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Revision 1.66, Fri Mar 8 20:48:41 2002 UTC (12 years, 1 month ago) by thorpej
Branch: MAIN
Changes since 1.65: +286 -160 lines

Pool deals fairly well with physical memory shortage, but it doesn't
deal with shortages of the VM maps where the backing pages are mapped
(usually kmem_map).  Try to deal with this:

* Group all information about the backend allocator for a pool in a
  separate structure.  The pool references this structure, rather than
  the individual fields.
* Change the pool_init() API accordingly, and adjust all callers.
* Link all pools using the same backend allocator on a list.
* The backend allocator is responsible for waiting for physical memory
  to become available, but will still fail if it cannot callocate KVA
  space for the pages.  If this happens, carefully drain all pools using
  the same backend allocator, so that some KVA space can be freed.
* Change pool_reclaim() to indicate if it actually succeeded in freeing
  some pages, and use that information to make draining easier and more
  efficient.
* Get rid of PR_URGENT.  There was only one use of it, and it could be
  dealt with by the caller.

From art@openbsd.org.

/*	$NetBSD: subr_pool.c,v 1.66 2002/03/08 20:48:41 thorpej Exp $	*/

/*-
 * Copyright (c) 1997, 1999, 2000 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Paul Kranenburg; by Jason R. Thorpe of the Numerical Aerospace
 * Simulation Facility, NASA Ames Research Center.
 *
 * 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, 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the NetBSD
 *	Foundation, Inc. and its contributors.
 * 4. Neither the name of The NetBSD Foundation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``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 FOUNDATION OR CONTRIBUTORS
 * 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.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: subr_pool.c,v 1.66 2002/03/08 20:48:41 thorpej Exp $");

#include "opt_pool.h"
#include "opt_poollog.h"
#include "opt_lockdebug.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/errno.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/lock.h>
#include <sys/pool.h>
#include <sys/syslog.h>

#include <uvm/uvm.h>

/*
 * Pool resource management utility.
 *
 * Memory is allocated in pages which are split into pieces according
 * to the pool item size. Each page is kept on a list headed by `pr_pagelist'
 * in the pool structure and the individual pool items are on a linked list
 * headed by `ph_itemlist' in each page header. The memory for building
 * the page list is either taken from the allocated pages themselves (for
 * small pool items) or taken from an internal pool of page headers (`phpool').
 */

/* List of all pools */
TAILQ_HEAD(,pool) pool_head = TAILQ_HEAD_INITIALIZER(pool_head);

/* Private pool for page header structures */
static struct pool phpool;

#ifdef POOL_SUBPAGE
/* Pool of subpages for use by normal pools. */
static struct pool psppool;
#endif

/* # of seconds to retain page after last use */
int pool_inactive_time = 10;

/* Next candidate for drainage (see pool_drain()) */
static struct pool	*drainpp;

/* This spin lock protects both pool_head and drainpp. */
struct simplelock pool_head_slock = SIMPLELOCK_INITIALIZER;

struct pool_item_header {
	/* Page headers */
	TAILQ_ENTRY(pool_item_header)
				ph_pagelist;	/* pool page list */
	TAILQ_HEAD(,pool_item)	ph_itemlist;	/* chunk list for this page */
	LIST_ENTRY(pool_item_header)
				ph_hashlist;	/* Off-page page headers */
	int			ph_nmissing;	/* # of chunks in use */
	caddr_t			ph_page;	/* this page's address */
	struct timeval		ph_time;	/* last referenced */
};
TAILQ_HEAD(pool_pagelist,pool_item_header);

struct pool_item {
#ifdef DIAGNOSTIC
	int pi_magic;
#endif
#define	PI_MAGIC 0xdeadbeef
	/* Other entries use only this list entry */
	TAILQ_ENTRY(pool_item)	pi_list;
};

#define	PR_HASH_INDEX(pp,addr) \
	(((u_long)(addr) >> (pp)->pr_alloc->pa_pageshift) & \
	 (PR_HASHTABSIZE - 1))

#define	POOL_NEEDS_CATCHUP(pp)						\
	((pp)->pr_nitems < (pp)->pr_minitems)

/*
 * Pool cache management.
 *
 * Pool caches provide a way for constructed objects to be cached by the
 * pool subsystem.  This can lead to performance improvements by avoiding
 * needless object construction/destruction; it is deferred until absolutely
 * necessary.
 *
 * Caches are grouped into cache groups.  Each cache group references
 * up to 16 constructed objects.  When a cache allocates an object
 * from the pool, it calls the object's constructor and places it into
 * a cache group.  When a cache group frees an object back to the pool,
 * it first calls the object's destructor.  This allows the object to
 * persist in constructed form while freed to the cache.
 *
 * Multiple caches may exist for each pool.  This allows a single
 * object type to have multiple constructed forms.  The pool references
 * each cache, so that when a pool is drained by the pagedaemon, it can
 * drain each individual cache as well.  Each time a cache is drained,
 * the most idle cache group is freed to the pool in its entirety.
 *
 * Pool caches are layed on top of pools.  By layering them, we can avoid
 * the complexity of cache management for pools which would not benefit
 * from it.
 */

/* The cache group pool. */
static struct pool pcgpool;

/* The pool cache group. */
#define	PCG_NOBJECTS		16
struct pool_cache_group {
	TAILQ_ENTRY(pool_cache_group)
		pcg_list;	/* link in the pool cache's group list */
	u_int	pcg_avail;	/* # available objects */
				/* pointers to the objects */
	void	*pcg_objects[PCG_NOBJECTS];
};

static void	pool_cache_reclaim(struct pool_cache *);

static int	pool_catchup(struct pool *);
static void	pool_prime_page(struct pool *, caddr_t,
		    struct pool_item_header *);

void		*pool_allocator_alloc(struct pool *, int);
void		pool_allocator_free(struct pool *, void *);

static void pool_print1(struct pool *, const char *,
	void (*)(const char *, ...));

/*
 * Pool log entry. An array of these is allocated in pool_init().
 */
struct pool_log {
	const char	*pl_file;
	long		pl_line;
	int		pl_action;
#define	PRLOG_GET	1
#define	PRLOG_PUT	2
	void		*pl_addr;
};

/* Number of entries in pool log buffers */
#ifndef POOL_LOGSIZE
#define	POOL_LOGSIZE	10
#endif

int pool_logsize = POOL_LOGSIZE;

#ifdef POOL_DIAGNOSTIC
static __inline void
pr_log(struct pool *pp, void *v, int action, const char *file, long line)
{
	int n = pp->pr_curlogentry;
	struct pool_log *pl;

	if ((pp->pr_roflags & PR_LOGGING) == 0)
		return;

	/*
	 * Fill in the current entry. Wrap around and overwrite
	 * the oldest entry if necessary.
	 */
	pl = &pp->pr_log[n];
	pl->pl_file = file;
	pl->pl_line = line;
	pl->pl_action = action;
	pl->pl_addr = v;
	if (++n >= pp->pr_logsize)
		n = 0;
	pp->pr_curlogentry = n;
}

static void
pr_printlog(struct pool *pp, struct pool_item *pi,
    void (*pr)(const char *, ...))
{
	int i = pp->pr_logsize;
	int n = pp->pr_curlogentry;

	if ((pp->pr_roflags & PR_LOGGING) == 0)
		return;

	/*
	 * Print all entries in this pool's log.
	 */
	while (i-- > 0) {
		struct pool_log *pl = &pp->pr_log[n];
		if (pl->pl_action != 0) {
			if (pi == NULL || pi == pl->pl_addr) {
				(*pr)("\tlog entry %d:\n", i);
				(*pr)("\t\taction = %s, addr = %p\n",
				    pl->pl_action == PRLOG_GET ? "get" : "put",
				    pl->pl_addr);
				(*pr)("\t\tfile: %s at line %lu\n",
				    pl->pl_file, pl->pl_line);
			}
		}
		if (++n >= pp->pr_logsize)
			n = 0;
	}
}

static __inline void
pr_enter(struct pool *pp, const char *file, long line)
{

	if (__predict_false(pp->pr_entered_file != NULL)) {
		printf("pool %s: reentrancy at file %s line %ld\n",
		    pp->pr_wchan, file, line);
		printf("         previous entry at file %s line %ld\n",
		    pp->pr_entered_file, pp->pr_entered_line);
		panic("pr_enter");
	}

	pp->pr_entered_file = file;
	pp->pr_entered_line = line;
}

static __inline void
pr_leave(struct pool *pp)
{

	if (__predict_false(pp->pr_entered_file == NULL)) {
		printf("pool %s not entered?\n", pp->pr_wchan);
		panic("pr_leave");
	}

	pp->pr_entered_file = NULL;
	pp->pr_entered_line = 0;
}

static __inline void
pr_enter_check(struct pool *pp, void (*pr)(const char *, ...))
{

	if (pp->pr_entered_file != NULL)
		(*pr)("\n\tcurrently entered from file %s line %ld\n",
		    pp->pr_entered_file, pp->pr_entered_line);
}
#else
#define	pr_log(pp, v, action, file, line)
#define	pr_printlog(pp, pi, pr)
#define	pr_enter(pp, file, line)
#define	pr_leave(pp)
#define	pr_enter_check(pp, pr)
#endif /* POOL_DIAGNOSTIC */

/*
 * Return the pool page header based on page address.
 */
static __inline struct pool_item_header *
pr_find_pagehead(struct pool *pp, caddr_t page)
{
	struct pool_item_header *ph;

	if ((pp->pr_roflags & PR_PHINPAGE) != 0)
		return ((struct pool_item_header *)(page + pp->pr_phoffset));

	for (ph = LIST_FIRST(&pp->pr_hashtab[PR_HASH_INDEX(pp, page)]);
	     ph != NULL;
	     ph = LIST_NEXT(ph, ph_hashlist)) {
		if (ph->ph_page == page)
			return (ph);
	}
	return (NULL);
}

/*
 * Remove a page from the pool.
 */
static __inline void
pr_rmpage(struct pool *pp, struct pool_item_header *ph,
     struct pool_pagelist *pq)
{
	int s;

	/*
	 * If the page was idle, decrement the idle page count.
	 */
	if (ph->ph_nmissing == 0) {
#ifdef DIAGNOSTIC
		if (pp->pr_nidle == 0)
			panic("pr_rmpage: nidle inconsistent");
		if (pp->pr_nitems < pp->pr_itemsperpage)
			panic("pr_rmpage: nitems inconsistent");
#endif
		pp->pr_nidle--;
	}

	pp->pr_nitems -= pp->pr_itemsperpage;

	/*
	 * Unlink a page from the pool and release it (or queue it for release).
	 */
	TAILQ_REMOVE(&pp->pr_pagelist, ph, ph_pagelist);
	if (pq) {
		TAILQ_INSERT_HEAD(pq, ph, ph_pagelist);
	} else {
		pool_allocator_free(pp, ph->ph_page);
		if ((pp->pr_roflags & PR_PHINPAGE) == 0) {
			LIST_REMOVE(ph, ph_hashlist);
			s = splhigh();
			pool_put(&phpool, ph);
			splx(s);
		}
	}
	pp->pr_npages--;
	pp->pr_npagefree++;

	if (pp->pr_curpage == ph) {
		/*
		 * Find a new non-empty page header, if any.
		 * Start search from the page head, to increase the
		 * chance for "high water" pages to be freed.
		 */
		TAILQ_FOREACH(ph, &pp->pr_pagelist, ph_pagelist)
			if (TAILQ_FIRST(&ph->ph_itemlist) != NULL)
				break;

		pp->pr_curpage = ph;
	}
}

/*
 * Initialize the given pool resource structure.
 *
 * We export this routine to allow other kernel parts to declare
 * static pools that must be initialized before malloc() is available.
 */
void
pool_init(struct pool *pp, size_t size, u_int align, u_int ioff, int flags,
    const char *wchan, struct pool_allocator *palloc)
{
	int off, slack, i;

#ifdef POOL_DIAGNOSTIC
	/*
	 * Always log if POOL_DIAGNOSTIC is defined.
	 */
	if (pool_logsize != 0)
		flags |= PR_LOGGING;
#endif

#ifdef POOL_SUBPAGE
	/*
	 * XXX We don't provide a real `nointr' back-end
	 * yet; all sub-pages come from a kmem back-end.
	 * maybe some day...
	 */
	if (palloc == NULL) {
		extern struct pool_allocator pool_allocator_kmem_subpage;
		palloc = &pool_allocator_kmem_subpage;
	}
	/*
	 * We'll assume any user-specified back-end allocator
	 * will deal with sub-pages, or simply don't care.
	 */
#else
	if (palloc == NULL)
		palloc = &pool_allocator_kmem;
#endif /* POOL_SUBPAGE */
	if ((palloc->pa_flags & PA_INITIALIZED) == 0) {
		if (palloc->pa_pagesz == 0) {
#ifdef POOL_SUBPAGE
			if (palloc == &pool_allocator_kmem)
				palloc->pa_pagesz = PAGE_SIZE;
			else
				palloc->pa_pagesz = POOL_SUBPAGE;
#else
			palloc->pa_pagesz = PAGE_SIZE;
#endif /* POOL_SUBPAGE */
		}

		TAILQ_INIT(&palloc->pa_list);

		simple_lock_init(&palloc->pa_slock);
		palloc->pa_pagemask = ~(palloc->pa_pagesz - 1);
		palloc->pa_pageshift = ffs(palloc->pa_pagesz) - 1;
		palloc->pa_flags |= PA_INITIALIZED;
	}

	if (align == 0)
		align = ALIGN(1);

	if (size < sizeof(struct pool_item))
		size = sizeof(struct pool_item);

	size = ALIGN(size);
#ifdef DIAGNOSTIC
	if (size > palloc->pa_pagesz)
		panic("pool_init: pool item size (%lu) too large",
		      (u_long)size);
#endif

	/*
	 * Initialize the pool structure.
	 */
	TAILQ_INIT(&pp->pr_pagelist);
	TAILQ_INIT(&pp->pr_cachelist);
	pp->pr_curpage = NULL;
	pp->pr_npages = 0;
	pp->pr_minitems = 0;
	pp->pr_minpages = 0;
	pp->pr_maxpages = UINT_MAX;
	pp->pr_roflags = flags;
	pp->pr_flags = 0;
	pp->pr_size = size;
	pp->pr_align = align;
	pp->pr_wchan = wchan;
	pp->pr_alloc = palloc;
	pp->pr_nitems = 0;
	pp->pr_nout = 0;
	pp->pr_hardlimit = UINT_MAX;
	pp->pr_hardlimit_warning = NULL;
	pp->pr_hardlimit_ratecap.tv_sec = 0;
	pp->pr_hardlimit_ratecap.tv_usec = 0;
	pp->pr_hardlimit_warning_last.tv_sec = 0;
	pp->pr_hardlimit_warning_last.tv_usec = 0;

	/*
	 * Decide whether to put the page header off page to avoid
	 * wasting too large a part of the page. Off-page page headers
	 * go on a hash table, so we can match a returned item
	 * with its header based on the page address.
	 * We use 1/16 of the page size as the threshold (XXX: tune)
	 */
	if (pp->pr_size < palloc->pa_pagesz/16) {
		/* Use the end of the page for the page header */
		pp->pr_roflags |= PR_PHINPAGE;
		pp->pr_phoffset = off = palloc->pa_pagesz -
		    ALIGN(sizeof(struct pool_item_header));
	} else {
		/* The page header will be taken from our page header pool */
		pp->pr_phoffset = 0;
		off = palloc->pa_pagesz;
		for (i = 0; i < PR_HASHTABSIZE; i++) {
			LIST_INIT(&pp->pr_hashtab[i]);
		}
	}

	/*
	 * Alignment is to take place at `ioff' within the item. This means
	 * we must reserve up to `align - 1' bytes on the page to allow
	 * appropriate positioning of each item.
	 *
	 * Silently enforce `0 <= ioff < align'.
	 */
	pp->pr_itemoffset = ioff = ioff % align;
	pp->pr_itemsperpage = (off - ((align - ioff) % align)) / pp->pr_size;
	KASSERT(pp->pr_itemsperpage != 0);

	/*
	 * Use the slack between the chunks and the page header
	 * for "cache coloring".
	 */
	slack = off - pp->pr_itemsperpage * pp->pr_size;
	pp->pr_maxcolor = (slack / align) * align;
	pp->pr_curcolor = 0;

	pp->pr_nget = 0;
	pp->pr_nfail = 0;
	pp->pr_nput = 0;
	pp->pr_npagealloc = 0;
	pp->pr_npagefree = 0;
	pp->pr_hiwat = 0;
	pp->pr_nidle = 0;

#ifdef POOL_DIAGNOSTIC
	if (flags & PR_LOGGING) {
		if (kmem_map == NULL ||
		    (pp->pr_log = malloc(pool_logsize * sizeof(struct pool_log),
		     M_TEMP, M_NOWAIT)) == NULL)
			pp->pr_roflags &= ~PR_LOGGING;
		pp->pr_curlogentry = 0;
		pp->pr_logsize = pool_logsize;
	}
#endif

	pp->pr_entered_file = NULL;
	pp->pr_entered_line = 0;

	simple_lock_init(&pp->pr_slock);

	/*
	 * Initialize private page header pool and cache magazine pool if we
	 * haven't done so yet.
	 * XXX LOCKING.
	 */
	if (phpool.pr_size == 0) {
#ifdef POOL_SUBPAGE
		pool_init(&phpool, sizeof(struct pool_item_header), 0, 0, 0,
		    "phpool", &pool_allocator_kmem);
		pool_init(&psppool, POOL_SUBPAGE, POOL_SUBPAGE, 0,
		    PR_RECURSIVE, "psppool", &pool_allocator_kmem);
#else
		pool_init(&phpool, sizeof(struct pool_item_header), 0, 0,
		    0, "phpool", NULL);
#endif
		pool_init(&pcgpool, sizeof(struct pool_cache_group), 0, 0,
		    0, "pcgpool", NULL);
	}

	/* Insert into the list of all pools. */
	simple_lock(&pool_head_slock);
	TAILQ_INSERT_TAIL(&pool_head, pp, pr_poollist);
	simple_unlock(&pool_head_slock);

	/* Insert this into the list of pools using this allocator. */
	simple_lock(&palloc->pa_slock);
	TAILQ_INSERT_TAIL(&palloc->pa_list, pp, pr_alloc_list);
	simple_unlock(&palloc->pa_slock);
}

/*
 * De-commision a pool resource.
 */
void
pool_destroy(struct pool *pp)
{
	struct pool_item_header *ph;
	struct pool_cache *pc;

	/* Locking order: pool_allocator -> pool */
	simple_lock(&pp->pr_alloc->pa_slock);
	TAILQ_REMOVE(&pp->pr_alloc->pa_list, pp, pr_alloc_list);
	simple_unlock(&pp->pr_alloc->pa_slock);

	/* Destroy all caches for this pool. */
	while ((pc = TAILQ_FIRST(&pp->pr_cachelist)) != NULL)
		pool_cache_destroy(pc);

#ifdef DIAGNOSTIC
	if (pp->pr_nout != 0) {
		pr_printlog(pp, NULL, printf);
		panic("pool_destroy: pool busy: still out: %u\n",
		    pp->pr_nout);
	}
#endif

	/* Remove all pages */
	if ((pp->pr_roflags & PR_STATIC) == 0)
		while ((ph = TAILQ_FIRST(&pp->pr_pagelist)) != NULL)
			pr_rmpage(pp, ph, NULL);

	/* Remove from global pool list */
	simple_lock(&pool_head_slock);
	TAILQ_REMOVE(&pool_head, pp, pr_poollist);
	if (drainpp == pp) {
		drainpp = NULL;
	}
	simple_unlock(&pool_head_slock);

#ifdef POOL_DIAGNOSTIC
	if ((pp->pr_roflags & PR_LOGGING) != 0)
		free(pp->pr_log, M_TEMP);
#endif

	if (pp->pr_roflags & PR_FREEHEADER)
		free(pp, M_POOL);
}

static __inline struct pool_item_header *
pool_alloc_item_header(struct pool *pp, caddr_t storage, int flags)
{
	struct pool_item_header *ph;
	int s;

	LOCK_ASSERT(simple_lock_held(&pp->pr_slock) == 0);

	if ((pp->pr_roflags & PR_PHINPAGE) != 0)
		ph = (struct pool_item_header *) (storage + pp->pr_phoffset);
	else {
		s = splhigh();
		ph = pool_get(&phpool, flags);
		splx(s);
	}

	return (ph);
}

/*
 * Grab an item from the pool; must be called at appropriate spl level
 */
void *
#ifdef POOL_DIAGNOSTIC
_pool_get(struct pool *pp, int flags, const char *file, long line)
#else
pool_get(struct pool *pp, int flags)
#endif
{
	struct pool_item *pi;
	struct pool_item_header *ph;
	void *v;

#ifdef DIAGNOSTIC
	if (__predict_false((pp->pr_roflags & PR_STATIC) &&
			    (flags & PR_MALLOCOK))) {
		pr_printlog(pp, NULL, printf);
		panic("pool_get: static");
	}

	if (__predict_false(curproc == NULL && doing_shutdown == 0 &&
			    (flags & PR_WAITOK) != 0))
		panic("pool_get: must have NOWAIT");

#ifdef LOCKDEBUG
	if (flags & PR_WAITOK)
		simple_lock_only_held(NULL, "pool_get(PR_WAITOK)");
#endif
#endif /* DIAGNOSTIC */

	simple_lock(&pp->pr_slock);
	pr_enter(pp, file, line);

 startover:
	/*
	 * Check to see if we've reached the hard limit.  If we have,
	 * and we can wait, then wait until an item has been returned to
	 * the pool.
	 */
#ifdef DIAGNOSTIC
	if (__predict_false(pp->pr_nout > pp->pr_hardlimit)) {
		pr_leave(pp);
		simple_unlock(&pp->pr_slock);
		panic("pool_get: %s: crossed hard limit", pp->pr_wchan);
	}
#endif
	if (__predict_false(pp->pr_nout == pp->pr_hardlimit)) {
		if ((flags & PR_WAITOK) && !(flags & PR_LIMITFAIL)) {
			/*
			 * XXX: A warning isn't logged in this case.  Should
			 * it be?
			 */
			pp->pr_flags |= PR_WANTED;
			pr_leave(pp);
			ltsleep(pp, PSWP, pp->pr_wchan, 0, &pp->pr_slock);
			pr_enter(pp, file, line);
			goto startover;
		}

		/*
		 * Log a message that the hard limit has been hit.
		 */
		if (pp->pr_hardlimit_warning != NULL &&
		    ratecheck(&pp->pr_hardlimit_warning_last,
			      &pp->pr_hardlimit_ratecap))
			log(LOG_ERR, "%s\n", pp->pr_hardlimit_warning);

		pp->pr_nfail++;

		pr_leave(pp);
		simple_unlock(&pp->pr_slock);
		return (NULL);
	}

	/*
	 * The convention we use is that if `curpage' is not NULL, then
	 * it points at a non-empty bucket. In particular, `curpage'
	 * never points at a page header which has PR_PHINPAGE set and
	 * has no items in its bucket.
	 */
	if ((ph = pp->pr_curpage) == NULL) {
#ifdef DIAGNOSTIC
		if (pp->pr_nitems != 0) {
			simple_unlock(&pp->pr_slock);
			printf("pool_get: %s: curpage NULL, nitems %u\n",
			    pp->pr_wchan, pp->pr_nitems);
			panic("pool_get: nitems inconsistent\n");
		}
#endif

		/*
		 * Call the back-end page allocator for more memory.
		 * Release the pool lock, as the back-end page allocator
		 * may block.
		 */
		pr_leave(pp);
		simple_unlock(&pp->pr_slock);
		v = pool_allocator_alloc(pp, flags);
		if (__predict_true(v != NULL))
			ph = pool_alloc_item_header(pp, v, flags);
		simple_lock(&pp->pr_slock);
		pr_enter(pp, file, line);

		if (__predict_false(v == NULL || ph == NULL)) {
			if (v != NULL)
				pool_allocator_free(pp, v);

			/*
			 * We were unable to allocate a page or item
			 * header, but we released the lock during
			 * allocation, so perhaps items were freed
			 * back to the pool.  Check for this case.
			 */
			if (pp->pr_curpage != NULL)
				goto startover;

			if ((flags & PR_WAITOK) == 0) {
				pp->pr_nfail++;
				pr_leave(pp);
				simple_unlock(&pp->pr_slock);
				return (NULL);
			}

			/*
			 * Wait for items to be returned to this pool.
			 *
			 * XXX: maybe we should wake up once a second and
			 * try again?
			 */
			pp->pr_flags |= PR_WANTED;
			/* PA_WANTED is already set on the allocator. */
			pr_leave(pp);
			ltsleep(pp, PSWP, pp->pr_wchan, 0, &pp->pr_slock);
			pr_enter(pp, file, line);
			goto startover;
		}

		/* We have more memory; add it to the pool */
		pool_prime_page(pp, v, ph);
		pp->pr_npagealloc++;

		/* Start the allocation process over. */
		goto startover;
	}

	if (__predict_false((v = pi = TAILQ_FIRST(&ph->ph_itemlist)) == NULL)) {
		pr_leave(pp);
		simple_unlock(&pp->pr_slock);
		panic("pool_get: %s: page empty", pp->pr_wchan);
	}
#ifdef DIAGNOSTIC
	if (__predict_false(pp->pr_nitems == 0)) {
		pr_leave(pp);
		simple_unlock(&pp->pr_slock);
		printf("pool_get: %s: items on itemlist, nitems %u\n",
		    pp->pr_wchan, pp->pr_nitems);
		panic("pool_get: nitems inconsistent\n");
	}
#endif

#ifdef POOL_DIAGNOSTIC
	pr_log(pp, v, PRLOG_GET, file, line);
#endif

#ifdef DIAGNOSTIC
	if (__predict_false(pi->pi_magic != PI_MAGIC)) {
		pr_printlog(pp, pi, printf);
		panic("pool_get(%s): free list modified: magic=%x; page %p;"
		       " item addr %p\n",
			pp->pr_wchan, pi->pi_magic, ph->ph_page, pi);
	}
#endif

	/*
	 * Remove from item list.
	 */
	TAILQ_REMOVE(&ph->ph_itemlist, pi, pi_list);
	pp->pr_nitems--;
	pp->pr_nout++;
	if (ph->ph_nmissing == 0) {
#ifdef DIAGNOSTIC
		if (__predict_false(pp->pr_nidle == 0))
			panic("pool_get: nidle inconsistent");
#endif
		pp->pr_nidle--;
	}
	ph->ph_nmissing++;
	if (TAILQ_FIRST(&ph->ph_itemlist) == NULL) {
#ifdef DIAGNOSTIC
		if (__predict_false(ph->ph_nmissing != pp->pr_itemsperpage)) {
			pr_leave(pp);
			simple_unlock(&pp->pr_slock);
			panic("pool_get: %s: nmissing inconsistent",
			    pp->pr_wchan);
		}
#endif
		/*
		 * Find a new non-empty page header, if any.
		 * Start search from the page head, to increase
		 * the chance for "high water" pages to be freed.
		 *
		 * Migrate empty pages to the end of the list.  This
		 * will speed the update of curpage as pages become
		 * idle.  Empty pages intermingled with idle pages
		 * is no big deal.  As soon as a page becomes un-empty,
		 * it will move back to the head of the list.
		 */
		TAILQ_REMOVE(&pp->pr_pagelist, ph, ph_pagelist);
		TAILQ_INSERT_TAIL(&pp->pr_pagelist, ph, ph_pagelist);
		TAILQ_FOREACH(ph, &pp->pr_pagelist, ph_pagelist)
			if (TAILQ_FIRST(&ph->ph_itemlist) != NULL)
				break;

		pp->pr_curpage = ph;
	}

	pp->pr_nget++;

	/*
	 * If we have a low water mark and we are now below that low
	 * water mark, add more items to the pool.
	 */
	if (POOL_NEEDS_CATCHUP(pp) && pool_catchup(pp) != 0) {
		/*
		 * XXX: Should we log a warning?  Should we set up a timeout
		 * to try again in a second or so?  The latter could break
		 * a caller's assumptions about interrupt protection, etc.
		 */
	}

	pr_leave(pp);
	simple_unlock(&pp->pr_slock);
	return (v);
}

/*
 * Internal version of pool_put().  Pool is already locked/entered.
 */
static void
pool_do_put(struct pool *pp, void *v)
{
	struct pool_item *pi = v;
	struct pool_item_header *ph;
	caddr_t page;
	int s;

	LOCK_ASSERT(simple_lock_held(&pp->pr_slock));

	page = (caddr_t)((u_long)v & pp->pr_alloc->pa_pagemask);

#ifdef DIAGNOSTIC
	if (__predict_false(pp->pr_nout == 0)) {
		printf("pool %s: putting with none out\n",
		    pp->pr_wchan);
		panic("pool_put");
	}
#endif

	if (__predict_false((ph = pr_find_pagehead(pp, page)) == NULL)) {
		pr_printlog(pp, NULL, printf);
		panic("pool_put: %s: page header missing", pp->pr_wchan);
	}

#ifdef LOCKDEBUG
	/*
	 * Check if we're freeing a locked simple lock.
	 */
	simple_lock_freecheck((caddr_t)pi, ((caddr_t)pi) + pp->pr_size);
#endif

	/*
	 * Return to item list.
	 */
#ifdef DIAGNOSTIC
	pi->pi_magic = PI_MAGIC;
#endif
#ifdef DEBUG
	{
		int i, *ip = v;

		for (i = 0; i < pp->pr_size / sizeof(int); i++) {
			*ip++ = PI_MAGIC;
		}
	}
#endif

	TAILQ_INSERT_HEAD(&ph->ph_itemlist, pi, pi_list);
	ph->ph_nmissing--;
	pp->pr_nput++;
	pp->pr_nitems++;
	pp->pr_nout--;

	/* Cancel "pool empty" condition if it exists */
	if (pp->pr_curpage == NULL)
		pp->pr_curpage = ph;

	if (pp->pr_flags & PR_WANTED) {
		pp->pr_flags &= ~PR_WANTED;
		if (ph->ph_nmissing == 0)
			pp->pr_nidle++;
		wakeup((caddr_t)pp);
		return;
	}

	/*
	 * If this page is now complete, do one of two things:
	 *
	 *	(1) If we have more pages than the page high water
	 *	    mark, free the page back to the system.
	 *
	 *	(2) Move it to the end of the page list, so that
	 *	    we minimize our chances of fragmenting the
	 *	    pool.  Idle pages migrate to the end (along with
	 *	    completely empty pages, so that we find un-empty
	 *	    pages more quickly when we update curpage) of the
	 *	    list so they can be more easily swept up by
	 *	    the pagedaemon when pages are scarce.
	 */
	if (ph->ph_nmissing == 0) {
		pp->pr_nidle++;
		if (pp->pr_npages > pp->pr_maxpages) {
			pr_rmpage(pp, ph, NULL);
		} else {
			TAILQ_REMOVE(&pp->pr_pagelist, ph, ph_pagelist);
			TAILQ_INSERT_TAIL(&pp->pr_pagelist, ph, ph_pagelist);

			/*
			 * Update the timestamp on the page.  A page must
			 * be idle for some period of time before it can
			 * be reclaimed by the pagedaemon.  This minimizes
			 * ping-pong'ing for memory.
			 */
			s = splclock();
			ph->ph_time = mono_time;
			splx(s);

			/*
			 * Update the current page pointer.  Just look for
			 * the first page with any free items.
			 *
			 * XXX: Maybe we want an option to look for the
			 * page with the fewest available items, to minimize
			 * fragmentation?
			 */
			TAILQ_FOREACH(ph, &pp->pr_pagelist, ph_pagelist)
				if (TAILQ_FIRST(&ph->ph_itemlist) != NULL)
					break;

			pp->pr_curpage = ph;
		}
	}
	/*
	 * If the page has just become un-empty, move it to the head of
	 * the list, and make it the current page.  The next allocation
	 * will get the item from this page, instead of further fragmenting
	 * the pool.
	 */
	else if (ph->ph_nmissing == (pp->pr_itemsperpage - 1)) {
		TAILQ_REMOVE(&pp->pr_pagelist, ph, ph_pagelist);
		TAILQ_INSERT_HEAD(&pp->pr_pagelist, ph, ph_pagelist);
		pp->pr_curpage = ph;
	}
}

/*
 * Return resource to the pool; must be called at appropriate spl level
 */
#ifdef POOL_DIAGNOSTIC
void
_pool_put(struct pool *pp, void *v, const char *file, long line)
{

	simple_lock(&pp->pr_slock);
	pr_enter(pp, file, line);

	pr_log(pp, v, PRLOG_PUT, file, line);

	pool_do_put(pp, v);

	pr_leave(pp);
	simple_unlock(&pp->pr_slock);
}
#undef pool_put
#endif /* POOL_DIAGNOSTIC */

void
pool_put(struct pool *pp, void *v)
{

	simple_lock(&pp->pr_slock);

	pool_do_put(pp, v);

	simple_unlock(&pp->pr_slock);
}

#ifdef POOL_DIAGNOSTIC
#define		pool_put(h, v)	_pool_put((h), (v), __FILE__, __LINE__)
#endif

/*
 * Add N items to the pool.
 */
int
pool_prime(struct pool *pp, int n)
{
	struct pool_item_header *ph;
	caddr_t cp;
	int newpages, error = 0;

	simple_lock(&pp->pr_slock);

	newpages = roundup(n, pp->pr_itemsperpage) / pp->pr_itemsperpage;

	while (newpages-- > 0) {
		simple_unlock(&pp->pr_slock);
		cp = pool_allocator_alloc(pp, PR_NOWAIT);
		if (__predict_true(cp != NULL))
			ph = pool_alloc_item_header(pp, cp, PR_NOWAIT);
		simple_lock(&pp->pr_slock);

		if (__predict_false(cp == NULL || ph == NULL)) {
			error = ENOMEM;
			if (cp != NULL)
				pool_allocator_free(pp, cp);
			break;
		}

		pool_prime_page(pp, cp, ph);
		pp->pr_npagealloc++;
		pp->pr_minpages++;
	}

	if (pp->pr_minpages >= pp->pr_maxpages)
		pp->pr_maxpages = pp->pr_minpages + 1;	/* XXX */

	simple_unlock(&pp->pr_slock);
	return (0);
}

/*
 * Add a page worth of items to the pool.
 *
 * Note, we must be called with the pool descriptor LOCKED.
 */
static void
pool_prime_page(struct pool *pp, caddr_t storage, struct pool_item_header *ph)
{
	struct pool_item *pi;
	caddr_t cp = storage;
	unsigned int align = pp->pr_align;
	unsigned int ioff = pp->pr_itemoffset;
	int n;

#ifdef DIAGNOSTIC
	if (((u_long)cp & (pp->pr_alloc->pa_pagesz - 1)) != 0)
		panic("pool_prime_page: %s: unaligned page", pp->pr_wchan);
#endif

	if ((pp->pr_roflags & PR_PHINPAGE) == 0)
		LIST_INSERT_HEAD(&pp->pr_hashtab[PR_HASH_INDEX(pp, cp)],
		    ph, ph_hashlist);

	/*
	 * Insert page header.
	 */
	TAILQ_INSERT_HEAD(&pp->pr_pagelist, ph, ph_pagelist);
	TAILQ_INIT(&ph->ph_itemlist);
	ph->ph_page = storage;
	ph->ph_nmissing = 0;
	memset(&ph->ph_time, 0, sizeof(ph->ph_time));

	pp->pr_nidle++;

	/*
	 * Color this page.
	 */
	cp = (caddr_t)(cp + pp->pr_curcolor);
	if ((pp->pr_curcolor += align) > pp->pr_maxcolor)
		pp->pr_curcolor = 0;

	/*
	 * Adjust storage to apply aligment to `pr_itemoffset' in each item.
	 */
	if (ioff != 0)
		cp = (caddr_t)(cp + (align - ioff));

	/*
	 * Insert remaining chunks on the bucket list.
	 */
	n = pp->pr_itemsperpage;
	pp->pr_nitems += n;

	while (n--) {
		pi = (struct pool_item *)cp;

		/* Insert on page list */
		TAILQ_INSERT_TAIL(&ph->ph_itemlist, pi, pi_list);
#ifdef DIAGNOSTIC
		pi->pi_magic = PI_MAGIC;
#endif
		cp = (caddr_t)(cp + pp->pr_size);
	}

	/*
	 * If the pool was depleted, point at the new page.
	 */
	if (pp->pr_curpage == NULL)
		pp->pr_curpage = ph;

	if (++pp->pr_npages > pp->pr_hiwat)
		pp->pr_hiwat = pp->pr_npages;
}

/*
 * Used by pool_get() when nitems drops below the low water mark.  This
 * is used to catch up nitmes with the low water mark.
 *
 * Note 1, we never wait for memory here, we let the caller decide what to do.
 *
 * Note 2, this doesn't work with static pools.
 *
 * Note 3, we must be called with the pool already locked, and we return
 * with it locked.
 */
static int
pool_catchup(struct pool *pp)
{
	struct pool_item_header *ph;
	caddr_t cp;
	int error = 0;

	if (pp->pr_roflags & PR_STATIC) {
		/*
		 * We dropped below the low water mark, and this is not a
		 * good thing.  Log a warning.
		 *
		 * XXX: rate-limit this?
		 */
		printf("WARNING: static pool `%s' dropped below low water "
		    "mark\n", pp->pr_wchan);
		return (0);
	}

	while (POOL_NEEDS_CATCHUP(pp)) {
		/*
		 * Call the page back-end allocator for more memory.
		 *
		 * XXX: We never wait, so should we bother unlocking
		 * the pool descriptor?
		 */
		simple_unlock(&pp->pr_slock);
		cp = pool_allocator_alloc(pp, PR_NOWAIT);
		if (__predict_true(cp != NULL))
			ph = pool_alloc_item_header(pp, cp, PR_NOWAIT);
		simple_lock(&pp->pr_slock);
		if (__predict_false(cp == NULL || ph == NULL)) {
			if (cp != NULL)
				pool_allocator_free(pp, cp);
			error = ENOMEM;
			break;
		}
		pool_prime_page(pp, cp, ph);
		pp->pr_npagealloc++;
	}

	return (error);
}

void
pool_setlowat(struct pool *pp, int n)
{
	int error;

	simple_lock(&pp->pr_slock);

	pp->pr_minitems = n;
	pp->pr_minpages = (n == 0)
		? 0
		: roundup(n, pp->pr_itemsperpage) / pp->pr_itemsperpage;

	/* Make sure we're caught up with the newly-set low water mark. */
	if (POOL_NEEDS_CATCHUP(pp) && (error = pool_catchup(pp) != 0)) {
		/*
		 * XXX: Should we log a warning?  Should we set up a timeout
		 * to try again in a second or so?  The latter could break
		 * a caller's assumptions about interrupt protection, etc.
		 */
	}

	simple_unlock(&pp->pr_slock);
}

void
pool_sethiwat(struct pool *pp, int n)
{

	simple_lock(&pp->pr_slock);

	pp->pr_maxpages = (n == 0)
		? 0
		: roundup(n, pp->pr_itemsperpage) / pp->pr_itemsperpage;

	simple_unlock(&pp->pr_slock);
}

void
pool_sethardlimit(struct pool *pp, int n, const char *warnmess, int ratecap)
{

	simple_lock(&pp->pr_slock);

	pp->pr_hardlimit = n;
	pp->pr_hardlimit_warning = warnmess;
	pp->pr_hardlimit_ratecap.tv_sec = ratecap;
	pp->pr_hardlimit_warning_last.tv_sec = 0;
	pp->pr_hardlimit_warning_last.tv_usec = 0;

	/*
	 * In-line version of pool_sethiwat(), because we don't want to
	 * release the lock.
	 */
	pp->pr_maxpages = (n == 0)
		? 0
		: roundup(n, pp->pr_itemsperpage) / pp->pr_itemsperpage;

	simple_unlock(&pp->pr_slock);
}

/*
 * Release all complete pages that have not been used recently.
 */
int
#ifdef POOL_DIAGNOSTIC
_pool_reclaim(struct pool *pp, const char *file, long line)
#else
pool_reclaim(struct pool *pp)
#endif
{
	struct pool_item_header *ph, *phnext;
	struct pool_cache *pc;
	struct timeval curtime;
	struct pool_pagelist pq;
	int s;

	if (pp->pr_roflags & PR_STATIC)
		return (0);

	if (simple_lock_try(&pp->pr_slock) == 0)
		return (0);
	pr_enter(pp, file, line);
	TAILQ_INIT(&pq);

	/*
	 * Reclaim items from the pool's caches.
	 */
	TAILQ_FOREACH(pc, &pp->pr_cachelist, pc_poollist)
		pool_cache_reclaim(pc);

	s = splclock();
	curtime = mono_time;
	splx(s);

	for (ph = TAILQ_FIRST(&pp->pr_pagelist); ph != NULL; ph = phnext) {
		phnext = TAILQ_NEXT(ph, ph_pagelist);

		/* Check our minimum page claim */
		if (pp->pr_npages <= pp->pr_minpages)
			break;

		if (ph->ph_nmissing == 0) {
			struct timeval diff;
			timersub(&curtime, &ph->ph_time, &diff);
			if (diff.tv_sec < pool_inactive_time)
				continue;

			/*
			 * If freeing this page would put us below
			 * the low water mark, stop now.
			 */
			if ((pp->pr_nitems - pp->pr_itemsperpage) <
			    pp->pr_minitems)
				break;

			pr_rmpage(pp, ph, &pq);
		}
	}

	pr_leave(pp);
	simple_unlock(&pp->pr_slock);
	if (TAILQ_EMPTY(&pq))
		return (0);

	while ((ph = TAILQ_FIRST(&pq)) != NULL) {
		TAILQ_REMOVE(&pq, ph, ph_pagelist);
		pool_allocator_free(pp, ph->ph_page);
		if (pp->pr_roflags & PR_PHINPAGE) {
			continue;
		}
		LIST_REMOVE(ph, ph_hashlist);
		s = splhigh();
		pool_put(&phpool, ph);
		splx(s);
	}

	return (1);
}

/*
 * Drain pools, one at a time.
 *
 * Note, we must never be called from an interrupt context.
 */
void
pool_drain(void *arg)
{
	struct pool *pp;
	int s;

	pp = NULL;
	s = splvm();
	simple_lock(&pool_head_slock);
	if (drainpp == NULL) {
		drainpp = TAILQ_FIRST(&pool_head);
	}
	if (drainpp) {
		pp = drainpp;
		drainpp = TAILQ_NEXT(pp, pr_poollist);
	}
	simple_unlock(&pool_head_slock);
	pool_reclaim(pp);
	splx(s);
}

/*
 * Diagnostic helpers.
 */
void
pool_print(struct pool *pp, const char *modif)
{
	int s;

	s = splvm();
	if (simple_lock_try(&pp->pr_slock) == 0) {
		printf("pool %s is locked; try again later\n",
		    pp->pr_wchan);
		splx(s);
		return;
	}
	pool_print1(pp, modif, printf);
	simple_unlock(&pp->pr_slock);
	splx(s);
}

void
pool_printit(struct pool *pp, const char *modif, void (*pr)(const char *, ...))
{
	int didlock = 0;

	if (pp == NULL) {
		(*pr)("Must specify a pool to print.\n");
		return;
	}

	/*
	 * Called from DDB; interrupts should be blocked, and all
	 * other processors should be paused.  We can skip locking
	 * the pool in this case.
	 *
	 * We do a simple_lock_try() just to print the lock
	 * status, however.
	 */

	if (simple_lock_try(&pp->pr_slock) == 0)
		(*pr)("WARNING: pool %s is locked\n", pp->pr_wchan);
	else
		didlock = 1;

	pool_print1(pp, modif, pr);

	if (didlock)
		simple_unlock(&pp->pr_slock);
}

static void
pool_print1(struct pool *pp, const char *modif, void (*pr)(const char *, ...))
{
	struct pool_item_header *ph;
	struct pool_cache *pc;
	struct pool_cache_group *pcg;
#ifdef DIAGNOSTIC
	struct pool_item *pi;
#endif
	int i, print_log = 0, print_pagelist = 0, print_cache = 0;
	char c;

	while ((c = *modif++) != '\0') {
		if (c == 'l')
			print_log = 1;
		if (c == 'p')
			print_pagelist = 1;
		if (c == 'c')
			print_cache = 1;
		modif++;
	}

	(*pr)("POOL %s: size %u, align %u, ioff %u, roflags 0x%08x\n",
	    pp->pr_wchan, pp->pr_size, pp->pr_align, pp->pr_itemoffset,
	    pp->pr_roflags);
	(*pr)("\talloc %p\n", pp->pr_alloc);
	(*pr)("\tminitems %u, minpages %u, maxpages %u, npages %u\n",
	    pp->pr_minitems, pp->pr_minpages, pp->pr_maxpages, pp->pr_npages);
	(*pr)("\titemsperpage %u, nitems %u, nout %u, hardlimit %u\n",
	    pp->pr_itemsperpage, pp->pr_nitems, pp->pr_nout, pp->pr_hardlimit);

	(*pr)("\n\tnget %lu, nfail %lu, nput %lu\n",
	    pp->pr_nget, pp->pr_nfail, pp->pr_nput);
	(*pr)("\tnpagealloc %lu, npagefree %lu, hiwat %u, nidle %lu\n",
	    pp->pr_npagealloc, pp->pr_npagefree, pp->pr_hiwat, pp->pr_nidle);

	if (print_pagelist == 0)
		goto skip_pagelist;

	if ((ph = TAILQ_FIRST(&pp->pr_pagelist)) != NULL)
		(*pr)("\n\tpage list:\n");
	for (; ph != NULL; ph = TAILQ_NEXT(ph, ph_pagelist)) {
		(*pr)("\t\tpage %p, nmissing %d, time %lu,%lu\n",
		    ph->ph_page, ph->ph_nmissing,
		    (u_long)ph->ph_time.tv_sec,
		    (u_long)ph->ph_time.tv_usec);
#ifdef DIAGNOSTIC
		TAILQ_FOREACH(pi, &ph->ph_itemlist, pi_list) {
			if (pi->pi_magic != PI_MAGIC) {
				(*pr)("\t\t\titem %p, magic 0x%x\n",
				    pi, pi->pi_magic);
			}
		}
#endif
	}
	if (pp->pr_curpage == NULL)
		(*pr)("\tno current page\n");
	else
		(*pr)("\tcurpage %p\n", pp->pr_curpage->ph_page);

 skip_pagelist:

	if (print_log == 0)
		goto skip_log;

	(*pr)("\n");
	if ((pp->pr_roflags & PR_LOGGING) == 0)
		(*pr)("\tno log\n");
	else
		pr_printlog(pp, NULL, pr);

 skip_log:

	if (print_cache == 0)
		goto skip_cache;

	TAILQ_FOREACH(pc, &pp->pr_cachelist, pc_poollist) {
		(*pr)("\tcache %p: allocfrom %p freeto %p\n", pc,
		    pc->pc_allocfrom, pc->pc_freeto);
		(*pr)("\t    hits %lu misses %lu ngroups %lu nitems %lu\n",
		    pc->pc_hits, pc->pc_misses, pc->pc_ngroups, pc->pc_nitems);
		TAILQ_FOREACH(pcg, &pc->pc_grouplist, pcg_list) {
			(*pr)("\t\tgroup %p: avail %d\n", pcg, pcg->pcg_avail);
			for (i = 0; i < PCG_NOBJECTS; i++)
				(*pr)("\t\t\t%p\n", pcg->pcg_objects[i]);
		}
	}

 skip_cache:

	pr_enter_check(pp, pr);
}

int
pool_chk(struct pool *pp, const char *label)
{
	struct pool_item_header *ph;
	int r = 0;

	simple_lock(&pp->pr_slock);

	TAILQ_FOREACH(ph, &pp->pr_pagelist, ph_pagelist) {
		struct pool_item *pi;
		int n;
		caddr_t page;

		page = (caddr_t)((u_long)ph & pp->pr_alloc->pa_pagemask);
		if (page != ph->ph_page &&
		    (pp->pr_roflags & PR_PHINPAGE) != 0) {
			if (label != NULL)
				printf("%s: ", label);
			printf("pool(%p:%s): page inconsistency: page %p;"
			       " at page head addr %p (p %p)\n", pp,
				pp->pr_wchan, ph->ph_page,
				ph, page);
			r++;
			goto out;
		}

		for (pi = TAILQ_FIRST(&ph->ph_itemlist), n = 0;
		     pi != NULL;
		     pi = TAILQ_NEXT(pi,pi_list), n++) {

#ifdef DIAGNOSTIC
			if (pi->pi_magic != PI_MAGIC) {
				if (label != NULL)
					printf("%s: ", label);
				printf("pool(%s): free list modified: magic=%x;"
				       " page %p; item ordinal %d;"
				       " addr %p (p %p)\n",
					pp->pr_wchan, pi->pi_magic, ph->ph_page,
					n, pi, page);
				panic("pool");
			}
#endif
			page =
			    (caddr_t)((u_long)pi & pp->pr_alloc->pa_pagemask);
			if (page == ph->ph_page)
				continue;

			if (label != NULL)
				printf("%s: ", label);
			printf("pool(%p:%s): page inconsistency: page %p;"
			       " item ordinal %d; addr %p (p %p)\n", pp,
				pp->pr_wchan, ph->ph_page,
				n, pi, page);
			r++;
			goto out;
		}
	}
out:
	simple_unlock(&pp->pr_slock);
	return (r);
}

/*
 * pool_cache_init:
 *
 *	Initialize a pool cache.
 *
 *	NOTE: If the pool must be protected from interrupts, we expect
 *	to be called at the appropriate interrupt priority level.
 */
void
pool_cache_init(struct pool_cache *pc, struct pool *pp,
    int (*ctor)(void *, void *, int),
    void (*dtor)(void *, void *),
    void *arg)
{

	TAILQ_INIT(&pc->pc_grouplist);
	simple_lock_init(&pc->pc_slock);

	pc->pc_allocfrom = NULL;
	pc->pc_freeto = NULL;
	pc->pc_pool = pp;

	pc->pc_ctor = ctor;
	pc->pc_dtor = dtor;
	pc->pc_arg  = arg;

	pc->pc_hits   = 0;
	pc->pc_misses = 0;

	pc->pc_ngroups = 0;

	pc->pc_nitems = 0;

	simple_lock(&pp->pr_slock);
	TAILQ_INSERT_TAIL(&pp->pr_cachelist, pc, pc_poollist);
	simple_unlock(&pp->pr_slock);
}

/*
 * pool_cache_destroy:
 *
 *	Destroy a pool cache.
 */
void
pool_cache_destroy(struct pool_cache *pc)
{
	struct pool *pp = pc->pc_pool;

	/* First, invalidate the entire cache. */
	pool_cache_invalidate(pc);

	/* ...and remove it from the pool's cache list. */
	simple_lock(&pp->pr_slock);
	TAILQ_REMOVE(&pp->pr_cachelist, pc, pc_poollist);
	simple_unlock(&pp->pr_slock);
}

static __inline void *
pcg_get(struct pool_cache_group *pcg)
{
	void *object;
	u_int idx;

	KASSERT(pcg->pcg_avail <= PCG_NOBJECTS);
	KASSERT(pcg->pcg_avail != 0);
	idx = --pcg->pcg_avail;

	KASSERT(pcg->pcg_objects[idx] != NULL);
	object = pcg->pcg_objects[idx];
	pcg->pcg_objects[idx] = NULL;

	return (object);
}

static __inline void
pcg_put(struct pool_cache_group *pcg, void *object)
{
	u_int idx;

	KASSERT(pcg->pcg_avail < PCG_NOBJECTS);
	idx = pcg->pcg_avail++;

	KASSERT(pcg->pcg_objects[idx] == NULL);
	pcg->pcg_objects[idx] = object;
}

/*
 * pool_cache_get:
 *
 *	Get an object from a pool cache.
 */
void *
pool_cache_get(struct pool_cache *pc, int flags)
{
	struct pool_cache_group *pcg;
	void *object;

#ifdef LOCKDEBUG
	if (flags & PR_WAITOK)
		simple_lock_only_held(NULL, "pool_cache_get(PR_WAITOK)");
#endif

	simple_lock(&pc->pc_slock);

	if ((pcg = pc->pc_allocfrom) == NULL) {
		TAILQ_FOREACH(pcg, &pc->pc_grouplist, pcg_list) {
			if (pcg->pcg_avail != 0) {
				pc->pc_allocfrom = pcg;
				goto have_group;
			}
		}

		/*
		 * No groups with any available objects.  Allocate
		 * a new object, construct it, and return it to
		 * the caller.  We will allocate a group, if necessary,
		 * when the object is freed back to the cache.
		 */
		pc->pc_misses++;
		simple_unlock(&pc->pc_slock);
		object = pool_get(pc->pc_pool, flags);
		if (object != NULL && pc->pc_ctor != NULL) {
			if ((*pc->pc_ctor)(pc->pc_arg, object, flags) != 0) {
				pool_put(pc->pc_pool, object);
				return (NULL);
			}
		}
		return (object);
	}

 have_group:
	pc->pc_hits++;
	pc->pc_nitems--;
	object = pcg_get(pcg);

	if (pcg->pcg_avail == 0)
		pc->pc_allocfrom = NULL;

	simple_unlock(&pc->pc_slock);

	return (object);
}

/*
 * pool_cache_put:
 *
 *	Put an object back to the pool cache.
 */
void
pool_cache_put(struct pool_cache *pc, void *object)
{
	struct pool_cache_group *pcg;
	int s;

	simple_lock(&pc->pc_slock);

	if ((pcg = pc->pc_freeto) == NULL) {
		TAILQ_FOREACH(pcg, &pc->pc_grouplist, pcg_list) {
			if (pcg->pcg_avail != PCG_NOBJECTS) {
				pc->pc_freeto = pcg;
				goto have_group;
			}
		}

		/*
		 * No empty groups to free the object to.  Attempt to
		 * allocate one.
		 */
		simple_unlock(&pc->pc_slock);
		s = splvm();
		pcg = pool_get(&pcgpool, PR_NOWAIT);
		splx(s);
		if (pcg != NULL) {
			memset(pcg, 0, sizeof(*pcg));
			simple_lock(&pc->pc_slock);
			pc->pc_ngroups++;
			TAILQ_INSERT_TAIL(&pc->pc_grouplist, pcg, pcg_list);
			if (pc->pc_freeto == NULL)
				pc->pc_freeto = pcg;
			goto have_group;
		}

		/*
		 * Unable to allocate a cache group; destruct the object
		 * and free it back to the pool.
		 */
		pool_cache_destruct_object(pc, object);
		return;
	}

 have_group:
	pc->pc_nitems++;
	pcg_put(pcg, object);

	if (pcg->pcg_avail == PCG_NOBJECTS)
		pc->pc_freeto = NULL;

	simple_unlock(&pc->pc_slock);
}

/*
 * pool_cache_destruct_object:
 *
 *	Force destruction of an object and its release back into
 *	the pool.
 */
void
pool_cache_destruct_object(struct pool_cache *pc, void *object)
{

	if (pc->pc_dtor != NULL)
		(*pc->pc_dtor)(pc->pc_arg, object);
	pool_put(pc->pc_pool, object);
}

/*
 * pool_cache_do_invalidate:
 *
 *	This internal function implements pool_cache_invalidate() and
 *	pool_cache_reclaim().
 */
static void
pool_cache_do_invalidate(struct pool_cache *pc, int free_groups,
    void (*putit)(struct pool *, void *))
{
	struct pool_cache_group *pcg, *npcg;
	void *object;
	int s;

	for (pcg = TAILQ_FIRST(&pc->pc_grouplist); pcg != NULL;
	     pcg = npcg) {
		npcg = TAILQ_NEXT(pcg, pcg_list);
		while (pcg->pcg_avail != 0) {
			pc->pc_nitems--;
			object = pcg_get(pcg);
			if (pcg->pcg_avail == 0 && pc->pc_allocfrom == pcg)
				pc->pc_allocfrom = NULL;
			if (pc->pc_dtor != NULL)
				(*pc->pc_dtor)(pc->pc_arg, object);
			(*putit)(pc->pc_pool, object);
		}
		if (free_groups) {
			pc->pc_ngroups--;
			TAILQ_REMOVE(&pc->pc_grouplist, pcg, pcg_list);
			if (pc->pc_freeto == pcg)
				pc->pc_freeto = NULL;
			s = splvm();
			pool_put(&pcgpool, pcg);
			splx(s);
		}
	}
}

/*
 * pool_cache_invalidate:
 *
 *	Invalidate a pool cache (destruct and release all of the
 *	cached objects).
 */
void
pool_cache_invalidate(struct pool_cache *pc)
{

	simple_lock(&pc->pc_slock);
	pool_cache_do_invalidate(pc, 0, pool_put);
	simple_unlock(&pc->pc_slock);
}

/*
 * pool_cache_reclaim:
 *
 *	Reclaim a pool cache for pool_reclaim().
 */
static void
pool_cache_reclaim(struct pool_cache *pc)
{

	simple_lock(&pc->pc_slock);
	pool_cache_do_invalidate(pc, 1, pool_do_put);
	simple_unlock(&pc->pc_slock);
}

/*
 * Pool backend allocators.
 *
 * Each pool has a backend allocator that handles allocation, deallocation,
 * and any additional draining that might be needed.
 *
 * We provide two standard allocators:
 *
 *	pool_allocator_kmem - the default when no allocator is specified
 *
 *	pool_allocator_nointr - used for pools that will not be accessed
 *	in interrupt context.
 */
void	*pool_page_alloc(struct pool *, int);
void	pool_page_free(struct pool *, void *);

struct pool_allocator pool_allocator_kmem = {
	pool_page_alloc, pool_page_free, 0,
};

void	*pool_page_alloc_nointr(struct pool *, int);
void	pool_page_free_nointr(struct pool *, void *);

struct pool_allocator pool_allocator_nointr = {
	pool_page_alloc_nointr, pool_page_free_nointr, 0,
};

#ifdef POOL_SUBPAGE
void	*pool_subpage_alloc(struct pool *, int);
void	pool_subpage_free(struct pool *, void *);

struct pool_allocator pool_allocator_kmem_subpage = {
	pool_subpage_alloc, pool_subpage_free, 0,
};
#endif /* POOL_SUBPAGE */

/*
 * We have at least three different resources for the same allocation and
 * each resource can be depleted.  First, we have the ready elements in the
 * pool.  Then we have the resource (typically a vm_map) for this allocator.
 * Finally, we have physical memory.  Waiting for any of these can be
 * unnecessary when any other is freed, but the kernel doesn't support
 * sleeping on multiple wait channels, so we have to employ another strategy.
 *
 * The caller sleeps on the pool (so that it can be awakened when an item
 * is returned to the pool), but we set PA_WANT on the allocator.  When a
 * page is returned to the allocator and PA_WANT is set, pool_allocator_free
 * will wake up all sleeping pools belonging to this allocator.
 *
 * XXX Thundering herd.
 */
void *
pool_allocator_alloc(struct pool *org, int flags)
{
	struct pool_allocator *pa = org->pr_alloc;
	struct pool *pp, *start;
	int s, freed;
	void *res;

	do {
		if ((res = (*pa->pa_alloc)(org, flags)) != NULL)
			return (res);
		if ((flags & PR_WAITOK) == 0)
			break;

		/*
		 * Drain all pools, except "org", that use this
		 * allocator.  We do this to reclaim VA space.
		 * pa_alloc is responsible for waiting for
		 * physical memory.
		 *
		 * XXX We risk looping forever if start if someone
		 * calls pool_destroy on "start".  But there is no
		 * other way to have potentially sleeping pool_reclaim,
		 * non-sleeping locks on pool_allocator, and some
		 * stirring of drained pools in the allocator.
		 */
		freed = 0;

		s = splvm();
		simple_lock(&pa->pa_slock);
		pp = start = TAILQ_FIRST(&pa->pa_list);
		do {
			TAILQ_REMOVE(&pa->pa_list, pp, pr_alloc_list);
			TAILQ_INSERT_TAIL(&pa->pa_list, pp, pr_alloc_list);
			if (pp == org)
				continue;
			simple_unlock(&pa->pa_list);
			freed = pool_reclaim(pp);
			simple_lock(&pa->pa_list);
		} while ((pp = TAILQ_FIRST(&pa->pa_list)) != start &&
			 freed == 0);

		if (freed == 0) {
			/*
			 * We set PA_WANT here, the caller will most likely
			 * sleep waiting for pages (if not, this won't hurt
			 * that much), and there is no way to set this in
			 * the caller without violating locking order.
			 */
			pa->pa_flags |= PA_WANT;
		}
		simple_unlock(&pa->pa_slock);
		splx(s);
	} while (freed);
	return (NULL);
}

void
pool_allocator_free(struct pool *pp, void *v)
{
	struct pool_allocator *pa = pp->pr_alloc;
	int s;

	(*pa->pa_free)(pp, v);

	s = splvm();
	simple_lock(&pa->pa_slock);
	if ((pa->pa_flags & PA_WANT) == 0) {
		simple_unlock(&pa->pa_slock);
		splx(s);
		return;
	}

	TAILQ_FOREACH(pp, &pa->pa_list, pr_alloc_list) {
		simple_lock(&pp->pr_slock);
		if ((pp->pr_flags & PR_WANTED) != 0) {
			pp->pr_flags &= ~PR_WANTED;
			wakeup(pp);
		}
	}
	pa->pa_flags &= ~PA_WANT;
	simple_unlock(&pa->pa_slock);
	splx(s);
}

void *
pool_page_alloc(struct pool *pp, int flags)
{
	boolean_t waitok = (flags & PR_WAITOK) ? TRUE : FALSE;

	return ((void *) uvm_km_alloc_poolpage(waitok));
}

void
pool_page_free(struct pool *pp, void *v)
{

	uvm_km_free_poolpage((vaddr_t) v);
}

#ifdef POOL_SUBPAGE
/* Sub-page allocator, for machines with large hardware pages. */
void *
pool_subpage_alloc(struct pool *pp, int flags)
{

	return (pool_get(&psppool, flags));
}

void
pool_subpage_free(struct pool *pp, void *v)
{

	pool_put(&psppool, v);
}

/* We don't provide a real nointr allocator.  Maybe later. */
void *
pool_page_alloc_nointr(struct pool *pp, int flags)
{

	return (pool_subpage_alloc(pp, flags));
}

void
pool_page_free_nointr(struct pool *pp, void *v)
{

	pool_subpage_free(pp, v);
}
#else
void *
pool_page_alloc_nointr(struct pool *pp, int flags)
{
	boolean_t waitok = (flags & PR_WAITOK) ? TRUE : FALSE;

	return ((void *) uvm_km_alloc_poolpage1(kernel_map,
	    uvm.kernel_object, waitok));
}

void
pool_page_free_nointr(struct pool *pp, void *v)
{

	uvm_km_free_poolpage1(kernel_map, (vaddr_t) v);
}
#endif /* POOL_SUBPAGE */