2 * Copyright (c) 1991 Regents of the University of California.
4 * Copyright (c) 1994 John S. Dyson
6 * Copyright (c) 1994 David Greenman
8 * Copyright (c) 2005 Yahoo! Technologies Norway AS
11 * This code is derived from software contributed to Berkeley by
12 * The Mach Operating System project at Carnegie-Mellon University.
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * 2. Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in the
21 * documentation and/or other materials provided with the distribution.
22 * 3. All advertising materials mentioning features or use of this software
23 * must display the following acknowledgement:
24 * This product includes software developed by the University of
25 * California, Berkeley and its contributors.
26 * 4. Neither the name of the University nor the names of its contributors
27 * may be used to endorse or promote products derived from this software
28 * without specific prior written permission.
30 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
42 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
45 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
46 * All rights reserved.
48 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
50 * Permission to use, copy, modify and distribute this software and
51 * its documentation is hereby granted, provided that both the copyright
52 * notice and this permission notice appear in all copies of the
53 * software, derivative works or modified versions, and any portions
54 * thereof, and that both notices appear in supporting documentation.
56 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
57 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
58 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
60 * Carnegie Mellon requests users of this software to return to
62 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
63 * School of Computer Science
64 * Carnegie Mellon University
65 * Pittsburgh PA 15213-3890
67 * any improvements or extensions that they make and grant Carnegie the
68 * rights to redistribute these changes.
72 * The proverbial page-out daemon.
75 #include <sys/cdefs.h>
76 __FBSDID("$FreeBSD$");
79 #include <sys/param.h>
80 #include <sys/systm.h>
81 #include <sys/kernel.h>
82 #include <sys/eventhandler.h>
84 #include <sys/mutex.h>
86 #include <sys/kthread.h>
88 #include <sys/mount.h>
89 #include <sys/racct.h>
90 #include <sys/resourcevar.h>
91 #include <sys/sched.h>
92 #include <sys/signalvar.h>
93 #include <sys/vnode.h>
94 #include <sys/vmmeter.h>
96 #include <sys/sysctl.h>
99 #include <vm/vm_param.h>
100 #include <vm/vm_object.h>
101 #include <vm/vm_page.h>
102 #include <vm/vm_map.h>
103 #include <vm/vm_pageout.h>
104 #include <vm/vm_pager.h>
105 #include <vm/swap_pager.h>
106 #include <vm/vm_extern.h>
110 * System initialization
113 /* the kernel process "vm_pageout"*/
114 static void vm_pageout(void);
115 static int vm_pageout_clean(vm_page_t);
116 static void vm_pageout_scan(int pass);
118 struct proc *pageproc;
120 static struct kproc_desc page_kp = {
125 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start,
128 #if !defined(NO_SWAPPING)
129 /* the kernel process "vm_daemon"*/
130 static void vm_daemon(void);
131 static struct proc *vmproc;
133 static struct kproc_desc vm_kp = {
138 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
142 int vm_pages_needed; /* Event on which pageout daemon sleeps */
143 int vm_pageout_deficit; /* Estimated number of pages deficit */
144 int vm_pageout_pages_needed; /* flag saying that the pageout daemon needs pages */
146 #if !defined(NO_SWAPPING)
147 static int vm_pageout_req_swapout; /* XXX */
148 static int vm_daemon_needed;
149 static struct mtx vm_daemon_mtx;
150 /* Allow for use by vm_pageout before vm_daemon is initialized. */
151 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
153 static int vm_max_launder = 32;
154 static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0;
155 static int vm_pageout_full_stats_interval = 0;
156 static int vm_pageout_algorithm=0;
157 static int defer_swap_pageouts=0;
158 static int disable_swap_pageouts=0;
160 #if defined(NO_SWAPPING)
161 static int vm_swap_enabled=0;
162 static int vm_swap_idle_enabled=0;
164 static int vm_swap_enabled=1;
165 static int vm_swap_idle_enabled=0;
168 SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm,
169 CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt");
171 SYSCTL_INT(_vm, OID_AUTO, max_launder,
172 CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
174 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max,
175 CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length");
177 SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval,
178 CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan");
180 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval,
181 CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan");
183 #if defined(NO_SWAPPING)
184 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
185 CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout");
186 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
187 CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
189 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
190 CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
191 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
192 CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
195 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
196 CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
198 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
199 CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
201 static int pageout_lock_miss;
202 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
203 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
205 #define VM_PAGEOUT_PAGE_COUNT 16
206 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
208 int vm_page_max_wired; /* XXX max # of wired pages system-wide */
209 SYSCTL_INT(_vm, OID_AUTO, max_wired,
210 CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
212 #if !defined(NO_SWAPPING)
213 static void vm_pageout_map_deactivate_pages(vm_map_t, long);
214 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
215 static void vm_req_vmdaemon(int req);
217 static void vm_pageout_page_stats(void);
220 * Initialize a dummy page for marking the caller's place in the specified
221 * paging queue. In principle, this function only needs to set the flag
222 * PG_MARKER. Nonetheless, it sets the flag VPO_BUSY and initializes the hold
223 * count to one as safety precautions.
226 vm_pageout_init_marker(vm_page_t marker, u_short queue)
229 bzero(marker, sizeof(*marker));
230 marker->flags = PG_MARKER;
231 marker->oflags = VPO_BUSY;
232 marker->queue = queue;
233 marker->hold_count = 1;
237 * vm_pageout_fallback_object_lock:
239 * Lock vm object currently associated with `m'. VM_OBJECT_TRYLOCK is
240 * known to have failed and page queue must be either PQ_ACTIVE or
241 * PQ_INACTIVE. To avoid lock order violation, unlock the page queues
242 * while locking the vm object. Use marker page to detect page queue
243 * changes and maintain notion of next page on page queue. Return
244 * TRUE if no changes were detected, FALSE otherwise. vm object is
247 * This function depends on both the lock portion of struct vm_object
248 * and normal struct vm_page being type stable.
251 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
253 struct vm_page marker;
259 vm_pageout_init_marker(&marker, queue);
262 TAILQ_INSERT_AFTER(&vm_page_queues[queue].pl,
264 vm_page_unlock_queues();
266 VM_OBJECT_LOCK(object);
268 vm_page_lock_queues();
270 /* Page queue might have changed. */
271 *next = TAILQ_NEXT(&marker, pageq);
272 unchanged = (m->queue == queue &&
273 m->object == object &&
274 &marker == TAILQ_NEXT(m, pageq));
275 TAILQ_REMOVE(&vm_page_queues[queue].pl,
281 * Lock the page while holding the page queue lock. Use marker page
282 * to detect page queue changes and maintain notion of next page on
283 * page queue. Return TRUE if no changes were detected, FALSE
284 * otherwise. The page is locked on return. The page queue lock might
285 * be dropped and reacquired.
287 * This function depends on normal struct vm_page being type stable.
290 vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
292 struct vm_page marker;
296 vm_page_lock_assert(m, MA_NOTOWNED);
297 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
299 if (vm_page_trylock(m))
303 vm_pageout_init_marker(&marker, queue);
305 TAILQ_INSERT_AFTER(&vm_page_queues[queue].pl, m, &marker, pageq);
306 vm_page_unlock_queues();
308 vm_page_lock_queues();
310 /* Page queue might have changed. */
311 *next = TAILQ_NEXT(&marker, pageq);
312 unchanged = (m->queue == queue && &marker == TAILQ_NEXT(m, pageq));
313 TAILQ_REMOVE(&vm_page_queues[queue].pl, &marker, pageq);
320 * Clean the page and remove it from the laundry.
322 * We set the busy bit to cause potential page faults on this page to
323 * block. Note the careful timing, however, the busy bit isn't set till
324 * late and we cannot do anything that will mess with the page.
327 vm_pageout_clean(vm_page_t m)
330 vm_page_t mc[2*vm_pageout_page_count], pb, ps;
332 int ib, is, page_base;
333 vm_pindex_t pindex = m->pindex;
335 vm_page_lock_assert(m, MA_OWNED);
337 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
340 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
341 * with the new swapper, but we could have serious problems paging
342 * out other object types if there is insufficient memory.
344 * Unfortunately, checking free memory here is far too late, so the
345 * check has been moved up a procedural level.
349 * Can't clean the page if it's busy or held.
351 KASSERT(m->busy == 0 && (m->oflags & VPO_BUSY) == 0,
352 ("vm_pageout_clean: page %p is busy", m));
353 KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m));
356 mc[vm_pageout_page_count] = pb = ps = m;
358 page_base = vm_pageout_page_count;
363 * Scan object for clusterable pages.
365 * We can cluster ONLY if: ->> the page is NOT
366 * clean, wired, busy, held, or mapped into a
367 * buffer, and one of the following:
368 * 1) The page is inactive, or a seldom used
371 * 2) we force the issue.
373 * During heavy mmap/modification loads the pageout
374 * daemon can really fragment the underlying file
375 * due to flushing pages out of order and not trying
376 * align the clusters (which leave sporatic out-of-order
377 * holes). To solve this problem we do the reverse scan
378 * first and attempt to align our cluster, then do a
379 * forward scan if room remains.
382 while (ib && pageout_count < vm_pageout_page_count) {
390 if ((p = vm_page_prev(pb)) == NULL ||
391 (p->oflags & VPO_BUSY) != 0 || p->busy != 0) {
396 vm_page_test_dirty(p);
398 p->queue != PQ_INACTIVE ||
399 p->hold_count != 0) { /* may be undergoing I/O */
405 mc[--page_base] = pb = p;
409 * alignment boundry, stop here and switch directions. Do
412 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
416 while (pageout_count < vm_pageout_page_count &&
417 pindex + is < object->size) {
420 if ((p = vm_page_next(ps)) == NULL ||
421 (p->oflags & VPO_BUSY) != 0 || p->busy != 0)
424 vm_page_test_dirty(p);
426 p->queue != PQ_INACTIVE ||
427 p->hold_count != 0) { /* may be undergoing I/O */
432 mc[page_base + pageout_count] = ps = p;
438 * If we exhausted our forward scan, continue with the reverse scan
439 * when possible, even past a page boundry. This catches boundry
442 if (ib && pageout_count < vm_pageout_page_count)
446 * we allow reads during pageouts...
448 return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL,
453 * vm_pageout_flush() - launder the given pages
455 * The given pages are laundered. Note that we setup for the start of
456 * I/O ( i.e. busy the page ), mark it read-only, and bump the object
457 * reference count all in here rather then in the parent. If we want
458 * the parent to do more sophisticated things we may have to change
461 * Returned runlen is the count of pages between mreq and first
462 * page after mreq with status VM_PAGER_AGAIN.
463 * *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
464 * for any page in runlen set.
467 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
470 vm_object_t object = mc[0]->object;
471 int pageout_status[count];
475 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
476 mtx_assert(&vm_page_queue_mtx, MA_NOTOWNED);
479 * Initiate I/O. Bump the vm_page_t->busy counter and
480 * mark the pages read-only.
482 * We do not have to fixup the clean/dirty bits here... we can
483 * allow the pager to do it after the I/O completes.
485 * NOTE! mc[i]->dirty may be partial or fragmented due to an
486 * edge case with file fragments.
488 for (i = 0; i < count; i++) {
489 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
490 ("vm_pageout_flush: partially invalid page %p index %d/%d",
492 vm_page_io_start(mc[i]);
493 pmap_remove_write(mc[i]);
495 vm_object_pip_add(object, count);
497 vm_pager_put_pages(object, mc, count, flags, pageout_status);
499 runlen = count - mreq;
502 for (i = 0; i < count; i++) {
503 vm_page_t mt = mc[i];
505 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
506 (mt->aflags & PGA_WRITEABLE) == 0,
507 ("vm_pageout_flush: page %p is not write protected", mt));
508 switch (pageout_status[i]) {
515 * Page outside of range of object. Right now we
516 * essentially lose the changes by pretending it
524 * If page couldn't be paged out, then reactivate the
525 * page so it doesn't clog the inactive list. (We
526 * will try paging out it again later).
529 vm_page_activate(mt);
531 if (eio != NULL && i >= mreq && i - mreq < runlen)
535 if (i >= mreq && i - mreq < runlen)
541 * If the operation is still going, leave the page busy to
542 * block all other accesses. Also, leave the paging in
543 * progress indicator set so that we don't attempt an object
546 if (pageout_status[i] != VM_PAGER_PEND) {
547 vm_object_pip_wakeup(object);
548 vm_page_io_finish(mt);
549 if (vm_page_count_severe()) {
551 vm_page_try_to_cache(mt);
558 return (numpagedout);
561 #if !defined(NO_SWAPPING)
563 * vm_pageout_object_deactivate_pages
565 * Deactivate enough pages to satisfy the inactive target
568 * The object and map must be locked.
571 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
574 vm_object_t backing_object, object;
576 int actcount, remove_mode;
578 VM_OBJECT_LOCK_ASSERT(first_object, MA_OWNED);
579 if (first_object->type == OBJT_DEVICE ||
580 first_object->type == OBJT_SG)
582 for (object = first_object;; object = backing_object) {
583 if (pmap_resident_count(pmap) <= desired)
585 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
586 if (object->type == OBJT_PHYS || object->paging_in_progress)
590 if (object->shadow_count > 1)
593 * Scan the object's entire memory queue.
595 TAILQ_FOREACH(p, &object->memq, listq) {
596 if (pmap_resident_count(pmap) <= desired)
598 if ((p->oflags & VPO_BUSY) != 0 || p->busy != 0)
600 PCPU_INC(cnt.v_pdpages);
602 if (p->wire_count != 0 || p->hold_count != 0 ||
603 !pmap_page_exists_quick(pmap, p)) {
607 actcount = pmap_ts_referenced(p);
608 if ((p->aflags & PGA_REFERENCED) != 0) {
611 vm_page_aflag_clear(p, PGA_REFERENCED);
613 if (p->queue != PQ_ACTIVE && actcount != 0) {
615 p->act_count += actcount;
616 } else if (p->queue == PQ_ACTIVE) {
618 p->act_count -= min(p->act_count,
621 (vm_pageout_algorithm ||
622 p->act_count == 0)) {
624 vm_page_deactivate(p);
626 vm_page_lock_queues();
628 vm_page_unlock_queues();
632 if (p->act_count < ACT_MAX -
634 p->act_count += ACT_ADVANCE;
635 vm_page_lock_queues();
637 vm_page_unlock_queues();
639 } else if (p->queue == PQ_INACTIVE)
643 if ((backing_object = object->backing_object) == NULL)
645 VM_OBJECT_LOCK(backing_object);
646 if (object != first_object)
647 VM_OBJECT_UNLOCK(object);
650 if (object != first_object)
651 VM_OBJECT_UNLOCK(object);
655 * deactivate some number of pages in a map, try to do it fairly, but
656 * that is really hard to do.
659 vm_pageout_map_deactivate_pages(map, desired)
664 vm_object_t obj, bigobj;
667 if (!vm_map_trylock(map))
674 * first, search out the biggest object, and try to free pages from
677 tmpe = map->header.next;
678 while (tmpe != &map->header) {
679 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
680 obj = tmpe->object.vm_object;
681 if (obj != NULL && VM_OBJECT_TRYLOCK(obj)) {
682 if (obj->shadow_count <= 1 &&
684 bigobj->resident_page_count < obj->resident_page_count)) {
686 VM_OBJECT_UNLOCK(bigobj);
689 VM_OBJECT_UNLOCK(obj);
692 if (tmpe->wired_count > 0)
693 nothingwired = FALSE;
697 if (bigobj != NULL) {
698 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
699 VM_OBJECT_UNLOCK(bigobj);
702 * Next, hunt around for other pages to deactivate. We actually
703 * do this search sort of wrong -- .text first is not the best idea.
705 tmpe = map->header.next;
706 while (tmpe != &map->header) {
707 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
709 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
710 obj = tmpe->object.vm_object;
713 vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
714 VM_OBJECT_UNLOCK(obj);
721 * Remove all mappings if a process is swapped out, this will free page
724 if (desired == 0 && nothingwired) {
725 pmap_remove(vm_map_pmap(map), vm_map_min(map),
730 #endif /* !defined(NO_SWAPPING) */
733 * vm_pageout_scan does the dirty work for the pageout daemon.
736 vm_pageout_scan(int pass)
739 struct vm_page marker;
740 int page_shortage, maxscan, pcount;
741 int addl_page_shortage, addl_page_shortage_init;
744 int vnodes_skipped = 0;
748 * Decrease registered cache sizes.
750 EVENTHANDLER_INVOKE(vm_lowmem, 0);
752 * We do this explicitly after the caches have been drained above.
756 addl_page_shortage_init = atomic_readandclear_int(&vm_pageout_deficit);
759 * Calculate the number of pages we want to either free or move
762 page_shortage = vm_paging_target() + addl_page_shortage_init;
764 vm_pageout_init_marker(&marker, PQ_INACTIVE);
767 * Start scanning the inactive queue for pages we can move to the
768 * cache or free. The scan will stop when the target is reached or
769 * we have scanned the entire inactive queue. Note that m->act_count
770 * is not used to form decisions for the inactive queue, only for the
773 * maxlaunder limits the number of dirty pages we flush per scan.
774 * For most systems a smaller value (16 or 32) is more robust under
775 * extreme memory and disk pressure because any unnecessary writes
776 * to disk can result in extreme performance degredation. However,
777 * systems with excessive dirty pages (especially when MAP_NOSYNC is
778 * used) will die horribly with limited laundering. If the pageout
779 * daemon cannot clean enough pages in the first pass, we let it go
780 * all out in succeeding passes.
782 if ((maxlaunder = vm_max_launder) <= 1)
786 vm_page_lock_queues();
788 addl_page_shortage = addl_page_shortage_init;
789 maxscan = cnt.v_inactive_count;
791 for (m = TAILQ_FIRST(&vm_page_queues[PQ_INACTIVE].pl);
792 m != NULL && maxscan-- > 0 && page_shortage > 0;
797 if (m->queue != PQ_INACTIVE)
800 next = TAILQ_NEXT(m, pageq);
805 if (m->flags & PG_MARKER)
808 KASSERT((m->flags & PG_FICTITIOUS) == 0,
809 ("Fictitious page %p cannot be in inactive queue", m));
810 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
811 ("Unmanaged page %p cannot be in inactive queue", m));
816 if (!vm_pageout_page_lock(m, &next)) {
818 addl_page_shortage++;
823 * A held page may be undergoing I/O, so skip it.
828 addl_page_shortage++;
833 * Don't mess with busy pages, keep in the front of the
834 * queue, most likely are being paged out.
837 if (!VM_OBJECT_TRYLOCK(object) &&
838 (!vm_pageout_fallback_object_lock(m, &next) ||
839 m->hold_count != 0)) {
840 VM_OBJECT_UNLOCK(object);
842 addl_page_shortage++;
845 if (m->busy || (m->oflags & VPO_BUSY)) {
847 VM_OBJECT_UNLOCK(object);
848 addl_page_shortage++;
853 * If the object is not being used, we ignore previous
856 if (object->ref_count == 0) {
857 vm_page_aflag_clear(m, PGA_REFERENCED);
858 KASSERT(!pmap_page_is_mapped(m),
859 ("vm_pageout_scan: page %p is mapped", m));
862 * Otherwise, if the page has been referenced while in the
863 * inactive queue, we bump the "activation count" upwards,
864 * making it less likely that the page will be added back to
865 * the inactive queue prematurely again. Here we check the
866 * page tables (or emulated bits, if any), given the upper
867 * level VM system not knowing anything about existing
870 } else if (((m->aflags & PGA_REFERENCED) == 0) &&
871 (actcount = pmap_ts_referenced(m))) {
874 m->act_count += actcount + ACT_ADVANCE;
875 VM_OBJECT_UNLOCK(object);
880 * If the upper level VM system knows about any page
881 * references, we activate the page. We also set the
882 * "activation count" higher than normal so that we will less
883 * likely place pages back onto the inactive queue again.
885 if ((m->aflags & PGA_REFERENCED) != 0) {
886 vm_page_aflag_clear(m, PGA_REFERENCED);
887 actcount = pmap_ts_referenced(m);
890 m->act_count += actcount + ACT_ADVANCE + 1;
891 VM_OBJECT_UNLOCK(object);
896 * If the upper level VM system does not believe that the page
897 * is fully dirty, but it is mapped for write access, then we
898 * consult the pmap to see if the page's dirty status should
901 if (m->dirty != VM_PAGE_BITS_ALL &&
902 (m->aflags & PGA_WRITEABLE) != 0) {
904 * Avoid a race condition: Unless write access is
905 * removed from the page, another processor could
906 * modify it before all access is removed by the call
907 * to vm_page_cache() below. If vm_page_cache() finds
908 * that the page has been modified when it removes all
909 * access, it panics because it cannot cache dirty
910 * pages. In principle, we could eliminate just write
911 * access here rather than all access. In the expected
912 * case, when there are no last instant modifications
913 * to the page, removing all access will be cheaper
916 if (pmap_is_modified(m))
918 else if (m->dirty == 0)
924 * Invalid pages can be easily freed
929 } else if (m->dirty == 0) {
931 * Clean pages can be placed onto the cache queue.
932 * This effectively frees them.
936 } else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) {
938 * Dirty pages need to be paged out, but flushing
939 * a page is extremely expensive verses freeing
940 * a clean page. Rather then artificially limiting
941 * the number of pages we can flush, we instead give
942 * dirty pages extra priority on the inactive queue
943 * by forcing them to be cycled through the queue
944 * twice before being flushed, after which the
945 * (now clean) page will cycle through once more
946 * before being freed. This significantly extends
947 * the thrash point for a heavily loaded machine.
949 m->flags |= PG_WINATCFLS;
951 } else if (maxlaunder > 0) {
953 * We always want to try to flush some dirty pages if
954 * we encounter them, to keep the system stable.
955 * Normally this number is small, but under extreme
956 * pressure where there are insufficient clean pages
957 * on the inactive queue, we may have to go all out.
959 int swap_pageouts_ok, vfslocked = 0;
960 struct vnode *vp = NULL;
961 struct mount *mp = NULL;
963 if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
964 swap_pageouts_ok = 1;
966 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
967 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
968 vm_page_count_min());
973 * We don't bother paging objects that are "dead".
974 * Those objects are in a "rundown" state.
976 if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
978 VM_OBJECT_UNLOCK(object);
984 * Following operations may unlock
985 * vm_page_queue_mtx, invalidating the 'next'
986 * pointer. To prevent an inordinate number
987 * of restarts we use our marker to remember
991 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE].pl,
994 * The object is already known NOT to be dead. It
995 * is possible for the vget() to block the whole
996 * pageout daemon, but the new low-memory handling
997 * code should prevent it.
999 * The previous code skipped locked vnodes and, worse,
1000 * reordered pages in the queue. This results in
1001 * completely non-deterministic operation and, on a
1002 * busy system, can lead to extremely non-optimal
1003 * pageouts. For example, it can cause clean pages
1004 * to be freed and dirty pages to be moved to the end
1005 * of the queue. Since dirty pages are also moved to
1006 * the end of the queue once-cleaned, this gives
1007 * way too large a weighting to defering the freeing
1010 * We can't wait forever for the vnode lock, we might
1011 * deadlock due to a vn_read() getting stuck in
1012 * vm_wait while holding this vnode. We skip the
1013 * vnode if we can't get it in a reasonable amount
1016 if (object->type == OBJT_VNODE) {
1017 vm_page_unlock_queues();
1019 vp = object->handle;
1020 if (vp->v_type == VREG &&
1021 vn_start_write(vp, &mp, V_NOWAIT) != 0) {
1023 ++pageout_lock_miss;
1024 if (object->flags & OBJ_MIGHTBEDIRTY)
1026 vm_page_lock_queues();
1027 goto unlock_and_continue;
1030 ("vp %p with NULL v_mount", vp));
1031 vm_object_reference_locked(object);
1032 VM_OBJECT_UNLOCK(object);
1033 vfslocked = VFS_LOCK_GIANT(vp->v_mount);
1034 if (vget(vp, LK_EXCLUSIVE | LK_TIMELOCK,
1036 VM_OBJECT_LOCK(object);
1037 vm_page_lock_queues();
1038 ++pageout_lock_miss;
1039 if (object->flags & OBJ_MIGHTBEDIRTY)
1042 goto unlock_and_continue;
1044 VM_OBJECT_LOCK(object);
1046 vm_page_lock_queues();
1048 * The page might have been moved to another
1049 * queue during potential blocking in vget()
1050 * above. The page might have been freed and
1051 * reused for another vnode.
1053 if (m->queue != PQ_INACTIVE ||
1054 m->object != object ||
1055 TAILQ_NEXT(m, pageq) != &marker) {
1057 if (object->flags & OBJ_MIGHTBEDIRTY)
1059 goto unlock_and_continue;
1063 * The page may have been busied during the
1064 * blocking in vget(). We don't move the
1065 * page back onto the end of the queue so that
1066 * statistics are more correct if we don't.
1068 if (m->busy || (m->oflags & VPO_BUSY)) {
1070 goto unlock_and_continue;
1074 * If the page has become held it might
1075 * be undergoing I/O, so skip it
1077 if (m->hold_count) {
1080 if (object->flags & OBJ_MIGHTBEDIRTY)
1082 goto unlock_and_continue;
1087 * If a page is dirty, then it is either being washed
1088 * (but not yet cleaned) or it is still in the
1089 * laundry. If it is still in the laundry, then we
1090 * start the cleaning operation.
1092 * decrement page_shortage on success to account for
1093 * the (future) cleaned page. Otherwise we could wind
1094 * up laundering or cleaning too many pages.
1096 vm_page_unlock_queues();
1097 if (vm_pageout_clean(m) != 0) {
1101 vm_page_lock_queues();
1102 unlock_and_continue:
1103 vm_page_lock_assert(m, MA_NOTOWNED);
1104 VM_OBJECT_UNLOCK(object);
1106 vm_page_unlock_queues();
1109 VFS_UNLOCK_GIANT(vfslocked);
1110 vm_object_deallocate(object);
1111 vn_finished_write(mp);
1112 vm_page_lock_queues();
1114 next = TAILQ_NEXT(&marker, pageq);
1115 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl,
1117 vm_page_lock_assert(m, MA_NOTOWNED);
1121 VM_OBJECT_UNLOCK(object);
1125 * Compute the number of pages we want to try to move from the
1126 * active queue to the inactive queue.
1128 page_shortage = vm_paging_target() +
1129 cnt.v_inactive_target - cnt.v_inactive_count;
1130 page_shortage += addl_page_shortage;
1133 * Scan the active queue for things we can deactivate. We nominally
1134 * track the per-page activity counter and use it to locate
1135 * deactivation candidates.
1137 pcount = cnt.v_active_count;
1138 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
1139 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1141 while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) {
1143 KASSERT(m->queue == PQ_ACTIVE,
1144 ("vm_pageout_scan: page %p isn't active", m));
1146 next = TAILQ_NEXT(m, pageq);
1147 if ((m->flags & PG_MARKER) != 0) {
1151 KASSERT((m->flags & PG_FICTITIOUS) == 0,
1152 ("Fictitious page %p cannot be in active queue", m));
1153 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
1154 ("Unmanaged page %p cannot be in active queue", m));
1155 if (!vm_pageout_page_lock(m, &next)) {
1161 if (!VM_OBJECT_TRYLOCK(object) &&
1162 !vm_pageout_fallback_object_lock(m, &next)) {
1163 VM_OBJECT_UNLOCK(object);
1170 * Don't deactivate pages that are busy.
1172 if ((m->busy != 0) ||
1173 (m->oflags & VPO_BUSY) ||
1174 (m->hold_count != 0)) {
1176 VM_OBJECT_UNLOCK(object);
1183 * The count for pagedaemon pages is done after checking the
1184 * page for eligibility...
1189 * Check to see "how much" the page has been used.
1192 if (object->ref_count != 0) {
1193 if (m->aflags & PGA_REFERENCED) {
1196 actcount += pmap_ts_referenced(m);
1198 m->act_count += ACT_ADVANCE + actcount;
1199 if (m->act_count > ACT_MAX)
1200 m->act_count = ACT_MAX;
1205 * Since we have "tested" this bit, we need to clear it now.
1207 vm_page_aflag_clear(m, PGA_REFERENCED);
1210 * Only if an object is currently being used, do we use the
1211 * page activation count stats.
1213 if (actcount && (object->ref_count != 0)) {
1216 m->act_count -= min(m->act_count, ACT_DECLINE);
1217 if (vm_pageout_algorithm ||
1218 object->ref_count == 0 ||
1219 m->act_count == 0) {
1221 if (object->ref_count == 0) {
1222 KASSERT(!pmap_page_is_mapped(m),
1223 ("vm_pageout_scan: page %p is mapped", m));
1227 vm_page_deactivate(m);
1229 vm_page_deactivate(m);
1236 VM_OBJECT_UNLOCK(object);
1239 vm_page_unlock_queues();
1240 #if !defined(NO_SWAPPING)
1242 * Idle process swapout -- run once per second.
1244 if (vm_swap_idle_enabled) {
1246 if (time_second != lsec) {
1247 vm_req_vmdaemon(VM_SWAP_IDLE);
1254 * If we didn't get enough free pages, and we have skipped a vnode
1255 * in a writeable object, wakeup the sync daemon. And kick swapout
1256 * if we did not get enough free pages.
1258 if (vm_paging_target() > 0) {
1259 if (vnodes_skipped && vm_page_count_min())
1260 (void) speedup_syncer();
1261 #if !defined(NO_SWAPPING)
1262 if (vm_swap_enabled && vm_page_count_target())
1263 vm_req_vmdaemon(VM_SWAP_NORMAL);
1268 * If we are critically low on one of RAM or swap and low on
1269 * the other, kill the largest process. However, we avoid
1270 * doing this on the first pass in order to give ourselves a
1271 * chance to flush out dirty vnode-backed pages and to allow
1272 * active pages to be moved to the inactive queue and reclaimed.
1275 ((swap_pager_avail < 64 && vm_page_count_min()) ||
1276 (swap_pager_full && vm_paging_target() > 0)))
1277 vm_pageout_oom(VM_OOM_MEM);
1282 vm_pageout_oom(int shortage)
1284 struct proc *p, *bigproc;
1285 vm_offset_t size, bigsize;
1290 * We keep the process bigproc locked once we find it to keep anyone
1291 * from messing with it; however, there is a possibility of
1292 * deadlock if process B is bigproc and one of it's child processes
1293 * attempts to propagate a signal to B while we are waiting for A's
1294 * lock while walking this list. To avoid this, we don't block on
1295 * the process lock but just skip a process if it is already locked.
1299 sx_slock(&allproc_lock);
1300 FOREACH_PROC_IN_SYSTEM(p) {
1303 if (PROC_TRYLOCK(p) == 0)
1306 * If this is a system, protected or killed process, skip it.
1308 if (p->p_state != PRS_NORMAL ||
1309 (p->p_flag & (P_INEXEC | P_PROTECTED | P_SYSTEM)) ||
1310 (p->p_pid == 1) || P_KILLED(p) ||
1311 ((p->p_pid < 48) && (swap_pager_avail != 0))) {
1316 * If the process is in a non-running type state,
1317 * don't touch it. Check all the threads individually.
1320 FOREACH_THREAD_IN_PROC(p, td) {
1322 if (!TD_ON_RUNQ(td) &&
1323 !TD_IS_RUNNING(td) &&
1324 !TD_IS_SLEEPING(td) &&
1325 !TD_IS_SUSPENDED(td)) {
1337 * get the process size
1339 vm = vmspace_acquire_ref(p);
1344 if (!vm_map_trylock_read(&vm->vm_map)) {
1349 size = vmspace_swap_count(vm);
1350 vm_map_unlock_read(&vm->vm_map);
1351 if (shortage == VM_OOM_MEM)
1352 size += vmspace_resident_count(vm);
1355 * if the this process is bigger than the biggest one
1358 if (size > bigsize) {
1359 if (bigproc != NULL)
1360 PROC_UNLOCK(bigproc);
1366 sx_sunlock(&allproc_lock);
1367 if (bigproc != NULL) {
1368 killproc(bigproc, "out of swap space");
1369 sched_nice(bigproc, PRIO_MIN);
1370 PROC_UNLOCK(bigproc);
1371 wakeup(&cnt.v_free_count);
1376 * This routine tries to maintain the pseudo LRU active queue,
1377 * so that during long periods of time where there is no paging,
1378 * that some statistic accumulation still occurs. This code
1379 * helps the situation where paging just starts to occur.
1382 vm_pageout_page_stats()
1386 int pcount,tpcount; /* Number of pages to check */
1387 static int fullintervalcount = 0;
1391 (cnt.v_inactive_target + cnt.v_cache_max + cnt.v_free_min) -
1392 (cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
1394 if (page_shortage <= 0)
1397 vm_page_lock_queues();
1398 pcount = cnt.v_active_count;
1399 fullintervalcount += vm_pageout_stats_interval;
1400 if (fullintervalcount < vm_pageout_full_stats_interval) {
1401 tpcount = (int64_t)vm_pageout_stats_max * cnt.v_active_count /
1403 if (pcount > tpcount)
1406 fullintervalcount = 0;
1409 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
1410 while ((m != NULL) && (pcount-- > 0)) {
1413 KASSERT(m->queue == PQ_ACTIVE,
1414 ("vm_pageout_page_stats: page %p isn't active", m));
1416 next = TAILQ_NEXT(m, pageq);
1417 if ((m->flags & PG_MARKER) != 0) {
1421 vm_page_lock_assert(m, MA_NOTOWNED);
1422 if (!vm_pageout_page_lock(m, &next)) {
1428 if (!VM_OBJECT_TRYLOCK(object) &&
1429 !vm_pageout_fallback_object_lock(m, &next)) {
1430 VM_OBJECT_UNLOCK(object);
1437 * Don't deactivate pages that are busy.
1439 if ((m->busy != 0) ||
1440 (m->oflags & VPO_BUSY) ||
1441 (m->hold_count != 0)) {
1443 VM_OBJECT_UNLOCK(object);
1450 if (m->aflags & PGA_REFERENCED) {
1451 vm_page_aflag_clear(m, PGA_REFERENCED);
1455 actcount += pmap_ts_referenced(m);
1457 m->act_count += ACT_ADVANCE + actcount;
1458 if (m->act_count > ACT_MAX)
1459 m->act_count = ACT_MAX;
1462 if (m->act_count == 0) {
1464 * We turn off page access, so that we have
1465 * more accurate RSS stats. We don't do this
1466 * in the normal page deactivation when the
1467 * system is loaded VM wise, because the
1468 * cost of the large number of page protect
1469 * operations would be higher than the value
1470 * of doing the operation.
1473 vm_page_deactivate(m);
1475 m->act_count -= min(m->act_count, ACT_DECLINE);
1480 VM_OBJECT_UNLOCK(object);
1483 vm_page_unlock_queues();
1487 * vm_pageout is the high level pageout daemon.
1495 * Initialize some paging parameters.
1497 cnt.v_interrupt_free_min = 2;
1498 if (cnt.v_page_count < 2000)
1499 vm_pageout_page_count = 8;
1502 * v_free_reserved needs to include enough for the largest
1503 * swap pager structures plus enough for any pv_entry structs
1506 if (cnt.v_page_count > 1024)
1507 cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
1510 cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
1511 cnt.v_interrupt_free_min;
1512 cnt.v_free_reserved = vm_pageout_page_count +
1513 cnt.v_pageout_free_min + (cnt.v_page_count / 768);
1514 cnt.v_free_severe = cnt.v_free_min / 2;
1515 cnt.v_free_min += cnt.v_free_reserved;
1516 cnt.v_free_severe += cnt.v_free_reserved;
1519 * v_free_target and v_cache_min control pageout hysteresis. Note
1520 * that these are more a measure of the VM cache queue hysteresis
1521 * then the VM free queue. Specifically, v_free_target is the
1522 * high water mark (free+cache pages).
1524 * v_free_reserved + v_cache_min (mostly means v_cache_min) is the
1525 * low water mark, while v_free_min is the stop. v_cache_min must
1526 * be big enough to handle memory needs while the pageout daemon
1527 * is signalled and run to free more pages.
1529 if (cnt.v_free_count > 6144)
1530 cnt.v_free_target = 4 * cnt.v_free_min + cnt.v_free_reserved;
1532 cnt.v_free_target = 2 * cnt.v_free_min + cnt.v_free_reserved;
1534 if (cnt.v_free_count > 2048) {
1535 cnt.v_cache_min = cnt.v_free_target;
1536 cnt.v_cache_max = 2 * cnt.v_cache_min;
1537 cnt.v_inactive_target = (3 * cnt.v_free_target) / 2;
1539 cnt.v_cache_min = 0;
1540 cnt.v_cache_max = 0;
1541 cnt.v_inactive_target = cnt.v_free_count / 4;
1543 if (cnt.v_inactive_target > cnt.v_free_count / 3)
1544 cnt.v_inactive_target = cnt.v_free_count / 3;
1546 /* XXX does not really belong here */
1547 if (vm_page_max_wired == 0)
1548 vm_page_max_wired = cnt.v_free_count / 3;
1550 if (vm_pageout_stats_max == 0)
1551 vm_pageout_stats_max = cnt.v_free_target;
1554 * Set interval in seconds for stats scan.
1556 if (vm_pageout_stats_interval == 0)
1557 vm_pageout_stats_interval = 5;
1558 if (vm_pageout_full_stats_interval == 0)
1559 vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
1561 swap_pager_swap_init();
1564 * The pageout daemon is never done, so loop forever.
1568 * If we have enough free memory, wakeup waiters. Do
1569 * not clear vm_pages_needed until we reach our target,
1570 * otherwise we may be woken up over and over again and
1571 * waste a lot of cpu.
1573 mtx_lock(&vm_page_queue_free_mtx);
1574 if (vm_pages_needed && !vm_page_count_min()) {
1575 if (!vm_paging_needed())
1576 vm_pages_needed = 0;
1577 wakeup(&cnt.v_free_count);
1579 if (vm_pages_needed) {
1581 * Still not done, take a second pass without waiting
1582 * (unlimited dirty cleaning), otherwise sleep a bit
1587 msleep(&vm_pages_needed,
1588 &vm_page_queue_free_mtx, PVM, "psleep",
1592 * Good enough, sleep & handle stats. Prime the pass
1599 error = msleep(&vm_pages_needed,
1600 &vm_page_queue_free_mtx, PVM, "psleep",
1601 vm_pageout_stats_interval * hz);
1602 if (error && !vm_pages_needed) {
1603 mtx_unlock(&vm_page_queue_free_mtx);
1605 vm_pageout_page_stats();
1609 if (vm_pages_needed)
1611 mtx_unlock(&vm_page_queue_free_mtx);
1612 vm_pageout_scan(pass);
1617 * Unless the free page queue lock is held by the caller, this function
1618 * should be regarded as advisory. Specifically, the caller should
1619 * not msleep() on &cnt.v_free_count following this function unless
1620 * the free page queue lock is held until the msleep() is performed.
1626 if (!vm_pages_needed && curthread->td_proc != pageproc) {
1627 vm_pages_needed = 1;
1628 wakeup(&vm_pages_needed);
1632 #if !defined(NO_SWAPPING)
1634 vm_req_vmdaemon(int req)
1636 static int lastrun = 0;
1638 mtx_lock(&vm_daemon_mtx);
1639 vm_pageout_req_swapout |= req;
1640 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
1641 wakeup(&vm_daemon_needed);
1644 mtx_unlock(&vm_daemon_mtx);
1650 struct rlimit rsslim;
1654 int breakout, swapout_flags, tryagain, attempts;
1656 uint64_t rsize, ravailable;
1660 mtx_lock(&vm_daemon_mtx);
1662 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", hz);
1664 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 0);
1666 swapout_flags = vm_pageout_req_swapout;
1667 vm_pageout_req_swapout = 0;
1668 mtx_unlock(&vm_daemon_mtx);
1670 swapout_procs(swapout_flags);
1673 * scan the processes for exceeding their rlimits or if
1674 * process is swapped out -- deactivate pages
1680 sx_slock(&allproc_lock);
1681 FOREACH_PROC_IN_SYSTEM(p) {
1682 vm_pindex_t limit, size;
1685 * if this is a system process or if we have already
1686 * looked at this process, skip it.
1689 if (p->p_state != PRS_NORMAL ||
1690 p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
1695 * if the process is in a non-running type state,
1699 FOREACH_THREAD_IN_PROC(p, td) {
1701 if (!TD_ON_RUNQ(td) &&
1702 !TD_IS_RUNNING(td) &&
1703 !TD_IS_SLEEPING(td) &&
1704 !TD_IS_SUSPENDED(td)) {
1718 lim_rlimit(p, RLIMIT_RSS, &rsslim);
1720 qmin(rsslim.rlim_cur, rsslim.rlim_max));
1723 * let processes that are swapped out really be
1724 * swapped out set the limit to nothing (will force a
1727 if ((p->p_flag & P_INMEM) == 0)
1728 limit = 0; /* XXX */
1729 vm = vmspace_acquire_ref(p);
1734 size = vmspace_resident_count(vm);
1735 if (limit >= 0 && size >= limit) {
1736 vm_pageout_map_deactivate_pages(
1737 &vm->vm_map, limit);
1740 rsize = IDX_TO_OFF(size);
1742 racct_set(p, RACCT_RSS, rsize);
1743 ravailable = racct_get_available(p, RACCT_RSS);
1745 if (rsize > ravailable) {
1747 * Don't be overly aggressive; this might be
1748 * an innocent process, and the limit could've
1749 * been exceeded by some memory hog. Don't
1750 * try to deactivate more than 1/4th of process'
1751 * resident set size.
1753 if (attempts <= 8) {
1754 if (ravailable < rsize - (rsize / 4))
1755 ravailable = rsize - (rsize / 4);
1757 vm_pageout_map_deactivate_pages(
1758 &vm->vm_map, OFF_TO_IDX(ravailable));
1759 /* Update RSS usage after paging out. */
1760 size = vmspace_resident_count(vm);
1761 rsize = IDX_TO_OFF(size);
1763 racct_set(p, RACCT_RSS, rsize);
1765 if (rsize > ravailable)
1771 sx_sunlock(&allproc_lock);
1772 if (tryagain != 0 && attempts <= 10)
1776 #endif /* !defined(NO_SWAPPING) */