2 * Copyright (c) 1991 Regents of the University of California.
4 * Copyright (c) 1994 John S. Dyson
6 * Copyright (c) 1994 David Greenman
9 * This code is derived from software contributed to Berkeley by
10 * The Mach Operating System project at Carnegie-Mellon University.
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Berkeley and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
40 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
43 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
44 * All rights reserved.
46 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
48 * Permission to use, copy, modify and distribute this software and
49 * its documentation is hereby granted, provided that both the copyright
50 * notice and this permission notice appear in all copies of the
51 * software, derivative works or modified versions, and any portions
52 * thereof, and that both notices appear in supporting documentation.
54 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
55 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
56 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
58 * Carnegie Mellon requests users of this software to return to
60 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
61 * School of Computer Science
62 * Carnegie Mellon University
63 * Pittsburgh PA 15213-3890
65 * any improvements or extensions that they make and grant Carnegie the
66 * rights to redistribute these changes.
68 * $FreeBSD: src/sys/vm/vm_pageout.c,v 1.151.2.15 2002/12/29 18:21:04 dillon Exp $
69 * $DragonFly: src/sys/vm/vm_pageout.c,v 1.36 2008/07/01 02:02:56 dillon Exp $
73 * The proverbial page-out daemon.
77 #include <sys/param.h>
78 #include <sys/systm.h>
79 #include <sys/kernel.h>
81 #include <sys/kthread.h>
82 #include <sys/resourcevar.h>
83 #include <sys/signalvar.h>
84 #include <sys/vnode.h>
85 #include <sys/vmmeter.h>
86 #include <sys/sysctl.h>
89 #include <vm/vm_param.h>
91 #include <vm/vm_object.h>
92 #include <vm/vm_page.h>
93 #include <vm/vm_map.h>
94 #include <vm/vm_pageout.h>
95 #include <vm/vm_pager.h>
96 #include <vm/swap_pager.h>
97 #include <vm/vm_extern.h>
99 #include <sys/thread2.h>
100 #include <vm/vm_page2.h>
103 * System initialization
106 /* the kernel process "vm_pageout"*/
107 static void vm_pageout (void);
108 static int vm_pageout_clean (vm_page_t);
109 static int vm_pageout_scan (int pass);
110 static int vm_pageout_free_page_calc (vm_size_t count);
111 struct thread *pagethread;
113 static struct kproc_desc page_kp = {
118 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start, &page_kp)
120 #if !defined(NO_SWAPPING)
121 /* the kernel process "vm_daemon"*/
122 static void vm_daemon (void);
123 static struct thread *vmthread;
125 static struct kproc_desc vm_kp = {
130 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp)
134 int vm_pages_needed=0; /* Event on which pageout daemon sleeps */
135 int vm_pageout_deficit=0; /* Estimated number of pages deficit */
136 int vm_pageout_pages_needed=0; /* flag saying that the pageout daemon needs pages */
138 #if !defined(NO_SWAPPING)
139 static int vm_pageout_req_swapout; /* XXX */
140 static int vm_daemon_needed;
142 static int vm_max_launder = 32;
143 static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0;
144 static int vm_pageout_full_stats_interval = 0;
145 static int vm_pageout_stats_free_max=0, vm_pageout_algorithm=0;
146 static int defer_swap_pageouts=0;
147 static int disable_swap_pageouts=0;
149 #if defined(NO_SWAPPING)
150 static int vm_swap_enabled=0;
151 static int vm_swap_idle_enabled=0;
153 static int vm_swap_enabled=1;
154 static int vm_swap_idle_enabled=0;
157 SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm,
158 CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt");
160 SYSCTL_INT(_vm, OID_AUTO, max_launder,
161 CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
163 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max,
164 CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length");
166 SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval,
167 CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan");
169 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval,
170 CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan");
172 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_free_max,
173 CTLFLAG_RW, &vm_pageout_stats_free_max, 0, "Not implemented");
175 #if defined(NO_SWAPPING)
176 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
177 CTLFLAG_RD, &vm_swap_enabled, 0, "");
178 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
179 CTLFLAG_RD, &vm_swap_idle_enabled, 0, "");
181 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
182 CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
183 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
184 CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
187 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
188 CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
190 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
191 CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
193 static int pageout_lock_miss;
194 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
195 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
198 SYSCTL_INT(_vm, OID_AUTO, vm_load,
199 CTLFLAG_RD, &vm_load, 0, "load on the VM system");
200 int vm_load_enable = 1;
201 SYSCTL_INT(_vm, OID_AUTO, vm_load_enable,
202 CTLFLAG_RW, &vm_load_enable, 0, "enable vm_load rate limiting");
205 SYSCTL_INT(_vm, OID_AUTO, vm_load_debug,
206 CTLFLAG_RW, &vm_load_debug, 0, "debug vm_load");
209 #define VM_PAGEOUT_PAGE_COUNT 16
210 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
212 int vm_page_max_wired; /* XXX max # of wired pages system-wide */
214 #if !defined(NO_SWAPPING)
215 typedef void freeer_fcn_t (vm_map_t, vm_object_t, vm_pindex_t, int);
216 static void vm_pageout_map_deactivate_pages (vm_map_t, vm_pindex_t);
217 static freeer_fcn_t vm_pageout_object_deactivate_pages;
218 static void vm_req_vmdaemon (void);
220 static void vm_pageout_page_stats(void);
223 * Update vm_load to slow down faulting processes.
226 vm_fault_ratecheck(void)
228 if (vm_pages_needed) {
240 * Clean the page and remove it from the laundry. The page must not be
243 * We set the busy bit to cause potential page faults on this page to
244 * block. Note the careful timing, however, the busy bit isn't set till
245 * late and we cannot do anything that will mess with the page.
249 vm_pageout_clean(vm_page_t m)
252 vm_page_t mc[2*vm_pageout_page_count];
254 int ib, is, page_base;
255 vm_pindex_t pindex = m->pindex;
260 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
261 * with the new swapper, but we could have serious problems paging
262 * out other object types if there is insufficient memory.
264 * Unfortunately, checking free memory here is far too late, so the
265 * check has been moved up a procedural level.
269 * Don't mess with the page if it's busy, held, or special
271 if ((m->hold_count != 0) ||
272 ((m->busy != 0) || (m->flags & (PG_BUSY|PG_UNMANAGED)))) {
276 mc[vm_pageout_page_count] = m;
278 page_base = vm_pageout_page_count;
283 * Scan object for clusterable pages.
285 * We can cluster ONLY if: ->> the page is NOT
286 * clean, wired, busy, held, or mapped into a
287 * buffer, and one of the following:
288 * 1) The page is inactive, or a seldom used
291 * 2) we force the issue.
293 * During heavy mmap/modification loads the pageout
294 * daemon can really fragment the underlying file
295 * due to flushing pages out of order and not trying
296 * align the clusters (which leave sporatic out-of-order
297 * holes). To solve this problem we do the reverse scan
298 * first and attempt to align our cluster, then do a
299 * forward scan if room remains.
303 while (ib && pageout_count < vm_pageout_page_count) {
311 if ((p = vm_page_lookup(object, pindex - ib)) == NULL) {
315 if (((p->queue - p->pc) == PQ_CACHE) ||
316 (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) {
320 vm_page_test_dirty(p);
321 if ((p->dirty & p->valid) == 0 ||
322 p->queue != PQ_INACTIVE ||
323 p->wire_count != 0 || /* may be held by buf cache */
324 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 if ((p = vm_page_lookup(object, pindex + is)) == NULL)
345 if (((p->queue - p->pc) == PQ_CACHE) ||
346 (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) {
349 vm_page_test_dirty(p);
350 if ((p->dirty & p->valid) == 0 ||
351 p->queue != PQ_INACTIVE ||
352 p->wire_count != 0 || /* may be held by buf cache */
353 p->hold_count != 0) { /* may be undergoing I/O */
356 mc[page_base + pageout_count] = p;
362 * If we exhausted our forward scan, continue with the reverse scan
363 * when possible, even past a page boundry. This catches boundry
366 if (ib && pageout_count < vm_pageout_page_count)
370 * we allow reads during pageouts...
372 return vm_pageout_flush(&mc[page_base], pageout_count, 0);
376 * vm_pageout_flush() - launder the given pages
378 * The given pages are laundered. Note that we setup for the start of
379 * I/O ( i.e. busy the page ), mark it read-only, and bump the object
380 * reference count all in here rather then in the parent. If we want
381 * the parent to do more sophisticated things we may have to change
385 vm_pageout_flush(vm_page_t *mc, int count, int flags)
388 int pageout_status[count];
393 * Initiate I/O. Bump the vm_page_t->busy counter.
395 for (i = 0; i < count; i++) {
396 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL, ("vm_pageout_flush page %p index %d/%d: partially invalid page", mc[i], i, count));
397 vm_page_io_start(mc[i]);
401 * We must make the pages read-only. This will also force the
402 * modified bit in the related pmaps to be cleared. The pager
403 * cannot clear the bit for us since the I/O completion code
404 * typically runs from an interrupt. The act of making the page
405 * read-only handles the case for us.
407 for (i = 0; i < count; i++) {
408 vm_page_protect(mc[i], VM_PROT_READ);
411 object = mc[0]->object;
412 vm_object_pip_add(object, count);
414 vm_pager_put_pages(object, mc, count,
415 (flags | ((object == &kernel_object) ? VM_PAGER_PUT_SYNC : 0)),
418 for (i = 0; i < count; i++) {
419 vm_page_t mt = mc[i];
421 switch (pageout_status[i]) {
430 * Page outside of range of object. Right now we
431 * essentially lose the changes by pretending it
434 pmap_clear_modify(mt);
440 * A page typically cannot be paged out when we
441 * have run out of swap. We leave the page
442 * marked inactive and will try to page it out
445 * Starvation of the active page list is used to
446 * determine when the system is massively memory
455 * If the operation is still going, leave the page busy to
456 * block all other accesses. Also, leave the paging in
457 * progress indicator set so that we don't attempt an object
460 * For any pages which have completed synchronously,
461 * deactivate the page if we are under a severe deficit.
462 * Do not try to enter them into the cache, though, they
463 * might still be read-heavy.
465 if (pageout_status[i] != VM_PAGER_PEND) {
466 vm_object_pip_wakeup(object);
467 vm_page_io_finish(mt);
468 if (vm_page_count_severe())
469 vm_page_deactivate(mt);
471 if (!vm_page_count_severe() || !vm_page_try_to_cache(mt))
472 vm_page_protect(mt, VM_PROT_READ);
479 #if !defined(NO_SWAPPING)
481 * vm_pageout_object_deactivate_pages
483 * deactivate enough pages to satisfy the inactive target
484 * requirements or if vm_page_proc_limit is set, then
485 * deactivate all of the pages in the object and its
488 * The object and map must be locked.
490 static int vm_pageout_object_deactivate_pages_callback(vm_page_t, void *);
493 vm_pageout_object_deactivate_pages(vm_map_t map, vm_object_t object,
494 vm_pindex_t desired, int map_remove_only)
496 struct rb_vm_page_scan_info info;
499 if (object->type == OBJT_DEVICE || object->type == OBJT_PHYS)
503 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
505 if (object->paging_in_progress)
508 remove_mode = map_remove_only;
509 if (object->shadow_count > 1)
513 * scan the objects entire memory queue. spl protection is
514 * required to avoid an interrupt unbusy/free race against
518 info.limit = remove_mode;
520 info.desired = desired;
521 vm_page_rb_tree_RB_SCAN(&object->rb_memq, NULL,
522 vm_pageout_object_deactivate_pages_callback,
526 object = object->backing_object;
531 vm_pageout_object_deactivate_pages_callback(vm_page_t p, void *data)
533 struct rb_vm_page_scan_info *info = data;
536 if (pmap_resident_count(vm_map_pmap(info->map)) <= info->desired) {
539 mycpu->gd_cnt.v_pdpages++;
540 if (p->wire_count != 0 || p->hold_count != 0 || p->busy != 0 ||
541 (p->flags & (PG_BUSY|PG_UNMANAGED)) ||
542 !pmap_page_exists_quick(vm_map_pmap(info->map), p)) {
546 actcount = pmap_ts_referenced(p);
548 vm_page_flag_set(p, PG_REFERENCED);
549 } else if (p->flags & PG_REFERENCED) {
553 if ((p->queue != PQ_ACTIVE) &&
554 (p->flags & PG_REFERENCED)) {
556 p->act_count += actcount;
557 vm_page_flag_clear(p, PG_REFERENCED);
558 } else if (p->queue == PQ_ACTIVE) {
559 if ((p->flags & PG_REFERENCED) == 0) {
560 p->act_count -= min(p->act_count, ACT_DECLINE);
561 if (!info->limit && (vm_pageout_algorithm || (p->act_count == 0))) {
563 vm_page_protect(p, VM_PROT_NONE);
565 vm_page_deactivate(p);
567 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, p, pageq);
568 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, p, pageq);
572 vm_page_flag_clear(p, PG_REFERENCED);
573 if (p->act_count < (ACT_MAX - ACT_ADVANCE))
574 p->act_count += ACT_ADVANCE;
575 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, p, pageq);
576 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, p, pageq);
578 } else if (p->queue == PQ_INACTIVE) {
580 vm_page_protect(p, VM_PROT_NONE);
587 * deactivate some number of pages in a map, try to do it fairly, but
588 * that is really hard to do.
591 vm_pageout_map_deactivate_pages(vm_map_t map, vm_pindex_t desired)
594 vm_object_t obj, bigobj;
597 if (lockmgr(&map->lock, LK_EXCLUSIVE | LK_NOWAIT)) {
605 * first, search out the biggest object, and try to free pages from
608 tmpe = map->header.next;
609 while (tmpe != &map->header) {
610 switch(tmpe->maptype) {
611 case VM_MAPTYPE_NORMAL:
612 case VM_MAPTYPE_VPAGETABLE:
613 obj = tmpe->object.vm_object;
614 if ((obj != NULL) && (obj->shadow_count <= 1) &&
616 (bigobj->resident_page_count < obj->resident_page_count))) {
623 if (tmpe->wired_count > 0)
624 nothingwired = FALSE;
629 vm_pageout_object_deactivate_pages(map, bigobj, desired, 0);
632 * Next, hunt around for other pages to deactivate. We actually
633 * do this search sort of wrong -- .text first is not the best idea.
635 tmpe = map->header.next;
636 while (tmpe != &map->header) {
637 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
639 switch(tmpe->maptype) {
640 case VM_MAPTYPE_NORMAL:
641 case VM_MAPTYPE_VPAGETABLE:
642 obj = tmpe->object.vm_object;
644 vm_pageout_object_deactivate_pages(map, obj, desired, 0);
653 * Remove all mappings if a process is swapped out, this will free page
656 if (desired == 0 && nothingwired)
657 pmap_remove(vm_map_pmap(map),
658 VM_MIN_USER_ADDRESS, VM_MAX_USER_ADDRESS);
664 * Don't try to be fancy - being fancy can lead to vnode deadlocks. We
665 * only do it for OBJT_DEFAULT and OBJT_SWAP objects which we know can
666 * be trivially freed.
669 vm_pageout_page_free(vm_page_t m)
671 vm_object_t object = m->object;
672 int type = object->type;
674 if (type == OBJT_SWAP || type == OBJT_DEFAULT)
675 vm_object_reference(object);
677 vm_page_protect(m, VM_PROT_NONE);
679 if (type == OBJT_SWAP || type == OBJT_DEFAULT)
680 vm_object_deallocate(object);
684 * vm_pageout_scan does the dirty work for the pageout daemon.
686 struct vm_pageout_scan_info {
687 struct proc *bigproc;
691 static int vm_pageout_scan_callback(struct proc *p, void *data);
694 vm_pageout_scan(int pass)
696 struct vm_pageout_scan_info info;
698 struct vm_page marker;
699 struct vnode *vpfailed; /* warning, allowed to be stale */
702 int inactive_shortage, active_shortage;
703 int inactive_original_shortage;
706 int vnodes_skipped = 0;
710 * Do whatever cleanup that the pmap code can.
715 * Calculate our target for the number of free+cache pages we
716 * want to get to. This is higher then the number that causes
717 * allocations to stall (severe) in order to provide hysteresis,
718 * and if we don't make it all the way but get to the minimum
721 inactive_shortage = vm_paging_target() + vm_pageout_deficit;
722 inactive_original_shortage = inactive_shortage;
723 vm_pageout_deficit = 0;
726 * Initialize our marker
728 bzero(&marker, sizeof(marker));
729 marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
730 marker.queue = PQ_INACTIVE;
731 marker.wire_count = 1;
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 * We will generally be in a critical section throughout the
756 * scan, but we can release it temporarily when we are sitting on a
757 * non-busy page without fear. this is required to prevent an
758 * interrupt from unbusying or freeing a page prior to our busy
759 * check, leaving us on the wrong queue or checking the wrong
765 maxscan = vmstats.v_inactive_count;
766 for (m = TAILQ_FIRST(&vm_page_queues[PQ_INACTIVE].pl);
767 m != NULL && maxscan-- > 0 && inactive_shortage > 0;
770 mycpu->gd_cnt.v_pdpages++;
773 * Give interrupts a chance
779 * It's easier for some of the conditions below to just loop
780 * and catch queue changes here rather then check everywhere
783 if (m->queue != PQ_INACTIVE)
785 next = TAILQ_NEXT(m, pageq);
790 if (m->flags & PG_MARKER)
794 * A held page may be undergoing I/O, so skip it.
797 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
798 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
799 ++vm_swapcache_inactive_heuristic;
804 * Dont mess with busy pages, keep in the front of the
805 * queue, most likely are being paged out.
807 if (m->busy || (m->flags & PG_BUSY)) {
811 if (m->object->ref_count == 0) {
813 * If the object is not being used, we ignore previous
816 vm_page_flag_clear(m, PG_REFERENCED);
817 pmap_clear_reference(m);
819 } else if (((m->flags & PG_REFERENCED) == 0) &&
820 (actcount = pmap_ts_referenced(m))) {
822 * Otherwise, if the page has been referenced while
823 * in the inactive queue, we bump the "activation
824 * count" upwards, making it less likely that the
825 * page will be added back to the inactive queue
826 * prematurely again. Here we check the page tables
827 * (or emulated bits, if any), given the upper level
828 * VM system not knowing anything about existing
832 m->act_count += (actcount + ACT_ADVANCE);
837 * If the upper level VM system knows about any page
838 * references, we activate the page. We also set the
839 * "activation count" higher than normal so that we will less
840 * likely place pages back onto the inactive queue again.
842 if ((m->flags & PG_REFERENCED) != 0) {
843 vm_page_flag_clear(m, PG_REFERENCED);
844 actcount = pmap_ts_referenced(m);
846 m->act_count += (actcount + ACT_ADVANCE + 1);
851 * If the upper level VM system doesn't know anything about
852 * the page being dirty, we have to check for it again. As
853 * far as the VM code knows, any partially dirty pages are
856 * Pages marked PG_WRITEABLE may be mapped into the user
857 * address space of a process running on another cpu. A
858 * user process (without holding the MP lock) running on
859 * another cpu may be able to touch the page while we are
860 * trying to remove it. vm_page_cache() will handle this
864 vm_page_test_dirty(m);
871 * Invalid pages can be easily freed
873 vm_pageout_page_free(m);
874 mycpu->gd_cnt.v_dfree++;
876 } else if (m->dirty == 0) {
878 * Clean pages can be placed onto the cache queue.
879 * This effectively frees them.
883 } else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) {
885 * Dirty pages need to be paged out, but flushing
886 * a page is extremely expensive verses freeing
887 * a clean page. Rather then artificially limiting
888 * the number of pages we can flush, we instead give
889 * dirty pages extra priority on the inactive queue
890 * by forcing them to be cycled through the queue
891 * twice before being flushed, after which the
892 * (now clean) page will cycle through once more
893 * before being freed. This significantly extends
894 * the thrash point for a heavily loaded machine.
896 vm_page_flag_set(m, PG_WINATCFLS);
897 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
898 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
899 ++vm_swapcache_inactive_heuristic;
900 } else if (maxlaunder > 0) {
902 * We always want to try to flush some dirty pages if
903 * we encounter them, to keep the system stable.
904 * Normally this number is small, but under extreme
905 * pressure where there are insufficient clean pages
906 * on the inactive queue, we may have to go all out.
908 int swap_pageouts_ok;
909 struct vnode *vp = NULL;
913 if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
914 swap_pageouts_ok = 1;
916 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
917 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
918 vm_page_count_min(0));
923 * We don't bother paging objects that are "dead".
924 * Those objects are in a "rundown" state.
926 if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
927 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
928 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
929 ++vm_swapcache_inactive_heuristic;
934 * The object is already known NOT to be dead. It
935 * is possible for the vget() to block the whole
936 * pageout daemon, but the new low-memory handling
937 * code should prevent it.
939 * The previous code skipped locked vnodes and, worse,
940 * reordered pages in the queue. This results in
941 * completely non-deterministic operation because,
942 * quite often, a vm_fault has initiated an I/O and
943 * is holding a locked vnode at just the point where
944 * the pageout daemon is woken up.
946 * We can't wait forever for the vnode lock, we might
947 * deadlock due to a vn_read() getting stuck in
948 * vm_wait while holding this vnode. We skip the
949 * vnode if we can't get it in a reasonable amount
952 * vpfailed is used to (try to) avoid the case where
953 * a large number of pages are associated with a
954 * locked vnode, which could cause the pageout daemon
955 * to stall for an excessive amount of time.
957 if (object->type == OBJT_VNODE) {
961 flags = LK_EXCLUSIVE | LK_NOOBJ;
965 flags |= LK_TIMELOCK;
966 if (vget(vp, flags) != 0) {
969 if (object->flags & OBJ_MIGHTBEDIRTY)
975 * The page might have been moved to another
976 * queue during potential blocking in vget()
977 * above. The page might have been freed and
978 * reused for another vnode. The object might
979 * have been reused for another vnode.
981 if (m->queue != PQ_INACTIVE ||
982 m->object != object ||
983 object->handle != vp) {
984 if (object->flags & OBJ_MIGHTBEDIRTY)
991 * The page may have been busied during the
992 * blocking in vput(); We don't move the
993 * page back onto the end of the queue so that
994 * statistics are more correct if we don't.
996 if (m->busy || (m->flags & PG_BUSY)) {
1002 * If the page has become held it might
1003 * be undergoing I/O, so skip it
1005 if (m->hold_count) {
1006 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
1007 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
1008 ++vm_swapcache_inactive_heuristic;
1009 if (object->flags & OBJ_MIGHTBEDIRTY)
1017 * If a page is dirty, then it is either being washed
1018 * (but not yet cleaned) or it is still in the
1019 * laundry. If it is still in the laundry, then we
1020 * start the cleaning operation.
1022 * This operation may cluster, invalidating the 'next'
1023 * pointer. To prevent an inordinate number of
1024 * restarts we use our marker to remember our place.
1026 * decrement inactive_shortage on success to account
1027 * for the (future) cleaned page. Otherwise we
1028 * could wind up laundering or cleaning too many
1031 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE].pl, m, &marker, pageq);
1032 if (vm_pageout_clean(m) != 0) {
1033 --inactive_shortage;
1036 next = TAILQ_NEXT(&marker, pageq);
1037 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, &marker, pageq);
1044 * We want to move pages from the active queue to the inactive
1045 * queue to get the inactive queue to the inactive target. If
1046 * we still have a page shortage from above we try to directly free
1047 * clean pages instead of moving them.
1049 * If we do still have a shortage we keep track of the number of
1050 * pages we free or cache (recycle_count) as a measure of thrashing
1051 * between the active and inactive queues.
1053 * If we were able to completely satisfy the free+cache targets
1054 * from the inactive pool we limit the number of pages we move
1055 * from the active pool to the inactive pool to 2x the pages we
1056 * had removed from the inactive pool (with a minimum of 1/5 the
1057 * inactive target). If we were not able to completely satisfy
1058 * the free+cache targets we go for the whole target aggressively.
1060 * NOTE: Both variables can end up negative.
1061 * NOTE: We are still in a critical section.
1063 active_shortage = vmstats.v_inactive_target - vmstats.v_inactive_count;
1064 if (inactive_original_shortage < vmstats.v_inactive_target / 10)
1065 inactive_original_shortage = vmstats.v_inactive_target / 10;
1066 if (inactive_shortage <= 0 &&
1067 active_shortage > inactive_original_shortage * 2) {
1068 active_shortage = inactive_original_shortage * 2;
1071 pcount = vmstats.v_active_count;
1073 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
1075 while ((m != NULL) && (pcount-- > 0) &&
1076 (inactive_shortage > 0 || active_shortage > 0)
1079 * Give interrupts a chance.
1085 * If the page was ripped out from under us, just stop.
1087 if (m->queue != PQ_ACTIVE)
1089 next = TAILQ_NEXT(m, pageq);
1092 * Don't deactivate pages that are busy.
1094 if ((m->busy != 0) ||
1095 (m->flags & PG_BUSY) ||
1096 (m->hold_count != 0)) {
1097 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1098 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1104 * The count for pagedaemon pages is done after checking the
1105 * page for eligibility...
1107 mycpu->gd_cnt.v_pdpages++;
1110 * Check to see "how much" the page has been used and clear
1111 * the tracking access bits. If the object has no references
1112 * don't bother paying the expense.
1115 if (m->object->ref_count != 0) {
1116 if (m->flags & PG_REFERENCED)
1118 actcount += pmap_ts_referenced(m);
1120 m->act_count += ACT_ADVANCE + actcount;
1121 if (m->act_count > ACT_MAX)
1122 m->act_count = ACT_MAX;
1125 vm_page_flag_clear(m, PG_REFERENCED);
1128 * actcount is only valid if the object ref_count is non-zero.
1130 if (actcount && m->object->ref_count != 0) {
1131 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1132 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1134 m->act_count -= min(m->act_count, ACT_DECLINE);
1135 if (vm_pageout_algorithm ||
1136 m->object->ref_count == 0 ||
1137 m->act_count < pass + 1
1140 * Deactivate the page. If we had a
1141 * shortage from our inactive scan try to
1142 * free (cache) the page instead.
1144 * Don't just blindly cache the page if
1145 * we do not have a shortage from the
1146 * inactive scan, that could lead to
1147 * gigabytes being moved.
1150 if (inactive_shortage > 0 ||
1151 m->object->ref_count == 0) {
1152 if (inactive_shortage > 0)
1155 vm_page_protect(m, VM_PROT_NONE);
1157 if (m->dirty == 0 &&
1158 inactive_shortage > 0) {
1159 --inactive_shortage;
1162 vm_page_deactivate(m);
1165 vm_page_deactivate(m);
1168 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1169 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1176 * We try to maintain some *really* free pages, this allows interrupt
1177 * code to be guaranteed space. Since both cache and free queues
1178 * are considered basically 'free', moving pages from cache to free
1179 * does not effect other calculations.
1181 * NOTE: we are still in a critical section.
1183 * Pages moved from PQ_CACHE to totally free are not counted in the
1184 * pages_freed counter.
1186 while (vmstats.v_free_count < vmstats.v_free_reserved) {
1187 static int cache_rover = 0;
1188 m = vm_page_list_find(PQ_CACHE, cache_rover, FALSE);
1191 if ((m->flags & (PG_BUSY|PG_UNMANAGED)) ||
1196 kprintf("Warning: busy page %p found in cache\n", m);
1198 vm_page_deactivate(m);
1201 KKASSERT((m->flags & PG_MAPPED) == 0);
1202 KKASSERT(m->dirty == 0);
1203 cache_rover = (cache_rover + PQ_PRIME2) & PQ_L2_MASK;
1204 vm_pageout_page_free(m);
1205 mycpu->gd_cnt.v_dfree++;
1210 #if !defined(NO_SWAPPING)
1212 * Idle process swapout -- run once per second.
1214 if (vm_swap_idle_enabled) {
1216 if (time_second != lsec) {
1217 vm_pageout_req_swapout |= VM_SWAP_IDLE;
1225 * If we didn't get enough free pages, and we have skipped a vnode
1226 * in a writeable object, wakeup the sync daemon. And kick swapout
1227 * if we did not get enough free pages.
1229 if (vm_paging_target() > 0) {
1230 if (vnodes_skipped && vm_page_count_min(0))
1232 #if !defined(NO_SWAPPING)
1233 if (vm_swap_enabled && vm_page_count_target()) {
1235 vm_pageout_req_swapout |= VM_SWAP_NORMAL;
1241 * Handle catastrophic conditions. Under good conditions we should
1242 * be at the target, well beyond our minimum. If we could not even
1243 * reach our minimum the system is under heavy stress.
1245 * Determine whether we have run out of memory. This occurs when
1246 * swap_pager_full is TRUE and the only pages left in the page
1247 * queues are dirty. We will still likely have page shortages.
1249 * - swap_pager_full is set if insufficient swap was
1250 * available to satisfy a requested pageout.
1252 * - the inactive queue is bloated (4 x size of active queue),
1253 * meaning it is unable to get rid of dirty pages and.
1255 * - vm_page_count_min() without counting pages recycled from the
1256 * active queue (recycle_count) means we could not recover
1257 * enough pages to meet bare minimum needs. This test only
1258 * works if the inactive queue is bloated.
1260 * - due to a positive inactive_shortage we shifted the remaining
1261 * dirty pages from the active queue to the inactive queue
1262 * trying to find clean ones to free.
1264 if (swap_pager_full && vm_page_count_min(recycle_count))
1265 kprintf("Warning: system low on memory+swap!\n");
1266 if (swap_pager_full && vm_page_count_min(recycle_count) &&
1267 vmstats.v_inactive_count > vmstats.v_active_count * 4 &&
1268 inactive_shortage > 0) {
1272 info.bigproc = NULL;
1274 allproc_scan(vm_pageout_scan_callback, &info);
1275 if (info.bigproc != NULL) {
1276 killproc(info.bigproc, "out of swap space");
1277 info.bigproc->p_nice = PRIO_MIN;
1278 info.bigproc->p_usched->resetpriority(
1279 FIRST_LWP_IN_PROC(info.bigproc));
1280 wakeup(&vmstats.v_free_count);
1281 PRELE(info.bigproc);
1284 return(inactive_shortage);
1288 vm_pageout_scan_callback(struct proc *p, void *data)
1290 struct vm_pageout_scan_info *info = data;
1294 * Never kill system processes or init. If we have configured swap
1295 * then try to avoid killing low-numbered pids.
1297 if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) ||
1298 ((p->p_pid < 48) && (vm_swap_size != 0))) {
1303 * if the process is in a non-running type state,
1306 if (p->p_stat != SACTIVE && p->p_stat != SSTOP)
1310 * Get the approximate process size. Note that anonymous pages
1311 * with backing swap will be counted twice, but there should not
1312 * be too many such pages due to the stress the VM system is
1313 * under at this point.
1315 size = vmspace_anonymous_count(p->p_vmspace) +
1316 vmspace_swap_count(p->p_vmspace);
1319 * If the this process is bigger than the biggest one
1322 if (info->bigsize < size) {
1324 PRELE(info->bigproc);
1327 info->bigsize = size;
1333 * This routine tries to maintain the pseudo LRU active queue,
1334 * so that during long periods of time where there is no paging,
1335 * that some statistic accumulation still occurs. This code
1336 * helps the situation where paging just starts to occur.
1339 vm_pageout_page_stats(void)
1342 int pcount,tpcount; /* Number of pages to check */
1343 static int fullintervalcount = 0;
1347 (vmstats.v_inactive_target + vmstats.v_cache_max + vmstats.v_free_min) -
1348 (vmstats.v_free_count + vmstats.v_inactive_count + vmstats.v_cache_count);
1350 if (page_shortage <= 0)
1355 pcount = vmstats.v_active_count;
1356 fullintervalcount += vm_pageout_stats_interval;
1357 if (fullintervalcount < vm_pageout_full_stats_interval) {
1358 tpcount = (vm_pageout_stats_max * vmstats.v_active_count) / vmstats.v_page_count;
1359 if (pcount > tpcount)
1362 fullintervalcount = 0;
1365 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
1366 while ((m != NULL) && (pcount-- > 0)) {
1369 if (m->queue != PQ_ACTIVE) {
1373 next = TAILQ_NEXT(m, pageq);
1375 * Don't deactivate pages that are busy.
1377 if ((m->busy != 0) ||
1378 (m->flags & PG_BUSY) ||
1379 (m->hold_count != 0)) {
1380 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1381 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1387 if (m->flags & PG_REFERENCED) {
1388 vm_page_flag_clear(m, PG_REFERENCED);
1392 actcount += pmap_ts_referenced(m);
1394 m->act_count += ACT_ADVANCE + actcount;
1395 if (m->act_count > ACT_MAX)
1396 m->act_count = ACT_MAX;
1397 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1398 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1400 if (m->act_count == 0) {
1402 * We turn off page access, so that we have
1403 * more accurate RSS stats. We don't do this
1404 * in the normal page deactivation when the
1405 * system is loaded VM wise, because the
1406 * cost of the large number of page protect
1407 * operations would be higher than the value
1408 * of doing the operation.
1411 vm_page_protect(m, VM_PROT_NONE);
1413 vm_page_deactivate(m);
1415 m->act_count -= min(m->act_count, ACT_DECLINE);
1416 TAILQ_REMOVE(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1417 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1427 vm_pageout_free_page_calc(vm_size_t count)
1429 if (count < vmstats.v_page_count)
1432 * free_reserved needs to include enough for the largest swap pager
1433 * structures plus enough for any pv_entry structs when paging.
1435 if (vmstats.v_page_count > 1024)
1436 vmstats.v_free_min = 4 + (vmstats.v_page_count - 1024) / 200;
1438 vmstats.v_free_min = 4;
1439 vmstats.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
1440 vmstats.v_interrupt_free_min;
1441 vmstats.v_free_reserved = vm_pageout_page_count +
1442 vmstats.v_pageout_free_min + (count / 768) + PQ_L2_SIZE;
1443 vmstats.v_free_severe = vmstats.v_free_min / 2;
1444 vmstats.v_free_min += vmstats.v_free_reserved;
1445 vmstats.v_free_severe += vmstats.v_free_reserved;
1451 * vm_pageout is the high level pageout daemon.
1457 int inactive_shortage;
1460 * Initialize some paging parameters.
1462 curthread->td_flags |= TDF_SYSTHREAD;
1464 vmstats.v_interrupt_free_min = 2;
1465 if (vmstats.v_page_count < 2000)
1466 vm_pageout_page_count = 8;
1468 vm_pageout_free_page_calc(vmstats.v_page_count);
1471 * v_free_target and v_cache_min control pageout hysteresis. Note
1472 * that these are more a measure of the VM cache queue hysteresis
1473 * then the VM free queue. Specifically, v_free_target is the
1474 * high water mark (free+cache pages).
1476 * v_free_reserved + v_cache_min (mostly means v_cache_min) is the
1477 * low water mark, while v_free_min is the stop. v_cache_min must
1478 * be big enough to handle memory needs while the pageout daemon
1479 * is signalled and run to free more pages.
1481 if (vmstats.v_free_count > 6144)
1482 vmstats.v_free_target = 4 * vmstats.v_free_min + vmstats.v_free_reserved;
1484 vmstats.v_free_target = 2 * vmstats.v_free_min + vmstats.v_free_reserved;
1487 * NOTE: With the new buffer cache b_act_count we want the default
1488 * inactive target to be a percentage of available memory.
1490 * The inactive target essentially determines the minimum
1491 * number of 'temporary' pages capable of caching one-time-use
1492 * files when the VM system is otherwise full of pages
1493 * belonging to multi-time-use files or active program data.
1495 * NOTE: The inactive target is aggressively persued only if the
1496 * inactive queue becomes too small. If the inactive queue
1497 * is large enough to satisfy page movement to free+cache
1498 * then it is repopulated more slowly from the active queue.
1499 * This allows a general inactive_target default to be set.
1501 * There is an issue here for processes which sit mostly idle
1502 * 'overnight', such as sshd, tcsh, and X. Any movement from
1503 * the active queue will eventually cause such pages to
1504 * recycle eventually causing a lot of paging in the morning.
1505 * To reduce the incidence of this pages cycled out of the
1506 * buffer cache are moved directly to the inactive queue if
1507 * they were only used once or twice.
1509 * The vfs.vm_cycle_point sysctl can be used to adjust this.
1510 * Increasing the value (up to 64) increases the number of
1511 * buffer recyclements which go directly to the inactive queue.
1513 if (vmstats.v_free_count > 2048) {
1514 vmstats.v_cache_min = vmstats.v_free_target;
1515 vmstats.v_cache_max = 2 * vmstats.v_cache_min;
1517 vmstats.v_cache_min = 0;
1518 vmstats.v_cache_max = 0;
1520 vmstats.v_inactive_target = vmstats.v_free_count / 4;
1522 /* XXX does not really belong here */
1523 if (vm_page_max_wired == 0)
1524 vm_page_max_wired = vmstats.v_free_count / 3;
1526 if (vm_pageout_stats_max == 0)
1527 vm_pageout_stats_max = vmstats.v_free_target;
1530 * Set interval in seconds for stats scan.
1532 if (vm_pageout_stats_interval == 0)
1533 vm_pageout_stats_interval = 5;
1534 if (vm_pageout_full_stats_interval == 0)
1535 vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
1539 * Set maximum free per pass
1541 if (vm_pageout_stats_free_max == 0)
1542 vm_pageout_stats_free_max = 5;
1544 swap_pager_swap_init();
1548 * The pageout daemon is never done, so loop forever.
1554 * Wait for an action request
1557 if (vm_pages_needed == 0) {
1558 error = tsleep(&vm_pages_needed,
1560 vm_pageout_stats_interval * hz);
1561 if (error && vm_pages_needed == 0) {
1562 vm_pageout_page_stats();
1565 vm_pages_needed = 1;
1570 * If we have enough free memory, wakeup waiters.
1571 * (This is optional here)
1574 if (!vm_page_count_min(0))
1575 wakeup(&vmstats.v_free_count);
1576 mycpu->gd_cnt.v_pdwakeups++;
1580 * Scan for pageout. Try to avoid thrashing the system
1583 inactive_shortage = vm_pageout_scan(pass);
1584 if (inactive_shortage > 0) {
1586 if (swap_pager_full) {
1588 * Running out of memory, catastrophic back-off
1589 * to one-second intervals.
1591 tsleep(&vm_pages_needed, 0, "pdelay", hz);
1592 } else if (pass < 10 && vm_pages_needed > 1) {
1594 * Normal operation, additional processes
1595 * have already kicked us. Retry immediately.
1597 } else if (pass < 10) {
1599 * Normal operation, fewer processes. Delay
1600 * a bit but allow wakeups.
1602 vm_pages_needed = 0;
1603 tsleep(&vm_pages_needed, 0, "pdelay", hz / 10);
1604 vm_pages_needed = 1;
1607 * We've taken too many passes, forced delay.
1609 tsleep(&vm_pages_needed, 0, "pdelay", hz / 10);
1613 * Interlocked wakeup of waiters (non-optional)
1616 if (vm_pages_needed && !vm_page_count_min(0)) {
1617 wakeup(&vmstats.v_free_count);
1618 vm_pages_needed = 0;
1625 * Called after allocating a page out of the cache or free queue
1626 * to possibly wake the pagedaemon up to replentish our supply.
1628 * We try to generate some hysteresis by waking the pagedaemon up
1629 * when our free+cache pages go below the severe level. The pagedaemon
1630 * tries to get the count back up to at least the minimum, and through
1631 * to the target level if possible.
1633 * If the pagedaemon is already active bump vm_pages_needed as a hint
1634 * that there are even more requests pending.
1637 pagedaemon_wakeup(void)
1639 if (vm_page_count_severe() && curthread != pagethread) {
1640 if (vm_pages_needed == 0) {
1641 vm_pages_needed = 1;
1642 wakeup(&vm_pages_needed);
1643 } else if (vm_page_count_min(0)) {
1649 #if !defined(NO_SWAPPING)
1651 vm_req_vmdaemon(void)
1653 static int lastrun = 0;
1655 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
1656 wakeup(&vm_daemon_needed);
1661 static int vm_daemon_callback(struct proc *p, void *data __unused);
1667 tsleep(&vm_daemon_needed, 0, "psleep", 0);
1668 if (vm_pageout_req_swapout) {
1669 swapout_procs(vm_pageout_req_swapout);
1670 vm_pageout_req_swapout = 0;
1673 * scan the processes for exceeding their rlimits or if
1674 * process is swapped out -- deactivate pages
1676 allproc_scan(vm_daemon_callback, NULL);
1681 vm_daemon_callback(struct proc *p, void *data __unused)
1683 vm_pindex_t limit, size;
1686 * if this is a system process or if we have already
1687 * looked at this process, skip it.
1689 if (p->p_flag & (P_SYSTEM | P_WEXIT))
1693 * if the process is in a non-running type state,
1696 if (p->p_stat != SACTIVE && p->p_stat != SSTOP)
1702 limit = OFF_TO_IDX(qmin(p->p_rlimit[RLIMIT_RSS].rlim_cur,
1703 p->p_rlimit[RLIMIT_RSS].rlim_max));
1706 * let processes that are swapped out really be
1707 * swapped out. Set the limit to nothing to get as
1708 * many pages out to swap as possible.
1710 if (p->p_flag & P_SWAPPEDOUT)
1713 size = vmspace_resident_count(p->p_vmspace);
1714 if (limit >= 0 && size >= limit) {
1715 vm_pageout_map_deactivate_pages(
1716 &p->p_vmspace->vm_map, limit);