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 out of memory 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_page_queue() must be used to
261 * determine whether the page has been logically dequeued by another thread.
262 * Once this check is performed, the page lock guarantees that the page will
263 * not be disassociated from the queue.
265 static __always_inline void
266 vm_pageout_collect_batch(struct scan_state *ss, const bool dequeue)
268 struct vm_pagequeue *pq;
269 vm_page_t m, marker, n;
274 KASSERT((marker->a.flags & PGA_ENQUEUED) != 0,
275 ("marker %p not enqueued", ss->marker));
277 vm_pagequeue_lock(pq);
278 for (m = TAILQ_NEXT(marker, plinks.q); m != NULL &&
279 ss->scanned < ss->maxscan && ss->bq.bq_cnt < VM_BATCHQUEUE_SIZE;
280 m = n, ss->scanned++) {
281 n = TAILQ_NEXT(m, plinks.q);
282 if ((m->flags & PG_MARKER) == 0) {
283 KASSERT((m->a.flags & PGA_ENQUEUED) != 0,
284 ("page %p not enqueued", m));
285 KASSERT((m->flags & PG_FICTITIOUS) == 0,
286 ("Fictitious page %p cannot be in page queue", m));
287 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
288 ("Unmanaged page %p cannot be in page queue", m));
292 (void)vm_batchqueue_insert(&ss->bq, m);
294 TAILQ_REMOVE(&pq->pq_pl, m, plinks.q);
295 vm_page_aflag_clear(m, PGA_ENQUEUED);
298 TAILQ_REMOVE(&pq->pq_pl, marker, plinks.q);
299 if (__predict_true(m != NULL))
300 TAILQ_INSERT_BEFORE(m, marker, plinks.q);
302 TAILQ_INSERT_TAIL(&pq->pq_pl, marker, plinks.q);
304 vm_pagequeue_cnt_add(pq, -ss->bq.bq_cnt);
305 vm_pagequeue_unlock(pq);
309 * Return the next page to be scanned, or NULL if the scan is complete.
311 static __always_inline vm_page_t
312 vm_pageout_next(struct scan_state *ss, const bool dequeue)
315 if (ss->bq.bq_cnt == 0)
316 vm_pageout_collect_batch(ss, dequeue);
317 return (vm_batchqueue_pop(&ss->bq));
321 * Determine whether processing of a page should be deferred and ensure that any
322 * outstanding queue operations are processed.
324 static __always_inline bool
325 vm_pageout_defer(vm_page_t m, const uint8_t queue, const bool enqueued)
329 as = vm_page_astate_load(m);
330 if (__predict_false(as.queue != queue ||
331 ((as.flags & PGA_ENQUEUED) != 0) != enqueued))
333 if ((as.flags & PGA_QUEUE_OP_MASK) != 0) {
334 vm_page_pqbatch_submit(m, queue);
341 * Scan for pages at adjacent offsets within the given page's object that are
342 * eligible for laundering, form a cluster of these pages and the given page,
343 * and launder that cluster.
346 vm_pageout_cluster(vm_page_t m)
349 vm_page_t mc[2 * vm_pageout_page_count], p, pb, ps;
351 int ib, is, page_base, pageout_count;
354 VM_OBJECT_ASSERT_WLOCKED(object);
357 vm_page_assert_xbusied(m);
359 mc[vm_pageout_page_count] = pb = ps = m;
361 page_base = vm_pageout_page_count;
366 * We can cluster only if the page is not clean, busy, or held, and
367 * the page is in the laundry queue.
369 * During heavy mmap/modification loads the pageout
370 * daemon can really fragment the underlying file
371 * due to flushing pages out of order and not trying to
372 * align the clusters (which leaves sporadic out-of-order
373 * holes). To solve this problem we do the reverse scan
374 * first and attempt to align our cluster, then do a
375 * forward scan if room remains.
378 while (ib != 0 && pageout_count < vm_pageout_page_count) {
383 if ((p = vm_page_prev(pb)) == NULL ||
384 vm_page_tryxbusy(p) == 0) {
388 if (vm_page_wired(p)) {
393 vm_page_test_dirty(p);
399 if (!vm_page_in_laundry(p) || !vm_page_try_remove_write(p)) {
404 mc[--page_base] = pb = p;
409 * We are at an alignment boundary. Stop here, and switch
410 * directions. Do not clear ib.
412 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
415 while (pageout_count < vm_pageout_page_count &&
416 pindex + is < object->size) {
417 if ((p = vm_page_next(ps)) == NULL ||
418 vm_page_tryxbusy(p) == 0)
420 if (vm_page_wired(p)) {
424 vm_page_test_dirty(p);
429 if (!vm_page_in_laundry(p) || !vm_page_try_remove_write(p)) {
433 mc[page_base + pageout_count] = ps = p;
439 * If we exhausted our forward scan, continue with the reverse scan
440 * when possible, even past an alignment boundary. This catches
441 * boundary conditions.
443 if (ib != 0 && pageout_count < vm_pageout_page_count)
446 return (vm_pageout_flush(&mc[page_base], pageout_count,
447 VM_PAGER_PUT_NOREUSE, 0, NULL, NULL));
451 * vm_pageout_flush() - launder the given pages
453 * The given pages are laundered. Note that we setup for the start of
454 * I/O ( i.e. busy the page ), mark it read-only, and bump the object
455 * reference count all in here rather then in the parent. If we want
456 * the parent to do more sophisticated things we may have to change
459 * Returned runlen is the count of pages between mreq and first
460 * page after mreq with status VM_PAGER_AGAIN.
461 * *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
462 * for any page in runlen set.
465 vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
468 vm_object_t object = mc[0]->object;
469 int pageout_status[count];
473 VM_OBJECT_ASSERT_WLOCKED(object);
476 * Initiate I/O. Mark the pages shared busy and verify that they're
477 * valid and read-only.
479 * We do not have to fixup the clean/dirty bits here... we can
480 * allow the pager to do it after the I/O completes.
482 * NOTE! mc[i]->dirty may be partial or fragmented due to an
483 * edge case with file fragments.
485 for (i = 0; i < count; i++) {
486 KASSERT(vm_page_all_valid(mc[i]),
487 ("vm_pageout_flush: partially invalid page %p index %d/%d",
489 KASSERT((mc[i]->a.flags & PGA_WRITEABLE) == 0,
490 ("vm_pageout_flush: writeable page %p", mc[i]));
491 vm_page_busy_downgrade(mc[i]);
493 vm_object_pip_add(object, count);
495 vm_pager_put_pages(object, mc, count, flags, pageout_status);
497 runlen = count - mreq;
500 for (i = 0; i < count; i++) {
501 vm_page_t mt = mc[i];
503 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
504 !pmap_page_is_write_mapped(mt),
505 ("vm_pageout_flush: page %p is not write protected", mt));
506 switch (pageout_status[i]) {
509 * The page may have moved since laundering started, in
510 * which case it should be left alone.
512 if (vm_page_in_laundry(mt))
513 vm_page_deactivate_noreuse(mt);
520 * The page is outside the object's range. We pretend
521 * that the page out worked and clean the page, so the
522 * changes will be lost if the page is reclaimed by
526 if (vm_page_in_laundry(mt))
527 vm_page_deactivate_noreuse(mt);
532 * If the page couldn't be paged out to swap because the
533 * pager wasn't able to find space, place the page in
534 * the PQ_UNSWAPPABLE holding queue. This is an
535 * optimization that prevents the page daemon from
536 * wasting CPU cycles on pages that cannot be reclaimed
537 * becase no swap device is configured.
539 * Otherwise, reactivate the page so that it doesn't
540 * clog the laundry and inactive queues. (We will try
541 * paging it out again later.)
543 if (object->type == OBJT_SWAP &&
544 pageout_status[i] == VM_PAGER_FAIL) {
545 vm_page_unswappable(mt);
548 vm_page_activate(mt);
549 if (eio != NULL && i >= mreq && i - mreq < runlen)
553 if (i >= mreq && i - mreq < runlen)
559 * If the operation is still going, leave the page busy to
560 * block all other accesses. Also, leave the paging in
561 * progress indicator set so that we don't attempt an object
564 if (pageout_status[i] != VM_PAGER_PEND) {
565 vm_object_pip_wakeup(object);
571 return (numpagedout);
575 vm_pageout_swapon(void *arg __unused, struct swdevt *sp __unused)
578 atomic_store_rel_int(&swapdev_enabled, 1);
582 vm_pageout_swapoff(void *arg __unused, struct swdevt *sp __unused)
585 if (swap_pager_nswapdev() == 1)
586 atomic_store_rel_int(&swapdev_enabled, 0);
590 * Attempt to acquire all of the necessary locks to launder a page and
591 * then call through the clustering layer to PUTPAGES. Wait a short
592 * time for a vnode lock.
594 * Requires the page and object lock on entry, releases both before return.
595 * Returns 0 on success and an errno otherwise.
598 vm_pageout_clean(vm_page_t m, int *numpagedout)
607 VM_OBJECT_ASSERT_WLOCKED(object);
613 * The object is already known NOT to be dead. It
614 * is possible for the vget() to block the whole
615 * pageout daemon, but the new low-memory handling
616 * code should prevent it.
618 * We can't wait forever for the vnode lock, we might
619 * deadlock due to a vn_read() getting stuck in
620 * vm_wait while holding this vnode. We skip the
621 * vnode if we can't get it in a reasonable amount
624 if (object->type == OBJT_VNODE) {
627 if (vp->v_type == VREG &&
628 vn_start_write(vp, &mp, V_NOWAIT) != 0) {
634 ("vp %p with NULL v_mount", vp));
635 vm_object_reference_locked(object);
637 VM_OBJECT_WUNLOCK(object);
638 lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
639 LK_SHARED : LK_EXCLUSIVE;
640 if (vget(vp, lockmode | LK_TIMELOCK, curthread)) {
645 VM_OBJECT_WLOCK(object);
648 * Ensure that the object and vnode were not disassociated
649 * while locks were dropped.
651 if (vp->v_object != object) {
657 * While the object was unlocked, the page may have been:
658 * (1) moved to a different queue,
659 * (2) reallocated to a different object,
660 * (3) reallocated to a different offset, or
663 if (!vm_page_in_laundry(m) || m->object != object ||
664 m->pindex != pindex || m->dirty == 0) {
670 * The page may have been busied while the object lock was
673 if (vm_page_tryxbusy(m) == 0) {
680 * Remove all writeable mappings, failing if the page is wired.
682 if (!vm_page_try_remove_write(m)) {
689 * If a page is dirty, then it is either being washed
690 * (but not yet cleaned) or it is still in the
691 * laundry. If it is still in the laundry, then we
692 * start the cleaning operation.
694 if ((*numpagedout = vm_pageout_cluster(m)) == 0)
698 VM_OBJECT_WUNLOCK(object);
704 vm_object_deallocate(object);
705 vn_finished_write(mp);
712 * Attempt to launder the specified number of pages.
714 * Returns the number of pages successfully laundered.
717 vm_pageout_launder(struct vm_domain *vmd, int launder, bool in_shortfall)
719 struct scan_state ss;
720 struct vm_pagequeue *pq;
723 vm_page_astate_t new, old;
724 int act_delta, error, numpagedout, queue, refs, starting_target;
729 starting_target = launder;
733 * Scan the laundry queues for pages eligible to be laundered. We stop
734 * once the target number of dirty pages have been laundered, or once
735 * we've reached the end of the queue. A single iteration of this loop
736 * may cause more than one page to be laundered because of clustering.
738 * As an optimization, we avoid laundering from PQ_UNSWAPPABLE when no
739 * swap devices are configured.
741 if (atomic_load_acq_int(&swapdev_enabled))
742 queue = PQ_UNSWAPPABLE;
747 marker = &vmd->vmd_markers[queue];
748 pq = &vmd->vmd_pagequeues[queue];
749 vm_pagequeue_lock(pq);
750 vm_pageout_init_scan(&ss, pq, marker, NULL, pq->pq_cnt);
751 while (launder > 0 && (m = vm_pageout_next(&ss, false)) != NULL) {
752 if (__predict_false((m->flags & PG_MARKER) != 0))
756 * Don't touch a page that was removed from the queue after the
757 * page queue lock was released. Otherwise, ensure that any
758 * pending queue operations, such as dequeues for wired pages,
761 if (vm_pageout_defer(m, queue, true))
765 * Lock the page's object.
767 if (object == NULL || object != m->object) {
769 VM_OBJECT_WUNLOCK(object);
770 object = (vm_object_t)atomic_load_ptr(&m->object);
771 if (__predict_false(object == NULL))
772 /* The page is being freed by another thread. */
775 /* Depends on type-stability. */
776 VM_OBJECT_WLOCK(object);
777 if (__predict_false(m->object != object)) {
778 VM_OBJECT_WUNLOCK(object);
784 if (vm_page_tryxbusy(m) == 0)
788 * Check for wirings now that we hold the object lock and have
789 * exclusively busied the page. If the page is mapped, it may
790 * still be wired by pmap lookups. The call to
791 * vm_page_try_remove_all() below atomically checks for such
792 * wirings and removes mappings. If the page is unmapped, the
793 * wire count is guaranteed not to increase after this check.
795 if (__predict_false(vm_page_wired(m)))
799 * Invalid pages can be easily freed. They cannot be
800 * mapped; vm_page_free() asserts this.
802 if (vm_page_none_valid(m))
805 refs = object->ref_count != 0 ? pmap_ts_referenced(m) : 0;
807 for (old = vm_page_astate_load(m);;) {
809 * Check to see if the page has been removed from the
810 * queue since the first such check. Leave it alone if
811 * so, discarding any references collected by
812 * pmap_ts_referenced().
814 if (__predict_false(_vm_page_queue(old) == PQ_NONE))
819 if ((old.flags & PGA_REFERENCED) != 0) {
820 new.flags &= ~PGA_REFERENCED;
823 if (act_delta == 0) {
825 } else if (object->ref_count != 0) {
827 * Increase the activation count if the page was
828 * referenced while in the laundry queue. This
829 * makes it less likely that the page will be
830 * returned prematurely to the laundry queue.
832 new.act_count += ACT_ADVANCE +
834 if (new.act_count > ACT_MAX)
835 new.act_count = ACT_MAX;
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 = (vm_object_t)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 old.queue = PQ_ACTIVE;
1317 old.flags |= PGA_REQUEUE;
1321 * When not short for inactive pages, let dirty
1322 * pages go through the inactive queue before
1323 * moving to the laundry queue. This gives them
1324 * some extra time to be reactivated,
1325 * potentially avoiding an expensive pageout.
1326 * However, during a page shortage, the inactive
1327 * queue is necessarily small, and so dirty
1328 * pages would only spend a trivial amount of
1329 * time in the inactive queue. Therefore, we
1330 * might as well place them directly in the
1331 * laundry queue to reduce queuing overhead.
1333 * Calling vm_page_test_dirty() here would
1334 * require acquisition of the object's write
1335 * lock. However, during a page shortage,
1336 * directing dirty pages into the laundry queue
1337 * is only an optimization and not a
1338 * requirement. Therefore, we simply rely on
1339 * the opportunistic updates to the page's dirty
1340 * field by the pmap.
1342 if (page_shortage <= 0) {
1343 nqueue = PQ_INACTIVE;
1345 } else if (m->dirty == 0) {
1346 nqueue = PQ_INACTIVE;
1347 ps_delta = act_scan_laundry_weight;
1349 nqueue = PQ_LAUNDRY;
1353 new.flags |= PGA_REQUEUE;
1356 } while (!vm_page_pqstate_commit(m, &old, new));
1358 page_shortage -= ps_delta;
1360 vm_pagequeue_lock(pq);
1361 TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_clock[0], plinks.q);
1362 TAILQ_INSERT_AFTER(&pq->pq_pl, marker, &vmd->vmd_clock[0], plinks.q);
1363 vm_pageout_end_scan(&ss);
1364 vm_pagequeue_unlock(pq);
1368 vm_pageout_reinsert_inactive_page(struct vm_pagequeue *pq, vm_page_t marker,
1371 vm_page_astate_t as;
1373 vm_pagequeue_assert_locked(pq);
1375 as = vm_page_astate_load(m);
1376 if (as.queue != PQ_INACTIVE || (as.flags & PGA_ENQUEUED) != 0)
1378 vm_page_aflag_set(m, PGA_ENQUEUED);
1379 TAILQ_INSERT_BEFORE(marker, m, plinks.q);
1384 * Re-add stuck pages to the inactive queue. We will examine them again
1385 * during the next scan. If the queue state of a page has changed since
1386 * it was physically removed from the page queue in
1387 * vm_pageout_collect_batch(), don't do anything with that page.
1390 vm_pageout_reinsert_inactive(struct scan_state *ss, struct vm_batchqueue *bq,
1393 struct vm_pagequeue *pq;
1398 marker = ss->marker;
1402 if (vm_batchqueue_insert(bq, m))
1404 vm_pagequeue_lock(pq);
1405 delta += vm_pageout_reinsert_inactive_page(pq, marker, m);
1407 vm_pagequeue_lock(pq);
1408 while ((m = vm_batchqueue_pop(bq)) != NULL)
1409 delta += vm_pageout_reinsert_inactive_page(pq, marker, m);
1410 vm_pagequeue_cnt_add(pq, delta);
1411 vm_pagequeue_unlock(pq);
1412 vm_batchqueue_init(bq);
1416 * Attempt to reclaim the requested number of pages from the inactive queue.
1417 * Returns true if the shortage was addressed.
1420 vm_pageout_scan_inactive(struct vm_domain *vmd, int shortage,
1423 struct scan_state ss;
1424 struct vm_batchqueue rq;
1425 vm_page_t m, marker;
1426 struct vm_pagequeue *pq;
1428 vm_page_astate_t old, new;
1429 int act_delta, addl_page_shortage, deficit, page_shortage, refs;
1430 int starting_page_shortage;
1433 * The addl_page_shortage is an estimate of the number of temporarily
1434 * stuck pages in the inactive queue. In other words, the
1435 * number of pages from the inactive count that should be
1436 * discounted in setting the target for the active queue scan.
1438 addl_page_shortage = 0;
1441 * vmd_pageout_deficit counts the number of pages requested in
1442 * allocations that failed because of a free page shortage. We assume
1443 * that the allocations will be reattempted and thus include the deficit
1444 * in our scan target.
1446 deficit = atomic_readandclear_int(&vmd->vmd_pageout_deficit);
1447 starting_page_shortage = page_shortage = shortage + deficit;
1450 vm_batchqueue_init(&rq);
1453 * Start scanning the inactive queue for pages that we can free. The
1454 * scan will stop when we reach the target or we have scanned the
1455 * entire queue. (Note that m->a.act_count is not used to make
1456 * decisions for the inactive queue, only for the active queue.)
1458 marker = &vmd->vmd_markers[PQ_INACTIVE];
1459 pq = &vmd->vmd_pagequeues[PQ_INACTIVE];
1460 vm_pagequeue_lock(pq);
1461 vm_pageout_init_scan(&ss, pq, marker, NULL, pq->pq_cnt);
1462 while (page_shortage > 0 && (m = vm_pageout_next(&ss, true)) != NULL) {
1463 KASSERT((m->flags & PG_MARKER) == 0,
1464 ("marker page %p was dequeued", m));
1467 * Don't touch a page that was removed from the queue after the
1468 * page queue lock was released. Otherwise, ensure that any
1469 * pending queue operations, such as dequeues for wired pages,
1472 if (vm_pageout_defer(m, PQ_INACTIVE, false))
1476 * Lock the page's object.
1478 if (object == NULL || object != m->object) {
1480 VM_OBJECT_WUNLOCK(object);
1481 object = (vm_object_t)atomic_load_ptr(&m->object);
1482 if (__predict_false(object == NULL))
1483 /* The page is being freed by another thread. */
1486 /* Depends on type-stability. */
1487 VM_OBJECT_WLOCK(object);
1488 if (__predict_false(m->object != object)) {
1489 VM_OBJECT_WUNLOCK(object);
1495 if (vm_page_tryxbusy(m) == 0) {
1497 * Don't mess with busy pages. Leave them at
1498 * the front of the queue. Most likely, they
1499 * are being paged out and will leave the
1500 * queue shortly after the scan finishes. So,
1501 * they ought to be discounted from the
1504 addl_page_shortage++;
1508 /* Deferred free of swap space. */
1509 if ((m->a.flags & PGA_SWAP_FREE) != 0)
1510 vm_pager_page_unswapped(m);
1513 * Check for wirings now that we hold the object lock and have
1514 * exclusively busied the page. If the page is mapped, it may
1515 * still be wired by pmap lookups. The call to
1516 * vm_page_try_remove_all() below atomically checks for such
1517 * wirings and removes mappings. If the page is unmapped, the
1518 * wire count is guaranteed not to increase after this check.
1520 if (__predict_false(vm_page_wired(m)))
1524 * Invalid pages can be easily freed. They cannot be
1525 * mapped, vm_page_free() asserts this.
1527 if (vm_page_none_valid(m))
1530 refs = object->ref_count != 0 ? pmap_ts_referenced(m) : 0;
1532 for (old = vm_page_astate_load(m);;) {
1534 * Check to see if the page has been removed from the
1535 * queue since the first such check. Leave it alone if
1536 * so, discarding any references collected by
1537 * pmap_ts_referenced().
1539 if (__predict_false(_vm_page_queue(old) == PQ_NONE))
1544 if ((old.flags & PGA_REFERENCED) != 0) {
1545 new.flags &= ~PGA_REFERENCED;
1548 if (act_delta == 0) {
1550 } else if (object->ref_count != 0) {
1552 * Increase the activation count if the
1553 * page was referenced while in the
1554 * inactive queue. This makes it less
1555 * likely that the page will be returned
1556 * prematurely to the inactive queue.
1558 new.act_count += ACT_ADVANCE +
1560 if (new.act_count > ACT_MAX)
1561 new.act_count = ACT_MAX;
1563 new.flags |= PGA_REQUEUE;
1564 new.queue = PQ_ACTIVE;
1565 if (!vm_page_pqstate_commit(m, &old, new))
1568 VM_CNT_INC(v_reactivated);
1570 } else if ((object->flags & OBJ_DEAD) == 0) {
1571 new.queue = PQ_INACTIVE;
1572 new.flags |= PGA_REQUEUE;
1573 if (!vm_page_pqstate_commit(m, &old, new))
1581 * If the page appears to be clean at the machine-independent
1582 * layer, then remove all of its mappings from the pmap in
1583 * anticipation of freeing it. If, however, any of the page's
1584 * mappings allow write access, then the page may still be
1585 * modified until the last of those mappings are removed.
1587 if (object->ref_count != 0) {
1588 vm_page_test_dirty(m);
1589 if (m->dirty == 0 && !vm_page_try_remove_all(m))
1594 * Clean pages can be freed, but dirty pages must be sent back
1595 * to the laundry, unless they belong to a dead object.
1596 * Requeueing dirty pages from dead objects is pointless, as
1597 * they are being paged out and freed by the thread that
1598 * destroyed the object.
1600 if (m->dirty == 0) {
1603 * Now we are guaranteed that no other threads are
1604 * manipulating the page, check for a last-second
1605 * reference that would save it from doom.
1607 if (vm_pageout_defer(m, PQ_INACTIVE, false))
1611 * Because we dequeued the page and have already checked
1612 * for pending dequeue and enqueue requests, we can
1613 * safely disassociate the page from the inactive queue
1614 * without holding the queue lock.
1616 m->a.queue = PQ_NONE;
1621 if ((object->flags & OBJ_DEAD) == 0)
1627 vm_pageout_reinsert_inactive(&ss, &rq, m);
1630 VM_OBJECT_WUNLOCK(object);
1631 vm_pageout_reinsert_inactive(&ss, &rq, NULL);
1632 vm_pageout_reinsert_inactive(&ss, &ss.bq, NULL);
1633 vm_pagequeue_lock(pq);
1634 vm_pageout_end_scan(&ss);
1635 vm_pagequeue_unlock(pq);
1637 VM_CNT_ADD(v_dfree, starting_page_shortage - page_shortage);
1640 * Wake up the laundry thread so that it can perform any needed
1641 * laundering. If we didn't meet our target, we're in shortfall and
1642 * need to launder more aggressively. If PQ_LAUNDRY is empty and no
1643 * swap devices are configured, the laundry thread has no work to do, so
1644 * don't bother waking it up.
1646 * The laundry thread uses the number of inactive queue scans elapsed
1647 * since the last laundering to determine whether to launder again, so
1650 if (starting_page_shortage > 0) {
1651 pq = &vmd->vmd_pagequeues[PQ_LAUNDRY];
1652 vm_pagequeue_lock(pq);
1653 if (vmd->vmd_laundry_request == VM_LAUNDRY_IDLE &&
1654 (pq->pq_cnt > 0 || atomic_load_acq_int(&swapdev_enabled))) {
1655 if (page_shortage > 0) {
1656 vmd->vmd_laundry_request = VM_LAUNDRY_SHORTFALL;
1657 VM_CNT_INC(v_pdshortfalls);
1658 } else if (vmd->vmd_laundry_request !=
1659 VM_LAUNDRY_SHORTFALL)
1660 vmd->vmd_laundry_request =
1661 VM_LAUNDRY_BACKGROUND;
1662 wakeup(&vmd->vmd_laundry_request);
1664 vmd->vmd_clean_pages_freed +=
1665 starting_page_shortage - page_shortage;
1666 vm_pagequeue_unlock(pq);
1670 * Wakeup the swapout daemon if we didn't free the targeted number of
1673 if (page_shortage > 0)
1677 * If the inactive queue scan fails repeatedly to meet its
1678 * target, kill the largest process.
1680 vm_pageout_mightbe_oom(vmd, page_shortage, starting_page_shortage);
1683 * Reclaim pages by swapping out idle processes, if configured to do so.
1685 vm_swapout_run_idle();
1688 * See the description of addl_page_shortage above.
1690 *addl_shortage = addl_page_shortage + deficit;
1692 return (page_shortage <= 0);
1695 static int vm_pageout_oom_vote;
1698 * The pagedaemon threads randlomly select one to perform the
1699 * OOM. Trying to kill processes before all pagedaemons
1700 * failed to reach free target is premature.
1703 vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage,
1704 int starting_page_shortage)
1708 if (starting_page_shortage <= 0 || starting_page_shortage !=
1710 vmd->vmd_oom_seq = 0;
1713 if (vmd->vmd_oom_seq < vm_pageout_oom_seq) {
1715 vmd->vmd_oom = FALSE;
1716 atomic_subtract_int(&vm_pageout_oom_vote, 1);
1722 * Do not follow the call sequence until OOM condition is
1725 vmd->vmd_oom_seq = 0;
1730 vmd->vmd_oom = TRUE;
1731 old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1);
1732 if (old_vote != vm_ndomains - 1)
1736 * The current pagedaemon thread is the last in the quorum to
1737 * start OOM. Initiate the selection and signaling of the
1740 vm_pageout_oom(VM_OOM_MEM);
1743 * After one round of OOM terror, recall our vote. On the
1744 * next pass, current pagedaemon would vote again if the low
1745 * memory condition is still there, due to vmd_oom being
1748 vmd->vmd_oom = FALSE;
1749 atomic_subtract_int(&vm_pageout_oom_vote, 1);
1753 * The OOM killer is the page daemon's action of last resort when
1754 * memory allocation requests have been stalled for a prolonged period
1755 * of time because it cannot reclaim memory. This function computes
1756 * the approximate number of physical pages that could be reclaimed if
1757 * the specified address space is destroyed.
1759 * Private, anonymous memory owned by the address space is the
1760 * principal resource that we expect to recover after an OOM kill.
1761 * Since the physical pages mapped by the address space's COW entries
1762 * are typically shared pages, they are unlikely to be released and so
1763 * they are not counted.
1765 * To get to the point where the page daemon runs the OOM killer, its
1766 * efforts to write-back vnode-backed pages may have stalled. This
1767 * could be caused by a memory allocation deadlock in the write path
1768 * that might be resolved by an OOM kill. Therefore, physical pages
1769 * belonging to vnode-backed objects are counted, because they might
1770 * be freed without being written out first if the address space holds
1771 * the last reference to an unlinked vnode.
1773 * Similarly, physical pages belonging to OBJT_PHYS objects are
1774 * counted because the address space might hold the last reference to
1778 vm_pageout_oom_pagecount(struct vmspace *vmspace)
1781 vm_map_entry_t entry;
1785 map = &vmspace->vm_map;
1786 KASSERT(!map->system_map, ("system map"));
1787 sx_assert(&map->lock, SA_LOCKED);
1789 VM_MAP_ENTRY_FOREACH(entry, map) {
1790 if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
1792 obj = entry->object.vm_object;
1795 if ((entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0 &&
1796 obj->ref_count != 1)
1798 switch (obj->type) {
1803 res += obj->resident_page_count;
1810 static int vm_oom_ratelim_last;
1811 static int vm_oom_pf_secs = 10;
1812 SYSCTL_INT(_vm, OID_AUTO, oom_pf_secs, CTLFLAG_RWTUN, &vm_oom_pf_secs, 0,
1814 static struct mtx vm_oom_ratelim_mtx;
1817 vm_pageout_oom(int shortage)
1819 struct proc *p, *bigproc;
1820 vm_offset_t size, bigsize;
1827 * For OOM requests originating from vm_fault(), there is a high
1828 * chance that a single large process faults simultaneously in
1829 * several threads. Also, on an active system running many
1830 * processes of middle-size, like buildworld, all of them
1831 * could fault almost simultaneously as well.
1833 * To avoid killing too many processes, rate-limit OOMs
1834 * initiated by vm_fault() time-outs on the waits for free
1837 mtx_lock(&vm_oom_ratelim_mtx);
1839 if (shortage == VM_OOM_MEM_PF &&
1840 (u_int)(now - vm_oom_ratelim_last) < hz * vm_oom_pf_secs) {
1841 mtx_unlock(&vm_oom_ratelim_mtx);
1844 vm_oom_ratelim_last = now;
1845 mtx_unlock(&vm_oom_ratelim_mtx);
1848 * We keep the process bigproc locked once we find it to keep anyone
1849 * from messing with it; however, there is a possibility of
1850 * deadlock if process B is bigproc and one of its child processes
1851 * attempts to propagate a signal to B while we are waiting for A's
1852 * lock while walking this list. To avoid this, we don't block on
1853 * the process lock but just skip a process if it is already locked.
1857 sx_slock(&allproc_lock);
1858 FOREACH_PROC_IN_SYSTEM(p) {
1862 * If this is a system, protected or killed process, skip it.
1864 if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC |
1865 P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 ||
1866 p->p_pid == 1 || P_KILLED(p) ||
1867 (p->p_pid < 48 && swap_pager_avail != 0)) {
1872 * If the process is in a non-running type state,
1873 * don't touch it. Check all the threads individually.
1876 FOREACH_THREAD_IN_PROC(p, td) {
1878 if (!TD_ON_RUNQ(td) &&
1879 !TD_IS_RUNNING(td) &&
1880 !TD_IS_SLEEPING(td) &&
1881 !TD_IS_SUSPENDED(td) &&
1882 !TD_IS_SWAPPED(td)) {
1894 * get the process size
1896 vm = vmspace_acquire_ref(p);
1903 sx_sunlock(&allproc_lock);
1904 if (!vm_map_trylock_read(&vm->vm_map)) {
1906 sx_slock(&allproc_lock);
1910 size = vmspace_swap_count(vm);
1911 if (shortage == VM_OOM_MEM || shortage == VM_OOM_MEM_PF)
1912 size += vm_pageout_oom_pagecount(vm);
1913 vm_map_unlock_read(&vm->vm_map);
1915 sx_slock(&allproc_lock);
1918 * If this process is bigger than the biggest one,
1921 if (size > bigsize) {
1922 if (bigproc != NULL)
1930 sx_sunlock(&allproc_lock);
1931 if (bigproc != NULL) {
1932 if (vm_panic_on_oom != 0)
1933 panic("out of swap space");
1935 killproc(bigproc, "out of swap space");
1936 sched_nice(bigproc, PRIO_MIN);
1938 PROC_UNLOCK(bigproc);
1943 * Signal a free page shortage to subsystems that have registered an event
1944 * handler. Reclaim memory from UMA in the event of a severe shortage.
1945 * Return true if the free page count should be re-evaluated.
1948 vm_pageout_lowmem(void)
1950 static int lowmem_ticks = 0;
1956 last = atomic_load_int(&lowmem_ticks);
1957 while ((u_int)(ticks - last) / hz >= lowmem_period) {
1958 if (atomic_fcmpset_int(&lowmem_ticks, &last, ticks) == 0)
1962 * Decrease registered cache sizes.
1964 SDT_PROBE0(vm, , , vm__lowmem_scan);
1965 EVENTHANDLER_INVOKE(vm_lowmem, VM_LOW_PAGES);
1968 * We do this explicitly after the caches have been
1971 uma_reclaim(UMA_RECLAIM_TRIM);
1976 * Kick off an asynchronous reclaim of cached memory if one of the
1977 * page daemons is failing to keep up with demand. Use the "severe"
1978 * threshold instead of "min" to ensure that we do not blow away the
1979 * caches if a subset of the NUMA domains are depleted by kernel memory
1980 * allocations; the domainset iterators automatically skip domains
1981 * below the "min" threshold on the first pass.
1983 * UMA reclaim worker has its own rate-limiting mechanism, so don't
1984 * worry about kicking it too often.
1986 if (vm_page_count_severe())
1987 uma_reclaim_wakeup();
1993 vm_pageout_worker(void *arg)
1995 struct vm_domain *vmd;
1997 int addl_shortage, domain, shortage;
2000 domain = (uintptr_t)arg;
2001 vmd = VM_DOMAIN(domain);
2006 * XXXKIB It could be useful to bind pageout daemon threads to
2007 * the cores belonging to the domain, from which vm_page_array
2011 KASSERT(vmd->vmd_segs != 0, ("domain without segments"));
2012 vmd->vmd_last_active_scan = ticks;
2015 * The pageout daemon worker is never done, so loop forever.
2018 vm_domain_pageout_lock(vmd);
2021 * We need to clear wanted before we check the limits. This
2022 * prevents races with wakers who will check wanted after they
2025 atomic_store_int(&vmd->vmd_pageout_wanted, 0);
2028 * Might the page daemon need to run again?
2030 if (vm_paging_needed(vmd, vmd->vmd_free_count)) {
2032 * Yes. If the scan failed to produce enough free
2033 * pages, sleep uninterruptibly for some time in the
2034 * hope that the laundry thread will clean some pages.
2036 vm_domain_pageout_unlock(vmd);
2038 pause("pwait", hz / VM_INACT_SCAN_RATE);
2041 * No, sleep until the next wakeup or until pages
2042 * need to have their reference stats updated.
2044 if (mtx_sleep(&vmd->vmd_pageout_wanted,
2045 vm_domain_pageout_lockptr(vmd), PDROP | PVM,
2046 "psleep", hz / VM_INACT_SCAN_RATE) == 0)
2047 VM_CNT_INC(v_pdwakeups);
2050 /* Prevent spurious wakeups by ensuring that wanted is set. */
2051 atomic_store_int(&vmd->vmd_pageout_wanted, 1);
2054 * Use the controller to calculate how many pages to free in
2055 * this interval, and scan the inactive queue. If the lowmem
2056 * handlers appear to have freed up some pages, subtract the
2057 * difference from the inactive queue scan target.
2059 shortage = pidctrl_daemon(&vmd->vmd_pid, vmd->vmd_free_count);
2061 ofree = vmd->vmd_free_count;
2062 if (vm_pageout_lowmem() && vmd->vmd_free_count > ofree)
2063 shortage -= min(vmd->vmd_free_count - ofree,
2065 target_met = vm_pageout_scan_inactive(vmd, shortage,
2071 * Scan the active queue. A positive value for shortage
2072 * indicates that we must aggressively deactivate pages to avoid
2075 shortage = vm_pageout_active_target(vmd) + addl_shortage;
2076 vm_pageout_scan_active(vmd, shortage);
2081 * Initialize basic pageout daemon settings. See the comment above the
2082 * definition of vm_domain for some explanation of how these thresholds are
2086 vm_pageout_init_domain(int domain)
2088 struct vm_domain *vmd;
2089 struct sysctl_oid *oid;
2091 vmd = VM_DOMAIN(domain);
2092 vmd->vmd_interrupt_free_min = 2;
2095 * v_free_reserved needs to include enough for the largest
2096 * swap pager structures plus enough for any pv_entry structs
2099 vmd->vmd_pageout_free_min = 2 * MAXBSIZE / PAGE_SIZE +
2100 vmd->vmd_interrupt_free_min;
2101 vmd->vmd_free_reserved = vm_pageout_page_count +
2102 vmd->vmd_pageout_free_min + vmd->vmd_page_count / 768;
2103 vmd->vmd_free_min = vmd->vmd_page_count / 200;
2104 vmd->vmd_free_severe = vmd->vmd_free_min / 2;
2105 vmd->vmd_free_target = 4 * vmd->vmd_free_min + vmd->vmd_free_reserved;
2106 vmd->vmd_free_min += vmd->vmd_free_reserved;
2107 vmd->vmd_free_severe += vmd->vmd_free_reserved;
2108 vmd->vmd_inactive_target = (3 * vmd->vmd_free_target) / 2;
2109 if (vmd->vmd_inactive_target > vmd->vmd_free_count / 3)
2110 vmd->vmd_inactive_target = vmd->vmd_free_count / 3;
2113 * Set the default wakeup threshold to be 10% below the paging
2114 * target. This keeps the steady state out of shortfall.
2116 vmd->vmd_pageout_wakeup_thresh = (vmd->vmd_free_target / 10) * 9;
2119 * Target amount of memory to move out of the laundry queue during a
2120 * background laundering. This is proportional to the amount of system
2123 vmd->vmd_background_launder_target = (vmd->vmd_free_target -
2124 vmd->vmd_free_min) / 10;
2126 /* Initialize the pageout daemon pid controller. */
2127 pidctrl_init(&vmd->vmd_pid, hz / VM_INACT_SCAN_RATE,
2128 vmd->vmd_free_target, PIDCTRL_BOUND,
2129 PIDCTRL_KPD, PIDCTRL_KID, PIDCTRL_KDD);
2130 oid = SYSCTL_ADD_NODE(NULL, SYSCTL_CHILDREN(vmd->vmd_oid), OID_AUTO,
2131 "pidctrl", CTLFLAG_RD, NULL, "");
2132 pidctrl_init_sysctl(&vmd->vmd_pid, SYSCTL_CHILDREN(oid));
2136 vm_pageout_init(void)
2142 * Initialize some paging parameters.
2144 if (vm_cnt.v_page_count < 2000)
2145 vm_pageout_page_count = 8;
2148 for (i = 0; i < vm_ndomains; i++) {
2149 struct vm_domain *vmd;
2151 vm_pageout_init_domain(i);
2153 vm_cnt.v_free_reserved += vmd->vmd_free_reserved;
2154 vm_cnt.v_free_target += vmd->vmd_free_target;
2155 vm_cnt.v_free_min += vmd->vmd_free_min;
2156 vm_cnt.v_inactive_target += vmd->vmd_inactive_target;
2157 vm_cnt.v_pageout_free_min += vmd->vmd_pageout_free_min;
2158 vm_cnt.v_interrupt_free_min += vmd->vmd_interrupt_free_min;
2159 vm_cnt.v_free_severe += vmd->vmd_free_severe;
2160 freecount += vmd->vmd_free_count;
2164 * Set interval in seconds for active scan. We want to visit each
2165 * page at least once every ten minutes. This is to prevent worst
2166 * case paging behaviors with stale active LRU.
2168 if (vm_pageout_update_period == 0)
2169 vm_pageout_update_period = 600;
2171 if (vm_page_max_user_wired == 0)
2172 vm_page_max_user_wired = freecount / 3;
2176 * vm_pageout is the high level pageout daemon.
2183 int error, first, i;
2188 mtx_init(&vm_oom_ratelim_mtx, "vmoomr", NULL, MTX_DEF);
2189 swap_pager_swap_init();
2190 for (first = -1, i = 0; i < vm_ndomains; i++) {
2191 if (VM_DOMAIN_EMPTY(i)) {
2193 printf("domain %d empty; skipping pageout\n",
2200 error = kthread_add(vm_pageout_worker,
2201 (void *)(uintptr_t)i, p, NULL, 0, 0, "dom%d", i);
2203 panic("starting pageout for domain %d: %d\n",
2206 error = kthread_add(vm_pageout_laundry_worker,
2207 (void *)(uintptr_t)i, p, NULL, 0, 0, "laundry: dom%d", i);
2209 panic("starting laundry for domain %d: %d", i, error);
2211 error = kthread_add(uma_reclaim_worker, NULL, p, NULL, 0, 0, "uma");
2213 panic("starting uma_reclaim helper, error %d\n", error);
2215 snprintf(td->td_name, sizeof(td->td_name), "dom%d", first);
2216 vm_pageout_worker((void *)(uintptr_t)first);
2220 * Perform an advisory wakeup of the page daemon.
2223 pagedaemon_wakeup(int domain)
2225 struct vm_domain *vmd;
2227 vmd = VM_DOMAIN(domain);
2228 vm_domain_pageout_assert_unlocked(vmd);
2229 if (curproc == pageproc)
2232 if (atomic_fetchadd_int(&vmd->vmd_pageout_wanted, 1) == 0) {
2233 vm_domain_pageout_lock(vmd);
2234 atomic_store_int(&vmd->vmd_pageout_wanted, 1);
2235 wakeup(&vmd->vmd_pageout_wanted);
2236 vm_domain_pageout_unlock(vmd);