Add comments and reformat/rearrange code. There are no significant

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

/*-
 * Copyright (C) 2006 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.
 *
 *   + Cache line sharing between arenas is avoided for internal data
 *     structures.
 *
 *   + Memory is managed in chunks and runs (chunks can be split into runs using
 *     a binary buddy scheme), 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 kB pages
 * and a 16 byte quantum, the size classes in each category are as follows:
 *
 *   |====================================|
 *   | Category | Subcategory    |   Size |
 *   |====================================|
 *   | Small    | Tiny           |      2 |
 *   |          |                |      4 |
 *   |          |                |      8 |
 *   |          |----------------+--------|
 *   |          | Quantum-spaced |     16 |
 *   |          |                |     32 |
 *   |          |                |     48 |
 *   |          |                |    ... |
 *   |          |                |    480 |
 *   |          |                |    496 |
 *   |          |                |    512 |
 *   |          |----------------+--------|
 *   |          | Sub-page       |   1 kB |
 *   |          |                |   2 kB |
 *   |====================================|
 *   | Medium                    |   4 kB |
 *   |                           |   8 kB |
 *   |                           |  16 kB |
 *   |                           |    ... |
 *   |                           | 256 kB |
 *   |                           | 512 kB |
 *   |                           |   1 MB |
 *   |====================================|
 *   | Large                     |   2 MB |
 *   |                           |   4 MB |
 *   |                           |   6 MB |
 *   |                           |    ... |
 *   |====================================|
 *
 * A different mechanism is used for each category:
 *
 *   Small : Each size class is segregated into its own set of runs.  Each run
 *           maintains a bitmap of which regions are free/allocated.
 *
 *   Medium : Each allocation is backed by a dedicated run.  Metadata are stored
 *            in the associated arena chunk header maps.
 *
 *   Large : Each allocation is backed by a dedicated contiguous set of chunks.
 *           Metadata are stored in a separate red-black tree.
 *
 *******************************************************************************
 */

/*
 *******************************************************************************
 *
 * Ring macros.
 *
 *******************************************************************************
 */

/* Ring definitions. */
#define qr(a_type) struct {                                             \
        a_type *qre_next;                                               \
        a_type *qre_prev;                                               \
}

#define qr_initializer {NULL, NULL}

/* Ring functions. */
#define qr_new(a_qr, a_field) do {                                      \
        (a_qr)->a_field.qre_next = (a_qr);                              \
        (a_qr)->a_field.qre_prev = (a_qr);                              \
} while (0)

#define qr_next(a_qr, a_field) ((a_qr)->a_field.qre_next)

#define qr_prev(a_qr, a_field) ((a_qr)->a_field.qre_prev)

#define qr_before_insert(a_qrelm, a_qr, a_field) do {                   \
        (a_qr)->a_field.qre_prev = (a_qrelm)->a_field.qre_prev;         \
        (a_qr)->a_field.qre_next = (a_qrelm);                           \
        (a_qr)->a_field.qre_prev->a_field.qre_next = (a_qr);            \
        (a_qrelm)->a_field.qre_prev = (a_qr);                           \
} while (0)

#define qr_after_insert(a_qrelm, a_qr, a_field) do {                    \
        (a_qr)->a_field.qre_next = (a_qrelm)->a_field.qre_next;         \
        (a_qr)->a_field.qre_prev = (a_qrelm);                           \
        (a_qr)->a_field.qre_next->a_field.qre_prev = (a_qr);            \
        (a_qrelm)->a_field.qre_next = (a_qr);                           \
} while (0)

#define qr_meld(a_qr_a, a_qr_b, a_type, a_field) do {                   \
        a_type *t;                                                      \
        (a_qr_a)->a_field.qre_prev->a_field.qre_next = (a_qr_b);        \
        (a_qr_b)->a_field.qre_prev->a_field.qre_next = (a_qr_a);        \
        t = (a_qr_a)->a_field.qre_prev;                                 \
        (a_qr_a)->a_field.qre_prev = (a_qr_b)->a_field.qre_prev;        \
        (a_qr_b)->a_field.qre_prev = t;                                 \
} while (0)

/* qr_meld() and qr_split() are functionally equivalent, so there's no need to
 * have two copies of the code. */
#define qr_split(a_qr_a, a_qr_b, a_type, a_field)                       \
        qr_meld((a_qr_a), (a_qr_b), a_type, a_field)

#define qr_remove(a_qr, a_field) do {                                   \
        (a_qr)->a_field.qre_prev->a_field.qre_next                      \
            = (a_qr)->a_field.qre_next;                                 \
        (a_qr)->a_field.qre_next->a_field.qre_prev                      \
            = (a_qr)->a_field.qre_prev;                                 \
        (a_qr)->a_field.qre_next = (a_qr);                              \
        (a_qr)->a_field.qre_prev = (a_qr);                              \
} while (0)

#define qr_foreach(var, a_qr, a_field)                                  \
        for ((var) = (a_qr);                                            \
            (var) != NULL;                                              \
            (var) = (((var)->a_field.qre_next != (a_qr))                \
            ? (var)->a_field.qre_next : NULL))

#define qr_reverse_foreach(var, a_qr, a_field)                          \
        for ((var) = ((a_qr) != NULL) ? qr_prev(a_qr, a_field) : NULL;  \
            (var) != NULL;                                              \
            (var) = (((var) != (a_qr))                                  \
            ? (var)->a_field.qre_prev : NULL))

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

/*
 * In order to disable various extra features that may have negative
 * performance impacts, (assertions, expanded statistics, redzones), define
 * NO_MALLOC_EXTRAS.
 */
/* #define NO_MALLOC_EXTRAS */

#ifndef NO_MALLOC_EXTRAS
#  define MALLOC_DEBUG
#endif

#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/stddef.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/sysctl.h>
#include <sys/tree.h>
#include <sys/uio.h>
#include <sys/ktrace.h> /* Must come after several other sys/ includes. */

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

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

#include "un-namespace.h"

/*
 * Calculate statistics that can be used to get an idea of how well caching is
 * working.
 */
#ifndef NO_MALLOC_EXTRAS
#  define MALLOC_STATS
#endif

#ifndef MALLOC_DEBUG
#  ifndef NDEBUG
#    define NDEBUG
#  endif
#endif
#include <assert.h>

#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^QUANTUM_2POW_MIN bytes. */
#ifdef __i386__
#  define QUANTUM_2POW_MIN      4
#  define SIZEOF_PTR            4
#  define USE_BRK
#endif
#ifdef __ia64__
#  define QUANTUM_2POW_MIN      4
#  define SIZEOF_PTR            8
#  define NO_TLS
#endif
#ifdef __alpha__
#  define QUANTUM_2POW_MIN      4
#  define SIZEOF_PTR            8
#  define NO_TLS
#endif
#ifdef __sparc64__
#  define QUANTUM_2POW_MIN      4
#  define SIZEOF_PTR            8
#  define NO_TLS
#endif
#ifdef __amd64__
#  define QUANTUM_2POW_MIN      4
#  define SIZEOF_PTR            8
#endif
#ifdef __arm__
#  define QUANTUM_2POW_MIN      3
#  define SIZEOF_PTR            4
#  define USE_BRK
#  define NO_TLS
#endif
#ifdef __powerpc__
#  define QUANTUM_2POW_MIN      4
#  define SIZEOF_PTR            4
#  define USE_BRK
#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

/*
 * Size and alignment of memory chunks that are allocated by the OS's virtual
 * memory system.
 *
 * chunksize limits:
 *
 *   2^(pagesize_2pow - 1 + RUN_MIN_REGS_2POW) <= chunk_size <= 2^28
 */
#define CHUNK_2POW_DEFAULT      21
#define CHUNK_2POW_MAX          28

/*
 * Maximum size of L1 cache line.  This is used to avoid cache line aliasing,
 * so over-estimates are okay (up to a point), but under-estimates will
 * negatively affect performance.
 */
#define CACHELINE_2POW 6
#define CACHELINE ((size_t)(1 << CACHELINE_2POW))

/*
 * 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 SMALL_MAX_2POW_DEFAULT 9
#define SMALL_MAX_DEFAULT (1 << SMALL_MAX_2POW_DEFAULT)

/*
 * Minimum number of regions that must fit into a run that serves quantum-size
 * bin allocations.
 *
 * Note that if this is set too low, space will be wasted if there are size
 * classes that are small enough that RUN_MIN_REGS regions don't fill a page.
 * If this is set too high, then the overhead of searching through the bitmap
 * that tracks region usage will become excessive.
 */
#define RUN_MIN_REGS_2POW 10
#define RUN_MIN_REGS (1 << RUN_MIN_REGS_2POW)

/*
 * Maximum number of pages for a run that is used for bin allocations.
 *
 * Note that if this is set too low, then fragmentation for the largest bin
 * size classes will be high.  If this is set too high, then even small
 * programs will often have to allocate more than two chunks early on.
 */
#define RUN_MAX_PAGES_2POW 4
#define RUN_MAX_PAGES (1 << RUN_MAX_PAGES_2POW)

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

/*
 * Mutexes based on spinlocks.  We can't use normal pthread mutexes, because
 * they require malloc()ed memory.
 */
typedef struct {
        spinlock_t      lock;
} malloc_mutex_t;

static bool malloc_initialized = false;

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

#ifdef MALLOC_STATS

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;

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

        /*
         * Total number of run promotions/demotions for this bin's size class.
         */
        uint64_t        npromote;
        uint64_t        ndemote;

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

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

typedef struct arena_stats_s arena_stats_t;
struct arena_stats_s {
        /* Total byte count of allocated memory, not including overhead. */
        size_t          allocated;

        /* Number of times each function was called. */
        uint64_t        nmalloc;
        uint64_t        npalloc;
        uint64_t        ncalloc;
        uint64_t        ndalloc;
        uint64_t        nralloc;
        uint64_t        nmadvise;
};

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. */
        unsigned long   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.
         */
        unsigned long   curchunks;
};

#endif /* #ifdef MALLOC_STATS */

/******************************************************************************/
/*
 * Chunk data structures.
 */

/* Tree of chunks. */
typedef struct chunk_node_s chunk_node_t;
struct chunk_node_s {
        /* Linkage for the chunk tree. */
        RB_ENTRY(chunk_node_s) link;

        /*
         * Pointer to the chunk that this tree node is responsible for.  In some
         * (but certainly not all) cases, this data structure is placed at the
         * beginning of the corresponding chunk, so this field may point to this
         * node.
         */
        void    *chunk;

        /* Total chunk size. */
        size_t  size;
};
typedef struct chunk_tree_s chunk_tree_t;
RB_HEAD(chunk_tree_s, chunk_node_s);

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

typedef struct arena_s arena_t;
typedef struct arena_bin_s arena_bin_t;

typedef struct arena_chunk_map_s arena_chunk_map_t;
struct arena_chunk_map_s {
        bool            free:1;
        bool            large:1;
        unsigned        npages:15; /* Limiting factor for CHUNK_2POW_MAX. */
        unsigned        pos:15;
};

/* 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 chunk tree. */
        RB_ENTRY(arena_chunk_s) link;

        /*
         * Number of pages in use.  This is maintained in order to make
         * detection of empty chunks fast.
         */
        uint32_t pages_used;

        /*
         * Array of counters that keeps track of how many free runs of each
         * size are available in this chunk.  This table is sized at compile
         * time, which is wasteful.  However, due to unrelated rounding, this
         * doesn't actually waste any otherwise useful space.
         *
         *   index == 2^n pages
         *
         *   index | npages
         *   ------+-------
         *       0 |      1
         *       1 |      2
         *       2 |      4
         *       3 |      8
         *         :
         */
        uint32_t nfree_runs[CHUNK_2POW_MAX/* - PAGE_SHIFT */];

        /* Map of pages within chunk that keeps track of free/large/small. */
        arena_chunk_map_t map[1]; /* Dynamically sized. */
};
typedef struct arena_chunk_tree_s arena_chunk_tree_t;
RB_HEAD(arena_chunk_tree_s, arena_chunk_s);

typedef struct arena_run_s arena_run_t;
struct arena_run_s {
        /* Linkage for run rings. */
        qr(arena_run_t) link;

#ifdef MALLOC_DEBUG
        uint32_t        magic;
#  define ARENA_RUN_MAGIC 0x384adf93
#endif

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

        /* Bitmask of in-use regions (0: in use, 1: free). */
#define REGS_MASK_NELMS                                                 \
        ((1 << (RUN_MIN_REGS_2POW + 1)) / (sizeof(unsigned) << 3))
        unsigned        regs_mask[REGS_MASK_NELMS];

        /* Index of first element that might have a free region. */
        unsigned        regs_minelm:(RUN_MIN_REGS_2POW + 2);

        /* Number of free regions in run. */
        unsigned        nfree:(RUN_MIN_REGS_2POW + 2);

        /*
         * Current quartile for this run, one of: {RUN_QINIT, RUN_Q0, RUN_25,
         * RUN_Q50, RUN_Q75, RUN_Q100}.
         */
#define RUN_QINIT       0
#define RUN_Q0          1
#define RUN_Q25         2
#define RUN_Q50         3
#define RUN_Q75         4
#define RUN_Q100        5
        unsigned        quartile:3;

        /*
         * Limits on the number of free regions for the fullness quartile this
         * run is currently in.  If nfree goes outside these limits, the run
         * is moved to a different fullness quartile.
         */
        unsigned        free_max:(RUN_MIN_REGS_2POW + 2);
        unsigned        free_min:(RUN_MIN_REGS_2POW + 2);
};

/* Used for run ring headers, where the run isn't actually used. */
typedef struct arena_run_link_s arena_run_link_t;
struct arena_run_link_s {
        /* Linkage for run rings. */
        qr(arena_run_t) link;
};

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

        /*
         * Links into rings of runs, of various fullnesses (names indicate
         * approximate lower bounds).  A new run conceptually starts off in
         * runsinit, and it isn't inserted into the runs0 ring until it
         * reaches 25% full (hysteresis mechanism).  For the run to be moved
         * again, it must become either empty or 50% full.  Thus, each ring
         * contains runs that are within 50% above the advertised fullness for
         * the ring.  This provides a low-overhead mechanism for segregating
         * runs into approximate fullness classes.
         *
         * Conceptually, there is a runs100 that contains completely full runs.
         * Since we don't need to search for these runs though, no runs100 ring
         * is actually maintained.
         *
         * These rings are useful when looking for an existing run to use when
         * runcur is no longer usable.  We look for usable runs in the
         * following order:
         *
         *   1) runs50
         *   2) runs25
         *   3) runs0
         *   4) runs75
         *
         * runs75 isn't a good place to look, because it contains runs that may
         * be nearly completely full.  Still, we look there as a last resort in
         * order to avoid allocating a new run if at all possible.
         */
        /* arena_run_link_t     runsinit;   0% <= fullness <   25% */
        arena_run_link_t        runs0;  /*  0% <  fullness <   50% */
        arena_run_link_t        runs25; /* 25% <  fullness <   75% */
        arena_run_link_t        runs50; /* 50% <  fullness <  100% */
        arena_run_link_t        runs75; /* 75% <  fullness <  100% */
        /* arena_run_link_t     runs100;          fullness == 100% */

        /* 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;

        /* 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
};

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

        /* All operations on this arena require that mtx be locked. */
        malloc_mutex_t          mtx;

#ifdef MALLOC_STATS
        arena_stats_t           stats;
#endif

        /*
         * Tree of chunks this arena manages.
         */
        arena_chunk_tree_t      chunks;

        /*
         * bins is used to store rings of free regions of the following sizes,
         * assuming a 16-byte quantum, 4kB pagesize, and default MALLOC_OPTIONS.
         *
         *   bins[i] | size |
         *   --------+------+
         *        0  |    2 |
         *        1  |    4 |
         *        2  |    8 |
         *   --------+------+
         *        3  |   16 |
         *        4  |   32 |
         *        5  |   48 |
         *        6  |   64 |
         *           :      :
         *           :      :
         *       33  |  496 |
         *       34  |  512 |
         *   --------+------+
         *       35  | 1024 |
         *       36  | 2048 |
         *   --------+------+
         */
        arena_bin_t             bins[1]; /* Dynamically sized. */
};

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

/* Used as a special "nil" return value for malloc(0). */
static int              nil;

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

/* VM page size. */
static unsigned         pagesize;
static unsigned         pagesize_2pow;

/* Various bin-related settings. */
static size_t           bin_maxclass; /* Max size class for bins. */
static unsigned         ntbins; /* Number of (2^n)-spaced tiny bins. */
static unsigned         nqbins; /* Number of quantum-spaced bins. */
static unsigned         nsbins; /* Number of (2^n)-spaced sub-page bins. */
static size_t           small_min;
static size_t           small_max;
static unsigned         tiny_min_2pow;

/* Various quantum-related settings. */
static size_t           quantum;
static size_t           quantum_mask; /* (quantum - 1). */

/* Various chunk-related settings. */
static size_t           chunk_size;
static size_t           chunk_size_mask; /* (chunk_size - 1). */
static size_t           arena_maxclass; /* Max size class for arenas. */
static unsigned         arena_chunk_maplen;

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

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

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

#ifdef USE_BRK
/*
 * Try to use brk for chunk-size allocations, due to address space constraints.
 */
/* Result of first sbrk(0) call. */
static void             *brk_base;
/* Current end of brk, or ((void *)-1) if brk is exhausted. */
static void             *brk_prev;
/* Upper limit on brk addresses (may be an over-estimate). */
static void             *brk_max;
#endif

#ifdef MALLOC_STATS
/*
 * Byte counters for allocated/total space used by the chunks in the huge
 * allocations tree.
 */
static uint64_t         huge_nmalloc;
static uint64_t         huge_ndalloc;
static size_t           huge_allocated;
#endif

/*
 * Tree of chunks that were previously allocated.  This is used when allocating
 * chunks, in an attempt to re-use address space.
 */
static chunk_tree_t     old_chunks;

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

/*
 * Current chunk that is being used for internal memory allocations.  This
 * chunk is carved up in cacheline-size quanta, so that there is no chance of
 * false cache line sharing.
 */
static void             *base_chunk;
static void             *base_next_addr;
static void             *base_past_addr; /* Addr immediately past base_chunk. */
static chunk_node_t     *base_chunk_nodes; /* LIFO cache of chunk nodes. */
static malloc_mutex_t   base_mtx;
#ifdef MALLOC_STATS
static uint64_t         base_total;
#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 malloc_mutex_t   arenas_mtx; /* 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;
#endif

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

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

#ifndef NO_MALLOC_EXTRAS
static bool     opt_abort = true;
static bool     opt_junk = true;
#else
static bool     opt_abort = false;
static bool     opt_junk = false;
#endif
static bool     opt_hint = false;
static bool     opt_print_stats = false;
static size_t   opt_quantum_2pow = QUANTUM_2POW_MIN;
static size_t   opt_small_max_2pow = SMALL_MAX_2POW_DEFAULT;
static size_t   opt_chunk_2pow = CHUNK_2POW_DEFAULT;
static bool     opt_utrace = false;
static bool     opt_sysv = false;
static bool     opt_xmalloc = false;
static bool     opt_zero = false;
static int32_t  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 = {a, b, c};                         \
                utrace(&ut, sizeof(ut));                                \
        }

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

static void     malloc_mutex_init(malloc_mutex_t *a_mutex);
static void     wrtmessage(const char *p1, const char *p2, const char *p3,
                const char *p4);
static void     malloc_printf(const char *format, ...);
static void     *base_alloc(size_t size);
static chunk_node_t *base_chunk_node_alloc(void);
static void     base_chunk_node_dealloc(chunk_node_t *node);
#ifdef MALLOC_STATS
static void     stats_print(arena_t *arena);
#endif
static void     *pages_map(void *addr, size_t size);
static void     pages_unmap(void *addr, size_t size);
static void     *chunk_alloc(size_t size);
static void     chunk_dealloc(void *chunk, size_t size);
static void     arena_run_split(arena_t *arena, arena_run_t *run, bool large,
    size_t size);
static arena_chunk_t *arena_chunk_alloc(arena_t *arena);
static void     arena_chunk_dealloc(arena_chunk_t *chunk);
static void     arena_bin_run_refile(arena_t *arena, arena_bin_t *bin,
    arena_run_t *run, size_t size, bool promote);
static arena_run_t *arena_run_alloc(arena_t *arena, bool large, size_t size);
static void     arena_run_dalloc(arena_t *arena, arena_run_t *run, size_t size);
static arena_run_t *arena_bin_nonfull_run_get(arena_t *arena, arena_bin_t *bin,
    size_t size);
static void *arena_bin_malloc_hard(arena_t *arena, arena_bin_t *bin,
    size_t size);
static void     *arena_malloc(arena_t *arena, size_t size);
static size_t   arena_salloc(arena_t *arena, const void *ptr);
static void     *arena_ralloc(arena_t *arena, void *ptr, size_t size,
    size_t oldsize);
static void     arena_dalloc(arena_t *arena, void *ptr);
static bool     arena_new(arena_t *arena);
static arena_t  *arenas_extend(unsigned ind);
#ifndef NO_TLS
static arena_t  *choose_arena_hard(void);
#endif
static void     *huge_malloc(size_t size);
static void     *huge_ralloc(void *ptr, size_t size, size_t oldsize);
static void     huge_dalloc(void *ptr);
static void     *imalloc(arena_t *arena, size_t size);
static void     *ipalloc(arena_t *arena, size_t alignment, size_t size);
static void     *icalloc(arena_t *arena, size_t size);
static size_t   isalloc(const void *ptr);
static void     *iralloc(arena_t *arena, void *ptr, size_t size);
static void     idalloc(void *ptr);
static void     malloc_print_stats(void);
static bool     malloc_init_hard(void);

/*
 * End function prototypes.
 */
/******************************************************************************/
/*
 * Begin mutex.
 */

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

        a_mutex->lock = lock;
}

static inline void
malloc_mutex_lock(malloc_mutex_t *a_mutex)
{

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

static inline void
malloc_mutex_unlock(malloc_mutex_t *a_mutex)
{

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

/*
 * End mutex.
 */
/******************************************************************************/
/*
 * Begin Utility functions/macros.
 */

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

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

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

/* Return the smallest cacheline multiple that is >= s. */
#define CACHELINE_CEILING(s)                                            \
        (((s) + (CACHELINE - 1)) & ~(CACHELINE - 1))

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

/* Compute the smallest power of 2 that is >= x. */
static inline 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);
}

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

        _write(STDERR_FILENO, p1, strlen(p1));
        _write(STDERR_FILENO, p2, strlen(p2));
        _write(STDERR_FILENO, p3, strlen(p3));
        _write(STDERR_FILENO, p4, strlen(p4));
}

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

/*
 * 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, "", "", "");
}

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

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) {
                void *tchunk;

                assert(csize <= chunk_size);

                tchunk = chunk_alloc(chunk_size);
                if (tchunk == NULL) {
                        ret = NULL;
                        goto RETURN;
                }
                base_chunk = tchunk;
                base_next_addr = (void *)base_chunk;
                base_past_addr = (void *)((uintptr_t)base_chunk + chunk_size);
#ifdef MALLOC_STATS
                base_total += chunk_size;
#endif
        }

        /* Allocate. */
        ret = base_next_addr;
        base_next_addr = (void *)((uintptr_t)base_next_addr + csize);

RETURN:
        malloc_mutex_unlock(&base_mtx);
        return (ret);
}

static chunk_node_t *
base_chunk_node_alloc(void)
{
        chunk_node_t *ret;

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

        return (ret);
}

static void
base_chunk_node_dealloc(chunk_node_t *node)
{

        malloc_mutex_lock(&base_mtx);
        *(chunk_node_t **)node = base_chunk_nodes;
        base_chunk_nodes = node;
        malloc_mutex_unlock(&base_mtx);
}

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

#ifdef MALLOC_STATS
static void
stats_print(arena_t *arena)
{
        unsigned i;
        int gap_start;

        malloc_printf("allocated: %zu\n", arena->stats.allocated);

        malloc_printf("calls:\n");
        malloc_printf(" %12s %12s %12s %12s %12s %12s\n", "nmalloc", "npalloc",
            "ncalloc", "ndalloc", "nralloc", "nmadvise");
        malloc_printf(" %12llu %12llu %12llu %12llu %12llu %12llu\n",
            arena->stats.nmalloc, arena->stats.npalloc, arena->stats.ncalloc,
            arena->stats.ndalloc, arena->stats.nralloc, arena->stats.nmadvise);

        malloc_printf("bins:\n");
        malloc_printf("%13s %1s %4s %5s %8s %9s %5s %6s %7s %6s %6s\n",
            "bin", "", "size", "nregs", "run_size", "nrequests", "nruns",
            "hiruns", "curruns", "npromo", "ndemo");
        for (i = 0, gap_start = -1; i < ntbins + nqbins + nsbins; i++) {
                if (arena->bins[i].stats.nrequests == 0) {
                        if (gap_start == -1)
                                gap_start = i;
                } else {
                        if (gap_start != -1) {
                                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 = -1;
                        }
                        malloc_printf(
                            "%13u %1s %4u %5u %8u %9llu %5llu"
                            " %6lu %7lu %6llu %6llu\n",
                            i,
                            i < ntbins ? "T" : i < ntbins + nqbins ? "Q" : "S",
                            arena->bins[i].reg_size,
                            arena->bins[i].nregs,
                            arena->bins[i].run_size,
                            arena->bins[i].stats.nrequests,
                            arena->bins[i].stats.nruns,
                            arena->bins[i].stats.highruns,
                            arena->bins[i].stats.curruns,
                            arena->bins[i].stats.npromote,
                            arena->bins[i].stats.ndemote);
                }
        }
        if (gap_start != -1) {
                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);
                }
        }
}
#endif

/*
 * End Utility functions/macros.
 */
/******************************************************************************/
/*
 * Begin chunk management functions.
 */

static inline int
chunk_comp(chunk_node_t *a, chunk_node_t *b)
{

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

        if ((uintptr_t)a->chunk < (uintptr_t)b->chunk)
                return (-1);
        else if (a->chunk == b->chunk)
                return (0);
        else
                return (1);
}

/* Generate red-black tree code for chunks. */
RB_GENERATE_STATIC(chunk_tree_s, chunk_node_s, link, chunk_comp);

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

#ifdef USE_BRK
AGAIN:
#endif
        /*
         * 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_printf("%s: (malloc) Error in munmap(): %s\n",
                            _getprogname(), buf);
                        if (opt_abort)
                                abort();
                }
                ret = NULL;
        }
#ifdef USE_BRK
        else if ((uintptr_t)ret >= (uintptr_t)brk_base
            && (uintptr_t)ret < (uintptr_t)brk_max) {
                /*
                 * We succeeded in mapping memory, but at a location that could
                 * be confused with brk.  Leave the mapping intact so that this
                 * won't ever happen again, then try again.
                 */
                assert(addr == NULL);
                goto AGAIN;
        }
#endif

        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_printf("%s: (malloc) Error in munmap(): %s\n",
                    _getprogname(), buf);
                if (opt_abort)
                        abort();
        }
}

static void *
chunk_alloc(size_t size)
{
        void *ret, *chunk;
        chunk_node_t *tchunk, *delchunk;

        assert(size != 0);
        assert(size % chunk_size == 0);

        malloc_mutex_lock(&chunks_mtx);

        if (size == chunk_size) {
                /*
                 * Check for address ranges that were previously chunks and try
                 * to use them.
                 */

                tchunk = RB_MIN(chunk_tree_s, &old_chunks);
                while (tchunk != NULL) {
                        /* Found an address range.  Try to recycle it. */

                        chunk = tchunk->chunk;
                        delchunk = tchunk;
                        tchunk = RB_NEXT(chunk_tree_s, &old_chunks, delchunk);

                        /* Remove delchunk from the tree. */
                        RB_REMOVE(chunk_tree_s, &old_chunks, delchunk);
                        base_chunk_node_dealloc(delchunk);

#ifdef USE_BRK
                        if ((uintptr_t)chunk >= (uintptr_t)brk_base
                            && (uintptr_t)chunk < (uintptr_t)brk_max) {
                                /* Re-use a previously freed brk chunk. */
                                ret = chunk;
                                goto RETURN;
                        }
#endif
                        if ((ret = pages_map(chunk, size)) != NULL) {
                                /* Success. */
                                goto RETURN;
                        }
                }

#ifdef USE_BRK
                /*
                 * Try to create chunk-size allocations in brk, in order to
                 * make full use of limited address space.
                 */
                if (brk_prev != (void *)-1) {
                        void *brk_cur;
                        intptr_t incr;

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

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

                                brk_prev = sbrk(incr);
                                if (brk_prev == brk_cur) {
                                        /* Success. */
                                        goto RETURN;
                                }
                        } while (brk_prev != (void *)-1);
                }
#endif
        }

        /*
         * Try to over-allocate, but allow the OS to place the allocation
         * anywhere.  Beware of size_t wrap-around.
         */
        if (size + chunk_size > size) {
                if ((ret = pages_map(NULL, size + chunk_size)) != NULL) {
                        size_t offset = CHUNK_ADDR2OFFSET(ret);

                        /*
                         * Success.  Clean up unneeded leading/trailing space.
                         */
                        if (offset != 0) {
                                /* Leading space. */
                                pages_unmap(ret, chunk_size - offset);

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

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

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

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

static void
chunk_dealloc(void *chunk, size_t size)
{
        size_t offset;
        chunk_node_t *node;

        assert(chunk != NULL);
        assert(CHUNK_ADDR2BASE(chunk) == chunk);
        assert(size != 0);
        assert(size % chunk_size == 0);

        malloc_mutex_lock(&chunks_mtx);
        for (offset = 0; offset < size; offset += chunk_size) {
                node = base_chunk_node_alloc();
                if (node == NULL)
                        break;

                /*
                 * Create a record of this chunk before deallocating it, so
                 * that the address range can be recycled if memory usage
                 * increases later on.
                 */
                node->chunk = (void *)((uintptr_t)chunk + (uintptr_t)offset);
                node->size = chunk_size;
                RB_INSERT(chunk_tree_s, &old_chunks, node);
        }

#ifdef USE_BRK
        if ((uintptr_t)chunk >= (uintptr_t)brk_base
            && (uintptr_t)chunk < (uintptr_t)brk_max)
                madvise(chunk, size, MADV_FREE);
        else
#endif
                pages_unmap(chunk, size);

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

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

static inline int
arena_chunk_comp(arena_chunk_t *a, arena_chunk_t *b)
{

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

        if ((uintptr_t)a < (uintptr_t)b)
                return (-1);
        else if (a == b)
                return (0);
        else
                return (1);
}

/* Generate red-black tree code for arena chunks. */
RB_GENERATE_STATIC(arena_chunk_tree_s, arena_chunk_s, link, arena_chunk_comp);

static inline void
arena_run_mask_free_set(arena_run_t *run, unsigned reg)
{
        unsigned elm, bit;

        assert(run->magic == ARENA_RUN_MAGIC);
        assert(reg < run->bin->nregs);

        elm = reg / (sizeof(unsigned) << 3);
        if (elm < run->regs_minelm)
                run->regs_minelm = elm;
        bit = reg - (elm * (sizeof(unsigned) << 3));
        assert((run->regs_mask[elm] & (1 << bit)) == 0);
        run->regs_mask[elm] |= (1 << bit);
}

static inline void
arena_run_mask_free_unset(arena_run_t *run, unsigned reg)
{
        unsigned elm, bit;

        assert(run->magic == ARENA_RUN_MAGIC);
        assert(reg < run->bin->nregs);

        elm = reg / (sizeof(unsigned) << 3);
        bit = reg - (elm * (sizeof(unsigned) << 3));
        assert((run->regs_mask[elm] & (1 << bit)) != 0);
        run->regs_mask[elm] ^= (1 << bit);
}

static inline unsigned
arena_run_search(arena_run_t *run)
{
        unsigned i, mask, bit;

        assert(run->magic == ARENA_RUN_MAGIC);

        for (i = run->regs_minelm; i < REGS_MASK_NELMS; i++) {
                mask = run->regs_mask[i];
                if (mask != 0) {
                        bit = ffs(mask);
                        if (bit != 0) {
                                /* Usable allocation found. */
                                return ((i * (sizeof(unsigned) << 3))
                                    + bit - 1);
                        }
                } else {
                        /*
                         * Make a note that nothing before this element
                         * contains a free region.
                         */
                        run->regs_minelm = i + 1;
                }
        }

        return (UINT_MAX);
}

static void
arena_run_split(arena_t *arena, arena_run_t *run, bool large, size_t size)
{
        arena_chunk_t *chunk;
        unsigned run_ind, map_offset, total_pages, need_pages;
        unsigned i, log2_run_pages, run_pages;

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(run);
        run_ind = (unsigned)(((uintptr_t)run - (uintptr_t)chunk)
            >> pagesize_2pow);
        assert(chunk->map[run_ind].free);
        total_pages = chunk->map[run_ind].npages;
        need_pages = (size >> pagesize_2pow);

#ifdef MALLOC_DEBUG
        for (i = 0; i < total_pages; i++) {
                assert(chunk->map[run_ind + i].free);
                assert(chunk->map[run_ind + i].large == false);
                assert(chunk->map[run_ind + i].npages == total_pages);
                assert(chunk->map[run_ind + i].pos == i);
        }
#endif

        /* Split enough pages from the front of run to fit allocation size. */
        map_offset = run_ind;
        for (i = 0; i < need_pages; i++) {
                chunk->map[map_offset + i].free = false;
                chunk->map[map_offset + i].large = large;
                chunk->map[map_offset + i].npages = need_pages;
                chunk->map[map_offset + i].pos = i;
        }

        /* Update map for trailing pages. */
        map_offset += need_pages;
        while (map_offset < run_ind + total_pages) {
                log2_run_pages = ffs(map_offset) - 1;
                run_pages = (1 << log2_run_pages);
                for (i = 0; i < run_pages; i++) {
                        chunk->map[map_offset + i].free = true;
                        chunk->map[map_offset + i].large = false;
                        chunk->map[map_offset + i].npages = run_pages;
                        chunk->map[map_offset + i].pos = i;
                }

                chunk->nfree_runs[log2_run_pages]++;

                map_offset += run_pages;
        }

        chunk->pages_used += (size >> pagesize_2pow);
}

static arena_chunk_t *
arena_chunk_alloc(arena_t *arena)
{
        arena_chunk_t *chunk;
        unsigned i, j, header_npages, pow2_header_npages, map_offset;
        unsigned log2_run_pages, run_pages;
        size_t header_size;

        chunk = (arena_chunk_t *)chunk_alloc(chunk_size);
        if (chunk == NULL)
                return (NULL);

        chunk->arena = arena;

        RB_INSERT(arena_chunk_tree_s, &arena->chunks, chunk);

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

        memset(&chunk->nfree_runs, 0, sizeof(chunk->nfree_runs));

        header_size = (size_t)((uintptr_t)&chunk->map[arena_chunk_maplen]
            - (uintptr_t)chunk);
        if (header_size % pagesize != 0) {
                /* Round up to the nearest page boundary. */
                header_size += pagesize - (header_size % pagesize);
        }

        header_npages = header_size / pagesize;
        pow2_header_npages = pow2_ceil(header_npages);

        /*
         * Iteratively mark runs as in use, until we've spoken for the entire
         * header.
         */
        map_offset = 0;
        for (i = 0; header_npages > 0; i++) {
                if ((pow2_header_npages >> i) <= header_npages) {
                        for (j = 0; j < (pow2_header_npages >> i); j++) {
                                chunk->map[map_offset + j].free = false;
                                chunk->map[map_offset + j].large = false;
                                chunk->map[map_offset + j].npages =
                                    (pow2_header_npages >> i);
                                chunk->map[map_offset + j].pos = j;
                        }
                        header_npages -= (pow2_header_npages >> i);
                        map_offset += (pow2_header_npages >> i);
                }
        }

        /*
         * Finish initializing map.  The chunk header takes up some space at
         * the beginning of the chunk, which we just took care of by
         * "allocating" the leading pages.
         */
        while (map_offset < (chunk_size / pagesize)) {
                log2_run_pages = ffs(map_offset) - 1;
                run_pages = (1 << log2_run_pages);
                for (i = 0; i < run_pages; i++) {
                        chunk->map[map_offset + i].free = true;
                        chunk->map[map_offset + i].large = false;
                        chunk->map[map_offset + i].npages = run_pages;
                        chunk->map[map_offset + i].pos = i;
                }

                chunk->nfree_runs[log2_run_pages]++;

                map_offset += run_pages;
        }

        return (chunk);
}

static void
arena_chunk_dealloc(arena_chunk_t *chunk)
{

        RB_REMOVE(arena_chunk_tree_s, &chunk->arena->chunks, chunk);

        chunk_dealloc((void *)chunk, chunk_size);
}

static void
arena_bin_run_refile(arena_t *arena, arena_bin_t *bin, arena_run_t *run,
    size_t size, bool promote)
{

        assert(bin == run->bin);

        /* Determine whether to promote or demote run. */
        if (promote) {
                /* Promote. */
                assert(run->free_min > run->nfree);
                assert(run->quartile < RUN_Q100);
                run->quartile++;
                if (run->quartile == RUN_Q75) {
                        /*
                         * Skip RUN_Q75 during promotion from RUN_Q50.
                         * Separate handling of RUN_Q75 and RUN_Q100 allows us
                         * to keep completely full runs in RUN_Q100, thus
                         * guaranteeing that runs in RUN_Q75 are only mostly
                         * full.  This provides a method for avoiding a linear
                         * search for non-full runs, which avoids some
                         * pathological edge cases.
                         */
                        run->quartile++;
                }
#ifdef MALLOC_STATS
                bin->stats.npromote++;
#endif
        } else {
                /* Demote. */
                assert(run->free_max < run->nfree);
                assert(run->quartile > RUN_QINIT);
                run->quartile--;
#ifdef MALLOC_STATS
                bin->stats.ndemote++;
#endif
        }

        /* Re-file run. */
        qr_remove(run, link);
        switch (run->quartile) {
                case RUN_QINIT:
#ifdef MALLOC_STATS
                        bin->stats.curruns--;
#endif
                        if (bin->runcur == run)
                                bin->runcur = NULL;
#ifdef MALLOC_DEBUG
                        run->magic = 0;
#endif
                        arena_run_dalloc(arena, run, bin->run_size);
                        break;
                case RUN_Q0:
                        qr_before_insert((arena_run_t *)&bin->runs0, run, link);
                        run->free_max = run->bin->nregs - 1;
                        run->free_min = (run->bin->nregs >> 1) + 1;
                        assert(run->nfree <= run->free_max);
                        assert(run->nfree >= run->free_min);
                        break;
                case RUN_Q25:
                        qr_before_insert((arena_run_t *)&bin->runs25, run,
                            link);
                        run->free_max = ((run->bin->nregs >> 2) * 3) - 1;
                        run->free_min = (run->bin->nregs >> 2) + 1;
                        assert(run->nfree <= run->free_max);
                        assert(run->nfree >= run->free_min);
                        break;
                case RUN_Q50:
                        qr_before_insert((arena_run_t *)&bin->runs50, run,
                            link);
                        run->free_max = (run->bin->nregs >> 1) - 1;
                        run->free_min = 1;
                        assert(run->nfree <= run->free_max);
                        assert(run->nfree >= run->free_min);
                        break;
                case RUN_Q75:
                        qr_before_insert((arena_run_t *)&bin->runs75, run,
                            link);
                        run->free_max = (run->bin->nregs >> 2) - 1;
                        run->free_min = 1;
                        assert(run->nfree <= run->free_max);
                        assert(run->nfree >= run->free_min);
                        break;
                case RUN_Q100:
                        assert(bin->runcur == run);
                        bin->runcur = NULL;
                        run->free_max = 0;
                        run->free_min = 0;
                        assert(run->nfree <= run->free_max);
                        assert(run->nfree >= run->free_min);
                        break;
                default:
                        assert(0);
                        break;
        }
}

static arena_run_t *
arena_run_alloc(arena_t *arena, bool large, size_t size)
{
        arena_run_t *run;
        unsigned min_ind, i, j;
        arena_chunk_t *chunk;
#ifndef NDEBUG
        int rep = 0;
#endif

        assert(size <= arena_maxclass);

AGAIN:
#ifndef NDEBUG
        rep++;
        assert(rep <= 2);
#endif

        /*
         * Search through arena's chunks in address order for a run that is
         * large enough.  Look for a precise fit, but do not pass up a chunk
         * that has a run which is large enough to split.
         */
        min_ind = ffs(size / pagesize) - 1;
        RB_FOREACH(chunk, arena_chunk_tree_s, &arena->chunks) {
                for (i = min_ind;
                    i < (opt_chunk_2pow - pagesize_2pow);
                    i++) {
                        if (chunk->nfree_runs[i] > 0) {
                                arena_chunk_map_t *map = chunk->map;

                                /* Scan chunk's map for free run. */
                                for (j = 0;
                                    j < arena_chunk_maplen;
                                    j += map[j].npages) {
                                        if (map[j].free
                                            && map[j].npages == (1 << i))
                {/*<----------------------------*/
                        run = (arena_run_t *)&((char *)chunk)[j
                            << pagesize_2pow];

                        assert(chunk->nfree_runs[i] > 0);
                        chunk->nfree_runs[i]--;

                        /* Update page map. */
                        arena_run_split(arena, run, large, size);

                        return (run);
                }/*---------------------------->*/
                                }
                                /* Not reached. */
                                assert(0);
                        }
                }
        }

        /* No usable runs.  Allocate a new chunk, then try again. */
        if (arena_chunk_alloc(arena) == NULL)
                return (NULL);
        goto AGAIN;
}

static void
arena_run_dalloc(arena_t *arena, arena_run_t *run, size_t size)
{
        arena_chunk_t *chunk;
        unsigned i, run_ind, buddy_ind, base_run_ind, run_pages, log2_run_pages;

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(run);
        run_ind = (unsigned)(((uintptr_t)run - (uintptr_t)chunk)
            >> pagesize_2pow);
        run_pages = (size >> pagesize_2pow);
        log2_run_pages = ffs(run_pages) - 1;
        assert(run_pages > 0);

        /* Subtract pages from count of pages used in chunk. */
        chunk->pages_used -= run_pages;

        /* Mark run as deallocated. */
        for (i = 0; i < run_pages; i++) {
                chunk->map[run_ind + i].free = true;
                chunk->map[run_ind + i].large = false;
                chunk->map[run_ind + i].npages = run_pages;
                chunk->map[run_ind + i].pos = i;
        }

        /*
         * Tell the kernel that we don't need the data in this run, but only if
         * requested via runtime configuration.
         */
        if (opt_hint) {
                madvise(run, size, MADV_FREE);
#ifdef MALLOC_STATS
                arena->stats.nmadvise += (size >> pagesize_2pow);
#endif
        }

        /*
         * Iteratively coalesce with buddies.  Conceptually, the buddy scheme
         * induces a tree on the set of pages.  If we know the number of pages
         * in the subtree rooted at the current node, we can quickly determine
         * whether a run is the left or right buddy, and then calculate the
         * buddy's index.
         */
        for (;
            (run_pages = (1 << log2_run_pages)) < arena_chunk_maplen;
            log2_run_pages++) {
                if (((run_ind >> log2_run_pages) & 1) == 0) {
                        /* Current run precedes its buddy. */
                        buddy_ind = run_ind + run_pages;
                        base_run_ind = run_ind;
                } else {
                        /* Current run follows its buddy. */
                        buddy_ind = run_ind - run_pages;
                        base_run_ind = buddy_ind;
                }

                if (chunk->map[buddy_ind].free == false
                    || chunk->map[buddy_ind].npages != run_pages)
                        break;

                assert(chunk->nfree_runs[log2_run_pages] > 0);
                chunk->nfree_runs[log2_run_pages]--;

                /* Coalesce. */
                for (i = 0; i < (run_pages << 1); i++) {
                        chunk->map[base_run_ind + i].npages = (run_pages << 1);
                        chunk->map[base_run_ind + i].pos = i;
                }

                /* Update run_ind to be the beginning of the coalesced run. */
                run_ind = base_run_ind;
        }

        chunk->nfree_runs[log2_run_pages]++;

        /* Free pages, to the extent possible. */
        if (chunk->pages_used == 0) {
                /* This chunk is completely unused now, so deallocate it. */
                arena_chunk_dealloc(chunk);
        }
}

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

        /* Look for a usable run. */
        if ((run = qr_next((arena_run_t *)&bin->runs50, link))
            != (arena_run_t *)&bin->runs50
            || (run = qr_next((arena_run_t *)&bin->runs25, link))
            != (arena_run_t *)&bin->runs25
            || (run = qr_next((arena_run_t *)&bin->runs0, link))
            != (arena_run_t *)&bin->runs0
            || (run = qr_next((arena_run_t *)&bin->runs75, link))
            != (arena_run_t *)&bin->runs75) {
                /* run is guaranteed to have available space. */
                qr_remove(run, link);
                return (run);
        }
        /* No existing runs have any space available. */

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

        /* Initialize run internals. */
        qr_new(run, link);
        run->bin = bin;

        for (i = 0; i < bin->nregs / (sizeof(unsigned) << 3); i++)
                run->regs_mask[i] = UINT_MAX;
        remainder = bin->nregs % (sizeof(unsigned) << 3);
        if (remainder != 0) {
                run->regs_mask[i] = (UINT_MAX >> ((sizeof(unsigned) << 3)
                    - remainder));
                i++;
        }
        for (; i < REGS_MASK_NELMS; i++)
                run->regs_mask[i] = 0;

        run->regs_minelm = 0;

        run->nfree = bin->nregs;
        run->quartile = RUN_QINIT;
        run->free_max = bin->nregs;
        run->free_min = ((bin->nregs >> 2) * 3) + 1;
#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,
    size_t size)
{
        void *ret;
        unsigned regind;

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

        regind = arena_run_search(run);
        assert(regind != UINT_MAX);
        assert(regind < bin->nregs);

        ret = (void *)&((char *)run)[bin->reg0_offset + (bin->reg_size
            * regind)];
        arena_run_mask_free_unset(run, regind);
        run->nfree--;
        if (run->nfree < run->free_min) {
                /* Promote run to higher fullness quartile. */
                arena_bin_run_refile(arena, bin, run, size, true);
        }

        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, size_t size)
{

        assert(bin->runcur == NULL || bin->runcur->quartile == RUN_Q100);

        bin->runcur = arena_bin_nonfull_run_get(arena, bin, size);
        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, size));
}

static void *
arena_malloc(arena_t *arena, size_t size)
{
        void *ret;

        assert(arena != NULL);
        assert(arena->magic == ARENA_MAGIC);
        assert(size != 0);
        assert(QUANTUM_CEILING(size) <= arena_maxclass);

        malloc_mutex_lock(&arena->mtx);
        if (size <= bin_maxclass) {
                arena_bin_t *bin;
                arena_run_t *run;

                /* Small allocation. */

                if (size < small_min) {
                        /* Tiny. */
                        size = pow2_ceil(size);
                        bin = &arena->bins[ffs(size >> (tiny_min_2pow + 1))];
#ifdef MALLOC_STATS
                        /*
                         * Bin calculation is always correct, but we may need to
                         * fix size for the purposes of stats accuracy.
                         */
                        if (size < (1 << tiny_min_2pow))
                                size = (1 << tiny_min_2pow);
#endif
                } else if (size <= small_max) {
                        /* Quantum-spaced. */
                        size = QUANTUM_CEILING(size);
                        bin = &arena->bins[ntbins + (size >> opt_quantum_2pow)
                            - 1];
                } else {
                        /* Sub-page. */
                        size = pow2_ceil(size);
                        bin = &arena->bins[ntbins + nqbins
                            + (ffs(size >> opt_small_max_2pow) - 2)];
                }
                assert(size == bin->reg_size);

                if ((run = bin->runcur) != NULL)
                        ret = arena_bin_malloc_easy(arena, bin, run, size);
                else
                        ret = arena_bin_malloc_hard(arena, bin, size);

#ifdef MALLOC_STATS
                bin->stats.nrequests++;
#endif
        } else {
                /* Medium allocation. */
                size = pow2_ceil(size);
                ret = (void *)arena_run_alloc(arena, true, size);
        }

#ifdef MALLOC_STATS
        if (ret != NULL)
                arena->stats.allocated += size;
#endif

        malloc_mutex_unlock(&arena->mtx);

        if (opt_junk && ret != NULL)
                memset(ret, 0xa5, size);
        else if (opt_zero && ret != NULL)
                memset(ret, 0, size);
        return (ret);
}

/* Return the size of the allocation pointed to by ptr. */
static size_t
arena_salloc(arena_t *arena, const void *ptr)
{
        size_t ret;
        arena_chunk_t *chunk;
        uint32_t pageind;
        arena_chunk_map_t *mapelm;

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

        malloc_mutex_lock(&arena->mtx);
        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
        pageind = (((uintptr_t)ptr - (uintptr_t)chunk) >> pagesize_2pow);
        mapelm = &chunk->map[pageind];
        assert(mapelm->free == false);
        if (mapelm->large == false) {
                arena_run_t *run;

                pageind -= mapelm->pos;
                mapelm = &chunk->map[pageind];

                run = (arena_run_t *)&((char *)chunk)[pageind << pagesize_2pow];
                assert(run->magic == ARENA_RUN_MAGIC);
                ret = run->bin->reg_size;
        } else
                ret = mapelm->npages << pagesize_2pow;

        malloc_mutex_unlock(&arena->mtx);

        return (ret);
}

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

        /* Avoid moving the allocation if the size class would not change. */
        if (size < small_min) {
                if (oldsize < small_min &&
                    ffs(pow2_ceil(size) >> (tiny_min_2pow + 1))
                    == ffs(pow2_ceil(oldsize) >> (tiny_min_2pow + 1)))
                        goto IN_PLACE;
        } else if (size <= small_max) {
                if (oldsize >= small_min && oldsize <= small_max &&
                    (QUANTUM_CEILING(size) >> opt_quantum_2pow)
                    == (QUANTUM_CEILING(oldsize) >> opt_quantum_2pow))
                        goto IN_PLACE;
        } else {
                if (oldsize > small_max &&
                    pow2_ceil(size) == pow2_ceil(oldsize))
                        goto IN_PLACE;
        }

        /*
         * 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 = arena_malloc(arena, size);
        if (ret == NULL)
                return (NULL);

        if (size < oldsize)
                memcpy(ret, ptr, size);
        else
                memcpy(ret, ptr, oldsize);
        idalloc(ptr);
        return (ret);
IN_PLACE:
        if (opt_junk && size < oldsize)
                memset(&((char *)ptr)[size], 0x5a, oldsize - size);
        else if (opt_zero && size > oldsize)
                memset(&((char *)ptr)[size], 0, size - oldsize);
        return (ptr);
}

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

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

        malloc_mutex_lock(&arena->mtx);

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
        assert(chunk->arena == arena);
        pageind = (((uintptr_t)ptr - (uintptr_t)chunk) >> pagesize_2pow);
        mapelm = &chunk->map[pageind];
        assert(mapelm->free == false);
        if (mapelm->large == false) {
                arena_run_t *run;
                unsigned regind;

                /* Small allocation. */

                pageind -= mapelm->pos;
                mapelm = &chunk->map[pageind];

                run = (arena_run_t *)&((char *)chunk)[pageind << pagesize_2pow];
                assert(run->magic == ARENA_RUN_MAGIC);
                size = run->bin->reg_size;

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

                regind = (unsigned)(((uintptr_t)ptr
                    - (uintptr_t)&((char *)run)[run->bin->reg0_offset])
                    / run->bin->reg_size);
                arena_run_mask_free_set(run, regind);
                run->nfree++;
                if (run->nfree > run->free_max) {
                        /* Demote run to lower fullness quartile. */
                        arena_bin_run_refile(arena, run->bin, run, size, false);
                }
        } else {
                /* Medium allocation. */

                size = mapelm->npages << pagesize_2pow;

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

                arena_run_dalloc(arena, (arena_run_t *)ptr, size);
        }

#ifdef MALLOC_STATS
        arena->stats.allocated -= size;
#endif

        malloc_mutex_unlock(&arena->mtx);
}

static bool
arena_new(arena_t *arena)
{
        unsigned i;
        arena_bin_t *bin;
        size_t pow2_size, run_size;

        malloc_mutex_init(&arena->mtx);

#ifdef MALLOC_STATS
        memset(&arena->stats, 0, sizeof(arena_stats_t));
#endif

        /* Initialize chunks. */
        RB_INIT(&arena->chunks);

        /* Initialize bins. */

        /* (2^n)-spaced tiny bins. */
        for (i = 0; i < ntbins; i++) {
                bin = &arena->bins[i];
                bin->runcur = NULL;
                qr_new((arena_run_t *)&bin->runs0, link);
                qr_new((arena_run_t *)&bin->runs25, link);
                qr_new((arena_run_t *)&bin->runs50, link);
                qr_new((arena_run_t *)&bin->runs75, link);

                bin->reg_size = (1 << (tiny_min_2pow + i));

                /*
                 * Calculate how large of a run to allocate.  Make sure that at
                 * least RUN_MIN_REGS regions fit in the run.
                 */
                run_size = bin->reg_size << RUN_MIN_REGS_2POW;
                if (run_size < pagesize)
                        run_size = pagesize;
                if (run_size > (pagesize << RUN_MAX_PAGES_2POW))
                        run_size = (pagesize << RUN_MAX_PAGES_2POW);
                if (run_size > arena_maxclass)
                        run_size = arena_maxclass;
                bin->run_size = run_size;

                assert(run_size >= sizeof(arena_run_t));
                bin->nregs = (run_size - sizeof(arena_run_t)) / bin->reg_size;
                if (bin->nregs > REGS_MASK_NELMS * (sizeof(unsigned) << 3)) {
                        /* Take care not to overflow regs_mask. */
                        bin->nregs = REGS_MASK_NELMS * (sizeof(unsigned) << 3);
                }
                bin->reg0_offset = run_size - (bin->nregs * bin->reg_size);

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

        /* Quantum-spaced bins. */
        for (; i < ntbins + nqbins; i++) {
                bin = &arena->bins[i];
                bin->runcur = NULL;
                qr_new((arena_run_t *)&bin->runs0, link);
                qr_new((arena_run_t *)&bin->runs25, link);
                qr_new((arena_run_t *)&bin->runs50, link);
                qr_new((arena_run_t *)&bin->runs75, link);

                bin->reg_size = quantum * (i - ntbins + 1);

                /*
                 * Calculate how large of a run to allocate.  Make sure that at
                 * least RUN_MIN_REGS regions fit in the run.
                 */
                pow2_size = pow2_ceil(quantum * (i - ntbins + 1));
                run_size = (pow2_size << RUN_MIN_REGS_2POW);
                if (run_size < pagesize)
                        run_size = pagesize;
                if (run_size > (pagesize << RUN_MAX_PAGES_2POW))
                        run_size = (pagesize << RUN_MAX_PAGES_2POW);
                if (run_size > arena_maxclass)
                        run_size = arena_maxclass;
                bin->run_size = run_size;

                bin->nregs = (run_size - sizeof(arena_run_t)) / bin->reg_size;
                assert(bin->nregs <= REGS_MASK_NELMS * (sizeof(unsigned) << 3));
                bin->reg0_offset = run_size - (bin->nregs * bin->reg_size);

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

        /* (2^n)-spaced sub-page bins. */
        for (; i < ntbins + nqbins + nsbins; i++) {
                bin = &arena->bins[i];
                bin->runcur = NULL;
                qr_new((arena_run_t *)&bin->runs0, link);
                qr_new((arena_run_t *)&bin->runs25, link);
                qr_new((arena_run_t *)&bin->runs50, link);
                qr_new((arena_run_t *)&bin->runs75, link);

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

                /*
                 * Calculate how large of a run to allocate.  Make sure that at
                 * least RUN_MIN_REGS regions fit in the run.
                 */
                run_size = bin->reg_size << RUN_MIN_REGS_2POW;
                if (run_size < pagesize)
                        run_size = pagesize;
                if (run_size > (pagesize << RUN_MAX_PAGES_2POW))
                        run_size = (pagesize << RUN_MAX_PAGES_2POW);
                if (run_size > arena_maxclass)
                        run_size = arena_maxclass;
                bin->run_size = run_size;

                bin->nregs = (run_size - sizeof(arena_run_t)) / bin->reg_size;
                assert(bin->nregs <= REGS_MASK_NELMS * (sizeof(unsigned) << 3));
                bin->reg0_offset = run_size - (bin->nregs * bin->reg_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) * (ntbins + nqbins + nsbins - 1)));
        if (ret != NULL && arena_new(ret) == 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_printf("%s: (malloc) Error initializing arena\n",
            _getprogname());
        if (opt_abort)
                abort();

        return (arenas[0]);
}

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

/*
 * 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
        ret = arenas_map;
        if (ret == NULL)
                ret = choose_arena_hard();
#else
        if (__isthreaded) {
                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
                 * 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_mutex_lock(&arenas_mtx);
                        if (arenas[ind] == NULL)
                                ret = arenas_extend((unsigned)ind);
                        else
                                ret = arenas[ind];
                        malloc_mutex_unlock(&arenas_mtx);
                }
        } else
                ret = arenas[0];
#endif

        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;

        /* Assign one of the arenas to this thread, in a round-robin fashion. */
        if (__isthreaded) {
                malloc_mutex_lock(&arenas_mtx);
                ret = arenas[next_arena];
                if (ret == NULL)
                        ret = arenas_extend(next_arena);
                next_arena = (next_arena + 1) % narenas;
                malloc_mutex_unlock(&arenas_mtx);
        } else
                ret = arenas[0];
        arenas_map = ret;

        return (ret);
}
#endif

static void *
huge_malloc(size_t size)
{
        void *ret;
        size_t chunk_size;
        chunk_node_t *node;

        /* Allocate a chunk for this request. */

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

        /* Allocate a chunk node with which to track the chunk. */
        node = base_chunk_node_alloc();
        if (node == NULL)
                return (NULL);

        ret = chunk_alloc(chunk_size);
        if (ret == NULL) {
                base_chunk_node_dealloc(node);
                return (NULL);
        }

        /* Insert node into chunks. */
        node->chunk = ret;
        node->size = chunk_size;

        malloc_mutex_lock(&chunks_mtx);
        RB_INSERT(chunk_tree_s, &huge, node);
#ifdef MALLOC_STATS
        huge_nmalloc++;
        huge_allocated += chunk_size;
#endif
        malloc_mutex_unlock(&chunks_mtx);

        if (opt_junk && ret != NULL)
                memset(ret, 0xa5, chunk_size);
        else if (opt_zero && ret != NULL)
                memset(ret, 0, chunk_size);

        return (ret);
}

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

        /* Avoid moving the allocation if the size class would not change. */
        if (oldsize > arena_maxclass &&
            CHUNK_CEILING(size) == CHUNK_CEILING(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);
        if (ret == NULL)
                return (NULL);

        if (CHUNK_ADDR2BASE(ptr) == ptr) {
                /* The old allocation is a chunk. */
                if (size < oldsize)
                        memcpy(ret, ptr, size);
                else
                        memcpy(ret, ptr, oldsize);
        } else {
                /* The old allocation is a region. */
                assert(oldsize < size);
                memcpy(ret, ptr, oldsize);
        }
        idalloc(ptr);
        return (ret);
}

static void
huge_dalloc(void *ptr)
{
        chunk_node_t key;
        chunk_node_t *node;

        malloc_mutex_lock(&chunks_mtx);

        /* Extract from tree of huge allocations. */
        key.chunk = ptr;
        node = RB_FIND(chunk_tree_s, &huge, &key);
        assert(node != NULL);
        assert(node->chunk == ptr);
        RB_REMOVE(chunk_tree_s, &huge, node);

#ifdef MALLOC_STATS
        /* Update counters. */
        huge_ndalloc++;
        huge_allocated -= node->size;
#endif

        malloc_mutex_unlock(&chunks_mtx);

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

        base_chunk_node_dealloc(node);
}

static void *
imalloc(arena_t *arena, size_t size)
{
        void *ret;

        assert(arena != NULL);
        assert(arena->magic == ARENA_MAGIC);
        assert(size != 0);

        if (size <= arena_maxclass)
                ret = arena_malloc(arena, size);
        else
                ret = huge_malloc(size);

#ifdef MALLOC_STATS
        malloc_mutex_lock(&arena->mtx);
        arena->stats.nmalloc++;
        malloc_mutex_unlock(&arena->mtx);
#endif

        return (ret);
}

static void *
ipalloc(arena_t *arena, size_t alignment, size_t size)
{
        void *ret;
        size_t pow2_size;

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

        /*
         * Round up to the nearest power of two that is >= alignment and
         * >= size.
         */
        if (size > alignment)
                pow2_size = pow2_ceil(size);
        else
                pow2_size = alignment;
        pow2_size = QUANTUM_CEILING(pow2_size);
        if (pow2_size < size) {
                /* size_t overflow. */
                return (NULL);
        }

        if (pow2_size <= arena_maxclass)
                ret = arena_malloc(arena, pow2_size);
        else {
                if (alignment <= chunk_size)
                        ret = huge_malloc(size);
                else {
                        size_t chunksize, alloc_size, offset;
                        chunk_node_t *node;

                        /*
                         * 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.
                         */

                        chunksize = CHUNK_CEILING(size);

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

                        /*
                         * Allocate a chunk node with which to track the chunk.
                         */
                        node = base_chunk_node_alloc();
                        if (node == NULL)
                                return (NULL);

                        ret = chunk_alloc(alloc_size);
                        if (ret == NULL) {
                                base_chunk_node_dealloc(node);
                                return (NULL);
                        }

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

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

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

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

                        /* Insert node into chunks. */
                        node->chunk = ret;
                        node->size = chunksize;

                        malloc_mutex_lock(&chunks_mtx);
                        RB_INSERT(chunk_tree_s, &huge, node);
#ifdef MALLOC_STATS
                        huge_allocated += size;
#endif
                        malloc_mutex_unlock(&chunks_mtx);

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

#ifdef MALLOC_STATS
        malloc_mutex_lock(&arena->mtx);
        arena->stats.npalloc++;
        malloc_mutex_unlock(&arena->mtx);
#endif
        assert(((uintptr_t)ret & (alignment - 1)) == 0);
        return (ret);
}

static void *
icalloc(arena_t *arena, size_t size)
{
        void *ret;

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

        if (size <= arena_maxclass) {
                ret = arena_malloc(arena, size);
                if (ret == NULL)
                        return (NULL);
                memset(ret, 0, size);
        } else {
                /*
                 * The virtual memory system provides zero-filled pages, so
                 * there is no need to do so manually, unless opt_junk is
                 * enabled, in which case huge_malloc() fills huge allocations
                 * with junk.
                 */
                ret = huge_malloc(size);
                if (ret == NULL)
                        return (NULL);

                if (opt_junk)
                        memset(ret, 0, size);
#ifdef USE_BRK
                else if ((uintptr_t)ret >= (uintptr_t)brk_base
                    && (uintptr_t)ret < (uintptr_t)brk_max) {
                        /*
                         * This may be a re-used brk chunk.  Therefore, zero
                         * the memory.
                         */
                        memset(ret, 0, size);
                }
#endif
        }

#ifdef MALLOC_STATS
        malloc_mutex_lock(&arena->mtx);
        arena->stats.ncalloc++;
        malloc_mutex_unlock(&arena->mtx);
#endif

        return (ret);
}

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

        assert(ptr != NULL);
        assert(ptr != &nil);

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

                ret = arena_salloc(chunk->arena, ptr);
        } else {
                chunk_node_t *node, key;

                /* Chunk (huge allocation). */

                malloc_mutex_lock(&chunks_mtx);

                /* Extract from tree of huge allocations. */
                key.chunk = (void *)ptr;
                node = RB_FIND(chunk_tree_s, &huge, &key);
                assert(node != NULL);

                ret = node->size;

                malloc_mutex_unlock(&chunks_mtx);
        }

        return (ret);
}

static void *
iralloc(arena_t *arena, void *ptr, size_t size)
{
        void *ret;
        size_t oldsize;

        assert(arena != NULL);
        assert(arena->magic == ARENA_MAGIC);
        assert(ptr != NULL);
        assert(ptr != &nil);
        assert(size != 0);

        oldsize = isalloc(ptr);

        if (size <= arena_maxclass)
                ret = arena_ralloc(arena, ptr, size, oldsize);
        else
                ret = huge_ralloc(ptr, size, oldsize);

#ifdef MALLOC_STATS
        malloc_mutex_lock(&arena->mtx);
        arena->stats.nralloc++;
        malloc_mutex_unlock(&arena->mtx);
#endif
        return (ret);
}

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

        assert(ptr != NULL);
        assert(ptr != &nil);

        chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
        if (chunk != ptr) {
                /* Region. */
#ifdef MALLOC_STATS
                malloc_mutex_lock(&chunk->arena->mtx);
                chunk->arena->stats.ndalloc++;
                malloc_mutex_unlock(&chunk->arena->mtx);
#endif
                arena_dalloc(chunk->arena, ptr);
        } else
                huge_dalloc(ptr);
}

static void
malloc_print_stats(void)
{

        if (opt_print_stats) {
                malloc_printf("___ Begin malloc statistics ___\n");
                malloc_printf("Number of CPUs: %u\n", ncpus);
                malloc_printf("Number of arenas: %u\n", narenas);
                malloc_printf("Chunk size: %zu (2^%zu)\n", chunk_size,
                    opt_chunk_2pow);
                malloc_printf("Quantum size: %zu (2^%zu)\n", quantum,
                    opt_quantum_2pow);
                malloc_printf("Max small size: %zu\n", small_max);
                malloc_printf("Pointer size: %u\n", sizeof(void *));
                malloc_printf("Assertions %s\n",
#ifdef NDEBUG
                    "disabled"
#else
                    "enabled"
#endif
                    );

#ifdef MALLOC_STATS

                {
                        size_t allocated, total;
                        unsigned i;
                        arena_t *arena;

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

                        /* arenas. */
                        for (i = 0, allocated = 0; i < narenas; i++) {
                                if (arenas[i] != NULL) {
                                        malloc_mutex_lock(&arenas[i]->mtx);
                                        allocated += arenas[i]->stats.allocated;
                                        malloc_mutex_unlock(&arenas[i]->mtx);
                                }
                        }

                        /* huge. */
                        malloc_mutex_lock(&chunks_mtx);
                        allocated += huge_allocated;
                        total = stats_chunks.curchunks * chunk_size;
                        malloc_mutex_unlock(&chunks_mtx);

                        malloc_printf("Allocated: %zu, space used: %zu\n",
                            allocated, total);

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

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

                                malloc_printf("\nchunks:\n");
                                malloc_printf(" %13s%13s%13s\n", "nchunks",
                                    "highchunks", "curchunks");
                                malloc_printf(" %13llu%13lu%13lu\n",
                                    chunks_stats.nchunks,
                                    chunks_stats.highchunks,
                                    chunks_stats.curchunks);
                        }

                        /* Print chunk stats. */
                        malloc_printf("\nhuge:\n");
                        malloc_printf("%12s %12s %12s\n",
                            "nmalloc", "ndalloc", "allocated");
                        malloc_printf("%12llu %12llu %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] statistics:\n", i);
                                        malloc_mutex_lock(&arena->mtx);
                                        stats_print(arena);
                                        malloc_mutex_unlock(&arena->mtx);
                                }
                        }
                }
#endif /* #ifdef MALLOC_STATS */
                malloc_printf("--- End malloc statistics ---\n");
        }
}

/*
 * FreeBSD's pthreads implementation calls malloc(3), so the malloc
 * implementation has to take pains to avoid infinite recursion during
 * initialization.
 *
 * atomic_init_start() returns true if it started initializing.  In that case,
 * the caller must also call atomic_init_finish(), just before returning to its
 * caller.  This delayed finalization of initialization is critical, since
 * otherwise choose_arena() has no way to know whether it's safe to call
 * _pthread_self().
 */
static inline bool
malloc_init(void)
{

        /*
         * We always initialize before threads are created, since any thread
         * creation first triggers allocations.
         */
        assert(__isthreaded == 0 || malloc_initialized);

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

        return (false);
}

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

        /* Get number of CPUs. */
        {
                int mib[2];
                size_t len;

                mib[0] = CTL_HW;
                mib[1] = HW_NCPU;
                len = sizeof(ncpus);
                if (sysctl(mib, 2, &ncpus, &len, (void *) 0, 0) == -1) {
                        /* Error. */
                        ncpus = 1;
                }
        }

        /* Get page size. */
        {
                long result;

                result = sysconf(_SC_PAGESIZE);
                assert(result != -1);
                pagesize = (unsigned) result;

                /*
                 * We assume that pagesize is a power of 2 when calculating
                 * pagesize_2pow.
                 */
                assert(((result - 1) & result) == 0);
                pagesize_2pow = ffs(result) - 1;
        }

        for (i = 0; i < 3; i++) {
                /* 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);
                }

                for (j = 0; opts[j] != '\0'; j++) {
                        switch (opts[j]) {
                        case 'a':
                                opt_abort = false;
                                break;
                        case 'A':
                                opt_abort = true;
                                break;
                        case 'h':
                                opt_hint = false;
                                break;
                        case 'H':
                                opt_hint = true;
                                break;
                        case 'j':
                                opt_junk = false;
                                break;
                        case 'J':
                                opt_junk = true;
                                break;
                        case 'k':
                                /*
                                 * Run fullness quartile limits don't have
                                 * enough resolution if there are too few
                                 * regions for the largest bin size classes.
                                 */
                                if (opt_chunk_2pow > pagesize_2pow + 3)
                                        opt_chunk_2pow--;
                                break;
                        case 'K':
                                if (opt_chunk_2pow < CHUNK_2POW_MAX)
                                        opt_chunk_2pow++;
                                break;
                        case 'n':
                                opt_narenas_lshift--;
                                break;
                        case 'N':
                                opt_narenas_lshift++;
                                break;
                        case 'p':
                                opt_print_stats = false;
                                break;
                        case 'P':
                                opt_print_stats = true;
                                break;
                        case 'q':
                                if (opt_quantum_2pow > QUANTUM_2POW_MIN)
                                        opt_quantum_2pow--;
                                break;
                        case 'Q':
                                if (opt_quantum_2pow < pagesize_2pow - 1)
                                        opt_quantum_2pow++;
                                break;
                        case 's':
                                if (opt_small_max_2pow > QUANTUM_2POW_MIN)
                                        opt_small_max_2pow--;
                                break;
                        case 'S':
                                if (opt_small_max_2pow < pagesize_2pow - 1)
                                        opt_small_max_2pow++;
                                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:
                                malloc_printf("%s: (malloc) Unsupported"
                                    " character in malloc options: '%c'\n",
                                    _getprogname(), opts[j]);
                        }
                }
        }

        /* Take care to call atexit() only once. */
        if (opt_print_stats) {
                /* Print statistics at exit. */
                atexit(malloc_print_stats);
        }

        /* Set variables according to the value of opt_small_max_2pow. */
        if (opt_small_max_2pow < opt_quantum_2pow)
                opt_small_max_2pow = opt_quantum_2pow;
        small_max = (1 << opt_small_max_2pow);

        /* Set bin-related variables. */
        bin_maxclass = (pagesize >> 1);
        if (pagesize_2pow > RUN_MIN_REGS_2POW + 1)
                tiny_min_2pow = pagesize_2pow - (RUN_MIN_REGS_2POW + 1);
        else
                tiny_min_2pow = 1;
        assert(opt_quantum_2pow >= tiny_min_2pow);
        ntbins = opt_quantum_2pow - tiny_min_2pow;
        assert(ntbins <= opt_quantum_2pow);
        nqbins = (small_max >> opt_quantum_2pow);
        nsbins = pagesize_2pow - opt_small_max_2pow - 1;

        /* Set variables according to the value of opt_quantum_2pow. */
        quantum = (1 << opt_quantum_2pow);
        quantum_mask = quantum - 1;
        if (ntbins > 0)
                small_min = (quantum >> 1) + 1;
        else
                small_min = 1;
        assert(small_min <= quantum);

        /* Set variables according to the value of opt_chunk_2pow. */
        chunk_size = (1 << opt_chunk_2pow);
        chunk_size_mask = chunk_size - 1;
        arena_chunk_maplen = (1 << (opt_chunk_2pow - pagesize_2pow));
        arena_maxclass = (chunk_size >> 1);

        UTRACE(0, 0, 0);

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

        /* Various sanity checks that regard configuration. */
        assert(quantum >= sizeof(void *));
        assert(quantum <= pagesize);
        assert(chunk_size >= pagesize);
        assert(quantum * 4 <= chunk_size);

        /* Initialize chunks data. */
        malloc_mutex_init(&chunks_mtx);
        RB_INIT(&huge);
#ifdef USE_BRK
        brk_base = sbrk(0);
        brk_prev = brk_base;
        brk_max = (void *)((uintptr_t)brk_base + MAXDSIZ);
#endif
#ifdef MALLOC_STATS
        huge_nmalloc = 0;
        huge_ndalloc = 0;
        huge_allocated = 0;
#endif
        RB_INIT(&old_chunks);

        /* Initialize base allocation data structures. */
#ifdef MALLOC_STATS
        base_total = 0;
#endif
#ifdef USE_BRK
        /*
         * Do special brk allocation here, since the base chunk doesn't really
         * need to be chunk-aligned.
         */
        {
                void *brk_cur;
                intptr_t incr;

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

                        /*
                         * Calculate how much padding is necessary to
                         * chunk-align the end of brk.  Don't worry about
                         * brk_cur not being chunk-aligned though.
                         */
                        incr = (intptr_t)chunk_size
                            - (intptr_t)CHUNK_ADDR2OFFSET(brk_cur);

                        brk_prev = sbrk(incr);
                        if (brk_prev == brk_cur) {
                                /* Success. */
                                break;
                        }
                } while (brk_prev != (void *)-1);

                base_chunk = brk_cur;
                base_next_addr = base_chunk;
                base_past_addr = (void *)((uintptr_t)base_chunk + incr);
#ifdef MALLOC_STATS
                base_total += incr;
                stats_chunks.nchunks = 1;
                stats_chunks.curchunks = 1;
                stats_chunks.highchunks = 1;
#endif
        }
#else
        /*
         * The first base chunk will be allocated when needed by base_alloc().
         */
        base_chunk = NULL;
        base_next_addr = NULL;
        base_past_addr = NULL;
#endif
        base_chunk_nodes = NULL;
        malloc_mutex_init(&base_mtx);

        if (ncpus > 1) {
                /*
                 * For SMP systems, create four times as many arenas as there
                 * are CPUs by default.
                 */
                opt_narenas_lshift += 2;
        }

        /* Determine how many arenas to use. */
        narenas = ncpus;
        if (opt_narenas_lshift > 0)
                narenas <<= opt_narenas_lshift;

#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 i, 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) / sizeof(unsigned);
                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)
                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
         * arena_choose_hard().
         */
        arenas_extend(0);
        if (arenas[0] == NULL)
                return (true);

        malloc_mutex_init(&arenas_mtx);

        malloc_initialized = true;
        return (false);
}

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

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

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

        if (size == 0) {
                if (opt_sysv == false)
                        ret = &nil;
                else
                        ret = NULL;
                goto RETURN;
        }

        arena = choose_arena();
        if (arena != NULL)
                ret = imalloc(arena, size);
        else
                ret = NULL;

RETURN:
        if (ret == NULL) {
                if (opt_xmalloc) {
                        malloc_printf("%s: (malloc) Error in malloc(%zu):"
                            " out of memory\n", _getprogname(), size);
                        abort();
                }
                errno = ENOMEM;
        }

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

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

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

                arena = choose_arena();
                if (arena != NULL)
                        result = ipalloc(arena, alignment, size);
                else
                        result = NULL;
        }

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

        *memptr = result;
        ret = 0;

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

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

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

        if (num * size == 0) {
                if (opt_sysv == false)
                        ret = &nil;
                else
                        ret = NULL;
                goto RETURN;
        } else if ((num * size) / size != num) {
                /* size_t overflow. */
                ret = NULL;
                goto RETURN;
        }

        arena = choose_arena();
        if (arena != NULL)
                ret = icalloc(arena, num * size);
        else
                ret = NULL;

RETURN:
        if (ret == NULL) {
                if (opt_xmalloc) {
                        malloc_printf("%s: (malloc) Error in"
                            " calloc(%zu, %zu): out of memory\n",
                            _getprogname(), num, size);
                        abort();
                }
                errno = ENOMEM;
        }

        UTRACE(0, num * size, ret);
        return (ret);
}

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

        if (size != 0) {
                arena_t *arena;

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

                        arena = choose_arena();
                        if (arena != NULL)
                                ret = iralloc(arena, ptr, size);
                        else
                                ret = NULL;

                        if (ret == NULL) {
                                if (opt_xmalloc) {
                                        malloc_printf("%s: (malloc) Error in"
                                            " ralloc(%p, %zu): out of memory\n",
                                            _getprogname(), ptr, size);
                                        abort();
                                }
                                errno = ENOMEM;
                        }
                } else {
                        if (malloc_init())
                                ret = NULL;
                        else {
                                arena = choose_arena();
                                if (arena != NULL)
                                        ret = imalloc(arena, size);
                                else
                                        ret = NULL;
                        }

                        if (ret == NULL) {
                                if (opt_xmalloc) {
                                        malloc_printf("%s: (malloc) Error in"
                                            " ralloc(%p, %zu): out of memory\n",
                                            _getprogname(), ptr, size);
                                        abort();
                                }
                                errno = ENOMEM;
                        }
                }
        } else {
                if (ptr != &nil && ptr != NULL)
                        idalloc(ptr);

                ret = &nil;
        }

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

void
free(void *ptr)
{

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

                idalloc(ptr);
        }
}

/*
 * End malloc(3)-compatible functions.
 */
/******************************************************************************/
/*
 * Begin library-private functions, 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_mutex_lock(&arenas_mtx);
        for (i = 0; i < narenas; i++) {
                if (arenas[i] != NULL)
                        malloc_mutex_lock(&arenas[i]->mtx);
        }
        malloc_mutex_unlock(&arenas_mtx);

        malloc_mutex_lock(&base_mtx);

        malloc_mutex_lock(&chunks_mtx);
}

void
_malloc_postfork(void)
{
        unsigned i;

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

        malloc_mutex_unlock(&chunks_mtx);

        malloc_mutex_unlock(&base_mtx);

        malloc_mutex_lock(&arenas_mtx);
        for (i = 0; i < narenas; i++) {
                if (arenas[i] != NULL)
                        malloc_mutex_unlock(&arenas[i]->mtx);
        }
        malloc_mutex_unlock(&arenas_mtx);
}

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