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freebsd-dev/sys/vm/vm_pageout.c
Attilio Rao a15f7df5de The per-page act_count can be made very-easily protected by the 
per-page lock rather than vm_object lock, without any further overhead.
Make the formal switch.

Sponsored by:	EMC / Isilon storage division
Reviewed by:	alc
Tested by:	pho
2013-04-08 20:02:27 +00:00

1926 lines
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/*-
* Copyright (c) 1991 Regents of the University of California.
* All rights reserved.
* Copyright (c) 1994 John S. Dyson
* All rights reserved.
* Copyright (c) 1994 David Greenman
* All rights reserved.
* Copyright (c) 2005 Yahoo! Technologies Norway AS
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* 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 University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
*
* from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
*
*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* All rights reserved.
*
* Authors: Avadis Tevanian, Jr., Michael Wayne Young
*
* Permission to use, copy, modify and distribute this software and
* its documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
/*
* The proverbial page-out daemon.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_vm.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/eventhandler.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/kthread.h>
#include <sys/ktr.h>
#include <sys/mount.h>
#include <sys/racct.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/rwlock.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pager.h>
#include <vm/swap_pager.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
/*
* System initialization
*/
/* the kernel process "vm_pageout"*/
static void vm_pageout(void);
static int vm_pageout_clean(vm_page_t);
static void vm_pageout_scan(int pass);
struct proc *pageproc;
static struct kproc_desc page_kp = {
"pagedaemon",
vm_pageout,
&pageproc
};
SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start,
&page_kp);
#if !defined(NO_SWAPPING)
/* the kernel process "vm_daemon"*/
static void vm_daemon(void);
static struct proc *vmproc;
static struct kproc_desc vm_kp = {
"vmdaemon",
vm_daemon,
&vmproc
};
SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
#endif
int vm_pages_needed; /* Event on which pageout daemon sleeps */
int vm_pageout_deficit; /* Estimated number of pages deficit */
int vm_pageout_pages_needed; /* flag saying that the pageout daemon needs pages */
#if !defined(NO_SWAPPING)
static int vm_pageout_req_swapout; /* XXX */
static int vm_daemon_needed;
static struct mtx vm_daemon_mtx;
/* Allow for use by vm_pageout before vm_daemon is initialized. */
MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
#endif
static int vm_max_launder = 32;
static int vm_pageout_stats_max;
static int vm_pageout_stats;
static int vm_pageout_stats_interval;
static int vm_pageout_full_stats;
static int vm_pageout_full_stats_interval;
static int vm_pageout_algorithm;
static int defer_swap_pageouts;
static int disable_swap_pageouts;
#if defined(NO_SWAPPING)
static int vm_swap_enabled = 0;
static int vm_swap_idle_enabled = 0;
#else
static int vm_swap_enabled = 1;
static int vm_swap_idle_enabled = 0;
#endif
SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm,
CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt");
SYSCTL_INT(_vm, OID_AUTO, max_launder,
CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max,
CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length");
SYSCTL_INT(_vm, OID_AUTO, pageout_stats,
CTLFLAG_RD, &vm_pageout_stats, 0, "Number of partial stats scans");
SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval,
CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan");
SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats,
CTLFLAG_RD, &vm_pageout_full_stats, 0, "Number of full stats scans");
SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval,
CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan");
#if defined(NO_SWAPPING)
SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout");
SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
#else
SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
#endif
SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
static int pageout_lock_miss;
SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
#define VM_PAGEOUT_PAGE_COUNT 16
int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
int vm_page_max_wired; /* XXX max # of wired pages system-wide */
SYSCTL_INT(_vm, OID_AUTO, max_wired,
CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *);
static boolean_t vm_pageout_launder(int, int, vm_paddr_t, vm_paddr_t);
#if !defined(NO_SWAPPING)
static void vm_pageout_map_deactivate_pages(vm_map_t, long);
static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
static void vm_req_vmdaemon(int req);
#endif
static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *);
static void vm_pageout_page_stats(void);
/*
* Initialize a dummy page for marking the caller's place in the specified
* paging queue. In principle, this function only needs to set the flag
* PG_MARKER. Nonetheless, it sets the flag VPO_BUSY and initializes the hold
* count to one as safety precautions.
*/
static void
vm_pageout_init_marker(vm_page_t marker, u_short queue)
{
bzero(marker, sizeof(*marker));
marker->flags = PG_MARKER;
marker->oflags = VPO_BUSY;
marker->queue = queue;
marker->hold_count = 1;
}
/*
* vm_pageout_fallback_object_lock:
*
* Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is
* known to have failed and page queue must be either PQ_ACTIVE or
* PQ_INACTIVE. To avoid lock order violation, unlock the page queues
* while locking the vm object. Use marker page to detect page queue
* changes and maintain notion of next page on page queue. Return
* TRUE if no changes were detected, FALSE otherwise. vm object is
* locked on return.
*
* This function depends on both the lock portion of struct vm_object
* and normal struct vm_page being type stable.
*/
static boolean_t
vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
{
struct vm_page marker;
struct vm_pagequeue *pq;
boolean_t unchanged;
u_short queue;
vm_object_t object;
queue = m->queue;
vm_pageout_init_marker(&marker, queue);
pq = &vm_pagequeues[queue];
object = m->object;
TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, pageq);
vm_pagequeue_unlock(pq);
vm_page_unlock(m);
VM_OBJECT_WLOCK(object);
vm_page_lock(m);
vm_pagequeue_lock(pq);
/* Page queue might have changed. */
*next = TAILQ_NEXT(&marker, pageq);
unchanged = (m->queue == queue &&
m->object == object &&
&marker == TAILQ_NEXT(m, pageq));
TAILQ_REMOVE(&pq->pq_pl, &marker, pageq);
return (unchanged);
}
/*
* Lock the page while holding the page queue lock. Use marker page
* to detect page queue changes and maintain notion of next page on
* page queue. Return TRUE if no changes were detected, FALSE
* otherwise. The page is locked on return. The page queue lock might
* be dropped and reacquired.
*
* This function depends on normal struct vm_page being type stable.
*/
static boolean_t
vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
{
struct vm_page marker;
struct vm_pagequeue *pq;
boolean_t unchanged;
u_short queue;
vm_page_lock_assert(m, MA_NOTOWNED);
if (vm_page_trylock(m))
return (TRUE);
queue = m->queue;
vm_pageout_init_marker(&marker, queue);
pq = &vm_pagequeues[queue];
TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, pageq);
vm_pagequeue_unlock(pq);
vm_page_lock(m);
vm_pagequeue_lock(pq);
/* Page queue might have changed. */
*next = TAILQ_NEXT(&marker, pageq);
unchanged = (m->queue == queue && &marker == TAILQ_NEXT(m, pageq));
TAILQ_REMOVE(&pq->pq_pl, &marker, pageq);
return (unchanged);
}
/*
* vm_pageout_clean:
*
* Clean the page and remove it from the laundry.
*
* We set the busy bit to cause potential page faults on this page to
* block. Note the careful timing, however, the busy bit isn't set till
* late and we cannot do anything that will mess with the page.
*/
static int
vm_pageout_clean(vm_page_t m)
{
vm_object_t object;
vm_page_t mc[2*vm_pageout_page_count], pb, ps;
int pageout_count;
int ib, is, page_base;
vm_pindex_t pindex = m->pindex;
vm_page_lock_assert(m, MA_OWNED);
object = m->object;
VM_OBJECT_ASSERT_WLOCKED(object);
/*
* It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
* with the new swapper, but we could have serious problems paging
* out other object types if there is insufficient memory.
*
* Unfortunately, checking free memory here is far too late, so the
* check has been moved up a procedural level.
*/
/*
* Can't clean the page if it's busy or held.
*/
KASSERT(m->busy == 0 && (m->oflags & VPO_BUSY) == 0,
("vm_pageout_clean: page %p is busy", m));
KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m));
vm_page_unlock(m);
mc[vm_pageout_page_count] = pb = ps = m;
pageout_count = 1;
page_base = vm_pageout_page_count;
ib = 1;
is = 1;
/*
* Scan object for clusterable pages.
*
* We can cluster ONLY if: ->> the page is NOT
* clean, wired, busy, held, or mapped into a
* buffer, and one of the following:
* 1) The page is inactive, or a seldom used
* active page.
* -or-
* 2) we force the issue.
*
* During heavy mmap/modification loads the pageout
* daemon can really fragment the underlying file
* due to flushing pages out of order and not trying
* align the clusters (which leave sporatic out-of-order
* holes). To solve this problem we do the reverse scan
* first and attempt to align our cluster, then do a
* forward scan if room remains.
*/
more:
while (ib && pageout_count < vm_pageout_page_count) {
vm_page_t p;
if (ib > pindex) {
ib = 0;
break;
}
if ((p = vm_page_prev(pb)) == NULL ||
(p->oflags & VPO_BUSY) != 0 || p->busy != 0) {
ib = 0;
break;
}
vm_page_lock(p);
vm_page_test_dirty(p);
if (p->dirty == 0 ||
p->queue != PQ_INACTIVE ||
p->hold_count != 0) { /* may be undergoing I/O */
vm_page_unlock(p);
ib = 0;
break;
}
vm_page_unlock(p);
mc[--page_base] = pb = p;
++pageout_count;
++ib;
/*
* alignment boundry, stop here and switch directions. Do
* not clear ib.
*/
if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
break;
}
while (pageout_count < vm_pageout_page_count &&
pindex + is < object->size) {
vm_page_t p;
if ((p = vm_page_next(ps)) == NULL ||
(p->oflags & VPO_BUSY) != 0 || p->busy != 0)
break;
vm_page_lock(p);
vm_page_test_dirty(p);
if (p->dirty == 0 ||
p->queue != PQ_INACTIVE ||
p->hold_count != 0) { /* may be undergoing I/O */
vm_page_unlock(p);
break;
}
vm_page_unlock(p);
mc[page_base + pageout_count] = ps = p;
++pageout_count;
++is;
}
/*
* If we exhausted our forward scan, continue with the reverse scan
* when possible, even past a page boundry. This catches boundry
* conditions.
*/
if (ib && pageout_count < vm_pageout_page_count)
goto more;
/*
* we allow reads during pageouts...
*/
return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL,
NULL));
}
/*
* vm_pageout_flush() - launder the given pages
*
* The given pages are laundered. Note that we setup for the start of
* I/O ( i.e. busy the page ), mark it read-only, and bump the object
* reference count all in here rather then in the parent. If we want
* the parent to do more sophisticated things we may have to change
* the ordering.
*
* Returned runlen is the count of pages between mreq and first
* page after mreq with status VM_PAGER_AGAIN.
* *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
* for any page in runlen set.
*/
int
vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
boolean_t *eio)
{
vm_object_t object = mc[0]->object;
int pageout_status[count];
int numpagedout = 0;
int i, runlen;
VM_OBJECT_ASSERT_WLOCKED(object);
/*
* Initiate I/O. Bump the vm_page_t->busy counter and
* mark the pages read-only.
*
* We do not have to fixup the clean/dirty bits here... we can
* allow the pager to do it after the I/O completes.
*
* NOTE! mc[i]->dirty may be partial or fragmented due to an
* edge case with file fragments.
*/
for (i = 0; i < count; i++) {
KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
("vm_pageout_flush: partially invalid page %p index %d/%d",
mc[i], i, count));
vm_page_io_start(mc[i]);
pmap_remove_write(mc[i]);
}
vm_object_pip_add(object, count);
vm_pager_put_pages(object, mc, count, flags, pageout_status);
runlen = count - mreq;
if (eio != NULL)
*eio = FALSE;
for (i = 0; i < count; i++) {
vm_page_t mt = mc[i];
KASSERT(pageout_status[i] == VM_PAGER_PEND ||
!pmap_page_is_write_mapped(mt),
("vm_pageout_flush: page %p is not write protected", mt));
switch (pageout_status[i]) {
case VM_PAGER_OK:
case VM_PAGER_PEND:
numpagedout++;
break;
case VM_PAGER_BAD:
/*
* Page outside of range of object. Right now we
* essentially lose the changes by pretending it
* worked.
*/
vm_page_undirty(mt);
break;
case VM_PAGER_ERROR:
case VM_PAGER_FAIL:
/*
* If page couldn't be paged out, then reactivate the
* page so it doesn't clog the inactive list. (We
* will try paging out it again later).
*/
vm_page_lock(mt);
vm_page_activate(mt);
vm_page_unlock(mt);
if (eio != NULL && i >= mreq && i - mreq < runlen)
*eio = TRUE;
break;
case VM_PAGER_AGAIN:
if (i >= mreq && i - mreq < runlen)
runlen = i - mreq;
break;
}
/*
* If the operation is still going, leave the page busy to
* block all other accesses. Also, leave the paging in
* progress indicator set so that we don't attempt an object
* collapse.
*/
if (pageout_status[i] != VM_PAGER_PEND) {
vm_object_pip_wakeup(object);
vm_page_io_finish(mt);
if (vm_page_count_severe()) {
vm_page_lock(mt);
vm_page_try_to_cache(mt);
vm_page_unlock(mt);
}
}
}
if (prunlen != NULL)
*prunlen = runlen;
return (numpagedout);
}
static boolean_t
vm_pageout_launder(int queue, int tries, vm_paddr_t low, vm_paddr_t high)
{
struct mount *mp;
struct vm_pagequeue *pq;
struct vnode *vp;
vm_object_t object;
vm_paddr_t pa;
vm_page_t m, m_tmp, next;
pq = &vm_pagequeues[queue];
vm_pagequeue_lock(pq);
TAILQ_FOREACH_SAFE(m, &pq->pq_pl, pageq, next) {
KASSERT(m->queue == queue,
("vm_pageout_launder: page %p's queue is not %d", m,
queue));
if ((m->flags & PG_MARKER) != 0)
continue;
pa = VM_PAGE_TO_PHYS(m);
if (pa < low || pa + PAGE_SIZE > high)
continue;
if (!vm_pageout_page_lock(m, &next) || m->hold_count != 0) {
vm_page_unlock(m);
continue;
}
object = m->object;
if ((!VM_OBJECT_TRYWLOCK(object) &&
(!vm_pageout_fallback_object_lock(m, &next) ||
m->hold_count != 0)) || (m->oflags & VPO_BUSY) != 0 ||
m->busy != 0) {
vm_page_unlock(m);
VM_OBJECT_WUNLOCK(object);
continue;
}
vm_page_test_dirty(m);
if (m->dirty == 0 && object->ref_count != 0)
pmap_remove_all(m);
if (m->dirty != 0) {
vm_page_unlock(m);
if (tries == 0 || (object->flags & OBJ_DEAD) != 0) {
VM_OBJECT_WUNLOCK(object);
continue;
}
if (object->type == OBJT_VNODE) {
vm_pagequeue_unlock(pq);
vp = object->handle;
vm_object_reference_locked(object);
VM_OBJECT_WUNLOCK(object);
(void)vn_start_write(vp, &mp, V_WAIT);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
VM_OBJECT_WLOCK(object);
vm_object_page_clean(object, 0, 0, OBJPC_SYNC);
VM_OBJECT_WUNLOCK(object);
VOP_UNLOCK(vp, 0);
vm_object_deallocate(object);
vn_finished_write(mp);
return (TRUE);
} else if (object->type == OBJT_SWAP ||
object->type == OBJT_DEFAULT) {
vm_pagequeue_unlock(pq);
m_tmp = m;
vm_pageout_flush(&m_tmp, 1, VM_PAGER_PUT_SYNC,
0, NULL, NULL);
VM_OBJECT_WUNLOCK(object);
return (TRUE);
}
} else {
/*
* Dequeue here to prevent lock recursion in
* vm_page_cache().
*/
vm_page_dequeue_locked(m);
vm_page_cache(m);
vm_page_unlock(m);
}
VM_OBJECT_WUNLOCK(object);
}
vm_pagequeue_unlock(pq);
return (FALSE);
}
/*
* Increase the number of cached pages. The specified value, "tries",
* determines which categories of pages are cached:
*
* 0: All clean, inactive pages within the specified physical address range
* are cached. Will not sleep.
* 1: The vm_lowmem handlers are called. All inactive pages within
* the specified physical address range are cached. May sleep.
* 2: The vm_lowmem handlers are called. All inactive and active pages
* within the specified physical address range are cached. May sleep.
*/
void
vm_pageout_grow_cache(int tries, vm_paddr_t low, vm_paddr_t high)
{
int actl, actmax, inactl, inactmax;
if (tries > 0) {
/*
* Decrease registered cache sizes. The vm_lowmem handlers
* may acquire locks and/or sleep, so they can only be invoked
* when "tries" is greater than zero.
*/
EVENTHANDLER_INVOKE(vm_lowmem, 0);
/*
* We do this explicitly after the caches have been drained
* above.
*/
uma_reclaim();
}
inactl = 0;
inactmax = cnt.v_inactive_count;
actl = 0;
actmax = tries < 2 ? 0 : cnt.v_active_count;
again:
if (inactl < inactmax && vm_pageout_launder(PQ_INACTIVE, tries, low,
high)) {
inactl++;
goto again;
}
if (actl < actmax && vm_pageout_launder(PQ_ACTIVE, tries, low, high)) {
actl++;
goto again;
}
}
#if !defined(NO_SWAPPING)
/*
* vm_pageout_object_deactivate_pages
*
* Deactivate enough pages to satisfy the inactive target
* requirements.
*
* The object and map must be locked.
*/
static void
vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
long desired)
{
vm_object_t backing_object, object;
vm_page_t p;
int actcount, remove_mode;
VM_OBJECT_ASSERT_WLOCKED(first_object);
if ((first_object->flags & OBJ_FICTITIOUS) != 0)
return;
for (object = first_object;; object = backing_object) {
if (pmap_resident_count(pmap) <= desired)
goto unlock_return;
VM_OBJECT_ASSERT_WLOCKED(object);
if ((object->flags & OBJ_UNMANAGED) != 0 ||
object->paging_in_progress != 0)
goto unlock_return;
remove_mode = 0;
if (object->shadow_count > 1)
remove_mode = 1;
/*
* Scan the object's entire memory queue.
*/
TAILQ_FOREACH(p, &object->memq, listq) {
if (pmap_resident_count(pmap) <= desired)
goto unlock_return;
if ((p->oflags & VPO_BUSY) != 0 || p->busy != 0)
continue;
PCPU_INC(cnt.v_pdpages);
vm_page_lock(p);
if (p->wire_count != 0 || p->hold_count != 0 ||
!pmap_page_exists_quick(pmap, p)) {
vm_page_unlock(p);
continue;
}
actcount = pmap_ts_referenced(p);
if ((p->aflags & PGA_REFERENCED) != 0) {
if (actcount == 0)
actcount = 1;
vm_page_aflag_clear(p, PGA_REFERENCED);
}
if (p->queue != PQ_ACTIVE && actcount != 0) {
vm_page_activate(p);
p->act_count += actcount;
} else if (p->queue == PQ_ACTIVE) {
if (actcount == 0) {
p->act_count -= min(p->act_count,
ACT_DECLINE);
if (!remove_mode &&
(vm_pageout_algorithm ||
p->act_count == 0)) {
pmap_remove_all(p);
vm_page_deactivate(p);
} else
vm_page_requeue(p);
} else {
vm_page_activate(p);
if (p->act_count < ACT_MAX -
ACT_ADVANCE)
p->act_count += ACT_ADVANCE;
vm_page_requeue(p);
}
} else if (p->queue == PQ_INACTIVE)
pmap_remove_all(p);
vm_page_unlock(p);
}
if ((backing_object = object->backing_object) == NULL)
goto unlock_return;
VM_OBJECT_WLOCK(backing_object);
if (object != first_object)
VM_OBJECT_WUNLOCK(object);
}
unlock_return:
if (object != first_object)
VM_OBJECT_WUNLOCK(object);
}
/*
* deactivate some number of pages in a map, try to do it fairly, but
* that is really hard to do.
*/
static void
vm_pageout_map_deactivate_pages(map, desired)
vm_map_t map;
long desired;
{
vm_map_entry_t tmpe;
vm_object_t obj, bigobj;
int nothingwired;
if (!vm_map_trylock(map))
return;
bigobj = NULL;
nothingwired = TRUE;
/*
* first, search out the biggest object, and try to free pages from
* that.
*/
tmpe = map->header.next;
while (tmpe != &map->header) {
if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
obj = tmpe->object.vm_object;
if (obj != NULL && VM_OBJECT_TRYWLOCK(obj)) {
if (obj->shadow_count <= 1 &&
(bigobj == NULL ||
bigobj->resident_page_count < obj->resident_page_count)) {
if (bigobj != NULL)
VM_OBJECT_WUNLOCK(bigobj);
bigobj = obj;
} else
VM_OBJECT_WUNLOCK(obj);
}
}
if (tmpe->wired_count > 0)
nothingwired = FALSE;
tmpe = tmpe->next;
}
if (bigobj != NULL) {
vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
VM_OBJECT_WUNLOCK(bigobj);
}
/*
* Next, hunt around for other pages to deactivate. We actually
* do this search sort of wrong -- .text first is not the best idea.
*/
tmpe = map->header.next;
while (tmpe != &map->header) {
if (pmap_resident_count(vm_map_pmap(map)) <= desired)
break;
if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
obj = tmpe->object.vm_object;
if (obj != NULL) {
VM_OBJECT_WLOCK(obj);
vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
VM_OBJECT_WUNLOCK(obj);
}
}
tmpe = tmpe->next;
}
/*
* Remove all mappings if a process is swapped out, this will free page
* table pages.
*/
if (desired == 0 && nothingwired) {
pmap_remove(vm_map_pmap(map), vm_map_min(map),
vm_map_max(map));
}
vm_map_unlock(map);
}
#endif /* !defined(NO_SWAPPING) */
/*
* vm_pageout_scan does the dirty work for the pageout daemon.
*/
static void
vm_pageout_scan(int pass)
{
vm_page_t m, next;
struct vm_page marker;
struct vm_pagequeue *pq;
int page_shortage, maxscan, pcount;
int addl_page_shortage;
vm_object_t object;
int actcount;
int vnodes_skipped = 0;
int maxlaunder;
boolean_t queues_locked;
vm_pageout_init_marker(&marker, PQ_INACTIVE);
/*
* Decrease registered cache sizes.
*/
EVENTHANDLER_INVOKE(vm_lowmem, 0);
/*
* We do this explicitly after the caches have been drained above.
*/
uma_reclaim();
/*
* The addl_page_shortage is the number of temporarily
* stuck pages in the inactive queue. In other words, the
* number of pages from cnt.v_inactive_count that should be
* discounted in setting the target for the active queue scan.
*/
addl_page_shortage = atomic_readandclear_int(&vm_pageout_deficit);
/*
* Calculate the number of pages we want to either free or move
* to the cache.
*/
page_shortage = vm_paging_target() + addl_page_shortage;
/*
* maxlaunder limits the number of dirty pages we flush per scan.
* For most systems a smaller value (16 or 32) is more robust under
* extreme memory and disk pressure because any unnecessary writes
* to disk can result in extreme performance degredation. However,
* systems with excessive dirty pages (especially when MAP_NOSYNC is
* used) will die horribly with limited laundering. If the pageout
* daemon cannot clean enough pages in the first pass, we let it go
* all out in succeeding passes.
*/
if ((maxlaunder = vm_max_launder) <= 1)
maxlaunder = 1;
if (pass)
maxlaunder = 10000;
maxscan = cnt.v_inactive_count;
/*
* Start scanning the inactive queue for pages we can move to the
* cache or free. The scan will stop when the target is reached or
* we have scanned the entire inactive queue. Note that m->act_count
* is not used to form decisions for the inactive queue, only for the
* active queue.
*/
pq = &vm_pagequeues[PQ_INACTIVE];
vm_pagequeue_lock(pq);
queues_locked = TRUE;
for (m = TAILQ_FIRST(&pq->pq_pl);
m != NULL && maxscan-- > 0 && page_shortage > 0;
m = next) {
vm_pagequeue_assert_locked(pq);
KASSERT(queues_locked, ("unlocked queues"));
KASSERT(m->queue == PQ_INACTIVE, ("Inactive queue %p", m));
PCPU_INC(cnt.v_pdpages);
next = TAILQ_NEXT(m, pageq);
/*
* skip marker pages
*/
if (m->flags & PG_MARKER)
continue;
KASSERT((m->flags & PG_FICTITIOUS) == 0,
("Fictitious page %p cannot be in inactive queue", m));
KASSERT((m->oflags & VPO_UNMANAGED) == 0,
("Unmanaged page %p cannot be in inactive queue", m));
/*
* The page or object lock acquisitions fail if the
* page was removed from the queue or moved to a
* different position within the queue. In either
* case, addl_page_shortage should not be incremented.
*/
if (!vm_pageout_page_lock(m, &next)) {
vm_page_unlock(m);
continue;
}
object = m->object;
if (!VM_OBJECT_TRYWLOCK(object) &&
!vm_pageout_fallback_object_lock(m, &next)) {
vm_page_unlock(m);
VM_OBJECT_WUNLOCK(object);
continue;
}
/*
* Don't mess with busy pages, keep them at at the
* front of the queue, most likely they are being
* paged out. Increment addl_page_shortage for busy
* pages, because they may leave the inactive queue
* shortly after page scan is finished.
*/
if (m->busy != 0 || (m->oflags & VPO_BUSY) != 0) {
vm_page_unlock(m);
VM_OBJECT_WUNLOCK(object);
addl_page_shortage++;
continue;
}
/*
* We unlock the inactive page queue, invalidating the
* 'next' pointer. Use our marker to remember our
* place.
*/
TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, pageq);
vm_pagequeue_unlock(pq);
queues_locked = FALSE;
/*
* If the object is not being used, we ignore previous
* references.
*/
if (object->ref_count == 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
KASSERT(!pmap_page_is_mapped(m),
("vm_pageout_scan: page %p is mapped", m));
/*
* Otherwise, if the page has been referenced while in the
* inactive queue, we bump the "activation count" upwards,
* making it less likely that the page will be added back to
* the inactive queue prematurely again. Here we check the
* page tables (or emulated bits, if any), given the upper
* level VM system not knowing anything about existing
* references.
*/
} else if ((m->aflags & PGA_REFERENCED) == 0 &&
(actcount = pmap_ts_referenced(m)) != 0) {
vm_page_activate(m);
VM_OBJECT_WUNLOCK(object);
m->act_count += actcount + ACT_ADVANCE;
vm_page_unlock(m);
goto relock_queues;
}
/*
* If the upper level VM system knows about any page
* references, we activate the page. We also set the
* "activation count" higher than normal so that we will less
* likely place pages back onto the inactive queue again.
*/
if ((m->aflags & PGA_REFERENCED) != 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
actcount = pmap_ts_referenced(m);
vm_page_activate(m);
VM_OBJECT_WUNLOCK(object);
m->act_count += actcount + ACT_ADVANCE + 1;
vm_page_unlock(m);
goto relock_queues;
}
if (m->hold_count != 0) {
vm_page_unlock(m);
VM_OBJECT_WUNLOCK(object);
/*
* Held pages are essentially stuck in the
* queue. So, they ought to be discounted
* from cnt.v_inactive_count. See the
* calculation of the page_shortage for the
* loop over the active queue below.
*/
addl_page_shortage++;
goto relock_queues;
}
/*
* If the page appears to be clean at the machine-independent
* layer, then remove all of its mappings from the pmap in
* anticipation of placing it onto the cache queue. If,
* however, any of the page's mappings allow write access,
* then the page may still be modified until the last of those
* mappings are removed.
*/
vm_page_test_dirty(m);
if (m->dirty == 0 && object->ref_count != 0)
pmap_remove_all(m);
if (m->valid == 0) {
/*
* Invalid pages can be easily freed
*/
vm_page_free(m);
PCPU_INC(cnt.v_dfree);
--page_shortage;
} else if (m->dirty == 0) {
/*
* Clean pages can be placed onto the cache queue.
* This effectively frees them.
*/
vm_page_cache(m);
--page_shortage;
} else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) {
/*
* Dirty pages need to be paged out, but flushing
* a page is extremely expensive verses freeing
* a clean page. Rather then artificially limiting
* the number of pages we can flush, we instead give
* dirty pages extra priority on the inactive queue
* by forcing them to be cycled through the queue
* twice before being flushed, after which the
* (now clean) page will cycle through once more
* before being freed. This significantly extends
* the thrash point for a heavily loaded machine.
*/
m->flags |= PG_WINATCFLS;
vm_pagequeue_lock(pq);
queues_locked = TRUE;
vm_page_requeue_locked(m);
} else if (maxlaunder > 0) {
/*
* We always want to try to flush some dirty pages if
* we encounter them, to keep the system stable.
* Normally this number is small, but under extreme
* pressure where there are insufficient clean pages
* on the inactive queue, we may have to go all out.
*/
int swap_pageouts_ok;
struct vnode *vp = NULL;
struct mount *mp = NULL;
if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
swap_pageouts_ok = 1;
} else {
swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
vm_page_count_min());
}
/*
* We don't bother paging objects that are "dead".
* Those objects are in a "rundown" state.
*/
if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
vm_pagequeue_lock(pq);
vm_page_unlock(m);
VM_OBJECT_WUNLOCK(object);
queues_locked = TRUE;
vm_page_requeue_locked(m);
goto relock_queues;
}
/*
* The object is already known NOT to be dead. It
* is possible for the vget() to block the whole
* pageout daemon, but the new low-memory handling
* code should prevent it.
*
* The previous code skipped locked vnodes and, worse,
* reordered pages in the queue. This results in
* completely non-deterministic operation and, on a
* busy system, can lead to extremely non-optimal
* pageouts. For example, it can cause clean pages
* to be freed and dirty pages to be moved to the end
* of the queue. Since dirty pages are also moved to
* the end of the queue once-cleaned, this gives
* way too large a weighting to defering the freeing
* of dirty pages.
*
* We can't wait forever for the vnode lock, we might
* deadlock due to a vn_read() getting stuck in
* vm_wait while holding this vnode. We skip the
* vnode if we can't get it in a reasonable amount
* of time.
*/
if (object->type == OBJT_VNODE) {
vm_page_unlock(m);
vp = object->handle;
if (vp->v_type == VREG &&
vn_start_write(vp, &mp, V_NOWAIT) != 0) {
mp = NULL;
++pageout_lock_miss;
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
goto unlock_and_continue;
}
KASSERT(mp != NULL,
("vp %p with NULL v_mount", vp));
vm_object_reference_locked(object);
VM_OBJECT_WUNLOCK(object);
if (vget(vp, LK_EXCLUSIVE | LK_TIMELOCK,
curthread)) {
VM_OBJECT_WLOCK(object);
++pageout_lock_miss;
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
vp = NULL;
goto unlock_and_continue;
}
VM_OBJECT_WLOCK(object);
vm_page_lock(m);
vm_pagequeue_lock(pq);
queues_locked = TRUE;
/*
* The page might have been moved to another
* queue during potential blocking in vget()
* above. The page might have been freed and
* reused for another vnode.
*/
if (m->queue != PQ_INACTIVE ||
m->object != object ||
TAILQ_NEXT(m, pageq) != &marker) {
vm_page_unlock(m);
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
goto unlock_and_continue;
}
/*
* The page may have been busied during the
* blocking in vget(). We don't move the
* page back onto the end of the queue so that
* statistics are more correct if we don't.
*/
if (m->busy || (m->oflags & VPO_BUSY)) {
vm_page_unlock(m);
goto unlock_and_continue;
}
/*
* If the page has become held it might
* be undergoing I/O, so skip it
*/
if (m->hold_count) {
vm_page_unlock(m);
vm_page_requeue_locked(m);
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
goto unlock_and_continue;
}
vm_pagequeue_unlock(pq);
queues_locked = FALSE;
}
/*
* If a page is dirty, then it is either being washed
* (but not yet cleaned) or it is still in the
* laundry. If it is still in the laundry, then we
* start the cleaning operation.
*
* decrement page_shortage on success to account for
* the (future) cleaned page. Otherwise we could wind
* up laundering or cleaning too many pages.
*/
if (vm_pageout_clean(m) != 0) {
--page_shortage;
--maxlaunder;
}
unlock_and_continue:
vm_page_lock_assert(m, MA_NOTOWNED);
VM_OBJECT_WUNLOCK(object);
if (mp != NULL) {
if (queues_locked) {
vm_pagequeue_unlock(pq);
queues_locked = FALSE;
}
if (vp != NULL)
vput(vp);
vm_object_deallocate(object);
vn_finished_write(mp);
}
vm_page_lock_assert(m, MA_NOTOWNED);
goto relock_queues;
}
vm_page_unlock(m);
VM_OBJECT_WUNLOCK(object);
relock_queues:
if (!queues_locked) {
vm_pagequeue_lock(pq);
queues_locked = TRUE;
}
next = TAILQ_NEXT(&marker, pageq);
TAILQ_REMOVE(&pq->pq_pl, &marker, pageq);
}
vm_pagequeue_unlock(pq);
/*
* Compute the number of pages we want to try to move from the
* active queue to the inactive queue.
*/
page_shortage = vm_paging_target() +
cnt.v_inactive_target - cnt.v_inactive_count;
page_shortage += addl_page_shortage;
/*
* Scan the active queue for things we can deactivate. We nominally
* track the per-page activity counter and use it to locate
* deactivation candidates.
*/
pcount = cnt.v_active_count;
pq = &vm_pagequeues[PQ_ACTIVE];
vm_pagequeue_lock(pq);
m = TAILQ_FIRST(&pq->pq_pl);
while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) {
KASSERT(m->queue == PQ_ACTIVE,
("vm_pageout_scan: page %p isn't active", m));
next = TAILQ_NEXT(m, pageq);
if ((m->flags & PG_MARKER) != 0) {
m = next;
continue;
}
KASSERT((m->flags & PG_FICTITIOUS) == 0,
("Fictitious page %p cannot be in active queue", m));
KASSERT((m->oflags & VPO_UNMANAGED) == 0,
("Unmanaged page %p cannot be in active queue", m));
if (!vm_pageout_page_lock(m, &next)) {
vm_page_unlock(m);
m = next;
continue;
}
object = m->object;
if (!VM_OBJECT_TRYWLOCK(object) &&
!vm_pageout_fallback_object_lock(m, &next)) {
VM_OBJECT_WUNLOCK(object);
vm_page_unlock(m);
m = next;
continue;
}
/*
* Don't deactivate pages that are busy.
*/
if ((m->busy != 0) ||
(m->oflags & VPO_BUSY) ||
(m->hold_count != 0)) {
vm_page_unlock(m);
VM_OBJECT_WUNLOCK(object);
vm_page_requeue_locked(m);
m = next;
continue;
}
/*
* The count for pagedaemon pages is done after checking the
* page for eligibility...
*/
PCPU_INC(cnt.v_pdpages);
/*
* Check to see "how much" the page has been used.
*/
actcount = 0;
if (object->ref_count != 0) {
if (m->aflags & PGA_REFERENCED) {
actcount += 1;
}
actcount += pmap_ts_referenced(m);
if (actcount) {
m->act_count += ACT_ADVANCE + actcount;
if (m->act_count > ACT_MAX)
m->act_count = ACT_MAX;
}
}
/*
* Since we have "tested" this bit, we need to clear it now.
*/
vm_page_aflag_clear(m, PGA_REFERENCED);
/*
* Only if an object is currently being used, do we use the
* page activation count stats.
*/
if (actcount != 0 && object->ref_count != 0)
vm_page_requeue_locked(m);
else {
m->act_count -= min(m->act_count, ACT_DECLINE);
if (vm_pageout_algorithm ||
object->ref_count == 0 ||
m->act_count == 0) {
page_shortage--;
/* Dequeue to avoid later lock recursion. */
vm_page_dequeue_locked(m);
if (object->ref_count == 0) {
KASSERT(!pmap_page_is_mapped(m),
("vm_pageout_scan: page %p is mapped", m));
if (m->dirty == 0)
vm_page_cache(m);
else
vm_page_deactivate(m);
} else {
vm_page_deactivate(m);
}
} else
vm_page_requeue_locked(m);
}
vm_page_unlock(m);
VM_OBJECT_WUNLOCK(object);
m = next;
}
vm_pagequeue_unlock(pq);
#if !defined(NO_SWAPPING)
/*
* Idle process swapout -- run once per second.
*/
if (vm_swap_idle_enabled) {
static long lsec;
if (time_second != lsec) {
vm_req_vmdaemon(VM_SWAP_IDLE);
lsec = time_second;
}
}
#endif
/*
* If we didn't get enough free pages, and we have skipped a vnode
* in a writeable object, wakeup the sync daemon. And kick swapout
* if we did not get enough free pages.
*/
if (vm_paging_target() > 0) {
if (vnodes_skipped && vm_page_count_min())
(void) speedup_syncer();
#if !defined(NO_SWAPPING)
if (vm_swap_enabled && vm_page_count_target())
vm_req_vmdaemon(VM_SWAP_NORMAL);
#endif
}
/*
* If we are critically low on one of RAM or swap and low on
* the other, kill the largest process. However, we avoid
* doing this on the first pass in order to give ourselves a
* chance to flush out dirty vnode-backed pages and to allow
* active pages to be moved to the inactive queue and reclaimed.
*/
if (pass != 0 &&
((swap_pager_avail < 64 && vm_page_count_min()) ||
(swap_pager_full && vm_paging_target() > 0)))
vm_pageout_oom(VM_OOM_MEM);
}
void
vm_pageout_oom(int shortage)
{
struct proc *p, *bigproc;
vm_offset_t size, bigsize;
struct thread *td;
struct vmspace *vm;
/*
* We keep the process bigproc locked once we find it to keep anyone
* from messing with it; however, there is a possibility of
* deadlock if process B is bigproc and one of it's child processes
* attempts to propagate a signal to B while we are waiting for A's
* lock while walking this list. To avoid this, we don't block on
* the process lock but just skip a process if it is already locked.
*/
bigproc = NULL;
bigsize = 0;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
int breakout;
if (PROC_TRYLOCK(p) == 0)
continue;
/*
* If this is a system, protected or killed process, skip it.
*/
if (p->p_state != PRS_NORMAL ||
(p->p_flag & (P_INEXEC | P_PROTECTED | P_SYSTEM)) ||
(p->p_pid == 1) || P_KILLED(p) ||
((p->p_pid < 48) && (swap_pager_avail != 0))) {
PROC_UNLOCK(p);
continue;
}
/*
* If the process is in a non-running type state,
* don't touch it. Check all the threads individually.
*/
breakout = 0;
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (!TD_ON_RUNQ(td) &&
!TD_IS_RUNNING(td) &&
!TD_IS_SLEEPING(td) &&
!TD_IS_SUSPENDED(td)) {
thread_unlock(td);
breakout = 1;
break;
}
thread_unlock(td);
}
if (breakout) {
PROC_UNLOCK(p);
continue;
}
/*
* get the process size
*/
vm = vmspace_acquire_ref(p);
if (vm == NULL) {
PROC_UNLOCK(p);
continue;
}
if (!vm_map_trylock_read(&vm->vm_map)) {
vmspace_free(vm);
PROC_UNLOCK(p);
continue;
}
size = vmspace_swap_count(vm);
vm_map_unlock_read(&vm->vm_map);
if (shortage == VM_OOM_MEM)
size += vmspace_resident_count(vm);
vmspace_free(vm);
/*
* if the this process is bigger than the biggest one
* remember it.
*/
if (size > bigsize) {
if (bigproc != NULL)
PROC_UNLOCK(bigproc);
bigproc = p;
bigsize = size;
} else
PROC_UNLOCK(p);
}
sx_sunlock(&allproc_lock);
if (bigproc != NULL) {
killproc(bigproc, "out of swap space");
sched_nice(bigproc, PRIO_MIN);
PROC_UNLOCK(bigproc);
wakeup(&cnt.v_free_count);
}
}
/*
* This routine tries to maintain the pseudo LRU active queue,
* so that during long periods of time where there is no paging,
* that some statistic accumulation still occurs. This code
* helps the situation where paging just starts to occur.
*/
static void
vm_pageout_page_stats(void)
{
struct vm_pagequeue *pq;
vm_object_t object;
vm_page_t m, next;
int pcount, tpcount; /* Number of pages to check */
static int fullintervalcount = 0;
int page_shortage;
page_shortage =
(cnt.v_inactive_target + cnt.v_cache_max + cnt.v_free_min) -
(cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
if (page_shortage <= 0)
return;
pcount = cnt.v_active_count;
fullintervalcount += vm_pageout_stats_interval;
if (fullintervalcount < vm_pageout_full_stats_interval) {
vm_pageout_stats++;
tpcount = (int64_t)vm_pageout_stats_max * cnt.v_active_count /
cnt.v_page_count;
if (pcount > tpcount)
pcount = tpcount;
} else {
vm_pageout_full_stats++;
fullintervalcount = 0;
}
pq = &vm_pagequeues[PQ_ACTIVE];
vm_pagequeue_lock(pq);
m = TAILQ_FIRST(&pq->pq_pl);
while ((m != NULL) && (pcount-- > 0)) {
int actcount;
KASSERT(m->queue == PQ_ACTIVE,
("vm_pageout_page_stats: page %p isn't active", m));
next = TAILQ_NEXT(m, pageq);
if ((m->flags & PG_MARKER) != 0) {
m = next;
continue;
}
vm_page_lock_assert(m, MA_NOTOWNED);
if (!vm_pageout_page_lock(m, &next)) {
vm_page_unlock(m);
m = next;
continue;
}
object = m->object;
if (!VM_OBJECT_TRYWLOCK(object) &&
!vm_pageout_fallback_object_lock(m, &next)) {
VM_OBJECT_WUNLOCK(object);
vm_page_unlock(m);
m = next;
continue;
}
/*
* Don't deactivate pages that are busy.
*/
if ((m->busy != 0) ||
(m->oflags & VPO_BUSY) ||
(m->hold_count != 0)) {
vm_page_unlock(m);
VM_OBJECT_WUNLOCK(object);
vm_page_requeue_locked(m);
m = next;
continue;
}
actcount = 0;
if (m->aflags & PGA_REFERENCED) {
vm_page_aflag_clear(m, PGA_REFERENCED);
actcount += 1;
}
actcount += pmap_ts_referenced(m);
if (actcount) {
m->act_count += ACT_ADVANCE + actcount;
if (m->act_count > ACT_MAX)
m->act_count = ACT_MAX;
vm_page_requeue_locked(m);
} else {
if (m->act_count == 0) {
/*
* We turn off page access, so that we have
* more accurate RSS stats. We don't do this
* in the normal page deactivation when the
* system is loaded VM wise, because the
* cost of the large number of page protect
* operations would be higher than the value
* of doing the operation.
*/
pmap_remove_all(m);
/* Dequeue to avoid later lock recursion. */
vm_page_dequeue_locked(m);
vm_page_deactivate(m);
} else {
m->act_count -= min(m->act_count, ACT_DECLINE);
vm_page_requeue_locked(m);
}
}
vm_page_unlock(m);
VM_OBJECT_WUNLOCK(object);
m = next;
}
vm_pagequeue_unlock(pq);
}
/*
* vm_pageout is the high level pageout daemon.
*/
static void
vm_pageout(void)
{
int error, pass;
/*
* Initialize some paging parameters.
*/
cnt.v_interrupt_free_min = 2;
if (cnt.v_page_count < 2000)
vm_pageout_page_count = 8;
/*
* v_free_reserved needs to include enough for the largest
* swap pager structures plus enough for any pv_entry structs
* when paging.
*/
if (cnt.v_page_count > 1024)
cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
else
cnt.v_free_min = 4;
cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
cnt.v_interrupt_free_min;
cnt.v_free_reserved = vm_pageout_page_count +
cnt.v_pageout_free_min + (cnt.v_page_count / 768);
cnt.v_free_severe = cnt.v_free_min / 2;
cnt.v_free_min += cnt.v_free_reserved;
cnt.v_free_severe += cnt.v_free_reserved;
/*
* v_free_target and v_cache_min control pageout hysteresis. Note
* that these are more a measure of the VM cache queue hysteresis
* then the VM free queue. Specifically, v_free_target is the
* high water mark (free+cache pages).
*
* v_free_reserved + v_cache_min (mostly means v_cache_min) is the
* low water mark, while v_free_min is the stop. v_cache_min must
* be big enough to handle memory needs while the pageout daemon
* is signalled and run to free more pages.
*/
if (cnt.v_free_count > 6144)
cnt.v_free_target = 4 * cnt.v_free_min + cnt.v_free_reserved;
else
cnt.v_free_target = 2 * cnt.v_free_min + cnt.v_free_reserved;
if (cnt.v_free_count > 2048) {
cnt.v_cache_min = cnt.v_free_target;
cnt.v_cache_max = 2 * cnt.v_cache_min;
cnt.v_inactive_target = (3 * cnt.v_free_target) / 2;
} else {
cnt.v_cache_min = 0;
cnt.v_cache_max = 0;
cnt.v_inactive_target = cnt.v_free_count / 4;
}
if (cnt.v_inactive_target > cnt.v_free_count / 3)
cnt.v_inactive_target = cnt.v_free_count / 3;
/* XXX does not really belong here */
if (vm_page_max_wired == 0)
vm_page_max_wired = cnt.v_free_count / 3;
if (vm_pageout_stats_max == 0)
vm_pageout_stats_max = cnt.v_free_target;
/*
* Set interval in seconds for stats scan.
*/
if (vm_pageout_stats_interval == 0)
vm_pageout_stats_interval = 5;
if (vm_pageout_full_stats_interval == 0)
vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
swap_pager_swap_init();
pass = 0;
/*
* The pageout daemon is never done, so loop forever.
*/
while (TRUE) {
/*
* If we have enough free memory, wakeup waiters. Do
* not clear vm_pages_needed until we reach our target,
* otherwise we may be woken up over and over again and
* waste a lot of cpu.
*/
mtx_lock(&vm_page_queue_free_mtx);
if (vm_pages_needed && !vm_page_count_min()) {
if (!vm_paging_needed())
vm_pages_needed = 0;
wakeup(&cnt.v_free_count);
}
if (vm_pages_needed) {
/*
* Still not done, take a second pass without waiting
* (unlimited dirty cleaning), otherwise sleep a bit
* and try again.
*/
++pass;
if (pass > 1)
msleep(&vm_pages_needed,
&vm_page_queue_free_mtx, PVM, "psleep",
hz / 2);
} else {
/*
* Good enough, sleep & handle stats. Prime the pass
* for the next run.
*/
if (pass > 1)
pass = 1;
else
pass = 0;
error = msleep(&vm_pages_needed,
&vm_page_queue_free_mtx, PVM, "psleep",
vm_pageout_stats_interval * hz);
if (error && !vm_pages_needed) {
mtx_unlock(&vm_page_queue_free_mtx);
pass = 0;
vm_pageout_page_stats();
continue;
}
}
if (vm_pages_needed)
cnt.v_pdwakeups++;
mtx_unlock(&vm_page_queue_free_mtx);
vm_pageout_scan(pass);
}
}
/*
* Unless the free page queue lock is held by the caller, this function
* should be regarded as advisory. Specifically, the caller should
* not msleep() on &cnt.v_free_count following this function unless
* the free page queue lock is held until the msleep() is performed.
*/
void
pagedaemon_wakeup(void)
{
if (!vm_pages_needed && curthread->td_proc != pageproc) {
vm_pages_needed = 1;
wakeup(&vm_pages_needed);
}
}
#if !defined(NO_SWAPPING)
static void
vm_req_vmdaemon(int req)
{
static int lastrun = 0;
mtx_lock(&vm_daemon_mtx);
vm_pageout_req_swapout |= req;
if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
wakeup(&vm_daemon_needed);
lastrun = ticks;
}
mtx_unlock(&vm_daemon_mtx);
}
static void
vm_daemon(void)
{
struct rlimit rsslim;
struct proc *p;
struct thread *td;
struct vmspace *vm;
int breakout, swapout_flags, tryagain, attempts;
#ifdef RACCT
uint64_t rsize, ravailable;
#endif
while (TRUE) {
mtx_lock(&vm_daemon_mtx);
#ifdef RACCT
msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", hz);
#else
msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 0);
#endif
swapout_flags = vm_pageout_req_swapout;
vm_pageout_req_swapout = 0;
mtx_unlock(&vm_daemon_mtx);
if (swapout_flags)
swapout_procs(swapout_flags);
/*
* scan the processes for exceeding their rlimits or if
* process is swapped out -- deactivate pages
*/
tryagain = 0;
attempts = 0;
again:
attempts++;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
vm_pindex_t limit, size;
/*
* if this is a system process or if we have already
* looked at this process, skip it.
*/
PROC_LOCK(p);
if (p->p_state != PRS_NORMAL ||
p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
PROC_UNLOCK(p);
continue;
}
/*
* if the process is in a non-running type state,
* don't touch it.
*/
breakout = 0;
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (!TD_ON_RUNQ(td) &&
!TD_IS_RUNNING(td) &&
!TD_IS_SLEEPING(td) &&
!TD_IS_SUSPENDED(td)) {
thread_unlock(td);
breakout = 1;
break;
}
thread_unlock(td);
}
if (breakout) {
PROC_UNLOCK(p);
continue;
}
/*
* get a limit
*/
lim_rlimit(p, RLIMIT_RSS, &rsslim);
limit = OFF_TO_IDX(
qmin(rsslim.rlim_cur, rsslim.rlim_max));
/*
* let processes that are swapped out really be
* swapped out set the limit to nothing (will force a
* swap-out.)
*/
if ((p->p_flag & P_INMEM) == 0)
limit = 0; /* XXX */
vm = vmspace_acquire_ref(p);
PROC_UNLOCK(p);
if (vm == NULL)
continue;
size = vmspace_resident_count(vm);
if (size >= limit) {
vm_pageout_map_deactivate_pages(
&vm->vm_map, limit);
}
#ifdef RACCT
rsize = IDX_TO_OFF(size);
PROC_LOCK(p);
racct_set(p, RACCT_RSS, rsize);
ravailable = racct_get_available(p, RACCT_RSS);
PROC_UNLOCK(p);
if (rsize > ravailable) {
/*
* Don't be overly aggressive; this might be
* an innocent process, and the limit could've
* been exceeded by some memory hog. Don't
* try to deactivate more than 1/4th of process'
* resident set size.
*/
if (attempts <= 8) {
if (ravailable < rsize - (rsize / 4))
ravailable = rsize - (rsize / 4);
}
vm_pageout_map_deactivate_pages(
&vm->vm_map, OFF_TO_IDX(ravailable));
/* Update RSS usage after paging out. */
size = vmspace_resident_count(vm);
rsize = IDX_TO_OFF(size);
PROC_LOCK(p);
racct_set(p, RACCT_RSS, rsize);
PROC_UNLOCK(p);
if (rsize > ravailable)
tryagain = 1;
}
#endif
vmspace_free(vm);
}
sx_sunlock(&allproc_lock);
if (tryagain != 0 && attempts <= 10)
goto again;
}
}
#endif /* !defined(NO_SWAPPING) */
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