4 * Copyright (c) 1991 Regents of the University of California.
6 * Copyright (c) 1994 John S. Dyson
8 * Copyright (c) 1994 David Greenman
11 * This code is derived from software contributed to Berkeley by
12 * The Mach Operating System project at Carnegie-Mellon University.
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * 2. Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in the
21 * documentation and/or other materials provided with the distribution.
22 * 4. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
24 * without specific prior written permission.
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
41 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
42 * All rights reserved.
44 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
46 * Permission to use, copy, modify and distribute this software and
47 * its documentation is hereby granted, provided that both the copyright
48 * notice and this permission notice appear in all copies of the
49 * software, derivative works or modified versions, and any portions
50 * thereof, and that both notices appear in supporting documentation.
52 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
53 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
54 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
56 * Carnegie Mellon requests users of this software to return to
58 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
59 * School of Computer Science
60 * Carnegie Mellon University
61 * Pittsburgh PA 15213-3890
63 * any improvements or extensions that they make and grant Carnegie the
64 * rights to redistribute these changes.
66 * $FreeBSD: src/sys/vm/vm_pageout.c,v 1.151.2.15 2002/12/29 18:21:04 dillon Exp $
70 * The proverbial page-out daemon.
74 #include <sys/param.h>
75 #include <sys/systm.h>
76 #include <sys/kernel.h>
78 #include <sys/kthread.h>
79 #include <sys/resourcevar.h>
80 #include <sys/signalvar.h>
81 #include <sys/vnode.h>
82 #include <sys/vmmeter.h>
83 #include <sys/sysctl.h>
86 #include <vm/vm_param.h>
88 #include <vm/vm_object.h>
89 #include <vm/vm_page.h>
90 #include <vm/vm_map.h>
91 #include <vm/vm_pageout.h>
92 #include <vm/vm_pager.h>
93 #include <vm/swap_pager.h>
94 #include <vm/vm_extern.h>
96 #include <sys/thread2.h>
97 #include <sys/spinlock2.h>
98 #include <vm/vm_page2.h>
101 * System initialization
104 /* the kernel process "vm_pageout"*/
105 static int vm_pageout_clean (vm_page_t);
106 static int vm_pageout_free_page_calc (vm_size_t count);
107 struct thread *pagethread;
109 #if !defined(NO_SWAPPING)
110 /* the kernel process "vm_daemon"*/
111 static void vm_daemon (void);
112 static struct thread *vmthread;
114 static struct kproc_desc vm_kp = {
119 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp)
123 int vm_pages_needed=0; /* Event on which pageout daemon sleeps */
124 int vm_pageout_deficit=0; /* Estimated number of pages deficit */
125 int vm_pageout_pages_needed=0; /* flag saying that the pageout daemon needs pages */
127 #if !defined(NO_SWAPPING)
128 static int vm_pageout_req_swapout; /* XXX */
129 static int vm_daemon_needed;
131 static int vm_max_launder = 32;
132 static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0;
133 static int vm_pageout_full_stats_interval = 0;
134 static int vm_pageout_stats_free_max=0, vm_pageout_algorithm=0;
135 static int defer_swap_pageouts=0;
136 static int disable_swap_pageouts=0;
138 #if defined(NO_SWAPPING)
139 static int vm_swap_enabled=0;
140 static int vm_swap_idle_enabled=0;
142 static int vm_swap_enabled=1;
143 static int vm_swap_idle_enabled=0;
146 SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm,
147 CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt");
149 SYSCTL_INT(_vm, OID_AUTO, max_launder,
150 CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
152 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max,
153 CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length");
155 SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval,
156 CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan");
158 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval,
159 CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan");
161 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_free_max,
162 CTLFLAG_RW, &vm_pageout_stats_free_max, 0, "Not implemented");
164 #if defined(NO_SWAPPING)
165 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
166 CTLFLAG_RD, &vm_swap_enabled, 0, "");
167 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
168 CTLFLAG_RD, &vm_swap_idle_enabled, 0, "");
170 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
171 CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
172 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
173 CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
176 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
177 CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
179 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
180 CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
182 static int pageout_lock_miss;
183 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
184 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
186 #define VM_PAGEOUT_PAGE_COUNT 16
187 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
189 int vm_page_max_wired; /* XXX max # of wired pages system-wide */
191 #if !defined(NO_SWAPPING)
192 typedef void freeer_fcn_t (vm_map_t, vm_object_t, vm_pindex_t, int);
193 static void vm_pageout_map_deactivate_pages (vm_map_t, vm_pindex_t);
194 static freeer_fcn_t vm_pageout_object_deactivate_pages;
195 static void vm_req_vmdaemon (void);
197 static void vm_pageout_page_stats(int q);
202 * Clean the page and remove it from the laundry. The page must not be
205 * We set the busy bit to cause potential page faults on this page to
206 * block. Note the careful timing, however, the busy bit isn't set till
207 * late and we cannot do anything that will mess with the page.
210 vm_pageout_clean(vm_page_t m)
213 vm_page_t mc[2*vm_pageout_page_count];
216 int ib, is, page_base;
217 vm_pindex_t pindex = m->pindex;
222 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
223 * with the new swapper, but we could have serious problems paging
224 * out other object types if there is insufficient memory.
226 * Unfortunately, checking free memory here is far too late, so the
227 * check has been moved up a procedural level.
231 * Don't mess with the page if it's busy, held, or special
233 * XXX do we really need to check hold_count here? hold_count
234 * isn't supposed to mess with vm_page ops except prevent the
235 * page from being reused.
237 if (m->hold_count != 0 || (m->flags & PG_UNMANAGED)) {
242 mc[vm_pageout_page_count] = m;
244 page_base = vm_pageout_page_count;
249 * Scan object for clusterable pages.
251 * We can cluster ONLY if: ->> the page is NOT
252 * clean, wired, busy, held, or mapped into a
253 * buffer, and one of the following:
254 * 1) The page is inactive, or a seldom used
257 * 2) we force the issue.
259 * During heavy mmap/modification loads the pageout
260 * daemon can really fragment the underlying file
261 * due to flushing pages out of order and not trying
262 * align the clusters (which leave sporatic out-of-order
263 * holes). To solve this problem we do the reverse scan
264 * first and attempt to align our cluster, then do a
265 * forward scan if room remains.
268 vm_object_hold(object);
270 while (ib && pageout_count < vm_pageout_page_count) {
278 p = vm_page_lookup_busy_try(object, pindex - ib, TRUE, &error);
279 if (error || p == NULL) {
283 if ((p->queue - p->pc) == PQ_CACHE ||
284 (p->flags & PG_UNMANAGED)) {
289 vm_page_test_dirty(p);
290 if ((p->dirty & p->valid) == 0 ||
291 p->queue - p->pc != PQ_INACTIVE ||
292 p->wire_count != 0 || /* may be held by buf cache */
293 p->hold_count != 0) { /* may be undergoing I/O */
302 * alignment boundry, stop here and switch directions. Do
305 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
309 while (pageout_count < vm_pageout_page_count &&
310 pindex + is < object->size) {
313 p = vm_page_lookup_busy_try(object, pindex + is, TRUE, &error);
314 if (error || p == NULL)
316 if (((p->queue - p->pc) == PQ_CACHE) ||
317 (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) {
321 vm_page_test_dirty(p);
322 if ((p->dirty & p->valid) == 0 ||
323 p->queue - p->pc != PQ_INACTIVE ||
324 p->wire_count != 0 || /* may be held by buf cache */
325 p->hold_count != 0) { /* may be undergoing I/O */
329 mc[page_base + pageout_count] = p;
335 * If we exhausted our forward scan, continue with the reverse scan
336 * when possible, even past a page boundry. This catches boundry
339 if (ib && pageout_count < vm_pageout_page_count)
342 vm_object_drop(object);
345 * we allow reads during pageouts...
347 return vm_pageout_flush(&mc[page_base], pageout_count, 0);
351 * vm_pageout_flush() - launder the given pages
353 * The given pages are laundered. Note that we setup for the start of
354 * I/O ( i.e. busy the page ), mark it read-only, and bump the object
355 * reference count all in here rather then in the parent. If we want
356 * the parent to do more sophisticated things we may have to change
359 * The pages in the array must be busied by the caller and will be
360 * unbusied by this function.
363 vm_pageout_flush(vm_page_t *mc, int count, int flags)
366 int pageout_status[count];
371 * Initiate I/O. Bump the vm_page_t->busy counter.
373 for (i = 0; i < count; i++) {
374 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
375 ("vm_pageout_flush page %p index %d/%d: partially "
376 "invalid page", mc[i], i, count));
377 vm_page_io_start(mc[i]);
381 * We must make the pages read-only. This will also force the
382 * modified bit in the related pmaps to be cleared. The pager
383 * cannot clear the bit for us since the I/O completion code
384 * typically runs from an interrupt. The act of making the page
385 * read-only handles the case for us.
387 * Then we can unbusy the pages, we still hold a reference by virtue
390 for (i = 0; i < count; i++) {
391 vm_page_protect(mc[i], VM_PROT_READ);
392 vm_page_wakeup(mc[i]);
395 object = mc[0]->object;
396 vm_object_pip_add(object, count);
398 vm_pager_put_pages(object, mc, count,
399 (flags | ((object == &kernel_object) ? VM_PAGER_PUT_SYNC : 0)),
402 for (i = 0; i < count; i++) {
403 vm_page_t mt = mc[i];
405 switch (pageout_status[i]) {
414 * Page outside of range of object. Right now we
415 * essentially lose the changes by pretending it
418 vm_page_busy_wait(mt, FALSE, "pgbad");
419 pmap_clear_modify(mt);
426 * A page typically cannot be paged out when we
427 * have run out of swap. We leave the page
428 * marked inactive and will try to page it out
431 * Starvation of the active page list is used to
432 * determine when the system is massively memory
441 * If the operation is still going, leave the page busy to
442 * block all other accesses. Also, leave the paging in
443 * progress indicator set so that we don't attempt an object
446 * For any pages which have completed synchronously,
447 * deactivate the page if we are under a severe deficit.
448 * Do not try to enter them into the cache, though, they
449 * might still be read-heavy.
451 if (pageout_status[i] != VM_PAGER_PEND) {
452 vm_page_busy_wait(mt, FALSE, "pgouw");
453 if (vm_page_count_severe())
454 vm_page_deactivate(mt);
456 if (!vm_page_count_severe() || !vm_page_try_to_cache(mt))
457 vm_page_protect(mt, VM_PROT_READ);
459 vm_page_io_finish(mt);
461 vm_object_pip_wakeup(object);
467 #if !defined(NO_SWAPPING)
469 * deactivate enough pages to satisfy the inactive target
470 * requirements or if vm_page_proc_limit is set, then
471 * deactivate all of the pages in the object and its
474 * The map must be locked.
475 * The caller must hold the vm_object.
477 static int vm_pageout_object_deactivate_pages_callback(vm_page_t, void *);
480 vm_pageout_object_deactivate_pages(vm_map_t map, vm_object_t object,
481 vm_pindex_t desired, int map_remove_only)
483 struct rb_vm_page_scan_info info;
488 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
492 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
494 if (lobject->type == OBJT_DEVICE || lobject->type == OBJT_PHYS)
496 if (lobject->paging_in_progress)
499 remove_mode = map_remove_only;
500 if (lobject->shadow_count > 1)
504 * scan the objects entire memory queue. We hold the
505 * object's token so the scan should not race anything.
507 info.limit = remove_mode;
509 info.desired = desired;
510 vm_page_rb_tree_RB_SCAN(&lobject->rb_memq, NULL,
511 vm_pageout_object_deactivate_pages_callback,
514 while ((tobject = lobject->backing_object) != NULL) {
515 KKASSERT(tobject != object);
516 vm_object_hold(tobject);
517 if (tobject == lobject->backing_object)
519 vm_object_drop(tobject);
521 if (lobject != object) {
522 vm_object_lock_swap();
523 vm_object_drop(lobject);
527 if (lobject != object)
528 vm_object_drop(lobject);
532 * The caller must hold the vm_object.
535 vm_pageout_object_deactivate_pages_callback(vm_page_t p, void *data)
537 struct rb_vm_page_scan_info *info = data;
540 if (pmap_resident_count(vm_map_pmap(info->map)) <= info->desired) {
543 mycpu->gd_cnt.v_pdpages++;
545 if (vm_page_busy_try(p, TRUE))
547 if (p->wire_count || p->hold_count || (p->flags & PG_UNMANAGED)) {
551 if (!pmap_page_exists_quick(vm_map_pmap(info->map), p)) {
556 actcount = pmap_ts_referenced(p);
558 vm_page_flag_set(p, PG_REFERENCED);
559 } else if (p->flags & PG_REFERENCED) {
563 vm_page_and_queue_spin_lock(p);
564 if (p->queue - p->pc != PQ_ACTIVE && (p->flags & PG_REFERENCED)) {
565 vm_page_and_queue_spin_unlock(p);
567 p->act_count += actcount;
568 vm_page_flag_clear(p, PG_REFERENCED);
569 } else if (p->queue - p->pc == PQ_ACTIVE) {
570 if ((p->flags & PG_REFERENCED) == 0) {
571 p->act_count -= min(p->act_count, ACT_DECLINE);
573 (vm_pageout_algorithm || (p->act_count == 0))) {
574 vm_page_and_queue_spin_unlock(p);
575 vm_page_protect(p, VM_PROT_NONE);
576 vm_page_deactivate(p);
578 TAILQ_REMOVE(&vm_page_queues[p->queue].pl,
580 TAILQ_INSERT_TAIL(&vm_page_queues[p->queue].pl,
582 vm_page_and_queue_spin_unlock(p);
585 vm_page_and_queue_spin_unlock(p);
587 vm_page_flag_clear(p, PG_REFERENCED);
589 vm_page_and_queue_spin_lock(p);
590 if (p->queue - p->pc == PQ_ACTIVE) {
591 if (p->act_count < (ACT_MAX - ACT_ADVANCE))
592 p->act_count += ACT_ADVANCE;
593 TAILQ_REMOVE(&vm_page_queues[p->queue].pl,
595 TAILQ_INSERT_TAIL(&vm_page_queues[p->queue].pl,
598 vm_page_and_queue_spin_unlock(p);
600 } else if (p->queue - p->pc == PQ_INACTIVE) {
601 vm_page_and_queue_spin_unlock(p);
602 vm_page_protect(p, VM_PROT_NONE);
604 vm_page_and_queue_spin_unlock(p);
611 * Deactivate some number of pages in a map, try to do it fairly, but
612 * that is really hard to do.
615 vm_pageout_map_deactivate_pages(vm_map_t map, vm_pindex_t desired)
618 vm_object_t obj, bigobj;
621 if (lockmgr(&map->lock, LK_EXCLUSIVE | LK_NOWAIT)) {
629 * first, search out the biggest object, and try to free pages from
632 tmpe = map->header.next;
633 while (tmpe != &map->header) {
634 switch(tmpe->maptype) {
635 case VM_MAPTYPE_NORMAL:
636 case VM_MAPTYPE_VPAGETABLE:
637 obj = tmpe->object.vm_object;
638 if ((obj != NULL) && (obj->shadow_count <= 1) &&
640 (bigobj->resident_page_count < obj->resident_page_count))) {
647 if (tmpe->wired_count > 0)
648 nothingwired = FALSE;
653 vm_object_hold(bigobj);
654 vm_pageout_object_deactivate_pages(map, bigobj, desired, 0);
655 vm_object_drop(bigobj);
659 * Next, hunt around for other pages to deactivate. We actually
660 * do this search sort of wrong -- .text first is not the best idea.
662 tmpe = map->header.next;
663 while (tmpe != &map->header) {
664 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
666 switch(tmpe->maptype) {
667 case VM_MAPTYPE_NORMAL:
668 case VM_MAPTYPE_VPAGETABLE:
669 obj = tmpe->object.vm_object;
672 vm_pageout_object_deactivate_pages(map, obj, desired, 0);
683 * Remove all mappings if a process is swapped out, this will free page
686 if (desired == 0 && nothingwired)
687 pmap_remove(vm_map_pmap(map),
688 VM_MIN_USER_ADDRESS, VM_MAX_USER_ADDRESS);
694 * Called when the pageout scan wants to free a page. We no longer
695 * try to cycle the vm_object here with a reference & dealloc, which can
696 * cause a non-trivial object collapse in a critical path.
698 * It is unclear why we cycled the ref_count in the past, perhaps to try
699 * to optimize shadow chain collapses but I don't quite see why it would
700 * be necessary. An OBJ_DEAD object should terminate any and all vm_pages
701 * synchronously and not have to be kicked-start.
704 vm_pageout_page_free(vm_page_t m)
706 vm_page_protect(m, VM_PROT_NONE);
711 * vm_pageout_scan does the dirty work for the pageout daemon.
713 struct vm_pageout_scan_info {
714 struct proc *bigproc;
718 static int vm_pageout_scan_callback(struct proc *p, void *data);
721 vm_pageout_scan_inactive(int pass, int q, int inactive_shortage,
722 int *vnodes_skippedp)
725 struct vm_page marker;
726 struct vnode *vpfailed; /* warning, allowed to be stale */
734 * Start scanning the inactive queue for pages we can move to the
735 * cache or free. The scan will stop when the target is reached or
736 * we have scanned the entire inactive queue. Note that m->act_count
737 * is not used to form decisions for the inactive queue, only for the
740 * maxlaunder limits the number of dirty pages we flush per scan.
741 * For most systems a smaller value (16 or 32) is more robust under
742 * extreme memory and disk pressure because any unnecessary writes
743 * to disk can result in extreme performance degredation. However,
744 * systems with excessive dirty pages (especially when MAP_NOSYNC is
745 * used) will die horribly with limited laundering. If the pageout
746 * daemon cannot clean enough pages in the first pass, we let it go
747 * all out in succeeding passes.
749 if ((maxlaunder = vm_max_launder) <= 1)
755 * Initialize our marker
757 bzero(&marker, sizeof(marker));
758 marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
759 marker.queue = PQ_INACTIVE + q;
761 marker.wire_count = 1;
764 * Inactive queue scan.
766 * NOTE: The vm_page must be spinlocked before the queue to avoid
767 * deadlocks, so it is easiest to simply iterate the loop
768 * with the queue unlocked at the top.
772 vm_page_queues_spin_lock(PQ_INACTIVE + q);
773 TAILQ_INSERT_HEAD(&vm_page_queues[PQ_INACTIVE + q].pl, &marker, pageq);
774 maxscan = vmstats.v_inactive_count;
775 vm_page_queues_spin_unlock(PQ_INACTIVE + q);
777 while ((m = TAILQ_NEXT(&marker, pageq)) != NULL &&
778 maxscan-- > 0 && inactive_shortage - delta > 0)
780 vm_page_and_queue_spin_lock(m);
781 if (m != TAILQ_NEXT(&marker, pageq)) {
782 vm_page_and_queue_spin_unlock(m);
786 KKASSERT(m->queue - m->pc == PQ_INACTIVE);
787 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE + q].pl,
789 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE + q].pl, m,
791 mycpu->gd_cnt.v_pdpages++;
796 if (m->flags & PG_MARKER) {
797 vm_page_and_queue_spin_unlock(m);
802 * Try to busy the page. Don't mess with pages which are
803 * already busy or reorder them in the queue.
805 if (vm_page_busy_try(m, TRUE)) {
806 vm_page_and_queue_spin_unlock(m);
809 vm_page_and_queue_spin_unlock(m);
810 KKASSERT(m->queue - m->pc == PQ_INACTIVE);
815 * The page has been successfully busied and is now no
816 * longer spinlocked. The queue is no longer spinlocked
821 * It is possible for a page to be busied ad-hoc (e.g. the
822 * pmap_collect() code) and wired and race against the
823 * allocation of a new page. vm_page_alloc() may be forced
824 * to deactivate the wired page in which case it winds up
825 * on the inactive queue and must be handled here. We
826 * correct the problem simply by unqueuing the page.
829 vm_page_unqueue_nowakeup(m);
831 kprintf("WARNING: pagedaemon: wired page on "
832 "inactive queue %p\n", m);
837 * A held page may be undergoing I/O, so skip it.
840 vm_page_and_queue_spin_lock(m);
841 if (m->queue - m->pc == PQ_INACTIVE) {
843 &vm_page_queues[PQ_INACTIVE + q].pl,
846 &vm_page_queues[PQ_INACTIVE + q].pl,
849 vm_page_and_queue_spin_unlock(m);
850 ++vm_swapcache_inactive_heuristic;
855 if (m->object->ref_count == 0) {
857 * If the object is not being used, we ignore previous
860 vm_page_flag_clear(m, PG_REFERENCED);
861 pmap_clear_reference(m);
862 /* fall through to end */
863 } else if (((m->flags & PG_REFERENCED) == 0) &&
864 (actcount = pmap_ts_referenced(m))) {
866 * Otherwise, if the page has been referenced while
867 * in the inactive queue, we bump the "activation
868 * count" upwards, making it less likely that the
869 * page will be added back to the inactive queue
870 * prematurely again. Here we check the page tables
871 * (or emulated bits, if any), given the upper level
872 * VM system not knowing anything about existing
876 m->act_count += (actcount + ACT_ADVANCE);
882 * (m) is still busied.
884 * If the upper level VM system knows about any page
885 * references, we activate the page. We also set the
886 * "activation count" higher than normal so that we will less
887 * likely place pages back onto the inactive queue again.
889 if ((m->flags & PG_REFERENCED) != 0) {
890 vm_page_flag_clear(m, PG_REFERENCED);
891 actcount = pmap_ts_referenced(m);
893 m->act_count += (actcount + ACT_ADVANCE + 1);
899 * If the upper level VM system doesn't know anything about
900 * the page being dirty, we have to check for it again. As
901 * far as the VM code knows, any partially dirty pages are
904 * Pages marked PG_WRITEABLE may be mapped into the user
905 * address space of a process running on another cpu. A
906 * user process (without holding the MP lock) running on
907 * another cpu may be able to touch the page while we are
908 * trying to remove it. vm_page_cache() will handle this
912 vm_page_test_dirty(m);
919 * Invalid pages can be easily freed
921 vm_pageout_page_free(m);
922 mycpu->gd_cnt.v_dfree++;
924 } else if (m->dirty == 0) {
926 * Clean pages can be placed onto the cache queue.
927 * This effectively frees them.
931 } else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) {
933 * Dirty pages need to be paged out, but flushing
934 * a page is extremely expensive verses freeing
935 * a clean page. Rather then artificially limiting
936 * the number of pages we can flush, we instead give
937 * dirty pages extra priority on the inactive queue
938 * by forcing them to be cycled through the queue
939 * twice before being flushed, after which the
940 * (now clean) page will cycle through once more
941 * before being freed. This significantly extends
942 * the thrash point for a heavily loaded machine.
944 vm_page_flag_set(m, PG_WINATCFLS);
945 vm_page_and_queue_spin_lock(m);
946 if (m->queue - m->pc == PQ_INACTIVE) {
948 &vm_page_queues[PQ_INACTIVE + q].pl,
951 &vm_page_queues[PQ_INACTIVE + q].pl,
954 vm_page_and_queue_spin_unlock(m);
955 ++vm_swapcache_inactive_heuristic;
957 } else if (maxlaunder > 0) {
959 * We always want to try to flush some dirty pages if
960 * we encounter them, to keep the system stable.
961 * Normally this number is small, but under extreme
962 * pressure where there are insufficient clean pages
963 * on the inactive queue, we may have to go all out.
965 int swap_pageouts_ok;
966 struct vnode *vp = NULL;
970 if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
971 swap_pageouts_ok = 1;
973 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
974 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
975 vm_page_count_min(0));
980 * We don't bother paging objects that are "dead".
981 * Those objects are in a "rundown" state.
983 if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
984 vm_page_and_queue_spin_lock(m);
985 if (m->queue - m->pc == PQ_INACTIVE) {
987 &vm_page_queues[PQ_INACTIVE + q].pl,
990 &vm_page_queues[PQ_INACTIVE + q].pl,
993 vm_page_and_queue_spin_unlock(m);
994 ++vm_swapcache_inactive_heuristic;
1000 * (m) is still busied.
1002 * The object is already known NOT to be dead. It
1003 * is possible for the vget() to block the whole
1004 * pageout daemon, but the new low-memory handling
1005 * code should prevent it.
1007 * The previous code skipped locked vnodes and, worse,
1008 * reordered pages in the queue. This results in
1009 * completely non-deterministic operation because,
1010 * quite often, a vm_fault has initiated an I/O and
1011 * is holding a locked vnode at just the point where
1012 * the pageout daemon is woken up.
1014 * We can't wait forever for the vnode lock, we might
1015 * deadlock due to a vn_read() getting stuck in
1016 * vm_wait while holding this vnode. We skip the
1017 * vnode if we can't get it in a reasonable amount
1020 * vpfailed is used to (try to) avoid the case where
1021 * a large number of pages are associated with a
1022 * locked vnode, which could cause the pageout daemon
1023 * to stall for an excessive amount of time.
1025 if (object->type == OBJT_VNODE) {
1028 vp = object->handle;
1029 flags = LK_EXCLUSIVE | LK_NOOBJ;
1033 flags |= LK_TIMELOCK;
1038 * We have unbusied (m) temporarily so we can
1039 * acquire the vp lock without deadlocking.
1040 * (m) is held to prevent destruction.
1042 if (vget(vp, flags) != 0) {
1044 ++pageout_lock_miss;
1045 if (object->flags & OBJ_MIGHTBEDIRTY)
1052 * The page might have been moved to another
1053 * queue during potential blocking in vget()
1054 * above. The page might have been freed and
1055 * reused for another vnode. The object might
1056 * have been reused for another vnode.
1058 if (m->queue - m->pc != PQ_INACTIVE ||
1059 m->object != object ||
1060 object->handle != vp) {
1061 if (object->flags & OBJ_MIGHTBEDIRTY)
1069 * The page may have been busied during the
1070 * blocking in vput(); We don't move the
1071 * page back onto the end of the queue so that
1072 * statistics are more correct if we don't.
1074 if (vm_page_busy_try(m, TRUE)) {
1082 * (m) is busied again
1084 * We own the busy bit and remove our hold
1085 * bit. If the page is still held it
1086 * might be undergoing I/O, so skip it.
1088 if (m->hold_count) {
1089 vm_page_and_queue_spin_lock(m);
1090 if (m->queue - m->pc == PQ_INACTIVE) {
1091 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE + q].pl, m, pageq);
1092 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE + q].pl, m, pageq);
1094 vm_page_and_queue_spin_unlock(m);
1095 ++vm_swapcache_inactive_heuristic;
1096 if (object->flags & OBJ_MIGHTBEDIRTY)
1102 /* (m) is left busied as we fall through */
1106 * page is busy and not held here.
1108 * If a page is dirty, then it is either being washed
1109 * (but not yet cleaned) or it is still in the
1110 * laundry. If it is still in the laundry, then we
1111 * start the cleaning operation.
1113 * decrement inactive_shortage on success to account
1114 * for the (future) cleaned page. Otherwise we
1115 * could wind up laundering or cleaning too many
1118 if (vm_pageout_clean(m) != 0) {
1122 /* clean ate busy, page no longer accessible */
1129 vm_page_queues_spin_lock(PQ_INACTIVE + q);
1130 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE + q].pl, &marker, pageq);
1131 vm_page_queues_spin_unlock(PQ_INACTIVE + q);
1137 vm_pageout_scan_active(int pass, int q,
1138 int inactive_shortage, int active_shortage,
1139 int *recycle_countp)
1141 struct vm_page marker;
1148 * We want to move pages from the active queue to the inactive
1149 * queue to get the inactive queue to the inactive target. If
1150 * we still have a page shortage from above we try to directly free
1151 * clean pages instead of moving them.
1153 * If we do still have a shortage we keep track of the number of
1154 * pages we free or cache (recycle_count) as a measure of thrashing
1155 * between the active and inactive queues.
1157 * If we were able to completely satisfy the free+cache targets
1158 * from the inactive pool we limit the number of pages we move
1159 * from the active pool to the inactive pool to 2x the pages we
1160 * had removed from the inactive pool (with a minimum of 1/5 the
1161 * inactive target). If we were not able to completely satisfy
1162 * the free+cache targets we go for the whole target aggressively.
1164 * NOTE: Both variables can end up negative.
1165 * NOTE: We are still in a critical section.
1168 bzero(&marker, sizeof(marker));
1169 marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
1170 marker.queue = PQ_ACTIVE + q;
1172 marker.wire_count = 1;
1174 vm_page_queues_spin_lock(PQ_ACTIVE + q);
1175 TAILQ_INSERT_HEAD(&vm_page_queues[PQ_ACTIVE + q].pl, &marker, pageq);
1176 vm_page_queues_spin_unlock(PQ_ACTIVE + q);
1177 pcount = vmstats.v_active_count;
1179 while ((m = TAILQ_NEXT(&marker, pageq)) != NULL &&
1180 pcount-- > 0 && (inactive_shortage - delta > 0 ||
1181 active_shortage > 0))
1183 vm_page_and_queue_spin_lock(m);
1184 if (m != TAILQ_NEXT(&marker, pageq)) {
1185 vm_page_and_queue_spin_unlock(m);
1189 KKASSERT(m->queue - m->pc == PQ_ACTIVE);
1190 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE + q].pl,
1192 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_ACTIVE + q].pl, m,
1198 if (m->flags & PG_MARKER) {
1199 vm_page_and_queue_spin_unlock(m);
1204 * Try to busy the page. Don't mess with pages which are
1205 * already busy or reorder them in the queue.
1207 if (vm_page_busy_try(m, TRUE)) {
1208 vm_page_and_queue_spin_unlock(m);
1213 * Don't deactivate pages that are held, even if we can
1214 * busy them. (XXX why not?)
1216 if (m->hold_count != 0) {
1217 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE + q].pl,
1219 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE + q].pl,
1221 vm_page_and_queue_spin_unlock(m);
1225 vm_page_and_queue_spin_unlock(m);
1229 * The page has been successfully busied and the page and
1230 * queue are no longer locked.
1234 * The count for pagedaemon pages is done after checking the
1235 * page for eligibility...
1237 mycpu->gd_cnt.v_pdpages++;
1240 * Check to see "how much" the page has been used and clear
1241 * the tracking access bits. If the object has no references
1242 * don't bother paying the expense.
1245 if (m->object->ref_count != 0) {
1246 if (m->flags & PG_REFERENCED)
1248 actcount += pmap_ts_referenced(m);
1250 m->act_count += ACT_ADVANCE + actcount;
1251 if (m->act_count > ACT_MAX)
1252 m->act_count = ACT_MAX;
1255 vm_page_flag_clear(m, PG_REFERENCED);
1258 * actcount is only valid if the object ref_count is non-zero.
1260 if (actcount && m->object->ref_count != 0) {
1261 vm_page_and_queue_spin_lock(m);
1262 if (m->queue - m->pc == PQ_ACTIVE) {
1264 &vm_page_queues[PQ_ACTIVE + q].pl,
1267 &vm_page_queues[PQ_ACTIVE + q].pl,
1270 vm_page_and_queue_spin_unlock(m);
1273 m->act_count -= min(m->act_count, ACT_DECLINE);
1274 if (vm_pageout_algorithm ||
1275 m->object->ref_count == 0 ||
1276 m->act_count < pass + 1
1279 * Deactivate the page. If we had a
1280 * shortage from our inactive scan try to
1281 * free (cache) the page instead.
1283 * Don't just blindly cache the page if
1284 * we do not have a shortage from the
1285 * inactive scan, that could lead to
1286 * gigabytes being moved.
1289 if (inactive_shortage - delta > 0 ||
1290 m->object->ref_count == 0) {
1291 if (inactive_shortage - delta > 0)
1293 vm_page_protect(m, VM_PROT_NONE);
1294 if (m->dirty == 0 &&
1295 inactive_shortage - delta > 0) {
1299 vm_page_deactivate(m);
1303 vm_page_deactivate(m);
1307 vm_page_and_queue_spin_lock(m);
1308 if (m->queue - m->pc == PQ_ACTIVE) {
1310 &vm_page_queues[PQ_ACTIVE + q].pl,
1313 &vm_page_queues[PQ_ACTIVE + q].pl,
1316 vm_page_and_queue_spin_unlock(m);
1323 * Clean out our local marker.
1325 vm_page_queues_spin_lock(PQ_ACTIVE + q);
1326 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE + q].pl, &marker, pageq);
1327 vm_page_queues_spin_unlock(PQ_ACTIVE + q);
1333 * The number of actually free pages can drop down to v_free_reserved,
1334 * we try to build the free count back above v_free_min. Note that
1335 * vm_paging_needed() also returns TRUE if v_free_count is not at
1336 * least v_free_min so that is the minimum we must build the free
1339 * We use a slightly higher target to improve hysteresis,
1340 * ((v_free_target + v_free_min) / 2). Since v_free_target
1341 * is usually the same as v_cache_min this maintains about
1342 * half the pages in the free queue as are in the cache queue,
1343 * providing pretty good pipelining for pageout operation.
1345 * The system operator can manipulate vm.v_cache_min and
1346 * vm.v_free_target to tune the pageout demon. Be sure
1347 * to keep vm.v_free_min < vm.v_free_target.
1349 * Note that the original paging target is to get at least
1350 * (free_min + cache_min) into (free + cache). The slightly
1351 * higher target will shift additional pages from cache to free
1352 * without effecting the original paging target in order to
1353 * maintain better hysteresis and not have the free count always
1354 * be dead-on v_free_min.
1356 * NOTE: we are still in a critical section.
1358 * Pages moved from PQ_CACHE to totally free are not counted in the
1359 * pages_freed counter.
1362 vm_pageout_scan_cache(int inactive_shortage,
1363 int vnodes_skipped, int recycle_count)
1365 struct vm_pageout_scan_info info;
1368 while (vmstats.v_free_count <
1369 (vmstats.v_free_min + vmstats.v_free_target) / 2) {
1371 * This steals some code from vm/vm_page.c
1373 static int cache_rover = 0;
1375 m = vm_page_list_find(PQ_CACHE, cache_rover & PQ_L2_MASK, FALSE);
1378 /* page is returned removed from its queue and spinlocked */
1379 if (vm_page_busy_try(m, TRUE)) {
1380 vm_page_deactivate_locked(m);
1381 vm_page_spin_unlock(m);
1383 kprintf("Warning: busy page %p found in cache\n", m);
1387 vm_page_spin_unlock(m);
1388 pagedaemon_wakeup();
1392 * Page has been successfully busied and it and its queue
1393 * is no longer spinlocked.
1395 if ((m->flags & PG_UNMANAGED) ||
1398 vm_page_deactivate(m);
1402 KKASSERT((m->flags & PG_MAPPED) == 0);
1403 KKASSERT(m->dirty == 0);
1404 cache_rover += PQ_PRIME2;
1405 vm_pageout_page_free(m);
1406 mycpu->gd_cnt.v_dfree++;
1409 #if !defined(NO_SWAPPING)
1411 * Idle process swapout -- run once per second.
1413 if (vm_swap_idle_enabled) {
1415 if (time_second != lsec) {
1416 vm_pageout_req_swapout |= VM_SWAP_IDLE;
1424 * If we didn't get enough free pages, and we have skipped a vnode
1425 * in a writeable object, wakeup the sync daemon. And kick swapout
1426 * if we did not get enough free pages.
1428 if (vm_paging_target() > 0) {
1429 if (vnodes_skipped && vm_page_count_min(0))
1431 #if !defined(NO_SWAPPING)
1432 if (vm_swap_enabled && vm_page_count_target()) {
1434 vm_pageout_req_swapout |= VM_SWAP_NORMAL;
1440 * Handle catastrophic conditions. Under good conditions we should
1441 * be at the target, well beyond our minimum. If we could not even
1442 * reach our minimum the system is under heavy stress.
1444 * Determine whether we have run out of memory. This occurs when
1445 * swap_pager_full is TRUE and the only pages left in the page
1446 * queues are dirty. We will still likely have page shortages.
1448 * - swap_pager_full is set if insufficient swap was
1449 * available to satisfy a requested pageout.
1451 * - the inactive queue is bloated (4 x size of active queue),
1452 * meaning it is unable to get rid of dirty pages and.
1454 * - vm_page_count_min() without counting pages recycled from the
1455 * active queue (recycle_count) means we could not recover
1456 * enough pages to meet bare minimum needs. This test only
1457 * works if the inactive queue is bloated.
1459 * - due to a positive inactive_shortage we shifted the remaining
1460 * dirty pages from the active queue to the inactive queue
1461 * trying to find clean ones to free.
1463 if (swap_pager_full && vm_page_count_min(recycle_count))
1464 kprintf("Warning: system low on memory+swap!\n");
1465 if (swap_pager_full && vm_page_count_min(recycle_count) &&
1466 vmstats.v_inactive_count > vmstats.v_active_count * 4 &&
1467 inactive_shortage > 0) {
1471 info.bigproc = NULL;
1473 allproc_scan(vm_pageout_scan_callback, &info);
1474 if (info.bigproc != NULL) {
1475 killproc(info.bigproc, "out of swap space");
1476 info.bigproc->p_nice = PRIO_MIN;
1477 info.bigproc->p_usched->resetpriority(
1478 FIRST_LWP_IN_PROC(info.bigproc));
1479 wakeup(&vmstats.v_free_count);
1480 PRELE(info.bigproc);
1486 * The caller must hold proc_token.
1489 vm_pageout_scan_callback(struct proc *p, void *data)
1491 struct vm_pageout_scan_info *info = data;
1495 * Never kill system processes or init. If we have configured swap
1496 * then try to avoid killing low-numbered pids.
1498 if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) ||
1499 ((p->p_pid < 48) && (vm_swap_size != 0))) {
1504 * if the process is in a non-running type state,
1507 if (p->p_stat != SACTIVE && p->p_stat != SSTOP)
1511 * Get the approximate process size. Note that anonymous pages
1512 * with backing swap will be counted twice, but there should not
1513 * be too many such pages due to the stress the VM system is
1514 * under at this point.
1516 size = vmspace_anonymous_count(p->p_vmspace) +
1517 vmspace_swap_count(p->p_vmspace);
1520 * If the this process is bigger than the biggest one
1523 if (info->bigsize < size) {
1525 PRELE(info->bigproc);
1528 info->bigsize = size;
1535 * This routine tries to maintain the pseudo LRU active queue,
1536 * so that during long periods of time where there is no paging,
1537 * that some statistic accumulation still occurs. This code
1538 * helps the situation where paging just starts to occur.
1541 vm_pageout_page_stats(int q)
1543 static int fullintervalcount = 0;
1544 struct vm_page marker;
1546 int pcount, tpcount; /* Number of pages to check */
1549 page_shortage = (vmstats.v_inactive_target + vmstats.v_cache_max +
1550 vmstats.v_free_min) -
1551 (vmstats.v_free_count + vmstats.v_inactive_count +
1552 vmstats.v_cache_count);
1554 if (page_shortage <= 0)
1557 pcount = vmstats.v_active_count;
1558 fullintervalcount += vm_pageout_stats_interval;
1559 if (fullintervalcount < vm_pageout_full_stats_interval) {
1560 tpcount = (vm_pageout_stats_max * vmstats.v_active_count) /
1561 vmstats.v_page_count;
1562 if (pcount > tpcount)
1565 fullintervalcount = 0;
1568 bzero(&marker, sizeof(marker));
1569 marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
1570 marker.queue = PQ_ACTIVE + q;
1572 marker.wire_count = 1;
1574 vm_page_queues_spin_lock(PQ_ACTIVE + q);
1575 TAILQ_INSERT_HEAD(&vm_page_queues[PQ_ACTIVE + q].pl, &marker, pageq);
1576 vm_page_queues_spin_unlock(PQ_ACTIVE + q);
1578 while ((m = TAILQ_NEXT(&marker, pageq)) != NULL &&
1583 vm_page_and_queue_spin_lock(m);
1584 if (m != TAILQ_NEXT(&marker, pageq)) {
1585 vm_page_and_queue_spin_unlock(m);
1589 KKASSERT(m->queue - m->pc == PQ_ACTIVE);
1590 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE + q].pl, &marker, pageq);
1591 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_ACTIVE + q].pl, m,
1597 if (m->flags & PG_MARKER) {
1598 vm_page_and_queue_spin_unlock(m);
1603 * Ignore pages we can't busy
1605 if (vm_page_busy_try(m, TRUE)) {
1606 vm_page_and_queue_spin_unlock(m);
1609 vm_page_and_queue_spin_unlock(m);
1610 KKASSERT(m->queue - m->pc == PQ_ACTIVE);
1613 * We now have a safely busied page, the page and queue
1614 * spinlocks have been released.
1618 if (m->hold_count) {
1624 * Calculate activity
1627 if (m->flags & PG_REFERENCED) {
1628 vm_page_flag_clear(m, PG_REFERENCED);
1631 actcount += pmap_ts_referenced(m);
1634 * Update act_count and move page to end of queue.
1637 m->act_count += ACT_ADVANCE + actcount;
1638 if (m->act_count > ACT_MAX)
1639 m->act_count = ACT_MAX;
1640 vm_page_and_queue_spin_lock(m);
1641 if (m->queue - m->pc == PQ_ACTIVE) {
1643 &vm_page_queues[PQ_ACTIVE + q].pl,
1646 &vm_page_queues[PQ_ACTIVE + q].pl,
1649 vm_page_and_queue_spin_unlock(m);
1654 if (m->act_count == 0) {
1656 * We turn off page access, so that we have
1657 * more accurate RSS stats. We don't do this
1658 * in the normal page deactivation when the
1659 * system is loaded VM wise, because the
1660 * cost of the large number of page protect
1661 * operations would be higher than the value
1662 * of doing the operation.
1664 * We use the marker to save our place so
1665 * we can release the spin lock. both (m)
1666 * and (next) will be invalid.
1668 vm_page_protect(m, VM_PROT_NONE);
1669 vm_page_deactivate(m);
1671 m->act_count -= min(m->act_count, ACT_DECLINE);
1672 vm_page_and_queue_spin_lock(m);
1673 if (m->queue - m->pc == PQ_ACTIVE) {
1675 &vm_page_queues[PQ_ACTIVE + q].pl,
1678 &vm_page_queues[PQ_ACTIVE + q].pl,
1681 vm_page_and_queue_spin_unlock(m);
1687 * Remove our local marker
1689 vm_page_queues_spin_lock(PQ_ACTIVE + q);
1690 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE + q].pl, &marker, pageq);
1691 vm_page_queues_spin_unlock(PQ_ACTIVE + q);
1695 vm_pageout_free_page_calc(vm_size_t count)
1697 if (count < vmstats.v_page_count)
1700 * free_reserved needs to include enough for the largest swap pager
1701 * structures plus enough for any pv_entry structs when paging.
1703 * v_free_min normal allocations
1704 * v_free_reserved system allocations
1705 * v_pageout_free_min allocations by pageout daemon
1706 * v_interrupt_free_min low level allocations (e.g swap structures)
1708 if (vmstats.v_page_count > 1024)
1709 vmstats.v_free_min = 64 + (vmstats.v_page_count - 1024) / 200;
1711 vmstats.v_free_min = 64;
1712 vmstats.v_free_reserved = vmstats.v_free_min * 4 / 8 + 7;
1713 vmstats.v_free_severe = vmstats.v_free_min * 4 / 8 + 0;
1714 vmstats.v_pageout_free_min = vmstats.v_free_min * 2 / 8 + 7;
1715 vmstats.v_interrupt_free_min = vmstats.v_free_min * 1 / 8 + 7;
1722 * vm_pageout is the high level pageout daemon.
1727 vm_pageout_thread(void)
1733 * Initialize some paging parameters.
1735 curthread->td_flags |= TDF_SYSTHREAD;
1737 if (vmstats.v_page_count < 2000)
1738 vm_pageout_page_count = 8;
1740 vm_pageout_free_page_calc(vmstats.v_page_count);
1743 * v_free_target and v_cache_min control pageout hysteresis. Note
1744 * that these are more a measure of the VM cache queue hysteresis
1745 * then the VM free queue. Specifically, v_free_target is the
1746 * high water mark (free+cache pages).
1748 * v_free_reserved + v_cache_min (mostly means v_cache_min) is the
1749 * low water mark, while v_free_min is the stop. v_cache_min must
1750 * be big enough to handle memory needs while the pageout daemon
1751 * is signalled and run to free more pages.
1753 if (vmstats.v_free_count > 6144)
1754 vmstats.v_free_target = 4 * vmstats.v_free_min + vmstats.v_free_reserved;
1756 vmstats.v_free_target = 2 * vmstats.v_free_min + vmstats.v_free_reserved;
1759 * NOTE: With the new buffer cache b_act_count we want the default
1760 * inactive target to be a percentage of available memory.
1762 * The inactive target essentially determines the minimum
1763 * number of 'temporary' pages capable of caching one-time-use
1764 * files when the VM system is otherwise full of pages
1765 * belonging to multi-time-use files or active program data.
1767 * NOTE: The inactive target is aggressively persued only if the
1768 * inactive queue becomes too small. If the inactive queue
1769 * is large enough to satisfy page movement to free+cache
1770 * then it is repopulated more slowly from the active queue.
1771 * This allows a general inactive_target default to be set.
1773 * There is an issue here for processes which sit mostly idle
1774 * 'overnight', such as sshd, tcsh, and X. Any movement from
1775 * the active queue will eventually cause such pages to
1776 * recycle eventually causing a lot of paging in the morning.
1777 * To reduce the incidence of this pages cycled out of the
1778 * buffer cache are moved directly to the inactive queue if
1779 * they were only used once or twice.
1781 * The vfs.vm_cycle_point sysctl can be used to adjust this.
1782 * Increasing the value (up to 64) increases the number of
1783 * buffer recyclements which go directly to the inactive queue.
1785 if (vmstats.v_free_count > 2048) {
1786 vmstats.v_cache_min = vmstats.v_free_target;
1787 vmstats.v_cache_max = 2 * vmstats.v_cache_min;
1789 vmstats.v_cache_min = 0;
1790 vmstats.v_cache_max = 0;
1792 vmstats.v_inactive_target = vmstats.v_free_count / 4;
1794 /* XXX does not really belong here */
1795 if (vm_page_max_wired == 0)
1796 vm_page_max_wired = vmstats.v_free_count / 3;
1798 if (vm_pageout_stats_max == 0)
1799 vm_pageout_stats_max = vmstats.v_free_target;
1802 * Set interval in seconds for stats scan.
1804 if (vm_pageout_stats_interval == 0)
1805 vm_pageout_stats_interval = 5;
1806 if (vm_pageout_full_stats_interval == 0)
1807 vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
1811 * Set maximum free per pass
1813 if (vm_pageout_stats_free_max == 0)
1814 vm_pageout_stats_free_max = 5;
1816 swap_pager_swap_init();
1820 * The pageout daemon is never done, so loop forever.
1826 int inactive_shortage;
1827 int active_shortage;
1828 int vnodes_skipped = 0;
1829 int recycle_count = 0;
1833 * Wait for an action request. If we timeout check to
1834 * see if paging is needed (in case the normal wakeup
1837 if (vm_pages_needed == 0) {
1838 error = tsleep(&vm_pages_needed,
1840 vm_pageout_stats_interval * hz);
1842 vm_paging_needed() == 0 &&
1843 vm_pages_needed == 0) {
1844 for (q = 0; q < PQ_MAXL2_SIZE; ++q)
1845 vm_pageout_page_stats(q);
1848 vm_pages_needed = 1;
1851 mycpu->gd_cnt.v_pdwakeups++;
1854 * Do whatever cleanup that the pmap code can.
1859 * Scan for pageout. Try to avoid thrashing the system
1862 * Calculate our target for the number of free+cache pages we
1863 * want to get to. This is higher then the number that causes
1864 * allocations to stall (severe) in order to provide hysteresis,
1865 * and if we don't make it all the way but get to the minimum
1868 inactive_shortage = vm_paging_target() + vm_pageout_deficit;
1869 vm_pageout_deficit = 0;
1871 for (q = 0; q < PQ_MAXL2_SIZE; ++q) {
1872 delta1 += vm_pageout_scan_inactive(
1874 inactive_shortage / PQ_MAXL2_SIZE + 1,
1879 * Figure out how many active pages we must deactivate. If
1880 * we were able to reach our target with just the inactive
1881 * scan above we limit the number of active pages we
1882 * deactivate to reduce unnecessary work.
1884 active_shortage = vmstats.v_inactive_target -
1885 vmstats.v_inactive_count;
1888 * If we were unable to free sufficient inactive pages to
1889 * satisfy the free/cache queue requirements then simply
1890 * reaching the inactive target may not be good enough.
1891 * Try to deactivate pages in excess of the target based
1894 * However to prevent thrashing the VM system do not
1895 * deactivate more than an additional 1/10 the inactive
1896 * target's worth of active pages.
1898 if (delta1 < inactive_shortage) {
1899 tmp = (inactive_shortage - delta1) * 2;
1900 if (tmp > vmstats.v_inactive_target / 10)
1901 tmp = vmstats.v_inactive_target / 10;
1902 active_shortage += tmp;
1906 for (q = 0; q < PQ_MAXL2_SIZE; ++q) {
1907 delta2 += vm_pageout_scan_active(
1909 inactive_shortage / PQ_MAXL2_SIZE + 1,
1910 active_shortage / PQ_MAXL2_SIZE + 1,
1915 * Finally free enough cache pages to meet our free page
1916 * requirement and take more drastic measures if we are
1919 inactive_shortage -= delta2;
1920 vm_pageout_scan_cache(inactive_shortage, vnodes_skipped,
1924 * Wait for more work.
1926 if (inactive_shortage > 0) {
1928 if (swap_pager_full) {
1930 * Running out of memory, catastrophic back-off
1931 * to one-second intervals.
1933 tsleep(&vm_pages_needed, 0, "pdelay", hz);
1934 } else if (pass < 10 && vm_pages_needed > 1) {
1936 * Normal operation, additional processes
1937 * have already kicked us. Retry immediately.
1939 } else if (pass < 10) {
1941 * Normal operation, fewer processes. Delay
1942 * a bit but allow wakeups.
1944 vm_pages_needed = 0;
1945 tsleep(&vm_pages_needed, 0, "pdelay", hz / 10);
1946 vm_pages_needed = 1;
1949 * We've taken too many passes, forced delay.
1951 tsleep(&vm_pages_needed, 0, "pdelay", hz / 10);
1955 * Interlocked wakeup of waiters (non-optional)
1958 if (vm_pages_needed && !vm_page_count_min(0)) {
1959 wakeup(&vmstats.v_free_count);
1960 vm_pages_needed = 0;
1966 static struct kproc_desc page_kp = {
1971 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start, &page_kp)
1975 * Called after allocating a page out of the cache or free queue
1976 * to possibly wake the pagedaemon up to replentish our supply.
1978 * We try to generate some hysteresis by waking the pagedaemon up
1979 * when our free+cache pages go below the free_min+cache_min level.
1980 * The pagedaemon tries to get the count back up to at least the
1981 * minimum, and through to the target level if possible.
1983 * If the pagedaemon is already active bump vm_pages_needed as a hint
1984 * that there are even more requests pending.
1990 pagedaemon_wakeup(void)
1992 if (vm_paging_needed() && curthread != pagethread) {
1993 if (vm_pages_needed == 0) {
1994 vm_pages_needed = 1; /* SMP race ok */
1995 wakeup(&vm_pages_needed);
1996 } else if (vm_page_count_min(0)) {
1997 ++vm_pages_needed; /* SMP race ok */
2002 #if !defined(NO_SWAPPING)
2009 vm_req_vmdaemon(void)
2011 static int lastrun = 0;
2013 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
2014 wakeup(&vm_daemon_needed);
2019 static int vm_daemon_callback(struct proc *p, void *data __unused);
2028 * XXX vm_daemon_needed specific token?
2031 tsleep(&vm_daemon_needed, 0, "psleep", 0);
2032 if (vm_pageout_req_swapout) {
2033 swapout_procs(vm_pageout_req_swapout);
2034 vm_pageout_req_swapout = 0;
2037 * scan the processes for exceeding their rlimits or if
2038 * process is swapped out -- deactivate pages
2040 allproc_scan(vm_daemon_callback, NULL);
2045 * Caller must hold proc_token.
2048 vm_daemon_callback(struct proc *p, void *data __unused)
2050 vm_pindex_t limit, size;
2053 * if this is a system process or if we have already
2054 * looked at this process, skip it.
2056 if (p->p_flag & (P_SYSTEM | P_WEXIT))
2060 * if the process is in a non-running type state,
2063 if (p->p_stat != SACTIVE && p->p_stat != SSTOP)
2069 limit = OFF_TO_IDX(qmin(p->p_rlimit[RLIMIT_RSS].rlim_cur,
2070 p->p_rlimit[RLIMIT_RSS].rlim_max));
2073 * let processes that are swapped out really be
2074 * swapped out. Set the limit to nothing to get as
2075 * many pages out to swap as possible.
2077 if (p->p_flag & P_SWAPPEDOUT)
2080 lwkt_gettoken(&p->p_vmspace->vm_map.token);
2081 size = vmspace_resident_count(p->p_vmspace);
2082 if (limit >= 0 && size >= limit) {
2083 vm_pageout_map_deactivate_pages(&p->p_vmspace->vm_map, limit);
2085 lwkt_reltoken(&p->p_vmspace->vm_map.token);