common/vm/vm_seg.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
/*	  All Rights Reserved  	*/

/*
 * University Copyright- Copyright (c) 1982, 1986, 1988
 * The Regents of the University of California
 * All Rights Reserved
 *
 * University Acknowledgment- Portions of this document are derived from
 * software developed by the University of California, Berkeley, and its
 * contributors.
 */

#pragma ident	"%Z%%M%	%I%	%E% SMI"

/*
 * VM - segment management.
 */

#include <sys/types.h>
#include <sys/inttypes.h>
#include <sys/t_lock.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kmem.h>
#include <sys/sysmacros.h>
#include <sys/vmsystm.h>
#include <sys/tuneable.h>
#include <sys/debug.h>
#include <sys/fs/swapnode.h>
#include <sys/cmn_err.h>
#include <sys/callb.h>
#include <sys/mem_config.h>
#include <sys/mman.h>

#include <vm/hat.h>
#include <vm/as.h>
#include <vm/seg.h>
#include <vm/seg_kmem.h>
#include <vm/seg_spt.h>
#include <vm/seg_vn.h>
#include <vm/anon.h>

/*
 * kstats for segment advise
 */
segadvstat_t segadvstat = {
	{ "MADV_FREE_hit",	KSTAT_DATA_ULONG },
	{ "MADV_FREE_miss",	KSTAT_DATA_ULONG },
};

kstat_named_t *segadvstat_ptr = (kstat_named_t *)&segadvstat;
uint_t segadvstat_ndata = sizeof (segadvstat) / sizeof (kstat_named_t);

/*
 * entry in the segment page cache
 */
struct seg_pcache {
	struct seg_pcache	*p_hnext;	/* list for hashed blocks */
	struct seg_pcache	*p_hprev;
	pcache_link_t		p_plink;	/* per segment/amp list */
	void 			*p_htag0;	/* segment/amp pointer */
	caddr_t			p_addr;		/* base address/anon_idx */
	size_t			p_len;		/* total bytes */
	size_t			p_wlen;		/* writtable bytes at p_addr */
	struct page		**p_pp;		/* pp shadow list */
	seg_preclaim_cbfunc_t	p_callback;	/* reclaim callback function */
	clock_t			p_lbolt;	/* lbolt from last use */
	struct seg_phash	*p_hashp;	/* our pcache hash bucket */
	uint_t			p_active;	/* active count */
	uchar_t			p_write;	/* true if S_WRITE */
	uchar_t			p_ref;		/* reference byte */
	ushort_t		p_flags;	/* bit flags */
};

struct seg_phash {
	struct seg_pcache	*p_hnext;	/* list for hashed blocks */
	struct seg_pcache	*p_hprev;
	kmutex_t		p_hmutex;	/* protects hash bucket */
	pcache_link_t		p_halink[2];	/* active bucket linkages */
};

struct seg_phash_wired {
	struct seg_pcache	*p_hnext;	/* list for hashed blocks */
	struct seg_pcache	*p_hprev;
	kmutex_t		p_hmutex;	/* protects hash bucket */
};

/*
 * A parameter to control a maximum number of bytes that can be
 * purged from pcache at a time.
 */
#define	P_MAX_APURGE_BYTES	(1024 * 1024 * 1024)

/*
 * log2(fraction of pcache to reclaim at a time).
 */
#define	P_SHRINK_SHFT		(5)

/*
 * The following variables can be tuned via /etc/system.
 */

int	segpcache_enabled = 1;		/* if 1, shadow lists are cached */
pgcnt_t	segpcache_maxwindow = 0;	/* max # of pages that can be cached */
ulong_t	segpcache_hashsize_win = 0;	/* # of non wired buckets */
ulong_t	segpcache_hashsize_wired = 0;	/* # of wired buckets */
int	segpcache_reap_sec = 1;		/* reap check rate in secs */
clock_t	segpcache_reap_ticks = 0;	/* reap interval in ticks */
int	segpcache_pcp_maxage_sec = 1;	/* pcp max age in secs */
clock_t	segpcache_pcp_maxage_ticks = 0;	/* pcp max age in ticks */
int	segpcache_shrink_shift = P_SHRINK_SHFT;	/* log2 reap fraction */
pgcnt_t	segpcache_maxapurge_bytes = P_MAX_APURGE_BYTES;	/* max purge bytes */

static kmutex_t seg_pcache_mtx;	/* protects seg_pdisabled counter */
static kmutex_t seg_pasync_mtx;	/* protects async thread scheduling */
static kcondvar_t seg_pasync_cv;

#pragma align 64(pctrl1)
#pragma align 64(pctrl2)
#pragma align 64(pctrl3)

/*
 * Keep frequently used variables together in one cache line.
 */
static struct p_ctrl1 {
	uint_t p_disabled;		/* if not 0, caching temporarily off */
	pgcnt_t p_maxwin;		/* max # of pages that can be cached */
	size_t p_hashwin_sz;		/* # of non wired buckets */
	struct seg_phash *p_htabwin;	/* hash table for non wired entries */
	size_t p_hashwired_sz;		/* # of wired buckets */
	struct seg_phash_wired *p_htabwired; /* hash table for wired entries */
	kmem_cache_t *p_kmcache;	/* kmem cache for seg_pcache structs */
#ifdef _LP64
	ulong_t pad[1];
#endif /* _LP64 */
} pctrl1;

static struct p_ctrl2 {
	kmutex_t p_mem_mtx;	/* protects window counter and p_halinks */
	pgcnt_t  p_locked_win;	/* # pages from window */
	pgcnt_t  p_locked;	/* # of pages cached by pagelock */
	uchar_t	 p_ahcur;	/* current active links for insert/delete */
	uchar_t  p_athr_on;	/* async reclaim thread is running. */
	pcache_link_t p_ahhead[2]; /* active buckets linkages */
} pctrl2;

static struct p_ctrl3 {
	clock_t	p_pcp_maxage;		/* max pcp age in ticks */
	ulong_t	p_athr_empty_ahb;	/* athread walk stats */
	ulong_t p_athr_full_ahb;	/* athread walk stats */
	pgcnt_t	p_maxapurge_npages;	/* max pages to purge at a time */
	int	p_shrink_shft;		/* reap shift factor */
#ifdef _LP64
	ulong_t pad[3];
#endif /* _LP64 */
} pctrl3;

#define	seg_pdisabled			pctrl1.p_disabled
#define	seg_pmaxwindow			pctrl1.p_maxwin
#define	seg_phashsize_win		pctrl1.p_hashwin_sz
#define	seg_phashtab_win		pctrl1.p_htabwin
#define	seg_phashsize_wired		pctrl1.p_hashwired_sz
#define	seg_phashtab_wired		pctrl1.p_htabwired
#define	seg_pkmcache			pctrl1.p_kmcache
#define	seg_pmem_mtx			pctrl2.p_mem_mtx
#define	seg_plocked_window		pctrl2.p_locked_win
#define	seg_plocked			pctrl2.p_locked
#define	seg_pahcur			pctrl2.p_ahcur
#define	seg_pathr_on			pctrl2.p_athr_on
#define	seg_pahhead			pctrl2.p_ahhead
#define	seg_pmax_pcpage			pctrl3.p_pcp_maxage
#define	seg_pathr_empty_ahb		pctrl3.p_athr_empty_ahb
#define	seg_pathr_full_ahb		pctrl3.p_athr_full_ahb
#define	seg_pshrink_shift		pctrl3.p_shrink_shft
#define	seg_pmaxapurge_npages		pctrl3.p_maxapurge_npages

#define	P_HASHWIN_MASK			(seg_phashsize_win - 1)
#define	P_HASHWIRED_MASK		(seg_phashsize_wired - 1)
#define	P_BASESHIFT			(6)

kthread_t *seg_pasync_thr;

extern struct seg_ops segvn_ops;
extern struct seg_ops segspt_shmops;

#define	IS_PFLAGS_WIRED(flags) ((flags) & SEGP_FORCE_WIRED)
#define	IS_PCP_WIRED(pcp) IS_PFLAGS_WIRED((pcp)->p_flags)

#define	LBOLT_DELTA(t)	((ulong_t)(lbolt - (t)))

#define	PCP_AGE(pcp)	LBOLT_DELTA((pcp)->p_lbolt)

/*
 * htag0 argument can be a seg or amp pointer.
 */
#define	P_HASHBP(seg, htag0, addr, flags)				\
	(IS_PFLAGS_WIRED((flags)) ?					\
	    ((struct seg_phash *)&seg_phashtab_wired[P_HASHWIRED_MASK &	\
	    ((uintptr_t)(htag0) >> P_BASESHIFT)]) :			\
	    (&seg_phashtab_win[P_HASHWIN_MASK &				\
	    (((uintptr_t)(htag0) >> 3) ^				\
	    ((uintptr_t)(addr) >> ((flags & SEGP_PSHIFT) ?		\
	    (flags >> 16) : page_get_shift((seg)->s_szc))))]))

/*
 * htag0 argument can be a seg or amp pointer.
 */
#define	P_MATCH(pcp, htag0, addr, len)					\
	((pcp)->p_htag0 == (htag0) &&					\
	(pcp)->p_addr == (addr) &&					\
	(pcp)->p_len >= (len))

#define	P_MATCH_PP(pcp, htag0, addr, len, pp)				\
	((pcp)->p_pp == (pp) &&						\
	(pcp)->p_htag0 == (htag0) &&					\
	(pcp)->p_addr == (addr) &&					\
	(pcp)->p_len >= (len))

#define	plink2pcache(pl)	((struct seg_pcache *)((uintptr_t)(pl) - \
    offsetof(struct seg_pcache, p_plink)))

#define	hlink2phash(hl, l)	((struct seg_phash *)((uintptr_t)(hl) -	\
    offsetof(struct seg_phash, p_halink[l])))

/*
 * seg_padd_abuck()/seg_premove_abuck() link and unlink hash buckets from
 * active hash bucket lists. We maintain active bucket lists to reduce the
 * overhead of finding active buckets during asynchronous purging since there
 * can be 10s of millions of buckets on a large system but only a small subset
 * of them in actual use.
 *
 * There're 2 active bucket lists. Current active list (as per seg_pahcur) is
 * used by seg_pinsert()/seg_pinactive()/seg_ppurge() to add and delete
 * buckets. The other list is used by asynchronous purge thread. This allows
 * the purge thread to walk its active list without holding seg_pmem_mtx for a
 * long time. When asynchronous thread is done with its list it switches to
 * current active list and makes the list it just finished processing as
 * current active list.
 *
 * seg_padd_abuck() only adds the bucket to current list if the bucket is not
 * yet on any list.  seg_premove_abuck() may remove the bucket from either
 * list. If the bucket is on current list it will be always removed. Otherwise
 * the bucket is only removed if asynchronous purge thread is not currently
 * running or seg_premove_abuck() is called by asynchronous purge thread
 * itself. A given bucket can only be on one of active lists at a time. These
 * routines should be called with per bucket lock held.  The routines use
 * seg_pmem_mtx to protect list updates. seg_padd_abuck() must be called after
 * the first entry is added to the bucket chain and seg_premove_abuck() must
 * be called after the last pcp entry is deleted from its chain. Per bucket
 * lock should be held by the callers.  This avoids a potential race condition
 * when seg_premove_abuck() removes a bucket after pcp entries are added to
 * its list after the caller checked that the bucket has no entries. (this
 * race would cause a loss of an active bucket from the active lists).
 *
 * Both lists are circular doubly linked lists anchored at seg_pahhead heads.
 * New entries are added to the end of the list since LRU is used as the
 * purging policy.
 */
static void
seg_padd_abuck(struct seg_phash *hp)
{
	int lix;

	ASSERT(MUTEX_HELD(&hp->p_hmutex));
	ASSERT((struct seg_phash *)hp->p_hnext != hp);
	ASSERT((struct seg_phash *)hp->p_hprev != hp);
	ASSERT(hp->p_hnext == hp->p_hprev);
	ASSERT(!IS_PCP_WIRED(hp->p_hnext));
	ASSERT(hp->p_hnext->p_hnext == (struct seg_pcache *)hp);
	ASSERT(hp->p_hprev->p_hprev == (struct seg_pcache *)hp);
	ASSERT(hp >= seg_phashtab_win &&
	    hp < &seg_phashtab_win[seg_phashsize_win]);

	/*
	 * This bucket can already be on one of active lists
	 * since seg_premove_abuck() may have failed to remove it
	 * before.
	 */
	mutex_enter(&seg_pmem_mtx);
	lix = seg_pahcur;
	ASSERT(lix >= 0 && lix <= 1);
	if (hp->p_halink[lix].p_lnext != NULL) {
		ASSERT(hp->p_halink[lix].p_lprev != NULL);
		ASSERT(hp->p_halink[!lix].p_lnext == NULL);
		ASSERT(hp->p_halink[!lix].p_lprev == NULL);
		mutex_exit(&seg_pmem_mtx);
		return;
	}
	ASSERT(hp->p_halink[lix].p_lprev == NULL);

	/*
	 * If this bucket is still on list !lix async thread can't yet remove
	 * it since we hold here per bucket lock. In this case just return
	 * since async thread will eventually find and process this bucket.
	 */
	if (hp->p_halink[!lix].p_lnext != NULL) {
		ASSERT(hp->p_halink[!lix].p_lprev != NULL);
		mutex_exit(&seg_pmem_mtx);
		return;
	}
	ASSERT(hp->p_halink[!lix].p_lprev == NULL);
	/*
	 * This bucket is not on any active bucket list yet.
	 * Add the bucket to the tail of current active list.
	 */
	hp->p_halink[lix].p_lnext = &seg_pahhead[lix];
	hp->p_halink[lix].p_lprev = seg_pahhead[lix].p_lprev;
	seg_pahhead[lix].p_lprev->p_lnext = &hp->p_halink[lix];
	seg_pahhead[lix].p_lprev = &hp->p_halink[lix];
	mutex_exit(&seg_pmem_mtx);
}

static void
seg_premove_abuck(struct seg_phash *hp, int athr)
{
	int lix;

	ASSERT(MUTEX_HELD(&hp->p_hmutex));
	ASSERT((struct seg_phash *)hp->p_hnext == hp);
	ASSERT((struct seg_phash *)hp->p_hprev == hp);
	ASSERT(hp >= seg_phashtab_win &&
	    hp < &seg_phashtab_win[seg_phashsize_win]);

	if (athr) {
		ASSERT(seg_pathr_on);
		ASSERT(seg_pahcur <= 1);
		/*
		 * We are called by asynchronous thread that found this bucket
		 * on not currently active (i.e. !seg_pahcur) list. Remove it
		 * from there.  Per bucket lock we are holding makes sure
		 * seg_pinsert() can't sneak in and add pcp entries to this
		 * bucket right before we remove the bucket from its list.
		 */
		lix = !seg_pahcur;
		ASSERT(hp->p_halink[lix].p_lnext != NULL);
		ASSERT(hp->p_halink[lix].p_lprev != NULL);
		ASSERT(hp->p_halink[!lix].p_lnext == NULL);
		ASSERT(hp->p_halink[!lix].p_lprev == NULL);
		hp->p_halink[lix].p_lnext->p_lprev = hp->p_halink[lix].p_lprev;
		hp->p_halink[lix].p_lprev->p_lnext = hp->p_halink[lix].p_lnext;
		hp->p_halink[lix].p_lnext = NULL;
		hp->p_halink[lix].p_lprev = NULL;
		return;
	}

	mutex_enter(&seg_pmem_mtx);
	lix = seg_pahcur;
	ASSERT(lix >= 0 && lix <= 1);

	/*
	 * If the bucket is on currently active list just remove it from
	 * there.
	 */
	if (hp->p_halink[lix].p_lnext != NULL) {
		ASSERT(hp->p_halink[lix].p_lprev != NULL);
		ASSERT(hp->p_halink[!lix].p_lnext == NULL);
		ASSERT(hp->p_halink[!lix].p_lprev == NULL);
		hp->p_halink[lix].p_lnext->p_lprev = hp->p_halink[lix].p_lprev;
		hp->p_halink[lix].p_lprev->p_lnext = hp->p_halink[lix].p_lnext;
		hp->p_halink[lix].p_lnext = NULL;
		hp->p_halink[lix].p_lprev = NULL;
		mutex_exit(&seg_pmem_mtx);
		return;
	}
	ASSERT(hp->p_halink[lix].p_lprev == NULL);

	/*
	 * If asynchronous thread is not running we can remove the bucket from
	 * not currently active list. The bucket must be on this list since we
	 * already checked that it's not on the other list and the bucket from
	 * which we just deleted the last pcp entry must be still on one of the
	 * active bucket lists.
	 */
	lix = !lix;
	ASSERT(hp->p_halink[lix].p_lnext != NULL);
	ASSERT(hp->p_halink[lix].p_lprev != NULL);

	if (!seg_pathr_on) {
		hp->p_halink[lix].p_lnext->p_lprev = hp->p_halink[lix].p_lprev;
		hp->p_halink[lix].p_lprev->p_lnext = hp->p_halink[lix].p_lnext;
		hp->p_halink[lix].p_lnext = NULL;
		hp->p_halink[lix].p_lprev = NULL;
	}
	mutex_exit(&seg_pmem_mtx);
}

/*
 * Check if bucket pointed by hp already has a pcp entry that matches request
 * htag0, addr and len. Set *found to 1 if match is found and to 0 otherwise.
 * Also delete matching entries that cover smaller address range but start
 * at the same address as addr argument. Return the list of deleted entries if
 * any. This is an internal helper function called from seg_pinsert() only
 * for non wired shadow lists. The caller already holds a per seg/amp list
 * lock.
 */
static struct seg_pcache *
seg_plookup_checkdup(struct seg_phash *hp, void *htag0,
    caddr_t addr, size_t len, int *found)
{
	struct seg_pcache *pcp;
	struct seg_pcache *delcallb_list = NULL;

	ASSERT(MUTEX_HELD(&hp->p_hmutex));

	*found = 0;
	for (pcp = hp->p_hnext; pcp != (struct seg_pcache *)hp;
	    pcp = pcp->p_hnext) {
		ASSERT(pcp->p_hashp == hp);
		if (pcp->p_htag0 == htag0 && pcp->p_addr == addr) {
			ASSERT(!IS_PCP_WIRED(pcp));
			if (pcp->p_len < len) {
				pcache_link_t *plinkp;
				if (pcp->p_active) {
					continue;
				}
				plinkp = &pcp->p_plink;
				plinkp->p_lprev->p_lnext = plinkp->p_lnext;
				plinkp->p_lnext->p_lprev = plinkp->p_lprev;
				pcp->p_hprev->p_hnext = pcp->p_hnext;
				pcp->p_hnext->p_hprev = pcp->p_hprev;
				pcp->p_hprev = delcallb_list;
				delcallb_list = pcp;
			} else {
				*found = 1;
				break;
			}
		}
	}
	return (delcallb_list);
}

/*
 * lookup an address range in pagelock cache. Return shadow list and bump up
 * active count. If amp is not NULL use amp as a lookup tag otherwise use seg
 * as a lookup tag.
 */
struct page **
seg_plookup(struct seg *seg, struct anon_map *amp, caddr_t addr, size_t len,
    enum seg_rw rw, uint_t flags)
{
	struct seg_pcache *pcp;
	struct seg_phash *hp;
	void *htag0;

	ASSERT(seg != NULL);
	ASSERT(rw == S_READ || rw == S_WRITE);

	/*
	 * Skip pagelock cache, while DR is in progress or
	 * seg_pcache is off.
	 */
	if (seg_pdisabled) {
		return (NULL);
	}
	ASSERT(seg_phashsize_win != 0);

	htag0 = (amp == NULL ? (void *)seg : (void *)amp);
	hp = P_HASHBP(seg, htag0, addr, flags);
	mutex_enter(&hp->p_hmutex);
	for (pcp = hp->p_hnext; pcp != (struct seg_pcache *)hp;
	    pcp = pcp->p_hnext) {
		ASSERT(pcp->p_hashp == hp);
		if (P_MATCH(pcp, htag0, addr, len)) {
			ASSERT(IS_PFLAGS_WIRED(flags) == IS_PCP_WIRED(pcp));
			/*
			 * If this request wants to write pages
			 * but write permissions starting from
			 * addr don't cover the entire length len
			 * return lookup failure back to the caller.
			 * It will check protections and fail this
			 * pagelock operation with EACCESS error.
			 */
			if (rw == S_WRITE && pcp->p_wlen < len) {
				break;
			}
			if (pcp->p_active == UINT_MAX) {
				break;
			}
			pcp->p_active++;
			if (rw == S_WRITE && !pcp->p_write) {
				pcp->p_write = 1;
			}
			mutex_exit(&hp->p_hmutex);
			return (pcp->p_pp);
		}
	}
	mutex_exit(&hp->p_hmutex);
	return (NULL);
}

/*
 * mark address range inactive. If the cache is off or the address range is
 * not in the cache or another shadow list that covers bigger range is found
 * we call the segment driver to reclaim the pages. Otherwise just decrement
 * active count and set ref bit.  If amp is not NULL use amp as a lookup tag
 * otherwise use seg as a lookup tag.
 */
void
seg_pinactive(struct seg *seg, struct anon_map *amp, caddr_t addr,
    size_t len, struct page **pp, enum seg_rw rw, uint_t flags,
    seg_preclaim_cbfunc_t callback)
{
	struct seg_pcache *pcp;
	struct seg_phash *hp;
	kmutex_t *pmtx = NULL;
	pcache_link_t *pheadp;
	void *htag0;
	pgcnt_t npages = 0;
	int keep = 0;

	ASSERT(seg != NULL);
	ASSERT(rw == S_READ || rw == S_WRITE);

	htag0 = (amp == NULL ? (void *)seg : (void *)amp);

	/*
	 * Skip lookup if pcache is not configured.
	 */
	if (seg_phashsize_win == 0) {
		goto out;
	}

	/*
	 * Grab per seg/amp lock before hash lock if we are going to remove
	 * inactive entry from pcache.
	 */
	if (!IS_PFLAGS_WIRED(flags) && seg_pdisabled) {
		if (amp == NULL) {
			pheadp = &seg->s_phead;
			pmtx = &seg->s_pmtx;
		} else {
			pheadp = &amp->a_phead;
			pmtx = &amp->a_pmtx;
		}
		mutex_enter(pmtx);
	}

	hp = P_HASHBP(seg, htag0, addr, flags);
	mutex_enter(&hp->p_hmutex);
again:
	for (pcp = hp->p_hnext; pcp != (struct seg_pcache *)hp;
	    pcp = pcp->p_hnext) {
		ASSERT(pcp->p_hashp == hp);
		if (P_MATCH_PP(pcp, htag0, addr, len, pp)) {
			ASSERT(IS_PFLAGS_WIRED(flags) == IS_PCP_WIRED(pcp));
			ASSERT(pcp->p_active);
			if (keep) {
				/*
				 * Don't remove this pcp entry
				 * if we didn't find duplicate
				 * shadow lists on second search.
				 * Somebody removed those duplicates
				 * since we dropped hash lock after first
				 * search.
				 */
				ASSERT(pmtx != NULL);
				ASSERT(!IS_PFLAGS_WIRED(flags));
				mutex_exit(pmtx);
				pmtx = NULL;
			}
			pcp->p_active--;
			if (pcp->p_active == 0 && (pmtx != NULL ||
			    (seg_pdisabled && IS_PFLAGS_WIRED(flags)))) {

				/*
				 * This entry is no longer active.  Remove it
				 * now either because pcaching is temporarily
				 * disabled or there're other pcp entries that
				 * can match this pagelock request (i.e. this
				 * entry is a duplicate).
				 */

				ASSERT(callback == pcp->p_callback);
				if (pmtx != NULL) {
					pcache_link_t *plinkp = &pcp->p_plink;
					ASSERT(!IS_PCP_WIRED(pcp));
					ASSERT(pheadp->p_lnext != pheadp);
					ASSERT(pheadp->p_lprev != pheadp);
					plinkp->p_lprev->p_lnext =
					    plinkp->p_lnext;
					plinkp->p_lnext->p_lprev =
					    plinkp->p_lprev;
				}
				pcp->p_hprev->p_hnext = pcp->p_hnext;
				pcp->p_hnext->p_hprev = pcp->p_hprev;
				if (!IS_PCP_WIRED(pcp) &&
				    hp->p_hnext == (struct seg_pcache *)hp) {
					/*
					 * We removed the last entry from this
					 * bucket.  Now remove the bucket from
					 * its active list.
					 */
					seg_premove_abuck(hp, 0);
				}
				mutex_exit(&hp->p_hmutex);
				if (pmtx != NULL) {
					mutex_exit(pmtx);
				}
				len = pcp->p_len;
				npages = btop(len);
				if (rw != S_WRITE && pcp->p_write) {
					rw = S_WRITE;
				}
				kmem_cache_free(seg_pkmcache, pcp);
				goto out;
			} else {
				/*
				 * We found a matching pcp entry but will not
				 * free it right away even if it's no longer
				 * active.
				 */
				if (!pcp->p_active && !IS_PCP_WIRED(pcp)) {
					/*
					 * Set the reference bit and mark the
					 * time of last access to this pcp
					 * so that asynchronous thread doesn't
					 * free it immediately since
					 * it may be reactivated very soon.
					 */
					pcp->p_lbolt = lbolt;
					pcp->p_ref = 1;
				}
				mutex_exit(&hp->p_hmutex);
				if (pmtx != NULL) {
					mutex_exit(pmtx);
				}
				return;
			}
		} else if (!IS_PFLAGS_WIRED(flags) &&
		    P_MATCH(pcp, htag0, addr, len)) {
			/*
			 * This is a duplicate pcp entry.  This situation may
			 * happen if a bigger shadow list that covers our
			 * range was added while our entry was still active.
			 * Now we can free our pcp entry if it becomes
			 * inactive.
			 */
			if (!pcp->p_active) {
				/*
				 * Mark this entry as referenced just in case
				 * we'll free our own pcp entry soon.
				 */
				pcp->p_lbolt = lbolt;
				pcp->p_ref = 1;
			}
			if (pmtx != NULL) {
				/*
				 * we are already holding pmtx and found a
				 * duplicate.  Don't keep our own pcp entry.
				 */
				keep = 0;
				continue;
			}
			/*
			 * We have to use mutex_tryenter to attempt to lock
			 * seg/amp list lock since we already hold hash lock
			 * and seg/amp list lock is above hash lock in lock
			 * order.  If mutex_tryenter fails drop hash lock and
			 * retake both locks in correct order and research
			 * this hash chain.
			 */
			ASSERT(keep == 0);
			if (amp == NULL) {
				pheadp = &seg->s_phead;
				pmtx = &seg->s_pmtx;
			} else {
				pheadp = &amp->a_phead;
				pmtx = &amp->a_pmtx;
			}
			if (!mutex_tryenter(pmtx)) {
				mutex_exit(&hp->p_hmutex);
				mutex_enter(pmtx);
				mutex_enter(&hp->p_hmutex);
				/*
				 * If we don't find bigger shadow list on
				 * second search (it may happen since we
				 * dropped bucket lock) keep the entry that
				 * matches our own shadow list.
				 */
				keep = 1;
				goto again;
			}
		}
	}
	mutex_exit(&hp->p_hmutex);
	if (pmtx != NULL) {
		mutex_exit(pmtx);
	}
out:
	(*callback)(htag0, addr, len, pp, rw, 0);
	if (npages) {
		mutex_enter(&seg_pmem_mtx);
		ASSERT(seg_plocked >= npages);
		seg_plocked -= npages;
		if (!IS_PFLAGS_WIRED(flags)) {
			ASSERT(seg_plocked_window >= npages);
			seg_plocked_window -= npages;
		}
		mutex_exit(&seg_pmem_mtx);
	}

}

#ifdef DEBUG
static uint32_t p_insert_chk_mtbf = 0;
#endif

/*
 * The seg_pinsert_check() is used by segment drivers to predict whether
 * a call to seg_pinsert will fail and thereby avoid wasteful pre-processing.
 */
/*ARGSUSED*/
int
seg_pinsert_check(struct seg *seg, struct anon_map *amp, caddr_t addr,
    size_t len, uint_t flags)
{
	ASSERT(seg != NULL);

#ifdef DEBUG
	if (p_insert_chk_mtbf && !(gethrtime() % p_insert_chk_mtbf)) {
		return (SEGP_FAIL);
	}
#endif

	if (seg_pdisabled) {
		return (SEGP_FAIL);
	}
	ASSERT(seg_phashsize_win != 0);

	if (IS_PFLAGS_WIRED(flags)) {
		return (SEGP_SUCCESS);
	}

	if (seg_plocked_window + btop(len) > seg_pmaxwindow) {
		return (SEGP_FAIL);
	}

	if (freemem < desfree) {
		return (SEGP_FAIL);
	}

	return (SEGP_SUCCESS);
}

#ifdef DEBUG
static uint32_t p_insert_mtbf = 0;
#endif

/*
 * Insert address range with shadow list into pagelock cache if there's no
 * shadow list already cached for this address range. If the cache is off or
 * caching is temporarily disabled or the allowed 'window' is exceeded return
 * SEGP_FAIL. Otherwise return SEGP_SUCCESS.
 *
 * For non wired shadow lists (segvn case) include address in the hashing
 * function to avoid linking all the entries from the same segment or amp on
 * the same bucket.  amp is used instead of seg if amp is not NULL. Non wired
 * pcache entries are also linked on a per segment/amp list so that all
 * entries can be found quickly during seg/amp purge without walking the
 * entire pcache hash table.  For wired shadow lists (segspt case) we
 * don't use address hashing and per segment linking because the caller
 * currently inserts only one entry per segment that covers the entire
 * segment. If we used per segment linking even for segspt it would complicate
 * seg_ppurge_wiredpp() locking.
 *
 * Both hash bucket and per seg/amp locks need to be held before adding a non
 * wired entry to hash and per seg/amp lists. per seg/amp lock should be taken
 * first.
 *
 * This function will also remove from pcache old inactive shadow lists that
 * overlap with this request but cover smaller range for the same start
 * address.
 */
int
seg_pinsert(struct seg *seg, struct anon_map *amp, caddr_t addr, size_t len,
    size_t wlen, struct page **pp, enum seg_rw rw, uint_t flags,
    seg_preclaim_cbfunc_t callback)
{
	struct seg_pcache *pcp;
	struct seg_phash *hp;
	pgcnt_t npages;
	pcache_link_t *pheadp;
	kmutex_t *pmtx;
	struct seg_pcache *delcallb_list = NULL;

	ASSERT(seg != NULL);
	ASSERT(rw == S_READ || rw == S_WRITE);
	ASSERT(rw == S_READ || wlen == len);
	ASSERT(rw == S_WRITE || wlen <= len);
	ASSERT(amp == NULL || wlen == len);

#ifdef DEBUG
	if (p_insert_mtbf && !(gethrtime() % p_insert_mtbf)) {
		return (SEGP_FAIL);
	}
#endif

	if (seg_pdisabled) {
		return (SEGP_FAIL);
	}
	ASSERT(seg_phashsize_win != 0);

	ASSERT((len & PAGEOFFSET) == 0);
	npages = btop(len);
	mutex_enter(&seg_pmem_mtx);
	if (!IS_PFLAGS_WIRED(flags)) {
		if (seg_plocked_window + npages > seg_pmaxwindow) {
			mutex_exit(&seg_pmem_mtx);
			return (SEGP_FAIL);
		}
		seg_plocked_window += npages;
	}
	seg_plocked += npages;
	mutex_exit(&seg_pmem_mtx);

	pcp = kmem_cache_alloc(seg_pkmcache, KM_SLEEP);
	/*
	 * If amp is not NULL set htag0 to amp otherwise set it to seg.
	 */
	if (amp == NULL) {
		pcp->p_htag0 = (void *)seg;
		pcp->p_flags = flags & 0xffff;
	} else {
		pcp->p_htag0 = (void *)amp;
		pcp->p_flags = (flags & 0xffff) | SEGP_AMP;
	}
	pcp->p_addr = addr;
	pcp->p_len = len;
	pcp->p_wlen = wlen;
	pcp->p_pp = pp;
	pcp->p_write = (rw == S_WRITE);
	pcp->p_callback = callback;
	pcp->p_active = 1;

	hp = P_HASHBP(seg, pcp->p_htag0, addr, flags);
	if (!IS_PFLAGS_WIRED(flags)) {
		int found;
		void *htag0;
		if (amp == NULL) {
			pheadp = &seg->s_phead;
			pmtx = &seg->s_pmtx;
			htag0 = (void *)seg;
		} else {
			pheadp = &amp->a_phead;
			pmtx = &amp->a_pmtx;
			htag0 = (void *)amp;
		}
		mutex_enter(pmtx);
		mutex_enter(&hp->p_hmutex);
		delcallb_list = seg_plookup_checkdup(hp, htag0, addr,
		    len, &found);
		if (found) {
			mutex_exit(&hp->p_hmutex);
			mutex_exit(pmtx);
			mutex_enter(&seg_pmem_mtx);
			seg_plocked -= npages;
			seg_plocked_window -= npages;
			mutex_exit(&seg_pmem_mtx);
			kmem_cache_free(seg_pkmcache, pcp);
			goto out;
		}
		pcp->p_plink.p_lnext = pheadp->p_lnext;
		pcp->p_plink.p_lprev = pheadp;
		pheadp->p_lnext->p_lprev = &pcp->p_plink;
		pheadp->p_lnext = &pcp->p_plink;
	} else {
		mutex_enter(&hp->p_hmutex);
	}
	pcp->p_hashp = hp;
	pcp->p_hnext = hp->p_hnext;
	pcp->p_hprev = (struct seg_pcache *)hp;
	hp->p_hnext->p_hprev = pcp;
	hp->p_hnext = pcp;
	if (!IS_PFLAGS_WIRED(flags) &&
	    hp->p_hprev == pcp) {
		seg_padd_abuck(hp);
	}
	mutex_exit(&hp->p_hmutex);
	if (!IS_PFLAGS_WIRED(flags)) {
		mutex_exit(pmtx);
	}

out:
	npages = 0;
	while (delcallb_list != NULL) {
		pcp = delcallb_list;
		delcallb_list = pcp->p_hprev;
		ASSERT(!IS_PCP_WIRED(pcp) && !pcp->p_active);
		(void) (*pcp->p_callback)(pcp->p_htag0, pcp->p_addr,
		    pcp->p_len, pcp->p_pp, pcp->p_write ? S_WRITE : S_READ, 0);
		npages += btop(pcp->p_len);
		kmem_cache_free(seg_pkmcache, pcp);
	}
	if (npages) {
		ASSERT(!IS_PFLAGS_WIRED(flags));
		mutex_enter(&seg_pmem_mtx);
		ASSERT(seg_plocked >= npages);
		ASSERT(seg_plocked_window >= npages);
		seg_plocked -= npages;
		seg_plocked_window -= npages;
		mutex_exit(&seg_pmem_mtx);
	}

	return (SEGP_SUCCESS);
}

/*
 * purge entries from the pagelock cache if not active
 * and not recently used.
 */
static void
seg_ppurge_async(int force)
{
	struct seg_pcache *delcallb_list = NULL;
	struct seg_pcache *pcp;
	struct seg_phash *hp;
	pgcnt_t npages = 0;
	pgcnt_t npages_window = 0;
	pgcnt_t	npgs_to_purge;
	pgcnt_t npgs_purged = 0;
	int hlinks = 0;
	int hlix;
	pcache_link_t *hlinkp;
	pcache_link_t *hlnextp = NULL;
	int lowmem;
	int trim;

	ASSERT(seg_phashsize_win != 0);

	/*
	 * if the cache is off or empty, return
	 */
	if (seg_plocked == 0 || (!force && seg_plocked_window == 0)) {
		return;
	}

	if (!force) {
		lowmem = 0;
		trim = 0;
		if (freemem < lotsfree + needfree) {
			spgcnt_t fmem = MAX((spgcnt_t)(freemem - needfree), 0);
			if (fmem <= 5 * (desfree >> 2)) {
				lowmem = 1;
			} else if (fmem <= 7 * (lotsfree >> 3)) {
				if (seg_plocked_window >=
				    (availrmem_initial >> 1)) {
					lowmem = 1;
				}
			} else if (fmem < lotsfree) {
				if (seg_plocked_window >=
				    3 * (availrmem_initial >> 2)) {
					lowmem = 1;
				}
			}
		}
		if (seg_plocked_window >= 7 * (seg_pmaxwindow >> 3)) {
			trim = 1;
		}
		if (!lowmem && !trim) {
			return;
		}
		npgs_to_purge = seg_plocked_window >>
		    seg_pshrink_shift;
		if (lowmem) {
			npgs_to_purge = MIN(npgs_to_purge,
			    MAX(seg_pmaxapurge_npages, desfree));
		} else {
			npgs_to_purge = MIN(npgs_to_purge,
			    seg_pmaxapurge_npages);
		}
		if (npgs_to_purge == 0) {
			return;
		}
	} else {
		struct seg_phash_wired *hpw;

		ASSERT(seg_phashsize_wired != 0);

		for (hpw = seg_phashtab_wired;
		    hpw < &seg_phashtab_wired[seg_phashsize_wired]; hpw++) {

			if (hpw->p_hnext == (struct seg_pcache *)hpw) {
				continue;
			}

			mutex_enter(&hpw->p_hmutex);

			for (pcp = hpw->p_hnext;
			    pcp != (struct seg_pcache *)hpw;
			    pcp = pcp->p_hnext) {

				ASSERT(IS_PCP_WIRED(pcp));
				ASSERT(pcp->p_hashp ==
				    (struct seg_phash *)hpw);

				if (pcp->p_active) {
					continue;
				}
				pcp->p_hprev->p_hnext = pcp->p_hnext;
				pcp->p_hnext->p_hprev = pcp->p_hprev;
				pcp->p_hprev = delcallb_list;
				delcallb_list = pcp;
			}
			mutex_exit(&hpw->p_hmutex);
		}
	}

	mutex_enter(&seg_pmem_mtx);
	if (seg_pathr_on) {
		mutex_exit(&seg_pmem_mtx);
		goto runcb;
	}
	seg_pathr_on = 1;
	mutex_exit(&seg_pmem_mtx);
	ASSERT(seg_pahcur <= 1);
	hlix = !seg_pahcur;

again:
	for (hlinkp = seg_pahhead[hlix].p_lnext; hlinkp != &seg_pahhead[hlix];
	    hlinkp = hlnextp) {

		hlnextp = hlinkp->p_lnext;
		ASSERT(hlnextp != NULL);

		hp = hlink2phash(hlinkp, hlix);
		if (hp->p_hnext == (struct seg_pcache *)hp) {
			seg_pathr_empty_ahb++;
			continue;
		}
		seg_pathr_full_ahb++;
		mutex_enter(&hp->p_hmutex);

		for (pcp = hp->p_hnext; pcp != (struct seg_pcache *)hp;
		    pcp = pcp->p_hnext) {
			pcache_link_t *pheadp;
			pcache_link_t *plinkp;
			void *htag0;
			kmutex_t *pmtx;

			ASSERT(!IS_PCP_WIRED(pcp));
			ASSERT(pcp->p_hashp == hp);

			if (pcp->p_active) {
				continue;
			}
			if (!force && pcp->p_ref &&
			    PCP_AGE(pcp) < seg_pmax_pcpage) {
				pcp->p_ref = 0;
				continue;
			}
			plinkp = &pcp->p_plink;
			htag0 = pcp->p_htag0;
			if (pcp->p_flags & SEGP_AMP) {
				pheadp = &((amp_t *)htag0)->a_phead;
				pmtx = &((amp_t *)htag0)->a_pmtx;
			} else {
				pheadp = &((seg_t *)htag0)->s_phead;
				pmtx = &((seg_t *)htag0)->s_pmtx;
			}
			if (!mutex_tryenter(pmtx)) {
				continue;
			}
			ASSERT(pheadp->p_lnext != pheadp);
			ASSERT(pheadp->p_lprev != pheadp);
			plinkp->p_lprev->p_lnext =
			    plinkp->p_lnext;
			plinkp->p_lnext->p_lprev =
			    plinkp->p_lprev;
			pcp->p_hprev->p_hnext = pcp->p_hnext;
			pcp->p_hnext->p_hprev = pcp->p_hprev;
			mutex_exit(pmtx);
			pcp->p_hprev = delcallb_list;
			delcallb_list = pcp;
			npgs_purged += btop(pcp->p_len);
		}
		if (hp->p_hnext == (struct seg_pcache *)hp) {
			seg_premove_abuck(hp, 1);
		}
		mutex_exit(&hp->p_hmutex);
		if (npgs_purged >= seg_plocked_window) {
			break;
		}
		if (!force) {
			if (npgs_purged >= npgs_to_purge) {
				break;
			}
			if (!trim && !(seg_pathr_full_ahb & 15)) {
				ASSERT(lowmem);
				if (freemem >= lotsfree + needfree) {
					break;
				}
			}
		}
	}

	if (hlinkp == &seg_pahhead[hlix]) {
		/*
		 * We processed the entire hlix active bucket list
		 * but didn't find enough pages to reclaim.
		 * Switch the lists and walk the other list
		 * if we haven't done it yet.
		 */
		mutex_enter(&seg_pmem_mtx);
		ASSERT(seg_pathr_on);
		ASSERT(seg_pahcur == !hlix);
		seg_pahcur = hlix;
		mutex_exit(&seg_pmem_mtx);
		if (++hlinks < 2) {
			hlix = !hlix;
			goto again;
		}
	} else if ((hlinkp = hlnextp) != &seg_pahhead[hlix] &&
	    seg_pahhead[hlix].p_lnext != hlinkp) {
		ASSERT(hlinkp != NULL);
		ASSERT(hlinkp->p_lprev != &seg_pahhead[hlix]);
		ASSERT(seg_pahhead[hlix].p_lnext != &seg_pahhead[hlix]);
		ASSERT(seg_pahhead[hlix].p_lprev != &seg_pahhead[hlix]);

		/*
		 * Reinsert the header to point to hlinkp
		 * so that we start from hlinkp bucket next time around.
		 */
		seg_pahhead[hlix].p_lnext->p_lprev = seg_pahhead[hlix].p_lprev;
		seg_pahhead[hlix].p_lprev->p_lnext = seg_pahhead[hlix].p_lnext;
		seg_pahhead[hlix].p_lnext = hlinkp;
		seg_pahhead[hlix].p_lprev = hlinkp->p_lprev;
		hlinkp->p_lprev->p_lnext = &seg_pahhead[hlix];
		hlinkp->p_lprev = &seg_pahhead[hlix];
	}

	mutex_enter(&seg_pmem_mtx);
	ASSERT(seg_pathr_on);
	seg_pathr_on = 0;
	mutex_exit(&seg_pmem_mtx);

runcb:
	/*
	 * Run the delayed callback list. segments/amps can't go away until
	 * callback is executed since they must have non 0 softlockcnt. That's
	 * why we don't need to hold as/seg/amp locks to execute the callback.
	 */
	while (delcallb_list != NULL) {
		pcp = delcallb_list;
		delcallb_list = pcp->p_hprev;
		ASSERT(!pcp->p_active);
		(void) (*pcp->p_callback)(pcp->p_htag0, pcp->p_addr,
		    pcp->p_len, pcp->p_pp, pcp->p_write ? S_WRITE : S_READ, 1);
		npages += btop(pcp->p_len);
		if (!IS_PCP_WIRED(pcp)) {
			npages_window += btop(pcp->p_len);
		}
		kmem_cache_free(seg_pkmcache, pcp);
	}
	if (npages) {
		mutex_enter(&seg_pmem_mtx);
		ASSERT(seg_plocked >= npages);
		ASSERT(seg_plocked_window >= npages_window);
		seg_plocked -= npages;
		seg_plocked_window -= npages_window;
		mutex_exit(&seg_pmem_mtx);
	}
}

/*
 * Remove cached pages for segment(s) entries from hashtable.  The segments
 * are identified by pp array. This is useful for multiple seg's cached on
 * behalf of dummy segment (ISM/DISM) with common pp array.
 */
void
seg_ppurge_wiredpp(struct page **pp)
{
	struct seg_pcache *pcp;
	struct seg_phash_wired *hp;
	pgcnt_t npages = 0;
	struct	seg_pcache *delcallb_list = NULL;

	/*
	 * if the cache is empty, return
	 */
	if (seg_plocked == 0) {
		return;
	}
	ASSERT(seg_phashsize_wired != 0);

	for (hp = seg_phashtab_wired;
	    hp < &seg_phashtab_wired[seg_phashsize_wired]; hp++) {
		if (hp->p_hnext == (struct seg_pcache *)hp) {
			continue;
		}
		mutex_enter(&hp->p_hmutex);
		pcp = hp->p_hnext;
		while (pcp != (struct seg_pcache *)hp) {
			ASSERT(pcp->p_hashp == (struct seg_phash *)hp);
			ASSERT(IS_PCP_WIRED(pcp));
			/*
			 * purge entries which are not active
			 */
			if (!pcp->p_active && pcp->p_pp == pp) {
				ASSERT(pcp->p_htag0 != NULL);
				pcp->p_hprev->p_hnext = pcp->p_hnext;
				pcp->p_hnext->p_hprev = pcp->p_hprev;
				pcp->p_hprev = delcallb_list;
				delcallb_list = pcp;
			}
			pcp = pcp->p_hnext;
		}
		mutex_exit(&hp->p_hmutex);
		/*
		 * segments can't go away until callback is executed since
		 * they must have non 0 softlockcnt. That's why we don't
		 * need to hold as/seg locks to execute the callback.
		 */
		while (delcallb_list != NULL) {
			int done;
			pcp = delcallb_list;
			delcallb_list = pcp->p_hprev;
			ASSERT(!pcp->p_active);
			done = (*pcp->p_callback)(pcp->p_htag0, pcp->p_addr,
			    pcp->p_len, pcp->p_pp,
			    pcp->p_write ? S_WRITE : S_READ, 1);
			npages += btop(pcp->p_len);
			ASSERT(IS_PCP_WIRED(pcp));
			kmem_cache_free(seg_pkmcache, pcp);
			if (done) {
				ASSERT(delcallb_list == NULL);
				goto out;
			}
		}
	}

out:
	mutex_enter(&seg_pmem_mtx);
	ASSERT(seg_plocked >= npages);
	seg_plocked -= npages;
	mutex_exit(&seg_pmem_mtx);
}

/*
 * purge all entries for a given segment. Since we
 * callback into the segment driver directly for page
 * reclaim the caller needs to hold the right locks.
 */
void
seg_ppurge(struct seg *seg, struct anon_map *amp, uint_t flags)
{
	struct seg_pcache *delcallb_list = NULL;
	struct seg_pcache *pcp;
	struct seg_phash *hp;
	pgcnt_t npages = 0;
	void *htag0;

	if (seg_plocked == 0) {
		return;
	}
	ASSERT(seg_phashsize_win != 0);

	/*
	 * If amp is not NULL use amp as a lookup tag otherwise use seg
	 * as a lookup tag.
	 */
	htag0 = (amp == NULL ? (void *)seg : (void *)amp);
	ASSERT(htag0 != NULL);
	if (IS_PFLAGS_WIRED(flags)) {
		hp = P_HASHBP(seg, htag0, 0, flags);
		mutex_enter(&hp->p_hmutex);
		pcp = hp->p_hnext;
		while (pcp != (struct seg_pcache *)hp) {
			ASSERT(pcp->p_hashp == hp);
			ASSERT(IS_PCP_WIRED(pcp));
			if (pcp->p_htag0 == htag0) {
				if (pcp->p_active) {
					break;
				}
				pcp->p_hprev->p_hnext = pcp->p_hnext;
				pcp->p_hnext->p_hprev = pcp->p_hprev;
				pcp->p_hprev = delcallb_list;
				delcallb_list = pcp;
			}
			pcp = pcp->p_hnext;
		}
		mutex_exit(&hp->p_hmutex);
	} else {
		pcache_link_t *plinkp;
		pcache_link_t *pheadp;
		kmutex_t *pmtx;

		if (amp == NULL) {
			ASSERT(seg != NULL);
			pheadp = &seg->s_phead;
			pmtx = &seg->s_pmtx;
		} else {
			pheadp = &amp->a_phead;
			pmtx = &amp->a_pmtx;
		}
		mutex_enter(pmtx);
		while ((plinkp = pheadp->p_lnext) != pheadp) {
			pcp = plink2pcache(plinkp);
			ASSERT(!IS_PCP_WIRED(pcp));
			ASSERT(pcp->p_htag0 == htag0);
			hp = pcp->p_hashp;
			mutex_enter(&hp->p_hmutex);
			if (pcp->p_active) {
				mutex_exit(&hp->p_hmutex);
				break;
			}
			ASSERT(plinkp->p_lprev == pheadp);
			pheadp->p_lnext = plinkp->p_lnext;
			plinkp->p_lnext->p_lprev = pheadp;
			pcp->p_hprev->p_hnext = pcp->p_hnext;
			pcp->p_hnext->p_hprev = pcp->p_hprev;
			pcp->p_hprev = delcallb_list;
			delcallb_list = pcp;
			if (hp->p_hnext == (struct seg_pcache *)hp) {
				seg_premove_abuck(hp, 0);
			}
			mutex_exit(&hp->p_hmutex);
		}
		mutex_exit(pmtx);
	}
	while (delcallb_list != NULL) {
		pcp = delcallb_list;
		delcallb_list = pcp->p_hprev;
		ASSERT(!pcp->p_active);
		(void) (*pcp->p_callback)(pcp->p_htag0, pcp->p_addr, pcp->p_len,
		    pcp->p_pp, pcp->p_write ? S_WRITE : S_READ, 0);
		npages += btop(pcp->p_len);
		kmem_cache_free(seg_pkmcache, pcp);
	}
	mutex_enter(&seg_pmem_mtx);
	ASSERT(seg_plocked >= npages);
	seg_plocked -= npages;
	if (!IS_PFLAGS_WIRED(flags)) {
		ASSERT(seg_plocked_window >= npages);
		seg_plocked_window -= npages;
	}
	mutex_exit(&seg_pmem_mtx);
}

static void seg_pinit_mem_config(void);

/*
 * setup the pagelock cache
 */
static void
seg_pinit(void)
{
	struct seg_phash *hp;
	ulong_t i;
	pgcnt_t physmegs;

	seg_plocked = 0;
	seg_plocked_window = 0;

	if (segpcache_enabled == 0) {
		seg_phashsize_win = 0;
		seg_phashsize_wired = 0;
		seg_pdisabled = 1;
		return;
	}

	seg_pdisabled = 0;
	seg_pkmcache = kmem_cache_create("seg_pcache",
	    sizeof (struct seg_pcache), 0, NULL, NULL, NULL, NULL, NULL, 0);
	if (segpcache_pcp_maxage_ticks <= 0) {
		segpcache_pcp_maxage_ticks = segpcache_pcp_maxage_sec * hz;
	}
	seg_pmax_pcpage = segpcache_pcp_maxage_ticks;
	seg_pathr_empty_ahb = 0;
	seg_pathr_full_ahb = 0;
	seg_pshrink_shift = segpcache_shrink_shift;
	seg_pmaxapurge_npages = btop(segpcache_maxapurge_bytes);

	mutex_init(&seg_pcache_mtx, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&seg_pmem_mtx, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&seg_pasync_mtx, NULL, MUTEX_DEFAULT, NULL);
	cv_init(&seg_pasync_cv, NULL, CV_DEFAULT, NULL);

	physmegs = physmem >> (20 - PAGESHIFT);

	/*
	 * If segpcache_hashsize_win was not set in /etc/system or it has
	 * absurd value set it to a default.
	 */
	if (segpcache_hashsize_win == 0 || segpcache_hashsize_win > physmem) {
		/*
		 * Create one bucket per 32K (or at least per 8 pages) of
		 * available memory.
		 */
		pgcnt_t pages_per_bucket = MAX(btop(32 * 1024), 8);
		segpcache_hashsize_win = MAX(1024, physmem / pages_per_bucket);
	}
	if (!ISP2(segpcache_hashsize_win)) {
		ulong_t rndfac = ~(1UL <<
		    (highbit(segpcache_hashsize_win) - 1));
		rndfac &= segpcache_hashsize_win;
		segpcache_hashsize_win += rndfac;
		segpcache_hashsize_win = 1 <<
		    (highbit(segpcache_hashsize_win) - 1);
	}
	seg_phashsize_win = segpcache_hashsize_win;
	seg_phashtab_win = kmem_zalloc(
	    seg_phashsize_win * sizeof (struct seg_phash),
	    KM_SLEEP);
	for (i = 0; i < seg_phashsize_win; i++) {
		hp = &seg_phashtab_win[i];
		hp->p_hnext = (struct seg_pcache *)hp;
		hp->p_hprev = (struct seg_pcache *)hp;
		mutex_init(&hp->p_hmutex, NULL, MUTEX_DEFAULT, NULL);
	}

	seg_pahcur = 0;
	seg_pathr_on = 0;
	seg_pahhead[0].p_lnext = &seg_pahhead[0];
	seg_pahhead[0].p_lprev = &seg_pahhead[0];
	seg_pahhead[1].p_lnext = &seg_pahhead[1];
	seg_pahhead[1].p_lprev = &seg_pahhead[1];

	/*
	 * If segpcache_hashsize_wired was not set in /etc/system or it has
	 * absurd value set it to a default.
	 */
	if (segpcache_hashsize_wired == 0 ||
	    segpcache_hashsize_wired > physmem / 4) {
		/*
		 * Choose segpcache_hashsize_wired based on physmem.
		 * Create a bucket per 128K bytes upto 256K buckets.
		 */
		if (physmegs < 20 * 1024) {
			segpcache_hashsize_wired = MAX(1024, physmegs << 3);
		} else {
			segpcache_hashsize_wired = 256 * 1024;
		}
	}
	if (!ISP2(segpcache_hashsize_wired)) {
		segpcache_hashsize_wired = 1 <<
		    highbit(segpcache_hashsize_wired);
	}
	seg_phashsize_wired = segpcache_hashsize_wired;
	seg_phashtab_wired = kmem_zalloc(
	    seg_phashsize_wired * sizeof (struct seg_phash_wired), KM_SLEEP);
	for (i = 0; i < seg_phashsize_wired; i++) {
		hp = (struct seg_phash *)&seg_phashtab_wired[i];
		hp->p_hnext = (struct seg_pcache *)hp;
		hp->p_hprev = (struct seg_pcache *)hp;
		mutex_init(&hp->p_hmutex, NULL, MUTEX_DEFAULT, NULL);
	}

	if (segpcache_maxwindow == 0) {
		if (physmegs < 64) {
			/* 3% of memory */
			segpcache_maxwindow = availrmem >> 5;
		} else if (physmegs < 512) {
			/* 12% of memory */
			segpcache_maxwindow = availrmem >> 3;
		} else if (physmegs < 1024) {
			/* 25% of memory */
			segpcache_maxwindow = availrmem >> 2;
		} else if (physmegs < 2048) {
			/* 50% of memory */
			segpcache_maxwindow = availrmem >> 1;
		} else {
			/* no limit */
			segpcache_maxwindow = (pgcnt_t)-1;
		}
	}
	seg_pmaxwindow = segpcache_maxwindow;
	seg_pinit_mem_config();
}

/*
 * called by pageout if memory is low
 */
void
seg_preap(void)
{
	/*
	 * if the cache is off or empty, return
	 */
	if (seg_plocked_window == 0) {
		return;
	}
	ASSERT(seg_phashsize_win != 0);

	/*
	 * If somebody is already purging pcache
	 * just return.
	 */
	if (seg_pdisabled) {
		return;
	}

	cv_signal(&seg_pasync_cv);
}

/*
 * run as a backgroud thread and reclaim pagelock
 * pages which have not been used recently
 */
void
seg_pasync_thread(void)
{
	callb_cpr_t cpr_info;

	if (seg_phashsize_win == 0) {
		thread_exit();
		/*NOTREACHED*/
	}

	seg_pasync_thr = curthread;

	CALLB_CPR_INIT(&cpr_info, &seg_pasync_mtx,
	    callb_generic_cpr, "seg_pasync");

	if (segpcache_reap_ticks <= 0) {
		segpcache_reap_ticks = segpcache_reap_sec * hz;
	}

	mutex_enter(&seg_pasync_mtx);
	for (;;) {
		CALLB_CPR_SAFE_BEGIN(&cpr_info);
		(void) cv_timedwait(&seg_pasync_cv, &seg_pasync_mtx,
		    lbolt + segpcache_reap_ticks);
		CALLB_CPR_SAFE_END(&cpr_info, &seg_pasync_mtx);
		if (seg_pdisabled == 0) {
			seg_ppurge_async(0);
		}
	}
}

static struct kmem_cache *seg_cache;

/*
 * Initialize segment management data structures.
 */
void
seg_init(void)
{
	kstat_t *ksp;

	seg_cache = kmem_cache_create("seg_cache", sizeof (struct seg),
	    0, NULL, NULL, NULL, NULL, NULL, 0);

	ksp = kstat_create("unix", 0, "segadvstat", "vm", KSTAT_TYPE_NAMED,
	    segadvstat_ndata, KSTAT_FLAG_VIRTUAL);
	if (ksp) {
		ksp->ks_data = (void *)segadvstat_ptr;
		kstat_install(ksp);
	}

	seg_pinit();
}

/*
 * Allocate a segment to cover [base, base+size]
 * and attach it to the specified address space.
 */
struct seg *
seg_alloc(struct as *as, caddr_t base, size_t size)
{
	struct seg *new;
	caddr_t segbase;
	size_t segsize;

	segbase = (caddr_t)((uintptr_t)base & (uintptr_t)PAGEMASK);
	segsize = (((uintptr_t)(base + size) + PAGEOFFSET) & PAGEMASK) -
	    (uintptr_t)segbase;

	if (!valid_va_range(&segbase, &segsize, segsize, AH_LO))
		return ((struct seg *)NULL);	/* bad virtual addr range */

	if (as != &kas &&
	    valid_usr_range(segbase, segsize, 0, as,
	    as->a_userlimit) != RANGE_OKAY)
		return ((struct seg *)NULL);	/* bad virtual addr range */

	new = kmem_cache_alloc(seg_cache, KM_SLEEP);
	new->s_ops = NULL;
	new->s_data = NULL;
	new->s_szc = 0;
	new->s_flags = 0;
	mutex_init(&new->s_pmtx, NULL, MUTEX_DEFAULT, NULL);
	new->s_phead.p_lnext = &new->s_phead;
	new->s_phead.p_lprev = &new->s_phead;
	if (seg_attach(as, segbase, segsize, new) < 0) {
		kmem_cache_free(seg_cache, new);
		return ((struct seg *)NULL);
	}
	/* caller must fill in ops, data */
	return (new);
}

/*
 * Attach a segment to the address space.  Used by seg_alloc()
 * and for kernel startup to attach to static segments.
 */
int
seg_attach(struct as *as, caddr_t base, size_t size, struct seg *seg)
{
	seg->s_as = as;
	seg->s_base = base;
	seg->s_size = size;

	/*
	 * as_addseg() will add the segment at the appropraite point
	 * in the list. It will return -1 if there is overlap with
	 * an already existing segment.
	 */
	return (as_addseg(as, seg));
}

/*
 * Unmap a segment and free it from its associated address space.
 * This should be called by anybody who's finished with a whole segment's
 * mapping.  Just calls SEGOP_UNMAP() on the whole mapping .  It is the
 * responsibility of the segment driver to unlink the the segment
 * from the address space, and to free public and private data structures
 * associated with the segment.  (This is typically done by a call to
 * seg_free()).
 */
void
seg_unmap(struct seg *seg)
{
#ifdef DEBUG
	int ret;
#endif /* DEBUG */

	ASSERT(seg->s_as && AS_WRITE_HELD(seg->s_as, &seg->s_as->a_lock));

	/* Shouldn't have called seg_unmap if mapping isn't yet established */
	ASSERT(seg->s_data != NULL);

	/* Unmap the whole mapping */
#ifdef DEBUG
	ret = SEGOP_UNMAP(seg, seg->s_base, seg->s_size);
	ASSERT(ret == 0);
#else
	SEGOP_UNMAP(seg, seg->s_base, seg->s_size);
#endif /* DEBUG */
}

/*
 * Free the segment from its associated as. This should only be called
 * if a mapping to the segment has not yet been established (e.g., if
 * an error occurs in the middle of doing an as_map when the segment
 * has already been partially set up) or if it has already been deleted
 * (e.g., from a segment driver unmap routine if the unmap applies to the
 * entire segment). If the mapping is currently set up then seg_unmap() should
 * be called instead.
 */
void
seg_free(struct seg *seg)
{
	register struct as *as = seg->s_as;
	struct seg *tseg = as_removeseg(as, seg);

	ASSERT(tseg == seg);

	/*
	 * If the segment private data field is NULL,
	 * then segment driver is not attached yet.
	 */
	if (seg->s_data != NULL)
		SEGOP_FREE(seg);

	mutex_destroy(&seg->s_pmtx);
	ASSERT(seg->s_phead.p_lnext == &seg->s_phead);
	ASSERT(seg->s_phead.p_lprev == &seg->s_phead);
	kmem_cache_free(seg_cache, seg);
}

/*ARGSUSED*/
static void
seg_p_mem_config_post_add(
	void *arg,
	pgcnt_t delta_pages)
{
	/* Nothing to do. */
}

void
seg_p_enable(void)
{
	mutex_enter(&seg_pcache_mtx);
	ASSERT(seg_pdisabled != 0);
	seg_pdisabled--;
	mutex_exit(&seg_pcache_mtx);
}

/*
 * seg_p_disable - disables seg_pcache, and then attempts to empty the
 * cache.
 * Returns SEGP_SUCCESS if the cache was successfully emptied, or
 * SEGP_FAIL if the cache could not be emptied.
 */
int
seg_p_disable(void)
{
	pgcnt_t	old_plocked;
	int stall_count = 0;

	mutex_enter(&seg_pcache_mtx);
	seg_pdisabled++;
	ASSERT(seg_pdisabled != 0);
	mutex_exit(&seg_pcache_mtx);

	/*
	 * Attempt to empty the cache. Terminate if seg_plocked does not
	 * diminish with SEGP_STALL_THRESHOLD consecutive attempts.
	 */
	while (seg_plocked != 0) {
		ASSERT(seg_phashsize_win != 0);
		old_plocked = seg_plocked;
		seg_ppurge_async(1);
		if (seg_plocked == old_plocked) {
			if (stall_count++ > SEGP_STALL_THRESHOLD) {
				return (SEGP_FAIL);
			}
		} else
			stall_count = 0;
		if (seg_plocked != 0)
			delay(hz/SEGP_PREDEL_DELAY_FACTOR);
	}
	return (SEGP_SUCCESS);
}

/*
 * Attempt to purge seg_pcache.  May need to return before this has
 * completed to allow other pre_del callbacks to unlock pages. This is
 * ok because:
 *	1) The seg_pdisabled flag has been set so at least we won't
 *	cache anymore locks and the locks we couldn't purge
 *	will not be held if they do get released by a subsequent
 *	pre-delete callback.
 *
 *	2) The rest of the memory delete thread processing does not
 *	depend on the changes made in this pre-delete callback. No
 *	panics will result, the worst that will happen is that the
 *	DR code will timeout and cancel the delete.
 */
/*ARGSUSED*/
static int
seg_p_mem_config_pre_del(
	void *arg,
	pgcnt_t delta_pages)
{
	if (seg_phashsize_win == 0) {
		return (0);
	}
	if (seg_p_disable() != SEGP_SUCCESS)
		cmn_err(CE_NOTE,
		    "!Pre-delete couldn't purge"" pagelock cache - continuing");
	return (0);
}

/*ARGSUSED*/
static void
seg_p_mem_config_post_del(
	void *arg,
	pgcnt_t delta_pages,
	int cancelled)
{
	if (seg_phashsize_win == 0) {
		return;
	}
	seg_p_enable();
}

static kphysm_setup_vector_t seg_p_mem_config_vec = {
	KPHYSM_SETUP_VECTOR_VERSION,
	seg_p_mem_config_post_add,
	seg_p_mem_config_pre_del,
	seg_p_mem_config_post_del,
};

static void
seg_pinit_mem_config(void)
{
	int ret;

	ret = kphysm_setup_func_register(&seg_p_mem_config_vec, (void *)NULL);
	/*
	 * Want to catch this in the debug kernel. At run time, if the
	 * callbacks don't get run all will be OK as the disable just makes
	 * it more likely that the pages can be collected.
	 */
	ASSERT(ret == 0);
}

/*
 * Verify that segment is not a shared anonymous segment which reserves
 * swap.  zone.max-swap accounting (zone->zone_max_swap) cannot be transfered
 * from one zone to another if any segments are shared.  This is because the
 * last process to exit will credit the swap reservation.  This could lead
 * to the swap being reserved by one zone, and credited to another.
 */
boolean_t
seg_can_change_zones(struct seg *seg)
{
	struct segvn_data *svd;

	if (seg->s_ops == &segspt_shmops)
		return (B_FALSE);

	if (seg->s_ops == &segvn_ops) {
		svd = (struct segvn_data *)seg->s_data;
		if (svd->type == MAP_SHARED &&
		    svd->amp != NULL &&
		    svd->amp->swresv > 0)
		return (B_FALSE);
	}
	return (B_TRUE);
}

/*
 * Return swap reserved by a segment backing a private mapping.
 */
size_t
seg_swresv(struct seg *seg)
{
	struct segvn_data *svd;
	size_t swap = 0;

	if (seg->s_ops == &segvn_ops) {
		svd = (struct segvn_data *)seg->s_data;
		if (svd->type == MAP_PRIVATE && svd->swresv > 0)
			swap = svd->swresv;
	}
	return (swap);
}