Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

[FreeBSD/stable/10.git] / sys / vm / uma_core.c

/*-
 * Copyright (c) 2002-2005, 2009, 2013 Jeffrey Roberson <jeff@FreeBSD.org>
 * Copyright (c) 2004, 2005 Bosko Milekic <bmilekic@FreeBSD.org>
 * Copyright (c) 2004-2006 Robert N. M. Watson
 * 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 unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, 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 AUTHOR ``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 AUTHOR 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.
 */

/*
 * uma_core.c  Implementation of the Universal Memory allocator
 *
 * This allocator is intended to replace the multitude of similar object caches
 * in the standard FreeBSD kernel.  The intent is to be flexible as well as
 * effecient.  A primary design goal is to return unused memory to the rest of
 * the system.  This will make the system as a whole more flexible due to the
 * ability to move memory to subsystems which most need it instead of leaving
 * pools of reserved memory unused.
 *
 * The basic ideas stem from similar slab/zone based allocators whose algorithms
 * are well known.
 *
 */

/*
 * TODO:
 *      - Improve memory usage for large allocations
 *      - Investigate cache size adjustments
 */

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

/* I should really use ktr.. */
/*
#define UMA_DEBUG 1
#define UMA_DEBUG_ALLOC 1
#define UMA_DEBUG_ALLOC_1 1
*/

#include "opt_ddb.h"
#include "opt_param.h"
#include "opt_vm.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bitset.h>
#include <sys/kernel.h>
#include <sys/types.h>
#include <sys/queue.h>
#include <sys/malloc.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/sysctl.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/sbuf.h>
#include <sys/smp.h>
#include <sys/vmmeter.h>

#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_param.h>
#include <vm/vm_map.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
#include <vm/uma_int.h>
#include <vm/uma_dbg.h>

#include <ddb/ddb.h>

#ifdef DEBUG_MEMGUARD
#include <vm/memguard.h>
#endif

/*
 * This is the zone and keg from which all zones are spawned.  The idea is that
 * even the zone & keg heads are allocated from the allocator, so we use the
 * bss section to bootstrap us.
 */
static struct uma_keg masterkeg;
static struct uma_zone masterzone_k;
static struct uma_zone masterzone_z;
static uma_zone_t kegs = &masterzone_k;
static uma_zone_t zones = &masterzone_z;

/* This is the zone from which all of uma_slab_t's are allocated. */
static uma_zone_t slabzone;
static uma_zone_t slabrefzone;  /* With refcounters (for UMA_ZONE_REFCNT) */

/*
 * The initial hash tables come out of this zone so they can be allocated
 * prior to malloc coming up.
 */
static uma_zone_t hashzone;

/* The boot-time adjusted value for cache line alignment. */
int uma_align_cache = 64 - 1;

static MALLOC_DEFINE(M_UMAHASH, "UMAHash", "UMA Hash Buckets");

/*
 * Are we allowed to allocate buckets?
 */
static int bucketdisable = 1;

/* Linked list of all kegs in the system */
static LIST_HEAD(,uma_keg) uma_kegs = LIST_HEAD_INITIALIZER(uma_kegs);

/* This mutex protects the keg list */
static struct mtx_padalign uma_mtx;

/* Linked list of boot time pages */
static LIST_HEAD(,uma_slab) uma_boot_pages =
    LIST_HEAD_INITIALIZER(uma_boot_pages);

/* This mutex protects the boot time pages list */
static struct mtx_padalign uma_boot_pages_mtx;

/* Is the VM done starting up? */
static int booted = 0;
#define UMA_STARTUP     1
#define UMA_STARTUP2    2

/* Maximum number of allowed items-per-slab if the slab header is OFFPAGE */
static const u_int uma_max_ipers = SLAB_SETSIZE;

/*
 * Only mbuf clusters use ref zones.  Just provide enough references
 * to support the one user.  New code should not use the ref facility.
 */
static const u_int uma_max_ipers_ref = PAGE_SIZE / MCLBYTES;

/*
 * This is the handle used to schedule events that need to happen
 * outside of the allocation fast path.
 */
static struct callout uma_callout;
#define UMA_TIMEOUT     20              /* Seconds for callout interval. */

/*
 * This structure is passed as the zone ctor arg so that I don't have to create
 * a special allocation function just for zones.
 */
struct uma_zctor_args {
        const char *name;
        size_t size;
        uma_ctor ctor;
        uma_dtor dtor;
        uma_init uminit;
        uma_fini fini;
        uma_import import;
        uma_release release;
        void *arg;
        uma_keg_t keg;
        int align;
        uint32_t flags;
};

struct uma_kctor_args {
        uma_zone_t zone;
        size_t size;
        uma_init uminit;
        uma_fini fini;
        int align;
        uint32_t flags;
};

struct uma_bucket_zone {
        uma_zone_t      ubz_zone;
        char            *ubz_name;
        int             ubz_entries;    /* Number of items it can hold. */
        int             ubz_maxsize;    /* Maximum allocation size per-item. */
};

/*
 * Compute the actual number of bucket entries to pack them in power
 * of two sizes for more efficient space utilization.
 */
#define BUCKET_SIZE(n)                                          \
    (((sizeof(void *) * (n)) - sizeof(struct uma_bucket)) / sizeof(void *))

#define BUCKET_MAX      BUCKET_SIZE(128)

struct uma_bucket_zone bucket_zones[] = {
        { NULL, "4 Bucket", BUCKET_SIZE(4), 4096 },
        { NULL, "8 Bucket", BUCKET_SIZE(8), 2048 },
        { NULL, "16 Bucket", BUCKET_SIZE(16), 1024 },
        { NULL, "32 Bucket", BUCKET_SIZE(32), 512 },
        { NULL, "64 Bucket", BUCKET_SIZE(64), 256 },
        { NULL, "128 Bucket", BUCKET_SIZE(128), 128 },
        { NULL, NULL, 0}
};

/*
 * Flags and enumerations to be passed to internal functions.
 */
enum zfreeskip { SKIP_NONE = 0, SKIP_DTOR, SKIP_FINI };

/* Prototypes.. */

static void *noobj_alloc(uma_zone_t, int, uint8_t *, int);
static void *page_alloc(uma_zone_t, int, uint8_t *, int);
static void *startup_alloc(uma_zone_t, int, uint8_t *, int);
static void page_free(void *, int, uint8_t);
static uma_slab_t keg_alloc_slab(uma_keg_t, uma_zone_t, int);
static void cache_drain(uma_zone_t);
static void bucket_drain(uma_zone_t, uma_bucket_t);
static void bucket_cache_drain(uma_zone_t zone);
static int keg_ctor(void *, int, void *, int);
static void keg_dtor(void *, int, void *);
static int zone_ctor(void *, int, void *, int);
static void zone_dtor(void *, int, void *);
static int zero_init(void *, int, int);
static void keg_small_init(uma_keg_t keg);
static void keg_large_init(uma_keg_t keg);
static void zone_foreach(void (*zfunc)(uma_zone_t));
static void zone_timeout(uma_zone_t zone);
static int hash_alloc(struct uma_hash *);
static int hash_expand(struct uma_hash *, struct uma_hash *);
static void hash_free(struct uma_hash *hash);
static void uma_timeout(void *);
static void uma_startup3(void);
static void *zone_alloc_item(uma_zone_t, void *, int);
static void zone_free_item(uma_zone_t, void *, void *, enum zfreeskip);
static void bucket_enable(void);
static void bucket_init(void);
static uma_bucket_t bucket_alloc(uma_zone_t zone, void *, int);
static void bucket_free(uma_zone_t zone, uma_bucket_t, void *);
static void bucket_zone_drain(void);
static uma_bucket_t zone_alloc_bucket(uma_zone_t zone, void *, int flags);
static uma_slab_t zone_fetch_slab(uma_zone_t zone, uma_keg_t last, int flags);
static uma_slab_t zone_fetch_slab_multi(uma_zone_t zone, uma_keg_t last, int flags);
static void *slab_alloc_item(uma_keg_t keg, uma_slab_t slab);
static void slab_free_item(uma_keg_t keg, uma_slab_t slab, void *item);
static uma_keg_t uma_kcreate(uma_zone_t zone, size_t size, uma_init uminit,
    uma_fini fini, int align, uint32_t flags);
static int zone_import(uma_zone_t zone, void **bucket, int max, int flags);
static void zone_release(uma_zone_t zone, void **bucket, int cnt);

void uma_print_zone(uma_zone_t);
void uma_print_stats(void);
static int sysctl_vm_zone_count(SYSCTL_HANDLER_ARGS);
static int sysctl_vm_zone_stats(SYSCTL_HANDLER_ARGS);

SYSINIT(uma_startup3, SI_SUB_VM_CONF, SI_ORDER_SECOND, uma_startup3, NULL);

SYSCTL_PROC(_vm, OID_AUTO, zone_count, CTLFLAG_RD|CTLTYPE_INT,
    0, 0, sysctl_vm_zone_count, "I", "Number of UMA zones");

SYSCTL_PROC(_vm, OID_AUTO, zone_stats, CTLFLAG_RD|CTLTYPE_STRUCT,
    0, 0, sysctl_vm_zone_stats, "s,struct uma_type_header", "Zone Stats");

static int zone_warnings = 1;
TUNABLE_INT("vm.zone_warnings", &zone_warnings);
SYSCTL_INT(_vm, OID_AUTO, zone_warnings, CTLFLAG_RW, &zone_warnings, 0,
    "Warn when UMA zones becomes full");

/*
 * This routine checks to see whether or not it's safe to enable buckets.
 */
static void
bucket_enable(void)
{
        bucketdisable = vm_page_count_min();
}

/*
 * Initialize bucket_zones, the array of zones of buckets of various sizes.
 *
 * For each zone, calculate the memory required for each bucket, consisting
 * of the header and an array of pointers.
 */
static void
bucket_init(void)
{
        struct uma_bucket_zone *ubz;
        int size;
        int i;

        for (i = 0, ubz = &bucket_zones[0]; ubz->ubz_entries != 0; ubz++) {
                size = roundup(sizeof(struct uma_bucket), sizeof(void *));
                size += sizeof(void *) * ubz->ubz_entries;
                ubz->ubz_zone = uma_zcreate(ubz->ubz_name, size,
                    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR,
                    UMA_ZONE_MTXCLASS | UMA_ZFLAG_BUCKET);
        }
}

/*
 * Given a desired number of entries for a bucket, return the zone from which
 * to allocate the bucket.
 */
static struct uma_bucket_zone *
bucket_zone_lookup(int entries)
{
        struct uma_bucket_zone *ubz;

        for (ubz = &bucket_zones[0]; ubz->ubz_entries != 0; ubz++)
                if (ubz->ubz_entries >= entries)
                        return (ubz);
        ubz--;
        return (ubz);
}

static int
bucket_select(int size)
{
        struct uma_bucket_zone *ubz;

        ubz = &bucket_zones[0];
        if (size > ubz->ubz_maxsize)
                return MAX((ubz->ubz_maxsize * ubz->ubz_entries) / size, 1);

        for (; ubz->ubz_entries != 0; ubz++)
                if (ubz->ubz_maxsize < size)
                        break;
        ubz--;
        return (ubz->ubz_entries);
}

static uma_bucket_t
bucket_alloc(uma_zone_t zone, void *udata, int flags)
{
        struct uma_bucket_zone *ubz;
        uma_bucket_t bucket;

        /*
         * This is to stop us from allocating per cpu buckets while we're
         * running out of vm.boot_pages.  Otherwise, we would exhaust the
         * boot pages.  This also prevents us from allocating buckets in
         * low memory situations.
         */
        if (bucketdisable)
                return (NULL);
        /*
         * To limit bucket recursion we store the original zone flags
         * in a cookie passed via zalloc_arg/zfree_arg.  This allows the
         * NOVM flag to persist even through deep recursions.  We also
         * store ZFLAG_BUCKET once we have recursed attempting to allocate
         * a bucket for a bucket zone so we do not allow infinite bucket
         * recursion.  This cookie will even persist to frees of unused
         * buckets via the allocation path or bucket allocations in the
         * free path.
         */
        if ((uintptr_t)udata & UMA_ZFLAG_BUCKET)
                return (NULL);
        if ((zone->uz_flags & UMA_ZFLAG_BUCKET) == 0)
                udata = (void *)(uintptr_t)zone->uz_flags;
        else
                udata = (void *)((uintptr_t)udata | UMA_ZFLAG_BUCKET);
        if ((uintptr_t)udata & UMA_ZFLAG_CACHEONLY)
                flags |= M_NOVM;
        ubz = bucket_zone_lookup(zone->uz_count);
        bucket = uma_zalloc_arg(ubz->ubz_zone, udata, flags);
        if (bucket) {
#ifdef INVARIANTS
                bzero(bucket->ub_bucket, sizeof(void *) * ubz->ubz_entries);
#endif
                bucket->ub_cnt = 0;
                bucket->ub_entries = ubz->ubz_entries;
        }

        return (bucket);
}

static void
bucket_free(uma_zone_t zone, uma_bucket_t bucket, void *udata)
{
        struct uma_bucket_zone *ubz;

        KASSERT(bucket->ub_cnt == 0,
            ("bucket_free: Freeing a non free bucket."));
        if ((zone->uz_flags & UMA_ZFLAG_BUCKET) == 0)
                udata = (void *)(uintptr_t)zone->uz_flags;
        ubz = bucket_zone_lookup(bucket->ub_entries);
        uma_zfree_arg(ubz->ubz_zone, bucket, udata);
}

static void
bucket_zone_drain(void)
{
        struct uma_bucket_zone *ubz;

        for (ubz = &bucket_zones[0]; ubz->ubz_entries != 0; ubz++)
                zone_drain(ubz->ubz_zone);
}

static void
zone_log_warning(uma_zone_t zone)
{
        static const struct timeval warninterval = { 300, 0 };

        if (!zone_warnings || zone->uz_warning == NULL)
                return;

        if (ratecheck(&zone->uz_ratecheck, &warninterval))
                printf("[zone: %s] %s\n", zone->uz_name, zone->uz_warning);
}

static void
zone_foreach_keg(uma_zone_t zone, void (*kegfn)(uma_keg_t))
{
        uma_klink_t klink;

        LIST_FOREACH(klink, &zone->uz_kegs, kl_link)
                kegfn(klink->kl_keg);
}

/*
 * Routine called by timeout which is used to fire off some time interval
 * based calculations.  (stats, hash size, etc.)
 *
 * Arguments:
 *      arg   Unused
 *
 * Returns:
 *      Nothing
 */
static void
uma_timeout(void *unused)
{
        bucket_enable();
        zone_foreach(zone_timeout);

        /* Reschedule this event */
        callout_reset(&uma_callout, UMA_TIMEOUT * hz, uma_timeout, NULL);
}

/*
 * Routine to perform timeout driven calculations.  This expands the
 * hashes and does per cpu statistics aggregation.
 *
 *  Returns nothing.
 */
static void
keg_timeout(uma_keg_t keg)
{

        KEG_LOCK(keg);
        /*
         * Expand the keg hash table.
         *
         * This is done if the number of slabs is larger than the hash size.
         * What I'm trying to do here is completely reduce collisions.  This
         * may be a little aggressive.  Should I allow for two collisions max?
         */
        if (keg->uk_flags & UMA_ZONE_HASH &&
            keg->uk_pages / keg->uk_ppera >= keg->uk_hash.uh_hashsize) {
                struct uma_hash newhash;
                struct uma_hash oldhash;
                int ret;

                /*
                 * This is so involved because allocating and freeing
                 * while the keg lock is held will lead to deadlock.
                 * I have to do everything in stages and check for
                 * races.
                 */
                newhash = keg->uk_hash;
                KEG_UNLOCK(keg);
                ret = hash_alloc(&newhash);
                KEG_LOCK(keg);
                if (ret) {
                        if (hash_expand(&keg->uk_hash, &newhash)) {
                                oldhash = keg->uk_hash;
                                keg->uk_hash = newhash;
                        } else
                                oldhash = newhash;

                        KEG_UNLOCK(keg);
                        hash_free(&oldhash);
                        return;
                }
        }
        KEG_UNLOCK(keg);
}

static void
zone_timeout(uma_zone_t zone)
{

        zone_foreach_keg(zone, &keg_timeout);
}

/*
 * Allocate and zero fill the next sized hash table from the appropriate
 * backing store.
 *
 * Arguments:
 *      hash  A new hash structure with the old hash size in uh_hashsize
 *
 * Returns:
 *      1 on sucess and 0 on failure.
 */
static int
hash_alloc(struct uma_hash *hash)
{
        int oldsize;
        int alloc;

        oldsize = hash->uh_hashsize;

        /* We're just going to go to a power of two greater */
        if (oldsize)  {
                hash->uh_hashsize = oldsize * 2;
                alloc = sizeof(hash->uh_slab_hash[0]) * hash->uh_hashsize;
                hash->uh_slab_hash = (struct slabhead *)malloc(alloc,
                    M_UMAHASH, M_NOWAIT);
        } else {
                alloc = sizeof(hash->uh_slab_hash[0]) * UMA_HASH_SIZE_INIT;
                hash->uh_slab_hash = zone_alloc_item(hashzone, NULL,
                    M_WAITOK);
                hash->uh_hashsize = UMA_HASH_SIZE_INIT;
        }
        if (hash->uh_slab_hash) {
                bzero(hash->uh_slab_hash, alloc);
                hash->uh_hashmask = hash->uh_hashsize - 1;
                return (1);
        }

        return (0);
}

/*
 * Expands the hash table for HASH zones.  This is done from zone_timeout
 * to reduce collisions.  This must not be done in the regular allocation
 * path, otherwise, we can recurse on the vm while allocating pages.
 *
 * Arguments:
 *      oldhash  The hash you want to expand
 *      newhash  The hash structure for the new table
 *
 * Returns:
 *      Nothing
 *
 * Discussion:
 */
static int
hash_expand(struct uma_hash *oldhash, struct uma_hash *newhash)
{
        uma_slab_t slab;
        int hval;
        int i;

        if (!newhash->uh_slab_hash)
                return (0);

        if (oldhash->uh_hashsize >= newhash->uh_hashsize)
                return (0);

        /*
         * I need to investigate hash algorithms for resizing without a
         * full rehash.
         */

        for (i = 0; i < oldhash->uh_hashsize; i++)
                while (!SLIST_EMPTY(&oldhash->uh_slab_hash[i])) {
                        slab = SLIST_FIRST(&oldhash->uh_slab_hash[i]);
                        SLIST_REMOVE_HEAD(&oldhash->uh_slab_hash[i], us_hlink);
                        hval = UMA_HASH(newhash, slab->us_data);
                        SLIST_INSERT_HEAD(&newhash->uh_slab_hash[hval],
                            slab, us_hlink);
                }

        return (1);
}

/*
 * Free the hash bucket to the appropriate backing store.
 *
 * Arguments:
 *      slab_hash  The hash bucket we're freeing
 *      hashsize   The number of entries in that hash bucket
 *
 * Returns:
 *      Nothing
 */
static void
hash_free(struct uma_hash *hash)
{
        if (hash->uh_slab_hash == NULL)
                return;
        if (hash->uh_hashsize == UMA_HASH_SIZE_INIT)
                zone_free_item(hashzone, hash->uh_slab_hash, NULL, SKIP_NONE);
        else
                free(hash->uh_slab_hash, M_UMAHASH);
}

/*
 * Frees all outstanding items in a bucket
 *
 * Arguments:
 *      zone   The zone to free to, must be unlocked.
 *      bucket The free/alloc bucket with items, cpu queue must be locked.
 *
 * Returns:
 *      Nothing
 */

static void
bucket_drain(uma_zone_t zone, uma_bucket_t bucket)
{
        int i;

        if (bucket == NULL)
                return;

        if (zone->uz_fini)
                for (i = 0; i < bucket->ub_cnt; i++) 
                        zone->uz_fini(bucket->ub_bucket[i], zone->uz_size);
        zone->uz_release(zone->uz_arg, bucket->ub_bucket, bucket->ub_cnt);
        bucket->ub_cnt = 0;
}

/*
 * Drains the per cpu caches for a zone.
 *
 * NOTE: This may only be called while the zone is being turn down, and not
 * during normal operation.  This is necessary in order that we do not have
 * to migrate CPUs to drain the per-CPU caches.
 *
 * Arguments:
 *      zone     The zone to drain, must be unlocked.
 *
 * Returns:
 *      Nothing
 */
static void
cache_drain(uma_zone_t zone)
{
        uma_cache_t cache;
        int cpu;

        /*
         * XXX: It is safe to not lock the per-CPU caches, because we're
         * tearing down the zone anyway.  I.e., there will be no further use
         * of the caches at this point.
         *
         * XXX: It would good to be able to assert that the zone is being
         * torn down to prevent improper use of cache_drain().
         *
         * XXX: We lock the zone before passing into bucket_cache_drain() as
         * it is used elsewhere.  Should the tear-down path be made special
         * there in some form?
         */
        CPU_FOREACH(cpu) {
                cache = &zone->uz_cpu[cpu];
                bucket_drain(zone, cache->uc_allocbucket);
                bucket_drain(zone, cache->uc_freebucket);
                if (cache->uc_allocbucket != NULL)
                        bucket_free(zone, cache->uc_allocbucket, NULL);
                if (cache->uc_freebucket != NULL)
                        bucket_free(zone, cache->uc_freebucket, NULL);
                cache->uc_allocbucket = cache->uc_freebucket = NULL;
        }
        ZONE_LOCK(zone);
        bucket_cache_drain(zone);
        ZONE_UNLOCK(zone);
}

/*
 * Drain the cached buckets from a zone.  Expects a locked zone on entry.
 */
static void
bucket_cache_drain(uma_zone_t zone)
{
        uma_bucket_t bucket;

        /*
         * Drain the bucket queues and free the buckets, we just keep two per
         * cpu (alloc/free).
         */
        while ((bucket = LIST_FIRST(&zone->uz_buckets)) != NULL) {
                LIST_REMOVE(bucket, ub_link);
                ZONE_UNLOCK(zone);
                bucket_drain(zone, bucket);
                bucket_free(zone, bucket, NULL);
                ZONE_LOCK(zone);
        }
}

static void
keg_free_slab(uma_keg_t keg, uma_slab_t slab, int start)
{
        uint8_t *mem;
        int i;
        uint8_t flags;

        mem = slab->us_data;
        flags = slab->us_flags;
        i = start;
        if (keg->uk_fini != NULL) {
                for (i--; i > -1; i--)
                        keg->uk_fini(slab->us_data + (keg->uk_rsize * i),
                            keg->uk_size);
        }
        if (keg->uk_flags & UMA_ZONE_OFFPAGE)
                zone_free_item(keg->uk_slabzone, slab, NULL, SKIP_NONE);
#ifdef UMA_DEBUG
        printf("%s: Returning %d bytes.\n", keg->uk_name,
            PAGE_SIZE * keg->uk_ppera);
#endif
        keg->uk_freef(mem, PAGE_SIZE * keg->uk_ppera, flags);
}

/*
 * Frees pages from a keg back to the system.  This is done on demand from
 * the pageout daemon.
 *
 * Returns nothing.
 */
static void
keg_drain(uma_keg_t keg)
{
        struct slabhead freeslabs = { 0 };
        uma_slab_t slab;
        uma_slab_t n;

        /*
         * We don't want to take pages from statically allocated kegs at this
         * time
         */
        if (keg->uk_flags & UMA_ZONE_NOFREE || keg->uk_freef == NULL)
                return;

#ifdef UMA_DEBUG
        printf("%s free items: %u\n", keg->uk_name, keg->uk_free);
#endif
        KEG_LOCK(keg);
        if (keg->uk_free == 0)
                goto finished;

        slab = LIST_FIRST(&keg->uk_free_slab);
        while (slab) {
                n = LIST_NEXT(slab, us_link);

                /* We have no where to free these to */
                if (slab->us_flags & UMA_SLAB_BOOT) {
                        slab = n;
                        continue;
                }

                LIST_REMOVE(slab, us_link);
                keg->uk_pages -= keg->uk_ppera;
                keg->uk_free -= keg->uk_ipers;

                if (keg->uk_flags & UMA_ZONE_HASH)
                        UMA_HASH_REMOVE(&keg->uk_hash, slab, slab->us_data);

                SLIST_INSERT_HEAD(&freeslabs, slab, us_hlink);

                slab = n;
        }
finished:
        KEG_UNLOCK(keg);

        while ((slab = SLIST_FIRST(&freeslabs)) != NULL) {
                SLIST_REMOVE(&freeslabs, slab, uma_slab, us_hlink);
                keg_free_slab(keg, slab, keg->uk_ipers);
        }
}

static void
zone_drain_wait(uma_zone_t zone, int waitok)
{

        /*
         * Set draining to interlock with zone_dtor() so we can release our
         * locks as we go.  Only dtor() should do a WAITOK call since it
         * is the only call that knows the structure will still be available
         * when it wakes up.
         */
        ZONE_LOCK(zone);
        while (zone->uz_flags & UMA_ZFLAG_DRAINING) {
                if (waitok == M_NOWAIT)
                        goto out;
                mtx_unlock(&uma_mtx);
                msleep(zone, zone->uz_lockptr, PVM, "zonedrain", 1);
                mtx_lock(&uma_mtx);
        }
        zone->uz_flags |= UMA_ZFLAG_DRAINING;
        bucket_cache_drain(zone);
        ZONE_UNLOCK(zone);
        /*
         * The DRAINING flag protects us from being freed while
         * we're running.  Normally the uma_mtx would protect us but we
         * must be able to release and acquire the right lock for each keg.
         */
        zone_foreach_keg(zone, &keg_drain);
        ZONE_LOCK(zone);
        zone->uz_flags &= ~UMA_ZFLAG_DRAINING;
        wakeup(zone);
out:
        ZONE_UNLOCK(zone);
}

void
zone_drain(uma_zone_t zone)
{

        zone_drain_wait(zone, M_NOWAIT);
}

/*
 * Allocate a new slab for a keg.  This does not insert the slab onto a list.
 *
 * Arguments:
 *      wait  Shall we wait?
 *
 * Returns:
 *      The slab that was allocated or NULL if there is no memory and the
 *      caller specified M_NOWAIT.
 */
static uma_slab_t
keg_alloc_slab(uma_keg_t keg, uma_zone_t zone, int wait)
{
        uma_slabrefcnt_t slabref;
        uma_alloc allocf;
        uma_slab_t slab;
        uint8_t *mem;
        uint8_t flags;
        int i;

        mtx_assert(&keg->uk_lock, MA_OWNED);
        slab = NULL;
        mem = NULL;

#ifdef UMA_DEBUG
        printf("alloc_slab:  Allocating a new slab for %s\n", keg->uk_name);
#endif
        allocf = keg->uk_allocf;
        KEG_UNLOCK(keg);

        if (keg->uk_flags & UMA_ZONE_OFFPAGE) {
                slab = zone_alloc_item(keg->uk_slabzone, NULL, wait);
                if (slab == NULL)
                        goto out;
        }

        /*
         * This reproduces the old vm_zone behavior of zero filling pages the
         * first time they are added to a zone.
         *
         * Malloced items are zeroed in uma_zalloc.
         */

        if ((keg->uk_flags & UMA_ZONE_MALLOC) == 0)
                wait |= M_ZERO;
        else
                wait &= ~M_ZERO;

        if (keg->uk_flags & UMA_ZONE_NODUMP)
                wait |= M_NODUMP;

        /* zone is passed for legacy reasons. */
        mem = allocf(zone, keg->uk_ppera * PAGE_SIZE, &flags, wait);
        if (mem == NULL) {
                if (keg->uk_flags & UMA_ZONE_OFFPAGE)
                        zone_free_item(keg->uk_slabzone, slab, NULL, SKIP_NONE);
                slab = NULL;
                goto out;
        }

        /* Point the slab into the allocated memory */
        if (!(keg->uk_flags & UMA_ZONE_OFFPAGE))
                slab = (uma_slab_t )(mem + keg->uk_pgoff);

        if (keg->uk_flags & UMA_ZONE_VTOSLAB)
                for (i = 0; i < keg->uk_ppera; i++)
                        vsetslab((vm_offset_t)mem + (i * PAGE_SIZE), slab);

        slab->us_keg = keg;
        slab->us_data = mem;
        slab->us_freecount = keg->uk_ipers;
        slab->us_flags = flags;
        BIT_FILL(SLAB_SETSIZE, &slab->us_free);
#ifdef INVARIANTS
        BIT_ZERO(SLAB_SETSIZE, &slab->us_debugfree);
#endif
        if (keg->uk_flags & UMA_ZONE_REFCNT) {
                slabref = (uma_slabrefcnt_t)slab;
                for (i = 0; i < keg->uk_ipers; i++)
                        slabref->us_refcnt[i] = 0;
        }

        if (keg->uk_init != NULL) {
                for (i = 0; i < keg->uk_ipers; i++)
                        if (keg->uk_init(slab->us_data + (keg->uk_rsize * i),
                            keg->uk_size, wait) != 0)
                                break;
                if (i != keg->uk_ipers) {
                        keg_free_slab(keg, slab, i);
                        slab = NULL;
                        goto out;
                }
        }
out:
        KEG_LOCK(keg);

        if (slab != NULL) {
                if (keg->uk_flags & UMA_ZONE_HASH)
                        UMA_HASH_INSERT(&keg->uk_hash, slab, mem);

                keg->uk_pages += keg->uk_ppera;
                keg->uk_free += keg->uk_ipers;
        }

        return (slab);
}

/*
 * This function is intended to be used early on in place of page_alloc() so
 * that we may use the boot time page cache to satisfy allocations before
 * the VM is ready.
 */
static void *
startup_alloc(uma_zone_t zone, int bytes, uint8_t *pflag, int wait)
{
        uma_keg_t keg;
        uma_slab_t tmps;
        int pages, check_pages;

        keg = zone_first_keg(zone);
        pages = howmany(bytes, PAGE_SIZE);
        check_pages = pages - 1;
        KASSERT(pages > 0, ("startup_alloc can't reserve 0 pages\n"));

        /*
         * Check our small startup cache to see if it has pages remaining.
         */
        mtx_lock(&uma_boot_pages_mtx);

        /* First check if we have enough room. */
        tmps = LIST_FIRST(&uma_boot_pages);
        while (tmps != NULL && check_pages-- > 0)
                tmps = LIST_NEXT(tmps, us_link);
        if (tmps != NULL) {
                /*
                 * It's ok to lose tmps references.  The last one will
                 * have tmps->us_data pointing to the start address of
                 * "pages" contiguous pages of memory.
                 */
                while (pages-- > 0) {
                        tmps = LIST_FIRST(&uma_boot_pages);
                        LIST_REMOVE(tmps, us_link);
                }
                mtx_unlock(&uma_boot_pages_mtx);
                *pflag = tmps->us_flags;
                return (tmps->us_data);
        }
        mtx_unlock(&uma_boot_pages_mtx);
        if (booted < UMA_STARTUP2)
                panic("UMA: Increase vm.boot_pages");
        /*
         * Now that we've booted reset these users to their real allocator.
         */
#ifdef UMA_MD_SMALL_ALLOC
        keg->uk_allocf = (keg->uk_ppera > 1) ? page_alloc : uma_small_alloc;
#else
        keg->uk_allocf = page_alloc;
#endif
        return keg->uk_allocf(zone, bytes, pflag, wait);
}

/*
 * Allocates a number of pages from the system
 *
 * Arguments:
 *      bytes  The number of bytes requested
 *      wait  Shall we wait?
 *
 * Returns:
 *      A pointer to the alloced memory or possibly
 *      NULL if M_NOWAIT is set.
 */
static void *
page_alloc(uma_zone_t zone, int bytes, uint8_t *pflag, int wait)
{
        void *p;        /* Returned page */

        *pflag = UMA_SLAB_KMEM;
        p = (void *) kmem_malloc(kmem_arena, bytes, wait);

        return (p);
}

/*
 * Allocates a number of pages from within an object
 *
 * Arguments:
 *      bytes  The number of bytes requested
 *      wait   Shall we wait?
 *
 * Returns:
 *      A pointer to the alloced memory or possibly
 *      NULL if M_NOWAIT is set.
 */
static void *
noobj_alloc(uma_zone_t zone, int bytes, uint8_t *flags, int wait)
{
        TAILQ_HEAD(, vm_page) alloctail;
        u_long npages;
        vm_offset_t retkva, zkva;
        vm_page_t p, p_next;
        uma_keg_t keg;

        TAILQ_INIT(&alloctail);
        keg = zone_first_keg(zone);

        npages = howmany(bytes, PAGE_SIZE);
        while (npages > 0) {
                p = vm_page_alloc(NULL, 0, VM_ALLOC_INTERRUPT |
                    VM_ALLOC_WIRED | VM_ALLOC_NOOBJ);
                if (p != NULL) {
                        /*
                         * Since the page does not belong to an object, its
                         * listq is unused.
                         */
                        TAILQ_INSERT_TAIL(&alloctail, p, listq);
                        npages--;
                        continue;
                }
                if (wait & M_WAITOK) {
                        VM_WAIT;
                        continue;
                }

                /*
                 * Page allocation failed, free intermediate pages and
                 * exit.
                 */
                TAILQ_FOREACH_SAFE(p, &alloctail, listq, p_next) {
                        vm_page_unwire(p, 0);
                        vm_page_free(p); 
                }
                return (NULL);
        }
        *flags = UMA_SLAB_PRIV;
        zkva = keg->uk_kva +
            atomic_fetchadd_long(&keg->uk_offset, round_page(bytes));
        retkva = zkva;
        TAILQ_FOREACH(p, &alloctail, listq) {
                pmap_qenter(zkva, &p, 1);
                zkva += PAGE_SIZE;
        }

        return ((void *)retkva);
}

/*
 * Frees a number of pages to the system
 *
 * Arguments:
 *      mem   A pointer to the memory to be freed
 *      size  The size of the memory being freed
 *      flags The original p->us_flags field
 *
 * Returns:
 *      Nothing
 */
static void
page_free(void *mem, int size, uint8_t flags)
{
        struct vmem *vmem;

        if (flags & UMA_SLAB_KMEM)
                vmem = kmem_arena;
        else if (flags & UMA_SLAB_KERNEL)
                vmem = kernel_arena;
        else
                panic("UMA: page_free used with invalid flags %d", flags);

        kmem_free(vmem, (vm_offset_t)mem, size);
}

/*
 * Zero fill initializer
 *
 * Arguments/Returns follow uma_init specifications
 */
static int
zero_init(void *mem, int size, int flags)
{
        bzero(mem, size);
        return (0);
}

/*
 * Finish creating a small uma keg.  This calculates ipers, and the keg size.
 *
 * Arguments
 *      keg  The zone we should initialize
 *
 * Returns
 *      Nothing
 */
static void
keg_small_init(uma_keg_t keg)
{
        u_int rsize;
        u_int memused;
        u_int wastedspace;
        u_int shsize;

        if (keg->uk_flags & UMA_ZONE_PCPU) {
                u_int ncpus = mp_ncpus ? mp_ncpus : MAXCPU;

                keg->uk_slabsize = sizeof(struct pcpu);
                keg->uk_ppera = howmany(ncpus * sizeof(struct pcpu),
                    PAGE_SIZE);
        } else {
                keg->uk_slabsize = UMA_SLAB_SIZE;
                keg->uk_ppera = 1;
        }

        /*
         * Calculate the size of each allocation (rsize) according to
         * alignment.  If the requested size is smaller than we have
         * allocation bits for we round it up.
         */
        rsize = keg->uk_size;
        if (rsize < keg->uk_slabsize / SLAB_SETSIZE)
                rsize = keg->uk_slabsize / SLAB_SETSIZE;
        if (rsize & keg->uk_align)
                rsize = (rsize & ~keg->uk_align) + (keg->uk_align + 1);
        keg->uk_rsize = rsize;

        KASSERT((keg->uk_flags & UMA_ZONE_PCPU) == 0 ||
            keg->uk_rsize < sizeof(struct pcpu),
            ("%s: size %u too large", __func__, keg->uk_rsize));

        if (keg->uk_flags & UMA_ZONE_REFCNT)
                rsize += sizeof(uint32_t);

        if (keg->uk_flags & UMA_ZONE_OFFPAGE)
                shsize = 0;
        else 
                shsize = sizeof(struct uma_slab);

        keg->uk_ipers = (keg->uk_slabsize - shsize) / rsize;
        KASSERT(keg->uk_ipers > 0 && keg->uk_ipers <= SLAB_SETSIZE,
            ("%s: keg->uk_ipers %u", __func__, keg->uk_ipers));

        memused = keg->uk_ipers * rsize + shsize;
        wastedspace = keg->uk_slabsize - memused;

        /*
         * We can't do OFFPAGE if we're internal or if we've been
         * asked to not go to the VM for buckets.  If we do this we
         * may end up going to the VM  for slabs which we do not
         * want to do if we're UMA_ZFLAG_CACHEONLY as a result
         * of UMA_ZONE_VM, which clearly forbids it.
         */
        if ((keg->uk_flags & UMA_ZFLAG_INTERNAL) ||
            (keg->uk_flags & UMA_ZFLAG_CACHEONLY))
                return;

        /*
         * See if using an OFFPAGE slab will limit our waste.  Only do
         * this if it permits more items per-slab.
         *
         * XXX We could try growing slabsize to limit max waste as well.
         * Historically this was not done because the VM could not
         * efficiently handle contiguous allocations.
         */
        if ((wastedspace >= keg->uk_slabsize / UMA_MAX_WASTE) &&
            (keg->uk_ipers < (keg->uk_slabsize / keg->uk_rsize))) {
                keg->uk_ipers = keg->uk_slabsize / keg->uk_rsize;
                KASSERT(keg->uk_ipers > 0 && keg->uk_ipers <= SLAB_SETSIZE,
                    ("%s: keg->uk_ipers %u", __func__, keg->uk_ipers));
#ifdef UMA_DEBUG
                printf("UMA decided we need offpage slab headers for "
                    "keg: %s, calculated wastedspace = %d, "
                    "maximum wasted space allowed = %d, "
                    "calculated ipers = %d, "
                    "new wasted space = %d\n", keg->uk_name, wastedspace,
                    keg->uk_slabsize / UMA_MAX_WASTE, keg->uk_ipers,
                    keg->uk_slabsize - keg->uk_ipers * keg->uk_rsize);
#endif
                keg->uk_flags |= UMA_ZONE_OFFPAGE;
        }

        if ((keg->uk_flags & UMA_ZONE_OFFPAGE) &&
            (keg->uk_flags & UMA_ZONE_VTOSLAB) == 0)
                keg->uk_flags |= UMA_ZONE_HASH;
}

/*
 * Finish creating a large (> UMA_SLAB_SIZE) uma kegs.  Just give in and do
 * OFFPAGE for now.  When I can allow for more dynamic slab sizes this will be
 * more complicated.
 *
 * Arguments
 *      keg  The keg we should initialize
 *
 * Returns
 *      Nothing
 */
static void
keg_large_init(uma_keg_t keg)
{

        KASSERT(keg != NULL, ("Keg is null in keg_large_init"));
        KASSERT((keg->uk_flags & UMA_ZFLAG_CACHEONLY) == 0,
            ("keg_large_init: Cannot large-init a UMA_ZFLAG_CACHEONLY keg"));
        KASSERT((keg->uk_flags & UMA_ZONE_PCPU) == 0,
            ("%s: Cannot large-init a UMA_ZONE_PCPU keg", __func__));

        keg->uk_ppera = howmany(keg->uk_size, PAGE_SIZE);
        keg->uk_slabsize = keg->uk_ppera * PAGE_SIZE;
        keg->uk_ipers = 1;
        keg->uk_rsize = keg->uk_size;

        /* We can't do OFFPAGE if we're internal, bail out here. */
        if (keg->uk_flags & UMA_ZFLAG_INTERNAL)
                return;

        keg->uk_flags |= UMA_ZONE_OFFPAGE;
        if ((keg->uk_flags & UMA_ZONE_VTOSLAB) == 0)
                keg->uk_flags |= UMA_ZONE_HASH;
}

static void
keg_cachespread_init(uma_keg_t keg)
{
        int alignsize;
        int trailer;
        int pages;
        int rsize;

        KASSERT((keg->uk_flags & UMA_ZONE_PCPU) == 0,
            ("%s: Cannot cachespread-init a UMA_ZONE_PCPU keg", __func__));

        alignsize = keg->uk_align + 1;
        rsize = keg->uk_size;
        /*
         * We want one item to start on every align boundary in a page.  To
         * do this we will span pages.  We will also extend the item by the
         * size of align if it is an even multiple of align.  Otherwise, it
         * would fall on the same boundary every time.
         */
        if (rsize & keg->uk_align)
                rsize = (rsize & ~keg->uk_align) + alignsize;
        if ((rsize & alignsize) == 0)
                rsize += alignsize;
        trailer = rsize - keg->uk_size;
        pages = (rsize * (PAGE_SIZE / alignsize)) / PAGE_SIZE;
        pages = MIN(pages, (128 * 1024) / PAGE_SIZE);
        keg->uk_rsize = rsize;
        keg->uk_ppera = pages;
        keg->uk_slabsize = UMA_SLAB_SIZE;
        keg->uk_ipers = ((pages * PAGE_SIZE) + trailer) / rsize;
        keg->uk_flags |= UMA_ZONE_OFFPAGE | UMA_ZONE_VTOSLAB;
        KASSERT(keg->uk_ipers <= uma_max_ipers,
            ("%s: keg->uk_ipers too high(%d) increase max_ipers", __func__,
            keg->uk_ipers));
}

/*
 * Keg header ctor.  This initializes all fields, locks, etc.  And inserts
 * the keg onto the global keg list.
 *
 * Arguments/Returns follow uma_ctor specifications
 *      udata  Actually uma_kctor_args
 */
static int
keg_ctor(void *mem, int size, void *udata, int flags)
{
        struct uma_kctor_args *arg = udata;
        uma_keg_t keg = mem;
        uma_zone_t zone;

        bzero(keg, size);
        keg->uk_size = arg->size;
        keg->uk_init = arg->uminit;
        keg->uk_fini = arg->fini;
        keg->uk_align = arg->align;
        keg->uk_free = 0;
        keg->uk_reserve = 0;
        keg->uk_pages = 0;
        keg->uk_flags = arg->flags;
        keg->uk_allocf = page_alloc;
        keg->uk_freef = page_free;
        keg->uk_slabzone = NULL;

        /*
         * The master zone is passed to us at keg-creation time.
         */
        zone = arg->zone;
        keg->uk_name = zone->uz_name;

        if (arg->flags & UMA_ZONE_VM)
                keg->uk_flags |= UMA_ZFLAG_CACHEONLY;

        if (arg->flags & UMA_ZONE_ZINIT)
                keg->uk_init = zero_init;

        if (arg->flags & UMA_ZONE_REFCNT || arg->flags & UMA_ZONE_MALLOC)
                keg->uk_flags |= UMA_ZONE_VTOSLAB;

        if (arg->flags & UMA_ZONE_PCPU)
#ifdef SMP
                keg->uk_flags |= UMA_ZONE_OFFPAGE;
#else
                keg->uk_flags &= ~UMA_ZONE_PCPU;
#endif

        if (keg->uk_flags & UMA_ZONE_CACHESPREAD) {
                keg_cachespread_init(keg);
        } else if (keg->uk_flags & UMA_ZONE_REFCNT) {
                if (keg->uk_size >
                    (UMA_SLAB_SIZE - sizeof(struct uma_slab_refcnt) -
                    sizeof(uint32_t)))
                        keg_large_init(keg);
                else
                        keg_small_init(keg);
        } else {
                if (keg->uk_size > (UMA_SLAB_SIZE - sizeof(struct uma_slab)))
                        keg_large_init(keg);
                else
                        keg_small_init(keg);
        }

        if (keg->uk_flags & UMA_ZONE_OFFPAGE) {
                if (keg->uk_flags & UMA_ZONE_REFCNT) {
                        if (keg->uk_ipers > uma_max_ipers_ref)
                                panic("Too many ref items per zone: %d > %d\n",
                                    keg->uk_ipers, uma_max_ipers_ref);
                        keg->uk_slabzone = slabrefzone;
                } else
                        keg->uk_slabzone = slabzone;
        }

        /*
         * If we haven't booted yet we need allocations to go through the
         * startup cache until the vm is ready.
         */
        if (keg->uk_ppera == 1) {
#ifdef UMA_MD_SMALL_ALLOC
                keg->uk_allocf = uma_small_alloc;
                keg->uk_freef = uma_small_free;

                if (booted < UMA_STARTUP)
                        keg->uk_allocf = startup_alloc;
#else
                if (booted < UMA_STARTUP2)
                        keg->uk_allocf = startup_alloc;
#endif
        } else if (booted < UMA_STARTUP2 &&
            (keg->uk_flags & UMA_ZFLAG_INTERNAL))
                keg->uk_allocf = startup_alloc;

        /*
         * Initialize keg's lock
         */
        KEG_LOCK_INIT(keg, (arg->flags & UMA_ZONE_MTXCLASS));

        /*
         * If we're putting the slab header in the actual page we need to
         * figure out where in each page it goes.  This calculates a right
         * justified offset into the memory on an ALIGN_PTR boundary.
         */
        if (!(keg->uk_flags & UMA_ZONE_OFFPAGE)) {
                u_int totsize;

                /* Size of the slab struct and free list */
                totsize = sizeof(struct uma_slab);

                /* Size of the reference counts. */
                if (keg->uk_flags & UMA_ZONE_REFCNT)
                        totsize += keg->uk_ipers * sizeof(uint32_t);

                if (totsize & UMA_ALIGN_PTR)
                        totsize = (totsize & ~UMA_ALIGN_PTR) +
                            (UMA_ALIGN_PTR + 1);
                keg->uk_pgoff = (PAGE_SIZE * keg->uk_ppera) - totsize;

                /*
                 * The only way the following is possible is if with our
                 * UMA_ALIGN_PTR adjustments we are now bigger than
                 * UMA_SLAB_SIZE.  I haven't checked whether this is
                 * mathematically possible for all cases, so we make
                 * sure here anyway.
                 */
                totsize = keg->uk_pgoff + sizeof(struct uma_slab);
                if (keg->uk_flags & UMA_ZONE_REFCNT)
                        totsize += keg->uk_ipers * sizeof(uint32_t);
                if (totsize > PAGE_SIZE * keg->uk_ppera) {
                        printf("zone %s ipers %d rsize %d size %d\n",
                            zone->uz_name, keg->uk_ipers, keg->uk_rsize,
                            keg->uk_size);
                        panic("UMA slab won't fit.");
                }
        }

        if (keg->uk_flags & UMA_ZONE_HASH)
                hash_alloc(&keg->uk_hash);

#ifdef UMA_DEBUG
        printf("UMA: %s(%p) size %d(%d) flags %#x ipers %d ppera %d out %d free %d\n",
            zone->uz_name, zone, keg->uk_size, keg->uk_rsize, keg->uk_flags,
            keg->uk_ipers, keg->uk_ppera,
            (keg->uk_ipers * keg->uk_pages) - keg->uk_free, keg->uk_free);
#endif

        LIST_INSERT_HEAD(&keg->uk_zones, zone, uz_link);

        mtx_lock(&uma_mtx);
        LIST_INSERT_HEAD(&uma_kegs, keg, uk_link);
        mtx_unlock(&uma_mtx);
        return (0);
}

/*
 * Zone header ctor.  This initializes all fields, locks, etc.
 *
 * Arguments/Returns follow uma_ctor specifications
 *      udata  Actually uma_zctor_args
 */
static int
zone_ctor(void *mem, int size, void *udata, int flags)
{
        struct uma_zctor_args *arg = udata;
        uma_zone_t zone = mem;
        uma_zone_t z;
        uma_keg_t keg;

        bzero(zone, size);
        zone->uz_name = arg->name;
        zone->uz_ctor = arg->ctor;
        zone->uz_dtor = arg->dtor;
        zone->uz_slab = zone_fetch_slab;
        zone->uz_init = NULL;
        zone->uz_fini = NULL;
        zone->uz_allocs = 0;
        zone->uz_frees = 0;
        zone->uz_fails = 0;
        zone->uz_sleeps = 0;
        zone->uz_count = 0;
        zone->uz_flags = 0;
        zone->uz_warning = NULL;
        timevalclear(&zone->uz_ratecheck);
        keg = arg->keg;

        ZONE_LOCK_INIT(zone, (arg->flags & UMA_ZONE_MTXCLASS));

        /*
         * This is a pure cache zone, no kegs.
         */
        if (arg->import) {
                if (arg->flags & UMA_ZONE_VM)
                        arg->flags |= UMA_ZFLAG_CACHEONLY;
                zone->uz_flags = arg->flags;
                zone->uz_size = arg->size;
                zone->uz_import = arg->import;
                zone->uz_release = arg->release;
                zone->uz_arg = arg->arg;
                zone->uz_lockptr = &zone->uz_lock;
                goto out;
        }

        /*
         * Use the regular zone/keg/slab allocator.
         */
        zone->uz_import = (uma_import)zone_import;
        zone->uz_release = (uma_release)zone_release;
        zone->uz_arg = zone; 

        if (arg->flags & UMA_ZONE_SECONDARY) {
                KASSERT(arg->keg != NULL, ("Secondary zone on zero'd keg"));
                zone->uz_init = arg->uminit;
                zone->uz_fini = arg->fini;
                zone->uz_lockptr = &keg->uk_lock;
                zone->uz_flags |= UMA_ZONE_SECONDARY;
                mtx_lock(&uma_mtx);
                ZONE_LOCK(zone);
                LIST_FOREACH(z, &keg->uk_zones, uz_link) {
                        if (LIST_NEXT(z, uz_link) == NULL) {
                                LIST_INSERT_AFTER(z, zone, uz_link);
                                break;
                        }
                }
                ZONE_UNLOCK(zone);
                mtx_unlock(&uma_mtx);
        } else if (keg == NULL) {
                if ((keg = uma_kcreate(zone, arg->size, arg->uminit, arg->fini,
                    arg->align, arg->flags)) == NULL)
                        return (ENOMEM);
        } else {
                struct uma_kctor_args karg;
                int error;

                /* We should only be here from uma_startup() */
                karg.size = arg->size;
                karg.uminit = arg->uminit;
                karg.fini = arg->fini;
                karg.align = arg->align;
                karg.flags = arg->flags;
                karg.zone = zone;
                error = keg_ctor(arg->keg, sizeof(struct uma_keg), &karg,
                    flags);
                if (error)
                        return (error);
        }

        /*
         * Link in the first keg.
         */
        zone->uz_klink.kl_keg = keg;
        LIST_INSERT_HEAD(&zone->uz_kegs, &zone->uz_klink, kl_link);
        zone->uz_lockptr = &keg->uk_lock;
        zone->uz_size = keg->uk_size;
        zone->uz_flags |= (keg->uk_flags &
            (UMA_ZONE_INHERIT | UMA_ZFLAG_INHERIT));

        /*
         * Some internal zones don't have room allocated for the per cpu
         * caches.  If we're internal, bail out here.
         */
        if (keg->uk_flags & UMA_ZFLAG_INTERNAL) {
                KASSERT((zone->uz_flags & UMA_ZONE_SECONDARY) == 0,
                    ("Secondary zone requested UMA_ZFLAG_INTERNAL"));
                return (0);
        }

out:
        if ((arg->flags & UMA_ZONE_MAXBUCKET) == 0)
                zone->uz_count = bucket_select(zone->uz_size);
        else
                zone->uz_count = BUCKET_MAX;

        return (0);
}

/*
 * Keg header dtor.  This frees all data, destroys locks, frees the hash
 * table and removes the keg from the global list.
 *
 * Arguments/Returns follow uma_dtor specifications
 *      udata  unused
 */
static void
keg_dtor(void *arg, int size, void *udata)
{
        uma_keg_t keg;

        keg = (uma_keg_t)arg;
        KEG_LOCK(keg);
        if (keg->uk_free != 0) {
                printf("Freed UMA keg was not empty (%d items). "
                    " Lost %d pages of memory.\n",
                    keg->uk_free, keg->uk_pages);
        }
        KEG_UNLOCK(keg);

        hash_free(&keg->uk_hash);

        KEG_LOCK_FINI(keg);
}

/*
 * Zone header dtor.
 *
 * Arguments/Returns follow uma_dtor specifications
 *      udata  unused
 */
static void
zone_dtor(void *arg, int size, void *udata)
{
        uma_klink_t klink;
        uma_zone_t zone;
        uma_keg_t keg;

        zone = (uma_zone_t)arg;
        keg = zone_first_keg(zone);

        if (!(zone->uz_flags & UMA_ZFLAG_INTERNAL))
                cache_drain(zone);

        mtx_lock(&uma_mtx);
        LIST_REMOVE(zone, uz_link);
        mtx_unlock(&uma_mtx);
        /*
         * XXX there are some races here where
         * the zone can be drained but zone lock
         * released and then refilled before we
         * remove it... we dont care for now
         */
        zone_drain_wait(zone, M_WAITOK);
        /*
         * Unlink all of our kegs.
         */
        while ((klink = LIST_FIRST(&zone->uz_kegs)) != NULL) {
                klink->kl_keg = NULL;
                LIST_REMOVE(klink, kl_link);
                if (klink == &zone->uz_klink)
                        continue;
                free(klink, M_TEMP);
        }
        /*
         * We only destroy kegs from non secondary zones.
         */
        if (keg != NULL && (zone->uz_flags & UMA_ZONE_SECONDARY) == 0)  {
                mtx_lock(&uma_mtx);
                LIST_REMOVE(keg, uk_link);
                mtx_unlock(&uma_mtx);
                zone_free_item(kegs, keg, NULL, SKIP_NONE);
        }
        ZONE_LOCK_FINI(zone);
}

/*
 * Traverses every zone in the system and calls a callback
 *
 * Arguments:
 *      zfunc  A pointer to a function which accepts a zone
 *              as an argument.
 *
 * Returns:
 *      Nothing
 */
static void
zone_foreach(void (*zfunc)(uma_zone_t))
{
        uma_keg_t keg;
        uma_zone_t zone;

        mtx_lock(&uma_mtx);
        LIST_FOREACH(keg, &uma_kegs, uk_link) {
                LIST_FOREACH(zone, &keg->uk_zones, uz_link)
                        zfunc(zone);
        }
        mtx_unlock(&uma_mtx);
}

/* Public functions */
/* See uma.h */
void
uma_startup(void *bootmem, int boot_pages)
{
        struct uma_zctor_args args;
        uma_slab_t slab;
        u_int slabsize;
        int i;

#ifdef UMA_DEBUG
        printf("Creating uma keg headers zone and keg.\n");
#endif
        mtx_init(&uma_mtx, "UMA lock", NULL, MTX_DEF);

        /* "manually" create the initial zone */
        memset(&args, 0, sizeof(args));
        args.name = "UMA Kegs";
        args.size = sizeof(struct uma_keg);
        args.ctor = keg_ctor;
        args.dtor = keg_dtor;
        args.uminit = zero_init;
        args.fini = NULL;
        args.keg = &masterkeg;
        args.align = 32 - 1;
        args.flags = UMA_ZFLAG_INTERNAL;
        /* The initial zone has no Per cpu queues so it's smaller */
        zone_ctor(kegs, sizeof(struct uma_zone), &args, M_WAITOK);

#ifdef UMA_DEBUG
        printf("Filling boot free list.\n");
#endif
        for (i = 0; i < boot_pages; i++) {
                slab = (uma_slab_t)((uint8_t *)bootmem + (i * UMA_SLAB_SIZE));
                slab->us_data = (uint8_t *)slab;
                slab->us_flags = UMA_SLAB_BOOT;
                LIST_INSERT_HEAD(&uma_boot_pages, slab, us_link);
        }
        mtx_init(&uma_boot_pages_mtx, "UMA boot pages", NULL, MTX_DEF);

#ifdef UMA_DEBUG
        printf("Creating uma zone headers zone and keg.\n");
#endif
        args.name = "UMA Zones";
        args.size = sizeof(struct uma_zone) +
            (sizeof(struct uma_cache) * (mp_maxid + 1));
        args.ctor = zone_ctor;
        args.dtor = zone_dtor;
        args.uminit = zero_init;
        args.fini = NULL;
        args.keg = NULL;
        args.align = 32 - 1;
        args.flags = UMA_ZFLAG_INTERNAL;
        /* The initial zone has no Per cpu queues so it's smaller */
        zone_ctor(zones, sizeof(struct uma_zone), &args, M_WAITOK);

#ifdef UMA_DEBUG
        printf("Initializing pcpu cache locks.\n");
#endif
#ifdef UMA_DEBUG
        printf("Creating slab and hash zones.\n");
#endif

        /* Now make a zone for slab headers */
        slabzone = uma_zcreate("UMA Slabs",
                                sizeof(struct uma_slab),
                                NULL, NULL, NULL, NULL,
                                UMA_ALIGN_PTR, UMA_ZFLAG_INTERNAL);

        /*
         * We also create a zone for the bigger slabs with reference
         * counts in them, to accomodate UMA_ZONE_REFCNT zones.
         */
        slabsize = sizeof(struct uma_slab_refcnt);
        slabsize += uma_max_ipers_ref * sizeof(uint32_t);
        slabrefzone = uma_zcreate("UMA RCntSlabs",
                                  slabsize,
                                  NULL, NULL, NULL, NULL,
                                  UMA_ALIGN_PTR,
                                  UMA_ZFLAG_INTERNAL);

        hashzone = uma_zcreate("UMA Hash",
            sizeof(struct slabhead *) * UMA_HASH_SIZE_INIT,
            NULL, NULL, NULL, NULL,
            UMA_ALIGN_PTR, UMA_ZFLAG_INTERNAL);

        bucket_init();

        booted = UMA_STARTUP;

#ifdef UMA_DEBUG
        printf("UMA startup complete.\n");
#endif
}

/* see uma.h */
void
uma_startup2(void)
{
        booted = UMA_STARTUP2;
        bucket_enable();
#ifdef UMA_DEBUG
        printf("UMA startup2 complete.\n");
#endif
}

/*
 * Initialize our callout handle
 *
 */

static void
uma_startup3(void)
{
#ifdef UMA_DEBUG
        printf("Starting callout.\n");
#endif
        callout_init(&uma_callout, CALLOUT_MPSAFE);
        callout_reset(&uma_callout, UMA_TIMEOUT * hz, uma_timeout, NULL);
#ifdef UMA_DEBUG
        printf("UMA startup3 complete.\n");
#endif
}

static uma_keg_t
uma_kcreate(uma_zone_t zone, size_t size, uma_init uminit, uma_fini fini,
                int align, uint32_t flags)
{
        struct uma_kctor_args args;

        args.size = size;
        args.uminit = uminit;
        args.fini = fini;
        args.align = (align == UMA_ALIGN_CACHE) ? uma_align_cache : align;
        args.flags = flags;
        args.zone = zone;
        return (zone_alloc_item(kegs, &args, M_WAITOK));
}

/* See uma.h */
void
uma_set_align(int align)
{

        if (align != UMA_ALIGN_CACHE)
                uma_align_cache = align;
}

/* See uma.h */
uma_zone_t
uma_zcreate(const char *name, size_t size, uma_ctor ctor, uma_dtor dtor,
                uma_init uminit, uma_fini fini, int align, uint32_t flags)

{
        struct uma_zctor_args args;

        /* This stuff is essential for the zone ctor */
        memset(&args, 0, sizeof(args));
        args.name = name;
        args.size = size;
        args.ctor = ctor;
        args.dtor = dtor;
        args.uminit = uminit;
        args.fini = fini;
        args.align = align;
        args.flags = flags;
        args.keg = NULL;

        return (zone_alloc_item(zones, &args, M_WAITOK));
}

/* See uma.h */
uma_zone_t
uma_zsecond_create(char *name, uma_ctor ctor, uma_dtor dtor,
                    uma_init zinit, uma_fini zfini, uma_zone_t master)
{
        struct uma_zctor_args args;
        uma_keg_t keg;

        keg = zone_first_keg(master);
        memset(&args, 0, sizeof(args));
        args.name = name;
        args.size = keg->uk_size;
        args.ctor = ctor;
        args.dtor = dtor;
        args.uminit = zinit;
        args.fini = zfini;
        args.align = keg->uk_align;
        args.flags = keg->uk_flags | UMA_ZONE_SECONDARY;
        args.keg = keg;

        /* XXX Attaches only one keg of potentially many. */
        return (zone_alloc_item(zones, &args, M_WAITOK));
}

/* See uma.h */
uma_zone_t
uma_zcache_create(char *name, int size, uma_ctor ctor, uma_dtor dtor,
                    uma_init zinit, uma_fini zfini, uma_import zimport,
                    uma_release zrelease, void *arg, int flags)
{
        struct uma_zctor_args args;

        memset(&args, 0, sizeof(args));
        args.name = name;
        args.size = size;
        args.ctor = ctor;
        args.dtor = dtor;
        args.uminit = zinit;
        args.fini = zfini;
        args.import = zimport;
        args.release = zrelease;
        args.arg = arg;
        args.align = 0;
        args.flags = flags;

        return (zone_alloc_item(zones, &args, M_WAITOK));
}

static void
zone_lock_pair(uma_zone_t a, uma_zone_t b)
{
        if (a < b) {
                ZONE_LOCK(a);
                mtx_lock_flags(b->uz_lockptr, MTX_DUPOK);
        } else {
                ZONE_LOCK(b);
                mtx_lock_flags(a->uz_lockptr, MTX_DUPOK);
        }
}

static void
zone_unlock_pair(uma_zone_t a, uma_zone_t b)
{

        ZONE_UNLOCK(a);
        ZONE_UNLOCK(b);
}

int
uma_zsecond_add(uma_zone_t zone, uma_zone_t master)
{
        uma_klink_t klink;
        uma_klink_t kl;
        int error;

        error = 0;
        klink = malloc(sizeof(*klink), M_TEMP, M_WAITOK | M_ZERO);

        zone_lock_pair(zone, master);
        /*
         * zone must use vtoslab() to resolve objects and must already be
         * a secondary.
         */
        if ((zone->uz_flags & (UMA_ZONE_VTOSLAB | UMA_ZONE_SECONDARY))
            != (UMA_ZONE_VTOSLAB | UMA_ZONE_SECONDARY)) {
                error = EINVAL;
                goto out;
        }
        /*
         * The new master must also use vtoslab().
         */
        if ((zone->uz_flags & UMA_ZONE_VTOSLAB) != UMA_ZONE_VTOSLAB) {
                error = EINVAL;
                goto out;
        }
        /*
         * Both must either be refcnt, or not be refcnt.
         */
        if ((zone->uz_flags & UMA_ZONE_REFCNT) !=
            (master->uz_flags & UMA_ZONE_REFCNT)) {
                error = EINVAL;
                goto out;
        }
        /*
         * The underlying object must be the same size.  rsize
         * may be different.
         */
        if (master->uz_size != zone->uz_size) {
                error = E2BIG;
                goto out;
        }
        /*
         * Put it at the end of the list.
         */
        klink->kl_keg = zone_first_keg(master);
        LIST_FOREACH(kl, &zone->uz_kegs, kl_link) {
                if (LIST_NEXT(kl, kl_link) == NULL) {
                        LIST_INSERT_AFTER(kl, klink, kl_link);
                        break;
                }
        }
        klink = NULL;
        zone->uz_flags |= UMA_ZFLAG_MULTI;
        zone->uz_slab = zone_fetch_slab_multi;

out:
        zone_unlock_pair(zone, master);
        if (klink != NULL)
                free(klink, M_TEMP);

        return (error);
}


/* See uma.h */
void
uma_zdestroy(uma_zone_t zone)
{

        zone_free_item(zones, zone, NULL, SKIP_NONE);
}

/* See uma.h */
void *
uma_zalloc_arg(uma_zone_t zone, void *udata, int flags)
{
        void *item;
        uma_cache_t cache;
        uma_bucket_t bucket;
        int lockfail;
        int cpu;

        /* This is the fast path allocation */
#ifdef UMA_DEBUG_ALLOC_1
        printf("Allocating one item from %s(%p)\n", zone->uz_name, zone);
#endif
        CTR3(KTR_UMA, "uma_zalloc_arg thread %x zone %s flags %d", curthread,
            zone->uz_name, flags);

        if (flags & M_WAITOK) {
                WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                    "uma_zalloc_arg: zone \"%s\"", zone->uz_name);
        }
#ifdef DEBUG_MEMGUARD
        if (memguard_cmp_zone(zone)) {
                item = memguard_alloc(zone->uz_size, flags);
                if (item != NULL) {
                        /*
                         * Avoid conflict with the use-after-free
                         * protecting infrastructure from INVARIANTS.
                         */
                        if (zone->uz_init != NULL &&
                            zone->uz_init != mtrash_init &&
                            zone->uz_init(item, zone->uz_size, flags) != 0)
                                return (NULL);
                        if (zone->uz_ctor != NULL &&
                            zone->uz_ctor != mtrash_ctor &&
                            zone->uz_ctor(item, zone->uz_size, udata,
                            flags) != 0) {
                                zone->uz_fini(item, zone->uz_size);
                                return (NULL);
                        }
                        return (item);
                }
                /* This is unfortunate but should not be fatal. */
        }
#endif
        /*
         * If possible, allocate from the per-CPU cache.  There are two
         * requirements for safe access to the per-CPU cache: (1) the thread
         * accessing the cache must not be preempted or yield during access,
         * and (2) the thread must not migrate CPUs without switching which
         * cache it accesses.  We rely on a critical section to prevent
         * preemption and migration.  We release the critical section in
         * order to acquire the zone mutex if we are unable to allocate from
         * the current cache; when we re-acquire the critical section, we
         * must detect and handle migration if it has occurred.
         */
        critical_enter();
        cpu = curcpu;
        cache = &zone->uz_cpu[cpu];

zalloc_start:
        bucket = cache->uc_allocbucket;
        if (bucket != NULL && bucket->ub_cnt > 0) {
                bucket->ub_cnt--;
                item = bucket->ub_bucket[bucket->ub_cnt];
#ifdef INVARIANTS
                bucket->ub_bucket[bucket->ub_cnt] = NULL;
#endif
                KASSERT(item != NULL, ("uma_zalloc: Bucket pointer mangled."));
                cache->uc_allocs++;
                critical_exit();
                if (zone->uz_ctor != NULL &&
                    zone->uz_ctor(item, zone->uz_size, udata, flags) != 0) {
                        atomic_add_long(&zone->uz_fails, 1);
                        zone_free_item(zone, item, udata, SKIP_DTOR);
                        return (NULL);
                }
#ifdef INVARIANTS
                uma_dbg_alloc(zone, NULL, item);
#endif
                if (flags & M_ZERO)
                        bzero(item, zone->uz_size);
                return (item);
        }

        /*
         * We have run out of items in our alloc bucket.
         * See if we can switch with our free bucket.
         */
        bucket = cache->uc_freebucket;
        if (bucket != NULL && bucket->ub_cnt > 0) {
#ifdef UMA_DEBUG_ALLOC
                printf("uma_zalloc: Swapping empty with alloc.\n");
#endif
                cache->uc_freebucket = cache->uc_allocbucket;
                cache->uc_allocbucket = bucket;
                goto zalloc_start;
        }

        /*
         * Discard any empty allocation bucket while we hold no locks.
         */
        bucket = cache->uc_allocbucket;
        cache->uc_allocbucket = NULL;
        critical_exit();
        if (bucket != NULL)
                bucket_free(zone, bucket, udata);

        /* Short-circuit for zones without buckets and low memory. */
        if (zone->uz_count == 0 || bucketdisable)
                goto zalloc_item;

        /*
         * Attempt to retrieve the item from the per-CPU cache has failed, so
         * we must go back to the zone.  This requires the zone lock, so we
         * must drop the critical section, then re-acquire it when we go back
         * to the cache.  Since the critical section is released, we may be
         * preempted or migrate.  As such, make sure not to maintain any
         * thread-local state specific to the cache from prior to releasing
         * the critical section.
         */
        lockfail = 0;
        if (ZONE_TRYLOCK(zone) == 0) {
                /* Record contention to size the buckets. */
                ZONE_LOCK(zone);
                lockfail = 1;
        }
        critical_enter();
        cpu = curcpu;
        cache = &zone->uz_cpu[cpu];

        /*
         * Since we have locked the zone we may as well send back our stats.
         */
        atomic_add_long(&zone->uz_allocs, cache->uc_allocs);
        atomic_add_long(&zone->uz_frees, cache->uc_frees);
        cache->uc_allocs = 0;
        cache->uc_frees = 0;

        /* See if we lost the race to fill the cache. */
        if (cache->uc_allocbucket != NULL) {
                ZONE_UNLOCK(zone);
                goto zalloc_start;
        }

        /*
         * Check the zone's cache of buckets.
         */
        if ((bucket = LIST_FIRST(&zone->uz_buckets)) != NULL) {
                KASSERT(bucket->ub_cnt != 0,
                    ("uma_zalloc_arg: Returning an empty bucket."));

                LIST_REMOVE(bucket, ub_link);
                cache->uc_allocbucket = bucket;
                ZONE_UNLOCK(zone);
                goto zalloc_start;
        }
        /* We are no longer associated with this CPU. */
        critical_exit();

        /*
         * We bump the uz count when the cache size is insufficient to
         * handle the working set.
         */
        if (lockfail && zone->uz_count < BUCKET_MAX)
                zone->uz_count++;
        ZONE_UNLOCK(zone);

        /*
         * Now lets just fill a bucket and put it on the free list.  If that
         * works we'll restart the allocation from the begining and it
         * will use the just filled bucket.
         */
        bucket = zone_alloc_bucket(zone, udata, flags);
        if (bucket != NULL) {
                ZONE_LOCK(zone);
                critical_enter();
                cpu = curcpu;
                cache = &zone->uz_cpu[cpu];
                /*
                 * See if we lost the race or were migrated.  Cache the
                 * initialized bucket to make this less likely or claim
                 * the memory directly.
                 */
                if (cache->uc_allocbucket == NULL)
                        cache->uc_allocbucket = bucket;
                else
                        LIST_INSERT_HEAD(&zone->uz_buckets, bucket, ub_link);
                ZONE_UNLOCK(zone);
                goto zalloc_start;
        }

        /*
         * We may not be able to get a bucket so return an actual item.
         */
#ifdef UMA_DEBUG
        printf("uma_zalloc_arg: Bucketzone returned NULL\n");
#endif

zalloc_item:
        item = zone_alloc_item(zone, udata, flags);

        return (item);
}

static uma_slab_t
keg_fetch_slab(uma_keg_t keg, uma_zone_t zone, int flags)
{
        uma_slab_t slab;
        int reserve;

        mtx_assert(&keg->uk_lock, MA_OWNED);
        slab = NULL;
        reserve = 0;
        if ((flags & M_USE_RESERVE) == 0)
                reserve = keg->uk_reserve;

        for (;;) {
                /*
                 * Find a slab with some space.  Prefer slabs that are partially
                 * used over those that are totally full.  This helps to reduce
                 * fragmentation.
                 */
                if (keg->uk_free > reserve) {
                        if (!LIST_EMPTY(&keg->uk_part_slab)) {
                                slab = LIST_FIRST(&keg->uk_part_slab);
                        } else {
                                slab = LIST_FIRST(&keg->uk_free_slab);
                                LIST_REMOVE(slab, us_link);
                                LIST_INSERT_HEAD(&keg->uk_part_slab, slab,
                                    us_link);
                        }
                        MPASS(slab->us_keg == keg);
                        return (slab);
                }

                /*
                 * M_NOVM means don't ask at all!
                 */
                if (flags & M_NOVM)
                        break;

                if (keg->uk_maxpages && keg->uk_pages >= keg->uk_maxpages) {
                        keg->uk_flags |= UMA_ZFLAG_FULL;
                        /*
                         * If this is not a multi-zone, set the FULL bit.
                         * Otherwise slab_multi() takes care of it.
                         */
                        if ((zone->uz_flags & UMA_ZFLAG_MULTI) == 0) {
                                zone->uz_flags |= UMA_ZFLAG_FULL;
                                zone_log_warning(zone);
                        }
                        if (flags & M_NOWAIT)
                                break;
                        zone->uz_sleeps++;
                        msleep(keg, &keg->uk_lock, PVM, "keglimit", 0);
                        continue;
                }
                slab = keg_alloc_slab(keg, zone, flags);
                /*
                 * If we got a slab here it's safe to mark it partially used
                 * and return.  We assume that the caller is going to remove
                 * at least one item.
                 */
                if (slab) {
                        MPASS(slab->us_keg == keg);
                        LIST_INSERT_HEAD(&keg->uk_part_slab, slab, us_link);
                        return (slab);
                }
                /*
                 * We might not have been able to get a slab but another cpu
                 * could have while we were unlocked.  Check again before we
                 * fail.
                 */
                flags |= M_NOVM;
        }
        return (slab);
}

static uma_slab_t
zone_fetch_slab(uma_zone_t zone, uma_keg_t keg, int flags)
{
        uma_slab_t slab;

        if (keg == NULL) {
                keg = zone_first_keg(zone);
                KEG_LOCK(keg);
        }

        for (;;) {
                slab = keg_fetch_slab(keg, zone, flags);
                if (slab)
                        return (slab);
                if (flags & (M_NOWAIT | M_NOVM))
                        break;
        }
        KEG_UNLOCK(keg);
        return (NULL);
}

/*
 * uma_zone_fetch_slab_multi:  Fetches a slab from one available keg.  Returns
 * with the keg locked.  On NULL no lock is held.
 *
 * The last pointer is used to seed the search.  It is not required.
 */
static uma_slab_t
zone_fetch_slab_multi(uma_zone_t zone, uma_keg_t last, int rflags)
{
        uma_klink_t klink;
        uma_slab_t slab;
        uma_keg_t keg;
        int flags;
        int empty;
        int full;

        /*
         * Don't wait on the first pass.  This will skip limit tests
         * as well.  We don't want to block if we can find a provider
         * without blocking.
         */
        flags = (rflags & ~M_WAITOK) | M_NOWAIT;
        /*
         * Use the last slab allocated as a hint for where to start
         * the search.
         */
        if (last != NULL) {
                slab = keg_fetch_slab(last, zone, flags);
                if (slab)
                        return (slab);
                KEG_UNLOCK(last);
        }
        /*
         * Loop until we have a slab incase of transient failures
         * while M_WAITOK is specified.  I'm not sure this is 100%
         * required but we've done it for so long now.
         */
        for (;;) {
                empty = 0;
                full = 0;
                /*
                 * Search the available kegs for slabs.  Be careful to hold the
                 * correct lock while calling into the keg layer.
                 */
                LIST_FOREACH(klink, &zone->uz_kegs, kl_link) {
                        keg = klink->kl_keg;
                        KEG_LOCK(keg);
                        if ((keg->uk_flags & UMA_ZFLAG_FULL) == 0) {
                                slab = keg_fetch_slab(keg, zone, flags);
                                if (slab)
                                        return (slab);
                        }
                        if (keg->uk_flags & UMA_ZFLAG_FULL)
                                full++;
                        else
                                empty++;
                        KEG_UNLOCK(keg);
                }
                if (rflags & (M_NOWAIT | M_NOVM))
                        break;
                flags = rflags;
                /*
                 * All kegs are full.  XXX We can't atomically check all kegs
                 * and sleep so just sleep for a short period and retry.
                 */
                if (full && !empty) {
                        ZONE_LOCK(zone);
                        zone->uz_flags |= UMA_ZFLAG_FULL;
                        zone->uz_sleeps++;
                        zone_log_warning(zone);
                        msleep(zone, zone->uz_lockptr, PVM,
                            "zonelimit", hz/100);
                        zone->uz_flags &= ~UMA_ZFLAG_FULL;
                        ZONE_UNLOCK(zone);
                        continue;
                }
        }
        return (NULL);
}

static void *
slab_alloc_item(uma_keg_t keg, uma_slab_t slab)
{
        void *item;
        uint8_t freei;

        MPASS(keg == slab->us_keg);
        mtx_assert(&keg->uk_lock, MA_OWNED);

        freei = BIT_FFS(SLAB_SETSIZE, &slab->us_free) - 1;
        BIT_CLR(SLAB_SETSIZE, freei, &slab->us_free);
        item = slab->us_data + (keg->uk_rsize * freei);
        slab->us_freecount--;
        keg->uk_free--;

        /* Move this slab to the full list */
        if (slab->us_freecount == 0) {
                LIST_REMOVE(slab, us_link);
                LIST_INSERT_HEAD(&keg->uk_full_slab, slab, us_link);
        }

        return (item);
}

static int
zone_import(uma_zone_t zone, void **bucket, int max, int flags)
{
        uma_slab_t slab;
        uma_keg_t keg;
        int i;

        slab = NULL;
        keg = NULL;
        /* Try to keep the buckets totally full */
        for (i = 0; i < max; ) {
                if ((slab = zone->uz_slab(zone, keg, flags)) == NULL)
                        break;
                keg = slab->us_keg;
                while (slab->us_freecount && i < max) { 
                        bucket[i++] = slab_alloc_item(keg, slab);
                        if (keg->uk_free <= keg->uk_reserve)
                                break;
                }
                /* Don't grab more than one slab at a time. */
                flags &= ~M_WAITOK;
                flags |= M_NOWAIT;
        }
        if (slab != NULL)
                KEG_UNLOCK(keg);

        return i;
}

static uma_bucket_t
zone_alloc_bucket(uma_zone_t zone, void *udata, int flags)
{
        uma_bucket_t bucket;
        int max;

        /* Don't wait for buckets, preserve caller's NOVM setting. */
        bucket = bucket_alloc(zone, udata, M_NOWAIT | (flags & M_NOVM));
        if (bucket == NULL)
                goto out;

        max = MIN(bucket->ub_entries, zone->uz_count);
        bucket->ub_cnt = zone->uz_import(zone->uz_arg, bucket->ub_bucket,
            max, flags);

        /*
         * Initialize the memory if necessary.
         */
        if (bucket->ub_cnt != 0 && zone->uz_init != NULL) {
                int i;

                for (i = 0; i < bucket->ub_cnt; i++)
                        if (zone->uz_init(bucket->ub_bucket[i], zone->uz_size,
                            flags) != 0)
                                break;
                /*
                 * If we couldn't initialize the whole bucket, put the
                 * rest back onto the freelist.
                 */
                if (i != bucket->ub_cnt) {
                        zone->uz_release(zone->uz_arg, &bucket->ub_bucket[i],
                            bucket->ub_cnt - i);
#ifdef INVARIANTS
                        bzero(&bucket->ub_bucket[i],
                            sizeof(void *) * (bucket->ub_cnt - i));
#endif
                        bucket->ub_cnt = i;
                }
        }

out:
        if (bucket == NULL || bucket->ub_cnt == 0) {
                if (bucket != NULL)
                        bucket_free(zone, bucket, udata);
                atomic_add_long(&zone->uz_fails, 1);
                return (NULL);
        }

        return (bucket);
}

/*
 * Allocates a single item from a zone.
 *
 * Arguments
 *      zone   The zone to alloc for.
 *      udata  The data to be passed to the constructor.
 *      flags  M_WAITOK, M_NOWAIT, M_ZERO.
 *
 * Returns
 *      NULL if there is no memory and M_NOWAIT is set
 *      An item if successful
 */

static void *
zone_alloc_item(uma_zone_t zone, void *udata, int flags)
{
        void *item;

        item = NULL;

#ifdef UMA_DEBUG_ALLOC
        printf("INTERNAL: Allocating one item from %s(%p)\n", zone->uz_name, zone);
#endif
        if (zone->uz_import(zone->uz_arg, &item, 1, flags) != 1)
                goto fail;
        atomic_add_long(&zone->uz_allocs, 1);

        /*
         * We have to call both the zone's init (not the keg's init)
         * and the zone's ctor.  This is because the item is going from
         * a keg slab directly to the user, and the user is expecting it
         * to be both zone-init'd as well as zone-ctor'd.
         */
        if (zone->uz_init != NULL) {
                if (zone->uz_init(item, zone->uz_size, flags) != 0) {
                        zone_free_item(zone, item, udata, SKIP_FINI);
                        goto fail;
                }
        }
        if (zone->uz_ctor != NULL) {
                if (zone->uz_ctor(item, zone->uz_size, udata, flags) != 0) {
                        zone_free_item(zone, item, udata, SKIP_DTOR);
                        goto fail;
                }
        }
#ifdef INVARIANTS
        uma_dbg_alloc(zone, NULL, item);
#endif
        if (flags & M_ZERO)
                bzero(item, zone->uz_size);

        return (item);

fail:
        atomic_add_long(&zone->uz_fails, 1);
        return (NULL);
}

/* See uma.h */
void
uma_zfree_arg(uma_zone_t zone, void *item, void *udata)
{
        uma_cache_t cache;
        uma_bucket_t bucket;
        int cpu;

#ifdef UMA_DEBUG_ALLOC_1
        printf("Freeing item %p to %s(%p)\n", item, zone->uz_name, zone);
#endif
        CTR2(KTR_UMA, "uma_zfree_arg thread %x zone %s", curthread,
            zone->uz_name);

        /* uma_zfree(..., NULL) does nothing, to match free(9). */
        if (item == NULL)
                return;
#ifdef DEBUG_MEMGUARD
        if (is_memguard_addr(item)) {
                if (zone->uz_dtor != NULL && zone->uz_dtor != mtrash_dtor)
                        zone->uz_dtor(item, zone->uz_size, udata);
                if (zone->uz_fini != NULL && zone->uz_fini != mtrash_fini)
                        zone->uz_fini(item, zone->uz_size);
                memguard_free(item);
                return;
        }
#endif
#ifdef INVARIANTS
        if (zone->uz_flags & UMA_ZONE_MALLOC)
                uma_dbg_free(zone, udata, item);
        else
                uma_dbg_free(zone, NULL, item);
#endif
        if (zone->uz_dtor != NULL)
                zone->uz_dtor(item, zone->uz_size, udata);

        /*
         * The race here is acceptable.  If we miss it we'll just have to wait
         * a little longer for the limits to be reset.
         */
        if (zone->uz_flags & UMA_ZFLAG_FULL)
                goto zfree_item;

        /*
         * If possible, free to the per-CPU cache.  There are two
         * requirements for safe access to the per-CPU cache: (1) the thread
         * accessing the cache must not be preempted or yield during access,
         * and (2) the thread must not migrate CPUs without switching which
         * cache it accesses.  We rely on a critical section to prevent
         * preemption and migration.  We release the critical section in
         * order to acquire the zone mutex if we are unable to free to the
         * current cache; when we re-acquire the critical section, we must
         * detect and handle migration if it has occurred.
         */
zfree_restart:
        critical_enter();
        cpu = curcpu;
        cache = &zone->uz_cpu[cpu];

zfree_start:
        /*
         * Try to free into the allocbucket first to give LIFO ordering
         * for cache-hot datastructures.  Spill over into the freebucket
         * if necessary.  Alloc will swap them if one runs dry.
         */
        bucket = cache->uc_allocbucket;
        if (bucket == NULL || bucket->ub_cnt >= bucket->ub_entries)
                bucket = cache->uc_freebucket;
        if (bucket != NULL && bucket->ub_cnt < bucket->ub_entries) {
                KASSERT(bucket->ub_bucket[bucket->ub_cnt] == NULL,
                    ("uma_zfree: Freeing to non free bucket index."));
                bucket->ub_bucket[bucket->ub_cnt] = item;
                bucket->ub_cnt++;
                cache->uc_frees++;
                critical_exit();
                return;
        }

        /*
         * We must go back the zone, which requires acquiring the zone lock,
         * which in turn means we must release and re-acquire the critical
         * section.  Since the critical section is released, we may be
         * preempted or migrate.  As such, make sure not to maintain any
         * thread-local state specific to the cache from prior to releasing
         * the critical section.
         */
        critical_exit();
        if (zone->uz_count == 0 || bucketdisable)
                goto zfree_item;

        ZONE_LOCK(zone);
        critical_enter();
        cpu = curcpu;
        cache = &zone->uz_cpu[cpu];

        /*
         * Since we have locked the zone we may as well send back our stats.
         */
        atomic_add_long(&zone->uz_allocs, cache->uc_allocs);
        atomic_add_long(&zone->uz_frees, cache->uc_frees);
        cache->uc_allocs = 0;
        cache->uc_frees = 0;

        bucket = cache->uc_freebucket;
        if (bucket != NULL && bucket->ub_cnt < bucket->ub_entries) {
                ZONE_UNLOCK(zone);
                goto zfree_start;
        }
        cache->uc_freebucket = NULL;

        /* Can we throw this on the zone full list? */
        if (bucket != NULL) {
#ifdef UMA_DEBUG_ALLOC
                printf("uma_zfree: Putting old bucket on the free list.\n");
#endif
                /* ub_cnt is pointing to the last free item */
                KASSERT(bucket->ub_cnt != 0,
                    ("uma_zfree: Attempting to insert an empty bucket onto the full list.\n"));
                LIST_INSERT_HEAD(&zone->uz_buckets, bucket, ub_link);
        }

        /* We are no longer associated with this CPU. */
        critical_exit();

        /* And the zone.. */
        ZONE_UNLOCK(zone);

#ifdef UMA_DEBUG_ALLOC
        printf("uma_zfree: Allocating new free bucket.\n");
#endif
        bucket = bucket_alloc(zone, udata, M_NOWAIT);
        if (bucket) {
                critical_enter();
                cpu = curcpu;
                cache = &zone->uz_cpu[cpu];
                if (cache->uc_freebucket == NULL) {
                        cache->uc_freebucket = bucket;
                        goto zfree_start;
                }
                /*
                 * We lost the race, start over.  We have to drop our
                 * critical section to free the bucket.
                 */
                critical_exit();
                bucket_free(zone, bucket, udata);
                goto zfree_restart;
        }

        /*
         * If nothing else caught this, we'll just do an internal free.
         */
zfree_item:
        zone_free_item(zone, item, udata, SKIP_DTOR);

        return;
}

static void
slab_free_item(uma_keg_t keg, uma_slab_t slab, void *item)
{
        uint8_t freei;

        mtx_assert(&keg->uk_lock, MA_OWNED);
        MPASS(keg == slab->us_keg);

        /* Do we need to remove from any lists? */
        if (slab->us_freecount+1 == keg->uk_ipers) {
                LIST_REMOVE(slab, us_link);
                LIST_INSERT_HEAD(&keg->uk_free_slab, slab, us_link);
        } else if (slab->us_freecount == 0) {
                LIST_REMOVE(slab, us_link);
                LIST_INSERT_HEAD(&keg->uk_part_slab, slab, us_link);
        }

        /* Slab management. */
        freei = ((uintptr_t)item - (uintptr_t)slab->us_data) / keg->uk_rsize;
        BIT_SET(SLAB_SETSIZE, freei, &slab->us_free);
        slab->us_freecount++;

        /* Keg statistics. */
        keg->uk_free++;
}

static void
zone_release(uma_zone_t zone, void **bucket, int cnt)
{
        void *item;
        uma_slab_t slab;
        uma_keg_t keg;
        uint8_t *mem;
        int clearfull;
        int i;

        clearfull = 0;
        keg = zone_first_keg(zone);
        KEG_LOCK(keg);
        for (i = 0; i < cnt; i++) {
                item = bucket[i];
                if (!(zone->uz_flags & UMA_ZONE_VTOSLAB)) {
                        mem = (uint8_t *)((uintptr_t)item & (~UMA_SLAB_MASK));
                        if (zone->uz_flags & UMA_ZONE_HASH) {
                                slab = hash_sfind(&keg->uk_hash, mem);
                        } else {
                                mem += keg->uk_pgoff;
                                slab = (uma_slab_t)mem;
                        }
                } else {
                        slab = vtoslab((vm_offset_t)item);
                        if (slab->us_keg != keg) {
                                KEG_UNLOCK(keg);
                                keg = slab->us_keg;
                                KEG_LOCK(keg);
                        }
                }
                slab_free_item(keg, slab, item);
                if (keg->uk_flags & UMA_ZFLAG_FULL) {
                        if (keg->uk_pages < keg->uk_maxpages) {
                                keg->uk_flags &= ~UMA_ZFLAG_FULL;
                                clearfull = 1;
                        }

                        /* 
                         * We can handle one more allocation. Since we're
                         * clearing ZFLAG_FULL, wake up all procs blocked
                         * on pages. This should be uncommon, so keeping this
                         * simple for now (rather than adding count of blocked 
                         * threads etc).
                         */
                        wakeup(keg);
                }
        }
        KEG_UNLOCK(keg);
        if (clearfull) {
                ZONE_LOCK(zone);
                zone->uz_flags &= ~UMA_ZFLAG_FULL;
                wakeup(zone);
                ZONE_UNLOCK(zone);
        }

}

/*
 * Frees a single item to any zone.
 *
 * Arguments:
 *      zone   The zone to free to
 *      item   The item we're freeing
 *      udata  User supplied data for the dtor
 *      skip   Skip dtors and finis
 */
static void
zone_free_item(uma_zone_t zone, void *item, void *udata, enum zfreeskip skip)
{

#ifdef INVARIANTS
        if (skip == SKIP_NONE) {
                if (zone->uz_flags & UMA_ZONE_MALLOC)
                        uma_dbg_free(zone, udata, item);
                else
                        uma_dbg_free(zone, NULL, item);
        }
#endif
        if (skip < SKIP_DTOR && zone->uz_dtor)
                zone->uz_dtor(item, zone->uz_size, udata);

        if (skip < SKIP_FINI && zone->uz_fini)
                zone->uz_fini(item, zone->uz_size);

        atomic_add_long(&zone->uz_frees, 1);
        zone->uz_release(zone->uz_arg, &item, 1);
}

/* See uma.h */
int
uma_zone_set_max(uma_zone_t zone, int nitems)
{
        uma_keg_t keg;

        keg = zone_first_keg(zone);
        if (keg == NULL)
                return (0);
        KEG_LOCK(keg);
        keg->uk_maxpages = (nitems / keg->uk_ipers) * keg->uk_ppera;
        if (keg->uk_maxpages * keg->uk_ipers < nitems)
                keg->uk_maxpages += keg->uk_ppera;
        nitems = keg->uk_maxpages * keg->uk_ipers;
        KEG_UNLOCK(keg);

        return (nitems);
}

/* See uma.h */
int
uma_zone_get_max(uma_zone_t zone)
{
        int nitems;
        uma_keg_t keg;

        keg = zone_first_keg(zone);
        if (keg == NULL)
                return (0);
        KEG_LOCK(keg);
        nitems = keg->uk_maxpages * keg->uk_ipers;
        KEG_UNLOCK(keg);

        return (nitems);
}

/* See uma.h */
void
uma_zone_set_warning(uma_zone_t zone, const char *warning)
{

        ZONE_LOCK(zone);
        zone->uz_warning = warning;
        ZONE_UNLOCK(zone);
}

/* See uma.h */
int
uma_zone_get_cur(uma_zone_t zone)
{
        int64_t nitems;
        u_int i;

        ZONE_LOCK(zone);
        nitems = zone->uz_allocs - zone->uz_frees;
        CPU_FOREACH(i) {
                /*
                 * See the comment in sysctl_vm_zone_stats() regarding the
                 * safety of accessing the per-cpu caches. With the zone lock
                 * held, it is safe, but can potentially result in stale data.
                 */
                nitems += zone->uz_cpu[i].uc_allocs -
                    zone->uz_cpu[i].uc_frees;
        }
        ZONE_UNLOCK(zone);

        return (nitems < 0 ? 0 : nitems);
}

/* See uma.h */
void
uma_zone_set_init(uma_zone_t zone, uma_init uminit)
{
        uma_keg_t keg;

        keg = zone_first_keg(zone);
        KASSERT(keg != NULL, ("uma_zone_set_init: Invalid zone type"));
        KEG_LOCK(keg);
        KASSERT(keg->uk_pages == 0,
            ("uma_zone_set_init on non-empty keg"));
        keg->uk_init = uminit;
        KEG_UNLOCK(keg);
}

/* See uma.h */
void
uma_zone_set_fini(uma_zone_t zone, uma_fini fini)
{
        uma_keg_t keg;

        keg = zone_first_keg(zone);
        KASSERT(keg != NULL, ("uma_zone_set_init: Invalid zone type"));
        KEG_LOCK(keg);
        KASSERT(keg->uk_pages == 0,
            ("uma_zone_set_fini on non-empty keg"));
        keg->uk_fini = fini;
        KEG_UNLOCK(keg);
}

/* See uma.h */
void
uma_zone_set_zinit(uma_zone_t zone, uma_init zinit)
{

        ZONE_LOCK(zone);
        KASSERT(zone_first_keg(zone)->uk_pages == 0,
            ("uma_zone_set_zinit on non-empty keg"));
        zone->uz_init = zinit;
        ZONE_UNLOCK(zone);
}

/* See uma.h */
void
uma_zone_set_zfini(uma_zone_t zone, uma_fini zfini)
{

        ZONE_LOCK(zone);
        KASSERT(zone_first_keg(zone)->uk_pages == 0,
            ("uma_zone_set_zfini on non-empty keg"));
        zone->uz_fini = zfini;
        ZONE_UNLOCK(zone);
}

/* See uma.h */
/* XXX uk_freef is not actually used with the zone locked */
void
uma_zone_set_freef(uma_zone_t zone, uma_free freef)
{
        uma_keg_t keg;

        keg = zone_first_keg(zone);
        KASSERT(keg != NULL, ("uma_zone_set_init: Invalid zone type"));
        KEG_LOCK(keg);
        keg->uk_freef = freef;
        KEG_UNLOCK(keg);
}

/* See uma.h */
/* XXX uk_allocf is not actually used with the zone locked */
void
uma_zone_set_allocf(uma_zone_t zone, uma_alloc allocf)
{
        uma_keg_t keg;

        keg = zone_first_keg(zone);
        KEG_LOCK(keg);
        keg->uk_allocf = allocf;
        KEG_UNLOCK(keg);
}

/* See uma.h */
void
uma_zone_reserve(uma_zone_t zone, int items)
{
        uma_keg_t keg;

        keg = zone_first_keg(zone);
        if (keg == NULL)
                return;
        KEG_LOCK(keg);
        keg->uk_reserve = items;
        KEG_UNLOCK(keg);

        return;
}

/* See uma.h */
int
uma_zone_reserve_kva(uma_zone_t zone, int count)
{
        uma_keg_t keg;
        vm_offset_t kva;
        int pages;

        keg = zone_first_keg(zone);
        if (keg == NULL)
                return (0);
        pages = count / keg->uk_ipers;

        if (pages * keg->uk_ipers < count)
                pages++;

#ifdef UMA_MD_SMALL_ALLOC
        if (keg->uk_ppera > 1) {
#else
        if (1) {
#endif
                kva = kva_alloc(pages * UMA_SLAB_SIZE);
                if (kva == 0)
                        return (0);
        } else
                kva = 0;
        KEG_LOCK(keg);
        keg->uk_kva = kva;
        keg->uk_offset = 0;
        keg->uk_maxpages = pages;
#ifdef UMA_MD_SMALL_ALLOC
        keg->uk_allocf = (keg->uk_ppera > 1) ? noobj_alloc : uma_small_alloc;
#else
        keg->uk_allocf = noobj_alloc;
#endif
        keg->uk_flags |= UMA_ZONE_NOFREE;
        KEG_UNLOCK(keg);

        return (1);
}

/* See uma.h */
void
uma_prealloc(uma_zone_t zone, int items)
{
        int slabs;
        uma_slab_t slab;
        uma_keg_t keg;

        keg = zone_first_keg(zone);
        if (keg == NULL)
                return;
        KEG_LOCK(keg);
        slabs = items / keg->uk_ipers;
        if (slabs * keg->uk_ipers < items)
                slabs++;
        while (slabs > 0) {
                slab = keg_alloc_slab(keg, zone, M_WAITOK);
                if (slab == NULL)
                        break;
                MPASS(slab->us_keg == keg);
                LIST_INSERT_HEAD(&keg->uk_free_slab, slab, us_link);
                slabs--;
        }
        KEG_UNLOCK(keg);
}

/* See uma.h */
uint32_t *
uma_find_refcnt(uma_zone_t zone, void *item)
{
        uma_slabrefcnt_t slabref;
        uma_slab_t slab;
        uma_keg_t keg;
        uint32_t *refcnt;
        int idx;

        slab = vtoslab((vm_offset_t)item & (~UMA_SLAB_MASK));
        slabref = (uma_slabrefcnt_t)slab;
        keg = slab->us_keg;
        KASSERT(keg->uk_flags & UMA_ZONE_REFCNT,
            ("uma_find_refcnt(): zone possibly not UMA_ZONE_REFCNT"));
        idx = ((uintptr_t)item - (uintptr_t)slab->us_data) / keg->uk_rsize;
        refcnt = &slabref->us_refcnt[idx];
        return refcnt;
}

/* See uma.h */
void
uma_reclaim(void)
{
#ifdef UMA_DEBUG
        printf("UMA: vm asked us to release pages!\n");
#endif
        bucket_enable();
        zone_foreach(zone_drain);
        /*
         * Some slabs may have been freed but this zone will be visited early
         * we visit again so that we can free pages that are empty once other
         * zones are drained.  We have to do the same for buckets.
         */
        zone_drain(slabzone);
        zone_drain(slabrefzone);
        bucket_zone_drain();
}

/* See uma.h */
int
uma_zone_exhausted(uma_zone_t zone)
{
        int full;

        ZONE_LOCK(zone);
        full = (zone->uz_flags & UMA_ZFLAG_FULL);
        ZONE_UNLOCK(zone);
        return (full);  
}

int
uma_zone_exhausted_nolock(uma_zone_t zone)
{
        return (zone->uz_flags & UMA_ZFLAG_FULL);
}

void *
uma_large_malloc(int size, int wait)
{
        void *mem;
        uma_slab_t slab;
        uint8_t flags;

        slab = zone_alloc_item(slabzone, NULL, wait);
        if (slab == NULL)
                return (NULL);
        mem = page_alloc(NULL, size, &flags, wait);
        if (mem) {
                vsetslab((vm_offset_t)mem, slab);
                slab->us_data = mem;
                slab->us_flags = flags | UMA_SLAB_MALLOC;
                slab->us_size = size;
        } else {
                zone_free_item(slabzone, slab, NULL, SKIP_NONE);
        }

        return (mem);
}

void
uma_large_free(uma_slab_t slab)
{

        page_free(slab->us_data, slab->us_size, slab->us_flags);
        zone_free_item(slabzone, slab, NULL, SKIP_NONE);
}

void
uma_print_stats(void)
{
        zone_foreach(uma_print_zone);
}

static void
slab_print(uma_slab_t slab)
{
        printf("slab: keg %p, data %p, freecount %d\n",
                slab->us_keg, slab->us_data, slab->us_freecount);
}

static void
cache_print(uma_cache_t cache)
{
        printf("alloc: %p(%d), free: %p(%d)\n",
                cache->uc_allocbucket,
                cache->uc_allocbucket?cache->uc_allocbucket->ub_cnt:0,
                cache->uc_freebucket,
                cache->uc_freebucket?cache->uc_freebucket->ub_cnt:0);
}

static void
uma_print_keg(uma_keg_t keg)
{
        uma_slab_t slab;

        printf("keg: %s(%p) size %d(%d) flags %#x ipers %d ppera %d "
            "out %d free %d limit %d\n",
            keg->uk_name, keg, keg->uk_size, keg->uk_rsize, keg->uk_flags,
            keg->uk_ipers, keg->uk_ppera,
            (keg->uk_ipers * keg->uk_pages) - keg->uk_free, keg->uk_free,
            (keg->uk_maxpages / keg->uk_ppera) * keg->uk_ipers);
        printf("Part slabs:\n");
        LIST_FOREACH(slab, &keg->uk_part_slab, us_link)
                slab_print(slab);
        printf("Free slabs:\n");
        LIST_FOREACH(slab, &keg->uk_free_slab, us_link)
                slab_print(slab);
        printf("Full slabs:\n");
        LIST_FOREACH(slab, &keg->uk_full_slab, us_link)
                slab_print(slab);
}

void
uma_print_zone(uma_zone_t zone)
{
        uma_cache_t cache;
        uma_klink_t kl;
        int i;

        printf("zone: %s(%p) size %d flags %#x\n",
            zone->uz_name, zone, zone->uz_size, zone->uz_flags);
        LIST_FOREACH(kl, &zone->uz_kegs, kl_link)
                uma_print_keg(kl->kl_keg);
        CPU_FOREACH(i) {
                cache = &zone->uz_cpu[i];
                printf("CPU %d Cache:\n", i);
                cache_print(cache);
        }
}

#ifdef DDB
/*
 * Generate statistics across both the zone and its per-cpu cache's.  Return
 * desired statistics if the pointer is non-NULL for that statistic.
 *
 * Note: does not update the zone statistics, as it can't safely clear the
 * per-CPU cache statistic.
 *
 * XXXRW: Following the uc_allocbucket and uc_freebucket pointers here isn't
 * safe from off-CPU; we should modify the caches to track this information
 * directly so that we don't have to.
 */
static void
uma_zone_sumstat(uma_zone_t z, int *cachefreep, uint64_t *allocsp,
    uint64_t *freesp, uint64_t *sleepsp)
{
        uma_cache_t cache;
        uint64_t allocs, frees, sleeps;
        int cachefree, cpu;

        allocs = frees = sleeps = 0;
        cachefree = 0;
        CPU_FOREACH(cpu) {
                cache = &z->uz_cpu[cpu];
                if (cache->uc_allocbucket != NULL)
                        cachefree += cache->uc_allocbucket->ub_cnt;
                if (cache->uc_freebucket != NULL)
                        cachefree += cache->uc_freebucket->ub_cnt;
                allocs += cache->uc_allocs;
                frees += cache->uc_frees;
        }
        allocs += z->uz_allocs;
        frees += z->uz_frees;
        sleeps += z->uz_sleeps;
        if (cachefreep != NULL)
                *cachefreep = cachefree;
        if (allocsp != NULL)
                *allocsp = allocs;
        if (freesp != NULL)
                *freesp = frees;
        if (sleepsp != NULL)
                *sleepsp = sleeps;
}
#endif /* DDB */

static int
sysctl_vm_zone_count(SYSCTL_HANDLER_ARGS)
{
        uma_keg_t kz;
        uma_zone_t z;
        int count;

        count = 0;
        mtx_lock(&uma_mtx);
        LIST_FOREACH(kz, &uma_kegs, uk_link) {
                LIST_FOREACH(z, &kz->uk_zones, uz_link)
                        count++;
        }
        mtx_unlock(&uma_mtx);
        return (sysctl_handle_int(oidp, &count, 0, req));
}

static int
sysctl_vm_zone_stats(SYSCTL_HANDLER_ARGS)
{
        struct uma_stream_header ush;
        struct uma_type_header uth;
        struct uma_percpu_stat ups;
        uma_bucket_t bucket;
        struct sbuf sbuf;
        uma_cache_t cache;
        uma_klink_t kl;
        uma_keg_t kz;
        uma_zone_t z;
        uma_keg_t k;
        int count, error, i;

        error = sysctl_wire_old_buffer(req, 0);
        if (error != 0)
                return (error);
        sbuf_new_for_sysctl(&sbuf, NULL, 128, req);

        count = 0;
        mtx_lock(&uma_mtx);
        LIST_FOREACH(kz, &uma_kegs, uk_link) {
                LIST_FOREACH(z, &kz->uk_zones, uz_link)
                        count++;
        }

        /*
         * Insert stream header.
         */
        bzero(&ush, sizeof(ush));
        ush.ush_version = UMA_STREAM_VERSION;
        ush.ush_maxcpus = (mp_maxid + 1);
        ush.ush_count = count;
        (void)sbuf_bcat(&sbuf, &ush, sizeof(ush));

        LIST_FOREACH(kz, &uma_kegs, uk_link) {
                LIST_FOREACH(z, &kz->uk_zones, uz_link) {
                        bzero(&uth, sizeof(uth));
                        ZONE_LOCK(z);
                        strlcpy(uth.uth_name, z->uz_name, UTH_MAX_NAME);
                        uth.uth_align = kz->uk_align;
                        uth.uth_size = kz->uk_size;
                        uth.uth_rsize = kz->uk_rsize;
                        LIST_FOREACH(kl, &z->uz_kegs, kl_link) {
                                k = kl->kl_keg;
                                uth.uth_maxpages += k->uk_maxpages;
                                uth.uth_pages += k->uk_pages;
                                uth.uth_keg_free += k->uk_free;
                                uth.uth_limit = (k->uk_maxpages / k->uk_ppera)
                                    * k->uk_ipers;
                        }

                        /*
                         * A zone is secondary is it is not the first entry
                         * on the keg's zone list.
                         */
                        if ((z->uz_flags & UMA_ZONE_SECONDARY) &&
                            (LIST_FIRST(&kz->uk_zones) != z))
                                uth.uth_zone_flags = UTH_ZONE_SECONDARY;

                        LIST_FOREACH(bucket, &z->uz_buckets, ub_link)
                                uth.uth_zone_free += bucket->ub_cnt;
                        uth.uth_allocs = z->uz_allocs;
                        uth.uth_frees = z->uz_frees;
                        uth.uth_fails = z->uz_fails;
                        uth.uth_sleeps = z->uz_sleeps;
                        (void)sbuf_bcat(&sbuf, &uth, sizeof(uth));
                        /*
                         * While it is not normally safe to access the cache
                         * bucket pointers while not on the CPU that owns the
                         * cache, we only allow the pointers to be exchanged
                         * without the zone lock held, not invalidated, so
                         * accept the possible race associated with bucket
                         * exchange during monitoring.
                         */
                        for (i = 0; i < (mp_maxid + 1); i++) {
                                bzero(&ups, sizeof(ups));
                                if (kz->uk_flags & UMA_ZFLAG_INTERNAL)
                                        goto skip;
                                if (CPU_ABSENT(i))
                                        goto skip;
                                cache = &z->uz_cpu[i];
                                if (cache->uc_allocbucket != NULL)
                                        ups.ups_cache_free +=
                                            cache->uc_allocbucket->ub_cnt;
                                if (cache->uc_freebucket != NULL)
                                        ups.ups_cache_free +=
                                            cache->uc_freebucket->ub_cnt;
                                ups.ups_allocs = cache->uc_allocs;
                                ups.ups_frees = cache->uc_frees;
skip:
                                (void)sbuf_bcat(&sbuf, &ups, sizeof(ups));
                        }
                        ZONE_UNLOCK(z);
                }
        }
        mtx_unlock(&uma_mtx);
        error = sbuf_finish(&sbuf);
        sbuf_delete(&sbuf);
        return (error);
}

#ifdef DDB
DB_SHOW_COMMAND(uma, db_show_uma)
{
        uint64_t allocs, frees, sleeps;
        uma_bucket_t bucket;
        uma_keg_t kz;
        uma_zone_t z;
        int cachefree;

        db_printf("%18s %8s %8s %8s %12s %8s\n", "Zone", "Size", "Used", "Free",
            "Requests", "Sleeps");
        LIST_FOREACH(kz, &uma_kegs, uk_link) {
                LIST_FOREACH(z, &kz->uk_zones, uz_link) {
                        if (kz->uk_flags & UMA_ZFLAG_INTERNAL) {
                                allocs = z->uz_allocs;
                                frees = z->uz_frees;
                                sleeps = z->uz_sleeps;
                                cachefree = 0;
                        } else
                                uma_zone_sumstat(z, &cachefree, &allocs,
                                    &frees, &sleeps);
                        if (!((z->uz_flags & UMA_ZONE_SECONDARY) &&
                            (LIST_FIRST(&kz->uk_zones) != z)))
                                cachefree += kz->uk_free;
                        LIST_FOREACH(bucket, &z->uz_buckets, ub_link)
                                cachefree += bucket->ub_cnt;
                        db_printf("%18s %8ju %8jd %8d %12ju %8ju\n", z->uz_name,
                            (uintmax_t)kz->uk_size,
                            (intmax_t)(allocs - frees), cachefree,
                            (uintmax_t)allocs, sleeps);
                        if (db_pager_quit)
                                return;
                }
        }
}
#endif