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");
187 SYSCTL_INT(_vm, OID_AUTO, vm_load,
188 CTLFLAG_RD, &vm_load, 0, "load on the VM system");
189 int vm_load_enable = 1;
190 SYSCTL_INT(_vm, OID_AUTO, vm_load_enable,
191 CTLFLAG_RW, &vm_load_enable, 0, "enable vm_load rate limiting");
194 SYSCTL_INT(_vm, OID_AUTO, vm_load_debug,
195 CTLFLAG_RW, &vm_load_debug, 0, "debug vm_load");
198 #define VM_PAGEOUT_PAGE_COUNT 16
199 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
201 int vm_page_max_wired; /* XXX max # of wired pages system-wide */
203 #if !defined(NO_SWAPPING)
204 typedef void freeer_fcn_t (vm_map_t, vm_object_t, vm_pindex_t, int);
205 static void vm_pageout_map_deactivate_pages (vm_map_t, vm_pindex_t);
206 static freeer_fcn_t vm_pageout_object_deactivate_pages;
207 static void vm_req_vmdaemon (void);
209 static void vm_pageout_page_stats(int q);
212 * Update vm_load to slow down faulting processes.
218 vm_fault_ratecheck(void)
220 if (vm_pages_needed) {
232 * Clean the page and remove it from the laundry. The page must not be
235 * We set the busy bit to cause potential page faults on this page to
236 * block. Note the careful timing, however, the busy bit isn't set till
237 * late and we cannot do anything that will mess with the page.
240 vm_pageout_clean(vm_page_t m)
243 vm_page_t mc[2*vm_pageout_page_count];
246 int ib, is, page_base;
247 vm_pindex_t pindex = m->pindex;
252 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
253 * with the new swapper, but we could have serious problems paging
254 * out other object types if there is insufficient memory.
256 * Unfortunately, checking free memory here is far too late, so the
257 * check has been moved up a procedural level.
261 * Don't mess with the page if it's busy, held, or special
263 * XXX do we really need to check hold_count here? hold_count
264 * isn't supposed to mess with vm_page ops except prevent the
265 * page from being reused.
267 if (m->hold_count != 0 || (m->flags & PG_UNMANAGED)) {
272 mc[vm_pageout_page_count] = m;
274 page_base = vm_pageout_page_count;
279 * Scan object for clusterable pages.
281 * We can cluster ONLY if: ->> the page is NOT
282 * clean, wired, busy, held, or mapped into a
283 * buffer, and one of the following:
284 * 1) The page is inactive, or a seldom used
287 * 2) we force the issue.
289 * During heavy mmap/modification loads the pageout
290 * daemon can really fragment the underlying file
291 * due to flushing pages out of order and not trying
292 * align the clusters (which leave sporatic out-of-order
293 * holes). To solve this problem we do the reverse scan
294 * first and attempt to align our cluster, then do a
295 * forward scan if room remains.
298 vm_object_hold(object);
300 while (ib && pageout_count < vm_pageout_page_count) {
308 p = vm_page_lookup_busy_try(object, pindex - ib, TRUE, &error);
309 if (error || p == NULL) {
313 if ((p->queue - p->pc) == PQ_CACHE ||
314 (p->flags & PG_UNMANAGED)) {
319 vm_page_test_dirty(p);
320 if ((p->dirty & p->valid) == 0 ||
321 p->queue - p->pc != PQ_INACTIVE ||
322 p->wire_count != 0 || /* may be held by buf cache */
323 p->hold_count != 0) { /* may be undergoing I/O */
332 * alignment boundry, stop here and switch directions. Do
335 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
339 while (pageout_count < vm_pageout_page_count &&
340 pindex + is < object->size) {
343 p = vm_page_lookup_busy_try(object, pindex + is, TRUE, &error);
344 if (error || p == NULL)
346 if (((p->queue - p->pc) == PQ_CACHE) ||
347 (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) {
351 vm_page_test_dirty(p);
352 if ((p->dirty & p->valid) == 0 ||
353 p->queue - p->pc != PQ_INACTIVE ||
354 p->wire_count != 0 || /* may be held by buf cache */
355 p->hold_count != 0) { /* may be undergoing I/O */
359 mc[page_base + pageout_count] = p;
365 * If we exhausted our forward scan, continue with the reverse scan
366 * when possible, even past a page boundry. This catches boundry
369 if (ib && pageout_count < vm_pageout_page_count)
372 vm_object_drop(object);
375 * we allow reads during pageouts...
377 return vm_pageout_flush(&mc[page_base], pageout_count, 0);
381 * vm_pageout_flush() - launder the given pages
383 * The given pages are laundered. Note that we setup for the start of
384 * I/O ( i.e. busy the page ), mark it read-only, and bump the object
385 * reference count all in here rather then in the parent. If we want
386 * the parent to do more sophisticated things we may have to change
389 * The pages in the array must be busied by the caller and will be
390 * unbusied by this function.
393 vm_pageout_flush(vm_page_t *mc, int count, int flags)
396 int pageout_status[count];
401 * Initiate I/O. Bump the vm_page_t->busy counter.
403 for (i = 0; i < count; i++) {
404 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
405 ("vm_pageout_flush page %p index %d/%d: partially "
406 "invalid page", mc[i], i, count));
407 vm_page_io_start(mc[i]);
411 * We must make the pages read-only. This will also force the
412 * modified bit in the related pmaps to be cleared. The pager
413 * cannot clear the bit for us since the I/O completion code
414 * typically runs from an interrupt. The act of making the page
415 * read-only handles the case for us.
417 * Then we can unbusy the pages, we still hold a reference by virtue
420 for (i = 0; i < count; i++) {
421 vm_page_protect(mc[i], VM_PROT_READ);
422 vm_page_wakeup(mc[i]);
425 object = mc[0]->object;
426 vm_object_pip_add(object, count);
428 vm_pager_put_pages(object, mc, count,
429 (flags | ((object == &kernel_object) ? VM_PAGER_PUT_SYNC : 0)),
432 for (i = 0; i < count; i++) {
433 vm_page_t mt = mc[i];
435 switch (pageout_status[i]) {
444 * Page outside of range of object. Right now we
445 * essentially lose the changes by pretending it
448 vm_page_busy_wait(mt, FALSE, "pgbad");
449 pmap_clear_modify(mt);
456 * A page typically cannot be paged out when we
457 * have run out of swap. We leave the page
458 * marked inactive and will try to page it out
461 * Starvation of the active page list is used to
462 * determine when the system is massively memory
471 * If the operation is still going, leave the page busy to
472 * block all other accesses. Also, leave the paging in
473 * progress indicator set so that we don't attempt an object
476 * For any pages which have completed synchronously,
477 * deactivate the page if we are under a severe deficit.
478 * Do not try to enter them into the cache, though, they
479 * might still be read-heavy.
481 if (pageout_status[i] != VM_PAGER_PEND) {
482 vm_page_busy_wait(mt, FALSE, "pgouw");
483 if (vm_page_count_severe())
484 vm_page_deactivate(mt);
486 if (!vm_page_count_severe() || !vm_page_try_to_cache(mt))
487 vm_page_protect(mt, VM_PROT_READ);
489 vm_page_io_finish(mt);
491 vm_object_pip_wakeup(object);
497 #if !defined(NO_SWAPPING)
499 * deactivate enough pages to satisfy the inactive target
500 * requirements or if vm_page_proc_limit is set, then
501 * deactivate all of the pages in the object and its
504 * The map must be locked.
505 * The caller must hold the vm_object.
507 static int vm_pageout_object_deactivate_pages_callback(vm_page_t, void *);
510 vm_pageout_object_deactivate_pages(vm_map_t map, vm_object_t object,
511 vm_pindex_t desired, int map_remove_only)
513 struct rb_vm_page_scan_info info;
518 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
522 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
524 if (lobject->type == OBJT_DEVICE || lobject->type == OBJT_PHYS)
526 if (lobject->paging_in_progress)
529 remove_mode = map_remove_only;
530 if (lobject->shadow_count > 1)
534 * scan the objects entire memory queue. We hold the
535 * object's token so the scan should not race anything.
537 info.limit = remove_mode;
539 info.desired = desired;
540 vm_page_rb_tree_RB_SCAN(&lobject->rb_memq, NULL,
541 vm_pageout_object_deactivate_pages_callback,
544 while ((tobject = lobject->backing_object) != NULL) {
545 KKASSERT(tobject != object);
546 vm_object_hold(tobject);
547 if (tobject == lobject->backing_object)
549 vm_object_drop(tobject);
551 if (lobject != object) {
552 vm_object_lock_swap();
553 vm_object_drop(lobject);
557 if (lobject != object)
558 vm_object_drop(lobject);
562 * The caller must hold the vm_object.
565 vm_pageout_object_deactivate_pages_callback(vm_page_t p, void *data)
567 struct rb_vm_page_scan_info *info = data;
570 if (pmap_resident_count(vm_map_pmap(info->map)) <= info->desired) {
573 mycpu->gd_cnt.v_pdpages++;
575 if (vm_page_busy_try(p, TRUE))
577 if (p->wire_count || p->hold_count || (p->flags & PG_UNMANAGED)) {
581 if (!pmap_page_exists_quick(vm_map_pmap(info->map), p)) {
586 actcount = pmap_ts_referenced(p);
588 vm_page_flag_set(p, PG_REFERENCED);
589 } else if (p->flags & PG_REFERENCED) {
593 vm_page_and_queue_spin_lock(p);
594 if (p->queue - p->pc != PQ_ACTIVE && (p->flags & PG_REFERENCED)) {
595 vm_page_and_queue_spin_unlock(p);
597 p->act_count += actcount;
598 vm_page_flag_clear(p, PG_REFERENCED);
599 } else if (p->queue - p->pc == PQ_ACTIVE) {
600 if ((p->flags & PG_REFERENCED) == 0) {
601 p->act_count -= min(p->act_count, ACT_DECLINE);
603 (vm_pageout_algorithm || (p->act_count == 0))) {
604 vm_page_and_queue_spin_unlock(p);
605 vm_page_protect(p, VM_PROT_NONE);
606 vm_page_deactivate(p);
608 TAILQ_REMOVE(&vm_page_queues[p->queue].pl,
610 TAILQ_INSERT_TAIL(&vm_page_queues[p->queue].pl,
612 vm_page_and_queue_spin_unlock(p);
615 vm_page_and_queue_spin_unlock(p);
617 vm_page_flag_clear(p, PG_REFERENCED);
619 vm_page_and_queue_spin_lock(p);
620 if (p->queue - p->pc == PQ_ACTIVE) {
621 if (p->act_count < (ACT_MAX - ACT_ADVANCE))
622 p->act_count += ACT_ADVANCE;
623 TAILQ_REMOVE(&vm_page_queues[p->queue].pl,
625 TAILQ_INSERT_TAIL(&vm_page_queues[p->queue].pl,
628 vm_page_and_queue_spin_unlock(p);
630 } else if (p->queue - p->pc == PQ_INACTIVE) {
631 vm_page_and_queue_spin_unlock(p);
632 vm_page_protect(p, VM_PROT_NONE);
634 vm_page_and_queue_spin_unlock(p);
641 * Deactivate some number of pages in a map, try to do it fairly, but
642 * that is really hard to do.
645 vm_pageout_map_deactivate_pages(vm_map_t map, vm_pindex_t desired)
648 vm_object_t obj, bigobj;
651 if (lockmgr(&map->lock, LK_EXCLUSIVE | LK_NOWAIT)) {
659 * first, search out the biggest object, and try to free pages from
662 tmpe = map->header.next;
663 while (tmpe != &map->header) {
664 switch(tmpe->maptype) {
665 case VM_MAPTYPE_NORMAL:
666 case VM_MAPTYPE_VPAGETABLE:
667 obj = tmpe->object.vm_object;
668 if ((obj != NULL) && (obj->shadow_count <= 1) &&
670 (bigobj->resident_page_count < obj->resident_page_count))) {
677 if (tmpe->wired_count > 0)
678 nothingwired = FALSE;
683 vm_object_hold(bigobj);
684 vm_pageout_object_deactivate_pages(map, bigobj, desired, 0);
685 vm_object_drop(bigobj);
689 * Next, hunt around for other pages to deactivate. We actually
690 * do this search sort of wrong -- .text first is not the best idea.
692 tmpe = map->header.next;
693 while (tmpe != &map->header) {
694 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
696 switch(tmpe->maptype) {
697 case VM_MAPTYPE_NORMAL:
698 case VM_MAPTYPE_VPAGETABLE:
699 obj = tmpe->object.vm_object;
702 vm_pageout_object_deactivate_pages(map, obj, desired, 0);
713 * Remove all mappings if a process is swapped out, this will free page
716 if (desired == 0 && nothingwired)
717 pmap_remove(vm_map_pmap(map),
718 VM_MIN_USER_ADDRESS, VM_MAX_USER_ADDRESS);
724 * Called when the pageout scan wants to free a page. We no longer
725 * try to cycle the vm_object here with a reference & dealloc, which can
726 * cause a non-trivial object collapse in a critical path.
728 * It is unclear why we cycled the ref_count in the past, perhaps to try
729 * to optimize shadow chain collapses but I don't quite see why it would
730 * be necessary. An OBJ_DEAD object should terminate any and all vm_pages
731 * synchronously and not have to be kicked-start.
734 vm_pageout_page_free(vm_page_t m)
736 vm_page_protect(m, VM_PROT_NONE);
741 * vm_pageout_scan does the dirty work for the pageout daemon.
743 struct vm_pageout_scan_info {
744 struct proc *bigproc;
748 static int vm_pageout_scan_callback(struct proc *p, void *data);
751 vm_pageout_scan_inactive(int pass, int q, int inactive_shortage,
752 int *vnodes_skippedp)
755 struct vm_page marker;
756 struct vnode *vpfailed; /* warning, allowed to be stale */
764 * Start scanning the inactive queue for pages we can move to the
765 * cache or free. The scan will stop when the target is reached or
766 * we have scanned the entire inactive queue. Note that m->act_count
767 * is not used to form decisions for the inactive queue, only for the
770 * maxlaunder limits the number of dirty pages we flush per scan.
771 * For most systems a smaller value (16 or 32) is more robust under
772 * extreme memory and disk pressure because any unnecessary writes
773 * to disk can result in extreme performance degredation. However,
774 * systems with excessive dirty pages (especially when MAP_NOSYNC is
775 * used) will die horribly with limited laundering. If the pageout
776 * daemon cannot clean enough pages in the first pass, we let it go
777 * all out in succeeding passes.
779 if ((maxlaunder = vm_max_launder) <= 1)
785 * Initialize our marker
787 bzero(&marker, sizeof(marker));
788 marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
789 marker.queue = PQ_INACTIVE + q;
791 marker.wire_count = 1;
794 * Inactive queue scan.
796 * NOTE: The vm_page must be spinlocked before the queue to avoid
797 * deadlocks, so it is easiest to simply iterate the loop
798 * with the queue unlocked at the top.
802 vm_page_queues_spin_lock(PQ_INACTIVE + q);
803 TAILQ_INSERT_HEAD(&vm_page_queues[PQ_INACTIVE + q].pl, &marker, pageq);
804 maxscan = vmstats.v_inactive_count;
805 vm_page_queues_spin_unlock(PQ_INACTIVE + q);
807 while ((m = TAILQ_NEXT(&marker, pageq)) != NULL &&
808 maxscan-- > 0 && inactive_shortage - delta > 0)
810 vm_page_and_queue_spin_lock(m);
811 if (m != TAILQ_NEXT(&marker, pageq)) {
812 vm_page_and_queue_spin_unlock(m);
816 KKASSERT(m->queue - m->pc == PQ_INACTIVE);
817 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE + q].pl,
819 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE + q].pl, m,
821 mycpu->gd_cnt.v_pdpages++;
826 if (m->flags & PG_MARKER) {
827 vm_page_and_queue_spin_unlock(m);
832 * Try to busy the page. Don't mess with pages which are
833 * already busy or reorder them in the queue.
835 if (vm_page_busy_try(m, TRUE)) {
836 vm_page_and_queue_spin_unlock(m);
839 vm_page_and_queue_spin_unlock(m);
840 KKASSERT(m->queue - m->pc == PQ_INACTIVE);
845 * The page has been successfully busied and is now no
846 * longer spinlocked. The queue is no longer spinlocked
851 * A held page may be undergoing I/O, so skip it.
854 vm_page_and_queue_spin_lock(m);
855 if (m->queue - m->pc == PQ_INACTIVE) {
857 &vm_page_queues[PQ_INACTIVE + q].pl,
860 &vm_page_queues[PQ_INACTIVE + q].pl,
863 vm_page_and_queue_spin_unlock(m);
864 ++vm_swapcache_inactive_heuristic;
869 if (m->object->ref_count == 0) {
871 * If the object is not being used, we ignore previous
874 vm_page_flag_clear(m, PG_REFERENCED);
875 pmap_clear_reference(m);
876 /* fall through to end */
877 } else if (((m->flags & PG_REFERENCED) == 0) &&
878 (actcount = pmap_ts_referenced(m))) {
880 * Otherwise, if the page has been referenced while
881 * in the inactive queue, we bump the "activation
882 * count" upwards, making it less likely that the
883 * page will be added back to the inactive queue
884 * prematurely again. Here we check the page tables
885 * (or emulated bits, if any), given the upper level
886 * VM system not knowing anything about existing
890 m->act_count += (actcount + ACT_ADVANCE);
896 * (m) is still busied.
898 * If the upper level VM system knows about any page
899 * references, we activate the page. We also set the
900 * "activation count" higher than normal so that we will less
901 * likely place pages back onto the inactive queue again.
903 if ((m->flags & PG_REFERENCED) != 0) {
904 vm_page_flag_clear(m, PG_REFERENCED);
905 actcount = pmap_ts_referenced(m);
907 m->act_count += (actcount + ACT_ADVANCE + 1);
913 * If the upper level VM system doesn't know anything about
914 * the page being dirty, we have to check for it again. As
915 * far as the VM code knows, any partially dirty pages are
918 * Pages marked PG_WRITEABLE may be mapped into the user
919 * address space of a process running on another cpu. A
920 * user process (without holding the MP lock) running on
921 * another cpu may be able to touch the page while we are
922 * trying to remove it. vm_page_cache() will handle this
926 vm_page_test_dirty(m);
933 * Invalid pages can be easily freed
935 vm_pageout_page_free(m);
936 mycpu->gd_cnt.v_dfree++;
938 } else if (m->dirty == 0) {
940 * Clean pages can be placed onto the cache queue.
941 * This effectively frees them.
945 } else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) {
947 * Dirty pages need to be paged out, but flushing
948 * a page is extremely expensive verses freeing
949 * a clean page. Rather then artificially limiting
950 * the number of pages we can flush, we instead give
951 * dirty pages extra priority on the inactive queue
952 * by forcing them to be cycled through the queue
953 * twice before being flushed, after which the
954 * (now clean) page will cycle through once more
955 * before being freed. This significantly extends
956 * the thrash point for a heavily loaded machine.
958 vm_page_flag_set(m, PG_WINATCFLS);
959 vm_page_and_queue_spin_lock(m);
960 if (m->queue - m->pc == PQ_INACTIVE) {
962 &vm_page_queues[PQ_INACTIVE + q].pl,
965 &vm_page_queues[PQ_INACTIVE + q].pl,
968 vm_page_and_queue_spin_unlock(m);
969 ++vm_swapcache_inactive_heuristic;
971 } else if (maxlaunder > 0) {
973 * We always want to try to flush some dirty pages if
974 * we encounter them, to keep the system stable.
975 * Normally this number is small, but under extreme
976 * pressure where there are insufficient clean pages
977 * on the inactive queue, we may have to go all out.
979 int swap_pageouts_ok;
980 struct vnode *vp = NULL;
984 if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
985 swap_pageouts_ok = 1;
987 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
988 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
989 vm_page_count_min(0));
994 * We don't bother paging objects that are "dead".
995 * Those objects are in a "rundown" state.
997 if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
998 vm_page_and_queue_spin_lock(m);
999 if (m->queue - m->pc == PQ_INACTIVE) {
1001 &vm_page_queues[PQ_INACTIVE + q].pl,
1004 &vm_page_queues[PQ_INACTIVE + q].pl,
1007 vm_page_and_queue_spin_unlock(m);
1008 ++vm_swapcache_inactive_heuristic;
1014 * (m) is still busied.
1016 * The object is already known NOT to be dead. It
1017 * is possible for the vget() to block the whole
1018 * pageout daemon, but the new low-memory handling
1019 * code should prevent it.
1021 * The previous code skipped locked vnodes and, worse,
1022 * reordered pages in the queue. This results in
1023 * completely non-deterministic operation because,
1024 * quite often, a vm_fault has initiated an I/O and
1025 * is holding a locked vnode at just the point where
1026 * the pageout daemon is woken up.
1028 * We can't wait forever for the vnode lock, we might
1029 * deadlock due to a vn_read() getting stuck in
1030 * vm_wait while holding this vnode. We skip the
1031 * vnode if we can't get it in a reasonable amount
1034 * vpfailed is used to (try to) avoid the case where
1035 * a large number of pages are associated with a
1036 * locked vnode, which could cause the pageout daemon
1037 * to stall for an excessive amount of time.
1039 if (object->type == OBJT_VNODE) {
1042 vp = object->handle;
1043 flags = LK_EXCLUSIVE | LK_NOOBJ;
1047 flags |= LK_TIMELOCK;
1052 * We have unbusied (m) temporarily so we can
1053 * acquire the vp lock without deadlocking.
1054 * (m) is held to prevent destruction.
1056 if (vget(vp, flags) != 0) {
1058 ++pageout_lock_miss;
1059 if (object->flags & OBJ_MIGHTBEDIRTY)
1066 * The page might have been moved to another
1067 * queue during potential blocking in vget()
1068 * above. The page might have been freed and
1069 * reused for another vnode. The object might
1070 * have been reused for another vnode.
1072 if (m->queue - m->pc != PQ_INACTIVE ||
1073 m->object != object ||
1074 object->handle != vp) {
1075 if (object->flags & OBJ_MIGHTBEDIRTY)
1083 * The page may have been busied during the
1084 * blocking in vput(); We don't move the
1085 * page back onto the end of the queue so that
1086 * statistics are more correct if we don't.
1088 if (vm_page_busy_try(m, TRUE)) {
1096 * (m) is busied again
1098 * We own the busy bit and remove our hold
1099 * bit. If the page is still held it
1100 * might be undergoing I/O, so skip it.
1102 if (m->hold_count) {
1103 vm_page_and_queue_spin_lock(m);
1104 if (m->queue - m->pc == PQ_INACTIVE) {
1105 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE + q].pl, m, pageq);
1106 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE + q].pl, m, pageq);
1108 vm_page_and_queue_spin_unlock(m);
1109 ++vm_swapcache_inactive_heuristic;
1110 if (object->flags & OBJ_MIGHTBEDIRTY)
1116 /* (m) is left busied as we fall through */
1120 * page is busy and not held here.
1122 * If a page is dirty, then it is either being washed
1123 * (but not yet cleaned) or it is still in the
1124 * laundry. If it is still in the laundry, then we
1125 * start the cleaning operation.
1127 * decrement inactive_shortage on success to account
1128 * for the (future) cleaned page. Otherwise we
1129 * could wind up laundering or cleaning too many
1132 if (vm_pageout_clean(m) != 0) {
1136 /* clean ate busy, page no longer accessible */
1143 vm_page_queues_spin_lock(PQ_INACTIVE + q);
1144 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE + q].pl, &marker, pageq);
1145 vm_page_queues_spin_unlock(PQ_INACTIVE + q);
1151 vm_pageout_scan_active(int pass, int q,
1152 int inactive_shortage, int active_shortage,
1153 int *recycle_countp)
1155 struct vm_page marker;
1162 * We want to move pages from the active queue to the inactive
1163 * queue to get the inactive queue to the inactive target. If
1164 * we still have a page shortage from above we try to directly free
1165 * clean pages instead of moving them.
1167 * If we do still have a shortage we keep track of the number of
1168 * pages we free or cache (recycle_count) as a measure of thrashing
1169 * between the active and inactive queues.
1171 * If we were able to completely satisfy the free+cache targets
1172 * from the inactive pool we limit the number of pages we move
1173 * from the active pool to the inactive pool to 2x the pages we
1174 * had removed from the inactive pool (with a minimum of 1/5 the
1175 * inactive target). If we were not able to completely satisfy
1176 * the free+cache targets we go for the whole target aggressively.
1178 * NOTE: Both variables can end up negative.
1179 * NOTE: We are still in a critical section.
1182 bzero(&marker, sizeof(marker));
1183 marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
1184 marker.queue = PQ_ACTIVE + q;
1186 marker.wire_count = 1;
1188 vm_page_queues_spin_lock(PQ_ACTIVE + q);
1189 TAILQ_INSERT_HEAD(&vm_page_queues[PQ_ACTIVE + q].pl, &marker, pageq);
1190 vm_page_queues_spin_unlock(PQ_ACTIVE + q);
1191 pcount = vmstats.v_active_count;
1193 while ((m = TAILQ_NEXT(&marker, pageq)) != NULL &&
1194 pcount-- > 0 && (inactive_shortage - delta > 0 ||
1195 active_shortage > 0))
1197 vm_page_and_queue_spin_lock(m);
1198 if (m != TAILQ_NEXT(&marker, pageq)) {
1199 vm_page_and_queue_spin_unlock(m);
1203 KKASSERT(m->queue - m->pc == PQ_ACTIVE);
1204 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE + q].pl,
1206 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_ACTIVE + q].pl, m,
1212 if (m->flags & PG_MARKER) {
1213 vm_page_and_queue_spin_unlock(m);
1218 * Try to busy the page. Don't mess with pages which are
1219 * already busy or reorder them in the queue.
1221 if (vm_page_busy_try(m, TRUE)) {
1222 vm_page_and_queue_spin_unlock(m);
1227 * Don't deactivate pages that are held, even if we can
1228 * busy them. (XXX why not?)
1230 if (m->hold_count != 0) {
1231 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE + q].pl,
1233 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE + q].pl,
1235 vm_page_and_queue_spin_unlock(m);
1239 vm_page_and_queue_spin_unlock(m);
1243 * The page has been successfully busied and the page and
1244 * queue are no longer locked.
1248 * The count for pagedaemon pages is done after checking the
1249 * page for eligibility...
1251 mycpu->gd_cnt.v_pdpages++;
1254 * Check to see "how much" the page has been used and clear
1255 * the tracking access bits. If the object has no references
1256 * don't bother paying the expense.
1259 if (m->object->ref_count != 0) {
1260 if (m->flags & PG_REFERENCED)
1262 actcount += pmap_ts_referenced(m);
1264 m->act_count += ACT_ADVANCE + actcount;
1265 if (m->act_count > ACT_MAX)
1266 m->act_count = ACT_MAX;
1269 vm_page_flag_clear(m, PG_REFERENCED);
1272 * actcount is only valid if the object ref_count is non-zero.
1274 if (actcount && m->object->ref_count != 0) {
1275 vm_page_and_queue_spin_lock(m);
1276 if (m->queue - m->pc == PQ_ACTIVE) {
1278 &vm_page_queues[PQ_ACTIVE + q].pl,
1281 &vm_page_queues[PQ_ACTIVE + q].pl,
1284 vm_page_and_queue_spin_unlock(m);
1287 m->act_count -= min(m->act_count, ACT_DECLINE);
1288 if (vm_pageout_algorithm ||
1289 m->object->ref_count == 0 ||
1290 m->act_count < pass + 1
1293 * Deactivate the page. If we had a
1294 * shortage from our inactive scan try to
1295 * free (cache) the page instead.
1297 * Don't just blindly cache the page if
1298 * we do not have a shortage from the
1299 * inactive scan, that could lead to
1300 * gigabytes being moved.
1303 if (inactive_shortage - delta > 0 ||
1304 m->object->ref_count == 0) {
1305 if (inactive_shortage - delta > 0)
1307 vm_page_protect(m, VM_PROT_NONE);
1308 if (m->dirty == 0 &&
1309 inactive_shortage - delta > 0) {
1313 vm_page_deactivate(m);
1317 vm_page_deactivate(m);
1321 vm_page_and_queue_spin_lock(m);
1322 if (m->queue - m->pc == PQ_ACTIVE) {
1324 &vm_page_queues[PQ_ACTIVE + q].pl,
1327 &vm_page_queues[PQ_ACTIVE + q].pl,
1330 vm_page_and_queue_spin_unlock(m);
1337 * Clean out our local marker.
1339 vm_page_queues_spin_lock(PQ_ACTIVE + q);
1340 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE + q].pl, &marker, pageq);
1341 vm_page_queues_spin_unlock(PQ_ACTIVE + q);
1347 * The number of actually free pages can drop down to v_free_reserved,
1348 * we try to build the free count back above v_free_min. Note that
1349 * vm_paging_needed() also returns TRUE if v_free_count is not at
1350 * least v_free_min so that is the minimum we must build the free
1353 * We use a slightly higher target to improve hysteresis,
1354 * ((v_free_target + v_free_min) / 2). Since v_free_target
1355 * is usually the same as v_cache_min this maintains about
1356 * half the pages in the free queue as are in the cache queue,
1357 * providing pretty good pipelining for pageout operation.
1359 * The system operator can manipulate vm.v_cache_min and
1360 * vm.v_free_target to tune the pageout demon. Be sure
1361 * to keep vm.v_free_min < vm.v_free_target.
1363 * Note that the original paging target is to get at least
1364 * (free_min + cache_min) into (free + cache). The slightly
1365 * higher target will shift additional pages from cache to free
1366 * without effecting the original paging target in order to
1367 * maintain better hysteresis and not have the free count always
1368 * be dead-on v_free_min.
1370 * NOTE: we are still in a critical section.
1372 * Pages moved from PQ_CACHE to totally free are not counted in the
1373 * pages_freed counter.
1376 vm_pageout_scan_cache(int inactive_shortage,
1377 int vnodes_skipped, int recycle_count)
1379 struct vm_pageout_scan_info info;
1382 while (vmstats.v_free_count <
1383 (vmstats.v_free_min + vmstats.v_free_target) / 2) {
1385 * This steals some code from vm/vm_page.c
1387 static int cache_rover = 0;
1389 m = vm_page_list_find(PQ_CACHE, cache_rover & PQ_L2_MASK, FALSE);
1392 /* page is returned removed from its queue and spinlocked */
1393 if (vm_page_busy_try(m, TRUE)) {
1394 vm_page_deactivate_locked(m);
1395 vm_page_spin_unlock(m);
1397 kprintf("Warning: busy page %p found in cache\n", m);
1401 vm_page_spin_unlock(m);
1402 pagedaemon_wakeup();
1406 * Page has been successfully busied and it and its queue
1407 * is no longer spinlocked.
1409 if ((m->flags & PG_UNMANAGED) ||
1412 vm_page_deactivate(m);
1416 KKASSERT((m->flags & PG_MAPPED) == 0);
1417 KKASSERT(m->dirty == 0);
1418 cache_rover += PQ_PRIME2;
1419 vm_pageout_page_free(m);
1420 mycpu->gd_cnt.v_dfree++;
1423 #if !defined(NO_SWAPPING)
1425 * Idle process swapout -- run once per second.
1427 if (vm_swap_idle_enabled) {
1429 if (time_second != lsec) {
1430 vm_pageout_req_swapout |= VM_SWAP_IDLE;
1438 * If we didn't get enough free pages, and we have skipped a vnode
1439 * in a writeable object, wakeup the sync daemon. And kick swapout
1440 * if we did not get enough free pages.
1442 if (vm_paging_target() > 0) {
1443 if (vnodes_skipped && vm_page_count_min(0))
1445 #if !defined(NO_SWAPPING)
1446 if (vm_swap_enabled && vm_page_count_target()) {
1448 vm_pageout_req_swapout |= VM_SWAP_NORMAL;
1454 * Handle catastrophic conditions. Under good conditions we should
1455 * be at the target, well beyond our minimum. If we could not even
1456 * reach our minimum the system is under heavy stress.
1458 * Determine whether we have run out of memory. This occurs when
1459 * swap_pager_full is TRUE and the only pages left in the page
1460 * queues are dirty. We will still likely have page shortages.
1462 * - swap_pager_full is set if insufficient swap was
1463 * available to satisfy a requested pageout.
1465 * - the inactive queue is bloated (4 x size of active queue),
1466 * meaning it is unable to get rid of dirty pages and.
1468 * - vm_page_count_min() without counting pages recycled from the
1469 * active queue (recycle_count) means we could not recover
1470 * enough pages to meet bare minimum needs. This test only
1471 * works if the inactive queue is bloated.
1473 * - due to a positive inactive_shortage we shifted the remaining
1474 * dirty pages from the active queue to the inactive queue
1475 * trying to find clean ones to free.
1477 if (swap_pager_full && vm_page_count_min(recycle_count))
1478 kprintf("Warning: system low on memory+swap!\n");
1479 if (swap_pager_full && vm_page_count_min(recycle_count) &&
1480 vmstats.v_inactive_count > vmstats.v_active_count * 4 &&
1481 inactive_shortage > 0) {
1485 info.bigproc = NULL;
1487 allproc_scan(vm_pageout_scan_callback, &info);
1488 if (info.bigproc != NULL) {
1489 killproc(info.bigproc, "out of swap space");
1490 info.bigproc->p_nice = PRIO_MIN;
1491 info.bigproc->p_usched->resetpriority(
1492 FIRST_LWP_IN_PROC(info.bigproc));
1493 wakeup(&vmstats.v_free_count);
1494 PRELE(info.bigproc);
1500 * The caller must hold proc_token.
1503 vm_pageout_scan_callback(struct proc *p, void *data)
1505 struct vm_pageout_scan_info *info = data;
1509 * Never kill system processes or init. If we have configured swap
1510 * then try to avoid killing low-numbered pids.
1512 if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) ||
1513 ((p->p_pid < 48) && (vm_swap_size != 0))) {
1518 * if the process is in a non-running type state,
1521 if (p->p_stat != SACTIVE && p->p_stat != SSTOP)
1525 * Get the approximate process size. Note that anonymous pages
1526 * with backing swap will be counted twice, but there should not
1527 * be too many such pages due to the stress the VM system is
1528 * under at this point.
1530 size = vmspace_anonymous_count(p->p_vmspace) +
1531 vmspace_swap_count(p->p_vmspace);
1534 * If the this process is bigger than the biggest one
1537 if (info->bigsize < size) {
1539 PRELE(info->bigproc);
1542 info->bigsize = size;
1549 * This routine tries to maintain the pseudo LRU active queue,
1550 * so that during long periods of time where there is no paging,
1551 * that some statistic accumulation still occurs. This code
1552 * helps the situation where paging just starts to occur.
1555 vm_pageout_page_stats(int q)
1557 static int fullintervalcount = 0;
1558 struct vm_page marker;
1560 int pcount, tpcount; /* Number of pages to check */
1563 page_shortage = (vmstats.v_inactive_target + vmstats.v_cache_max +
1564 vmstats.v_free_min) -
1565 (vmstats.v_free_count + vmstats.v_inactive_count +
1566 vmstats.v_cache_count);
1568 if (page_shortage <= 0)
1571 pcount = vmstats.v_active_count;
1572 fullintervalcount += vm_pageout_stats_interval;
1573 if (fullintervalcount < vm_pageout_full_stats_interval) {
1574 tpcount = (vm_pageout_stats_max * vmstats.v_active_count) /
1575 vmstats.v_page_count;
1576 if (pcount > tpcount)
1579 fullintervalcount = 0;
1582 bzero(&marker, sizeof(marker));
1583 marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
1584 marker.queue = PQ_ACTIVE + q;
1586 marker.wire_count = 1;
1588 vm_page_queues_spin_lock(PQ_ACTIVE + q);
1589 TAILQ_INSERT_HEAD(&vm_page_queues[PQ_ACTIVE + q].pl, &marker, pageq);
1590 vm_page_queues_spin_unlock(PQ_ACTIVE + q);
1592 while ((m = TAILQ_NEXT(&marker, pageq)) != NULL &&
1597 vm_page_and_queue_spin_lock(m);
1598 if (m != TAILQ_NEXT(&marker, pageq)) {
1599 vm_page_and_queue_spin_unlock(m);
1603 KKASSERT(m->queue - m->pc == PQ_ACTIVE);
1604 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE + q].pl, &marker, pageq);
1605 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_ACTIVE + q].pl, m,
1611 if (m->flags & PG_MARKER) {
1612 vm_page_and_queue_spin_unlock(m);
1617 * Ignore pages we can't busy
1619 if (vm_page_busy_try(m, TRUE)) {
1620 vm_page_and_queue_spin_unlock(m);
1623 vm_page_and_queue_spin_unlock(m);
1624 KKASSERT(m->queue - m->pc == PQ_ACTIVE);
1627 * We now have a safely busied page, the page and queue
1628 * spinlocks have been released.
1632 if (m->hold_count) {
1638 * Calculate activity
1641 if (m->flags & PG_REFERENCED) {
1642 vm_page_flag_clear(m, PG_REFERENCED);
1645 actcount += pmap_ts_referenced(m);
1648 * Update act_count and move page to end of queue.
1651 m->act_count += ACT_ADVANCE + actcount;
1652 if (m->act_count > ACT_MAX)
1653 m->act_count = ACT_MAX;
1654 vm_page_and_queue_spin_lock(m);
1655 if (m->queue - m->pc == PQ_ACTIVE) {
1657 &vm_page_queues[PQ_ACTIVE + q].pl,
1660 &vm_page_queues[PQ_ACTIVE + q].pl,
1663 vm_page_and_queue_spin_unlock(m);
1668 if (m->act_count == 0) {
1670 * We turn off page access, so that we have
1671 * more accurate RSS stats. We don't do this
1672 * in the normal page deactivation when the
1673 * system is loaded VM wise, because the
1674 * cost of the large number of page protect
1675 * operations would be higher than the value
1676 * of doing the operation.
1678 * We use the marker to save our place so
1679 * we can release the spin lock. both (m)
1680 * and (next) will be invalid.
1682 vm_page_protect(m, VM_PROT_NONE);
1683 vm_page_deactivate(m);
1685 m->act_count -= min(m->act_count, ACT_DECLINE);
1686 vm_page_and_queue_spin_lock(m);
1687 if (m->queue - m->pc == PQ_ACTIVE) {
1689 &vm_page_queues[PQ_ACTIVE + q].pl,
1692 &vm_page_queues[PQ_ACTIVE + q].pl,
1695 vm_page_and_queue_spin_unlock(m);
1701 * Remove our local marker
1703 vm_page_queues_spin_lock(PQ_ACTIVE + q);
1704 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE + q].pl, &marker, pageq);
1705 vm_page_queues_spin_unlock(PQ_ACTIVE + q);
1709 vm_pageout_free_page_calc(vm_size_t count)
1711 if (count < vmstats.v_page_count)
1714 * free_reserved needs to include enough for the largest swap pager
1715 * structures plus enough for any pv_entry structs when paging.
1717 * v_free_min normal allocations
1718 * v_free_reserved system allocations
1719 * v_pageout_free_min allocations by pageout daemon
1720 * v_interrupt_free_min low level allocations (e.g swap structures)
1722 if (vmstats.v_page_count > 1024)
1723 vmstats.v_free_min = 64 + (vmstats.v_page_count - 1024) / 200;
1725 vmstats.v_free_min = 64;
1726 vmstats.v_free_reserved = vmstats.v_free_min * 4 / 8 + 7;
1727 vmstats.v_free_severe = vmstats.v_free_min * 4 / 8 + 0;
1728 vmstats.v_pageout_free_min = vmstats.v_free_min * 2 / 8 + 7;
1729 vmstats.v_interrupt_free_min = vmstats.v_free_min * 1 / 8 + 7;
1736 * vm_pageout is the high level pageout daemon.
1741 vm_pageout_thread(void)
1747 * Initialize some paging parameters.
1749 curthread->td_flags |= TDF_SYSTHREAD;
1751 if (vmstats.v_page_count < 2000)
1752 vm_pageout_page_count = 8;
1754 vm_pageout_free_page_calc(vmstats.v_page_count);
1757 * v_free_target and v_cache_min control pageout hysteresis. Note
1758 * that these are more a measure of the VM cache queue hysteresis
1759 * then the VM free queue. Specifically, v_free_target is the
1760 * high water mark (free+cache pages).
1762 * v_free_reserved + v_cache_min (mostly means v_cache_min) is the
1763 * low water mark, while v_free_min is the stop. v_cache_min must
1764 * be big enough to handle memory needs while the pageout daemon
1765 * is signalled and run to free more pages.
1767 if (vmstats.v_free_count > 6144)
1768 vmstats.v_free_target = 4 * vmstats.v_free_min + vmstats.v_free_reserved;
1770 vmstats.v_free_target = 2 * vmstats.v_free_min + vmstats.v_free_reserved;
1773 * NOTE: With the new buffer cache b_act_count we want the default
1774 * inactive target to be a percentage of available memory.
1776 * The inactive target essentially determines the minimum
1777 * number of 'temporary' pages capable of caching one-time-use
1778 * files when the VM system is otherwise full of pages
1779 * belonging to multi-time-use files or active program data.
1781 * NOTE: The inactive target is aggressively persued only if the
1782 * inactive queue becomes too small. If the inactive queue
1783 * is large enough to satisfy page movement to free+cache
1784 * then it is repopulated more slowly from the active queue.
1785 * This allows a general inactive_target default to be set.
1787 * There is an issue here for processes which sit mostly idle
1788 * 'overnight', such as sshd, tcsh, and X. Any movement from
1789 * the active queue will eventually cause such pages to
1790 * recycle eventually causing a lot of paging in the morning.
1791 * To reduce the incidence of this pages cycled out of the
1792 * buffer cache are moved directly to the inactive queue if
1793 * they were only used once or twice.
1795 * The vfs.vm_cycle_point sysctl can be used to adjust this.
1796 * Increasing the value (up to 64) increases the number of
1797 * buffer recyclements which go directly to the inactive queue.
1799 if (vmstats.v_free_count > 2048) {
1800 vmstats.v_cache_min = vmstats.v_free_target;
1801 vmstats.v_cache_max = 2 * vmstats.v_cache_min;
1803 vmstats.v_cache_min = 0;
1804 vmstats.v_cache_max = 0;
1806 vmstats.v_inactive_target = vmstats.v_free_count / 4;
1808 /* XXX does not really belong here */
1809 if (vm_page_max_wired == 0)
1810 vm_page_max_wired = vmstats.v_free_count / 3;
1812 if (vm_pageout_stats_max == 0)
1813 vm_pageout_stats_max = vmstats.v_free_target;
1816 * Set interval in seconds for stats scan.
1818 if (vm_pageout_stats_interval == 0)
1819 vm_pageout_stats_interval = 5;
1820 if (vm_pageout_full_stats_interval == 0)
1821 vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
1825 * Set maximum free per pass
1827 if (vm_pageout_stats_free_max == 0)
1828 vm_pageout_stats_free_max = 5;
1830 swap_pager_swap_init();
1834 * The pageout daemon is never done, so loop forever.
1840 int inactive_shortage;
1841 int active_shortage;
1842 int vnodes_skipped = 0;
1843 int recycle_count = 0;
1847 * Wait for an action request. If we timeout check to
1848 * see if paging is needed (in case the normal wakeup
1851 if (vm_pages_needed == 0) {
1852 error = tsleep(&vm_pages_needed,
1854 vm_pageout_stats_interval * hz);
1856 vm_paging_needed() == 0 &&
1857 vm_pages_needed == 0) {
1858 for (q = 0; q < PQ_MAXL2_SIZE; ++q)
1859 vm_pageout_page_stats(q);
1862 vm_pages_needed = 1;
1865 mycpu->gd_cnt.v_pdwakeups++;
1868 * Do whatever cleanup that the pmap code can.
1873 * Scan for pageout. Try to avoid thrashing the system
1876 * Calculate our target for the number of free+cache pages we
1877 * want to get to. This is higher then the number that causes
1878 * allocations to stall (severe) in order to provide hysteresis,
1879 * and if we don't make it all the way but get to the minimum
1882 inactive_shortage = vm_paging_target() + vm_pageout_deficit;
1883 vm_pageout_deficit = 0;
1885 for (q = 0; q < PQ_MAXL2_SIZE; ++q) {
1886 delta1 += vm_pageout_scan_inactive(
1888 inactive_shortage / PQ_MAXL2_SIZE + 1,
1893 * Figure out how many active pages we must deactivate. If
1894 * we were able to reach our target with just the inactive
1895 * scan above we limit the number of active pages we
1896 * deactivate to reduce unnecessary work.
1898 active_shortage = vmstats.v_inactive_target -
1899 vmstats.v_inactive_count;
1901 tmp = inactive_shortage;
1902 if (tmp < vmstats.v_inactive_target / 10)
1903 tmp = vmstats.v_inactive_target / 10;
1904 inactive_shortage -= delta1;
1905 if (inactive_shortage <= 0 && active_shortage > tmp * 2)
1906 active_shortage = tmp * 2;
1909 for (q = 0; q < PQ_MAXL2_SIZE; ++q) {
1910 delta2 += vm_pageout_scan_active(
1912 inactive_shortage / PQ_MAXL2_SIZE + 1,
1913 active_shortage / PQ_MAXL2_SIZE + 1,
1918 * Finally free enough cache pages to meet our free page
1919 * requirement and take more drastic measures if we are
1922 inactive_shortage -= delta2;
1923 vm_pageout_scan_cache(inactive_shortage, vnodes_skipped,
1927 * Wait for more work.
1929 if (inactive_shortage > 0) {
1931 if (swap_pager_full) {
1933 * Running out of memory, catastrophic back-off
1934 * to one-second intervals.
1936 tsleep(&vm_pages_needed, 0, "pdelay", hz);
1937 } else if (pass < 10 && vm_pages_needed > 1) {
1939 * Normal operation, additional processes
1940 * have already kicked us. Retry immediately.
1942 } else if (pass < 10) {
1944 * Normal operation, fewer processes. Delay
1945 * a bit but allow wakeups.
1947 vm_pages_needed = 0;
1948 tsleep(&vm_pages_needed, 0, "pdelay", hz / 10);
1949 vm_pages_needed = 1;
1952 * We've taken too many passes, forced delay.
1954 tsleep(&vm_pages_needed, 0, "pdelay", hz / 10);
1958 * Interlocked wakeup of waiters (non-optional)
1961 if (vm_pages_needed && !vm_page_count_min(0)) {
1962 wakeup(&vmstats.v_free_count);
1963 vm_pages_needed = 0;
1969 static struct kproc_desc page_kp = {
1974 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start, &page_kp)
1978 * Called after allocating a page out of the cache or free queue
1979 * to possibly wake the pagedaemon up to replentish our supply.
1981 * We try to generate some hysteresis by waking the pagedaemon up
1982 * when our free+cache pages go below the free_min+cache_min level.
1983 * The pagedaemon tries to get the count back up to at least the
1984 * minimum, and through to the target level if possible.
1986 * If the pagedaemon is already active bump vm_pages_needed as a hint
1987 * that there are even more requests pending.
1993 pagedaemon_wakeup(void)
1995 if (vm_paging_needed() && curthread != pagethread) {
1996 if (vm_pages_needed == 0) {
1997 vm_pages_needed = 1; /* SMP race ok */
1998 wakeup(&vm_pages_needed);
1999 } else if (vm_page_count_min(0)) {
2000 ++vm_pages_needed; /* SMP race ok */
2005 #if !defined(NO_SWAPPING)
2012 vm_req_vmdaemon(void)
2014 static int lastrun = 0;
2016 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
2017 wakeup(&vm_daemon_needed);
2022 static int vm_daemon_callback(struct proc *p, void *data __unused);
2031 * XXX vm_daemon_needed specific token?
2034 tsleep(&vm_daemon_needed, 0, "psleep", 0);
2035 if (vm_pageout_req_swapout) {
2036 swapout_procs(vm_pageout_req_swapout);
2037 vm_pageout_req_swapout = 0;
2040 * scan the processes for exceeding their rlimits or if
2041 * process is swapped out -- deactivate pages
2043 allproc_scan(vm_daemon_callback, NULL);
2048 * Caller must hold proc_token.
2051 vm_daemon_callback(struct proc *p, void *data __unused)
2053 vm_pindex_t limit, size;
2056 * if this is a system process or if we have already
2057 * looked at this process, skip it.
2059 if (p->p_flag & (P_SYSTEM | P_WEXIT))
2063 * if the process is in a non-running type state,
2066 if (p->p_stat != SACTIVE && p->p_stat != SSTOP)
2072 limit = OFF_TO_IDX(qmin(p->p_rlimit[RLIMIT_RSS].rlim_cur,
2073 p->p_rlimit[RLIMIT_RSS].rlim_max));
2076 * let processes that are swapped out really be
2077 * swapped out. Set the limit to nothing to get as
2078 * many pages out to swap as possible.
2080 if (p->p_flag & P_SWAPPEDOUT)
2083 lwkt_gettoken(&p->p_vmspace->vm_map.token);
2084 size = vmspace_resident_count(p->p_vmspace);
2085 if (limit >= 0 && size >= limit) {
2086 vm_pageout_map_deactivate_pages(&p->p_vmspace->vm_map, limit);
2088 lwkt_reltoken(&p->p_vmspace->vm_map.token);