- Copy stable/9 to releng/9.2 as part of the 9.2-RELEASE cycle.

[FreeBSD/releng/9.2.git] / lib / libc / stdlib / malloc.c

/*-
 * Copyright (C) 2006-2010 Jason Evans <jasone@FreeBSD.org>.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice(s), this list of conditions and the following disclaimer as
 *    the first lines of this file unmodified other than the possible
 *    addition of one or more copyright notices.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice(s), this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *******************************************************************************
 *
 * This allocator implementation is designed to provide scalable performance
 * for multi-threaded programs on multi-processor systems.  The following
 * features are included for this purpose:
 *
 *   + Multiple arenas are used if there are multiple CPUs, which reduces lock
 *     contention and cache sloshing.
 *
 *   + Thread-specific caching is used if there are multiple threads, which
 *     reduces the amount of locking.
 *
 *   + Cache line sharing between arenas is avoided for internal data
 *     structures.
 *
 *   + Memory is managed in chunks and runs (chunks can be split into runs),
 *     rather than as individual pages.  This provides a constant-time
 *     mechanism for associating allocations with particular arenas.
 *
 * Allocation requests are rounded up to the nearest size class, and no record
 * of the original request size is maintained.  Allocations are broken into
 * categories according to size class.  Assuming runtime defaults, 4 KiB pages
 * and a 16 byte quantum on a 32-bit system, the size classes in each category
 * are as follows:
 *
 *   |========================================|
 *   | Category | Subcategory      |     Size |
 *   |========================================|
 *   | Small    | Tiny             |        2 |
 *   |          |                  |        4 |
 *   |          |                  |        8 |
 *   |          |------------------+----------|
 *   |          | Quantum-spaced   |       16 |
 *   |          |                  |       32 |
 *   |          |                  |       48 |
 *   |          |                  |      ... |
 *   |          |                  |       96 |
 *   |          |                  |      112 |
 *   |          |                  |      128 |
 *   |          |------------------+----------|
 *   |          | Cacheline-spaced |      192 |
 *   |          |                  |      256 |
 *   |          |                  |      320 |
 *   |          |                  |      384 |
 *   |          |                  |      448 |
 *   |          |                  |      512 |
 *   |          |------------------+----------|
 *   |          | Sub-page         |      760 |
 *   |          |                  |     1024 |
 *   |          |                  |     1280 |
 *   |          |                  |      ... |
 *   |          |                  |     3328 |
 *   |          |                  |     3584 |
 *   |          |                  |     3840 |
 *   |========================================|
 *   | Medium                      |    4 KiB |
 *   |                             |    6 KiB |
 *   |                             |    8 KiB |
 *   |                             |      ... |
 *   |                             |   28 KiB |
 *   |                             |   30 KiB |
 *   |                             |   32 KiB |
 *   |========================================|
 *   | Large                       |   36 KiB |
 *   |                             |   40 KiB |
 *   |                             |   44 KiB |
 *   |                             |      ... |
 *   |                             | 1012 KiB |
 *   |                             | 1016 KiB |
 *   |                             | 1020 KiB |
 *   |========================================|
 *   | Huge                        |    1 MiB |
 *   |                             |    2 MiB |
 *   |                             |    3 MiB |
 *   |                             |      ... |
 *   |========================================|
 *
 * Different mechanisms are used accoding to category:
 *
 *   Small/medium : Each size class is segregated into its own set of runs.
 *                  Each run maintains a bitmap of which regions are
 *                  free/allocated.
 *
 *   Large : Each allocation is backed by a dedicated run.  Metadata are stored
 *           in the associated arena chunk header maps.
 *
 *   Huge : Each allocation is backed by a dedicated contiguous set of chunks.
 *          Metadata are stored in a separate red-black tree.
 *
 *******************************************************************************
 */

/*
 * MALLOC_PRODUCTION disables assertions and statistics gathering.  It also
 * defaults the A and J runtime options to off.  These settings are appropriate
 * for production systems.
 */
#ifndef MALLOC_PRODUCTION
#define MALLOC_PRODUCTION
#endif

#ifndef MALLOC_PRODUCTION
   /*
    * MALLOC_DEBUG enables assertions and other sanity checks, and disables
    * inline functions.
    */
#  define MALLOC_DEBUG

   /* MALLOC_STATS enables statistics calculation. */
#  define MALLOC_STATS
#endif

/*
 * MALLOC_TINY enables support for tiny objects, which are smaller than one
 * quantum.
 */
#define MALLOC_TINY

/*
 * MALLOC_TCACHE enables a thread-specific caching layer for small and medium
 * objects.  This makes it possible to allocate/deallocate objects without any
 * locking when the cache is in the steady state.
 */
#define MALLOC_TCACHE

/*
 * MALLOC_DSS enables use of sbrk(2) to allocate chunks from the data storage
 * segment (DSS).  In an ideal world, this functionality would be completely
 * unnecessary, but we are burdened by history and the lack of resource limits
 * for anonymous mapped memory.
 */
#define MALLOC_DSS

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "libc_private.h"
#ifdef MALLOC_DEBUG
#  define _LOCK_DEBUG
#endif
#include "spinlock.h"
#include "namespace.h"
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/sysctl.h>
#include <sys/uio.h>
#include <sys/ktrace.h> /* Must come after several other sys/ includes. */

#include <machine/cpufunc.h>
#include <machine/param.h>
#include <machine/vmparam.h>

#include <errno.h>
#include <limits.h>
#include <link.h>
#include <pthread.h>
#include <sched.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdint.h>
#include <inttypes.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>

#include "un-namespace.h"

#include "libc_private.h"

#define RB_COMPACT
#include "rb.h"
#if (defined(MALLOC_TCACHE) && defined(MALLOC_STATS))
#include "qr.h"
#include "ql.h"
#endif

#ifdef MALLOC_DEBUG
   /* Disable inlining to make debugging easier. */
#  define inline
#endif

/* Size of stack-allocated buffer passed to strerror_r(). */
#define STRERROR_BUF            64

/*
 * Minimum alignment of allocations is 2^LG_QUANTUM bytes.
 */
#ifdef __i386__
#  define LG_QUANTUM            4
#  define LG_SIZEOF_PTR         2
#  define CPU_SPINWAIT          __asm__ volatile("pause")
#  ifdef __clang__
#    define TLS_MODEL           /* clang does not support tls_model yet */
#  else
#    define TLS_MODEL           __attribute__((tls_model("initial-exec")))
#  endif
#endif
#ifdef __ia64__
#  define LG_QUANTUM            4
#  define LG_SIZEOF_PTR         3
#  define TLS_MODEL             /* default */
#endif
#ifdef __alpha__
#  define LG_QUANTUM            4
#  define LG_SIZEOF_PTR         3
#  define NO_TLS
#endif
#ifdef __sparc64__
#  define LG_QUANTUM            4
#  define LG_SIZEOF_PTR         3
#  define TLS_MODEL             __attribute__((tls_model("initial-exec")))
#endif
#ifdef __amd64__
#  define LG_QUANTUM            4
#  define LG_SIZEOF_PTR         3
#  define CPU_SPINWAIT          __asm__ volatile("pause")
#  ifdef __clang__
#    define TLS_MODEL           /* clang does not support tls_model yet */
#  else
#    define TLS_MODEL           __attribute__((tls_model("initial-exec")))
#  endif
#endif
#ifdef __arm__
#  define LG_QUANTUM            3
#  define LG_SIZEOF_PTR         2
#  define NO_TLS
#endif
#ifdef __mips__
#  define LG_QUANTUM            3
#  define LG_SIZEOF_PTR         2
#  define NO_TLS
#endif
#ifdef __powerpc64__
#  define LG_QUANTUM            4
#  define LG_SIZEOF_PTR         3
#  define TLS_MODEL             /* default */
#elif defined(__powerpc__)
#  define LG_QUANTUM            4
#  define LG_SIZEOF_PTR         2
#  define TLS_MODEL             /* default */
#endif
#ifdef __s390x__
#  define LG_QUANTUM            4
#endif

#define QUANTUM                 ((size_t)(1U << LG_QUANTUM))
#define QUANTUM_MASK            (QUANTUM - 1)

#define SIZEOF_PTR              (1U << LG_SIZEOF_PTR)

/* sizeof(int) == (1U << LG_SIZEOF_INT). */
#ifndef LG_SIZEOF_INT
#  define LG_SIZEOF_INT 2
#endif

/* We can't use TLS in non-PIC programs, since TLS relies on loader magic. */
#if (!defined(PIC) && !defined(NO_TLS))
#  define NO_TLS
#endif

#ifdef NO_TLS
   /* MALLOC_TCACHE requires TLS. */
#  ifdef MALLOC_TCACHE
#    undef MALLOC_TCACHE
#  endif
#endif

/*
 * Size and alignment of memory chunks that are allocated by the OS's virtual
 * memory system.
 */
#define LG_CHUNK_DEFAULT        22

/*
 * The minimum ratio of active:dirty pages per arena is computed as:
 *
 *   (nactive >> opt_lg_dirty_mult) >= ndirty
 *
 * So, supposing that opt_lg_dirty_mult is 5, there can be no less than 32
 * times as many active pages as dirty pages.
 */
#define LG_DIRTY_MULT_DEFAULT   5

/*
 * Maximum size of L1 cache line.  This is used to avoid cache line aliasing.
 * In addition, this controls the spacing of cacheline-spaced size classes.
 */
#define LG_CACHELINE            6
#define CACHELINE               ((size_t)(1U << LG_CACHELINE))
#define CACHELINE_MASK          (CACHELINE - 1)

/*
 * Subpages are an artificially designated partitioning of pages.  Their only
 * purpose is to support subpage-spaced size classes.
 *
 * There must be at least 4 subpages per page, due to the way size classes are
 * handled.
 */
#define LG_SUBPAGE              8
#define SUBPAGE                 ((size_t)(1U << LG_SUBPAGE))
#define SUBPAGE_MASK            (SUBPAGE - 1)

#ifdef MALLOC_TINY
   /* Smallest size class to support. */
#  define LG_TINY_MIN           1
#endif

/*
 * Maximum size class that is a multiple of the quantum, but not (necessarily)
 * a power of 2.  Above this size, allocations are rounded up to the nearest
 * power of 2.
 */
#define LG_QSPACE_MAX_DEFAULT   7

/*
 * Maximum size class that is a multiple of the cacheline, but not (necessarily)
 * a power of 2.  Above this size, allocations are rounded up to the nearest
 * power of 2.
 */
#define LG_CSPACE_MAX_DEFAULT   9

/*
 * Maximum medium size class.  This must not be more than 1/4 of a chunk
 * (LG_MEDIUM_MAX_DEFAULT <= LG_CHUNK_DEFAULT - 2).
 */
#define LG_MEDIUM_MAX_DEFAULT   15

/*
 * RUN_MAX_OVRHD indicates maximum desired run header overhead.  Runs are sized
 * as small as possible such that this setting is still honored, without
 * violating other constraints.  The goal is to make runs as small as possible
 * without exceeding a per run external fragmentation threshold.
 *
 * We use binary fixed point math for overhead computations, where the binary
 * point is implicitly RUN_BFP bits to the left.
 *
 * Note that it is possible to set RUN_MAX_OVRHD low enough that it cannot be
 * honored for some/all object sizes, since there is one bit of header overhead
 * per object (plus a constant).  This constraint is relaxed (ignored) for runs
 * that are so small that the per-region overhead is greater than:
 *
 *   (RUN_MAX_OVRHD / (reg_size << (3+RUN_BFP))
 */
#define RUN_BFP                 12
/*                                    \/   Implicit binary fixed point. */
#define RUN_MAX_OVRHD           0x0000003dU
#define RUN_MAX_OVRHD_RELAX     0x00001800U

/* Put a cap on small object run size.  This overrides RUN_MAX_OVRHD. */
#define RUN_MAX_SMALL                                                   \
        (arena_maxclass <= (1U << (CHUNK_MAP_LG_PG_RANGE + PAGE_SHIFT)) \
            ? arena_maxclass : (1U << (CHUNK_MAP_LG_PG_RANGE +          \
            PAGE_SHIFT)))

/*
 * Hyper-threaded CPUs may need a special instruction inside spin loops in
 * order to yield to another virtual CPU.  If no such instruction is defined
 * above, make CPU_SPINWAIT a no-op.
 */
#ifndef CPU_SPINWAIT
#  define CPU_SPINWAIT
#endif

/*
 * Adaptive spinning must eventually switch to blocking, in order to avoid the
 * potential for priority inversion deadlock.  Backing off past a certain point
 * can actually waste time.
 */
#define LG_SPIN_LIMIT           11

#ifdef MALLOC_TCACHE
   /*
    * Default number of cache slots for each bin in the thread cache (0:
    * disabled).
    */
#  define LG_TCACHE_NSLOTS_DEFAULT      7
   /*
    * (1U << opt_lg_tcache_gc_sweep) is the approximate number of
    * allocation events between full GC sweeps (-1: disabled).  Integer
    * rounding may cause the actual number to be slightly higher, since GC is
    * performed incrementally.
    */
#  define LG_TCACHE_GC_SWEEP_DEFAULT    13
#endif

/******************************************************************************/

/*
 * Mutexes based on spinlocks.  We can't use normal pthread spinlocks in all
 * places, because they require malloc()ed memory, which causes bootstrapping
 * issues in some cases.
 */
typedef struct {
        spinlock_t      lock;
} malloc_mutex_t;

/* Set to true once the allocator has been initialized. */
static bool malloc_initialized = false;

/* Used to avoid initialization races. */
static malloc_mutex_t init_lock = {_SPINLOCK_INITIALIZER};

/******************************************************************************/
/*
 * Statistics data structures.
 */

#ifdef MALLOC_STATS

#ifdef MALLOC_TCACHE
typedef struct tcache_bin_stats_s tcache_bin_stats_t;
struct tcache_bin_stats_s {
        /*
         * Number of allocation requests that corresponded to the size of this
         * bin.
         */
        uint64_t        nrequests;
};
#endif

typedef struct malloc_bin_stats_s malloc_bin_stats_t;
struct malloc_bin_stats_s {
        /*
         * Number of allocation requests that corresponded to the size of this
         * bin.
         */
        uint64_t        nrequests;

#ifdef MALLOC_TCACHE
        /* Number of tcache fills from this bin. */
        uint64_t        nfills;

        /* Number of tcache flushes to this bin. */
        uint64_t        nflushes;
#endif

        /* Total number of runs created for this bin's size class. */
        uint64_t        nruns;

        /*
         * Total number of runs reused by extracting them from the runs tree for
         * this bin's size class.
         */
        uint64_t        reruns;

        /* High-water mark for this bin. */
        size_t          highruns;

        /* Current number of runs in this bin. */
        size_t          curruns;
};

typedef struct malloc_large_stats_s malloc_large_stats_t;
struct malloc_large_stats_s {
        /*
         * Number of allocation requests that corresponded to this size class.
         */
        uint64_t        nrequests;

        /* High-water mark for this size class. */
        size_t          highruns;

        /* Current number of runs of this size class. */
        size_t          curruns;
};

typedef struct arena_stats_s arena_stats_t;
struct arena_stats_s {
        /* Number of bytes currently mapped. */
        size_t          mapped;

        /*
         * Total number of purge sweeps, total number of madvise calls made,
         * and total pages purged in order to keep dirty unused memory under
         * control.
         */
        uint64_t        npurge;
        uint64_t        nmadvise;
        uint64_t        purged;

        /* Per-size-category statistics. */
        size_t          allocated_small;
        uint64_t        nmalloc_small;
        uint64_t        ndalloc_small;

        size_t          allocated_medium;
        uint64_t        nmalloc_medium;
        uint64_t        ndalloc_medium;

        size_t          allocated_large;
        uint64_t        nmalloc_large;
        uint64_t        ndalloc_large;

        /*
         * One element for each possible size class, including sizes that
         * overlap with bin size classes.  This is necessary because ipalloc()
         * sometimes has to use such large objects in order to assure proper
         * alignment.
         */
        malloc_large_stats_t    *lstats;
};

typedef struct chunk_stats_s chunk_stats_t;
struct chunk_stats_s {
        /* Number of chunks that were allocated. */
        uint64_t        nchunks;

        /* High-water mark for number of chunks allocated. */
        size_t          highchunks;

        /*
         * Current number of chunks allocated.  This value isn't maintained for
         * any other purpose, so keep track of it in order to be able to set
         * highchunks.
         */
        size_t          curchunks;
};

#endif /* #ifdef MALLOC_STATS */

/******************************************************************************/
/*
 * Extent data structures.
 */

/* Tree of extents. */
typedef struct extent_node_s extent_node_t;
struct extent_node_s {
#ifdef MALLOC_DSS
        /* Linkage for the size/address-ordered tree. */
        rb_node(extent_node_t) link_szad;
#endif

        /* Linkage for the address-ordered tree. */
        rb_node(extent_node_t) link_ad;

        /* Pointer to the extent that this tree node is responsible for. */
        void    *addr;

        /* Total region size. */
        size_t  size;
};
typedef rb_tree(extent_node_t) extent_tree_t;

/******************************************************************************/
/*
 * Arena data structures.
 */

typedef struct arena_s arena_t;
typedef struct arena_bin_s arena_bin_t;

/* Each element of the chunk map corresponds to one page within the chunk. */
typedef struct arena_chunk_map_s arena_chunk_map_t;
struct arena_chunk_map_s {
        /*
         * Linkage for run trees.  There are two disjoint uses:
         *
         * 1) arena_t's runs_avail tree.
         * 2) arena_run_t conceptually uses this linkage for in-use non-full
         *    runs, rather than directly embedding linkage.
         */
        rb_node(arena_chunk_map_t)      link;

        /*
         * Run address (or size) and various flags are stored together.  The bit
         * layout looks like (assuming 32-bit system):
         *
         *   ???????? ???????? ????cccc ccccdzla
         *
         * ? : Unallocated: Run address for first/last pages, unset for internal
         *                  pages.
         *     Small/medium: Don't care.
         *     Large: Run size for first page, unset for trailing pages.
         * - : Unused.
         * c : refcount (could overflow for PAGE_SIZE >= 128 KiB)
         * d : dirty?
         * z : zeroed?
         * l : large?
         * a : allocated?
         *
         * Following are example bit patterns for the three types of runs.
         *
         * p : run page offset
         * s : run size
         * x : don't care
         * - : 0
         * [dzla] : bit set
         *
         *   Unallocated:
         *     ssssssss ssssssss ssss---- --------
         *     xxxxxxxx xxxxxxxx xxxx---- ----d---
         *     ssssssss ssssssss ssss---- -----z--
         *
         *   Small/medium:
         *     pppppppp ppppcccc cccccccc cccc---a
         *     pppppppp ppppcccc cccccccc cccc---a
         *     pppppppp ppppcccc cccccccc cccc---a
         *
         *   Large:
         *     ssssssss ssssssss ssss---- ------la
         *     -------- -------- -------- ------la
         *     -------- -------- -------- ------la
         */
        size_t                          bits;
#define CHUNK_MAP_PG_MASK       ((size_t)0xfff00000U)
#define CHUNK_MAP_PG_SHIFT      20
#define CHUNK_MAP_LG_PG_RANGE   12

#define CHUNK_MAP_RC_MASK       ((size_t)0xffff0U)
#define CHUNK_MAP_RC_ONE        ((size_t)0x00010U)

#define CHUNK_MAP_FLAGS_MASK    ((size_t)0xfU)
#define CHUNK_MAP_DIRTY         ((size_t)0x8U)
#define CHUNK_MAP_ZEROED        ((size_t)0x4U)
#define CHUNK_MAP_LARGE         ((size_t)0x2U)
#define CHUNK_MAP_ALLOCATED     ((size_t)0x1U)
#define CHUNK_MAP_KEY           (CHUNK_MAP_DIRTY | CHUNK_MAP_ALLOCATED)
};
typedef rb_tree(arena_chunk_map_t) arena_avail_tree_t;
typedef rb_tree(arena_chunk_map_t) arena_run_tree_t;

/* Arena chunk header. */
typedef struct arena_chunk_s arena_chunk_t;
struct arena_chunk_s {
        /* Arena that owns the chunk. */
        arena_t         *arena;

        /* Linkage for the arena's chunks_dirty tree. */
        rb_node(arena_chunk_t) link_dirty;

        /*
         * True if the chunk is currently in the chunks_dirty tree, due to
         * having at some point contained one or more dirty pages.  Removal
         * from chunks_dirty is lazy, so (dirtied && ndirty == 0) is possible.
         */
        bool            dirtied;

        /* Number of dirty pages. */
        size_t          ndirty;

        /* Map of pages within chunk that keeps track of free/large/small. */
        arena_chunk_map_t map[1]; /* Dynamically sized. */
};
typedef rb_tree(arena_chunk_t) arena_chunk_tree_t;

typedef struct arena_run_s arena_run_t;
struct arena_run_s {
#ifdef MALLOC_DEBUG
        uint32_t        magic;
#  define ARENA_RUN_MAGIC 0x384adf93
#endif

        /* Bin this run is associated with. */
        arena_bin_t     *bin;

        /* Index of first element that might have a free region. */
        unsigned        regs_minelm;

        /* Number of free regions in run. */
        unsigned        nfree;

        /* Bitmask of in-use regions (0: in use, 1: free). */
        unsigned        regs_mask[1]; /* Dynamically sized. */
};

struct arena_bin_s {
        /*
         * Current run being used to service allocations of this bin's size
         * class.
         */
        arena_run_t     *runcur;

        /*
         * Tree of non-full runs.  This tree is used when looking for an
         * existing run when runcur is no longer usable.  We choose the
         * non-full run that is lowest in memory; this policy tends to keep
         * objects packed well, and it can also help reduce the number of
         * almost-empty chunks.
         */
        arena_run_tree_t runs;

        /* Size of regions in a run for this bin's size class. */
        size_t          reg_size;

        /* Total size of a run for this bin's size class. */
        size_t          run_size;

        /* Total number of regions in a run for this bin's size class. */
        uint32_t        nregs;

        /* Number of elements in a run's regs_mask for this bin's size class. */
        uint32_t        regs_mask_nelms;

        /* Offset of first region in a run for this bin's size class. */
        uint32_t        reg0_offset;

#ifdef MALLOC_STATS
        /* Bin statistics. */
        malloc_bin_stats_t stats;
#endif
};

#ifdef MALLOC_TCACHE
typedef struct tcache_s tcache_t;
#endif

struct arena_s {
#ifdef MALLOC_DEBUG
        uint32_t                magic;
#  define ARENA_MAGIC 0x947d3d24
#endif

        /* All operations on this arena require that lock be locked. */
        pthread_mutex_t         lock;

#ifdef MALLOC_STATS
        arena_stats_t           stats;
#  ifdef MALLOC_TCACHE
        /*
         * List of tcaches for extant threads associated with this arena.
         * Stats from these are merged incrementally, and at exit.
         */
        ql_head(tcache_t)       tcache_ql;
#  endif
#endif

        /* Tree of dirty-page-containing chunks this arena manages. */
        arena_chunk_tree_t      chunks_dirty;

        /*
         * In order to avoid rapid chunk allocation/deallocation when an arena
         * oscillates right on the cusp of needing a new chunk, cache the most
         * recently freed chunk.  The spare is left in the arena's chunk trees
         * until it is deleted.
         *
         * There is one spare chunk per arena, rather than one spare total, in
         * order to avoid interactions between multiple threads that could make
         * a single spare inadequate.
         */
        arena_chunk_t           *spare;

        /* Number of pages in active runs. */
        size_t                  nactive;

        /*
         * Current count of pages within unused runs that are potentially
         * dirty, and for which madvise(... MADV_FREE) has not been called.  By
         * tracking this, we can institute a limit on how much dirty unused
         * memory is mapped for each arena.
         */
        size_t                  ndirty;

        /*
         * Size/address-ordered tree of this arena's available runs.  This tree
         * is used for first-best-fit run allocation.
         */
        arena_avail_tree_t      runs_avail;

        /*
         * bins is used to store trees of free regions of the following sizes,
         * assuming a 16-byte quantum, 4 KiB page size, and default
         * MALLOC_OPTIONS.
         *
         *   bins[i] |   size |
         *   --------+--------+
         *        0  |      2 |
         *        1  |      4 |
         *        2  |      8 |
         *   --------+--------+
         *        3  |     16 |
         *        4  |     32 |
         *        5  |     48 |
         *           :        :
         *        8  |     96 |
         *        9  |    112 |
         *       10  |    128 |
         *   --------+--------+
         *       11  |    192 |
         *       12  |    256 |
         *       13  |    320 |
         *       14  |    384 |
         *       15  |    448 |
         *       16  |    512 |
         *   --------+--------+
         *       17  |    768 |
         *       18  |   1024 |
         *       19  |   1280 |
         *           :        :
         *       27  |   3328 |
         *       28  |   3584 |
         *       29  |   3840 |
         *   --------+--------+
         *       30  |  4 KiB |
         *       31  |  6 KiB |
         *       33  |  8 KiB |
         *           :        :
         *       43  | 28 KiB |
         *       44  | 30 KiB |
         *       45  | 32 KiB |
         *   --------+--------+
         */
        arena_bin_t             bins[1]; /* Dynamically sized. */
};

/******************************************************************************/
/*
 * Thread cache data structures.
 */

#ifdef MALLOC_TCACHE
typedef struct tcache_bin_s tcache_bin_t;
struct tcache_bin_s {
#  ifdef MALLOC_STATS
        tcache_bin_stats_t tstats;
#  endif
        unsigned        low_water;      /* Min # cached since last GC. */
        unsigned        high_water;     /* Max # cached since last GC. */
        unsigned        ncached;        /* # of cached objects. */
        void            *slots[1];      /* Dynamically sized. */
};

struct tcache_s {
#  ifdef MALLOC_STATS
        ql_elm(tcache_t) link;          /* Used for aggregating stats. */
#  endif
        arena_t         *arena;         /* This thread's arena. */
        unsigned        ev_cnt;         /* Event count since incremental GC. */
        unsigned        next_gc_bin;    /* Next bin to GC. */
        tcache_bin_t    *tbins[1];      /* Dynamically sized. */
};
#endif

/******************************************************************************/
/*
 * Data.
 */

/* Number of CPUs. */
static unsigned         ncpus;

/* Various bin-related settings. */
#ifdef MALLOC_TINY              /* Number of (2^n)-spaced tiny bins. */
#  define               ntbins  ((unsigned)(LG_QUANTUM - LG_TINY_MIN))
#else
#  define               ntbins  0
#endif
static unsigned         nqbins; /* Number of quantum-spaced bins. */
static unsigned         ncbins; /* Number of cacheline-spaced bins. */
static unsigned         nsbins; /* Number of subpage-spaced bins. */
static unsigned         nmbins; /* Number of medium bins. */
static unsigned         nbins;
static unsigned         mbin0; /* mbin offset (nbins - nmbins). */
#ifdef MALLOC_TINY
#  define               tspace_max      ((size_t)(QUANTUM >> 1))
#endif
#define                 qspace_min      QUANTUM
static size_t           qspace_max;
static size_t           cspace_min;
static size_t           cspace_max;
static size_t           sspace_min;
static size_t           sspace_max;
#define                 small_maxclass  sspace_max
#define                 medium_min      PAGE_SIZE
static size_t           medium_max;
#define                 bin_maxclass    medium_max

/*
 * Soft limit on the number of medium size classes.  Spacing between medium
 * size classes never exceeds pagesize, which can force more than NBINS_MAX
 * medium size classes.
 */
#define NMBINS_MAX      16
/* Spacing between medium size classes. */
static size_t           lg_mspace;
static size_t           mspace_mask;

static uint8_t const    *small_size2bin;
/*
 * const_small_size2bin is a static constant lookup table that in the common
 * case can be used as-is for small_size2bin.  For dynamically linked programs,
 * this avoids a page of memory overhead per process.
 */
#define S2B_1(i)        i,
#define S2B_2(i)        S2B_1(i) S2B_1(i)
#define S2B_4(i)        S2B_2(i) S2B_2(i)
#define S2B_8(i)        S2B_4(i) S2B_4(i)
#define S2B_16(i)       S2B_8(i) S2B_8(i)
#define S2B_32(i)       S2B_16(i) S2B_16(i)
#define S2B_64(i)       S2B_32(i) S2B_32(i)
#define S2B_128(i)      S2B_64(i) S2B_64(i)
#define S2B_256(i)      S2B_128(i) S2B_128(i)
static const uint8_t    const_small_size2bin[PAGE_SIZE - 255] = {
        S2B_1(0xffU)            /*    0 */
#if (LG_QUANTUM == 4)
/* 64-bit system ************************/
#  ifdef MALLOC_TINY
        S2B_2(0)                /*    2 */
        S2B_2(1)                /*    4 */
        S2B_4(2)                /*    8 */
        S2B_8(3)                /*   16 */
#    define S2B_QMIN 3
#  else
        S2B_16(0)               /*   16 */
#    define S2B_QMIN 0
#  endif
        S2B_16(S2B_QMIN + 1)    /*   32 */
        S2B_16(S2B_QMIN + 2)    /*   48 */
        S2B_16(S2B_QMIN + 3)    /*   64 */
        S2B_16(S2B_QMIN + 4)    /*   80 */
        S2B_16(S2B_QMIN + 5)    /*   96 */
        S2B_16(S2B_QMIN + 6)    /*  112 */
        S2B_16(S2B_QMIN + 7)    /*  128 */
#  define S2B_CMIN (S2B_QMIN + 8)
#else
/* 32-bit system ************************/
#  ifdef MALLOC_TINY
        S2B_2(0)                /*    2 */
        S2B_2(1)                /*    4 */
        S2B_4(2)                /*    8 */
#    define S2B_QMIN 2
#  else
        S2B_8(0)                /*    8 */
#    define S2B_QMIN 0
#  endif
        S2B_8(S2B_QMIN + 1)     /*   16 */
        S2B_8(S2B_QMIN + 2)     /*   24 */
        S2B_8(S2B_QMIN + 3)     /*   32 */
        S2B_8(S2B_QMIN + 4)     /*   40 */
        S2B_8(S2B_QMIN + 5)     /*   48 */
        S2B_8(S2B_QMIN + 6)     /*   56 */
        S2B_8(S2B_QMIN + 7)     /*   64 */
        S2B_8(S2B_QMIN + 8)     /*   72 */
        S2B_8(S2B_QMIN + 9)     /*   80 */
        S2B_8(S2B_QMIN + 10)    /*   88 */
        S2B_8(S2B_QMIN + 11)    /*   96 */
        S2B_8(S2B_QMIN + 12)    /*  104 */
        S2B_8(S2B_QMIN + 13)    /*  112 */
        S2B_8(S2B_QMIN + 14)    /*  120 */
        S2B_8(S2B_QMIN + 15)    /*  128 */
#  define S2B_CMIN (S2B_QMIN + 16)
#endif
/****************************************/
        S2B_64(S2B_CMIN + 0)    /*  192 */
        S2B_64(S2B_CMIN + 1)    /*  256 */
        S2B_64(S2B_CMIN + 2)    /*  320 */
        S2B_64(S2B_CMIN + 3)    /*  384 */
        S2B_64(S2B_CMIN + 4)    /*  448 */
        S2B_64(S2B_CMIN + 5)    /*  512 */
#  define S2B_SMIN (S2B_CMIN + 6)
        S2B_256(S2B_SMIN + 0)   /*  768 */
        S2B_256(S2B_SMIN + 1)   /* 1024 */
        S2B_256(S2B_SMIN + 2)   /* 1280 */
        S2B_256(S2B_SMIN + 3)   /* 1536 */
        S2B_256(S2B_SMIN + 4)   /* 1792 */
        S2B_256(S2B_SMIN + 5)   /* 2048 */
        S2B_256(S2B_SMIN + 6)   /* 2304 */
        S2B_256(S2B_SMIN + 7)   /* 2560 */
        S2B_256(S2B_SMIN + 8)   /* 2816 */
        S2B_256(S2B_SMIN + 9)   /* 3072 */
        S2B_256(S2B_SMIN + 10)  /* 3328 */
        S2B_256(S2B_SMIN + 11)  /* 3584 */
        S2B_256(S2B_SMIN + 12)  /* 3840 */
#if (PAGE_SHIFT == 13)
        S2B_256(S2B_SMIN + 13)  /* 4096 */
        S2B_256(S2B_SMIN + 14)  /* 4352 */
        S2B_256(S2B_SMIN + 15)  /* 4608 */
        S2B_256(S2B_SMIN + 16)  /* 4864 */
        S2B_256(S2B_SMIN + 17)  /* 5120 */
        S2B_256(S2B_SMIN + 18)  /* 5376 */
        S2B_256(S2B_SMIN + 19)  /* 5632 */
        S2B_256(S2B_SMIN + 20)  /* 5888 */
        S2B_256(S2B_SMIN + 21)  /* 6144 */
        S2B_256(S2B_SMIN + 22)  /* 6400 */
        S2B_256(S2B_SMIN + 23)  /* 6656 */
        S2B_256(S2B_SMIN + 24)  /* 6912 */
        S2B_256(S2B_SMIN + 25)  /* 7168 */
        S2B_256(S2B_SMIN + 26)  /* 7424 */
        S2B_256(S2B_SMIN + 27)  /* 7680 */
        S2B_256(S2B_SMIN + 28)  /* 7936 */
#endif
};
#undef S2B_1
#undef S2B_2
#undef S2B_4
#undef S2B_8
#undef S2B_16
#undef S2B_32
#undef S2B_64
#undef S2B_128
#undef S2B_256
#undef S2B_QMIN
#undef S2B_CMIN
#undef S2B_SMIN

/* Various chunk-related settings. */
static size_t           chunksize;
static size_t           chunksize_mask; /* (chunksize - 1). */
static size_t           chunk_npages;
static size_t           arena_chunk_header_npages;
static size_t           arena_maxclass; /* Max size class for arenas. */

/********/
/*
 * Chunks.
 */

/* Protects chunk-related data structures. */
static malloc_mutex_t   huge_mtx;

/* Tree of chunks that are stand-alone huge allocations. */
static extent_tree_t    huge;

#ifdef MALLOC_DSS
/*
 * Protects sbrk() calls.  This avoids malloc races among threads, though it
 * does not protect against races with threads that call sbrk() directly.
 */
static malloc_mutex_t   dss_mtx;
/* Base address of the DSS. */
static void             *dss_base;
/* Current end of the DSS, or ((void *)-1) if the DSS is exhausted. */
static void             *dss_prev;
/* Current upper limit on DSS addresses. */
static void             *dss_max;

/*
 * Trees of chunks that were previously allocated (trees differ only in node
 * ordering).  These are used when allocating chunks, in an attempt to re-use
 * address space.  Depending on function, different tree orderings are needed,
 * which is why there are two trees with the same contents.
 */
static extent_tree_t    dss_chunks_szad;
static extent_tree_t    dss_chunks_ad;
#endif

#ifdef MALLOC_STATS
/* Huge allocation statistics. */
static uint64_t         huge_nmalloc;
static uint64_t         huge_ndalloc;
static size_t           huge_allocated;
#endif

/****************************/
/*
 * base (internal allocation).
 */

/*
 * Current pages that are being used for internal memory allocations.  These
 * pages are carved up in cacheline-size quanta, so that there is no chance of
 * false cache line sharing.
 */
static void             *base_pages;
static void             *base_next_addr;
static void             *base_past_addr; /* Addr immediately past base_pages. */
static extent_node_t    *base_nodes;
static malloc_mutex_t   base_mtx;
#ifdef MALLOC_STATS
static size_t           base_mapped;
#endif

/********/
/*
 * Arenas.
 */

/*
 * Arenas that are used to service external requests.  Not all elements of the
 * arenas array are necessarily used; arenas are created lazily as needed.
 */
static arena_t          **arenas;
static unsigned         narenas;
#ifndef NO_TLS
static unsigned         next_arena;
#endif
static pthread_mutex_t  arenas_lock; /* Protects arenas initialization. */

#ifndef NO_TLS
/*
 * Map of _pthread_self() --> arenas[???], used for selecting an arena to use
 * for allocations.
 */
static __thread arena_t         *arenas_map TLS_MODEL;
#endif

#ifdef MALLOC_TCACHE
/* Map of thread-specific caches. */
static __thread tcache_t        *tcache_tls TLS_MODEL;

/*
 * Number of cache slots for each bin in the thread cache, or 0 if tcache is
 * disabled.
 */
size_t                          tcache_nslots;

/* Number of tcache allocation/deallocation events between incremental GCs. */
unsigned                        tcache_gc_incr;
#endif

/*
 * Used by chunk_alloc_mmap() to decide whether to attempt the fast path and
 * potentially avoid some system calls.  We can get away without TLS here,
 * since the state of mmap_unaligned only affects performance, rather than
 * correct function.
 */
#ifndef NO_TLS
static __thread bool    mmap_unaligned TLS_MODEL;
#else
static          bool    mmap_unaligned;
#endif

#ifdef MALLOC_STATS
static malloc_mutex_t   chunks_mtx;
/* Chunk statistics. */
static chunk_stats_t    stats_chunks;
#endif

/*******************************/
/*
 * Runtime configuration options.
 */
const char      *_malloc_options;

#ifndef MALLOC_PRODUCTION
static bool     opt_abort = true;
static bool     opt_junk = true;
#else
static bool     opt_abort = false;
static bool     opt_junk = false;
#endif
#ifdef MALLOC_TCACHE
static size_t   opt_lg_tcache_nslots = LG_TCACHE_NSLOTS_DEFAULT;
static ssize_t  opt_lg_tcache_gc_sweep = LG_TCACHE_GC_SWEEP_DEFAULT;
#endif
#ifdef MALLOC_DSS
static bool     opt_dss = true;
static bool     opt_mmap = true;
#endif
static ssize_t  opt_lg_dirty_mult = LG_DIRTY_MULT_DEFAULT;
static bool     opt_stats_print = false;
static size_t   opt_lg_qspace_max = LG_QSPACE_MAX_DEFAULT;
static size_t   opt_lg_cspace_max = LG_CSPACE_MAX_DEFAULT;
static size_t   opt_lg_medium_max = LG_MEDIUM_MAX_DEFAULT;
static size_t   opt_lg_chunk = LG_CHUNK_DEFAULT;
static bool     opt_utrace = false;
static bool     opt_sysv = false;
static bool     opt_xmalloc = false;
static bool     opt_zero = false;
static int      opt_narenas_lshift = 0;

typedef struct {
        void    *p;
        size_t  s;
        void    *r;
} malloc_utrace_t;

#define UTRACE(a, b, c)                                                 \
        if (opt_utrace) {                                               \
                malloc_utrace_t ut;                                     \
                ut.p = (a);                                             \
                ut.s = (b);                                             \
                ut.r = (c);                                             \
                utrace(&ut, sizeof(ut));                                \
        }

/******************************************************************************/
/*
 * Begin function prototypes for non-inline static functions.
 */

static void     malloc_mutex_init(malloc_mutex_t *mutex);
static bool     malloc_spin_init(pthread_mutex_t *lock);
#ifdef MALLOC_TINY
static size_t   pow2_ceil(size_t x);
#endif
static void     wrtmessage(const char *p1, const char *p2, const char *p3,
                const char *p4);
#ifdef MALLOC_STATS
static void     malloc_printf(const char *format, ...);
#endif
static char     *umax2s(uintmax_t x, unsigned base, char *s);
#ifdef MALLOC_DSS
static bool     base_pages_alloc_dss(size_t minsize);
#endif
static bool     base_pages_alloc_mmap(size_t minsize);
static bool     base_pages_alloc(size_t minsize);
static void     *base_alloc(size_t size);
static void     *base_calloc(size_t number, size_t size);
static extent_node_t *base_node_alloc(void);
static void     base_node_dealloc(extent_node_t *node);
static void     *pages_map(void *addr, size_t size);
static void     pages_unmap(void *addr, size_t size);
#ifdef MALLOC_DSS
static void     *chunk_alloc_dss(size_t size, bool *zero);
static void     *chunk_recycle_dss(size_t size, bool *zero);
#endif
static void     *chunk_alloc_mmap_slow(size_t size, bool unaligned);
static void     *chunk_alloc_mmap(size_t size);
static void     *chunk_alloc(size_t size, bool *zero);
#ifdef MALLOC_DSS
static extent_node_t *chunk_dealloc_dss_record(void *chunk, size_t size);
static bool     chunk_dealloc_dss(void *chunk, size_t size);
#endif
static void     chunk_dealloc_mmap(void *chunk, size_t size);
static void     chunk_dealloc(void *chunk, size_t size);
#ifndef NO_TLS
static arena_t  *choose_arena_hard(void);
#endif
static void     arena_run_split(arena_t *arena, arena_run_t *run, size_t size,
    bool large, bool zero);
static arena_chunk_t *arena_chunk_alloc(arena_t *arena);
static void     arena_chunk_dealloc(arena_t *arena, arena_chunk_t *chunk);
static arena_run_t *arena_run_alloc(arena_t *arena, size_t size, bool large,
    bool zero);
static void     arena_purge(arena_t *arena);
static void     arena_run_dalloc(arena_t *arena, arena_run_t *run, bool dirty);
static void     arena_run_trim_head(arena_t *arena, arena_chunk_t *chunk,
    arena_run_t *run, size_t oldsize, size_t newsize);
static void     arena_run_trim_tail(arena_t *arena, arena_chunk_t *chunk,
    arena_run_t *run, size_t oldsize, size_t newsize, bool dirty);
static arena_run_t *arena_bin_nonfull_run_get(arena_t *arena, arena_bin_t *bin);
static void     *arena_bin_malloc_hard(arena_t *arena, arena_bin_t *bin);
static size_t   arena_bin_run_size_calc(arena_bin_t *bin, size_t min_run_size);
#ifdef MALLOC_TCACHE
static void     tcache_bin_fill(tcache_t *tcache, tcache_bin_t *tbin,
    size_t binind);
static void     *tcache_alloc_hard(tcache_t *tcache, tcache_bin_t *tbin,
    size_t binind);
#endif
static void     *arena_malloc_medium(arena_t *arena, size_t size, bool zero);
static void     *arena_malloc_large(arena_t *arena, size_t size, bool zero);
static void     *arena_palloc(arena_t *arena, size_t alignment, size_t size,
    size_t alloc_size);
static bool     arena_is_large(const void *ptr);
static size_t   arena_salloc(const void *ptr);
static void
arena_dalloc_bin_run(arena_t *arena, arena_chunk_t *chunk, arena_run_t *run,
    arena_bin_t *bin);
#ifdef MALLOC_STATS
static void     arena_stats_print(arena_t *arena);
#endif
static void     stats_print_atexit(void);
#ifdef MALLOC_TCACHE
static void     tcache_bin_flush(tcache_bin_t *tbin, size_t binind,
    unsigned rem);
#endif
static void     arena_dalloc_large(arena_t *arena, arena_chunk_t *chunk,
    void *ptr);
#ifdef MALLOC_TCACHE
static void     arena_dalloc_hard(arena_t *arena, arena_chunk_t *chunk,
    void *ptr, arena_chunk_map_t *mapelm, tcache_t *tcache);
#endif
static void     arena_ralloc_large_shrink(arena_t *arena, arena_chunk_t *chunk,
    void *ptr, size_t size, size_t oldsize);
static bool     arena_ralloc_large_grow(arena_t *arena, arena_chunk_t *chunk,
    void *ptr, size_t size, size_t oldsize);
static bool     arena_ralloc_large(void *ptr, size_t size, size_t oldsize);
static void     *arena_ralloc(void *ptr, size_t size, size_t oldsize);
static bool     arena_new(arena_t *arena, unsigned ind);
static arena_t  *arenas_extend(unsigned ind);
#ifdef MALLOC_TCACHE
static tcache_bin_t     *tcache_bin_create(arena_t *arena);
static void     tcache_bin_destroy(tcache_t *tcache, tcache_bin_t *tbin,
    unsigned binind);
#  ifdef MALLOC_STATS
static void     tcache_stats_merge(tcache_t *tcache, arena_t *arena);
#  endif
static tcache_t *tcache_create(arena_t *arena);
static void     tcache_destroy(tcache_t *tcache);
#endif
static void     *huge_malloc(size_t size, bool zero);
static void     *huge_palloc(size_t alignment, size_t size);
static void     *huge_ralloc(void *ptr, size_t size, size_t oldsize);
static void     huge_dalloc(void *ptr);
static void     malloc_stats_print(void);
#ifdef MALLOC_DEBUG
static void     small_size2bin_validate(void);
#endif
static bool     small_size2bin_init(void);
static bool     small_size2bin_init_hard(void);
static unsigned malloc_ncpus(void);
static bool     malloc_init_hard(void);

/*
 * End function prototypes.
 */
/******************************************************************************/

static void
wrtmessage(const char *p1, const char *p2, const char *p3, const char *p4)
{

        if (_write(STDERR_FILENO, p1, strlen(p1)) < 0
            || _write(STDERR_FILENO, p2, strlen(p2)) < 0
            || _write(STDERR_FILENO, p3, strlen(p3)) < 0
            || _write(STDERR_FILENO, p4, strlen(p4)) < 0)
                return;
}

void    (*_malloc_message)(const char *p1, const char *p2, const char *p3,
            const char *p4) = wrtmessage;

/*
 * We don't want to depend on vsnprintf() for production builds, since that can
 * cause unnecessary bloat for static binaries.  umax2s() provides minimal
 * integer printing functionality, so that malloc_printf() use can be limited to
 * MALLOC_STATS code.
 */
#define UMAX2S_BUFSIZE  65
static char *
umax2s(uintmax_t x, unsigned base, char *s)
{
        unsigned i;

        i = UMAX2S_BUFSIZE - 1;
        s[i] = '\0';
        switch (base) {
        case 10:
                do {
                        i--;
                        s[i] = "0123456789"[x % 10];
                        x /= 10;
                } while (x > 0);
                break;
        case 16:
                do {
                        i--;
                        s[i] = "0123456789abcdef"[x & 0xf];
                        x >>= 4;
                } while (x > 0);
                break;
        default:
                do {
                        i--;
                        s[i] = "0123456789abcdefghijklmnopqrstuvwxyz"[x % base];
                        x /= base;
                } while (x > 0);
        }

        return (&s[i]);
}

/*
 * Define a custom assert() in order to reduce the chances of deadlock during
 * assertion failure.
 */
#ifdef MALLOC_DEBUG
#  define assert(e) do {                                                \
        if (!(e)) {                                                     \
                char line_buf[UMAX2S_BUFSIZE];                          \
                _malloc_message(_getprogname(), ": (malloc) ",          \
                    __FILE__, ":");                                     \
                _malloc_message(umax2s(__LINE__, 10, line_buf),         \
                    ": Failed assertion: ", "\"", #e);                  \
                _malloc_message("\"\n", "", "", "");                    \
                abort();                                                \
        }                                                               \
} while (0)
#else
#define assert(e)
#endif

#ifdef MALLOC_STATS
/*
 * Print to stderr in such a way as to (hopefully) avoid memory allocation.
 */
static void
malloc_printf(const char *format, ...)
{
        char buf[4096];
        va_list ap;

        va_start(ap, format);
        vsnprintf(buf, sizeof(buf), format, ap);
        va_end(ap);
        _malloc_message(buf, "", "", "");
}
#endif

/******************************************************************************/
/*
 * Begin mutex.  We can't use normal pthread mutexes in all places, because
 * they require malloc()ed memory, which causes bootstrapping issues in some
 * cases.
 */

static void
malloc_mutex_init(malloc_mutex_t *mutex)
{
        static const spinlock_t lock = _SPINLOCK_INITIALIZER;

        mutex->lock = lock;
}

static inline void
malloc_mutex_lock(malloc_mutex_t *mutex)
{

        if (__isthreaded)
                _SPINLOCK(&mutex->lock);
}

static inline void
malloc_mutex_unlock(malloc_mutex_t *mutex)
{

        if (__isthreaded)
                _SPINUNLOCK(&mutex->lock);
}

/*
 * End mutex.
 */
/******************************************************************************/
/*
 * Begin spin lock.  Spin locks here are actually adaptive mutexes that block
 * after a period of spinning, because unbounded spinning would allow for
 * priority inversion.
 */

/*
 * We use an unpublished interface to initialize pthread mutexes with an
 * allocation callback, in order to avoid infinite recursion.
 */
int     _pthread_mutex_init_calloc_cb(pthread_mutex_t *mutex,
    void *(calloc_cb)(size_t, size_t));

__weak_reference(_pthread_mutex_init_calloc_cb_stub,
    _pthread_mutex_init_calloc_cb);

int
_pthread_mutex_init_calloc_cb_stub(pthread_mutex_t *mutex,
    void *(calloc_cb)(size_t, size_t))
{

        return (0);
}

static bool
malloc_spin_init(pthread_mutex_t *lock)
{

        if (_pthread_mutex_init_calloc_cb(lock, base_calloc) != 0)
                return (true);

        return (false);
}

static inline void
malloc_spin_lock(pthread_mutex_t *lock)
{

        if (__isthreaded) {
                if (_pthread_mutex_trylock(lock) != 0) {
                        /* Exponentially back off if there are multiple CPUs. */
                        if (ncpus > 1) {
                                unsigned i;
                                volatile unsigned j;

                                for (i = 1; i <= LG_SPIN_LIMIT; i++) {
                                        for (j = 0; j < (1U << i); j++) {
                                                CPU_SPINWAIT;
                                        }

                                        if (_pthread_mutex_trylock(lock) == 0)
                                                return;
                                }
                        }

                        /*
                         * Spinning failed.  Block until the lock becomes
                         * available, in order to avoid indefinite priority
                         * inversion.
                         */
                        _pthread_mutex_lock(lock);
                }
        }
}

static inline void
malloc_spin_unlock(pthread_mutex_t *lock)
{

        if (__isthreaded)
                _pthread_mutex_unlock(lock);
}

/*
 * End spin lock.
 */
/******************************************************************************/
/*
 * Begin Utility functions/macros.
 */

/* Return the chunk address for allocation address a. */
#define CHUNK_ADDR2BASE(a)                                              \
        ((void *)((uintptr_t)(a) & ~chunksize_mask))

/* Return the chunk offset of address a. */
#define CHUNK_ADDR2OFFSET(a)                                            \
        ((size_t)((uintptr_t)(a) & chunksize_mask))

/* Return the smallest chunk multiple that is >= s. */
#define CHUNK_CEILING(s)                                                \
        (((s) + chunksize_mask) & ~chunksize_mask)

/* Return the smallest quantum multiple that is >= a. */
#define QUANTUM_CEILING(a)                                              \
        (((a) + QUANTUM_MASK) & ~QUANTUM_MASK)

/* Return the smallest cacheline multiple that is >= s. */
#define CACHELINE_CEILING(s)                                            \
        (((s) + CACHELINE_MASK) & ~CACHELINE_MASK)

/* Return the smallest subpage multiple that is >= s. */
#define SUBPAGE_CEILING(s)                                              \
        (((s) + SUBPAGE_MASK) & ~SUBPAGE_MASK)

/* Return the smallest medium size class that is >= s. */
#define MEDIUM_CEILING(s)                                               \
        (((s) + mspace_mask) & ~mspace_mask)

/* Return the smallest pagesize multiple that is >= s. */
#define PAGE_CEILING(s)                                                 \
        (((s) + PAGE_MASK) & ~PAGE_MASK)

#ifdef MALLOC_TINY
/* Compute the smallest power of 2 that is >= x. */
static size_t
pow2_ceil(size_t x)
{

        x--;
        x |= x >> 1;
        x |= x >> 2;
        x |= x >> 4;
        x |= x >> 8;
        x |= x >> 16;
#if (SIZEOF_PTR == 8)
        x |= x >> 32;
#endif
        x++;
        return (x);
}
#endif

/******************************************************************************/

#ifdef MALLOC_DSS
static bool
base_pages_alloc_dss(size_t minsize)
{

        /*
         * Do special DSS allocation here, since base allocations don't need to
         * be chunk-aligned.
         */
        malloc_mutex_lock(&dss_mtx);
        if (dss_prev != (void *)-1) {
                intptr_t incr;
                size_t csize = CHUNK_CEILING(minsize);

                do {
                        /* Get the current end of the DSS. */
                        dss_max = sbrk(0);

                        /*
                         * Calculate how much padding is necessary to
                         * chunk-align the end of the DSS.  Don't worry about
                         * dss_max not being chunk-aligned though.
                         */
                        incr = (intptr_t)chunksize
                            - (intptr_t)CHUNK_ADDR2OFFSET(dss_max);
                        assert(incr >= 0);
                        if ((size_t)incr < minsize)
                                incr += csize;

                        dss_prev = sbrk(incr);
                        if (dss_prev == dss_max) {
                                /* Success. */
                                dss_max = (void *)((intptr_t)dss_prev + incr);
                                base_pages = dss_prev;
                                base_next_addr = base_pages;
                                base_past_addr = dss_max;
#ifdef MALLOC_STATS
                                base_mapped += incr;
#endif
                                malloc_mutex_unlock(&dss_mtx);
                                return (false);
                        }
                } while (dss_prev != (void *)-1);
        }
        malloc_mutex_unlock(&dss_mtx);

        return (true);
}
#endif

static bool
base_pages_alloc_mmap(size_t minsize)
{
        size_t csize;

        assert(minsize != 0);
        csize = PAGE_CEILING(minsize);
        base_pages = pages_map(NULL, csize);
        if (base_pages == NULL)
                return (true);
        base_next_addr = base_pages;
        base_past_addr = (void *)((uintptr_t)base_pages + csize);
#ifdef MALLOC_STATS
        base_mapped += csize;
#endif

        return (false);
}

static bool
base_pages_alloc(size_t minsize)
{

#ifdef MALLOC_DSS
        if (opt_mmap && minsize != 0)
#endif
        {
                if (base_pages_alloc_mmap(minsize) == false)
                        return (false);
        }

#ifdef MALLOC_DSS
        if (opt_dss) {
                if (base_pages_alloc_dss(minsize) == false)
                        return (false);
        }

#endif

        return (true);
}

static void *
base_alloc(size_t size)
{
        void *ret;
        size_t csize;

        /* Round size up to nearest multiple of the cacheline size. */
        csize = CACHELINE_CEILING(size);

        malloc_mutex_lock(&base_mtx);
        /* Make sure there's enough space for the allocation. */
        if ((uintptr_t)base_next_addr + csize > (uintptr_t)base_past_addr) {
                if (base_pages_alloc(csize)) {
                        malloc_mutex_unlock(&base_mtx);
                        return (NULL);
                }
        }
        /* Allocate. */
        ret = base_next_addr;
        base_next_addr = (void *)((uintptr_t)base_next_addr + csize);
        malloc_mutex_unlock(&base_mtx);

        return (ret);
}

static void *
base_calloc(size_t number, size_t size)
{
        void *ret;

        ret = base_alloc(number * size);
        if (ret != NULL)
                memset(ret, 0, number * size);

        return (ret);
}

static extent_node_t *
base_node_alloc(void)
{
        extent_node_t *ret;

        malloc_mutex_lock(&base_mtx);
        if (base_nodes != NULL) {
                ret = base_nodes;
                base_nodes = *(extent_node_t **)ret;
                malloc_mutex_unlock(&base_mtx);
        } else {
                malloc_mutex_unlock(&base_mtx);
                ret = (extent_node_t *)base_alloc(sizeof(extent_node_t));
        }

        return (ret);
}

static void
base_node_dealloc(extent_node_t *node)
{

        malloc_mutex_lock(&base_mtx);
        *(extent_node_t **)node = base_nodes;
        base_nodes = node;
        malloc_mutex_unlock(&base_mtx);
}

/*
 * End Utility functions/macros.
 */
/******************************************************************************/
/*
 * Begin extent tree code.
 */

#ifdef MALLOC_DSS
static inline int
extent_szad_comp(extent_node_t *a, extent_node_t *b)
{
        int ret;
        size_t a_size = a->size;
        size_t b_size = b->size;

        ret = (a_size > b_size) - (a_size < b_size);
        if (ret == 0) {
                uintptr_t a_addr = (uintptr_t)a->addr;
                uintptr_t b_addr = (uintptr_t)b->addr;

                ret = (a_addr > b_addr) - (a_addr < b_addr);
        }

        return (ret);
}

/* Wrap red-black tree macros in functions. */
rb_gen(__unused static, extent_tree_szad_, extent_tree_t, extent_node_t,
    link_szad, extent_szad_comp)
#endif

static inline int
extent_ad_comp(extent_node_t *a, extent_node_t *b)
{
        uintptr_t a_addr = (uintptr_t)a->addr;
        uintptr_t b_addr = (uintptr_t)b->addr;

        return ((a_addr > b_addr) - (a_addr < b_addr));
}

/* Wrap red-black tree macros in functions. */
rb_gen(__unused static, extent_tree_ad_, extent_tree_t, extent_node_t, link_ad,
    extent_ad_comp)

/*
 * End extent tree code.
 */
/******************************************************************************/
/*
 * Begin chunk management functions.
 */

static void *
pages_map(void *addr, size_t size)
{
        void *ret;

        /*
         * We don't use MAP_FIXED here, because it can cause the *replacement*
         * of existing mappings, and we only want to create new mappings.
         */
        ret = mmap(addr, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON,
            -1, 0);
        assert(ret != NULL);

        if (ret == MAP_FAILED)
                ret = NULL;
        else if (addr != NULL && ret != addr) {
                /*
                 * We succeeded in mapping memory, but not in the right place.
                 */
                if (munmap(ret, size) == -1) {
                        char buf[STRERROR_BUF];

                        strerror_r(errno, buf, sizeof(buf));
                        _malloc_message(_getprogname(),
                            ": (malloc) Error in munmap(): ", buf, "\n");
                        if (opt_abort)
                                abort();
                }
                ret = NULL;
        }

        assert(ret == NULL || (addr == NULL && ret != addr)
            || (addr != NULL && ret == addr));
        return (ret);
}

static void
pages_unmap(void *addr, size_t size)
{

        if (munmap(addr, size) == -1) {
                char buf[STRERROR_BUF];

                strerror_r(errno, buf, sizeof(buf));
                _malloc_message(_getprogname(),
                    ": (malloc) Error in munmap(): ", buf, "\n");
                if (opt_abort)
                        abort();
        }
}

#ifdef MALLOC_DSS
static void *
chunk_alloc_dss(size_t size, bool *zero)
{
        void *ret;

        ret = chunk_recycle_dss(size, zero);
        if (ret != NULL)
                return (ret);

        /*
         * sbrk() uses a signed increment argument, so take care not to
         * interpret a huge allocation request as a negative increment.
         */
        if ((intptr_t)size < 0)
                return (NULL);

        malloc_mutex_lock(&dss_mtx);
        if (dss_prev != (void *)-1) {
                intptr_t incr;

                /*
                 * The loop is necessary to recover from races with other
                 * threads that are using the DSS for something other than
                 * malloc.
                 */
                do {
                        /* Get the current end of the DSS. */
                        dss_max = sbrk(0);

                        /*
                         * Calculate how much padding is necessary to
                         * chunk-align the end of the DSS.
                         */
                        incr = (intptr_t)size
                            - (intptr_t)CHUNK_ADDR2OFFSET(dss_max);
                        if (incr == (intptr_t)size)
                                ret = dss_max;
                        else {
                                ret = (void *)((intptr_t)dss_max + incr);
                                incr += size;
                        }

                        dss_prev = sbrk(incr);
                        if (dss_prev == dss_max) {
                                /* Success. */
                                dss_max = (void *)((intptr_t)dss_prev + incr);
                                malloc_mutex_unlock(&dss_mtx);
                                *zero = true;
                                return (ret);
                        }
                } while (dss_prev != (void *)-1);
        }
        malloc_mutex_unlock(&dss_mtx);

        return (NULL);
}

static void *
chunk_recycle_dss(size_t size, bool *zero)
{
        extent_node_t *node, key;

        key.addr = NULL;
        key.size = size;
        malloc_mutex_lock(&dss_mtx);
        node = extent_tree_szad_nsearch(&dss_chunks_szad, &key);
        if (node != NULL) {
                void *ret = node->addr;

                /* Remove node from the tree. */
                extent_tree_szad_remove(&dss_chunks_szad, node);
                if (node->size == size) {
                        extent_tree_ad_remove(&dss_chunks_ad, node);
                        base_node_dealloc(node);
                } else {
                        /*
                         * Insert the remainder of node's address range as a
                         * smaller chunk.  Its position within dss_chunks_ad
                         * does not change.
                         */
                        assert(node->size > size);
                        node->addr = (void *)((uintptr_t)node->addr + size);
                        node->size -= size;
                        extent_tree_szad_insert(&dss_chunks_szad, node);
                }
                malloc_mutex_unlock(&dss_mtx);

                if (*zero)
                        memset(ret, 0, size);
                return (ret);
        }
        malloc_mutex_unlock(&dss_mtx);

        return (NULL);
}
#endif

static void *
chunk_alloc_mmap_slow(size_t size, bool unaligned)
{
        void *ret;
        size_t offset;

        /* Beware size_t wrap-around. */
        if (size + chunksize <= size)
                return (NULL);

        ret = pages_map(NULL, size + chunksize);
        if (ret == NULL)
                return (NULL);

        /* Clean up unneeded leading/trailing space. */
        offset = CHUNK_ADDR2OFFSET(ret);
        if (offset != 0) {
                /* Note that mmap() returned an unaligned mapping. */
                unaligned = true;

                /* Leading space. */
                pages_unmap(ret, chunksize - offset);

                ret = (void *)((uintptr_t)ret +
                    (chunksize - offset));

                /* Trailing space. */
                pages_unmap((void *)((uintptr_t)ret + size),
                    offset);
        } else {
                /* Trailing space only. */
                pages_unmap((void *)((uintptr_t)ret + size),
                    chunksize);
        }

        /*
         * If mmap() returned an aligned mapping, reset mmap_unaligned so that
         * the next chunk_alloc_mmap() execution tries the fast allocation
         * method.
         */
        if (unaligned == false)
                mmap_unaligned = false;

        return (ret);
}

static void *
chunk_alloc_mmap(size_t size)
{
        void *ret;

        /*
         * Ideally, there would be a way to specify alignment to mmap() (like
         * NetBSD has), but in the absence of such a feature, we have to work
         * hard to efficiently create aligned mappings.  The reliable, but
         * slow method is to create a mapping that is over-sized, then trim the
         * excess.  However, that always results in at least one call to
         * pages_unmap().
         *
         * A more optimistic approach is to try mapping precisely the right
         * amount, then try to append another mapping if alignment is off.  In
         * practice, this works out well as long as the application is not
         * interleaving mappings via direct mmap() calls.  If we do run into a
         * situation where there is an interleaved mapping and we are unable to
         * extend an unaligned mapping, our best option is to switch to the
         * slow method until mmap() returns another aligned mapping.  This will
         * tend to leave a gap in the memory map that is too small to cause
         * later problems for the optimistic method.
         *
         * Another possible confounding factor is address space layout
         * randomization (ASLR), which causes mmap(2) to disregard the
         * requested address.  mmap_unaligned tracks whether the previous
         * chunk_alloc_mmap() execution received any unaligned or relocated
         * mappings, and if so, the current execution will immediately fall
         * back to the slow method.  However, we keep track of whether the fast
         * method would have succeeded, and if so, we make a note to try the
         * fast method next time.
         */

        if (mmap_unaligned == false) {
                size_t offset;

                ret = pages_map(NULL, size);
                if (ret == NULL)
                        return (NULL);

                offset = CHUNK_ADDR2OFFSET(ret);
                if (offset != 0) {
                        mmap_unaligned = true;
                        /* Try to extend chunk boundary. */
                        if (pages_map((void *)((uintptr_t)ret + size),
                            chunksize - offset) == NULL) {
                                /*
                                 * Extension failed.  Clean up, then revert to
                                 * the reliable-but-expensive method.
                                 */
                                pages_unmap(ret, size);
                                ret = chunk_alloc_mmap_slow(size, true);
                        } else {
                                /* Clean up unneeded leading space. */
                                pages_unmap(ret, chunksize - offset);
                                ret = (void *)((uintptr_t)ret + (chunksize -
                                    offset));
                        }
                }
        } else
                ret = chunk_alloc_mmap_slow(size, false);

        return (ret);
}

/*
 * If the caller specifies (*zero == false), it is still possible to receive
 * zeroed memory, in which case *zero is toggled to true.  arena_chunk_alloc()
 * takes advantage of this to avoid demanding zeroed chunks, but taking
 * advantage of them if they are returned.
 */
static void *
chunk_alloc(size_t size, bool *zero)
{
        void *ret;

        assert(size != 0);
        assert((size & chunksize_mask) == 0);

#ifdef MALLOC_DSS
        if (opt_mmap)
#endif
        {
                ret = chunk_alloc_mmap(size);
                if (ret != NULL) {
                        *zero = true;
                        goto RETURN;
                }
        }

#ifdef MALLOC_DSS
        if (opt_dss) {
                ret = chunk_alloc_dss(size, zero);
                if (ret != NULL)
                        goto RETURN;
        }
#endif

        /* All strategies for allocation failed. */
        ret = NULL;
RETURN:
#ifdef MALLOC_STATS
        if (ret != NULL) {
                malloc_mutex_lock(&chunks_mtx);
                stats_chunks.nchunks += (size / chunksize);
                stats_chunks.curchunks += (size / chunksize);
                if (stats_chunks.curchunks > stats_chunks.highchunks)
                        stats_chunks.highchunks = stats_chunks.curchunks;
                malloc_mutex_unlock(&chunks_mtx);
        }
#endif

        assert(CHUNK_ADDR2BASE(ret) == ret);
        return (ret);
}

#ifdef MALLOC_DSS
static extent_node_t *
chunk_dealloc_dss_record(void *chunk, size_t size)
{
        extent_node_t *node, *prev, key;

        key.addr = (void *)((uintptr_t)chunk + size);
        node = extent_tree_ad_nsearch(&dss_chunks_ad, &key);
        /* Try to coalesce forward. */
        if (node != NULL && node->addr == key.addr) {
                /*
                 * Coalesce chunk with the following address range.  This does
                 * not change the position within dss_chunks_ad, so only
                 * remove/insert from/into dss_chunks_szad.
                 */
                extent_tree_szad_remove(&dss_chunks_szad, node);
                node->addr = chunk;
                node->size += size;
                extent_tree_szad_insert(&dss_chunks_szad, node);
        } else {
                /*
                 * Coalescing forward failed, so insert a new node.  Drop
                 * dss_mtx during node allocation, since it is possible that a
                 * new base chunk will be allocated.
                 */
                malloc_mutex_unlock(&dss_mtx);
                node = base_node_alloc();
                malloc_mutex_lock(&dss_mtx);
                if (node == NULL)
                        return (NULL);
                node->addr = chunk;
                node->size = size;
                extent_tree_ad_insert(&dss_chunks_ad, node);
                extent_tree_szad_insert(&dss_chunks_szad, node);
        }

        /* Try to coalesce backward. */
        prev = extent_tree_ad_prev(&dss_chunks_ad, node);
        if (prev != NULL && (void *)((uintptr_t)prev->addr + prev->size) ==
            chunk) {
                /*
                 * Coalesce chunk with the previous address range.  This does
                 * not change the position within dss_chunks_ad, so only
                 * remove/insert node from/into dss_chunks_szad.
                 */
                extent_tree_szad_remove(&dss_chunks_szad, prev);
                extent_tree_ad_remove(&dss_chunks_ad, prev);

                extent_tree_szad_remove(&dss_chunks_szad, node);
                node->addr = prev->addr;
                node->size += prev->size;
                extent_tree_szad_insert(&dss_chunks_szad, node);

                base_node_dealloc(prev);
        }

        return (node);
}

static bool
chunk_dealloc_dss(void *chunk, size_t size)
{
        bool ret;

        malloc_mutex_lock(&dss_mtx);
        if ((uintptr_t)chunk >= (uintptr_t)dss_base
            && (uintptr_t)chunk < (uintptr_t)dss_max) {
                extent_node_t *node;

                /* Try to coalesce with other unused chunks. */
                node = chunk_dealloc_dss_record(chunk, size);
                if (node != NULL) {
                        chunk = node->addr;
                        size = node->size;
                }

                /* Get the current end of the DSS. */
                dss_max = sbrk(0);

                /*
                 * Try to shrink the DSS if this chunk is at the end of the
                 * DSS.  The sbrk() call here is subject to a race condition
                 * with threads that use brk(2) or sbrk(2) directly, but the
                 * alternative would be to leak memory for the sake of poorly
                 * designed multi-threaded programs.
                 */
                if ((void *)((uintptr_t)chunk + size) == dss_max
                    && (dss_prev = sbrk(-(intptr_t)size)) == dss_max) {
                        /* Success. */
                        dss_max = (void *)((intptr_t)dss_prev - (intptr_t)size);

                        if (node != NULL) {
                                extent_tree_szad_remove(&dss_chunks_szad, node);
                                extent_tree_ad_remove(&dss_chunks_ad, node);
                                base_node_dealloc(node);
                        }
                } else
                        madvise(chunk, size, MADV_FREE);

                ret = false;
                goto RETURN;
        }

        ret = true;
RETURN:
        malloc_mutex_unlock(&dss_mtx);
        return (ret);
}
#endif

static void
chunk_dealloc_mmap(void *chunk, size_t size)
{

        pages_unmap(chunk, size);
}

static void
chunk_dealloc(void *chunk, size_t size)
{

        assert(chunk != NULL);
        assert(CHUNK_ADDR2BASE(chunk) == chunk);
        assert(size != 0);
        assert((size & chunksize_mask) == 0);

#ifdef MALLOC_STATS
        malloc_mutex_lock(&chunks_mtx);
        stats_chunks.curchunks -= (size / chunksize);
        malloc_mutex_unlock(&chunks_mtx);
#endif

#ifdef MALLOC_DSS
        if (opt_dss) {
                if (chunk_dealloc_dss(chunk, size) == false)
                        return;
        }

        if (opt_mmap)
#endif
                chunk_dealloc_mmap(chunk, size);
}

/*
 * End chunk management functions.
 */
/******************************************************************************/
/*
 * Begin arena.
 */

/*
 * Choose an arena based on a per-thread value (fast-path code, calls slow-path
 * code if necessary).
 */
static inline arena_t *
choose_arena(void)
{
        arena_t *ret;

        /*
         * We can only use TLS if this is a PIC library, since for the static
         * library version, libc's malloc is used by TLS allocation, which
         * introduces a bootstrapping issue.
         */
#ifndef NO_TLS
        if (__isthreaded == false) {
            /* Avoid the overhead of TLS for single-threaded operation. */
            return (arenas[0]);
        }

        ret = arenas_map;
        if (ret == NULL) {
                ret = choose_arena_hard();
                assert(ret != NULL);
        }
#else
        if (__isthreaded && narenas > 1) {
                unsigned long ind;

                /*
                 * Hash _pthread_self() to one of the arenas.  There is a prime
                 * number of arenas, so this has a reasonable chance of
                 * working.  Even so, the hashing can be easily thwarted by
                 * inconvenient _pthread_self() values.  Without specific
                 * knowledge of how _pthread_self() calculates values, we can't
                 * easily do much better than this.
                 */
                ind = (unsigned long) _pthread_self() % narenas;

                /*
                 * Optimistially assume that arenas[ind] has been initialized.
                 * At worst, we find out that some other thread has already
                 * done so, after acquiring the lock in preparation.  Note that
                 * this lazy locking also has the effect of lazily forcing
                 * cache coherency; without the lock acquisition, there's no
                 * guarantee that modification of arenas[ind] by another thread
                 * would be seen on this CPU for an arbitrary amount of time.
                 *
                 * In general, this approach to modifying a synchronized value
                 * isn't a good idea, but in this case we only ever modify the
                 * value once, so things work out well.
                 */
                ret = arenas[ind];
                if (ret == NULL) {
                        /*
                         * Avoid races with another thread that may have already
                         * initialized arenas[ind].
                         */
                        malloc_spin_lock(&arenas_lock);
                        if (arenas[ind] == NULL)
                                ret = arenas_extend((unsigned)ind);
                        else
                                ret = arenas[ind];
                        malloc_spin_unlock(&arenas_lock);
                }
        } else
                ret = arenas[0];
#endif

        assert(ret != NULL);
        return (ret);
}

#ifndef NO_TLS
/*
 * Choose an arena based on a per-thread value (slow-path code only, called
 * only by choose_arena()).
 */
static arena_t *
choose_arena_hard(void)
{
        arena_t *ret;

        assert(__isthreaded);

        if (narenas > 1) {
                malloc_spin_lock(&arenas_lock);
                if ((ret = arenas[next_arena]) == NULL)
                        ret = arenas_extend(next_arena);
                next_arena = (next_arena + 1) % narenas;
                malloc_spin_unlock(&arenas_lock);
        } else
                ret = arenas[0];

        arenas_map = ret;

        return (ret);
}
#endif

static inline int
arena_chunk_comp(arena_chunk_t *a, arena_chunk_t *b)
{
        uintptr_t a_chunk = (uintptr_t)a;
        uintptr_t b_chunk = (uintptr_t)b;

        assert(a != NULL);
        assert(b != NULL);

        return ((a_chunk > b_chunk) - (a_chunk < b_chunk));
}

/* Wrap red-black tree macros in functions. */
rb_gen(__unused static, arena_chunk_tree_dirty_, arena_chunk_tree_t,
    arena_chunk_t, link_dirty, arena_chunk_comp)

static inline int
arena_run_comp(arena_chunk_map_t *a, arena_chunk_map_t *b)
{
        uintptr_t a_mapelm = (uintptr_t)a;
        uintptr_t b_mapelm = (uintptr_t)b;

        assert(a != NULL);
        assert(b != NULL);

        return ((a_mapelm > b_mapelm) - (a_mapelm < b_mapelm));
}

/* Wrap red-black tree macros in functions. */
rb_gen(__unused static, arena_run_tree_, arena_run_tree_t, arena_chunk_map_t,
    link, arena_run_comp)

static inline int
arena_avail_comp(arena_chunk_map_t *a, arena_chunk_map_t *b)
{
        int ret;
        size_t a_size = a->bits & ~PAGE_MASK;
        size_t b_size = b->bits & ~PAGE_MASK;

        ret = (a_size > b_size) - (a_size < b_size);
        if (ret == 0) {
                uintptr_t a_mapelm, b_mapelm;

                if ((a->bits & CHUNK_MAP_KEY) != CHUNK_MAP_KEY)
                        a_mapelm = (uintptr_t)a;
                else {
                        /*
                         * Treat keys as though they are lower than anything
                         * else.
                         */
                        a_mapelm = 0;
                }
                b_mapelm = (uintptr_t)b;

                ret = (a_mapelm > b_mapelm) - (a_mapelm < b_mapelm);
        }

        return (ret);
}

/* Wrap red-black tree macros in functions. */
rb_gen(__unused static, arena_avail_tree_, arena_avail_tree_t,
    arena_chunk_map_t, link, arena_avail_comp)

static inline void
arena_run_rc_incr(arena_run_t *run, arena_bin_t *bin, const void *ptr)
{
        arena_chunk_t *chunk;
        arena_t *arena;
        size_t pagebeg, pageend, i;

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
        arena = chunk->arena;
        pagebeg = ((uintptr_t)ptr - (uintptr_t)chunk) >> PAGE_SHIFT;
        pageend = ((uintptr_t)ptr + (uintptr_t)(bin->reg_size - 1) -
            (uintptr_t)chunk) >> PAGE_SHIFT;

        for (i = pagebeg; i <= pageend; i++) {
                size_t mapbits = chunk->map[i].bits;

                if (mapbits & CHUNK_MAP_DIRTY) {
                        assert((mapbits & CHUNK_MAP_RC_MASK) == 0);
                        chunk->ndirty--;
                        arena->ndirty--;
                        mapbits ^= CHUNK_MAP_DIRTY;
                }
                assert((mapbits & CHUNK_MAP_RC_MASK) != CHUNK_MAP_RC_MASK);
                mapbits += CHUNK_MAP_RC_ONE;
                chunk->map[i].bits = mapbits;
        }
}

static inline void
arena_run_rc_decr(arena_run_t *run, arena_bin_t *bin, const void *ptr)
{
        arena_chunk_t *chunk;
        arena_t *arena;
        size_t pagebeg, pageend, mapbits, i;
        bool dirtier = false;

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
        arena = chunk->arena;
        pagebeg = ((uintptr_t)ptr - (uintptr_t)chunk) >> PAGE_SHIFT;
        pageend = ((uintptr_t)ptr + (uintptr_t)(bin->reg_size - 1) -
            (uintptr_t)chunk) >> PAGE_SHIFT;

        /* First page. */
        mapbits = chunk->map[pagebeg].bits;
        mapbits -= CHUNK_MAP_RC_ONE;
        if ((mapbits & CHUNK_MAP_RC_MASK) == 0) {
                dirtier = true;
                assert((mapbits & CHUNK_MAP_DIRTY) == 0);
                mapbits |= CHUNK_MAP_DIRTY;
                chunk->ndirty++;
                arena->ndirty++;
        }
        chunk->map[pagebeg].bits = mapbits;

        if (pageend - pagebeg >= 1) {
                /*
                 * Interior pages are completely consumed by the object being
                 * deallocated, which means that the pages can be
                 * unconditionally marked dirty.
                 */
                for (i = pagebeg + 1; i < pageend; i++) {
                        mapbits = chunk->map[i].bits;
                        mapbits -= CHUNK_MAP_RC_ONE;
                        assert((mapbits & CHUNK_MAP_RC_MASK) == 0);
                        dirtier = true;
                        assert((mapbits & CHUNK_MAP_DIRTY) == 0);
                        mapbits |= CHUNK_MAP_DIRTY;
                        chunk->ndirty++;
                        arena->ndirty++;
                        chunk->map[i].bits = mapbits;
                }

                /* Last page. */
                mapbits = chunk->map[pageend].bits;
                mapbits -= CHUNK_MAP_RC_ONE;
                if ((mapbits & CHUNK_MAP_RC_MASK) == 0) {
                        dirtier = true;
                        assert((mapbits & CHUNK_MAP_DIRTY) == 0);
                        mapbits |= CHUNK_MAP_DIRTY;
                        chunk->ndirty++;
                        arena->ndirty++;
                }
                chunk->map[pageend].bits = mapbits;
        }

        if (dirtier) {
                if (chunk->dirtied == false) {
                        arena_chunk_tree_dirty_insert(&arena->chunks_dirty,
                            chunk);
                        chunk->dirtied = true;
                }

                /* Enforce opt_lg_dirty_mult. */
                if (opt_lg_dirty_mult >= 0 && (arena->nactive >>
                    opt_lg_dirty_mult) < arena->ndirty)
                        arena_purge(arena);
        }
}

static inline void *
arena_run_reg_alloc(arena_run_t *run, arena_bin_t *bin)
{
        void *ret;
        unsigned i, mask, bit, regind;

        assert(run->magic == ARENA_RUN_MAGIC);
        assert(run->regs_minelm < bin->regs_mask_nelms);

        /*
         * Move the first check outside the loop, so that run->regs_minelm can
         * be updated unconditionally, without the possibility of updating it
         * multiple times.
         */
        i = run->regs_minelm;
        mask = run->regs_mask[i];
        if (mask != 0) {
                /* Usable allocation found. */
                bit = ffs((int)mask) - 1;

                regind = ((i << (LG_SIZEOF_INT + 3)) + bit);
                assert(regind < bin->nregs);
                ret = (void *)(((uintptr_t)run) + bin->reg0_offset
                    + (bin->reg_size * regind));

                /* Clear bit. */
                mask ^= (1U << bit);
                run->regs_mask[i] = mask;

                arena_run_rc_incr(run, bin, ret);

                return (ret);
        }

        for (i++; i < bin->regs_mask_nelms; i++) {
                mask = run->regs_mask[i];
                if (mask != 0) {
                        /* Usable allocation found. */
                        bit = ffs((int)mask) - 1;

                        regind = ((i << (LG_SIZEOF_INT + 3)) + bit);
                        assert(regind < bin->nregs);
                        ret = (void *)(((uintptr_t)run) + bin->reg0_offset
                            + (bin->reg_size * regind));

                        /* Clear bit. */
                        mask ^= (1U << bit);
                        run->regs_mask[i] = mask;

                        /*
                         * Make a note that nothing before this element
                         * contains a free region.
                         */
                        run->regs_minelm = i; /* Low payoff: + (mask == 0); */

                        arena_run_rc_incr(run, bin, ret);

                        return (ret);
                }
        }
        /* Not reached. */
        assert(0);
        return (NULL);
}

static inline void
arena_run_reg_dalloc(arena_run_t *run, arena_bin_t *bin, void *ptr, size_t size)
{
        unsigned shift, diff, regind, elm, bit;

        assert(run->magic == ARENA_RUN_MAGIC);

        /*
         * Avoid doing division with a variable divisor if possible.  Using
         * actual division here can reduce allocator throughput by over 20%!
         */
        diff = (unsigned)((uintptr_t)ptr - (uintptr_t)run - bin->reg0_offset);

        /* Rescale (factor powers of 2 out of the numerator and denominator). */
        shift = ffs(size) - 1;
        diff >>= shift;
        size >>= shift;

        if (size == 1) {
                /* The divisor was a power of 2. */
                regind = diff;
        } else {
                /*
                 * To divide by a number D that is not a power of two we
                 * multiply by (2^21 / D) and then right shift by 21 positions.
                 *
                 *   X / D
                 *
                 * becomes
                 *
                 *   (X * size_invs[D - 3]) >> SIZE_INV_SHIFT
                 *
                 * We can omit the first three elements, because we never
                 * divide by 0, and 1 and 2 are both powers of two, which are
                 * handled above.
                 */
#define SIZE_INV_SHIFT 21
#define SIZE_INV(s) (((1U << SIZE_INV_SHIFT) / (s)) + 1)
                static const unsigned size_invs[] = {
                    SIZE_INV(3),
                    SIZE_INV(4), SIZE_INV(5), SIZE_INV(6), SIZE_INV(7),
                    SIZE_INV(8), SIZE_INV(9), SIZE_INV(10), SIZE_INV(11),
                    SIZE_INV(12), SIZE_INV(13), SIZE_INV(14), SIZE_INV(15),
                    SIZE_INV(16), SIZE_INV(17), SIZE_INV(18), SIZE_INV(19),
                    SIZE_INV(20), SIZE_INV(21), SIZE_INV(22), SIZE_INV(23),
                    SIZE_INV(24), SIZE_INV(25), SIZE_INV(26), SIZE_INV(27),
                    SIZE_INV(28), SIZE_INV(29), SIZE_INV(30), SIZE_INV(31)
                };

                if (size <= ((sizeof(size_invs) / sizeof(unsigned)) + 2))
                        regind = (diff * size_invs[size - 3]) >> SIZE_INV_SHIFT;
                else
                        regind = diff / size;
#undef SIZE_INV
#undef SIZE_INV_SHIFT
        }
        assert(diff == regind * size);
        assert(regind < bin->nregs);

        elm = regind >> (LG_SIZEOF_INT + 3);
        if (elm < run->regs_minelm)
                run->regs_minelm = elm;
        bit = regind - (elm << (LG_SIZEOF_INT + 3));
        assert((run->regs_mask[elm] & (1U << bit)) == 0);
        run->regs_mask[elm] |= (1U << bit);

        arena_run_rc_decr(run, bin, ptr);
}

static void
arena_run_split(arena_t *arena, arena_run_t *run, size_t size, bool large,
    bool zero)
{
        arena_chunk_t *chunk;
        size_t old_ndirty, run_ind, total_pages, need_pages, rem_pages, i;

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(run);
        old_ndirty = chunk->ndirty;
        run_ind = (unsigned)(((uintptr_t)run - (uintptr_t)chunk)
            >> PAGE_SHIFT);
        total_pages = (chunk->map[run_ind].bits & ~PAGE_MASK) >>
            PAGE_SHIFT;
        need_pages = (size >> PAGE_SHIFT);
        assert(need_pages > 0);
        assert(need_pages <= total_pages);
        rem_pages = total_pages - need_pages;

        arena_avail_tree_remove(&arena->runs_avail, &chunk->map[run_ind]);
        arena->nactive += need_pages;

        /* Keep track of trailing unused pages for later use. */
        if (rem_pages > 0) {
                chunk->map[run_ind+need_pages].bits = (rem_pages <<
                    PAGE_SHIFT) | (chunk->map[run_ind+need_pages].bits &
                    CHUNK_MAP_FLAGS_MASK);
                chunk->map[run_ind+total_pages-1].bits = (rem_pages <<
                    PAGE_SHIFT) | (chunk->map[run_ind+total_pages-1].bits &
                    CHUNK_MAP_FLAGS_MASK);
                arena_avail_tree_insert(&arena->runs_avail,
                    &chunk->map[run_ind+need_pages]);
        }

        for (i = 0; i < need_pages; i++) {
                /* Zero if necessary. */
                if (zero) {
                        if ((chunk->map[run_ind + i].bits & CHUNK_MAP_ZEROED)
                            == 0) {
                                memset((void *)((uintptr_t)chunk + ((run_ind
                                    + i) << PAGE_SHIFT)), 0, PAGE_SIZE);
                                /* CHUNK_MAP_ZEROED is cleared below. */
                        }
                }

                /* Update dirty page accounting. */
                if (chunk->map[run_ind + i].bits & CHUNK_MAP_DIRTY) {
                        chunk->ndirty--;
                        arena->ndirty--;
                        /* CHUNK_MAP_DIRTY is cleared below. */
                }

                /* Initialize the chunk map. */
                if (large) {
                        chunk->map[run_ind + i].bits = CHUNK_MAP_LARGE
                            | CHUNK_MAP_ALLOCATED;
                } else {
                        chunk->map[run_ind + i].bits = (i << CHUNK_MAP_PG_SHIFT)
                            | CHUNK_MAP_ALLOCATED;
                }
        }

        if (large) {
                /*
                 * Set the run size only in the first element for large runs.
                 * This is primarily a debugging aid, since the lack of size
                 * info for trailing pages only matters if the application
                 * tries to operate on an interior pointer.
                 */
                chunk->map[run_ind].bits |= size;
        } else {
                /*
                 * Initialize the first page's refcount to 1, so that the run
                 * header is protected from dirty page purging.
                 */
                chunk->map[run_ind].bits += CHUNK_MAP_RC_ONE;
        }
}

static arena_chunk_t *
arena_chunk_alloc(arena_t *arena)
{
        arena_chunk_t *chunk;
        size_t i;

        if (arena->spare != NULL) {
                chunk = arena->spare;
                arena->spare = NULL;
        } else {
                bool zero;
                size_t zeroed;

                zero = false;
                chunk = (arena_chunk_t *)chunk_alloc(chunksize, &zero);
                if (chunk == NULL)
                        return (NULL);
#ifdef MALLOC_STATS
                arena->stats.mapped += chunksize;
#endif

                chunk->arena = arena;
                chunk->dirtied = false;

                /*
                 * Claim that no pages are in use, since the header is merely
                 * overhead.
                 */
                chunk->ndirty = 0;

                /*
                 * Initialize the map to contain one maximal free untouched run.
                 * Mark the pages as zeroed iff chunk_alloc() returned a zeroed
                 * chunk.
                 */
                zeroed = zero ? CHUNK_MAP_ZEROED : 0;
                for (i = 0; i < arena_chunk_header_npages; i++)
                        chunk->map[i].bits = 0;
                chunk->map[i].bits = arena_maxclass | zeroed;
                for (i++; i < chunk_npages-1; i++)
                        chunk->map[i].bits = zeroed;
                chunk->map[chunk_npages-1].bits = arena_maxclass | zeroed;
        }

        /* Insert the run into the runs_avail tree. */
        arena_avail_tree_insert(&arena->runs_avail,
            &chunk->map[arena_chunk_header_npages]);

        return (chunk);
}

static void
arena_chunk_dealloc(arena_t *arena, arena_chunk_t *chunk)
{

        if (arena->spare != NULL) {
                if (arena->spare->dirtied) {
                        arena_chunk_tree_dirty_remove(
                            &chunk->arena->chunks_dirty, arena->spare);
                        arena->ndirty -= arena->spare->ndirty;
                }
                chunk_dealloc((void *)arena->spare, chunksize);
#ifdef MALLOC_STATS
                arena->stats.mapped -= chunksize;
#endif
        }

        /*
         * Remove run from runs_avail, regardless of whether this chunk
         * will be cached, so that the arena does not use it.  Dirty page
         * flushing only uses the chunks_dirty tree, so leaving this chunk in
         * the chunks_* trees is sufficient for that purpose.
         */
        arena_avail_tree_remove(&arena->runs_avail,
            &chunk->map[arena_chunk_header_npages]);

        arena->spare = chunk;
}

static arena_run_t *
arena_run_alloc(arena_t *arena, size_t size, bool large, bool zero)
{
        arena_chunk_t *chunk;
        arena_run_t *run;
        arena_chunk_map_t *mapelm, key;

        assert(size <= arena_maxclass);
        assert((size & PAGE_MASK) == 0);

        /* Search the arena's chunks for the lowest best fit. */
        key.bits = size | CHUNK_MAP_KEY;
        mapelm = arena_avail_tree_nsearch(&arena->runs_avail, &key);
        if (mapelm != NULL) {
                arena_chunk_t *run_chunk = CHUNK_ADDR2BASE(mapelm);
                size_t pageind = ((uintptr_t)mapelm - (uintptr_t)run_chunk->map)
                    / sizeof(arena_chunk_map_t);

                run = (arena_run_t *)((uintptr_t)run_chunk + (pageind
                    << PAGE_SHIFT));
                arena_run_split(arena, run, size, large, zero);
                return (run);
        }

        /*
         * No usable runs.  Create a new chunk from which to allocate the run.
         */
        chunk = arena_chunk_alloc(arena);
        if (chunk == NULL)
                return (NULL);
        run = (arena_run_t *)((uintptr_t)chunk + (arena_chunk_header_npages <<
            PAGE_SHIFT));
        /* Update page map. */
        arena_run_split(arena, run, size, large, zero);
        return (run);
}

#ifdef MALLOC_DEBUG
static arena_chunk_t *
chunks_dirty_iter_cb(arena_chunk_tree_t *tree, arena_chunk_t *chunk, void *arg)
{
        size_t *ndirty = (size_t *)arg;

        assert(chunk->dirtied);
        *ndirty += chunk->ndirty;
        return (NULL);
}
#endif

static void
arena_purge(arena_t *arena)
{
        arena_chunk_t *chunk;
        size_t i, npages;
#ifdef MALLOC_DEBUG
        size_t ndirty = 0;

        arena_chunk_tree_dirty_iter(&arena->chunks_dirty, NULL,
            chunks_dirty_iter_cb, (void *)&ndirty);
        assert(ndirty == arena->ndirty);
#endif
        assert((arena->nactive >> opt_lg_dirty_mult) < arena->ndirty);

#ifdef MALLOC_STATS
        arena->stats.npurge++;
#endif

        /*
         * Iterate downward through chunks until enough dirty memory has been
         * purged.  Terminate as soon as possible in order to minimize the
         * number of system calls, even if a chunk has only been partially
         * purged.
         */

        while ((arena->nactive >> (opt_lg_dirty_mult + 1)) < arena->ndirty) {
                chunk = arena_chunk_tree_dirty_last(&arena->chunks_dirty);
                assert(chunk != NULL);

                for (i = chunk_npages - 1; chunk->ndirty > 0; i--) {
                        assert(i >= arena_chunk_header_npages);
                        if (chunk->map[i].bits & CHUNK_MAP_DIRTY) {
                                chunk->map[i].bits ^= CHUNK_MAP_DIRTY;
                                /* Find adjacent dirty run(s). */
                                for (npages = 1; i > arena_chunk_header_npages
                                    && (chunk->map[i - 1].bits &
                                    CHUNK_MAP_DIRTY); npages++) {
                                        i--;
                                        chunk->map[i].bits ^= CHUNK_MAP_DIRTY;
                                }
                                chunk->ndirty -= npages;
                                arena->ndirty -= npages;

                                madvise((void *)((uintptr_t)chunk + (i <<
                                    PAGE_SHIFT)), (npages << PAGE_SHIFT),
                                    MADV_FREE);
#ifdef MALLOC_STATS
                                arena->stats.nmadvise++;
                                arena->stats.purged += npages;
#endif
                                if ((arena->nactive >> (opt_lg_dirty_mult + 1))
                                    >= arena->ndirty)
                                        break;
                        }
                }

                if (chunk->ndirty == 0) {
                        arena_chunk_tree_dirty_remove(&arena->chunks_dirty,
                            chunk);
                        chunk->dirtied = false;
                }
        }
}

static void
arena_run_dalloc(arena_t *arena, arena_run_t *run, bool dirty)
{
        arena_chunk_t *chunk;
        size_t size, run_ind, run_pages;

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(run);
        run_ind = (size_t)(((uintptr_t)run - (uintptr_t)chunk)
            >> PAGE_SHIFT);
        assert(run_ind >= arena_chunk_header_npages);
        assert(run_ind < chunk_npages);
        if ((chunk->map[run_ind].bits & CHUNK_MAP_LARGE) != 0)
                size = chunk->map[run_ind].bits & ~PAGE_MASK;
        else
                size = run->bin->run_size;
        run_pages = (size >> PAGE_SHIFT);
        arena->nactive -= run_pages;

        /* Mark pages as unallocated in the chunk map. */
        if (dirty) {
                size_t i;

                for (i = 0; i < run_pages; i++) {
                        /*
                         * When (dirty == true), *all* pages within the run
                         * need to have their dirty bits set, because only
                         * small runs can create a mixture of clean/dirty
                         * pages, but such runs are passed to this function
                         * with (dirty == false).
                         */
                        assert((chunk->map[run_ind + i].bits & CHUNK_MAP_DIRTY)
                            == 0);
                        chunk->ndirty++;
                        arena->ndirty++;
                        chunk->map[run_ind + i].bits = CHUNK_MAP_DIRTY;
                }
        } else {
                size_t i;

                for (i = 0; i < run_pages; i++) {
                        chunk->map[run_ind + i].bits &= ~(CHUNK_MAP_LARGE |
                            CHUNK_MAP_ALLOCATED);
                }
        }
        chunk->map[run_ind].bits = size | (chunk->map[run_ind].bits &
            CHUNK_MAP_FLAGS_MASK);
        chunk->map[run_ind+run_pages-1].bits = size |
            (chunk->map[run_ind+run_pages-1].bits & CHUNK_MAP_FLAGS_MASK);

        /* Try to coalesce forward. */
        if (run_ind + run_pages < chunk_npages &&
            (chunk->map[run_ind+run_pages].bits & CHUNK_MAP_ALLOCATED) == 0) {
                size_t nrun_size = chunk->map[run_ind+run_pages].bits &
                    ~PAGE_MASK;

                /*
                 * Remove successor from runs_avail; the coalesced run is
                 * inserted later.
                 */
                arena_avail_tree_remove(&arena->runs_avail,
                    &chunk->map[run_ind+run_pages]);

                size += nrun_size;
                run_pages = size >> PAGE_SHIFT;

                assert((chunk->map[run_ind+run_pages-1].bits & ~PAGE_MASK)
                    == nrun_size);
                chunk->map[run_ind].bits = size | (chunk->map[run_ind].bits &
                    CHUNK_MAP_FLAGS_MASK);
                chunk->map[run_ind+run_pages-1].bits = size |
                    (chunk->map[run_ind+run_pages-1].bits &
                    CHUNK_MAP_FLAGS_MASK);
        }

        /* Try to coalesce backward. */
        if (run_ind > arena_chunk_header_npages && (chunk->map[run_ind-1].bits &
            CHUNK_MAP_ALLOCATED) == 0) {
                size_t prun_size = chunk->map[run_ind-1].bits & ~PAGE_MASK;

                run_ind -= prun_size >> PAGE_SHIFT;

                /*
                 * Remove predecessor from runs_avail; the coalesced run is
                 * inserted later.
                 */
                arena_avail_tree_remove(&arena->runs_avail,
                    &chunk->map[run_ind]);

                size += prun_size;
                run_pages = size >> PAGE_SHIFT;

                assert((chunk->map[run_ind].bits & ~PAGE_MASK) == prun_size);
                chunk->map[run_ind].bits = size | (chunk->map[run_ind].bits &
                    CHUNK_MAP_FLAGS_MASK);
                chunk->map[run_ind+run_pages-1].bits = size |
                    (chunk->map[run_ind+run_pages-1].bits &
                    CHUNK_MAP_FLAGS_MASK);
        }

        /* Insert into runs_avail, now that coalescing is complete. */
        arena_avail_tree_insert(&arena->runs_avail, &chunk->map[run_ind]);

        /*
         * Deallocate chunk if it is now completely unused.  The bit
         * manipulation checks whether the first run is unallocated and extends
         * to the end of the chunk.
         */
        if ((chunk->map[arena_chunk_header_npages].bits & (~PAGE_MASK |
            CHUNK_MAP_ALLOCATED)) == arena_maxclass)
                arena_chunk_dealloc(arena, chunk);

        /*
         * It is okay to do dirty page processing even if the chunk was
         * deallocated above, since in that case it is the spare.  Waiting
         * until after possible chunk deallocation to do dirty processing
         * allows for an old spare to be fully deallocated, thus decreasing the
         * chances of spuriously crossing the dirty page purging threshold.
         */
        if (dirty) {
                if (chunk->dirtied == false) {
                        arena_chunk_tree_dirty_insert(&arena->chunks_dirty,
                            chunk);
                        chunk->dirtied = true;
                }

                /* Enforce opt_lg_dirty_mult. */
                if (opt_lg_dirty_mult >= 0 && (arena->nactive >>
                    opt_lg_dirty_mult) < arena->ndirty)
                        arena_purge(arena);
        }
}

static void
arena_run_trim_head(arena_t *arena, arena_chunk_t *chunk, arena_run_t *run,
    size_t oldsize, size_t newsize)
{
        size_t pageind = ((uintptr_t)run - (uintptr_t)chunk) >> PAGE_SHIFT;
        size_t head_npages = (oldsize - newsize) >> PAGE_SHIFT;

        assert(oldsize > newsize);

        /*
         * Update the chunk map so that arena_run_dalloc() can treat the
         * leading run as separately allocated.
         */
        assert((chunk->map[pageind].bits & CHUNK_MAP_DIRTY) == 0);
        chunk->map[pageind].bits = (oldsize - newsize) | CHUNK_MAP_LARGE |
            CHUNK_MAP_ALLOCATED;
        assert((chunk->map[pageind+head_npages].bits & CHUNK_MAP_DIRTY) == 0);
        chunk->map[pageind+head_npages].bits = newsize | CHUNK_MAP_LARGE |
            CHUNK_MAP_ALLOCATED;

        arena_run_dalloc(arena, run, false);
}

static void
arena_run_trim_tail(arena_t *arena, arena_chunk_t *chunk, arena_run_t *run,
    size_t oldsize, size_t newsize, bool dirty)
{
        size_t pageind = ((uintptr_t)run - (uintptr_t)chunk) >> PAGE_SHIFT;
        size_t npages = newsize >> PAGE_SHIFT;

        assert(oldsize > newsize);

        /*
         * Update the chunk map so that arena_run_dalloc() can treat the
         * trailing run as separately allocated.
         */
        assert((chunk->map[pageind].bits & CHUNK_MAP_DIRTY) == 0);
        chunk->map[pageind].bits = newsize | CHUNK_MAP_LARGE |
            CHUNK_MAP_ALLOCATED;
        assert((chunk->map[pageind+npages].bits & CHUNK_MAP_DIRTY) == 0);
        chunk->map[pageind+npages].bits = (oldsize - newsize) | CHUNK_MAP_LARGE
            | CHUNK_MAP_ALLOCATED;

        arena_run_dalloc(arena, (arena_run_t *)((uintptr_t)run + newsize),
            dirty);
}

static arena_run_t *
arena_bin_nonfull_run_get(arena_t *arena, arena_bin_t *bin)
{
        arena_chunk_map_t *mapelm;
        arena_run_t *run;
        unsigned i, remainder;

        /* Look for a usable run. */
        mapelm = arena_run_tree_first(&bin->runs);
        if (mapelm != NULL) {
                arena_chunk_t *chunk;
                size_t pageind;

                /* run is guaranteed to have available space. */
                arena_run_tree_remove(&bin->runs, mapelm);

                chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(mapelm);
                pageind = (((uintptr_t)mapelm - (uintptr_t)chunk->map) /
                    sizeof(arena_chunk_map_t));
                run = (arena_run_t *)((uintptr_t)chunk + (uintptr_t)((pageind -
                    ((mapelm->bits & CHUNK_MAP_PG_MASK) >> CHUNK_MAP_PG_SHIFT))
                    << PAGE_SHIFT));
#ifdef MALLOC_STATS
                bin->stats.reruns++;
#endif
                return (run);
        }
        /* No existing runs have any space available. */

        /* Allocate a new run. */
        run = arena_run_alloc(arena, bin->run_size, false, false);
        if (run == NULL)
                return (NULL);

        /* Initialize run internals. */
        run->bin = bin;

        for (i = 0; i < bin->regs_mask_nelms - 1; i++)
                run->regs_mask[i] = UINT_MAX;
        remainder = bin->nregs & ((1U << (LG_SIZEOF_INT + 3)) - 1);
        if (remainder == 0)
                run->regs_mask[i] = UINT_MAX;
        else {
                /* The last element has spare bits that need to be unset. */
                run->regs_mask[i] = (UINT_MAX >> ((1U << (LG_SIZEOF_INT + 3))
                    - remainder));
        }

        run->regs_minelm = 0;

        run->nfree = bin->nregs;
#ifdef MALLOC_DEBUG
        run->magic = ARENA_RUN_MAGIC;
#endif

#ifdef MALLOC_STATS
        bin->stats.nruns++;
        bin->stats.curruns++;
        if (bin->stats.curruns > bin->stats.highruns)
                bin->stats.highruns = bin->stats.curruns;
#endif
        return (run);
}

/* bin->runcur must have space available before this function is called. */
static inline void *
arena_bin_malloc_easy(arena_t *arena, arena_bin_t *bin, arena_run_t *run)
{
        void *ret;

        assert(run->magic == ARENA_RUN_MAGIC);
        assert(run->nfree > 0);

        ret = arena_run_reg_alloc(run, bin);
        assert(ret != NULL);
        run->nfree--;

        return (ret);
}

/* Re-fill bin->runcur, then call arena_bin_malloc_easy(). */
static void *
arena_bin_malloc_hard(arena_t *arena, arena_bin_t *bin)
{

        bin->runcur = arena_bin_nonfull_run_get(arena, bin);
        if (bin->runcur == NULL)
                return (NULL);
        assert(bin->runcur->magic == ARENA_RUN_MAGIC);
        assert(bin->runcur->nfree > 0);

        return (arena_bin_malloc_easy(arena, bin, bin->runcur));
}

/*
 * Calculate bin->run_size such that it meets the following constraints:
 *
 *   *) bin->run_size >= min_run_size
 *   *) bin->run_size <= arena_maxclass
 *   *) bin->run_size <= RUN_MAX_SMALL
 *   *) run header overhead <= RUN_MAX_OVRHD (or header overhead relaxed).
 *   *) run header size < PAGE_SIZE
 *
 * bin->nregs, bin->regs_mask_nelms, and bin->reg0_offset are
 * also calculated here, since these settings are all interdependent.
 */
static size_t
arena_bin_run_size_calc(arena_bin_t *bin, size_t min_run_size)
{
        size_t try_run_size, good_run_size;
        unsigned good_nregs, good_mask_nelms, good_reg0_offset;
        unsigned try_nregs, try_mask_nelms, try_reg0_offset;

        assert(min_run_size >= PAGE_SIZE);
        assert(min_run_size <= arena_maxclass);
        assert(min_run_size <= RUN_MAX_SMALL);

        /*
         * Calculate known-valid settings before entering the run_size
         * expansion loop, so that the first part of the loop always copies
         * valid settings.
         *
         * The do..while loop iteratively reduces the number of regions until
         * the run header and the regions no longer overlap.  A closed formula
         * would be quite messy, since there is an interdependency between the
         * header's mask length and the number of regions.
         */
        try_run_size = min_run_size;
        try_nregs = ((try_run_size - sizeof(arena_run_t)) / bin->reg_size)
            + 1; /* Counter-act try_nregs-- in loop. */
        do {
                try_nregs--;
                try_mask_nelms = (try_nregs >> (LG_SIZEOF_INT + 3)) +
                    ((try_nregs & ((1U << (LG_SIZEOF_INT + 3)) - 1)) ? 1 : 0);
                try_reg0_offset = try_run_size - (try_nregs * bin->reg_size);
        } while (sizeof(arena_run_t) + (sizeof(unsigned) * (try_mask_nelms - 1))
            > try_reg0_offset);

        /* run_size expansion loop. */
        do {
                /*
                 * Copy valid settings before trying more aggressive settings.
                 */
                good_run_size = try_run_size;
                good_nregs = try_nregs;
                good_mask_nelms = try_mask_nelms;
                good_reg0_offset = try_reg0_offset;

                /* Try more aggressive settings. */
                try_run_size += PAGE_SIZE;
                try_nregs = ((try_run_size - sizeof(arena_run_t)) /
                    bin->reg_size) + 1; /* Counter-act try_nregs-- in loop. */
                do {
                        try_nregs--;
                        try_mask_nelms = (try_nregs >> (LG_SIZEOF_INT + 3)) +
                            ((try_nregs & ((1U << (LG_SIZEOF_INT + 3)) - 1)) ?
                            1 : 0);
                        try_reg0_offset = try_run_size - (try_nregs *
                            bin->reg_size);
                } while (sizeof(arena_run_t) + (sizeof(unsigned) *
                    (try_mask_nelms - 1)) > try_reg0_offset);
        } while (try_run_size <= arena_maxclass && try_run_size <= RUN_MAX_SMALL
            && RUN_MAX_OVRHD * (bin->reg_size << 3) > RUN_MAX_OVRHD_RELAX
            && (try_reg0_offset << RUN_BFP) > RUN_MAX_OVRHD * try_run_size
            && (sizeof(arena_run_t) + (sizeof(unsigned) * (try_mask_nelms - 1)))
            < PAGE_SIZE);

        assert(sizeof(arena_run_t) + (sizeof(unsigned) * (good_mask_nelms - 1))
            <= good_reg0_offset);
        assert((good_mask_nelms << (LG_SIZEOF_INT + 3)) >= good_nregs);

        /* Copy final settings. */
        bin->run_size = good_run_size;
        bin->nregs = good_nregs;
        bin->regs_mask_nelms = good_mask_nelms;
        bin->reg0_offset = good_reg0_offset;

        return (good_run_size);
}

#ifdef MALLOC_TCACHE
static inline void
tcache_event(tcache_t *tcache)
{

        if (tcache_gc_incr == 0)
                return;

        tcache->ev_cnt++;
        assert(tcache->ev_cnt <= tcache_gc_incr);
        if (tcache->ev_cnt >= tcache_gc_incr) {
                size_t binind = tcache->next_gc_bin;
                tcache_bin_t *tbin = tcache->tbins[binind];

                if (tbin != NULL) {
                        if (tbin->high_water == 0) {
                                /*
                                 * This bin went completely unused for an
                                 * entire GC cycle, so throw away the tbin.
                                 */
                                assert(tbin->ncached == 0);
                                tcache_bin_destroy(tcache, tbin, binind);
                                tcache->tbins[binind] = NULL;
                        } else {
                                if (tbin->low_water > 0) {
                                        /*
                                         * Flush (ceiling) half of the objects
                                         * below the low water mark.
                                         */
                                        tcache_bin_flush(tbin, binind,
                                            tbin->ncached - (tbin->low_water >>
                                            1) - (tbin->low_water & 1));
                                }
                                tbin->low_water = tbin->ncached;
                                tbin->high_water = tbin->ncached;
                        }
                }

                tcache->next_gc_bin++;
                if (tcache->next_gc_bin == nbins)
                        tcache->next_gc_bin = 0;
                tcache->ev_cnt = 0;
        }
}

static inline void *
tcache_bin_alloc(tcache_bin_t *tbin)
{

        if (tbin->ncached == 0)
                return (NULL);
        tbin->ncached--;
        if (tbin->ncached < tbin->low_water)
                tbin->low_water = tbin->ncached;
        return (tbin->slots[tbin->ncached]);
}

static void
tcache_bin_fill(tcache_t *tcache, tcache_bin_t *tbin, size_t binind)
{
        arena_t *arena;
        arena_bin_t *bin;
        arena_run_t *run;
        void *ptr;
        unsigned i;

        assert(tbin->ncached == 0);

        arena = tcache->arena;
        bin = &arena->bins[binind];
        malloc_spin_lock(&arena->lock);
        for (i = 0; i < (tcache_nslots >> 1); i++) {
                if ((run = bin->runcur) != NULL && run->nfree > 0)
                        ptr = arena_bin_malloc_easy(arena, bin, run);
                else
                        ptr = arena_bin_malloc_hard(arena, bin);
                if (ptr == NULL)
                        break;
                /*
                 * Fill tbin such that the objects lowest in memory are used
                 * first.
                 */
                tbin->slots[(tcache_nslots >> 1) - 1 - i] = ptr;
        }
#ifdef MALLOC_STATS
        bin->stats.nfills++;
        bin->stats.nrequests += tbin->tstats.nrequests;
        if (bin->reg_size <= small_maxclass) {
                arena->stats.nmalloc_small += (i - tbin->ncached);
                arena->stats.allocated_small += (i - tbin->ncached) *
                    bin->reg_size;
                arena->stats.nmalloc_small += tbin->tstats.nrequests;
        } else {
                arena->stats.nmalloc_medium += (i - tbin->ncached);
                arena->stats.allocated_medium += (i - tbin->ncached) *
                    bin->reg_size;
                arena->stats.nmalloc_medium += tbin->tstats.nrequests;
        }
        tbin->tstats.nrequests = 0;
#endif
        malloc_spin_unlock(&arena->lock);
        tbin->ncached = i;
        if (tbin->ncached > tbin->high_water)
                tbin->high_water = tbin->ncached;
}

static inline void *
tcache_alloc(tcache_t *tcache, size_t size, bool zero)
{
        void *ret;
        tcache_bin_t *tbin;
        size_t binind;

        if (size <= small_maxclass)
                binind = small_size2bin[size];
        else {
                binind = mbin0 + ((MEDIUM_CEILING(size) - medium_min) >>
                    lg_mspace);
        }
        assert(binind < nbins);
        tbin = tcache->tbins[binind];
        if (tbin == NULL) {
                tbin = tcache_bin_create(tcache->arena);
                if (tbin == NULL)
                        return (NULL);
                tcache->tbins[binind] = tbin;
        }

        ret = tcache_bin_alloc(tbin);
        if (ret == NULL) {
                ret = tcache_alloc_hard(tcache, tbin, binind);
                if (ret == NULL)
                        return (NULL);
        }

        if (zero == false) {
                if (opt_junk)
                        memset(ret, 0xa5, size);
                else if (opt_zero)
                        memset(ret, 0, size);
        } else
                memset(ret, 0, size);

#ifdef MALLOC_STATS
        tbin->tstats.nrequests++;
#endif
        tcache_event(tcache);
        return (ret);
}

static void *
tcache_alloc_hard(tcache_t *tcache, tcache_bin_t *tbin, size_t binind)
{
        void *ret;

        tcache_bin_fill(tcache, tbin, binind);
        ret = tcache_bin_alloc(tbin);

        return (ret);
}
#endif

static inline void *
arena_malloc_small(arena_t *arena, size_t size, bool zero)
{
        void *ret;
        arena_bin_t *bin;
        arena_run_t *run;
        size_t binind;

        binind = small_size2bin[size];
        assert(binind < mbin0);
        bin = &arena->bins[binind];
        size = bin->reg_size;

        malloc_spin_lock(&arena->lock);
        if ((run = bin->runcur) != NULL && run->nfree > 0)
                ret = arena_bin_malloc_easy(arena, bin, run);
        else
                ret = arena_bin_malloc_hard(arena, bin);

        if (ret == NULL) {
                malloc_spin_unlock(&arena->lock);
                return (NULL);
        }

#ifdef MALLOC_STATS
#  ifdef MALLOC_TCACHE
        if (__isthreaded == false) {
#  endif
                bin->stats.nrequests++;
                arena->stats.nmalloc_small++;
#  ifdef MALLOC_TCACHE
        }
#  endif
        arena->stats.allocated_small += size;
#endif
        malloc_spin_unlock(&arena->lock);

        if (zero == false) {
                if (opt_junk)
                        memset(ret, 0xa5, size);
                else if (opt_zero)
                        memset(ret, 0, size);
        } else
                memset(ret, 0, size);

        return (ret);
}

static void *
arena_malloc_medium(arena_t *arena, size_t size, bool zero)
{
        void *ret;
        arena_bin_t *bin;
        arena_run_t *run;
        size_t binind;

        size = MEDIUM_CEILING(size);
        binind = mbin0 + ((size - medium_min) >> lg_mspace);
        assert(binind < nbins);
        bin = &arena->bins[binind];
        assert(bin->reg_size == size);

        malloc_spin_lock(&arena->lock);
        if ((run = bin->runcur) != NULL && run->nfree > 0)
                ret = arena_bin_malloc_easy(arena, bin, run);
        else
                ret = arena_bin_malloc_hard(arena, bin);

        if (ret == NULL) {
                malloc_spin_unlock(&arena->lock);
                return (NULL);
        }

#ifdef MALLOC_STATS
#  ifdef MALLOC_TCACHE
        if (__isthreaded == false) {
#  endif
                bin->stats.nrequests++;
                arena->stats.nmalloc_medium++;
#  ifdef MALLOC_TCACHE
        }
#  endif
        arena->stats.allocated_medium += size;
#endif
        malloc_spin_unlock(&arena->lock);

        if (zero == false) {
                if (opt_junk)
                        memset(ret, 0xa5, size);
                else if (opt_zero)
                        memset(ret, 0, size);
        } else
                memset(ret, 0, size);

        return (ret);
}

static void *
arena_malloc_large(arena_t *arena, size_t size, bool zero)
{
        void *ret;

        /* Large allocation. */
        size = PAGE_CEILING(size);
        malloc_spin_lock(&arena->lock);
        ret = (void *)arena_run_alloc(arena, size, true, zero);
        if (ret == NULL) {
                malloc_spin_unlock(&arena->lock);
                return (NULL);
        }
#ifdef MALLOC_STATS
        arena->stats.nmalloc_large++;
        arena->stats.allocated_large += size;
        arena->stats.lstats[(size >> PAGE_SHIFT) - 1].nrequests++;
        arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns++;
        if (arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns >
            arena->stats.lstats[(size >> PAGE_SHIFT) - 1].highruns) {
                arena->stats.lstats[(size >> PAGE_SHIFT) - 1].highruns =
                    arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns;
        }
#endif
        malloc_spin_unlock(&arena->lock);

        if (zero == false) {
                if (opt_junk)
                        memset(ret, 0xa5, size);
                else if (opt_zero)
                        memset(ret, 0, size);
        }

        return (ret);
}

static inline void *
arena_malloc(size_t size, bool zero)
{

        assert(size != 0);
        assert(QUANTUM_CEILING(size) <= arena_maxclass);

        if (size <= bin_maxclass) {
#ifdef MALLOC_TCACHE
                if (__isthreaded && tcache_nslots) {
                        tcache_t *tcache = tcache_tls;
                        if ((uintptr_t)tcache > (uintptr_t)1)
                                return (tcache_alloc(tcache, size, zero));
                        else if (tcache == NULL) {
                                tcache = tcache_create(choose_arena());
                                if (tcache == NULL)
                                        return (NULL);
                                return (tcache_alloc(tcache, size, zero));
                        }
                }
#endif
                if (size <= small_maxclass) {
                        return (arena_malloc_small(choose_arena(), size,
                            zero));
                } else {
                        return (arena_malloc_medium(choose_arena(),
                            size, zero));
                }
        } else
                return (arena_malloc_large(choose_arena(), size, zero));
}

static inline void *
imalloc(size_t size)
{

        assert(size != 0);

        if (size <= arena_maxclass)
                return (arena_malloc(size, false));
        else
                return (huge_malloc(size, false));
}

static inline void *
icalloc(size_t size)
{

        if (size <= arena_maxclass)
                return (arena_malloc(size, true));
        else
                return (huge_malloc(size, true));
}

/* Only handles large allocations that require more than page alignment. */
static void *
arena_palloc(arena_t *arena, size_t alignment, size_t size, size_t alloc_size)
{
        void *ret;
        size_t offset;
        arena_chunk_t *chunk;

        assert((size & PAGE_MASK) == 0);
        assert((alignment & PAGE_MASK) == 0);

        malloc_spin_lock(&arena->lock);
        ret = (void *)arena_run_alloc(arena, alloc_size, true, false);
        if (ret == NULL) {
                malloc_spin_unlock(&arena->lock);
                return (NULL);
        }

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ret);

        offset = (uintptr_t)ret & (alignment - 1);
        assert((offset & PAGE_MASK) == 0);
        assert(offset < alloc_size);
        if (offset == 0)
                arena_run_trim_tail(arena, chunk, ret, alloc_size, size, false);
        else {
                size_t leadsize, trailsize;

                leadsize = alignment - offset;
                if (leadsize > 0) {
                        arena_run_trim_head(arena, chunk, ret, alloc_size,
                            alloc_size - leadsize);
                        ret = (void *)((uintptr_t)ret + leadsize);
                }

                trailsize = alloc_size - leadsize - size;
                if (trailsize != 0) {
                        /* Trim trailing space. */
                        assert(trailsize < alloc_size);
                        arena_run_trim_tail(arena, chunk, ret, size + trailsize,
                            size, false);
                }
        }

#ifdef MALLOC_STATS
        arena->stats.nmalloc_large++;
        arena->stats.allocated_large += size;
        arena->stats.lstats[(size >> PAGE_SHIFT) - 1].nrequests++;
        arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns++;
        if (arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns >
            arena->stats.lstats[(size >> PAGE_SHIFT) - 1].highruns) {
                arena->stats.lstats[(size >> PAGE_SHIFT) - 1].highruns =
                    arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns;
        }
#endif
        malloc_spin_unlock(&arena->lock);

        if (opt_junk)
                memset(ret, 0xa5, size);
        else if (opt_zero)
                memset(ret, 0, size);
        return (ret);
}

static inline void *
ipalloc(size_t alignment, size_t size)
{
        void *ret;
        size_t ceil_size;

        /*
         * Round size up to the nearest multiple of alignment.
         *
         * This done, we can take advantage of the fact that for each small
         * size class, every object is aligned at the smallest power of two
         * that is non-zero in the base two representation of the size.  For
         * example:
         *
         *   Size |   Base 2 | Minimum alignment
         *   -----+----------+------------------
         *     96 |  1100000 |  32
         *    144 | 10100000 |  32
         *    192 | 11000000 |  64
         *
         * Depending on runtime settings, it is possible that arena_malloc()
         * will further round up to a power of two, but that never causes
         * correctness issues.
         */
        ceil_size = (size + (alignment - 1)) & (-alignment);
        /*
         * (ceil_size < size) protects against the combination of maximal
         * alignment and size greater than maximal alignment.
         */
        if (ceil_size < size) {
                /* size_t overflow. */
                return (NULL);
        }

        if (ceil_size <= PAGE_SIZE || (alignment <= PAGE_SIZE
            && ceil_size <= arena_maxclass))
                ret = arena_malloc(ceil_size, false);
        else {
                size_t run_size;

                /*
                 * We can't achieve subpage alignment, so round up alignment
                 * permanently; it makes later calculations simpler.
                 */
                alignment = PAGE_CEILING(alignment);
                ceil_size = PAGE_CEILING(size);
                /*
                 * (ceil_size < size) protects against very large sizes within
                 * PAGE_SIZE of SIZE_T_MAX.
                 *
                 * (ceil_size + alignment < ceil_size) protects against the
                 * combination of maximal alignment and ceil_size large enough
                 * to cause overflow.  This is similar to the first overflow
                 * check above, but it needs to be repeated due to the new
                 * ceil_size value, which may now be *equal* to maximal
                 * alignment, whereas before we only detected overflow if the
                 * original size was *greater* than maximal alignment.
                 */
                if (ceil_size < size || ceil_size + alignment < ceil_size) {
                        /* size_t overflow. */
                        return (NULL);
                }

                /*
                 * Calculate the size of the over-size run that arena_palloc()
                 * would need to allocate in order to guarantee the alignment.
                 */
                if (ceil_size >= alignment)
                        run_size = ceil_size + alignment - PAGE_SIZE;
                else {
                        /*
                         * It is possible that (alignment << 1) will cause
                         * overflow, but it doesn't matter because we also
                         * subtract PAGE_SIZE, which in the case of overflow
                         * leaves us with a very large run_size.  That causes
                         * the first conditional below to fail, which means
                         * that the bogus run_size value never gets used for
                         * anything important.
                         */
                        run_size = (alignment << 1) - PAGE_SIZE;
                }

                if (run_size <= arena_maxclass) {
                        ret = arena_palloc(choose_arena(), alignment, ceil_size,
                            run_size);
                } else if (alignment <= chunksize)
                        ret = huge_malloc(ceil_size, false);
                else
                        ret = huge_palloc(alignment, ceil_size);
        }

        assert(((uintptr_t)ret & (alignment - 1)) == 0);
        return (ret);
}

static bool
arena_is_large(const void *ptr)
{
        arena_chunk_t *chunk;
        size_t pageind, mapbits;

        assert(ptr != NULL);
        assert(CHUNK_ADDR2BASE(ptr) != ptr);

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
        pageind = (((uintptr_t)ptr - (uintptr_t)chunk) >> PAGE_SHIFT);
        mapbits = chunk->map[pageind].bits;
        assert((mapbits & CHUNK_MAP_ALLOCATED) != 0);
        return ((mapbits & CHUNK_MAP_LARGE) != 0);
}

/* Return the size of the allocation pointed to by ptr. */
static size_t
arena_salloc(const void *ptr)
{
        size_t ret;
        arena_chunk_t *chunk;
        size_t pageind, mapbits;

        assert(ptr != NULL);
        assert(CHUNK_ADDR2BASE(ptr) != ptr);

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
        pageind = (((uintptr_t)ptr - (uintptr_t)chunk) >> PAGE_SHIFT);
        mapbits = chunk->map[pageind].bits;
        assert((mapbits & CHUNK_MAP_ALLOCATED) != 0);
        if ((mapbits & CHUNK_MAP_LARGE) == 0) {
                arena_run_t *run = (arena_run_t *)((uintptr_t)chunk +
                    (uintptr_t)((pageind - ((mapbits & CHUNK_MAP_PG_MASK) >>
                    CHUNK_MAP_PG_SHIFT)) << PAGE_SHIFT));
                assert(run->magic == ARENA_RUN_MAGIC);
                ret = run->bin->reg_size;
        } else {
                ret = mapbits & ~PAGE_MASK;
                assert(ret != 0);
        }

        return (ret);
}

static inline size_t
isalloc(const void *ptr)
{
        size_t ret;
        arena_chunk_t *chunk;

        assert(ptr != NULL);

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
        if (chunk != ptr) {
                /* Region. */
                assert(chunk->arena->magic == ARENA_MAGIC);

                ret = arena_salloc(ptr);
        } else {
                extent_node_t *node, key;

                /* Chunk (huge allocation). */

                malloc_mutex_lock(&huge_mtx);

                /* Extract from tree of huge allocations. */
                key.addr = __DECONST(void *, ptr);
                node = extent_tree_ad_search(&huge, &key);
                assert(node != NULL);

                ret = node->size;

                malloc_mutex_unlock(&huge_mtx);
        }

        return (ret);
}

static inline void
arena_dalloc_bin(arena_t *arena, arena_chunk_t *chunk, void *ptr,
    arena_chunk_map_t *mapelm)
{
        size_t pageind;
        arena_run_t *run;
        arena_bin_t *bin;
        size_t size;

        pageind = (((uintptr_t)ptr - (uintptr_t)chunk) >> PAGE_SHIFT);
        run = (arena_run_t *)((uintptr_t)chunk + (uintptr_t)((pageind -
            ((mapelm->bits & CHUNK_MAP_PG_MASK) >> CHUNK_MAP_PG_SHIFT)) <<
            PAGE_SHIFT));
        assert(run->magic == ARENA_RUN_MAGIC);
        bin = run->bin;
        size = bin->reg_size;

        if (opt_junk)
                memset(ptr, 0x5a, size);

        arena_run_reg_dalloc(run, bin, ptr, size);
        run->nfree++;

        if (run->nfree == bin->nregs)
                arena_dalloc_bin_run(arena, chunk, run, bin);
        else if (run->nfree == 1 && run != bin->runcur) {
                /*
                 * Make sure that bin->runcur always refers to the lowest
                 * non-full run, if one exists.
                 */
                if (bin->runcur == NULL)
                        bin->runcur = run;
                else if ((uintptr_t)run < (uintptr_t)bin->runcur) {
                        /* Switch runcur. */
                        if (bin->runcur->nfree > 0) {
                                arena_chunk_t *runcur_chunk =
                                    CHUNK_ADDR2BASE(bin->runcur);
                                size_t runcur_pageind =
                                    (((uintptr_t)bin->runcur -
                                    (uintptr_t)runcur_chunk)) >> PAGE_SHIFT;
                                arena_chunk_map_t *runcur_mapelm =
                                    &runcur_chunk->map[runcur_pageind];

                                /* Insert runcur. */
                                arena_run_tree_insert(&bin->runs,
                                    runcur_mapelm);
                        }
                        bin->runcur = run;
                } else {
                        size_t run_pageind = (((uintptr_t)run -
                            (uintptr_t)chunk)) >> PAGE_SHIFT;
                        arena_chunk_map_t *run_mapelm =
                            &chunk->map[run_pageind];

                        assert(arena_run_tree_search(&bin->runs, run_mapelm) ==
                            NULL);
                        arena_run_tree_insert(&bin->runs, run_mapelm);
                }
        }

#ifdef MALLOC_STATS
        if (size <= small_maxclass) {
                arena->stats.allocated_small -= size;
                arena->stats.ndalloc_small++;
        } else {
                arena->stats.allocated_medium -= size;
                arena->stats.ndalloc_medium++;
        }
#endif
}

static void
arena_dalloc_bin_run(arena_t *arena, arena_chunk_t *chunk, arena_run_t *run,
    arena_bin_t *bin)
{
        size_t run_ind;

        /* Deallocate run. */
        if (run == bin->runcur)
                bin->runcur = NULL;
        else if (bin->nregs != 1) {
                size_t run_pageind = (((uintptr_t)run -
                    (uintptr_t)chunk)) >> PAGE_SHIFT;
                arena_chunk_map_t *run_mapelm =
                    &chunk->map[run_pageind];
                /*
                 * This block's conditional is necessary because if the
                 * run only contains one region, then it never gets
                 * inserted into the non-full runs tree.
                 */
                arena_run_tree_remove(&bin->runs, run_mapelm);
        }
        /*
         * Mark the first page as dirty.  The dirty bit for every other page in
         * the run is already properly set, which means we can call
         * arena_run_dalloc(..., false), thus potentially avoiding the needless
         * creation of many dirty pages.
         */
        run_ind = (size_t)(((uintptr_t)run - (uintptr_t)chunk) >> PAGE_SHIFT);
        assert((chunk->map[run_ind].bits & CHUNK_MAP_DIRTY) == 0);
        chunk->map[run_ind].bits |= CHUNK_MAP_DIRTY;
        chunk->ndirty++;
        arena->ndirty++;

#ifdef MALLOC_DEBUG
        run->magic = 0;
#endif
        arena_run_dalloc(arena, run, false);
#ifdef MALLOC_STATS
        bin->stats.curruns--;
#endif

        if (chunk->dirtied == false) {
                arena_chunk_tree_dirty_insert(&arena->chunks_dirty, chunk);
                chunk->dirtied = true;
        }
        /* Enforce opt_lg_dirty_mult. */
        if (opt_lg_dirty_mult >= 0 && (arena->nactive >> opt_lg_dirty_mult) <
            arena->ndirty)
                arena_purge(arena);
}

#ifdef MALLOC_STATS
static void
arena_stats_print(arena_t *arena)
{

        malloc_printf("dirty pages: %zu:%zu active:dirty, %"PRIu64" sweep%s,"
            " %"PRIu64" madvise%s, %"PRIu64" purged\n",
            arena->nactive, arena->ndirty,
            arena->stats.npurge, arena->stats.npurge == 1 ? "" : "s",
            arena->stats.nmadvise, arena->stats.nmadvise == 1 ? "" : "s",
            arena->stats.purged);

        malloc_printf("            allocated      nmalloc      ndalloc\n");
        malloc_printf("small:   %12zu %12"PRIu64" %12"PRIu64"\n",
            arena->stats.allocated_small, arena->stats.nmalloc_small,
            arena->stats.ndalloc_small);
        malloc_printf("medium:  %12zu %12"PRIu64" %12"PRIu64"\n",
            arena->stats.allocated_medium, arena->stats.nmalloc_medium,
            arena->stats.ndalloc_medium);
        malloc_printf("large:   %12zu %12"PRIu64" %12"PRIu64"\n",
            arena->stats.allocated_large, arena->stats.nmalloc_large,
            arena->stats.ndalloc_large);
        malloc_printf("total:   %12zu %12"PRIu64" %12"PRIu64"\n",
            arena->stats.allocated_small + arena->stats.allocated_medium +
            arena->stats.allocated_large, arena->stats.nmalloc_small +
            arena->stats.nmalloc_medium + arena->stats.nmalloc_large,
            arena->stats.ndalloc_small + arena->stats.ndalloc_medium +
            arena->stats.ndalloc_large);
        malloc_printf("mapped:  %12zu\n", arena->stats.mapped);

        if (arena->stats.nmalloc_small + arena->stats.nmalloc_medium > 0) {
                unsigned i, gap_start;
#ifdef MALLOC_TCACHE
                malloc_printf("bins:     bin    size regs pgs  requests    "
                    "nfills  nflushes   newruns    reruns maxruns curruns\n");
#else
                malloc_printf("bins:     bin    size regs pgs  requests   "
                    "newruns    reruns maxruns curruns\n");
#endif
                for (i = 0, gap_start = UINT_MAX; i < nbins; i++) {
                        if (arena->bins[i].stats.nruns == 0) {
                                if (gap_start == UINT_MAX)
                                        gap_start = i;
                        } else {
                                if (gap_start != UINT_MAX) {
                                        if (i > gap_start + 1) {
                                                /*
                                                 * Gap of more than one size
                                                 * class.
                                                 */
                                                malloc_printf("[%u..%u]\n",
                                                    gap_start, i - 1);
                                        } else {
                                                /* Gap of one size class. */
                                                malloc_printf("[%u]\n",
                                                    gap_start);
                                        }
                                        gap_start = UINT_MAX;
                                }
                                malloc_printf(
                                    "%13u %1s %5u %4u %3u %9"PRIu64" %9"PRIu64
#ifdef MALLOC_TCACHE
                                    " %9"PRIu64" %9"PRIu64
#endif
                                    " %9"PRIu64" %7zu %7zu\n",
                                    i,
                                    i < ntbins ? "T" : i < ntbins + nqbins ?
                                    "Q" : i < ntbins + nqbins + ncbins ? "C" :
                                    i < ntbins + nqbins + ncbins + nsbins ? "S"
                                    : "M",
                                    arena->bins[i].reg_size,
                                    arena->bins[i].nregs,
                                    arena->bins[i].run_size >> PAGE_SHIFT,
                                    arena->bins[i].stats.nrequests,
#ifdef MALLOC_TCACHE
                                    arena->bins[i].stats.nfills,
                                    arena->bins[i].stats.nflushes,
#endif
                                    arena->bins[i].stats.nruns,
                                    arena->bins[i].stats.reruns,
                                    arena->bins[i].stats.highruns,
                                    arena->bins[i].stats.curruns);
                        }
                }
                if (gap_start != UINT_MAX) {
                        if (i > gap_start + 1) {
                                /* Gap of more than one size class. */
                                malloc_printf("[%u..%u]\n", gap_start, i - 1);
                        } else {
                                /* Gap of one size class. */
                                malloc_printf("[%u]\n", gap_start);
                        }
                }
        }

        if (arena->stats.nmalloc_large > 0) {
                size_t i;
                ssize_t gap_start;
                size_t nlclasses = (chunksize - PAGE_SIZE) >> PAGE_SHIFT;

                malloc_printf(
                    "large:   size pages nrequests   maxruns   curruns\n");

                for (i = 0, gap_start = -1; i < nlclasses; i++) {
                        if (arena->stats.lstats[i].nrequests == 0) {
                                if (gap_start == -1)
                                        gap_start = i;
                        } else {
                                if (gap_start != -1) {
                                        malloc_printf("[%zu]\n", i - gap_start);
                                        gap_start = -1;
                                }
                                malloc_printf(
                                    "%13zu %5zu %9"PRIu64" %9zu %9zu\n",
                                    (i+1) << PAGE_SHIFT, i+1,
                                    arena->stats.lstats[i].nrequests,
                                    arena->stats.lstats[i].highruns,
                                    arena->stats.lstats[i].curruns);
                        }
                }
                if (gap_start != -1)
                        malloc_printf("[%zu]\n", i - gap_start);
        }
}
#endif

static void
stats_print_atexit(void)
{

#if (defined(MALLOC_TCACHE) && defined(MALLOC_STATS))
        unsigned i;

        /*
         * Merge stats from extant threads.  This is racy, since individual
         * threads do not lock when recording tcache stats events.  As a
         * consequence, the final stats may be slightly out of date by the time
         * they are reported, if other threads continue to allocate.
         */
        for (i = 0; i < narenas; i++) {
                arena_t *arena = arenas[i];
                if (arena != NULL) {
                        tcache_t *tcache;

                        malloc_spin_lock(&arena->lock);
                        ql_foreach(tcache, &arena->tcache_ql, link) {
                                tcache_stats_merge(tcache, arena);
                        }
                        malloc_spin_unlock(&arena->lock);
                }
        }
#endif
        malloc_stats_print();
}

#ifdef MALLOC_TCACHE
static void
tcache_bin_flush(tcache_bin_t *tbin, size_t binind, unsigned rem)
{
        arena_chunk_t *chunk;
        arena_t *arena;
        void *ptr;
        unsigned i, ndeferred, ncached;

        for (ndeferred = tbin->ncached - rem; ndeferred > 0;) {
                ncached = ndeferred;
                /* Lock the arena associated with the first object. */
                chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(tbin->slots[0]);
                arena = chunk->arena;
                malloc_spin_lock(&arena->lock);
                /* Deallocate every object that belongs to the locked arena. */
                for (i = ndeferred = 0; i < ncached; i++) {
                        ptr = tbin->slots[i];
                        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
                        if (chunk->arena == arena) {
                                size_t pageind = (((uintptr_t)ptr -
                                    (uintptr_t)chunk) >> PAGE_SHIFT);
                                arena_chunk_map_t *mapelm =
                                    &chunk->map[pageind];
                                arena_dalloc_bin(arena, chunk, ptr, mapelm);
                        } else {
                                /*
                                 * This object was allocated via a different
                                 * arena than the one that is currently locked.
                                 * Stash the object, so that it can be handled
                                 * in a future pass.
                                 */
                                tbin->slots[ndeferred] = ptr;
                                ndeferred++;
                        }
                }
#ifdef MALLOC_STATS
                arena->bins[binind].stats.nflushes++;
                {
                        arena_bin_t *bin = &arena->bins[binind];
                        bin->stats.nrequests += tbin->tstats.nrequests;
                        if (bin->reg_size <= small_maxclass) {
                                arena->stats.nmalloc_small +=
                                    tbin->tstats.nrequests;
                        } else {
                                arena->stats.nmalloc_medium +=
                                    tbin->tstats.nrequests;
                        }
                        tbin->tstats.nrequests = 0;
                }
#endif
                malloc_spin_unlock(&arena->lock);
        }

        if (rem > 0) {
                /*
                 * Shift the remaining valid pointers to the base of the slots
                 * array.
                 */
                memmove(&tbin->slots[0], &tbin->slots[tbin->ncached - rem],
                    rem * sizeof(void *));
        }
        tbin->ncached = rem;
}

static inline void
tcache_dalloc(tcache_t *tcache, void *ptr)
{
        arena_t *arena;
        arena_chunk_t *chunk;
        arena_run_t *run;
        arena_bin_t *bin;
        tcache_bin_t *tbin;
        size_t pageind, binind;
        arena_chunk_map_t *mapelm;

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
        arena = chunk->arena;
        pageind = (((uintptr_t)ptr - (uintptr_t)chunk) >> PAGE_SHIFT);
        mapelm = &chunk->map[pageind];
        run = (arena_run_t *)((uintptr_t)chunk + (uintptr_t)((pageind -
            ((mapelm->bits & CHUNK_MAP_PG_MASK) >> CHUNK_MAP_PG_SHIFT)) <<
            PAGE_SHIFT));
        assert(run->magic == ARENA_RUN_MAGIC);
        bin = run->bin;
        binind = ((uintptr_t)bin - (uintptr_t)&arena->bins) /
            sizeof(arena_bin_t);
        assert(binind < nbins);

        if (opt_junk)
                memset(ptr, 0x5a, arena->bins[binind].reg_size);

        tbin = tcache->tbins[binind];
        if (tbin == NULL) {
                tbin = tcache_bin_create(choose_arena());
                if (tbin == NULL) {
                        malloc_spin_lock(&arena->lock);
                        arena_dalloc_bin(arena, chunk, ptr, mapelm);
                        malloc_spin_unlock(&arena->lock);
                        return;
                }
                tcache->tbins[binind] = tbin;
        }

        if (tbin->ncached == tcache_nslots)
                tcache_bin_flush(tbin, binind, (tcache_nslots >> 1));
        assert(tbin->ncached < tcache_nslots);
        tbin->slots[tbin->ncached] = ptr;
        tbin->ncached++;
        if (tbin->ncached > tbin->high_water)
                tbin->high_water = tbin->ncached;

        tcache_event(tcache);
}
#endif

static void
arena_dalloc_large(arena_t *arena, arena_chunk_t *chunk, void *ptr)
{

        /* Large allocation. */
        malloc_spin_lock(&arena->lock);

#ifndef MALLOC_STATS
        if (opt_junk)
#endif
        {
                size_t pageind = ((uintptr_t)ptr - (uintptr_t)chunk) >>
                    PAGE_SHIFT;
                size_t size = chunk->map[pageind].bits & ~PAGE_MASK;

#ifdef MALLOC_STATS
                if (opt_junk)
#endif
                        memset(ptr, 0x5a, size);
#ifdef MALLOC_STATS
                arena->stats.ndalloc_large++;
                arena->stats.allocated_large -= size;
                arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns--;
#endif
        }

        arena_run_dalloc(arena, (arena_run_t *)ptr, true);
        malloc_spin_unlock(&arena->lock);
}

static inline void
arena_dalloc(arena_t *arena, arena_chunk_t *chunk, void *ptr)
{
        size_t pageind;
        arena_chunk_map_t *mapelm;

        assert(arena != NULL);
        assert(arena->magic == ARENA_MAGIC);
        assert(chunk->arena == arena);
        assert(ptr != NULL);
        assert(CHUNK_ADDR2BASE(ptr) != ptr);

        pageind = (((uintptr_t)ptr - (uintptr_t)chunk) >> PAGE_SHIFT);
        mapelm = &chunk->map[pageind];
        assert((mapelm->bits & CHUNK_MAP_ALLOCATED) != 0);
        if ((mapelm->bits & CHUNK_MAP_LARGE) == 0) {
                /* Small allocation. */
#ifdef MALLOC_TCACHE
                if (__isthreaded && tcache_nslots) {
                        tcache_t *tcache = tcache_tls;
                        if ((uintptr_t)tcache > (uintptr_t)1)
                                tcache_dalloc(tcache, ptr);
                        else {
                                arena_dalloc_hard(arena, chunk, ptr, mapelm,
                                    tcache);
                        }
                } else {
#endif
                        malloc_spin_lock(&arena->lock);
                        arena_dalloc_bin(arena, chunk, ptr, mapelm);
                        malloc_spin_unlock(&arena->lock);
#ifdef MALLOC_TCACHE
                }
#endif
        } else
                arena_dalloc_large(arena, chunk, ptr);
}

#ifdef MALLOC_TCACHE
static void
arena_dalloc_hard(arena_t *arena, arena_chunk_t *chunk, void *ptr,
    arena_chunk_map_t *mapelm, tcache_t *tcache)
{

        if (tcache == NULL) {
                tcache = tcache_create(arena);
                if (tcache == NULL) {
                        malloc_spin_lock(&arena->lock);
                        arena_dalloc_bin(arena, chunk, ptr, mapelm);
                        malloc_spin_unlock(&arena->lock);
                } else
                        tcache_dalloc(tcache, ptr);
        } else {
                /* This thread is currently exiting, so directly deallocate. */
                assert(tcache == (void *)(uintptr_t)1);
                malloc_spin_lock(&arena->lock);
                arena_dalloc_bin(arena, chunk, ptr, mapelm);
                malloc_spin_unlock(&arena->lock);
        }
}
#endif

static inline void
idalloc(void *ptr)
{
        arena_chunk_t *chunk;

        assert(ptr != NULL);

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
        if (chunk != ptr)
                arena_dalloc(chunk->arena, chunk, ptr);
        else
                huge_dalloc(ptr);
}

static void
arena_ralloc_large_shrink(arena_t *arena, arena_chunk_t *chunk, void *ptr,
    size_t size, size_t oldsize)
{

        assert(size < oldsize);

        /*
         * Shrink the run, and make trailing pages available for other
         * allocations.
         */
        malloc_spin_lock(&arena->lock);
        arena_run_trim_tail(arena, chunk, (arena_run_t *)ptr, oldsize, size,
            true);
#ifdef MALLOC_STATS
        arena->stats.ndalloc_large++;
        arena->stats.allocated_large -= oldsize;
        arena->stats.lstats[(oldsize >> PAGE_SHIFT) - 1].curruns--;

        arena->stats.nmalloc_large++;
        arena->stats.allocated_large += size;
        arena->stats.lstats[(size >> PAGE_SHIFT) - 1].nrequests++;
        arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns++;
        if (arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns >
            arena->stats.lstats[(size >> PAGE_SHIFT) - 1].highruns) {
                arena->stats.lstats[(size >> PAGE_SHIFT) - 1].highruns =
                    arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns;
        }
#endif
        malloc_spin_unlock(&arena->lock);
}

static bool
arena_ralloc_large_grow(arena_t *arena, arena_chunk_t *chunk, void *ptr,
    size_t size, size_t oldsize)
{
        size_t pageind = ((uintptr_t)ptr - (uintptr_t)chunk) >> PAGE_SHIFT;
        size_t npages = oldsize >> PAGE_SHIFT;

        assert(oldsize == (chunk->map[pageind].bits & ~PAGE_MASK));

        /* Try to extend the run. */
        assert(size > oldsize);
        malloc_spin_lock(&arena->lock);
        if (pageind + npages < chunk_npages && (chunk->map[pageind+npages].bits
            & CHUNK_MAP_ALLOCATED) == 0 && (chunk->map[pageind+npages].bits &
            ~PAGE_MASK) >= size - oldsize) {
                /*
                 * The next run is available and sufficiently large.  Split the
                 * following run, then merge the first part with the existing
                 * allocation.
                 */
                arena_run_split(arena, (arena_run_t *)((uintptr_t)chunk +
                    ((pageind+npages) << PAGE_SHIFT)), size - oldsize, true,
                    false);

                chunk->map[pageind].bits = size | CHUNK_MAP_LARGE |
                    CHUNK_MAP_ALLOCATED;
                chunk->map[pageind+npages].bits = CHUNK_MAP_LARGE |
                    CHUNK_MAP_ALLOCATED;

#ifdef MALLOC_STATS
                arena->stats.ndalloc_large++;
                arena->stats.allocated_large -= oldsize;
                arena->stats.lstats[(oldsize >> PAGE_SHIFT) - 1].curruns--;

                arena->stats.nmalloc_large++;
                arena->stats.allocated_large += size;
                arena->stats.lstats[(size >> PAGE_SHIFT) - 1].nrequests++;
                arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns++;
                if (arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns >
                    arena->stats.lstats[(size >> PAGE_SHIFT) - 1].highruns) {
                        arena->stats.lstats[(size >> PAGE_SHIFT) - 1].highruns =
                            arena->stats.lstats[(size >> PAGE_SHIFT) - 1].curruns;
                }
#endif
                malloc_spin_unlock(&arena->lock);
                return (false);
        }
        malloc_spin_unlock(&arena->lock);

        return (true);
}

/*
 * Try to resize a large allocation, in order to avoid copying.  This will
 * always fail if growing an object, and the following run is already in use.
 */
static bool
arena_ralloc_large(void *ptr, size_t size, size_t oldsize)
{
        size_t psize;

        psize = PAGE_CEILING(size);
        if (psize == oldsize) {
                /* Same size class. */
                if (opt_junk && size < oldsize) {
                        memset((void *)((uintptr_t)ptr + size), 0x5a, oldsize -
                            size);
                }
                return (false);
        } else {
                arena_chunk_t *chunk;
                arena_t *arena;

                chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
                arena = chunk->arena;
                assert(arena->magic == ARENA_MAGIC);

                if (psize < oldsize) {
                        /* Fill before shrinking in order avoid a race. */
                        if (opt_junk) {
                                memset((void *)((uintptr_t)ptr + size), 0x5a,
                                    oldsize - size);
                        }
                        arena_ralloc_large_shrink(arena, chunk, ptr, psize,
                            oldsize);
                        return (false);
                } else {
                        bool ret = arena_ralloc_large_grow(arena, chunk, ptr,
                            psize, oldsize);
                        if (ret == false && opt_zero) {
                                memset((void *)((uintptr_t)ptr + oldsize), 0,
                                    size - oldsize);
                        }
                        return (ret);
                }
        }
}

static void *
arena_ralloc(void *ptr, size_t size, size_t oldsize)
{
        void *ret;
        size_t copysize;

        /*
         * Try to avoid moving the allocation.
         *
         * posix_memalign() can cause allocation of "large" objects that are
         * smaller than bin_maxclass (in order to meet alignment requirements).
         * Therefore, do not assume that (oldsize <= bin_maxclass) indicates
         * ptr refers to a bin-allocated object.
         */
        if (oldsize <= arena_maxclass) {
                if (arena_is_large(ptr) == false ) {
                        if (size <= small_maxclass) {
                                if (oldsize <= small_maxclass &&
                                    small_size2bin[size] ==
                                    small_size2bin[oldsize])
                                        goto IN_PLACE;
                        } else if (size <= bin_maxclass) {
                                if (small_maxclass < oldsize && oldsize <=
                                    bin_maxclass && MEDIUM_CEILING(size) ==
                                    MEDIUM_CEILING(oldsize))
                                        goto IN_PLACE;
                        }
                } else {
                        assert(size <= arena_maxclass);
                        if (size > bin_maxclass) {
                                if (arena_ralloc_large(ptr, size, oldsize) ==
                                    false)
                                        return (ptr);
                        }
                }
        }

        /* Try to avoid moving the allocation. */
        if (size <= small_maxclass) {
                if (oldsize <= small_maxclass && small_size2bin[size] ==
                    small_size2bin[oldsize])
                        goto IN_PLACE;
        } else if (size <= bin_maxclass) {
                if (small_maxclass < oldsize && oldsize <= bin_maxclass &&
                    MEDIUM_CEILING(size) == MEDIUM_CEILING(oldsize))
                        goto IN_PLACE;
        } else {
                if (bin_maxclass < oldsize && oldsize <= arena_maxclass) {
                        assert(size > bin_maxclass);
                        if (arena_ralloc_large(ptr, size, oldsize) == false)
                                return (ptr);
                }
        }

        /*
         * If we get here, then size and oldsize are different enough that we
         * need to move the object.  In that case, fall back to allocating new
         * space and copying.
         */
        ret = arena_malloc(size, false);
        if (ret == NULL)
                return (NULL);

        /* Junk/zero-filling were already done by arena_malloc(). */
        copysize = (size < oldsize) ? size : oldsize;
        memcpy(ret, ptr, copysize);
        idalloc(ptr);
        return (ret);
IN_PLACE:
        if (opt_junk && size < oldsize)
                memset((void *)((uintptr_t)ptr + size), 0x5a, oldsize - size);
        else if (opt_zero && size > oldsize)
                memset((void *)((uintptr_t)ptr + oldsize), 0, size - oldsize);
        return (ptr);
}

static inline void *
iralloc(void *ptr, size_t size)
{
        size_t oldsize;

        assert(ptr != NULL);
        assert(size != 0);

        oldsize = isalloc(ptr);

        if (size <= arena_maxclass)
                return (arena_ralloc(ptr, size, oldsize));
        else
                return (huge_ralloc(ptr, size, oldsize));
}

static bool
arena_new(arena_t *arena, unsigned ind)
{
        unsigned i;
        arena_bin_t *bin;
        size_t prev_run_size;

        if (malloc_spin_init(&arena->lock))
                return (true);

#ifdef MALLOC_STATS
        memset(&arena->stats, 0, sizeof(arena_stats_t));
        arena->stats.lstats = (malloc_large_stats_t *)base_alloc(
            sizeof(malloc_large_stats_t) * ((chunksize - PAGE_SIZE) >>
                PAGE_SHIFT));
        if (arena->stats.lstats == NULL)
                return (true);
        memset(arena->stats.lstats, 0, sizeof(malloc_large_stats_t) *
            ((chunksize - PAGE_SIZE) >> PAGE_SHIFT));
#  ifdef MALLOC_TCACHE
        ql_new(&arena->tcache_ql);
#  endif
#endif

        /* Initialize chunks. */
        arena_chunk_tree_dirty_new(&arena->chunks_dirty);
        arena->spare = NULL;

        arena->nactive = 0;
        arena->ndirty = 0;

        arena_avail_tree_new(&arena->runs_avail);

        /* Initialize bins. */
        prev_run_size = PAGE_SIZE;

        i = 0;
#ifdef MALLOC_TINY
        /* (2^n)-spaced tiny bins. */
        for (; i < ntbins; i++) {
                bin = &arena->bins[i];
                bin->runcur = NULL;
                arena_run_tree_new(&bin->runs);

                bin->reg_size = (1U << (LG_TINY_MIN + i));

                prev_run_size = arena_bin_run_size_calc(bin, prev_run_size);

#ifdef MALLOC_STATS
                memset(&bin->stats, 0, sizeof(malloc_bin_stats_t));
#endif
        }
#endif

        /* Quantum-spaced bins. */
        for (; i < ntbins + nqbins; i++) {
                bin = &arena->bins[i];
                bin->runcur = NULL;
                arena_run_tree_new(&bin->runs);

                bin->reg_size = (i - ntbins + 1) << LG_QUANTUM;

                prev_run_size = arena_bin_run_size_calc(bin, prev_run_size);

#ifdef MALLOC_STATS
                memset(&bin->stats, 0, sizeof(malloc_bin_stats_t));
#endif
        }

        /* Cacheline-spaced bins. */
        for (; i < ntbins + nqbins + ncbins; i++) {
                bin = &arena->bins[i];
                bin->runcur = NULL;
                arena_run_tree_new(&bin->runs);

                bin->reg_size = cspace_min + ((i - (ntbins + nqbins)) <<
                    LG_CACHELINE);

                prev_run_size = arena_bin_run_size_calc(bin, prev_run_size);

#ifdef MALLOC_STATS
                memset(&bin->stats, 0, sizeof(malloc_bin_stats_t));
#endif
        }

        /* Subpage-spaced bins. */
        for (; i < ntbins + nqbins + ncbins + nsbins; i++) {
                bin = &arena->bins[i];
                bin->runcur = NULL;
                arena_run_tree_new(&bin->runs);

                bin->reg_size = sspace_min + ((i - (ntbins + nqbins + ncbins))
                    << LG_SUBPAGE);

                prev_run_size = arena_bin_run_size_calc(bin, prev_run_size);

#ifdef MALLOC_STATS
                memset(&bin->stats, 0, sizeof(malloc_bin_stats_t));
#endif
        }

        /* Medium bins. */
        for (; i < nbins; i++) {
                bin = &arena->bins[i];
                bin->runcur = NULL;
                arena_run_tree_new(&bin->runs);

                bin->reg_size = medium_min + ((i - (ntbins + nqbins + ncbins +
                    nsbins)) << lg_mspace);

                prev_run_size = arena_bin_run_size_calc(bin, prev_run_size);

#ifdef MALLOC_STATS
                memset(&bin->stats, 0, sizeof(malloc_bin_stats_t));
#endif
        }

#ifdef MALLOC_DEBUG
        arena->magic = ARENA_MAGIC;
#endif

        return (false);
}

/* Create a new arena and insert it into the arenas array at index ind. */
static arena_t *
arenas_extend(unsigned ind)
{
        arena_t *ret;

        /* Allocate enough space for trailing bins. */
        ret = (arena_t *)base_alloc(sizeof(arena_t)
            + (sizeof(arena_bin_t) * (nbins - 1)));
        if (ret != NULL && arena_new(ret, ind) == false) {
                arenas[ind] = ret;
                return (ret);
        }
        /* Only reached if there is an OOM error. */

        /*
         * OOM here is quite inconvenient to propagate, since dealing with it
         * would require a check for failure in the fast path.  Instead, punt
         * by using arenas[0].  In practice, this is an extremely unlikely
         * failure.
         */
        _malloc_message(_getprogname(),
            ": (malloc) Error initializing arena\n", "", "");
        if (opt_abort)
                abort();

        return (arenas[0]);
}

#ifdef MALLOC_TCACHE
static tcache_bin_t *
tcache_bin_create(arena_t *arena)
{
        tcache_bin_t *ret;
        size_t tsize;

        tsize = sizeof(tcache_bin_t) + (sizeof(void *) * (tcache_nslots - 1));
        if (tsize <= small_maxclass)
                ret = (tcache_bin_t *)arena_malloc_small(arena, tsize, false);
        else if (tsize <= bin_maxclass)
                ret = (tcache_bin_t *)arena_malloc_medium(arena, tsize, false);
        else
                ret = (tcache_bin_t *)imalloc(tsize);
        if (ret == NULL)
                return (NULL);
#ifdef MALLOC_STATS
        memset(&ret->tstats, 0, sizeof(tcache_bin_stats_t));
#endif
        ret->low_water = 0;
        ret->high_water = 0;
        ret->ncached = 0;

        return (ret);
}

static void
tcache_bin_destroy(tcache_t *tcache, tcache_bin_t *tbin, unsigned binind)
{
        arena_t *arena;
        arena_chunk_t *chunk;
        size_t pageind, tsize;
        arena_chunk_map_t *mapelm;

        chunk = CHUNK_ADDR2BASE(tbin);
        arena = chunk->arena;
        pageind = (((uintptr_t)tbin - (uintptr_t)chunk) >> PAGE_SHIFT);
        mapelm = &chunk->map[pageind];

#ifdef MALLOC_STATS
        if (tbin->tstats.nrequests != 0) {
                arena_t *arena = tcache->arena;
                arena_bin_t *bin = &arena->bins[binind];
                malloc_spin_lock(&arena->lock);
                bin->stats.nrequests += tbin->tstats.nrequests;
                if (bin->reg_size <= small_maxclass)
                        arena->stats.nmalloc_small += tbin->tstats.nrequests;
                else
                        arena->stats.nmalloc_medium += tbin->tstats.nrequests;
                malloc_spin_unlock(&arena->lock);
        }
#endif

        assert(tbin->ncached == 0);
        tsize = sizeof(tcache_bin_t) + (sizeof(void *) * (tcache_nslots - 1));
        if (tsize <= bin_maxclass) {
                malloc_spin_lock(&arena->lock);
                arena_dalloc_bin(arena, chunk, tbin, mapelm);
                malloc_spin_unlock(&arena->lock);
        } else
                idalloc(tbin);
}

#ifdef MALLOC_STATS
static void
tcache_stats_merge(tcache_t *tcache, arena_t *arena)
{
        unsigned i;

        /* Merge and reset tcache stats. */
        for (i = 0; i < mbin0; i++) {
                arena_bin_t *bin = &arena->bins[i];
                tcache_bin_t *tbin = tcache->tbins[i];
                if (tbin != NULL) {
                        bin->stats.nrequests += tbin->tstats.nrequests;
                        arena->stats.nmalloc_small += tbin->tstats.nrequests;
                        tbin->tstats.nrequests = 0;
                }
        }
        for (; i < nbins; i++) {
                arena_bin_t *bin = &arena->bins[i];
                tcache_bin_t *tbin = tcache->tbins[i];
                if (tbin != NULL) {
                        bin->stats.nrequests += tbin->tstats.nrequests;
                        arena->stats.nmalloc_medium += tbin->tstats.nrequests;
                        tbin->tstats.nrequests = 0;
                }
        }
}
#endif

static tcache_t *
tcache_create(arena_t *arena)
{
        tcache_t *tcache;

        if (sizeof(tcache_t) + (sizeof(tcache_bin_t *) * (nbins - 1)) <=
            small_maxclass) {
                tcache = (tcache_t *)arena_malloc_small(arena, sizeof(tcache_t)
                    + (sizeof(tcache_bin_t *) * (nbins - 1)), true);
        } else if (sizeof(tcache_t) + (sizeof(tcache_bin_t *) * (nbins - 1)) <=
            bin_maxclass) {
                tcache = (tcache_t *)arena_malloc_medium(arena, sizeof(tcache_t)
                    + (sizeof(tcache_bin_t *) * (nbins - 1)), true);
        } else {
                tcache = (tcache_t *)icalloc(sizeof(tcache_t) +
                    (sizeof(tcache_bin_t *) * (nbins - 1)));
        }

        if (tcache == NULL)
                return (NULL);

#ifdef MALLOC_STATS
        /* Link into list of extant tcaches. */
        malloc_spin_lock(&arena->lock);
        ql_elm_new(tcache, link);
        ql_tail_insert(&arena->tcache_ql, tcache, link);
        malloc_spin_unlock(&arena->lock);
#endif

        tcache->arena = arena;

        tcache_tls = tcache;

        return (tcache);
}

static void
tcache_destroy(tcache_t *tcache)
{
        unsigned i;

#ifdef MALLOC_STATS
        /* Unlink from list of extant tcaches. */
        malloc_spin_lock(&tcache->arena->lock);
        ql_remove(&tcache->arena->tcache_ql, tcache, link);
        tcache_stats_merge(tcache, tcache->arena);
        malloc_spin_unlock(&tcache->arena->lock);
#endif

        for (i = 0; i < nbins; i++) {
                tcache_bin_t *tbin = tcache->tbins[i];
                if (tbin != NULL) {
                        tcache_bin_flush(tbin, i, 0);
                        tcache_bin_destroy(tcache, tbin, i);
                }
        }

        if (arena_salloc(tcache) <= bin_maxclass) {
                arena_chunk_t *chunk = CHUNK_ADDR2BASE(tcache);
                arena_t *arena = chunk->arena;
                size_t pageind = (((uintptr_t)tcache - (uintptr_t)chunk) >>
                    PAGE_SHIFT);
                arena_chunk_map_t *mapelm = &chunk->map[pageind];

                malloc_spin_lock(&arena->lock);
                arena_dalloc_bin(arena, chunk, tcache, mapelm);
                malloc_spin_unlock(&arena->lock);
        } else
                idalloc(tcache);
}
#endif

/*
 * End arena.
 */
/******************************************************************************/
/*
 * Begin general internal functions.
 */

static void *
huge_malloc(size_t size, bool zero)
{
        void *ret;
        size_t csize;
        extent_node_t *node;

        /* Allocate one or more contiguous chunks for this request. */

        csize = CHUNK_CEILING(size);
        if (csize == 0) {
                /* size is large enough to cause size_t wrap-around. */
                return (NULL);
        }

        /* Allocate an extent node with which to track the chunk. */
        node = base_node_alloc();
        if (node == NULL)
                return (NULL);

        ret = chunk_alloc(csize, &zero);
        if (ret == NULL) {
                base_node_dealloc(node);
                return (NULL);
        }

        /* Insert node into huge. */
        node->addr = ret;
        node->size = csize;

        malloc_mutex_lock(&huge_mtx);
        extent_tree_ad_insert(&huge, node);
#ifdef MALLOC_STATS
        huge_nmalloc++;
        huge_allocated += csize;
#endif
        malloc_mutex_unlock(&huge_mtx);

        if (zero == false) {
                if (opt_junk)
                        memset(ret, 0xa5, csize);
                else if (opt_zero)
                        memset(ret, 0, csize);
        }

        return (ret);
}

/* Only handles large allocations that require more than chunk alignment. */
static void *
huge_palloc(size_t alignment, size_t size)
{
        void *ret;
        size_t alloc_size, chunk_size, offset;
        extent_node_t *node;
        bool zero;

        /*
         * This allocation requires alignment that is even larger than chunk
         * alignment.  This means that huge_malloc() isn't good enough.
         *
         * Allocate almost twice as many chunks as are demanded by the size or
         * alignment, in order to assure the alignment can be achieved, then
         * unmap leading and trailing chunks.
         */
        assert(alignment >= chunksize);

        chunk_size = CHUNK_CEILING(size);

        if (size >= alignment)
                alloc_size = chunk_size + alignment - chunksize;
        else
                alloc_size = (alignment << 1) - chunksize;

        /* Allocate an extent node with which to track the chunk. */
        node = base_node_alloc();
        if (node == NULL)
                return (NULL);

        zero = false;
        ret = chunk_alloc(alloc_size, &zero);
        if (ret == NULL) {
                base_node_dealloc(node);
                return (NULL);
        }

        offset = (uintptr_t)ret & (alignment - 1);
        assert((offset & chunksize_mask) == 0);
        assert(offset < alloc_size);
        if (offset == 0) {
                /* Trim trailing space. */
                chunk_dealloc((void *)((uintptr_t)ret + chunk_size), alloc_size
                    - chunk_size);
        } else {
                size_t trailsize;

                /* Trim leading space. */
                chunk_dealloc(ret, alignment - offset);

                ret = (void *)((uintptr_t)ret + (alignment - offset));

                trailsize = alloc_size - (alignment - offset) - chunk_size;
                if (trailsize != 0) {
                    /* Trim trailing space. */
                    assert(trailsize < alloc_size);
                    chunk_dealloc((void *)((uintptr_t)ret + chunk_size),
                        trailsize);
                }
        }

        /* Insert node into huge. */
        node->addr = ret;
        node->size = chunk_size;

        malloc_mutex_lock(&huge_mtx);
        extent_tree_ad_insert(&huge, node);
#ifdef MALLOC_STATS
        huge_nmalloc++;
        huge_allocated += chunk_size;
#endif
        malloc_mutex_unlock(&huge_mtx);

        if (opt_junk)
                memset(ret, 0xa5, chunk_size);
        else if (opt_zero)
                memset(ret, 0, chunk_size);

        return (ret);
}

static void *
huge_ralloc(void *ptr, size_t size, size_t oldsize)
{
        void *ret;
        size_t copysize;

        /* Avoid moving the allocation if the size class would not change. */
        if (oldsize > arena_maxclass &&
            CHUNK_CEILING(size) == CHUNK_CEILING(oldsize)) {
                if (opt_junk && size < oldsize) {
                        memset((void *)((uintptr_t)ptr + size), 0x5a, oldsize
                            - size);
                } else if (opt_zero && size > oldsize) {
                        memset((void *)((uintptr_t)ptr + oldsize), 0, size
                            - oldsize);
                }
                return (ptr);
        }

        /*
         * If we get here, then size and oldsize are different enough that we
         * need to use a different size class.  In that case, fall back to
         * allocating new space and copying.
         */
        ret = huge_malloc(size, false);
        if (ret == NULL)
                return (NULL);

        copysize = (size < oldsize) ? size : oldsize;
        memcpy(ret, ptr, copysize);
        idalloc(ptr);
        return (ret);
}

static void
huge_dalloc(void *ptr)
{
        extent_node_t *node, key;

        malloc_mutex_lock(&huge_mtx);

        /* Extract from tree of huge allocations. */
        key.addr = ptr;
        node = extent_tree_ad_search(&huge, &key);
        assert(node != NULL);
        assert(node->addr == ptr);
        extent_tree_ad_remove(&huge, node);

#ifdef MALLOC_STATS
        huge_ndalloc++;
        huge_allocated -= node->size;
#endif

        malloc_mutex_unlock(&huge_mtx);

        /* Unmap chunk. */
#ifdef MALLOC_DSS
        if (opt_dss && opt_junk)
                memset(node->addr, 0x5a, node->size);
#endif
        chunk_dealloc(node->addr, node->size);

        base_node_dealloc(node);
}

static void
malloc_stats_print(void)
{
        char s[UMAX2S_BUFSIZE];

        _malloc_message("___ Begin malloc statistics ___\n", "", "", "");
        _malloc_message("Assertions ",
#ifdef NDEBUG
            "disabled",
#else
            "enabled",
#endif
            "\n", "");
        _malloc_message("Boolean MALLOC_OPTIONS: ", opt_abort ? "A" : "a", "", "");
#ifdef MALLOC_DSS
        _malloc_message(opt_dss ? "D" : "d", "", "", "");
#endif
        _malloc_message(opt_junk ? "J" : "j", "", "", "");
#ifdef MALLOC_DSS
        _malloc_message(opt_mmap ? "M" : "m", "", "", "");
#endif
        _malloc_message("P", "", "", "");
        _malloc_message(opt_utrace ? "U" : "u", "", "", "");
        _malloc_message(opt_sysv ? "V" : "v", "", "", "");
        _malloc_message(opt_xmalloc ? "X" : "x", "", "", "");
        _malloc_message(opt_zero ? "Z" : "z", "", "", "");
        _malloc_message("\n", "", "", "");

        _malloc_message("CPUs: ", umax2s(ncpus, 10, s), "\n", "");
        _malloc_message("Max arenas: ", umax2s(narenas, 10, s), "\n", "");
        _malloc_message("Pointer size: ", umax2s(sizeof(void *), 10, s), "\n", "");
        _malloc_message("Quantum size: ", umax2s(QUANTUM, 10, s), "\n", "");
        _malloc_message("Cacheline size (assumed): ",
            umax2s(CACHELINE, 10, s), "\n", "");
        _malloc_message("Subpage spacing: ", umax2s(SUBPAGE, 10, s), "\n", "");
        _malloc_message("Medium spacing: ", umax2s((1U << lg_mspace), 10, s), "\n",
            "");
#ifdef MALLOC_TINY
        _malloc_message("Tiny 2^n-spaced sizes: [", umax2s((1U << LG_TINY_MIN), 10,
            s), "..", "");
        _malloc_message(umax2s((qspace_min >> 1), 10, s), "]\n", "", "");
#endif
        _malloc_message("Quantum-spaced sizes: [", umax2s(qspace_min, 10, s), "..",
            "");
        _malloc_message(umax2s(qspace_max, 10, s), "]\n", "", "");
        _malloc_message("Cacheline-spaced sizes: [",
            umax2s(cspace_min, 10, s), "..", "");
        _malloc_message(umax2s(cspace_max, 10, s), "]\n", "", "");
        _malloc_message("Subpage-spaced sizes: [", umax2s(sspace_min, 10, s), "..",
            "");
        _malloc_message(umax2s(sspace_max, 10, s), "]\n", "", "");
        _malloc_message("Medium sizes: [", umax2s(medium_min, 10, s), "..", "");
        _malloc_message(umax2s(medium_max, 10, s), "]\n", "", "");
        if (opt_lg_dirty_mult >= 0) {
                _malloc_message("Min active:dirty page ratio per arena: ",
                    umax2s((1U << opt_lg_dirty_mult), 10, s), ":1\n", "");
        } else {
                _malloc_message("Min active:dirty page ratio per arena: N/A\n", "",
                    "", "");
        }
#ifdef MALLOC_TCACHE
        _malloc_message("Thread cache slots per size class: ",
            tcache_nslots ? umax2s(tcache_nslots, 10, s) : "N/A", "\n", "");
        _malloc_message("Thread cache GC sweep interval: ",
            (tcache_nslots && tcache_gc_incr > 0) ?
            umax2s((1U << opt_lg_tcache_gc_sweep), 10, s) : "N/A", "", "");
        _malloc_message(" (increment interval: ",
            (tcache_nslots && tcache_gc_incr > 0) ?  umax2s(tcache_gc_incr, 10, s)
            : "N/A", ")\n", "");
#endif
        _malloc_message("Chunk size: ", umax2s(chunksize, 10, s), "", "");
        _malloc_message(" (2^", umax2s(opt_lg_chunk, 10, s), ")\n", "");

#ifdef MALLOC_STATS
        {
                size_t allocated, mapped;
                unsigned i;
                arena_t *arena;

                /* Calculate and print allocated/mapped stats. */

                /* arenas. */
                for (i = 0, allocated = 0; i < narenas; i++) {
                        if (arenas[i] != NULL) {
                                malloc_spin_lock(&arenas[i]->lock);
                                allocated += arenas[i]->stats.allocated_small;
                                allocated += arenas[i]->stats.allocated_large;
                                malloc_spin_unlock(&arenas[i]->lock);
                        }
                }

                /* huge/base. */
                malloc_mutex_lock(&huge_mtx);
                allocated += huge_allocated;
                mapped = stats_chunks.curchunks * chunksize;
                malloc_mutex_unlock(&huge_mtx);

                malloc_mutex_lock(&base_mtx);
                mapped += base_mapped;
                malloc_mutex_unlock(&base_mtx);

                malloc_printf("Allocated: %zu, mapped: %zu\n", allocated,
                    mapped);

                /* Print chunk stats. */
                {
                        chunk_stats_t chunks_stats;

                        malloc_mutex_lock(&huge_mtx);
                        chunks_stats = stats_chunks;
                        malloc_mutex_unlock(&huge_mtx);

                        malloc_printf("chunks: nchunks   "
                            "highchunks    curchunks\n");
                        malloc_printf("  %13"PRIu64"%13zu%13zu\n",
                            chunks_stats.nchunks, chunks_stats.highchunks,
                            chunks_stats.curchunks);
                }

                /* Print chunk stats. */
                malloc_printf(
                    "huge: nmalloc      ndalloc    allocated\n");
                malloc_printf(" %12"PRIu64" %12"PRIu64" %12zu\n", huge_nmalloc,
                    huge_ndalloc, huge_allocated);

                /* Print stats for each arena. */
                for (i = 0; i < narenas; i++) {
                        arena = arenas[i];
                        if (arena != NULL) {
                                malloc_printf("\narenas[%u]:\n", i);
                                malloc_spin_lock(&arena->lock);
                                arena_stats_print(arena);
                                malloc_spin_unlock(&arena->lock);
                        }
                }
        }
#endif /* #ifdef MALLOC_STATS */
        _malloc_message("--- End malloc statistics ---\n", "", "", "");
}

#ifdef MALLOC_DEBUG
static void
small_size2bin_validate(void)
{
        size_t i, size, binind;

        assert(small_size2bin[0] == 0xffU);
        i = 1;
#  ifdef MALLOC_TINY
        /* Tiny. */
        for (; i < (1U << LG_TINY_MIN); i++) {
                size = pow2_ceil(1U << LG_TINY_MIN);
                binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
                assert(small_size2bin[i] == binind);
        }
        for (; i < qspace_min; i++) {
                size = pow2_ceil(i);
                binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
                assert(small_size2bin[i] == binind);
        }
#  endif
        /* Quantum-spaced. */
        for (; i <= qspace_max; i++) {
                size = QUANTUM_CEILING(i);
                binind = ntbins + (size >> LG_QUANTUM) - 1;
                assert(small_size2bin[i] == binind);
        }
        /* Cacheline-spaced. */
        for (; i <= cspace_max; i++) {
                size = CACHELINE_CEILING(i);
                binind = ntbins + nqbins + ((size - cspace_min) >>
                    LG_CACHELINE);
                assert(small_size2bin[i] == binind);
        }
        /* Sub-page. */
        for (; i <= sspace_max; i++) {
                size = SUBPAGE_CEILING(i);
                binind = ntbins + nqbins + ncbins + ((size - sspace_min)
                    >> LG_SUBPAGE);
                assert(small_size2bin[i] == binind);
        }
}
#endif

static bool
small_size2bin_init(void)
{

        if (opt_lg_qspace_max != LG_QSPACE_MAX_DEFAULT
            || opt_lg_cspace_max != LG_CSPACE_MAX_DEFAULT
            || sizeof(const_small_size2bin) != small_maxclass + 1)
                return (small_size2bin_init_hard());

        small_size2bin = const_small_size2bin;
#ifdef MALLOC_DEBUG
        assert(sizeof(const_small_size2bin) == small_maxclass + 1);
        small_size2bin_validate();
#endif
        return (false);
}

static bool
small_size2bin_init_hard(void)
{
        size_t i, size, binind;
        uint8_t *custom_small_size2bin;

        assert(opt_lg_qspace_max != LG_QSPACE_MAX_DEFAULT
            || opt_lg_cspace_max != LG_CSPACE_MAX_DEFAULT
            || sizeof(const_small_size2bin) != small_maxclass + 1);

        custom_small_size2bin = (uint8_t *)base_alloc(small_maxclass + 1);
        if (custom_small_size2bin == NULL)
                return (true);

        custom_small_size2bin[0] = 0xffU;
        i = 1;
#ifdef MALLOC_TINY
        /* Tiny. */
        for (; i < (1U << LG_TINY_MIN); i++) {
                size = pow2_ceil(1U << LG_TINY_MIN);
                binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
                custom_small_size2bin[i] = binind;
        }
        for (; i < qspace_min; i++) {
                size = pow2_ceil(i);
                binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
                custom_small_size2bin[i] = binind;
        }
#endif
        /* Quantum-spaced. */
        for (; i <= qspace_max; i++) {
                size = QUANTUM_CEILING(i);
                binind = ntbins + (size >> LG_QUANTUM) - 1;
                custom_small_size2bin[i] = binind;
        }
        /* Cacheline-spaced. */
        for (; i <= cspace_max; i++) {
                size = CACHELINE_CEILING(i);
                binind = ntbins + nqbins + ((size - cspace_min) >>
                    LG_CACHELINE);
                custom_small_size2bin[i] = binind;
        }
        /* Sub-page. */
        for (; i <= sspace_max; i++) {
                size = SUBPAGE_CEILING(i);
                binind = ntbins + nqbins + ncbins + ((size - sspace_min) >>
                    LG_SUBPAGE);
                custom_small_size2bin[i] = binind;
        }

        small_size2bin = custom_small_size2bin;
#ifdef MALLOC_DEBUG
        small_size2bin_validate();
#endif
        return (false);
}

static unsigned
malloc_ncpus(void)
{
        int mib[2];
        unsigned ret;
        int error;
        size_t len;

        error = _elf_aux_info(AT_NCPUS, &ret, sizeof(ret));
        if (error != 0 || ret == 0) {
                mib[0] = CTL_HW;
                mib[1] = HW_NCPU;
                len = sizeof(ret);
                if (sysctl(mib, 2, &ret, &len, (void *)NULL, 0) == -1) {
                        /* Error. */
                        ret = 1;
                }
        }

        return (ret);
}

/*
 * FreeBSD's pthreads implementation calls malloc(3), so the malloc
 * implementation has to take pains to avoid infinite recursion during
 * initialization.
 */
static inline bool
malloc_init(void)
{

        if (malloc_initialized == false)
                return (malloc_init_hard());

        return (false);
}

static bool
malloc_init_hard(void)
{
        unsigned i;
        int linklen;
        char buf[PATH_MAX + 1];
        const char *opts;

        malloc_mutex_lock(&init_lock);
        if (malloc_initialized) {
                /*
                 * Another thread initialized the allocator before this one
                 * acquired init_lock.
                 */
                malloc_mutex_unlock(&init_lock);
                return (false);
        }

        /* Get number of CPUs. */
        ncpus = malloc_ncpus();

        /*
         * Increase the chunk size to the largest page size that is greater
         * than the default chunk size and less than or equal to 4MB.
         */
        {
                size_t pagesizes[MAXPAGESIZES];
                int k, nsizes;

                nsizes = getpagesizes(pagesizes, MAXPAGESIZES);
                for (k = 0; k < nsizes; k++)
                        if (pagesizes[k] <= (1LU << 22))
                                while ((1LU << opt_lg_chunk) < pagesizes[k])
                                        opt_lg_chunk++;
        }

        for (i = 0; i < 3; i++) {
                unsigned j;

                /* Get runtime configuration. */
                switch (i) {
                case 0:
                        if ((linklen = readlink("/etc/malloc.conf", buf,
                                                sizeof(buf) - 1)) != -1) {
                                /*
                                 * Use the contents of the "/etc/malloc.conf"
                                 * symbolic link's name.
                                 */
                                buf[linklen] = '\0';
                                opts = buf;
                        } else {
                                /* No configuration specified. */
                                buf[0] = '\0';
                                opts = buf;
                        }
                        break;
                case 1:
                        if (issetugid() == 0 && (opts =
                            getenv("MALLOC_OPTIONS")) != NULL) {
                                /*
                                 * Do nothing; opts is already initialized to
                                 * the value of the MALLOC_OPTIONS environment
                                 * variable.
                                 */
                        } else {
                                /* No configuration specified. */
                                buf[0] = '\0';
                                opts = buf;
                        }
                        break;
                case 2:
                        if (_malloc_options != NULL) {
                                /*
                                 * Use options that were compiled into the
                                 * program.
                                 */
                                opts = _malloc_options;
                        } else {
                                /* No configuration specified. */
                                buf[0] = '\0';
                                opts = buf;
                        }
                        break;
                default:
                        /* NOTREACHED */
                        assert(false);
                        buf[0] = '\0';
                        opts = buf;
                }

                for (j = 0; opts[j] != '\0'; j++) {
                        unsigned k, nreps;
                        bool nseen;

                        /* Parse repetition count, if any. */
                        for (nreps = 0, nseen = false;; j++, nseen = true) {
                                switch (opts[j]) {
                                        case '0': case '1': case '2': case '3':
                                        case '4': case '5': case '6': case '7':
                                        case '8': case '9':
                                                nreps *= 10;
                                                nreps += opts[j] - '0';
                                                break;
                                        default:
                                                goto MALLOC_OUT;
                                }
                        }
MALLOC_OUT:
                        if (nseen == false)
                                nreps = 1;

                        for (k = 0; k < nreps; k++) {
                                switch (opts[j]) {
                                case 'a':
                                        opt_abort = false;
                                        break;
                                case 'A':
                                        opt_abort = true;
                                        break;
                                case 'c':
                                        if (opt_lg_cspace_max - 1 >
                                            opt_lg_qspace_max &&
                                            opt_lg_cspace_max >
                                            LG_CACHELINE)
                                                opt_lg_cspace_max--;
                                        break;
                                case 'C':
                                        if (opt_lg_cspace_max < PAGE_SHIFT
                                            - 1)
                                                opt_lg_cspace_max++;
                                        break;
                                case 'd':
#ifdef MALLOC_DSS
                                        opt_dss = false;
#endif
                                        break;
                                case 'D':
#ifdef MALLOC_DSS
                                        opt_dss = true;
#endif
                                        break;
                                case 'e':
                                        if (opt_lg_medium_max > PAGE_SHIFT)
                                                opt_lg_medium_max--;
                                        break;
                                case 'E':
                                        if (opt_lg_medium_max + 1 <
                                            opt_lg_chunk)
                                                opt_lg_medium_max++;
                                        break;
                                case 'f':
                                        if (opt_lg_dirty_mult + 1 <
                                            (sizeof(size_t) << 3))
                                                opt_lg_dirty_mult++;
                                        break;
                                case 'F':
                                        if (opt_lg_dirty_mult >= 0)
                                                opt_lg_dirty_mult--;
                                        break;
#ifdef MALLOC_TCACHE
                                case 'g':
                                        if (opt_lg_tcache_gc_sweep >= 0)
                                                opt_lg_tcache_gc_sweep--;
                                        break;
                                case 'G':
                                        if (opt_lg_tcache_gc_sweep + 1 <
                                            (sizeof(size_t) << 3))
                                                opt_lg_tcache_gc_sweep++;
                                        break;
                                case 'h':
                                        if (opt_lg_tcache_nslots > 0)
                                                opt_lg_tcache_nslots--;
                                        break;
                                case 'H':
                                        if (opt_lg_tcache_nslots + 1 <
                                            (sizeof(size_t) << 3))
                                                opt_lg_tcache_nslots++;
                                        break;
#endif
                                case 'j':
                                        opt_junk = false;
                                        break;
                                case 'J':
                                        opt_junk = true;
                                        break;
                                case 'k':
                                        /*
                                         * Chunks always require at least one
                                         * header page, plus enough room to
                                         * hold a run for the largest medium
                                         * size class (one page more than the
                                         * size).
                                         */
                                        if ((1U << (opt_lg_chunk - 1)) >=
                                            (2U << PAGE_SHIFT) + (1U <<
                                            opt_lg_medium_max))
                                                opt_lg_chunk--;
                                        break;
                                case 'K':
                                        if (opt_lg_chunk + 1 <
                                            (sizeof(size_t) << 3))
                                                opt_lg_chunk++;
                                        break;
                                case 'm':
#ifdef MALLOC_DSS
                                        opt_mmap = false;
#endif
                                        break;
                                case 'M':
#ifdef MALLOC_DSS
                                        opt_mmap = true;
#endif
                                        break;
                                case 'n':
                                        opt_narenas_lshift--;
                                        break;
                                case 'N':
                                        opt_narenas_lshift++;
                                        break;
                                case 'p':
                                        opt_stats_print = false;
                                        break;
                                case 'P':
                                        opt_stats_print = true;
                                        break;
                                case 'q':
                                        if (opt_lg_qspace_max > LG_QUANTUM)
                                                opt_lg_qspace_max--;
                                        break;
                                case 'Q':
                                        if (opt_lg_qspace_max + 1 <
                                            opt_lg_cspace_max)
                                                opt_lg_qspace_max++;
                                        break;
                                case 'u':
                                        opt_utrace = false;
                                        break;
                                case 'U':
                                        opt_utrace = true;
                                        break;
                                case 'v':
                                        opt_sysv = false;
                                        break;
                                case 'V':
                                        opt_sysv = true;
                                        break;
                                case 'x':
                                        opt_xmalloc = false;
                                        break;
                                case 'X':
                                        opt_xmalloc = true;
                                        break;
                                case 'z':
                                        opt_zero = false;
                                        break;
                                case 'Z':
                                        opt_zero = true;
                                        break;
                                default: {
                                        char cbuf[2];

                                        cbuf[0] = opts[j];
                                        cbuf[1] = '\0';
                                        _malloc_message(_getprogname(),
                                            ": (malloc) Unsupported character "
                                            "in malloc options: '", cbuf,
                                            "'\n");
                                }
                                }
                        }
                }
        }

#ifdef MALLOC_DSS
        /* Make sure that there is some method for acquiring memory. */
        if (opt_dss == false && opt_mmap == false)
                opt_mmap = true;
#endif
        if (opt_stats_print) {
                /* Print statistics at exit. */
                atexit(stats_print_atexit);
        }


        /* Set variables according to the value of opt_lg_[qc]space_max. */
        qspace_max = (1U << opt_lg_qspace_max);
        cspace_min = CACHELINE_CEILING(qspace_max);
        if (cspace_min == qspace_max)
                cspace_min += CACHELINE;
        cspace_max = (1U << opt_lg_cspace_max);
        sspace_min = SUBPAGE_CEILING(cspace_max);
        if (sspace_min == cspace_max)
                sspace_min += SUBPAGE;
        assert(sspace_min < PAGE_SIZE);
        sspace_max = PAGE_SIZE - SUBPAGE;
        medium_max = (1U << opt_lg_medium_max);

#ifdef MALLOC_TINY
        assert(LG_QUANTUM >= LG_TINY_MIN);
#endif
        assert(ntbins <= LG_QUANTUM);
        nqbins = qspace_max >> LG_QUANTUM;
        ncbins = ((cspace_max - cspace_min) >> LG_CACHELINE) + 1;
        nsbins = ((sspace_max - sspace_min) >> LG_SUBPAGE) + 1;

        /*
         * Compute medium size class spacing and the number of medium size
         * classes.  Limit spacing to no more than pagesize, but if possible
         * use the smallest spacing that does not exceed NMBINS_MAX medium size
         * classes.
         */
        lg_mspace = LG_SUBPAGE;
        nmbins = ((medium_max - medium_min) >> lg_mspace) + 1;
        while (lg_mspace < PAGE_SHIFT && nmbins > NMBINS_MAX) {
                lg_mspace = lg_mspace + 1;
                nmbins = ((medium_max - medium_min) >> lg_mspace) + 1;
        }
        mspace_mask = (1U << lg_mspace) - 1U;

        mbin0 = ntbins + nqbins + ncbins + nsbins;
        nbins = mbin0 + nmbins;
        /*
         * The small_size2bin lookup table uses uint8_t to encode each bin
         * index, so we cannot support more than 256 small size classes.  This
         * limit is difficult to exceed (not even possible with 16B quantum and
         * 4KiB pages), and such configurations are impractical, but
         * nonetheless we need to protect against this case in order to avoid
         * undefined behavior.
         */
        if (mbin0 > 256) {
            char line_buf[UMAX2S_BUFSIZE];
            _malloc_message(_getprogname(),
                ": (malloc) Too many small size classes (",
                umax2s(mbin0, 10, line_buf), " > max 256)\n");
            abort();
        }

        if (small_size2bin_init()) {
                malloc_mutex_unlock(&init_lock);
                return (true);
        }

#ifdef MALLOC_TCACHE
        if (opt_lg_tcache_nslots > 0) {
                tcache_nslots = (1U << opt_lg_tcache_nslots);

                /* Compute incremental GC event threshold. */
                if (opt_lg_tcache_gc_sweep >= 0) {
                        tcache_gc_incr = ((1U << opt_lg_tcache_gc_sweep) /
                            nbins) + (((1U << opt_lg_tcache_gc_sweep) % nbins ==
                            0) ? 0 : 1);
                } else
                        tcache_gc_incr = 0;
        } else
                tcache_nslots = 0;
#endif

        /* Set variables according to the value of opt_lg_chunk. */
        chunksize = (1LU << opt_lg_chunk);
        chunksize_mask = chunksize - 1;
        chunk_npages = (chunksize >> PAGE_SHIFT);
        {
                size_t header_size;

                /*
                 * Compute the header size such that it is large enough to
                 * contain the page map.
                 */
                header_size = sizeof(arena_chunk_t) +
                    (sizeof(arena_chunk_map_t) * (chunk_npages - 1));
                arena_chunk_header_npages = (header_size >> PAGE_SHIFT) +
                    ((header_size & PAGE_MASK) != 0);
        }
        arena_maxclass = chunksize - (arena_chunk_header_npages <<
            PAGE_SHIFT);

        UTRACE((void *)(intptr_t)(-1), 0, 0);

#ifdef MALLOC_STATS
        malloc_mutex_init(&chunks_mtx);
        memset(&stats_chunks, 0, sizeof(chunk_stats_t));
#endif

        /* Various sanity checks that regard configuration. */
        assert(chunksize >= PAGE_SIZE);

        /* Initialize chunks data. */
        malloc_mutex_init(&huge_mtx);
        extent_tree_ad_new(&huge);
#ifdef MALLOC_DSS
        malloc_mutex_init(&dss_mtx);
        dss_base = sbrk(0);
        i = (uintptr_t)dss_base & QUANTUM_MASK;
        if (i != 0)
                dss_base = sbrk(QUANTUM - i);
        dss_prev = dss_base;
        dss_max = dss_base;
        extent_tree_szad_new(&dss_chunks_szad);
        extent_tree_ad_new(&dss_chunks_ad);
#endif
#ifdef MALLOC_STATS
        huge_nmalloc = 0;
        huge_ndalloc = 0;
        huge_allocated = 0;
#endif

        /* Initialize base allocation data structures. */
#ifdef MALLOC_STATS
        base_mapped = 0;
#endif
#ifdef MALLOC_DSS
        /*
         * Allocate a base chunk here, since it doesn't actually have to be
         * chunk-aligned.  Doing this before allocating any other chunks allows
         * the use of space that would otherwise be wasted.
         */
        if (opt_dss)
                base_pages_alloc(0);
#endif
        base_nodes = NULL;
        malloc_mutex_init(&base_mtx);

        if (ncpus > 1) {
                /*
                 * For SMP systems, create more than one arena per CPU by
                 * default.
                 */
#ifdef MALLOC_TCACHE
                if (tcache_nslots) {
                        /*
                         * Only large object allocation/deallocation is
                         * guaranteed to acquire an arena mutex, so we can get
                         * away with fewer arenas than without thread caching.
                         */
                        opt_narenas_lshift += 1;
                } else {
#endif
                        /*
                         * All allocations must acquire an arena mutex, so use
                         * plenty of arenas.
                         */
                        opt_narenas_lshift += 2;
#ifdef MALLOC_TCACHE
                }
#endif
        }

        /* Determine how many arenas to use. */
        narenas = ncpus;
        if (opt_narenas_lshift > 0) {
                if ((narenas << opt_narenas_lshift) > narenas)
                        narenas <<= opt_narenas_lshift;
                /*
                 * Make sure not to exceed the limits of what base_alloc() can
                 * handle.
                 */
                if (narenas * sizeof(arena_t *) > chunksize)
                        narenas = chunksize / sizeof(arena_t *);
        } else if (opt_narenas_lshift < 0) {
                if ((narenas >> -opt_narenas_lshift) < narenas)
                        narenas >>= -opt_narenas_lshift;
                /* Make sure there is at least one arena. */
                if (narenas == 0)
                        narenas = 1;
        }

#ifdef NO_TLS
        if (narenas > 1) {
                static const unsigned primes[] = {1, 3, 5, 7, 11, 13, 17, 19,
                    23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83,
                    89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149,
                    151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211,
                    223, 227, 229, 233, 239, 241, 251, 257, 263};
                unsigned nprimes, parenas;

                /*
                 * Pick a prime number of hash arenas that is more than narenas
                 * so that direct hashing of pthread_self() pointers tends to
                 * spread allocations evenly among the arenas.
                 */
                assert((narenas & 1) == 0); /* narenas must be even. */
                nprimes = (sizeof(primes) >> LG_SIZEOF_INT);
                parenas = primes[nprimes - 1]; /* In case not enough primes. */
                for (i = 1; i < nprimes; i++) {
                        if (primes[i] > narenas) {
                                parenas = primes[i];
                                break;
                        }
                }
                narenas = parenas;
        }
#endif

#ifndef NO_TLS
        next_arena = 0;
#endif

        /* Allocate and initialize arenas. */
        arenas = (arena_t **)base_alloc(sizeof(arena_t *) * narenas);
        if (arenas == NULL) {
                malloc_mutex_unlock(&init_lock);
                return (true);
        }
        /*
         * Zero the array.  In practice, this should always be pre-zeroed,
         * since it was just mmap()ed, but let's be sure.
         */
        memset(arenas, 0, sizeof(arena_t *) * narenas);

        /*
         * Initialize one arena here.  The rest are lazily created in
         * choose_arena_hard().
         */
        arenas_extend(0);
        if (arenas[0] == NULL) {
                malloc_mutex_unlock(&init_lock);
                return (true);
        }
#ifndef NO_TLS
        /*
         * Assign the initial arena to the initial thread, in order to avoid
         * spurious creation of an extra arena if the application switches to
         * threaded mode.
         */
        arenas_map = arenas[0];
#endif
        malloc_spin_init(&arenas_lock);

        malloc_initialized = true;
        malloc_mutex_unlock(&init_lock);
        return (false);
}

/*
 * End general internal functions.
 */
/******************************************************************************/
/*
 * Begin malloc(3)-compatible functions.
 */

void *
malloc(size_t size)
{
        void *ret;

        if (malloc_init()) {
                ret = NULL;
                goto OOM;
        }

        if (size == 0) {
                if (opt_sysv == false)
                        size = 1;
                else {
                        if (opt_xmalloc) {
                                _malloc_message(_getprogname(),
                                    ": (malloc) Error in malloc(): "
                                    "invalid size 0\n", "", "");
                                abort();
                        }
                        ret = NULL;
                        goto RETURN;
                }
        }

        ret = imalloc(size);

OOM:
        if (ret == NULL) {
                if (opt_xmalloc) {
                        _malloc_message(_getprogname(),
                            ": (malloc) Error in malloc(): out of memory\n", "",
                            "");
                        abort();
                }
                errno = ENOMEM;
        }

RETURN:
        UTRACE(0, size, ret);
        return (ret);
}

int
posix_memalign(void **memptr, size_t alignment, size_t size)
{
        int ret;
        void *result;

        if (malloc_init())
                result = NULL;
        else {
                if (size == 0) {
                        if (opt_sysv == false)
                                size = 1;
                        else {
                                if (opt_xmalloc) {
                                        _malloc_message(_getprogname(),
                                            ": (malloc) Error in "
                                            "posix_memalign(): invalid "
                                            "size 0\n", "", "");
                                        abort();
                                }
                                result = NULL;
                                *memptr = NULL;
                                ret = 0;
                                goto RETURN;
                        }
                }

                /* Make sure that alignment is a large enough power of 2. */
                if (((alignment - 1) & alignment) != 0
                    || alignment < sizeof(void *)) {
                        if (opt_xmalloc) {
                                _malloc_message(_getprogname(),
                                    ": (malloc) Error in posix_memalign(): "
                                    "invalid alignment\n", "", "");
                                abort();
                        }
                        result = NULL;
                        ret = EINVAL;
                        goto RETURN;
                }

                result = ipalloc(alignment, size);
        }

        if (result == NULL) {
                if (opt_xmalloc) {
                        _malloc_message(_getprogname(),
                        ": (malloc) Error in posix_memalign(): out of memory\n",
                        "", "");
                        abort();
                }
                ret = ENOMEM;
                goto RETURN;
        }

        *memptr = result;
        ret = 0;

RETURN:
        UTRACE(0, size, result);
        return (ret);
}

void *
aligned_alloc(size_t alignment, size_t size)
{
        void *memptr;
        int ret;

        ret = posix_memalign(&memptr, alignment, size);
        if (ret != 0) {
                errno = ret;
                return (NULL);
        }
        return (memptr);
}

void *
calloc(size_t num, size_t size)
{
        void *ret;
        size_t num_size;

        if (malloc_init()) {
                num_size = 0;
                ret = NULL;
                goto RETURN;
        }

        num_size = num * size;
        if (num_size == 0) {
                if ((opt_sysv == false) && ((num == 0) || (size == 0)))
                        num_size = 1;
                else {
                        ret = NULL;
                        goto RETURN;
                }
        /*
         * Try to avoid division here.  We know that it isn't possible to
         * overflow during multiplication if neither operand uses any of the
         * most significant half of the bits in a size_t.
         */
        } else if (((num | size) & (SIZE_T_MAX << (sizeof(size_t) << 2)))
            && (num_size / size != num)) {
                /* size_t overflow. */
                ret = NULL;
                goto RETURN;
        }

        ret = icalloc(num_size);

RETURN:
        if (ret == NULL) {
                if (opt_xmalloc) {
                        _malloc_message(_getprogname(),
                            ": (malloc) Error in calloc(): out of memory\n", "",
                            "");
                        abort();
                }
                errno = ENOMEM;
        }

        UTRACE(0, num_size, ret);
        return (ret);
}

void *
realloc(void *ptr, size_t size)
{
        void *ret;

        if (size == 0) {
                if (opt_sysv == false)
                        size = 1;
                else {
                        if (ptr != NULL)
                                idalloc(ptr);
                        ret = NULL;
                        goto RETURN;
                }
        }

        if (ptr != NULL) {
                assert(malloc_initialized);

                ret = iralloc(ptr, size);

                if (ret == NULL) {
                        if (opt_xmalloc) {
                                _malloc_message(_getprogname(),
                                    ": (malloc) Error in realloc(): out of "
                                    "memory\n", "", "");
                                abort();
                        }
                        errno = ENOMEM;
                }
        } else {
                if (malloc_init())
                        ret = NULL;
                else
                        ret = imalloc(size);

                if (ret == NULL) {
                        if (opt_xmalloc) {
                                _malloc_message(_getprogname(),
                                    ": (malloc) Error in realloc(): out of "
                                    "memory\n", "", "");
                                abort();
                        }
                        errno = ENOMEM;
                }
        }

RETURN:
        UTRACE(ptr, size, ret);
        return (ret);
}

void
free(void *ptr)
{

        UTRACE(ptr, 0, 0);
        if (ptr != NULL) {
                assert(malloc_initialized);

                idalloc(ptr);
        }
}

/*
 * End malloc(3)-compatible functions.
 */
/******************************************************************************/
/*
 * Begin non-standard functions.
 */

size_t
malloc_usable_size(const void *ptr)
{

        assert(ptr != NULL);

        return (isalloc(ptr));
}

/*
 * End non-standard functions.
 */
/******************************************************************************/
/*
 * Begin library-private functions.
 */

/*
 * We provide an unpublished interface in order to receive notifications from
 * the pthreads library whenever a thread exits.  This allows us to clean up
 * thread caches.
 */
void
_malloc_thread_cleanup(void)
{

#ifdef MALLOC_TCACHE
        tcache_t *tcache = tcache_tls;

        if (tcache != NULL) {
                assert(tcache != (void *)(uintptr_t)1);
                tcache_destroy(tcache);
                tcache_tls = (void *)(uintptr_t)1;
        }
#endif
}

/*
 * The following functions are used by threading libraries for protection of
 * malloc during fork().  These functions are only called if the program is
 * running in threaded mode, so there is no need to check whether the program
 * is threaded here.
 */

void
_malloc_prefork(void)
{
        unsigned i;

        /* Acquire all mutexes in a safe order. */
        malloc_spin_lock(&arenas_lock);
        for (i = 0; i < narenas; i++) {
                if (arenas[i] != NULL)
                        malloc_spin_lock(&arenas[i]->lock);
        }

        malloc_mutex_lock(&base_mtx);

        malloc_mutex_lock(&huge_mtx);

#ifdef MALLOC_DSS
        malloc_mutex_lock(&dss_mtx);
#endif
}

void
_malloc_postfork(void)
{
        unsigned i;

        /* Release all mutexes, now that fork() has completed. */

#ifdef MALLOC_DSS
        malloc_mutex_unlock(&dss_mtx);
#endif

        malloc_mutex_unlock(&huge_mtx);

        malloc_mutex_unlock(&base_mtx);

        for (i = 0; i < narenas; i++) {
                if (arenas[i] != NULL)
                        malloc_spin_unlock(&arenas[i]->lock);
        }
        malloc_spin_unlock(&arenas_lock);
}

/*
 * End library-private functions.
 */
/******************************************************************************/