2 * SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU)
4 * Copyright (c) 1991 Regents of the University of California.
6 * Copyright (c) 1994 John S. Dyson
8 * Copyright (c) 1994 David Greenman
10 * Copyright (c) 2005 Yahoo! Technologies Norway AS
11 * All rights reserved.
13 * This code is derived from software contributed to Berkeley by
14 * The Mach Operating System project at Carnegie-Mellon University.
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
19 * 1. Redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution.
24 * 3. All advertising materials mentioning features or use of this software
25 * must display the following acknowledgement:
26 * This product includes software developed by the University of
27 * California, Berkeley and its contributors.
28 * 4. Neither the name of the University nor the names of its contributors
29 * may be used to endorse or promote products derived from this software
30 * without specific prior written permission.
32 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
33 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
34 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
35 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
36 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
37 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
38 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
39 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
40 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
41 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
44 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
47 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
48 * All rights reserved.
50 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
52 * Permission to use, copy, modify and distribute this software and
53 * its documentation is hereby granted, provided that both the copyright
54 * notice and this permission notice appear in all copies of the
55 * software, derivative works or modified versions, and any portions
56 * thereof, and that both notices appear in supporting documentation.
58 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
59 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
60 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
62 * Carnegie Mellon requests users of this software to return to
64 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
65 * School of Computer Science
66 * Carnegie Mellon University
67 * Pittsburgh PA 15213-3890
69 * any improvements or extensions that they make and grant Carnegie the
70 * rights to redistribute these changes.
74 * The proverbial page-out daemon.
77 #include <sys/cdefs.h>
78 __FBSDID("$FreeBSD$");
82 #include <sys/param.h>
83 #include <sys/systm.h>
84 #include <sys/kernel.h>
85 #include <sys/eventhandler.h>
87 #include <sys/mutex.h>
89 #include <sys/kthread.h>
91 #include <sys/mount.h>
92 #include <sys/racct.h>
93 #include <sys/resourcevar.h>
94 #include <sys/sched.h>
96 #include <sys/signalvar.h>
99 #include <sys/vnode.h>
100 #include <sys/vmmeter.h>
101 #include <sys/rwlock.h>
103 #include <sys/sysctl.h>
106 #include <vm/vm_param.h>
107 #include <vm/vm_object.h>
108 #include <vm/vm_page.h>
109 #include <vm/vm_map.h>
110 #include <vm/vm_pageout.h>
111 #include <vm/vm_pager.h>
112 #include <vm/vm_phys.h>
113 #include <vm/vm_pagequeue.h>
114 #include <vm/swap_pager.h>
115 #include <vm/vm_extern.h>
119 * System initialization
122 /* the kernel process "vm_pageout"*/
123 static void vm_pageout(void);
124 static void vm_pageout_init(void);
125 static int vm_pageout_clean(vm_page_t m, int *numpagedout);
126 static int vm_pageout_cluster(vm_page_t m);
127 static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage,
128 int starting_page_shortage);
130 SYSINIT(pagedaemon_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, vm_pageout_init,
133 struct proc *pageproc;
135 static struct kproc_desc page_kp = {
140 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start,
143 SDT_PROVIDER_DEFINE(vm);
144 SDT_PROBE_DEFINE(vm, , , vm__lowmem_scan);
146 /* Pagedaemon activity rates, in subdivisions of one second. */
147 #define VM_LAUNDER_RATE 10
148 #define VM_INACT_SCAN_RATE 10
150 static int vm_pageout_oom_seq = 12;
152 static int vm_pageout_update_period;
153 static int disable_swap_pageouts;
154 static int lowmem_period = 10;
155 static int swapdev_enabled;
157 static int vm_panic_on_oom = 0;
159 SYSCTL_INT(_vm, OID_AUTO, panic_on_oom,
160 CTLFLAG_RWTUN, &vm_panic_on_oom, 0,
161 "Panic on the given number of out-of-memory errors instead of killing the largest process");
163 SYSCTL_INT(_vm, OID_AUTO, pageout_update_period,
164 CTLFLAG_RWTUN, &vm_pageout_update_period, 0,
165 "Maximum active LRU update period");
167 SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RWTUN, &lowmem_period, 0,
168 "Low memory callback period");
170 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
171 CTLFLAG_RWTUN, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
173 static int pageout_lock_miss;
174 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
175 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
177 SYSCTL_INT(_vm, OID_AUTO, pageout_oom_seq,
178 CTLFLAG_RWTUN, &vm_pageout_oom_seq, 0,
179 "back-to-back calls to oom detector to start OOM");
181 static int act_scan_laundry_weight = 3;
182 SYSCTL_INT(_vm, OID_AUTO, act_scan_laundry_weight, CTLFLAG_RWTUN,
183 &act_scan_laundry_weight, 0,
184 "weight given to clean vs. dirty pages in active queue scans");
186 static u_int vm_background_launder_rate = 4096;
187 SYSCTL_UINT(_vm, OID_AUTO, background_launder_rate, CTLFLAG_RWTUN,
188 &vm_background_launder_rate, 0,
189 "background laundering rate, in kilobytes per second");
191 static u_int vm_background_launder_max = 20 * 1024;
192 SYSCTL_UINT(_vm, OID_AUTO, background_launder_max, CTLFLAG_RWTUN,
193 &vm_background_launder_max, 0, "background laundering cap, in kilobytes");
195 int vm_pageout_page_count = 32;
197 u_long vm_page_max_user_wired;
198 SYSCTL_ULONG(_vm, OID_AUTO, max_user_wired, CTLFLAG_RW,
199 &vm_page_max_user_wired, 0,
200 "system-wide limit to user-wired page count");
202 static u_int isqrt(u_int num);
203 static int vm_pageout_launder(struct vm_domain *vmd, int launder,
205 static void vm_pageout_laundry_worker(void *arg);
208 struct vm_batchqueue bq;
209 struct vm_pagequeue *pq;
216 vm_pageout_init_scan(struct scan_state *ss, struct vm_pagequeue *pq,
217 vm_page_t marker, vm_page_t after, int maxscan)
220 vm_pagequeue_assert_locked(pq);
221 KASSERT((marker->a.flags & PGA_ENQUEUED) == 0,
222 ("marker %p already enqueued", marker));
225 TAILQ_INSERT_HEAD(&pq->pq_pl, marker, plinks.q);
227 TAILQ_INSERT_AFTER(&pq->pq_pl, after, marker, plinks.q);
228 vm_page_aflag_set(marker, PGA_ENQUEUED);
230 vm_batchqueue_init(&ss->bq);
233 ss->maxscan = maxscan;
235 vm_pagequeue_unlock(pq);
239 vm_pageout_end_scan(struct scan_state *ss)
241 struct vm_pagequeue *pq;
244 vm_pagequeue_assert_locked(pq);
245 KASSERT((ss->marker->a.flags & PGA_ENQUEUED) != 0,
246 ("marker %p not enqueued", ss->marker));
248 TAILQ_REMOVE(&pq->pq_pl, ss->marker, plinks.q);
249 vm_page_aflag_clear(ss->marker, PGA_ENQUEUED);
250 pq->pq_pdpages += ss->scanned;
254 * Add a small number of queued pages to a batch queue for later processing
255 * without the corresponding queue lock held. The caller must have enqueued a
256 * marker page at the desired start point for the scan. Pages will be
257 * physically dequeued if the caller so requests. Otherwise, the returned
258 * batch may contain marker pages, and it is up to the caller to handle them.
260 * When processing the batch queue, vm_pageout_defer() must be used to
261 * determine whether the page has been logically dequeued since the batch was
264 static __always_inline void
265 vm_pageout_collect_batch(struct scan_state *ss, const bool dequeue)
267 struct vm_pagequeue *pq;
268 vm_page_t m, marker, n;
273 KASSERT((marker->a.flags & PGA_ENQUEUED) != 0,
274 ("marker %p not enqueued", ss->marker));
276 vm_pagequeue_lock(pq);
277 for (m = TAILQ_NEXT(marker, plinks.q); m != NULL &&
278 ss->scanned < ss->maxscan && ss->bq.bq_cnt < VM_BATCHQUEUE_SIZE;
279 m = n, ss->scanned++) {
280 n = TAILQ_NEXT(m, plinks.q);
281 if ((m->flags & PG_MARKER) == 0) {
282 KASSERT((m->a.flags & PGA_ENQUEUED) != 0,
283 ("page %p not enqueued", m));
284 KASSERT((m->flags & PG_FICTITIOUS) == 0,
285 ("Fictitious page %p cannot be in page queue", m));
286 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
287 ("Unmanaged page %p cannot be in page queue", m));
291 (void)vm_batchqueue_insert(&ss->bq, m);
293 TAILQ_REMOVE(&pq->pq_pl, m, plinks.q);
294 vm_page_aflag_clear(m, PGA_ENQUEUED);
297 TAILQ_REMOVE(&pq->pq_pl, marker, plinks.q);
298 if (__predict_true(m != NULL))
299 TAILQ_INSERT_BEFORE(m, marker, plinks.q);
301 TAILQ_INSERT_TAIL(&pq->pq_pl, marker, plinks.q);
303 vm_pagequeue_cnt_add(pq, -ss->bq.bq_cnt);
304 vm_pagequeue_unlock(pq);
308 * Return the next page to be scanned, or NULL if the scan is complete.
310 static __always_inline vm_page_t
311 vm_pageout_next(struct scan_state *ss, const bool dequeue)
314 if (ss->bq.bq_cnt == 0)
315 vm_pageout_collect_batch(ss, dequeue);
316 return (vm_batchqueue_pop(&ss->bq));
320 * Determine whether processing of a page should be deferred and ensure that any
321 * outstanding queue operations are processed.
323 static __always_inline bool
324 vm_pageout_defer(vm_page_t m, const uint8_t queue, const bool enqueued)
328 as = vm_page_astate_load(m);
329 if (__predict_false(as.queue != queue ||
330 ((as.flags & PGA_ENQUEUED) != 0) != enqueued))
332 if ((as.flags & PGA_QUEUE_OP_MASK) != 0) {
333 vm_page_pqbatch_submit(m, queue);
340 * Scan for pages at adjacent offsets within the given page's object that are
341 * eligible for laundering, form a cluster of these pages and the given page,
342 * and launder that cluster.
345 vm_pageout_cluster(vm_page_t m)
348 vm_page_t mc[2 * vm_pageout_page_count], p, pb, ps;
350 int ib, is, page_base, pageout_count;
353 VM_OBJECT_ASSERT_WLOCKED(object);
356 vm_page_assert_xbusied(m);
358 mc[vm_pageout_page_count] = pb = ps = m;
360 page_base = vm_pageout_page_count;
365 * We can cluster only if the page is not clean, busy, or held, and
366 * the page is in the laundry queue.
368 * During heavy mmap/modification loads the pageout
369 * daemon can really fragment the underlying file
370 * due to flushing pages out of order and not trying to
371 * align the clusters (which leaves sporadic out-of-order
372 * holes). To solve this problem we do the reverse scan
373 * first and attempt to align our cluster, then do a
374 * forward scan if room remains.
377 while (ib != 0 && pageout_count < vm_pageout_page_count) {
382 if ((p = vm_page_prev(pb)) == NULL ||
383 vm_page_tryxbusy(p) == 0) {
387 if (vm_page_wired(p)) {
392 vm_page_test_dirty(p);
398 if (!vm_page_in_laundry(p) || !vm_page_try_remove_write(p)) {
403 mc[--page_base] = pb = p;
408 * We are at an alignment boundary. Stop here, and switch
409 * directions. Do not clear ib.
411 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
414 while (pageout_count < vm_pageout_page_count &&
415 pindex + is < object->size) {
416 if ((p = vm_page_next(ps)) == NULL ||
417 vm_page_tryxbusy(p) == 0)
419 if (vm_page_wired(p)) {
423 vm_page_test_dirty(p);
428 if (!vm_page_in_laundry(p) || !vm_page_try_remove_write(p)) {
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 an alignment boundary. This catches
440 * boundary conditions.
442 if (ib != 0 && pageout_count < vm_pageout_page_count)
445 return (vm_pageout_flush(&mc[page_base], pageout_count,
446 VM_PAGER_PUT_NOREUSE, 0, NULL, NULL));
450 * vm_pageout_flush() - launder the given pages
452 * The given pages are laundered. Note that we setup for the start of
453 * I/O ( i.e. busy the page ), mark it read-only, and bump the object
454 * reference count all in here rather then in the parent. If we want
455 * the parent to do more sophisticated things we may have to change
458 * Returned runlen is the count of pages between mreq and first
459 * page after mreq with status VM_PAGER_AGAIN.
460 * *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
461 * for any page in runlen set.
464 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
467 vm_object_t object = mc[0]->object;
468 int pageout_status[count];
472 VM_OBJECT_ASSERT_WLOCKED(object);
475 * Initiate I/O. Mark the pages shared busy and verify that they're
476 * valid and read-only.
478 * We do not have to fixup the clean/dirty bits here... we can
479 * allow the pager to do it after the I/O completes.
481 * NOTE! mc[i]->dirty may be partial or fragmented due to an
482 * edge case with file fragments.
484 for (i = 0; i < count; i++) {
485 KASSERT(vm_page_all_valid(mc[i]),
486 ("vm_pageout_flush: partially invalid page %p index %d/%d",
488 KASSERT((mc[i]->a.flags & PGA_WRITEABLE) == 0,
489 ("vm_pageout_flush: writeable page %p", mc[i]));
490 vm_page_busy_downgrade(mc[i]);
492 vm_object_pip_add(object, count);
494 vm_pager_put_pages(object, mc, count, flags, pageout_status);
496 runlen = count - mreq;
499 for (i = 0; i < count; i++) {
500 vm_page_t mt = mc[i];
502 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
503 !pmap_page_is_write_mapped(mt),
504 ("vm_pageout_flush: page %p is not write protected", mt));
505 switch (pageout_status[i]) {
508 * The page may have moved since laundering started, in
509 * which case it should be left alone.
511 if (vm_page_in_laundry(mt))
512 vm_page_deactivate_noreuse(mt);
519 * The page is outside the object's range. We pretend
520 * that the page out worked and clean the page, so the
521 * changes will be lost if the page is reclaimed by
525 if (vm_page_in_laundry(mt))
526 vm_page_deactivate_noreuse(mt);
531 * If the page couldn't be paged out to swap because the
532 * pager wasn't able to find space, place the page in
533 * the PQ_UNSWAPPABLE holding queue. This is an
534 * optimization that prevents the page daemon from
535 * wasting CPU cycles on pages that cannot be reclaimed
536 * becase no swap device is configured.
538 * Otherwise, reactivate the page so that it doesn't
539 * clog the laundry and inactive queues. (We will try
540 * paging it out again later.)
542 if (object->type == OBJT_SWAP &&
543 pageout_status[i] == VM_PAGER_FAIL) {
544 vm_page_unswappable(mt);
547 vm_page_activate(mt);
548 if (eio != NULL && i >= mreq && i - mreq < runlen)
552 if (i >= mreq && i - mreq < runlen)
558 * If the operation is still going, leave the page busy to
559 * block all other accesses. Also, leave the paging in
560 * progress indicator set so that we don't attempt an object
563 if (pageout_status[i] != VM_PAGER_PEND) {
564 vm_object_pip_wakeup(object);
570 return (numpagedout);
574 vm_pageout_swapon(void *arg __unused, struct swdevt *sp __unused)
577 atomic_store_rel_int(&swapdev_enabled, 1);
581 vm_pageout_swapoff(void *arg __unused, struct swdevt *sp __unused)
584 if (swap_pager_nswapdev() == 1)
585 atomic_store_rel_int(&swapdev_enabled, 0);
589 * Attempt to acquire all of the necessary locks to launder a page and
590 * then call through the clustering layer to PUTPAGES. Wait a short
591 * time for a vnode lock.
593 * Requires the page and object lock on entry, releases both before return.
594 * Returns 0 on success and an errno otherwise.
597 vm_pageout_clean(vm_page_t m, int *numpagedout)
606 VM_OBJECT_ASSERT_WLOCKED(object);
612 * The object is already known NOT to be dead. It
613 * is possible for the vget() to block the whole
614 * pageout daemon, but the new low-memory handling
615 * code should prevent it.
617 * We can't wait forever for the vnode lock, we might
618 * deadlock due to a vn_read() getting stuck in
619 * vm_wait while holding this vnode. We skip the
620 * vnode if we can't get it in a reasonable amount
623 if (object->type == OBJT_VNODE) {
626 if (vp->v_type == VREG &&
627 vn_start_write(vp, &mp, V_NOWAIT) != 0) {
633 ("vp %p with NULL v_mount", vp));
634 vm_object_reference_locked(object);
636 VM_OBJECT_WUNLOCK(object);
637 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
638 LK_SHARED : LK_EXCLUSIVE;
639 if (vget(vp, lockmode | LK_TIMELOCK, curthread)) {
644 VM_OBJECT_WLOCK(object);
647 * Ensure that the object and vnode were not disassociated
648 * while locks were dropped.
650 if (vp->v_object != object) {
656 * While the object was unlocked, the page may have been:
657 * (1) moved to a different queue,
658 * (2) reallocated to a different object,
659 * (3) reallocated to a different offset, or
662 if (!vm_page_in_laundry(m) || m->object != object ||
663 m->pindex != pindex || m->dirty == 0) {
669 * The page may have been busied while the object lock was
672 if (vm_page_tryxbusy(m) == 0) {
679 * Remove all writeable mappings, failing if the page is wired.
681 if (!vm_page_try_remove_write(m)) {
688 * If a page is dirty, then it is either being washed
689 * (but not yet cleaned) or it is still in the
690 * laundry. If it is still in the laundry, then we
691 * start the cleaning operation.
693 if ((*numpagedout = vm_pageout_cluster(m)) == 0)
697 VM_OBJECT_WUNLOCK(object);
703 vm_object_deallocate(object);
704 vn_finished_write(mp);
711 * Attempt to launder the specified number of pages.
713 * Returns the number of pages successfully laundered.
716 vm_pageout_launder(struct vm_domain *vmd, int launder, bool in_shortfall)
718 struct scan_state ss;
719 struct vm_pagequeue *pq;
722 vm_page_astate_t new, old;
723 int act_delta, error, numpagedout, queue, refs, starting_target;
728 starting_target = launder;
732 * Scan the laundry queues for pages eligible to be laundered. We stop
733 * once the target number of dirty pages have been laundered, or once
734 * we've reached the end of the queue. A single iteration of this loop
735 * may cause more than one page to be laundered because of clustering.
737 * As an optimization, we avoid laundering from PQ_UNSWAPPABLE when no
738 * swap devices are configured.
740 if (atomic_load_acq_int(&swapdev_enabled))
741 queue = PQ_UNSWAPPABLE;
746 marker = &vmd->vmd_markers[queue];
747 pq = &vmd->vmd_pagequeues[queue];
748 vm_pagequeue_lock(pq);
749 vm_pageout_init_scan(&ss, pq, marker, NULL, pq->pq_cnt);
750 while (launder > 0 && (m = vm_pageout_next(&ss, false)) != NULL) {
751 if (__predict_false((m->flags & PG_MARKER) != 0))
755 * Don't touch a page that was removed from the queue after the
756 * page queue lock was released. Otherwise, ensure that any
757 * pending queue operations, such as dequeues for wired pages,
760 if (vm_pageout_defer(m, queue, true))
764 * Lock the page's object.
766 if (object == NULL || object != m->object) {
768 VM_OBJECT_WUNLOCK(object);
769 object = atomic_load_ptr(&m->object);
770 if (__predict_false(object == NULL))
771 /* The page is being freed by another thread. */
774 /* Depends on type-stability. */
775 VM_OBJECT_WLOCK(object);
776 if (__predict_false(m->object != object)) {
777 VM_OBJECT_WUNLOCK(object);
783 if (vm_page_tryxbusy(m) == 0)
787 * Check for wirings now that we hold the object lock and have
788 * exclusively busied the page. If the page is mapped, it may
789 * still be wired by pmap lookups. The call to
790 * vm_page_try_remove_all() below atomically checks for such
791 * wirings and removes mappings. If the page is unmapped, the
792 * wire count is guaranteed not to increase after this check.
794 if (__predict_false(vm_page_wired(m)))
798 * Invalid pages can be easily freed. They cannot be
799 * mapped; vm_page_free() asserts this.
801 if (vm_page_none_valid(m))
804 refs = object->ref_count != 0 ? pmap_ts_referenced(m) : 0;
806 for (old = vm_page_astate_load(m);;) {
808 * Check to see if the page has been removed from the
809 * queue since the first such check. Leave it alone if
810 * so, discarding any references collected by
811 * pmap_ts_referenced().
813 if (__predict_false(_vm_page_queue(old) == PQ_NONE))
818 if ((old.flags & PGA_REFERENCED) != 0) {
819 new.flags &= ~PGA_REFERENCED;
822 if (act_delta == 0) {
824 } else if (object->ref_count != 0) {
826 * Increase the activation count if the page was
827 * referenced while in the laundry queue. This
828 * makes it less likely that the page will be
829 * returned prematurely to the laundry queue.
831 new.act_count += ACT_ADVANCE +
833 if (new.act_count > ACT_MAX)
834 new.act_count = ACT_MAX;
836 new.flags &= ~PGA_QUEUE_OP_MASK;
837 new.flags |= PGA_REQUEUE;
838 new.queue = PQ_ACTIVE;
839 if (!vm_page_pqstate_commit(m, &old, new))
843 * If this was a background laundering, count
844 * activated pages towards our target. The
845 * purpose of background laundering is to ensure
846 * that pages are eventually cycled through the
847 * laundry queue, and an activation is a valid
852 VM_CNT_INC(v_reactivated);
854 } else if ((object->flags & OBJ_DEAD) == 0) {
855 new.flags |= PGA_REQUEUE;
856 if (!vm_page_pqstate_commit(m, &old, new))
864 * If the page appears to be clean at the machine-independent
865 * layer, then remove all of its mappings from the pmap in
866 * anticipation of freeing it. If, however, any of the page's
867 * mappings allow write access, then the page may still be
868 * modified until the last of those mappings are removed.
870 if (object->ref_count != 0) {
871 vm_page_test_dirty(m);
872 if (m->dirty == 0 && !vm_page_try_remove_all(m))
877 * Clean pages are freed, and dirty pages are paged out unless
878 * they belong to a dead object. Requeueing dirty pages from
879 * dead objects is pointless, as they are being paged out and
880 * freed by the thread that destroyed the object.
885 * Now we are guaranteed that no other threads are
886 * manipulating the page, check for a last-second
889 if (vm_pageout_defer(m, queue, true))
893 } else if ((object->flags & OBJ_DEAD) == 0) {
894 if (object->type != OBJT_SWAP &&
895 object->type != OBJT_DEFAULT)
897 else if (disable_swap_pageouts)
907 * Form a cluster with adjacent, dirty pages from the
908 * same object, and page out that entire cluster.
910 * The adjacent, dirty pages must also be in the
911 * laundry. However, their mappings are not checked
912 * for new references. Consequently, a recently
913 * referenced page may be paged out. However, that
914 * page will not be prematurely reclaimed. After page
915 * out, the page will be placed in the inactive queue,
916 * where any new references will be detected and the
919 error = vm_pageout_clean(m, &numpagedout);
921 launder -= numpagedout;
922 ss.scanned += numpagedout;
923 } else if (error == EDEADLK) {
933 if (object != NULL) {
934 VM_OBJECT_WUNLOCK(object);
937 vm_pagequeue_lock(pq);
938 vm_pageout_end_scan(&ss);
939 vm_pagequeue_unlock(pq);
941 if (launder > 0 && queue == PQ_UNSWAPPABLE) {
947 * Wakeup the sync daemon if we skipped a vnode in a writeable object
948 * and we didn't launder enough pages.
950 if (vnodes_skipped > 0 && launder > 0)
951 (void)speedup_syncer();
953 return (starting_target - launder);
957 * Compute the integer square root.
962 u_int bit, root, tmp;
964 bit = num != 0 ? (1u << ((fls(num) - 1) & ~1)) : 0;
979 * Perform the work of the laundry thread: periodically wake up and determine
980 * whether any pages need to be laundered. If so, determine the number of pages
981 * that need to be laundered, and launder them.
984 vm_pageout_laundry_worker(void *arg)
986 struct vm_domain *vmd;
987 struct vm_pagequeue *pq;
988 uint64_t nclean, ndirty, nfreed;
989 int domain, last_target, launder, shortfall, shortfall_cycle, target;
992 domain = (uintptr_t)arg;
993 vmd = VM_DOMAIN(domain);
994 pq = &vmd->vmd_pagequeues[PQ_LAUNDRY];
995 KASSERT(vmd->vmd_segs != 0, ("domain without segments"));
998 in_shortfall = false;
1000 last_target = target = 0;
1004 * Calls to these handlers are serialized by the swap syscall lock.
1006 (void)EVENTHANDLER_REGISTER(swapon, vm_pageout_swapon, vmd,
1007 EVENTHANDLER_PRI_ANY);
1008 (void)EVENTHANDLER_REGISTER(swapoff, vm_pageout_swapoff, vmd,
1009 EVENTHANDLER_PRI_ANY);
1012 * The pageout laundry worker is never done, so loop forever.
1015 KASSERT(target >= 0, ("negative target %d", target));
1016 KASSERT(shortfall_cycle >= 0,
1017 ("negative cycle %d", shortfall_cycle));
1021 * First determine whether we need to launder pages to meet a
1022 * shortage of free pages.
1024 if (shortfall > 0) {
1025 in_shortfall = true;
1026 shortfall_cycle = VM_LAUNDER_RATE / VM_INACT_SCAN_RATE;
1028 } else if (!in_shortfall)
1030 else if (shortfall_cycle == 0 || vm_laundry_target(vmd) <= 0) {
1032 * We recently entered shortfall and began laundering
1033 * pages. If we have completed that laundering run
1034 * (and we are no longer in shortfall) or we have met
1035 * our laundry target through other activity, then we
1036 * can stop laundering pages.
1038 in_shortfall = false;
1042 launder = target / shortfall_cycle--;
1046 * There's no immediate need to launder any pages; see if we
1047 * meet the conditions to perform background laundering:
1049 * 1. The ratio of dirty to clean inactive pages exceeds the
1050 * background laundering threshold, or
1051 * 2. we haven't yet reached the target of the current
1052 * background laundering run.
1054 * The background laundering threshold is not a constant.
1055 * Instead, it is a slowly growing function of the number of
1056 * clean pages freed by the page daemon since the last
1057 * background laundering. Thus, as the ratio of dirty to
1058 * clean inactive pages grows, the amount of memory pressure
1059 * required to trigger laundering decreases. We ensure
1060 * that the threshold is non-zero after an inactive queue
1061 * scan, even if that scan failed to free a single clean page.
1064 nclean = vmd->vmd_free_count +
1065 vmd->vmd_pagequeues[PQ_INACTIVE].pq_cnt;
1066 ndirty = vmd->vmd_pagequeues[PQ_LAUNDRY].pq_cnt;
1067 if (target == 0 && ndirty * isqrt(howmany(nfreed + 1,
1068 vmd->vmd_free_target - vmd->vmd_free_min)) >= nclean) {
1069 target = vmd->vmd_background_launder_target;
1073 * We have a non-zero background laundering target. If we've
1074 * laundered up to our maximum without observing a page daemon
1075 * request, just stop. This is a safety belt that ensures we
1076 * don't launder an excessive amount if memory pressure is low
1077 * and the ratio of dirty to clean pages is large. Otherwise,
1078 * proceed at the background laundering rate.
1083 last_target = target;
1084 } else if (last_target - target >=
1085 vm_background_launder_max * PAGE_SIZE / 1024) {
1088 launder = vm_background_launder_rate * PAGE_SIZE / 1024;
1089 launder /= VM_LAUNDER_RATE;
1090 if (launder > target)
1097 * Because of I/O clustering, the number of laundered
1098 * pages could exceed "target" by the maximum size of
1099 * a cluster minus one.
1101 target -= min(vm_pageout_launder(vmd, launder,
1102 in_shortfall), target);
1103 pause("laundp", hz / VM_LAUNDER_RATE);
1107 * If we're not currently laundering pages and the page daemon
1108 * hasn't posted a new request, sleep until the page daemon
1111 vm_pagequeue_lock(pq);
1112 if (target == 0 && vmd->vmd_laundry_request == VM_LAUNDRY_IDLE)
1113 (void)mtx_sleep(&vmd->vmd_laundry_request,
1114 vm_pagequeue_lockptr(pq), PVM, "launds", 0);
1117 * If the pagedaemon has indicated that it's in shortfall, start
1118 * a shortfall laundering unless we're already in the middle of
1119 * one. This may preempt a background laundering.
1121 if (vmd->vmd_laundry_request == VM_LAUNDRY_SHORTFALL &&
1122 (!in_shortfall || shortfall_cycle == 0)) {
1123 shortfall = vm_laundry_target(vmd) +
1124 vmd->vmd_pageout_deficit;
1130 vmd->vmd_laundry_request = VM_LAUNDRY_IDLE;
1131 nfreed += vmd->vmd_clean_pages_freed;
1132 vmd->vmd_clean_pages_freed = 0;
1133 vm_pagequeue_unlock(pq);
1138 * Compute the number of pages we want to try to move from the
1139 * active queue to either the inactive or laundry queue.
1141 * When scanning active pages during a shortage, we make clean pages
1142 * count more heavily towards the page shortage than dirty pages.
1143 * This is because dirty pages must be laundered before they can be
1144 * reused and thus have less utility when attempting to quickly
1145 * alleviate a free page shortage. However, this weighting also
1146 * causes the scan to deactivate dirty pages more aggressively,
1147 * improving the effectiveness of clustering.
1150 vm_pageout_active_target(struct vm_domain *vmd)
1154 shortage = vmd->vmd_inactive_target + vm_paging_target(vmd) -
1155 (vmd->vmd_pagequeues[PQ_INACTIVE].pq_cnt +
1156 vmd->vmd_pagequeues[PQ_LAUNDRY].pq_cnt / act_scan_laundry_weight);
1157 shortage *= act_scan_laundry_weight;
1162 * Scan the active queue. If there is no shortage of inactive pages, scan a
1163 * small portion of the queue in order to maintain quasi-LRU.
1166 vm_pageout_scan_active(struct vm_domain *vmd, int page_shortage)
1168 struct scan_state ss;
1170 vm_page_t m, marker;
1171 struct vm_pagequeue *pq;
1172 vm_page_astate_t old, new;
1174 int act_delta, max_scan, ps_delta, refs, scan_tick;
1177 marker = &vmd->vmd_markers[PQ_ACTIVE];
1178 pq = &vmd->vmd_pagequeues[PQ_ACTIVE];
1179 vm_pagequeue_lock(pq);
1182 * If we're just idle polling attempt to visit every
1183 * active page within 'update_period' seconds.
1186 if (vm_pageout_update_period != 0) {
1187 min_scan = pq->pq_cnt;
1188 min_scan *= scan_tick - vmd->vmd_last_active_scan;
1189 min_scan /= hz * vm_pageout_update_period;
1192 if (min_scan > 0 || (page_shortage > 0 && pq->pq_cnt > 0))
1193 vmd->vmd_last_active_scan = scan_tick;
1196 * Scan the active queue for pages that can be deactivated. Update
1197 * the per-page activity counter and use it to identify deactivation
1198 * candidates. Held pages may be deactivated.
1200 * To avoid requeuing each page that remains in the active queue, we
1201 * implement the CLOCK algorithm. To keep the implementation of the
1202 * enqueue operation consistent for all page queues, we use two hands,
1203 * represented by marker pages. Scans begin at the first hand, which
1204 * precedes the second hand in the queue. When the two hands meet,
1205 * they are moved back to the head and tail of the queue, respectively,
1206 * and scanning resumes.
1208 max_scan = page_shortage > 0 ? pq->pq_cnt : min_scan;
1210 vm_pageout_init_scan(&ss, pq, marker, &vmd->vmd_clock[0], max_scan);
1211 while ((m = vm_pageout_next(&ss, false)) != NULL) {
1212 if (__predict_false(m == &vmd->vmd_clock[1])) {
1213 vm_pagequeue_lock(pq);
1214 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_clock[0], plinks.q);
1215 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_clock[1], plinks.q);
1216 TAILQ_INSERT_HEAD(&pq->pq_pl, &vmd->vmd_clock[0],
1218 TAILQ_INSERT_TAIL(&pq->pq_pl, &vmd->vmd_clock[1],
1220 max_scan -= ss.scanned;
1221 vm_pageout_end_scan(&ss);
1224 if (__predict_false((m->flags & PG_MARKER) != 0))
1228 * Don't touch a page that was removed from the queue after the
1229 * page queue lock was released. Otherwise, ensure that any
1230 * pending queue operations, such as dequeues for wired pages,
1233 if (vm_pageout_defer(m, PQ_ACTIVE, true))
1237 * A page's object pointer may be set to NULL before
1238 * the object lock is acquired.
1240 object = atomic_load_ptr(&m->object);
1241 if (__predict_false(object == NULL))
1243 * The page has been removed from its object.
1247 /* Deferred free of swap space. */
1248 if ((m->a.flags & PGA_SWAP_FREE) != 0 &&
1249 VM_OBJECT_TRYWLOCK(object)) {
1250 if (m->object == object)
1251 vm_pager_page_unswapped(m);
1252 VM_OBJECT_WUNLOCK(object);
1256 * Check to see "how much" the page has been used.
1258 * Test PGA_REFERENCED after calling pmap_ts_referenced() so
1259 * that a reference from a concurrently destroyed mapping is
1260 * observed here and now.
1262 * Perform an unsynchronized object ref count check. While
1263 * the page lock ensures that the page is not reallocated to
1264 * another object, in particular, one with unmanaged mappings
1265 * that cannot support pmap_ts_referenced(), two races are,
1266 * nonetheless, possible:
1267 * 1) The count was transitioning to zero, but we saw a non-
1268 * zero value. pmap_ts_referenced() will return zero
1269 * because the page is not mapped.
1270 * 2) The count was transitioning to one, but we saw zero.
1271 * This race delays the detection of a new reference. At
1272 * worst, we will deactivate and reactivate the page.
1274 refs = object->ref_count != 0 ? pmap_ts_referenced(m) : 0;
1276 old = vm_page_astate_load(m);
1279 * Check to see if the page has been removed from the
1280 * queue since the first such check. Leave it alone if
1281 * so, discarding any references collected by
1282 * pmap_ts_referenced().
1284 if (__predict_false(_vm_page_queue(old) == PQ_NONE))
1288 * Advance or decay the act_count based on recent usage.
1292 if ((old.flags & PGA_REFERENCED) != 0) {
1293 new.flags &= ~PGA_REFERENCED;
1296 if (act_delta != 0) {
1297 new.act_count += ACT_ADVANCE + act_delta;
1298 if (new.act_count > ACT_MAX)
1299 new.act_count = ACT_MAX;
1301 new.act_count -= min(new.act_count,
1305 if (new.act_count > 0) {
1307 * Adjust the activation count and keep the page
1308 * in the active queue. The count might be left
1309 * unchanged if it is saturated. The page may
1310 * have been moved to a different queue since we
1311 * started the scan, in which case we move it
1315 if (old.queue != PQ_ACTIVE) {
1316 new.flags &= ~PGA_QUEUE_OP_MASK;
1317 new.flags |= PGA_REQUEUE;
1318 new.queue = PQ_ACTIVE;
1322 * When not short for inactive pages, let dirty
1323 * pages go through the inactive queue before
1324 * moving to the laundry queue. This gives them
1325 * some extra time to be reactivated,
1326 * potentially avoiding an expensive pageout.
1327 * However, during a page shortage, the inactive
1328 * queue is necessarily small, and so dirty
1329 * pages would only spend a trivial amount of
1330 * time in the inactive queue. Therefore, we
1331 * might as well place them directly in the
1332 * laundry queue to reduce queuing overhead.
1334 * Calling vm_page_test_dirty() here would
1335 * require acquisition of the object's write
1336 * lock. However, during a page shortage,
1337 * directing dirty pages into the laundry queue
1338 * is only an optimization and not a
1339 * requirement. Therefore, we simply rely on
1340 * the opportunistic updates to the page's dirty
1341 * field by the pmap.
1343 if (page_shortage <= 0) {
1344 nqueue = PQ_INACTIVE;
1346 } else if (m->dirty == 0) {
1347 nqueue = PQ_INACTIVE;
1348 ps_delta = act_scan_laundry_weight;
1350 nqueue = PQ_LAUNDRY;
1354 new.flags &= ~PGA_QUEUE_OP_MASK;
1355 new.flags |= PGA_REQUEUE;
1358 } while (!vm_page_pqstate_commit(m, &old, new));
1360 page_shortage -= ps_delta;
1362 vm_pagequeue_lock(pq);
1363 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_clock[0], plinks.q);
1364 TAILQ_INSERT_AFTER(&pq->pq_pl, marker, &vmd->vmd_clock[0], plinks.q);
1365 vm_pageout_end_scan(&ss);
1366 vm_pagequeue_unlock(pq);
1370 vm_pageout_reinsert_inactive_page(struct vm_pagequeue *pq, vm_page_t marker,
1373 vm_page_astate_t as;
1375 vm_pagequeue_assert_locked(pq);
1377 as = vm_page_astate_load(m);
1378 if (as.queue != PQ_INACTIVE || (as.flags & PGA_ENQUEUED) != 0)
1380 vm_page_aflag_set(m, PGA_ENQUEUED);
1381 TAILQ_INSERT_BEFORE(marker, m, plinks.q);
1386 * Re-add stuck pages to the inactive queue. We will examine them again
1387 * during the next scan. If the queue state of a page has changed since
1388 * it was physically removed from the page queue in
1389 * vm_pageout_collect_batch(), don't do anything with that page.
1392 vm_pageout_reinsert_inactive(struct scan_state *ss, struct vm_batchqueue *bq,
1395 struct vm_pagequeue *pq;
1400 marker = ss->marker;
1404 if (vm_batchqueue_insert(bq, m))
1406 vm_pagequeue_lock(pq);
1407 delta += vm_pageout_reinsert_inactive_page(pq, marker, m);
1409 vm_pagequeue_lock(pq);
1410 while ((m = vm_batchqueue_pop(bq)) != NULL)
1411 delta += vm_pageout_reinsert_inactive_page(pq, marker, m);
1412 vm_pagequeue_cnt_add(pq, delta);
1413 vm_pagequeue_unlock(pq);
1414 vm_batchqueue_init(bq);
1418 * Attempt to reclaim the requested number of pages from the inactive queue.
1419 * Returns true if the shortage was addressed.
1422 vm_pageout_scan_inactive(struct vm_domain *vmd, int shortage,
1425 struct scan_state ss;
1426 struct vm_batchqueue rq;
1427 vm_page_t m, marker;
1428 struct vm_pagequeue *pq;
1430 vm_page_astate_t old, new;
1431 int act_delta, addl_page_shortage, deficit, page_shortage, refs;
1432 int starting_page_shortage;
1435 * The addl_page_shortage is an estimate of the number of temporarily
1436 * stuck pages in the inactive queue. In other words, the
1437 * number of pages from the inactive count that should be
1438 * discounted in setting the target for the active queue scan.
1440 addl_page_shortage = 0;
1443 * vmd_pageout_deficit counts the number of pages requested in
1444 * allocations that failed because of a free page shortage. We assume
1445 * that the allocations will be reattempted and thus include the deficit
1446 * in our scan target.
1448 deficit = atomic_readandclear_int(&vmd->vmd_pageout_deficit);
1449 starting_page_shortage = page_shortage = shortage + deficit;
1452 vm_batchqueue_init(&rq);
1455 * Start scanning the inactive queue for pages that we can free. The
1456 * scan will stop when we reach the target or we have scanned the
1457 * entire queue. (Note that m->a.act_count is not used to make
1458 * decisions for the inactive queue, only for the active queue.)
1460 marker = &vmd->vmd_markers[PQ_INACTIVE];
1461 pq = &vmd->vmd_pagequeues[PQ_INACTIVE];
1462 vm_pagequeue_lock(pq);
1463 vm_pageout_init_scan(&ss, pq, marker, NULL, pq->pq_cnt);
1464 while (page_shortage > 0 && (m = vm_pageout_next(&ss, true)) != NULL) {
1465 KASSERT((m->flags & PG_MARKER) == 0,
1466 ("marker page %p was dequeued", m));
1469 * Don't touch a page that was removed from the queue after the
1470 * page queue lock was released. Otherwise, ensure that any
1471 * pending queue operations, such as dequeues for wired pages,
1474 if (vm_pageout_defer(m, PQ_INACTIVE, false))
1478 * Lock the page's object.
1480 if (object == NULL || object != m->object) {
1482 VM_OBJECT_WUNLOCK(object);
1483 object = atomic_load_ptr(&m->object);
1484 if (__predict_false(object == NULL))
1485 /* The page is being freed by another thread. */
1488 /* Depends on type-stability. */
1489 VM_OBJECT_WLOCK(object);
1490 if (__predict_false(m->object != object)) {
1491 VM_OBJECT_WUNLOCK(object);
1497 if (vm_page_tryxbusy(m) == 0) {
1499 * Don't mess with busy pages. Leave them at
1500 * the front of the queue. Most likely, they
1501 * are being paged out and will leave the
1502 * queue shortly after the scan finishes. So,
1503 * they ought to be discounted from the
1506 addl_page_shortage++;
1510 /* Deferred free of swap space. */
1511 if ((m->a.flags & PGA_SWAP_FREE) != 0)
1512 vm_pager_page_unswapped(m);
1515 * Check for wirings now that we hold the object lock and have
1516 * exclusively busied the page. If the page is mapped, it may
1517 * still be wired by pmap lookups. The call to
1518 * vm_page_try_remove_all() below atomically checks for such
1519 * wirings and removes mappings. If the page is unmapped, the
1520 * wire count is guaranteed not to increase after this check.
1522 if (__predict_false(vm_page_wired(m)))
1526 * Invalid pages can be easily freed. They cannot be
1527 * mapped, vm_page_free() asserts this.
1529 if (vm_page_none_valid(m))
1532 refs = object->ref_count != 0 ? pmap_ts_referenced(m) : 0;
1534 for (old = vm_page_astate_load(m);;) {
1536 * Check to see if the page has been removed from the
1537 * queue since the first such check. Leave it alone if
1538 * so, discarding any references collected by
1539 * pmap_ts_referenced().
1541 if (__predict_false(_vm_page_queue(old) == PQ_NONE))
1546 if ((old.flags & PGA_REFERENCED) != 0) {
1547 new.flags &= ~PGA_REFERENCED;
1550 if (act_delta == 0) {
1552 } else if (object->ref_count != 0) {
1554 * Increase the activation count if the
1555 * page was referenced while in the
1556 * inactive queue. This makes it less
1557 * likely that the page will be returned
1558 * prematurely to the inactive queue.
1560 new.act_count += ACT_ADVANCE +
1562 if (new.act_count > ACT_MAX)
1563 new.act_count = ACT_MAX;
1565 new.flags &= ~PGA_QUEUE_OP_MASK;
1566 new.flags |= PGA_REQUEUE;
1567 new.queue = PQ_ACTIVE;
1568 if (!vm_page_pqstate_commit(m, &old, new))
1571 VM_CNT_INC(v_reactivated);
1573 } else if ((object->flags & OBJ_DEAD) == 0) {
1574 new.queue = PQ_INACTIVE;
1575 new.flags |= PGA_REQUEUE;
1576 if (!vm_page_pqstate_commit(m, &old, new))
1584 * If the page appears to be clean at the machine-independent
1585 * layer, then remove all of its mappings from the pmap in
1586 * anticipation of freeing it. If, however, any of the page's
1587 * mappings allow write access, then the page may still be
1588 * modified until the last of those mappings are removed.
1590 if (object->ref_count != 0) {
1591 vm_page_test_dirty(m);
1592 if (m->dirty == 0 && !vm_page_try_remove_all(m))
1597 * Clean pages can be freed, but dirty pages must be sent back
1598 * to the laundry, unless they belong to a dead object.
1599 * Requeueing dirty pages from dead objects is pointless, as
1600 * they are being paged out and freed by the thread that
1601 * destroyed the object.
1603 if (m->dirty == 0) {
1606 * Now we are guaranteed that no other threads are
1607 * manipulating the page, check for a last-second
1608 * reference that would save it from doom.
1610 if (vm_pageout_defer(m, PQ_INACTIVE, false))
1614 * Because we dequeued the page and have already checked
1615 * for pending dequeue and enqueue requests, we can
1616 * safely disassociate the page from the inactive queue
1617 * without holding the queue lock.
1619 m->a.queue = PQ_NONE;
1624 if ((object->flags & OBJ_DEAD) == 0)
1630 vm_pageout_reinsert_inactive(&ss, &rq, m);
1633 VM_OBJECT_WUNLOCK(object);
1634 vm_pageout_reinsert_inactive(&ss, &rq, NULL);
1635 vm_pageout_reinsert_inactive(&ss, &ss.bq, NULL);
1636 vm_pagequeue_lock(pq);
1637 vm_pageout_end_scan(&ss);
1638 vm_pagequeue_unlock(pq);
1640 VM_CNT_ADD(v_dfree, starting_page_shortage - page_shortage);
1643 * Wake up the laundry thread so that it can perform any needed
1644 * laundering. If we didn't meet our target, we're in shortfall and
1645 * need to launder more aggressively. If PQ_LAUNDRY is empty and no
1646 * swap devices are configured, the laundry thread has no work to do, so
1647 * don't bother waking it up.
1649 * The laundry thread uses the number of inactive queue scans elapsed
1650 * since the last laundering to determine whether to launder again, so
1653 if (starting_page_shortage > 0) {
1654 pq = &vmd->vmd_pagequeues[PQ_LAUNDRY];
1655 vm_pagequeue_lock(pq);
1656 if (vmd->vmd_laundry_request == VM_LAUNDRY_IDLE &&
1657 (pq->pq_cnt > 0 || atomic_load_acq_int(&swapdev_enabled))) {
1658 if (page_shortage > 0) {
1659 vmd->vmd_laundry_request = VM_LAUNDRY_SHORTFALL;
1660 VM_CNT_INC(v_pdshortfalls);
1661 } else if (vmd->vmd_laundry_request !=
1662 VM_LAUNDRY_SHORTFALL)
1663 vmd->vmd_laundry_request =
1664 VM_LAUNDRY_BACKGROUND;
1665 wakeup(&vmd->vmd_laundry_request);
1667 vmd->vmd_clean_pages_freed +=
1668 starting_page_shortage - page_shortage;
1669 vm_pagequeue_unlock(pq);
1673 * Wakeup the swapout daemon if we didn't free the targeted number of
1676 if (page_shortage > 0)
1680 * If the inactive queue scan fails repeatedly to meet its
1681 * target, kill the largest process.
1683 vm_pageout_mightbe_oom(vmd, page_shortage, starting_page_shortage);
1686 * Reclaim pages by swapping out idle processes, if configured to do so.
1688 vm_swapout_run_idle();
1691 * See the description of addl_page_shortage above.
1693 *addl_shortage = addl_page_shortage + deficit;
1695 return (page_shortage <= 0);
1698 static int vm_pageout_oom_vote;
1701 * The pagedaemon threads randlomly select one to perform the
1702 * OOM. Trying to kill processes before all pagedaemons
1703 * failed to reach free target is premature.
1706 vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage,
1707 int starting_page_shortage)
1711 if (starting_page_shortage <= 0 || starting_page_shortage !=
1713 vmd->vmd_oom_seq = 0;
1716 if (vmd->vmd_oom_seq < vm_pageout_oom_seq) {
1718 vmd->vmd_oom = FALSE;
1719 atomic_subtract_int(&vm_pageout_oom_vote, 1);
1725 * Do not follow the call sequence until OOM condition is
1728 vmd->vmd_oom_seq = 0;
1733 vmd->vmd_oom = TRUE;
1734 old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1);
1735 if (old_vote != vm_ndomains - 1)
1739 * The current pagedaemon thread is the last in the quorum to
1740 * start OOM. Initiate the selection and signaling of the
1743 vm_pageout_oom(VM_OOM_MEM);
1746 * After one round of OOM terror, recall our vote. On the
1747 * next pass, current pagedaemon would vote again if the low
1748 * memory condition is still there, due to vmd_oom being
1751 vmd->vmd_oom = FALSE;
1752 atomic_subtract_int(&vm_pageout_oom_vote, 1);
1756 * The OOM killer is the page daemon's action of last resort when
1757 * memory allocation requests have been stalled for a prolonged period
1758 * of time because it cannot reclaim memory. This function computes
1759 * the approximate number of physical pages that could be reclaimed if
1760 * the specified address space is destroyed.
1762 * Private, anonymous memory owned by the address space is the
1763 * principal resource that we expect to recover after an OOM kill.
1764 * Since the physical pages mapped by the address space's COW entries
1765 * are typically shared pages, they are unlikely to be released and so
1766 * they are not counted.
1768 * To get to the point where the page daemon runs the OOM killer, its
1769 * efforts to write-back vnode-backed pages may have stalled. This
1770 * could be caused by a memory allocation deadlock in the write path
1771 * that might be resolved by an OOM kill. Therefore, physical pages
1772 * belonging to vnode-backed objects are counted, because they might
1773 * be freed without being written out first if the address space holds
1774 * the last reference to an unlinked vnode.
1776 * Similarly, physical pages belonging to OBJT_PHYS objects are
1777 * counted because the address space might hold the last reference to
1781 vm_pageout_oom_pagecount(struct vmspace *vmspace)
1784 vm_map_entry_t entry;
1788 map = &vmspace->vm_map;
1789 KASSERT(!map->system_map, ("system map"));
1790 sx_assert(&map->lock, SA_LOCKED);
1792 VM_MAP_ENTRY_FOREACH(entry, map) {
1793 if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
1795 obj = entry->object.vm_object;
1798 if ((entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0 &&
1799 obj->ref_count != 1)
1801 switch (obj->type) {
1806 res += obj->resident_page_count;
1813 static int vm_oom_ratelim_last;
1814 static int vm_oom_pf_secs = 10;
1815 SYSCTL_INT(_vm, OID_AUTO, oom_pf_secs, CTLFLAG_RWTUN, &vm_oom_pf_secs, 0,
1817 static struct mtx vm_oom_ratelim_mtx;
1820 vm_pageout_oom(int shortage)
1822 struct proc *p, *bigproc;
1823 vm_offset_t size, bigsize;
1830 * For OOM requests originating from vm_fault(), there is a high
1831 * chance that a single large process faults simultaneously in
1832 * several threads. Also, on an active system running many
1833 * processes of middle-size, like buildworld, all of them
1834 * could fault almost simultaneously as well.
1836 * To avoid killing too many processes, rate-limit OOMs
1837 * initiated by vm_fault() time-outs on the waits for free
1840 mtx_lock(&vm_oom_ratelim_mtx);
1842 if (shortage == VM_OOM_MEM_PF &&
1843 (u_int)(now - vm_oom_ratelim_last) < hz * vm_oom_pf_secs) {
1844 mtx_unlock(&vm_oom_ratelim_mtx);
1847 vm_oom_ratelim_last = now;
1848 mtx_unlock(&vm_oom_ratelim_mtx);
1851 * We keep the process bigproc locked once we find it to keep anyone
1852 * from messing with it; however, there is a possibility of
1853 * deadlock if process B is bigproc and one of its child processes
1854 * attempts to propagate a signal to B while we are waiting for A's
1855 * lock while walking this list. To avoid this, we don't block on
1856 * the process lock but just skip a process if it is already locked.
1860 sx_slock(&allproc_lock);
1861 FOREACH_PROC_IN_SYSTEM(p) {
1865 * If this is a system, protected or killed process, skip it.
1867 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC |
1868 P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 ||
1869 p->p_pid == 1 || P_KILLED(p) ||
1870 (p->p_pid < 48 && swap_pager_avail != 0)) {
1875 * If the process is in a non-running type state,
1876 * don't touch it. Check all the threads individually.
1879 FOREACH_THREAD_IN_PROC(p, td) {
1881 if (!TD_ON_RUNQ(td) &&
1882 !TD_IS_RUNNING(td) &&
1883 !TD_IS_SLEEPING(td) &&
1884 !TD_IS_SUSPENDED(td) &&
1885 !TD_IS_SWAPPED(td)) {
1897 * get the process size
1899 vm = vmspace_acquire_ref(p);
1906 sx_sunlock(&allproc_lock);
1907 if (!vm_map_trylock_read(&vm->vm_map)) {
1909 sx_slock(&allproc_lock);
1913 size = vmspace_swap_count(vm);
1914 if (shortage == VM_OOM_MEM || shortage == VM_OOM_MEM_PF)
1915 size += vm_pageout_oom_pagecount(vm);
1916 vm_map_unlock_read(&vm->vm_map);
1918 sx_slock(&allproc_lock);
1921 * If this process is bigger than the biggest one,
1924 if (size > bigsize) {
1925 if (bigproc != NULL)
1933 sx_sunlock(&allproc_lock);
1934 if (bigproc != NULL) {
1935 if (vm_panic_on_oom != 0 && --vm_panic_on_oom == 0)
1936 panic("out of swap space");
1938 killproc(bigproc, "out of swap space");
1939 sched_nice(bigproc, PRIO_MIN);
1941 PROC_UNLOCK(bigproc);
1946 * Signal a free page shortage to subsystems that have registered an event
1947 * handler. Reclaim memory from UMA in the event of a severe shortage.
1948 * Return true if the free page count should be re-evaluated.
1951 vm_pageout_lowmem(void)
1953 static int lowmem_ticks = 0;
1959 last = atomic_load_int(&lowmem_ticks);
1960 while ((u_int)(ticks - last) / hz >= lowmem_period) {
1961 if (atomic_fcmpset_int(&lowmem_ticks, &last, ticks) == 0)
1965 * Decrease registered cache sizes.
1967 SDT_PROBE0(vm, , , vm__lowmem_scan);
1968 EVENTHANDLER_INVOKE(vm_lowmem, VM_LOW_PAGES);
1971 * We do this explicitly after the caches have been
1974 uma_reclaim(UMA_RECLAIM_TRIM);
1980 * Kick off an asynchronous reclaim of cached memory if one of the
1981 * page daemons is failing to keep up with demand. Use the "severe"
1982 * threshold instead of "min" to ensure that we do not blow away the
1983 * caches if a subset of the NUMA domains are depleted by kernel memory
1984 * allocations; the domainset iterators automatically skip domains
1985 * below the "min" threshold on the first pass.
1987 * UMA reclaim worker has its own rate-limiting mechanism, so don't
1988 * worry about kicking it too often.
1990 if (vm_page_count_severe())
1991 uma_reclaim_wakeup();
1997 vm_pageout_worker(void *arg)
1999 struct vm_domain *vmd;
2001 int addl_shortage, domain, shortage;
2004 domain = (uintptr_t)arg;
2005 vmd = VM_DOMAIN(domain);
2010 * XXXKIB It could be useful to bind pageout daemon threads to
2011 * the cores belonging to the domain, from which vm_page_array
2015 KASSERT(vmd->vmd_segs != 0, ("domain without segments"));
2016 vmd->vmd_last_active_scan = ticks;
2019 * The pageout daemon worker is never done, so loop forever.
2022 vm_domain_pageout_lock(vmd);
2025 * We need to clear wanted before we check the limits. This
2026 * prevents races with wakers who will check wanted after they
2029 atomic_store_int(&vmd->vmd_pageout_wanted, 0);
2032 * Might the page daemon need to run again?
2034 if (vm_paging_needed(vmd, vmd->vmd_free_count)) {
2036 * Yes. If the scan failed to produce enough free
2037 * pages, sleep uninterruptibly for some time in the
2038 * hope that the laundry thread will clean some pages.
2040 vm_domain_pageout_unlock(vmd);
2042 pause("pwait", hz / VM_INACT_SCAN_RATE);
2045 * No, sleep until the next wakeup or until pages
2046 * need to have their reference stats updated.
2048 if (mtx_sleep(&vmd->vmd_pageout_wanted,
2049 vm_domain_pageout_lockptr(vmd), PDROP | PVM,
2050 "psleep", hz / VM_INACT_SCAN_RATE) == 0)
2051 VM_CNT_INC(v_pdwakeups);
2054 /* Prevent spurious wakeups by ensuring that wanted is set. */
2055 atomic_store_int(&vmd->vmd_pageout_wanted, 1);
2058 * Use the controller to calculate how many pages to free in
2059 * this interval, and scan the inactive queue. If the lowmem
2060 * handlers appear to have freed up some pages, subtract the
2061 * difference from the inactive queue scan target.
2063 shortage = pidctrl_daemon(&vmd->vmd_pid, vmd->vmd_free_count);
2065 ofree = vmd->vmd_free_count;
2066 if (vm_pageout_lowmem() && vmd->vmd_free_count > ofree)
2067 shortage -= min(vmd->vmd_free_count - ofree,
2069 target_met = vm_pageout_scan_inactive(vmd, shortage,
2075 * Scan the active queue. A positive value for shortage
2076 * indicates that we must aggressively deactivate pages to avoid
2079 shortage = vm_pageout_active_target(vmd) + addl_shortage;
2080 vm_pageout_scan_active(vmd, shortage);
2085 * Initialize basic pageout daemon settings. See the comment above the
2086 * definition of vm_domain for some explanation of how these thresholds are
2090 vm_pageout_init_domain(int domain)
2092 struct vm_domain *vmd;
2093 struct sysctl_oid *oid;
2095 vmd = VM_DOMAIN(domain);
2096 vmd->vmd_interrupt_free_min = 2;
2099 * v_free_reserved needs to include enough for the largest
2100 * swap pager structures plus enough for any pv_entry structs
2103 vmd->vmd_pageout_free_min = 2 * MAXBSIZE / PAGE_SIZE +
2104 vmd->vmd_interrupt_free_min;
2105 vmd->vmd_free_reserved = vm_pageout_page_count +
2106 vmd->vmd_pageout_free_min + vmd->vmd_page_count / 768;
2107 vmd->vmd_free_min = vmd->vmd_page_count / 200;
2108 vmd->vmd_free_severe = vmd->vmd_free_min / 2;
2109 vmd->vmd_free_target = 4 * vmd->vmd_free_min + vmd->vmd_free_reserved;
2110 vmd->vmd_free_min += vmd->vmd_free_reserved;
2111 vmd->vmd_free_severe += vmd->vmd_free_reserved;
2112 vmd->vmd_inactive_target = (3 * vmd->vmd_free_target) / 2;
2113 if (vmd->vmd_inactive_target > vmd->vmd_free_count / 3)
2114 vmd->vmd_inactive_target = vmd->vmd_free_count / 3;
2117 * Set the default wakeup threshold to be 10% below the paging
2118 * target. This keeps the steady state out of shortfall.
2120 vmd->vmd_pageout_wakeup_thresh = (vmd->vmd_free_target / 10) * 9;
2123 * Target amount of memory to move out of the laundry queue during a
2124 * background laundering. This is proportional to the amount of system
2127 vmd->vmd_background_launder_target = (vmd->vmd_free_target -
2128 vmd->vmd_free_min) / 10;
2130 /* Initialize the pageout daemon pid controller. */
2131 pidctrl_init(&vmd->vmd_pid, hz / VM_INACT_SCAN_RATE,
2132 vmd->vmd_free_target, PIDCTRL_BOUND,
2133 PIDCTRL_KPD, PIDCTRL_KID, PIDCTRL_KDD);
2134 oid = SYSCTL_ADD_NODE(NULL, SYSCTL_CHILDREN(vmd->vmd_oid), OID_AUTO,
2135 "pidctrl", CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");
2136 pidctrl_init_sysctl(&vmd->vmd_pid, SYSCTL_CHILDREN(oid));
2140 vm_pageout_init(void)
2146 * Initialize some paging parameters.
2148 if (vm_cnt.v_page_count < 2000)
2149 vm_pageout_page_count = 8;
2152 for (i = 0; i < vm_ndomains; i++) {
2153 struct vm_domain *vmd;
2155 vm_pageout_init_domain(i);
2157 vm_cnt.v_free_reserved += vmd->vmd_free_reserved;
2158 vm_cnt.v_free_target += vmd->vmd_free_target;
2159 vm_cnt.v_free_min += vmd->vmd_free_min;
2160 vm_cnt.v_inactive_target += vmd->vmd_inactive_target;
2161 vm_cnt.v_pageout_free_min += vmd->vmd_pageout_free_min;
2162 vm_cnt.v_interrupt_free_min += vmd->vmd_interrupt_free_min;
2163 vm_cnt.v_free_severe += vmd->vmd_free_severe;
2164 freecount += vmd->vmd_free_count;
2168 * Set interval in seconds for active scan. We want to visit each
2169 * page at least once every ten minutes. This is to prevent worst
2170 * case paging behaviors with stale active LRU.
2172 if (vm_pageout_update_period == 0)
2173 vm_pageout_update_period = 600;
2175 if (vm_page_max_user_wired == 0)
2176 vm_page_max_user_wired = freecount / 3;
2180 * vm_pageout is the high level pageout daemon.
2187 int error, first, i;
2192 mtx_init(&vm_oom_ratelim_mtx, "vmoomr", NULL, MTX_DEF);
2193 swap_pager_swap_init();
2194 for (first = -1, i = 0; i < vm_ndomains; i++) {
2195 if (VM_DOMAIN_EMPTY(i)) {
2197 printf("domain %d empty; skipping pageout\n",
2204 error = kthread_add(vm_pageout_worker,
2205 (void *)(uintptr_t)i, p, NULL, 0, 0, "dom%d", i);
2207 panic("starting pageout for domain %d: %d\n",
2210 error = kthread_add(vm_pageout_laundry_worker,
2211 (void *)(uintptr_t)i, p, NULL, 0, 0, "laundry: dom%d", i);
2213 panic("starting laundry for domain %d: %d", i, error);
2215 error = kthread_add(uma_reclaim_worker, NULL, p, NULL, 0, 0, "uma");
2217 panic("starting uma_reclaim helper, error %d\n", error);
2219 snprintf(td->td_name, sizeof(td->td_name), "dom%d", first);
2220 vm_pageout_worker((void *)(uintptr_t)first);
2224 * Perform an advisory wakeup of the page daemon.
2227 pagedaemon_wakeup(int domain)
2229 struct vm_domain *vmd;
2231 vmd = VM_DOMAIN(domain);
2232 vm_domain_pageout_assert_unlocked(vmd);
2233 if (curproc == pageproc)
2236 if (atomic_fetchadd_int(&vmd->vmd_pageout_wanted, 1) == 0) {
2237 vm_domain_pageout_lock(vmd);
2238 atomic_store_int(&vmd->vmd_pageout_wanted, 1);
2239 wakeup(&vmd->vmd_pageout_wanted);
2240 vm_domain_pageout_unlock(vmd);