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 vm_pageout_init_marker(vm_page_t marker, u_short queue)
223 bzero(marker, sizeof(*marker));
224 marker->flags = PG_FICTITIOUS | PG_MARKER;
225 marker->oflags = VPO_BUSY;
226 marker->queue = queue;
227 marker->wire_count = 1;
231 * vm_pageout_fallback_object_lock:
233 * Lock vm object currently associated with `m'. VM_OBJECT_TRYLOCK is
234 * known to have failed and page queue must be either PQ_ACTIVE or
235 * PQ_INACTIVE. To avoid lock order violation, unlock the page queues
236 * while locking the vm object. Use marker page to detect page queue
237 * changes and maintain notion of next page on page queue. Return
238 * TRUE if no changes were detected, FALSE otherwise. vm object is
241 * This function depends on both the lock portion of struct vm_object
242 * and normal struct vm_page being type stable.
245 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
247 struct vm_page marker;
253 vm_pageout_init_marker(&marker, queue);
256 TAILQ_INSERT_AFTER(&vm_page_queues[queue].pl,
258 vm_page_unlock_queues();
260 VM_OBJECT_LOCK(object);
262 vm_page_lock_queues();
264 /* Page queue might have changed. */
265 *next = TAILQ_NEXT(&marker, pageq);
266 unchanged = (m->queue == queue &&
267 m->object == object &&
268 &marker == TAILQ_NEXT(m, pageq));
269 TAILQ_REMOVE(&vm_page_queues[queue].pl,
275 * Lock the page while holding the page queue lock. Use marker page
276 * to detect page queue changes and maintain notion of next page on
277 * page queue. Return TRUE if no changes were detected, FALSE
278 * otherwise. The page is locked on return. The page queue lock might
279 * be dropped and reacquired.
281 * This function depends on normal struct vm_page being type stable.
284 vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
286 struct vm_page marker;
290 vm_page_lock_assert(m, MA_NOTOWNED);
291 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
293 if (vm_page_trylock(m))
297 vm_pageout_init_marker(&marker, queue);
299 TAILQ_INSERT_AFTER(&vm_page_queues[queue].pl, m, &marker, pageq);
300 vm_page_unlock_queues();
302 vm_page_lock_queues();
304 /* Page queue might have changed. */
305 *next = TAILQ_NEXT(&marker, pageq);
306 unchanged = (m->queue == queue && &marker == TAILQ_NEXT(m, pageq));
307 TAILQ_REMOVE(&vm_page_queues[queue].pl, &marker, pageq);
314 * Clean the page and remove it from the laundry.
316 * We set the busy bit to cause potential page faults on this page to
317 * block. Note the careful timing, however, the busy bit isn't set till
318 * late and we cannot do anything that will mess with the page.
321 vm_pageout_clean(vm_page_t m)
324 vm_page_t mc[2*vm_pageout_page_count], pb, ps;
326 int ib, is, page_base;
327 vm_pindex_t pindex = m->pindex;
329 vm_page_lock_assert(m, MA_OWNED);
331 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
334 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
335 * with the new swapper, but we could have serious problems paging
336 * out other object types if there is insufficient memory.
338 * Unfortunately, checking free memory here is far too late, so the
339 * check has been moved up a procedural level.
343 * Can't clean the page if it's busy or held.
345 KASSERT(m->busy == 0 && (m->oflags & VPO_BUSY) == 0,
346 ("vm_pageout_clean: page %p is busy", m));
347 KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m));
350 mc[vm_pageout_page_count] = pb = ps = m;
352 page_base = vm_pageout_page_count;
357 * Scan object for clusterable pages.
359 * We can cluster ONLY if: ->> the page is NOT
360 * clean, wired, busy, held, or mapped into a
361 * buffer, and one of the following:
362 * 1) The page is inactive, or a seldom used
365 * 2) we force the issue.
367 * During heavy mmap/modification loads the pageout
368 * daemon can really fragment the underlying file
369 * due to flushing pages out of order and not trying
370 * align the clusters (which leave sporatic out-of-order
371 * holes). To solve this problem we do the reverse scan
372 * first and attempt to align our cluster, then do a
373 * forward scan if room remains.
376 while (ib && pageout_count < vm_pageout_page_count) {
384 if ((p = vm_page_prev(pb)) == NULL ||
385 (p->oflags & VPO_BUSY) != 0 || p->busy != 0) {
390 vm_page_test_dirty(p);
392 p->queue != PQ_INACTIVE ||
393 p->hold_count != 0) { /* may be undergoing I/O */
399 mc[--page_base] = pb = p;
403 * alignment boundry, stop here and switch directions. Do
406 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
410 while (pageout_count < vm_pageout_page_count &&
411 pindex + is < object->size) {
414 if ((p = vm_page_next(ps)) == NULL ||
415 (p->oflags & VPO_BUSY) != 0 || p->busy != 0)
418 vm_page_test_dirty(p);
420 p->queue != PQ_INACTIVE ||
421 p->hold_count != 0) { /* may be undergoing I/O */
426 mc[page_base + pageout_count] = ps = p;
432 * If we exhausted our forward scan, continue with the reverse scan
433 * when possible, even past a page boundry. This catches boundry
436 if (ib && pageout_count < vm_pageout_page_count)
440 * we allow reads during pageouts...
442 return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL));
446 * vm_pageout_flush() - launder the given pages
448 * The given pages are laundered. Note that we setup for the start of
449 * I/O ( i.e. busy the page ), mark it read-only, and bump the object
450 * reference count all in here rather then in the parent. If we want
451 * the parent to do more sophisticated things we may have to change
454 * Returned runlen is the count of pages between mreq and first
455 * page after mreq with status VM_PAGER_AGAIN.
458 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen)
460 vm_object_t object = mc[0]->object;
461 int pageout_status[count];
465 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
466 mtx_assert(&vm_page_queue_mtx, MA_NOTOWNED);
469 * Initiate I/O. Bump the vm_page_t->busy counter and
470 * mark the pages read-only.
472 * We do not have to fixup the clean/dirty bits here... we can
473 * allow the pager to do it after the I/O completes.
475 * NOTE! mc[i]->dirty may be partial or fragmented due to an
476 * edge case with file fragments.
478 for (i = 0; i < count; i++) {
479 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
480 ("vm_pageout_flush: partially invalid page %p index %d/%d",
482 vm_page_io_start(mc[i]);
483 pmap_remove_write(mc[i]);
485 vm_object_pip_add(object, count);
487 vm_pager_put_pages(object, mc, count, flags, pageout_status);
489 runlen = count - mreq;
490 for (i = 0; i < count; i++) {
491 vm_page_t mt = mc[i];
493 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
494 (mt->flags & PG_WRITEABLE) == 0,
495 ("vm_pageout_flush: page %p is not write protected", mt));
496 switch (pageout_status[i]) {
503 * Page outside of range of object. Right now we
504 * essentially lose the changes by pretending it
512 * If page couldn't be paged out, then reactivate the
513 * page so it doesn't clog the inactive list. (We
514 * will try paging out it again later).
517 vm_page_activate(mt);
521 if (i >= mreq && i - mreq < runlen)
527 * If the operation is still going, leave the page busy to
528 * block all other accesses. Also, leave the paging in
529 * progress indicator set so that we don't attempt an object
532 if (pageout_status[i] != VM_PAGER_PEND) {
533 vm_object_pip_wakeup(object);
534 vm_page_io_finish(mt);
535 if (vm_page_count_severe()) {
537 vm_page_try_to_cache(mt);
544 return (numpagedout);
547 #if !defined(NO_SWAPPING)
549 * vm_pageout_object_deactivate_pages
551 * Deactivate enough pages to satisfy the inactive target
554 * The object and map must be locked.
557 vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
560 vm_object_t backing_object, object;
562 int actcount, remove_mode;
564 VM_OBJECT_LOCK_ASSERT(first_object, MA_OWNED);
565 if (first_object->type == OBJT_DEVICE ||
566 first_object->type == OBJT_SG)
568 for (object = first_object;; object = backing_object) {
569 if (pmap_resident_count(pmap) <= desired)
571 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
572 if (object->type == OBJT_PHYS || object->paging_in_progress)
576 if (object->shadow_count > 1)
579 * Scan the object's entire memory queue.
581 TAILQ_FOREACH(p, &object->memq, listq) {
582 if (pmap_resident_count(pmap) <= desired)
584 if ((p->oflags & VPO_BUSY) != 0 || p->busy != 0)
586 PCPU_INC(cnt.v_pdpages);
588 if (p->wire_count != 0 || p->hold_count != 0 ||
589 !pmap_page_exists_quick(pmap, p)) {
593 actcount = pmap_ts_referenced(p);
594 if ((p->flags & PG_REFERENCED) != 0) {
597 vm_page_lock_queues();
598 vm_page_flag_clear(p, PG_REFERENCED);
599 vm_page_unlock_queues();
601 if (p->queue != PQ_ACTIVE && actcount != 0) {
603 p->act_count += actcount;
604 } else if (p->queue == PQ_ACTIVE) {
606 p->act_count -= min(p->act_count,
609 (vm_pageout_algorithm ||
610 p->act_count == 0)) {
612 vm_page_deactivate(p);
614 vm_page_lock_queues();
616 vm_page_unlock_queues();
620 if (p->act_count < ACT_MAX -
622 p->act_count += ACT_ADVANCE;
623 vm_page_lock_queues();
625 vm_page_unlock_queues();
627 } else if (p->queue == PQ_INACTIVE)
631 if ((backing_object = object->backing_object) == NULL)
633 VM_OBJECT_LOCK(backing_object);
634 if (object != first_object)
635 VM_OBJECT_UNLOCK(object);
638 if (object != first_object)
639 VM_OBJECT_UNLOCK(object);
643 * deactivate some number of pages in a map, try to do it fairly, but
644 * that is really hard to do.
647 vm_pageout_map_deactivate_pages(map, desired)
652 vm_object_t obj, bigobj;
655 if (!vm_map_trylock(map))
662 * first, search out the biggest object, and try to free pages from
665 tmpe = map->header.next;
666 while (tmpe != &map->header) {
667 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
668 obj = tmpe->object.vm_object;
669 if (obj != NULL && VM_OBJECT_TRYLOCK(obj)) {
670 if (obj->shadow_count <= 1 &&
672 bigobj->resident_page_count < obj->resident_page_count)) {
674 VM_OBJECT_UNLOCK(bigobj);
677 VM_OBJECT_UNLOCK(obj);
680 if (tmpe->wired_count > 0)
681 nothingwired = FALSE;
685 if (bigobj != NULL) {
686 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
687 VM_OBJECT_UNLOCK(bigobj);
690 * Next, hunt around for other pages to deactivate. We actually
691 * do this search sort of wrong -- .text first is not the best idea.
693 tmpe = map->header.next;
694 while (tmpe != &map->header) {
695 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
697 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
698 obj = tmpe->object.vm_object;
701 vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
702 VM_OBJECT_UNLOCK(obj);
709 * Remove all mappings if a process is swapped out, this will free page
712 if (desired == 0 && nothingwired) {
713 tmpe = map->header.next;
714 while (tmpe != &map->header) {
715 pmap_remove(vm_map_pmap(map), tmpe->start, tmpe->end);
721 #endif /* !defined(NO_SWAPPING) */
724 * vm_pageout_scan does the dirty work for the pageout daemon.
727 vm_pageout_scan(int pass)
730 struct vm_page marker;
731 int page_shortage, maxscan, pcount;
732 int addl_page_shortage, addl_page_shortage_init;
735 int vnodes_skipped = 0;
739 * Decrease registered cache sizes.
741 EVENTHANDLER_INVOKE(vm_lowmem, 0);
743 * We do this explicitly after the caches have been drained above.
747 addl_page_shortage_init = atomic_readandclear_int(&vm_pageout_deficit);
750 * Calculate the number of pages we want to either free or move
753 page_shortage = vm_paging_target() + addl_page_shortage_init;
755 vm_pageout_init_marker(&marker, PQ_INACTIVE);
758 * Start scanning the inactive queue for pages we can move to the
759 * cache or free. The scan will stop when the target is reached or
760 * we have scanned the entire inactive queue. Note that m->act_count
761 * is not used to form decisions for the inactive queue, only for the
764 * maxlaunder limits the number of dirty pages we flush per scan.
765 * For most systems a smaller value (16 or 32) is more robust under
766 * extreme memory and disk pressure because any unnecessary writes
767 * to disk can result in extreme performance degredation. However,
768 * systems with excessive dirty pages (especially when MAP_NOSYNC is
769 * used) will die horribly with limited laundering. If the pageout
770 * daemon cannot clean enough pages in the first pass, we let it go
771 * all out in succeeding passes.
773 if ((maxlaunder = vm_max_launder) <= 1)
777 vm_page_lock_queues();
779 addl_page_shortage = addl_page_shortage_init;
780 maxscan = cnt.v_inactive_count;
782 for (m = TAILQ_FIRST(&vm_page_queues[PQ_INACTIVE].pl);
783 m != NULL && maxscan-- > 0 && page_shortage > 0;
788 if (m->queue != PQ_INACTIVE)
791 next = TAILQ_NEXT(m, pageq);
796 if (m->flags & PG_MARKER)
802 if (!vm_pageout_page_lock(m, &next)) {
804 addl_page_shortage++;
809 * A held page may be undergoing I/O, so skip it.
814 addl_page_shortage++;
819 * Don't mess with busy pages, keep in the front of the
820 * queue, most likely are being paged out.
823 if (!VM_OBJECT_TRYLOCK(object) &&
824 (!vm_pageout_fallback_object_lock(m, &next) ||
825 m->hold_count != 0)) {
826 VM_OBJECT_UNLOCK(object);
828 addl_page_shortage++;
831 if (m->busy || (m->oflags & VPO_BUSY)) {
833 VM_OBJECT_UNLOCK(object);
834 addl_page_shortage++;
839 * If the object is not being used, we ignore previous
842 if (object->ref_count == 0) {
843 vm_page_flag_clear(m, PG_REFERENCED);
844 KASSERT(!pmap_page_is_mapped(m),
845 ("vm_pageout_scan: page %p is mapped", m));
848 * Otherwise, if the page has been referenced while in the
849 * inactive queue, we bump the "activation count" upwards,
850 * making it less likely that the page will be added back to
851 * the inactive queue prematurely again. Here we check the
852 * page tables (or emulated bits, if any), given the upper
853 * level VM system not knowing anything about existing
856 } else if (((m->flags & PG_REFERENCED) == 0) &&
857 (actcount = pmap_ts_referenced(m))) {
860 m->act_count += actcount + ACT_ADVANCE;
861 VM_OBJECT_UNLOCK(object);
866 * If the upper level VM system knows about any page
867 * references, we activate the page. We also set the
868 * "activation count" higher than normal so that we will less
869 * likely place pages back onto the inactive queue again.
871 if ((m->flags & PG_REFERENCED) != 0) {
872 vm_page_flag_clear(m, PG_REFERENCED);
873 actcount = pmap_ts_referenced(m);
876 m->act_count += actcount + ACT_ADVANCE + 1;
877 VM_OBJECT_UNLOCK(object);
882 * If the upper level VM system does not believe that the page
883 * is fully dirty, but it is mapped for write access, then we
884 * consult the pmap to see if the page's dirty status should
887 if (m->dirty != VM_PAGE_BITS_ALL &&
888 (m->flags & PG_WRITEABLE) != 0) {
890 * Avoid a race condition: Unless write access is
891 * removed from the page, another processor could
892 * modify it before all access is removed by the call
893 * to vm_page_cache() below. If vm_page_cache() finds
894 * that the page has been modified when it removes all
895 * access, it panics because it cannot cache dirty
896 * pages. In principle, we could eliminate just write
897 * access here rather than all access. In the expected
898 * case, when there are no last instant modifications
899 * to the page, removing all access will be cheaper
902 if (pmap_is_modified(m))
904 else if (m->dirty == 0)
910 * Invalid pages can be easily freed
915 } else if (m->dirty == 0) {
917 * Clean pages can be placed onto the cache queue.
918 * This effectively frees them.
922 } else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) {
924 * Dirty pages need to be paged out, but flushing
925 * a page is extremely expensive verses freeing
926 * a clean page. Rather then artificially limiting
927 * the number of pages we can flush, we instead give
928 * dirty pages extra priority on the inactive queue
929 * by forcing them to be cycled through the queue
930 * twice before being flushed, after which the
931 * (now clean) page will cycle through once more
932 * before being freed. This significantly extends
933 * the thrash point for a heavily loaded machine.
935 vm_page_flag_set(m, PG_WINATCFLS);
937 } else if (maxlaunder > 0) {
939 * We always want to try to flush some dirty pages if
940 * we encounter them, to keep the system stable.
941 * Normally this number is small, but under extreme
942 * pressure where there are insufficient clean pages
943 * on the inactive queue, we may have to go all out.
945 int swap_pageouts_ok, vfslocked = 0;
946 struct vnode *vp = NULL;
947 struct mount *mp = NULL;
949 if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
950 swap_pageouts_ok = 1;
952 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
953 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
954 vm_page_count_min());
959 * We don't bother paging objects that are "dead".
960 * Those objects are in a "rundown" state.
962 if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
964 VM_OBJECT_UNLOCK(object);
970 * Following operations may unlock
971 * vm_page_queue_mtx, invalidating the 'next'
972 * pointer. To prevent an inordinate number
973 * of restarts we use our marker to remember
977 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE].pl,
980 * The object is already known NOT to be dead. It
981 * is possible for the vget() to block the whole
982 * pageout daemon, but the new low-memory handling
983 * code should prevent it.
985 * The previous code skipped locked vnodes and, worse,
986 * reordered pages in the queue. This results in
987 * completely non-deterministic operation and, on a
988 * busy system, can lead to extremely non-optimal
989 * pageouts. For example, it can cause clean pages
990 * to be freed and dirty pages to be moved to the end
991 * of the queue. Since dirty pages are also moved to
992 * the end of the queue once-cleaned, this gives
993 * way too large a weighting to defering the freeing
996 * We can't wait forever for the vnode lock, we might
997 * deadlock due to a vn_read() getting stuck in
998 * vm_wait while holding this vnode. We skip the
999 * vnode if we can't get it in a reasonable amount
1002 if (object->type == OBJT_VNODE) {
1003 vm_page_unlock_queues();
1005 vp = object->handle;
1006 if (vp->v_type == VREG &&
1007 vn_start_write(vp, &mp, V_NOWAIT) != 0) {
1009 ++pageout_lock_miss;
1010 if (object->flags & OBJ_MIGHTBEDIRTY)
1012 vm_page_lock_queues();
1013 goto unlock_and_continue;
1016 ("vp %p with NULL v_mount", vp));
1017 vm_object_reference_locked(object);
1018 VM_OBJECT_UNLOCK(object);
1019 vfslocked = VFS_LOCK_GIANT(vp->v_mount);
1020 if (vget(vp, LK_EXCLUSIVE | LK_TIMELOCK,
1022 VM_OBJECT_LOCK(object);
1023 vm_page_lock_queues();
1024 ++pageout_lock_miss;
1025 if (object->flags & OBJ_MIGHTBEDIRTY)
1028 goto unlock_and_continue;
1030 VM_OBJECT_LOCK(object);
1032 vm_page_lock_queues();
1034 * The page might have been moved to another
1035 * queue during potential blocking in vget()
1036 * above. The page might have been freed and
1037 * reused for another vnode.
1039 if (m->queue != PQ_INACTIVE ||
1040 m->object != object ||
1041 TAILQ_NEXT(m, pageq) != &marker) {
1043 if (object->flags & OBJ_MIGHTBEDIRTY)
1045 goto unlock_and_continue;
1049 * The page may have been busied during the
1050 * blocking in vget(). We don't move the
1051 * page back onto the end of the queue so that
1052 * statistics are more correct if we don't.
1054 if (m->busy || (m->oflags & VPO_BUSY)) {
1056 goto unlock_and_continue;
1060 * If the page has become held it might
1061 * be undergoing I/O, so skip it
1063 if (m->hold_count) {
1066 if (object->flags & OBJ_MIGHTBEDIRTY)
1068 goto unlock_and_continue;
1073 * If a page is dirty, then it is either being washed
1074 * (but not yet cleaned) or it is still in the
1075 * laundry. If it is still in the laundry, then we
1076 * start the cleaning operation.
1078 * decrement page_shortage on success to account for
1079 * the (future) cleaned page. Otherwise we could wind
1080 * up laundering or cleaning too many pages.
1082 vm_page_unlock_queues();
1083 if (vm_pageout_clean(m) != 0) {
1087 vm_page_lock_queues();
1088 unlock_and_continue:
1089 vm_page_lock_assert(m, MA_NOTOWNED);
1090 VM_OBJECT_UNLOCK(object);
1092 vm_page_unlock_queues();
1095 VFS_UNLOCK_GIANT(vfslocked);
1096 vm_object_deallocate(object);
1097 vn_finished_write(mp);
1098 vm_page_lock_queues();
1100 next = TAILQ_NEXT(&marker, pageq);
1101 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl,
1103 vm_page_lock_assert(m, MA_NOTOWNED);
1107 VM_OBJECT_UNLOCK(object);
1111 * Compute the number of pages we want to try to move from the
1112 * active queue to the inactive queue.
1114 page_shortage = vm_paging_target() +
1115 cnt.v_inactive_target - cnt.v_inactive_count;
1116 page_shortage += addl_page_shortage;
1119 * Scan the active queue for things we can deactivate. We nominally
1120 * track the per-page activity counter and use it to locate
1121 * deactivation candidates.
1123 pcount = cnt.v_active_count;
1124 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
1125 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1127 while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) {
1129 KASSERT(m->queue == PQ_ACTIVE,
1130 ("vm_pageout_scan: page %p isn't active", m));
1132 next = TAILQ_NEXT(m, pageq);
1133 if ((m->flags & PG_MARKER) != 0) {
1137 if (!vm_pageout_page_lock(m, &next)) {
1143 if (!VM_OBJECT_TRYLOCK(object) &&
1144 !vm_pageout_fallback_object_lock(m, &next)) {
1145 VM_OBJECT_UNLOCK(object);
1152 * Don't deactivate pages that are busy.
1154 if ((m->busy != 0) ||
1155 (m->oflags & VPO_BUSY) ||
1156 (m->hold_count != 0)) {
1158 VM_OBJECT_UNLOCK(object);
1165 * The count for pagedaemon pages is done after checking the
1166 * page for eligibility...
1171 * Check to see "how much" the page has been used.
1174 if (object->ref_count != 0) {
1175 if (m->flags & PG_REFERENCED) {
1178 actcount += pmap_ts_referenced(m);
1180 m->act_count += ACT_ADVANCE + actcount;
1181 if (m->act_count > ACT_MAX)
1182 m->act_count = ACT_MAX;
1187 * Since we have "tested" this bit, we need to clear it now.
1189 vm_page_flag_clear(m, PG_REFERENCED);
1192 * Only if an object is currently being used, do we use the
1193 * page activation count stats.
1195 if (actcount && (object->ref_count != 0)) {
1198 m->act_count -= min(m->act_count, ACT_DECLINE);
1199 if (vm_pageout_algorithm ||
1200 object->ref_count == 0 ||
1201 m->act_count == 0) {
1203 if (object->ref_count == 0) {
1204 KASSERT(!pmap_page_is_mapped(m),
1205 ("vm_pageout_scan: page %p is mapped", m));
1209 vm_page_deactivate(m);
1211 vm_page_deactivate(m);
1218 VM_OBJECT_UNLOCK(object);
1221 vm_page_unlock_queues();
1222 #if !defined(NO_SWAPPING)
1224 * Idle process swapout -- run once per second.
1226 if (vm_swap_idle_enabled) {
1228 if (time_second != lsec) {
1229 vm_req_vmdaemon(VM_SWAP_IDLE);
1236 * If we didn't get enough free pages, and we have skipped a vnode
1237 * in a writeable object, wakeup the sync daemon. And kick swapout
1238 * if we did not get enough free pages.
1240 if (vm_paging_target() > 0) {
1241 if (vnodes_skipped && vm_page_count_min())
1242 (void) speedup_syncer();
1243 #if !defined(NO_SWAPPING)
1244 if (vm_swap_enabled && vm_page_count_target())
1245 vm_req_vmdaemon(VM_SWAP_NORMAL);
1250 * If we are critically low on one of RAM or swap and low on
1251 * the other, kill the largest process. However, we avoid
1252 * doing this on the first pass in order to give ourselves a
1253 * chance to flush out dirty vnode-backed pages and to allow
1254 * active pages to be moved to the inactive queue and reclaimed.
1257 ((swap_pager_avail < 64 && vm_page_count_min()) ||
1258 (swap_pager_full && vm_paging_target() > 0)))
1259 vm_pageout_oom(VM_OOM_MEM);
1264 vm_pageout_oom(int shortage)
1266 struct proc *p, *bigproc;
1267 vm_offset_t size, bigsize;
1272 * We keep the process bigproc locked once we find it to keep anyone
1273 * from messing with it; however, there is a possibility of
1274 * deadlock if process B is bigproc and one of it's child processes
1275 * attempts to propagate a signal to B while we are waiting for A's
1276 * lock while walking this list. To avoid this, we don't block on
1277 * the process lock but just skip a process if it is already locked.
1281 sx_slock(&allproc_lock);
1282 FOREACH_PROC_IN_SYSTEM(p) {
1285 if (PROC_TRYLOCK(p) == 0)
1288 * If this is a system, protected or killed process, skip it.
1290 if (p->p_state != PRS_NORMAL ||
1291 (p->p_flag & (P_INEXEC | P_PROTECTED | P_SYSTEM)) ||
1292 (p->p_pid == 1) || P_KILLED(p) ||
1293 ((p->p_pid < 48) && (swap_pager_avail != 0))) {
1298 * If the process is in a non-running type state,
1299 * don't touch it. Check all the threads individually.
1302 FOREACH_THREAD_IN_PROC(p, td) {
1304 if (!TD_ON_RUNQ(td) &&
1305 !TD_IS_RUNNING(td) &&
1306 !TD_IS_SLEEPING(td) &&
1307 !TD_IS_SUSPENDED(td)) {
1319 * get the process size
1321 vm = vmspace_acquire_ref(p);
1326 if (!vm_map_trylock_read(&vm->vm_map)) {
1331 size = vmspace_swap_count(vm);
1332 vm_map_unlock_read(&vm->vm_map);
1333 if (shortage == VM_OOM_MEM)
1334 size += vmspace_resident_count(vm);
1337 * if the this process is bigger than the biggest one
1340 if (size > bigsize) {
1341 if (bigproc != NULL)
1342 PROC_UNLOCK(bigproc);
1348 sx_sunlock(&allproc_lock);
1349 if (bigproc != NULL) {
1350 killproc(bigproc, "out of swap space");
1351 sched_nice(bigproc, PRIO_MIN);
1352 PROC_UNLOCK(bigproc);
1353 wakeup(&cnt.v_free_count);
1358 * This routine tries to maintain the pseudo LRU active queue,
1359 * so that during long periods of time where there is no paging,
1360 * that some statistic accumulation still occurs. This code
1361 * helps the situation where paging just starts to occur.
1364 vm_pageout_page_stats()
1368 int pcount,tpcount; /* Number of pages to check */
1369 static int fullintervalcount = 0;
1373 (cnt.v_inactive_target + cnt.v_cache_max + cnt.v_free_min) -
1374 (cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
1376 if (page_shortage <= 0)
1379 vm_page_lock_queues();
1380 pcount = cnt.v_active_count;
1381 fullintervalcount += vm_pageout_stats_interval;
1382 if (fullintervalcount < vm_pageout_full_stats_interval) {
1383 tpcount = (int64_t)vm_pageout_stats_max * cnt.v_active_count /
1385 if (pcount > tpcount)
1388 fullintervalcount = 0;
1391 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
1392 while ((m != NULL) && (pcount-- > 0)) {
1395 KASSERT(m->queue == PQ_ACTIVE,
1396 ("vm_pageout_page_stats: page %p isn't active", m));
1398 next = TAILQ_NEXT(m, pageq);
1399 if ((m->flags & PG_MARKER) != 0) {
1403 vm_page_lock_assert(m, MA_NOTOWNED);
1404 if (!vm_pageout_page_lock(m, &next)) {
1410 if (!VM_OBJECT_TRYLOCK(object) &&
1411 !vm_pageout_fallback_object_lock(m, &next)) {
1412 VM_OBJECT_UNLOCK(object);
1419 * Don't deactivate pages that are busy.
1421 if ((m->busy != 0) ||
1422 (m->oflags & VPO_BUSY) ||
1423 (m->hold_count != 0)) {
1425 VM_OBJECT_UNLOCK(object);
1432 if (m->flags & PG_REFERENCED) {
1433 vm_page_flag_clear(m, PG_REFERENCED);
1437 actcount += pmap_ts_referenced(m);
1439 m->act_count += ACT_ADVANCE + actcount;
1440 if (m->act_count > ACT_MAX)
1441 m->act_count = ACT_MAX;
1444 if (m->act_count == 0) {
1446 * We turn off page access, so that we have
1447 * more accurate RSS stats. We don't do this
1448 * in the normal page deactivation when the
1449 * system is loaded VM wise, because the
1450 * cost of the large number of page protect
1451 * operations would be higher than the value
1452 * of doing the operation.
1455 vm_page_deactivate(m);
1457 m->act_count -= min(m->act_count, ACT_DECLINE);
1462 VM_OBJECT_UNLOCK(object);
1465 vm_page_unlock_queues();
1469 * vm_pageout is the high level pageout daemon.
1477 * Initialize some paging parameters.
1479 cnt.v_interrupt_free_min = 2;
1480 if (cnt.v_page_count < 2000)
1481 vm_pageout_page_count = 8;
1484 * v_free_reserved needs to include enough for the largest
1485 * swap pager structures plus enough for any pv_entry structs
1488 if (cnt.v_page_count > 1024)
1489 cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
1492 cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
1493 cnt.v_interrupt_free_min;
1494 cnt.v_free_reserved = vm_pageout_page_count +
1495 cnt.v_pageout_free_min + (cnt.v_page_count / 768);
1496 cnt.v_free_severe = cnt.v_free_min / 2;
1497 cnt.v_free_min += cnt.v_free_reserved;
1498 cnt.v_free_severe += cnt.v_free_reserved;
1501 * v_free_target and v_cache_min control pageout hysteresis. Note
1502 * that these are more a measure of the VM cache queue hysteresis
1503 * then the VM free queue. Specifically, v_free_target is the
1504 * high water mark (free+cache pages).
1506 * v_free_reserved + v_cache_min (mostly means v_cache_min) is the
1507 * low water mark, while v_free_min is the stop. v_cache_min must
1508 * be big enough to handle memory needs while the pageout daemon
1509 * is signalled and run to free more pages.
1511 if (cnt.v_free_count > 6144)
1512 cnt.v_free_target = 4 * cnt.v_free_min + cnt.v_free_reserved;
1514 cnt.v_free_target = 2 * cnt.v_free_min + cnt.v_free_reserved;
1516 if (cnt.v_free_count > 2048) {
1517 cnt.v_cache_min = cnt.v_free_target;
1518 cnt.v_cache_max = 2 * cnt.v_cache_min;
1519 cnt.v_inactive_target = (3 * cnt.v_free_target) / 2;
1521 cnt.v_cache_min = 0;
1522 cnt.v_cache_max = 0;
1523 cnt.v_inactive_target = cnt.v_free_count / 4;
1525 if (cnt.v_inactive_target > cnt.v_free_count / 3)
1526 cnt.v_inactive_target = cnt.v_free_count / 3;
1528 /* XXX does not really belong here */
1529 if (vm_page_max_wired == 0)
1530 vm_page_max_wired = cnt.v_free_count / 3;
1532 if (vm_pageout_stats_max == 0)
1533 vm_pageout_stats_max = cnt.v_free_target;
1536 * Set interval in seconds for stats scan.
1538 if (vm_pageout_stats_interval == 0)
1539 vm_pageout_stats_interval = 5;
1540 if (vm_pageout_full_stats_interval == 0)
1541 vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
1543 swap_pager_swap_init();
1546 * The pageout daemon is never done, so loop forever.
1550 * If we have enough free memory, wakeup waiters. Do
1551 * not clear vm_pages_needed until we reach our target,
1552 * otherwise we may be woken up over and over again and
1553 * waste a lot of cpu.
1555 mtx_lock(&vm_page_queue_free_mtx);
1556 if (vm_pages_needed && !vm_page_count_min()) {
1557 if (!vm_paging_needed())
1558 vm_pages_needed = 0;
1559 wakeup(&cnt.v_free_count);
1561 if (vm_pages_needed) {
1563 * Still not done, take a second pass without waiting
1564 * (unlimited dirty cleaning), otherwise sleep a bit
1569 msleep(&vm_pages_needed,
1570 &vm_page_queue_free_mtx, PVM, "psleep",
1574 * Good enough, sleep & handle stats. Prime the pass
1581 error = msleep(&vm_pages_needed,
1582 &vm_page_queue_free_mtx, PVM, "psleep",
1583 vm_pageout_stats_interval * hz);
1584 if (error && !vm_pages_needed) {
1585 mtx_unlock(&vm_page_queue_free_mtx);
1587 vm_pageout_page_stats();
1591 if (vm_pages_needed)
1593 mtx_unlock(&vm_page_queue_free_mtx);
1594 vm_pageout_scan(pass);
1599 * Unless the free page queue lock is held by the caller, this function
1600 * should be regarded as advisory. Specifically, the caller should
1601 * not msleep() on &cnt.v_free_count following this function unless
1602 * the free page queue lock is held until the msleep() is performed.
1608 if (!vm_pages_needed && curthread->td_proc != pageproc) {
1609 vm_pages_needed = 1;
1610 wakeup(&vm_pages_needed);
1614 #if !defined(NO_SWAPPING)
1616 vm_req_vmdaemon(int req)
1618 static int lastrun = 0;
1620 mtx_lock(&vm_daemon_mtx);
1621 vm_pageout_req_swapout |= req;
1622 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
1623 wakeup(&vm_daemon_needed);
1626 mtx_unlock(&vm_daemon_mtx);
1632 struct rlimit rsslim;
1636 int breakout, swapout_flags, tryagain, attempts;
1637 uint64_t rsize, ravailable;
1640 mtx_lock(&vm_daemon_mtx);
1642 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", hz);
1644 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 0);
1646 swapout_flags = vm_pageout_req_swapout;
1647 vm_pageout_req_swapout = 0;
1648 mtx_unlock(&vm_daemon_mtx);
1650 swapout_procs(swapout_flags);
1653 * scan the processes for exceeding their rlimits or if
1654 * process is swapped out -- deactivate pages
1660 sx_slock(&allproc_lock);
1661 FOREACH_PROC_IN_SYSTEM(p) {
1662 vm_pindex_t limit, size;
1665 * if this is a system process or if we have already
1666 * looked at this process, skip it.
1669 if (p->p_state != PRS_NORMAL ||
1670 p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
1675 * if the process is in a non-running type state,
1679 FOREACH_THREAD_IN_PROC(p, td) {
1681 if (!TD_ON_RUNQ(td) &&
1682 !TD_IS_RUNNING(td) &&
1683 !TD_IS_SLEEPING(td) &&
1684 !TD_IS_SUSPENDED(td)) {
1698 lim_rlimit(p, RLIMIT_RSS, &rsslim);
1700 qmin(rsslim.rlim_cur, rsslim.rlim_max));
1703 * let processes that are swapped out really be
1704 * swapped out set the limit to nothing (will force a
1707 if ((p->p_flag & P_INMEM) == 0)
1708 limit = 0; /* XXX */
1709 vm = vmspace_acquire_ref(p);
1714 size = vmspace_resident_count(vm);
1715 if (limit >= 0 && size >= limit) {
1716 vm_pageout_map_deactivate_pages(
1717 &vm->vm_map, limit);
1719 rsize = IDX_TO_OFF(size);
1721 racct_set(p, RACCT_RSS, rsize);
1722 ravailable = racct_get_available(p, RACCT_RSS);
1724 if (rsize > ravailable) {
1726 * Don't be overly aggressive; this might be
1727 * an innocent process, and the limit could've
1728 * been exceeded by some memory hog. Don't
1729 * try to deactivate more than 1/4th of process'
1730 * resident set size.
1732 if (attempts <= 8) {
1733 if (ravailable < rsize - (rsize / 4))
1734 ravailable = rsize - (rsize / 4);
1736 vm_pageout_map_deactivate_pages(
1737 &vm->vm_map, OFF_TO_IDX(ravailable));
1738 /* Update RSS usage after paging out. */
1739 size = vmspace_resident_count(vm);
1740 rsize = IDX_TO_OFF(size);
1742 racct_set(p, RACCT_RSS, rsize);
1744 if (rsize > ravailable)
1749 sx_sunlock(&allproc_lock);
1750 if (tryagain != 0 && attempts <= 10)
1754 #endif /* !defined(NO_SWAPPING) */