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 * 3. All advertising materials mentioning features or use of this software
23 * must display the following acknowledgement:
24 * This product includes software developed by the University of
25 * California, Berkeley and its contributors.
26 * 4. Neither the name of the University nor the names of its contributors
27 * may be used to endorse or promote products derived from this software
28 * without specific prior written permission.
30 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
42 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
45 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
46 * All rights reserved.
48 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
50 * Permission to use, copy, modify and distribute this software and
51 * its documentation is hereby granted, provided that both the copyright
52 * notice and this permission notice appear in all copies of the
53 * software, derivative works or modified versions, and any portions
54 * thereof, and that both notices appear in supporting documentation.
56 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
57 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
58 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
60 * Carnegie Mellon requests users of this software to return to
62 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
63 * School of Computer Science
64 * Carnegie Mellon University
65 * Pittsburgh PA 15213-3890
67 * any improvements or extensions that they make and grant Carnegie the
68 * rights to redistribute these changes.
70 * $FreeBSD: src/sys/vm/vm_pageout.c,v 1.151.2.15 2002/12/29 18:21:04 dillon Exp $
71 * $DragonFly: src/sys/vm/vm_pageout.c,v 1.36 2008/07/01 02:02:56 dillon Exp $
75 * The proverbial page-out daemon.
79 #include <sys/param.h>
80 #include <sys/systm.h>
81 #include <sys/kernel.h>
83 #include <sys/kthread.h>
84 #include <sys/resourcevar.h>
85 #include <sys/signalvar.h>
86 #include <sys/vnode.h>
87 #include <sys/vmmeter.h>
88 #include <sys/sysctl.h>
91 #include <vm/vm_param.h>
93 #include <vm/vm_object.h>
94 #include <vm/vm_page.h>
95 #include <vm/vm_map.h>
96 #include <vm/vm_pageout.h>
97 #include <vm/vm_pager.h>
98 #include <vm/swap_pager.h>
99 #include <vm/vm_extern.h>
101 #include <sys/thread2.h>
102 #include <sys/mplock2.h>
103 #include <vm/vm_page2.h>
106 * System initialization
109 /* the kernel process "vm_pageout"*/
110 static int vm_pageout_clean (vm_page_t
);
111 static int vm_pageout_scan (int pass
);
112 static int vm_pageout_free_page_calc (vm_size_t count
);
113 struct thread
*pagethread
;
115 #if !defined(NO_SWAPPING)
116 /* the kernel process "vm_daemon"*/
117 static void vm_daemon (void);
118 static struct thread
*vmthread
;
120 static struct kproc_desc vm_kp
= {
125 SYSINIT(vmdaemon
, SI_SUB_KTHREAD_VM
, SI_ORDER_FIRST
, kproc_start
, &vm_kp
)
129 int vm_pages_needed
=0; /* Event on which pageout daemon sleeps */
130 int vm_pageout_deficit
=0; /* Estimated number of pages deficit */
131 int vm_pageout_pages_needed
=0; /* flag saying that the pageout daemon needs pages */
133 #if !defined(NO_SWAPPING)
134 static int vm_pageout_req_swapout
; /* XXX */
135 static int vm_daemon_needed
;
137 static int vm_max_launder
= 32;
138 static int vm_pageout_stats_max
=0, vm_pageout_stats_interval
= 0;
139 static int vm_pageout_full_stats_interval
= 0;
140 static int vm_pageout_stats_free_max
=0, vm_pageout_algorithm
=0;
141 static int defer_swap_pageouts
=0;
142 static int disable_swap_pageouts
=0;
144 #if defined(NO_SWAPPING)
145 static int vm_swap_enabled
=0;
146 static int vm_swap_idle_enabled
=0;
148 static int vm_swap_enabled
=1;
149 static int vm_swap_idle_enabled
=0;
152 SYSCTL_INT(_vm
, VM_PAGEOUT_ALGORITHM
, pageout_algorithm
,
153 CTLFLAG_RW
, &vm_pageout_algorithm
, 0, "LRU page mgmt");
155 SYSCTL_INT(_vm
, OID_AUTO
, max_launder
,
156 CTLFLAG_RW
, &vm_max_launder
, 0, "Limit dirty flushes in pageout");
158 SYSCTL_INT(_vm
, OID_AUTO
, pageout_stats_max
,
159 CTLFLAG_RW
, &vm_pageout_stats_max
, 0, "Max pageout stats scan length");
161 SYSCTL_INT(_vm
, OID_AUTO
, pageout_full_stats_interval
,
162 CTLFLAG_RW
, &vm_pageout_full_stats_interval
, 0, "Interval for full stats scan");
164 SYSCTL_INT(_vm
, OID_AUTO
, pageout_stats_interval
,
165 CTLFLAG_RW
, &vm_pageout_stats_interval
, 0, "Interval for partial stats scan");
167 SYSCTL_INT(_vm
, OID_AUTO
, pageout_stats_free_max
,
168 CTLFLAG_RW
, &vm_pageout_stats_free_max
, 0, "Not implemented");
170 #if defined(NO_SWAPPING)
171 SYSCTL_INT(_vm
, VM_SWAPPING_ENABLED
, swap_enabled
,
172 CTLFLAG_RD
, &vm_swap_enabled
, 0, "");
173 SYSCTL_INT(_vm
, OID_AUTO
, swap_idle_enabled
,
174 CTLFLAG_RD
, &vm_swap_idle_enabled
, 0, "");
176 SYSCTL_INT(_vm
, VM_SWAPPING_ENABLED
, swap_enabled
,
177 CTLFLAG_RW
, &vm_swap_enabled
, 0, "Enable entire process swapout");
178 SYSCTL_INT(_vm
, OID_AUTO
, swap_idle_enabled
,
179 CTLFLAG_RW
, &vm_swap_idle_enabled
, 0, "Allow swapout on idle criteria");
182 SYSCTL_INT(_vm
, OID_AUTO
, defer_swapspace_pageouts
,
183 CTLFLAG_RW
, &defer_swap_pageouts
, 0, "Give preference to dirty pages in mem");
185 SYSCTL_INT(_vm
, OID_AUTO
, disable_swapspace_pageouts
,
186 CTLFLAG_RW
, &disable_swap_pageouts
, 0, "Disallow swapout of dirty pages");
188 static int pageout_lock_miss
;
189 SYSCTL_INT(_vm
, OID_AUTO
, pageout_lock_miss
,
190 CTLFLAG_RD
, &pageout_lock_miss
, 0, "vget() lock misses during pageout");
193 SYSCTL_INT(_vm
, OID_AUTO
, vm_load
,
194 CTLFLAG_RD
, &vm_load
, 0, "load on the VM system");
195 int vm_load_enable
= 1;
196 SYSCTL_INT(_vm
, OID_AUTO
, vm_load_enable
,
197 CTLFLAG_RW
, &vm_load_enable
, 0, "enable vm_load rate limiting");
200 SYSCTL_INT(_vm
, OID_AUTO
, vm_load_debug
,
201 CTLFLAG_RW
, &vm_load_debug
, 0, "debug vm_load");
204 #define VM_PAGEOUT_PAGE_COUNT 16
205 int vm_pageout_page_count
= VM_PAGEOUT_PAGE_COUNT
;
207 int vm_page_max_wired
; /* XXX max # of wired pages system-wide */
209 #if !defined(NO_SWAPPING)
210 typedef void freeer_fcn_t (vm_map_t
, vm_object_t
, vm_pindex_t
, int);
211 static void vm_pageout_map_deactivate_pages (vm_map_t
, vm_pindex_t
);
212 static freeer_fcn_t vm_pageout_object_deactivate_pages
;
213 static void vm_req_vmdaemon (void);
215 static void vm_pageout_page_stats(void);
218 * Update vm_load to slow down faulting processes.
224 vm_fault_ratecheck(void)
226 if (vm_pages_needed
) {
238 * Clean the page and remove it from the laundry. The page must not be
241 * We set the busy bit to cause potential page faults on this page to
242 * block. Note the careful timing, however, the busy bit isn't set till
243 * late and we cannot do anything that will mess with the page.
245 * The caller must hold vm_token.
248 vm_pageout_clean(vm_page_t m
)
251 vm_page_t mc
[2*vm_pageout_page_count
];
253 int ib
, is
, page_base
;
254 vm_pindex_t pindex
= m
->pindex
;
259 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
260 * with the new swapper, but we could have serious problems paging
261 * out other object types if there is insufficient memory.
263 * Unfortunately, checking free memory here is far too late, so the
264 * check has been moved up a procedural level.
268 * Don't mess with the page if it's busy, held, or special
270 if ((m
->hold_count
!= 0) ||
271 ((m
->busy
!= 0) || (m
->flags
& (PG_BUSY
|PG_UNMANAGED
)))) {
275 mc
[vm_pageout_page_count
] = m
;
277 page_base
= vm_pageout_page_count
;
282 * Scan object for clusterable pages.
284 * We can cluster ONLY if: ->> the page is NOT
285 * clean, wired, busy, held, or mapped into a
286 * buffer, and one of the following:
287 * 1) The page is inactive, or a seldom used
290 * 2) we force the issue.
292 * During heavy mmap/modification loads the pageout
293 * daemon can really fragment the underlying file
294 * due to flushing pages out of order and not trying
295 * align the clusters (which leave sporatic out-of-order
296 * holes). To solve this problem we do the reverse scan
297 * first and attempt to align our cluster, then do a
298 * forward scan if room remains.
302 while (ib
&& pageout_count
< vm_pageout_page_count
) {
310 if ((p
= vm_page_lookup(object
, pindex
- ib
)) == NULL
) {
314 if (((p
->queue
- p
->pc
) == PQ_CACHE
) ||
315 (p
->flags
& (PG_BUSY
|PG_UNMANAGED
)) || p
->busy
) {
319 vm_page_test_dirty(p
);
320 if ((p
->dirty
& p
->valid
) == 0 ||
321 p
->queue
!= PQ_INACTIVE
||
322 p
->wire_count
!= 0 || /* may be held by buf cache */
323 p
->hold_count
!= 0) { /* may be undergoing I/O */
331 * alignment boundry, stop here and switch directions. Do
334 if ((pindex
- (ib
- 1)) % vm_pageout_page_count
== 0)
338 while (pageout_count
< vm_pageout_page_count
&&
339 pindex
+ is
< object
->size
) {
342 if ((p
= vm_page_lookup(object
, pindex
+ is
)) == NULL
)
344 if (((p
->queue
- p
->pc
) == PQ_CACHE
) ||
345 (p
->flags
& (PG_BUSY
|PG_UNMANAGED
)) || p
->busy
) {
348 vm_page_test_dirty(p
);
349 if ((p
->dirty
& p
->valid
) == 0 ||
350 p
->queue
!= PQ_INACTIVE
||
351 p
->wire_count
!= 0 || /* may be held by buf cache */
352 p
->hold_count
!= 0) { /* may be undergoing I/O */
355 mc
[page_base
+ pageout_count
] = p
;
361 * If we exhausted our forward scan, continue with the reverse scan
362 * when possible, even past a page boundry. This catches boundry
365 if (ib
&& pageout_count
< vm_pageout_page_count
)
369 * we allow reads during pageouts...
371 return vm_pageout_flush(&mc
[page_base
], pageout_count
, 0);
375 * vm_pageout_flush() - launder the given pages
377 * The given pages are laundered. Note that we setup for the start of
378 * I/O ( i.e. busy the page ), mark it read-only, and bump the object
379 * reference count all in here rather then in the parent. If we want
380 * the parent to do more sophisticated things we may have to change
383 * The caller must hold vm_token.
386 vm_pageout_flush(vm_page_t
*mc
, int count
, int flags
)
389 int pageout_status
[count
];
393 ASSERT_LWKT_TOKEN_HELD(&vm_token
);
396 * Initiate I/O. Bump the vm_page_t->busy counter.
398 for (i
= 0; i
< count
; i
++) {
399 KASSERT(mc
[i
]->valid
== VM_PAGE_BITS_ALL
, ("vm_pageout_flush page %p index %d/%d: partially invalid page", mc
[i
], i
, count
));
400 vm_page_io_start(mc
[i
]);
404 * We must make the pages read-only. This will also force the
405 * modified bit in the related pmaps to be cleared. The pager
406 * cannot clear the bit for us since the I/O completion code
407 * typically runs from an interrupt. The act of making the page
408 * read-only handles the case for us.
410 for (i
= 0; i
< count
; i
++) {
411 vm_page_protect(mc
[i
], VM_PROT_READ
);
414 object
= mc
[0]->object
;
415 vm_object_pip_add(object
, count
);
417 vm_pager_put_pages(object
, mc
, count
,
418 (flags
| ((object
== &kernel_object
) ? VM_PAGER_PUT_SYNC
: 0)),
421 for (i
= 0; i
< count
; i
++) {
422 vm_page_t mt
= mc
[i
];
424 switch (pageout_status
[i
]) {
433 * Page outside of range of object. Right now we
434 * essentially lose the changes by pretending it
437 pmap_clear_modify(mt
);
443 * A page typically cannot be paged out when we
444 * have run out of swap. We leave the page
445 * marked inactive and will try to page it out
448 * Starvation of the active page list is used to
449 * determine when the system is massively memory
458 * If the operation is still going, leave the page busy to
459 * block all other accesses. Also, leave the paging in
460 * progress indicator set so that we don't attempt an object
463 * For any pages which have completed synchronously,
464 * deactivate the page if we are under a severe deficit.
465 * Do not try to enter them into the cache, though, they
466 * might still be read-heavy.
468 if (pageout_status
[i
] != VM_PAGER_PEND
) {
469 vm_object_pip_wakeup(object
);
470 vm_page_io_finish(mt
);
471 if (vm_page_count_severe())
472 vm_page_deactivate(mt
);
474 if (!vm_page_count_severe() || !vm_page_try_to_cache(mt
))
475 vm_page_protect(mt
, VM_PROT_READ
);
482 #if !defined(NO_SWAPPING)
484 * vm_pageout_object_deactivate_pages
486 * deactivate enough pages to satisfy the inactive target
487 * requirements or if vm_page_proc_limit is set, then
488 * deactivate all of the pages in the object and its
491 * The map must be locked.
492 * The caller must hold vm_token.
494 static int vm_pageout_object_deactivate_pages_callback(vm_page_t
, void *);
497 vm_pageout_object_deactivate_pages(vm_map_t map
, vm_object_t object
,
498 vm_pindex_t desired
, int map_remove_only
)
500 struct rb_vm_page_scan_info info
;
503 if (object
->type
== OBJT_DEVICE
|| object
->type
== OBJT_PHYS
)
507 if (pmap_resident_count(vm_map_pmap(map
)) <= desired
)
509 if (object
->paging_in_progress
)
512 remove_mode
= map_remove_only
;
513 if (object
->shadow_count
> 1)
517 * scan the objects entire memory queue. spl protection is
518 * required to avoid an interrupt unbusy/free race against
522 info
.limit
= remove_mode
;
524 info
.desired
= desired
;
525 vm_page_rb_tree_RB_SCAN(&object
->rb_memq
, NULL
,
526 vm_pageout_object_deactivate_pages_callback
,
530 object
= object
->backing_object
;
535 * The caller must hold vm_token.
538 vm_pageout_object_deactivate_pages_callback(vm_page_t p
, void *data
)
540 struct rb_vm_page_scan_info
*info
= data
;
543 if (pmap_resident_count(vm_map_pmap(info
->map
)) <= info
->desired
) {
546 mycpu
->gd_cnt
.v_pdpages
++;
547 if (p
->wire_count
!= 0 || p
->hold_count
!= 0 || p
->busy
!= 0 ||
548 (p
->flags
& (PG_BUSY
|PG_UNMANAGED
)) ||
549 !pmap_page_exists_quick(vm_map_pmap(info
->map
), p
)) {
553 actcount
= pmap_ts_referenced(p
);
555 vm_page_flag_set(p
, PG_REFERENCED
);
556 } else if (p
->flags
& PG_REFERENCED
) {
560 if ((p
->queue
!= PQ_ACTIVE
) &&
561 (p
->flags
& PG_REFERENCED
)) {
563 p
->act_count
+= actcount
;
564 vm_page_flag_clear(p
, PG_REFERENCED
);
565 } else if (p
->queue
== PQ_ACTIVE
) {
566 if ((p
->flags
& PG_REFERENCED
) == 0) {
567 p
->act_count
-= min(p
->act_count
, ACT_DECLINE
);
568 if (!info
->limit
&& (vm_pageout_algorithm
|| (p
->act_count
== 0))) {
570 vm_page_protect(p
, VM_PROT_NONE
);
572 vm_page_deactivate(p
);
574 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, p
, pageq
);
575 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, p
, pageq
);
579 vm_page_flag_clear(p
, PG_REFERENCED
);
580 if (p
->act_count
< (ACT_MAX
- ACT_ADVANCE
))
581 p
->act_count
+= ACT_ADVANCE
;
582 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, p
, pageq
);
583 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, p
, pageq
);
585 } else if (p
->queue
== PQ_INACTIVE
) {
587 vm_page_protect(p
, VM_PROT_NONE
);
594 * Deactivate some number of pages in a map, try to do it fairly, but
595 * that is really hard to do.
597 * The caller must hold vm_token.
600 vm_pageout_map_deactivate_pages(vm_map_t map
, vm_pindex_t desired
)
603 vm_object_t obj
, bigobj
;
606 if (lockmgr(&map
->lock
, LK_EXCLUSIVE
| LK_NOWAIT
)) {
614 * first, search out the biggest object, and try to free pages from
617 tmpe
= map
->header
.next
;
618 while (tmpe
!= &map
->header
) {
619 switch(tmpe
->maptype
) {
620 case VM_MAPTYPE_NORMAL
:
621 case VM_MAPTYPE_VPAGETABLE
:
622 obj
= tmpe
->object
.vm_object
;
623 if ((obj
!= NULL
) && (obj
->shadow_count
<= 1) &&
625 (bigobj
->resident_page_count
< obj
->resident_page_count
))) {
632 if (tmpe
->wired_count
> 0)
633 nothingwired
= FALSE
;
638 vm_pageout_object_deactivate_pages(map
, bigobj
, desired
, 0);
641 * Next, hunt around for other pages to deactivate. We actually
642 * do this search sort of wrong -- .text first is not the best idea.
644 tmpe
= map
->header
.next
;
645 while (tmpe
!= &map
->header
) {
646 if (pmap_resident_count(vm_map_pmap(map
)) <= desired
)
648 switch(tmpe
->maptype
) {
649 case VM_MAPTYPE_NORMAL
:
650 case VM_MAPTYPE_VPAGETABLE
:
651 obj
= tmpe
->object
.vm_object
;
653 vm_pageout_object_deactivate_pages(map
, obj
, desired
, 0);
662 * Remove all mappings if a process is swapped out, this will free page
665 if (desired
== 0 && nothingwired
)
666 pmap_remove(vm_map_pmap(map
),
667 VM_MIN_USER_ADDRESS
, VM_MAX_USER_ADDRESS
);
673 * Don't try to be fancy - being fancy can lead to vnode deadlocks. We
674 * only do it for OBJT_DEFAULT and OBJT_SWAP objects which we know can
675 * be trivially freed.
677 * The caller must hold vm_token.
680 vm_pageout_page_free(vm_page_t m
)
682 vm_object_t object
= m
->object
;
683 int type
= object
->type
;
685 if (type
== OBJT_SWAP
|| type
== OBJT_DEFAULT
)
686 vm_object_reference(object
);
688 vm_page_protect(m
, VM_PROT_NONE
);
690 if (type
== OBJT_SWAP
|| type
== OBJT_DEFAULT
)
691 vm_object_deallocate(object
);
695 * vm_pageout_scan does the dirty work for the pageout daemon.
697 struct vm_pageout_scan_info
{
698 struct proc
*bigproc
;
702 static int vm_pageout_scan_callback(struct proc
*p
, void *data
);
705 * The caller must hold vm_token.
708 vm_pageout_scan(int pass
)
710 struct vm_pageout_scan_info info
;
712 struct vm_page marker
;
713 struct vnode
*vpfailed
; /* warning, allowed to be stale */
716 int inactive_shortage
, active_shortage
;
717 int inactive_original_shortage
;
720 int vnodes_skipped
= 0;
724 * Do whatever cleanup that the pmap code can.
729 * Calculate our target for the number of free+cache pages we
730 * want to get to. This is higher then the number that causes
731 * allocations to stall (severe) in order to provide hysteresis,
732 * and if we don't make it all the way but get to the minimum
735 inactive_shortage
= vm_paging_target() + vm_pageout_deficit
;
736 inactive_original_shortage
= inactive_shortage
;
737 vm_pageout_deficit
= 0;
740 * Initialize our marker
742 bzero(&marker
, sizeof(marker
));
743 marker
.flags
= PG_BUSY
| PG_FICTITIOUS
| PG_MARKER
;
744 marker
.queue
= PQ_INACTIVE
;
745 marker
.wire_count
= 1;
748 * Start scanning the inactive queue for pages we can move to the
749 * cache or free. The scan will stop when the target is reached or
750 * we have scanned the entire inactive queue. Note that m->act_count
751 * is not used to form decisions for the inactive queue, only for the
754 * maxlaunder limits the number of dirty pages we flush per scan.
755 * For most systems a smaller value (16 or 32) is more robust under
756 * extreme memory and disk pressure because any unnecessary writes
757 * to disk can result in extreme performance degredation. However,
758 * systems with excessive dirty pages (especially when MAP_NOSYNC is
759 * used) will die horribly with limited laundering. If the pageout
760 * daemon cannot clean enough pages in the first pass, we let it go
761 * all out in succeeding passes.
763 if ((maxlaunder
= vm_max_launder
) <= 1)
769 * We will generally be in a critical section throughout the
770 * scan, but we can release it temporarily when we are sitting on a
771 * non-busy page without fear. this is required to prevent an
772 * interrupt from unbusying or freeing a page prior to our busy
773 * check, leaving us on the wrong queue or checking the wrong
779 maxscan
= vmstats
.v_inactive_count
;
780 for (m
= TAILQ_FIRST(&vm_page_queues
[PQ_INACTIVE
].pl
);
781 m
!= NULL
&& maxscan
-- > 0 && inactive_shortage
> 0;
784 mycpu
->gd_cnt
.v_pdpages
++;
787 * Give interrupts a chance
793 * It's easier for some of the conditions below to just loop
794 * and catch queue changes here rather then check everywhere
797 if (m
->queue
!= PQ_INACTIVE
)
799 next
= TAILQ_NEXT(m
, pageq
);
804 if (m
->flags
& PG_MARKER
)
808 * A held page may be undergoing I/O, so skip it.
811 TAILQ_REMOVE(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
812 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
813 ++vm_swapcache_inactive_heuristic
;
818 * Dont mess with busy pages, keep in the front of the
819 * queue, most likely are being paged out.
821 if (m
->busy
|| (m
->flags
& PG_BUSY
)) {
825 if (m
->object
->ref_count
== 0) {
827 * If the object is not being used, we ignore previous
830 vm_page_flag_clear(m
, PG_REFERENCED
);
831 pmap_clear_reference(m
);
833 } else if (((m
->flags
& PG_REFERENCED
) == 0) &&
834 (actcount
= pmap_ts_referenced(m
))) {
836 * Otherwise, if the page has been referenced while
837 * in the inactive queue, we bump the "activation
838 * count" upwards, making it less likely that the
839 * page will be added back to the inactive queue
840 * prematurely again. Here we check the page tables
841 * (or emulated bits, if any), given the upper level
842 * VM system not knowing anything about existing
846 m
->act_count
+= (actcount
+ ACT_ADVANCE
);
851 * If the upper level VM system knows about any page
852 * references, we activate the page. We also set the
853 * "activation count" higher than normal so that we will less
854 * likely place pages back onto the inactive queue again.
856 if ((m
->flags
& PG_REFERENCED
) != 0) {
857 vm_page_flag_clear(m
, PG_REFERENCED
);
858 actcount
= pmap_ts_referenced(m
);
860 m
->act_count
+= (actcount
+ ACT_ADVANCE
+ 1);
865 * If the upper level VM system doesn't know anything about
866 * the page being dirty, we have to check for it again. As
867 * far as the VM code knows, any partially dirty pages are
870 * Pages marked PG_WRITEABLE may be mapped into the user
871 * address space of a process running on another cpu. A
872 * user process (without holding the MP lock) running on
873 * another cpu may be able to touch the page while we are
874 * trying to remove it. vm_page_cache() will handle this
878 vm_page_test_dirty(m
);
885 * Invalid pages can be easily freed
887 vm_pageout_page_free(m
);
888 mycpu
->gd_cnt
.v_dfree
++;
890 } else if (m
->dirty
== 0) {
892 * Clean pages can be placed onto the cache queue.
893 * This effectively frees them.
897 } else if ((m
->flags
& PG_WINATCFLS
) == 0 && pass
== 0) {
899 * Dirty pages need to be paged out, but flushing
900 * a page is extremely expensive verses freeing
901 * a clean page. Rather then artificially limiting
902 * the number of pages we can flush, we instead give
903 * dirty pages extra priority on the inactive queue
904 * by forcing them to be cycled through the queue
905 * twice before being flushed, after which the
906 * (now clean) page will cycle through once more
907 * before being freed. This significantly extends
908 * the thrash point for a heavily loaded machine.
910 vm_page_flag_set(m
, PG_WINATCFLS
);
911 TAILQ_REMOVE(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
912 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
913 ++vm_swapcache_inactive_heuristic
;
914 } else if (maxlaunder
> 0) {
916 * We always want to try to flush some dirty pages if
917 * we encounter them, to keep the system stable.
918 * Normally this number is small, but under extreme
919 * pressure where there are insufficient clean pages
920 * on the inactive queue, we may have to go all out.
922 int swap_pageouts_ok
;
923 struct vnode
*vp
= NULL
;
927 if ((object
->type
!= OBJT_SWAP
) && (object
->type
!= OBJT_DEFAULT
)) {
928 swap_pageouts_ok
= 1;
930 swap_pageouts_ok
= !(defer_swap_pageouts
|| disable_swap_pageouts
);
931 swap_pageouts_ok
|= (!disable_swap_pageouts
&& defer_swap_pageouts
&&
932 vm_page_count_min(0));
937 * We don't bother paging objects that are "dead".
938 * Those objects are in a "rundown" state.
940 if (!swap_pageouts_ok
|| (object
->flags
& OBJ_DEAD
)) {
941 TAILQ_REMOVE(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
942 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
943 ++vm_swapcache_inactive_heuristic
;
948 * The object is already known NOT to be dead. It
949 * is possible for the vget() to block the whole
950 * pageout daemon, but the new low-memory handling
951 * code should prevent it.
953 * The previous code skipped locked vnodes and, worse,
954 * reordered pages in the queue. This results in
955 * completely non-deterministic operation because,
956 * quite often, a vm_fault has initiated an I/O and
957 * is holding a locked vnode at just the point where
958 * the pageout daemon is woken up.
960 * We can't wait forever for the vnode lock, we might
961 * deadlock due to a vn_read() getting stuck in
962 * vm_wait while holding this vnode. We skip the
963 * vnode if we can't get it in a reasonable amount
966 * vpfailed is used to (try to) avoid the case where
967 * a large number of pages are associated with a
968 * locked vnode, which could cause the pageout daemon
969 * to stall for an excessive amount of time.
971 if (object
->type
== OBJT_VNODE
) {
975 flags
= LK_EXCLUSIVE
| LK_NOOBJ
;
979 flags
|= LK_TIMELOCK
;
980 if (vget(vp
, flags
) != 0) {
983 if (object
->flags
& OBJ_MIGHTBEDIRTY
)
989 * The page might have been moved to another
990 * queue during potential blocking in vget()
991 * above. The page might have been freed and
992 * reused for another vnode. The object might
993 * have been reused for another vnode.
995 if (m
->queue
!= PQ_INACTIVE
||
996 m
->object
!= object
||
997 object
->handle
!= vp
) {
998 if (object
->flags
& OBJ_MIGHTBEDIRTY
)
1005 * The page may have been busied during the
1006 * blocking in vput(); We don't move the
1007 * page back onto the end of the queue so that
1008 * statistics are more correct if we don't.
1010 if (m
->busy
|| (m
->flags
& PG_BUSY
)) {
1016 * If the page has become held it might
1017 * be undergoing I/O, so skip it
1019 if (m
->hold_count
) {
1020 TAILQ_REMOVE(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
1021 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
1022 ++vm_swapcache_inactive_heuristic
;
1023 if (object
->flags
& OBJ_MIGHTBEDIRTY
)
1031 * If a page is dirty, then it is either being washed
1032 * (but not yet cleaned) or it is still in the
1033 * laundry. If it is still in the laundry, then we
1034 * start the cleaning operation.
1036 * This operation may cluster, invalidating the 'next'
1037 * pointer. To prevent an inordinate number of
1038 * restarts we use our marker to remember our place.
1040 * decrement inactive_shortage on success to account
1041 * for the (future) cleaned page. Otherwise we
1042 * could wind up laundering or cleaning too many
1045 TAILQ_INSERT_AFTER(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, &marker
, pageq
);
1046 if (vm_pageout_clean(m
) != 0) {
1047 --inactive_shortage
;
1050 next
= TAILQ_NEXT(&marker
, pageq
);
1051 TAILQ_REMOVE(&vm_page_queues
[PQ_INACTIVE
].pl
, &marker
, pageq
);
1058 * We want to move pages from the active queue to the inactive
1059 * queue to get the inactive queue to the inactive target. If
1060 * we still have a page shortage from above we try to directly free
1061 * clean pages instead of moving them.
1063 * If we do still have a shortage we keep track of the number of
1064 * pages we free or cache (recycle_count) as a measure of thrashing
1065 * between the active and inactive queues.
1067 * If we were able to completely satisfy the free+cache targets
1068 * from the inactive pool we limit the number of pages we move
1069 * from the active pool to the inactive pool to 2x the pages we
1070 * had removed from the inactive pool (with a minimum of 1/5 the
1071 * inactive target). If we were not able to completely satisfy
1072 * the free+cache targets we go for the whole target aggressively.
1074 * NOTE: Both variables can end up negative.
1075 * NOTE: We are still in a critical section.
1077 active_shortage
= vmstats
.v_inactive_target
- vmstats
.v_inactive_count
;
1078 if (inactive_original_shortage
< vmstats
.v_inactive_target
/ 10)
1079 inactive_original_shortage
= vmstats
.v_inactive_target
/ 10;
1080 if (inactive_shortage
<= 0 &&
1081 active_shortage
> inactive_original_shortage
* 2) {
1082 active_shortage
= inactive_original_shortage
* 2;
1085 pcount
= vmstats
.v_active_count
;
1087 m
= TAILQ_FIRST(&vm_page_queues
[PQ_ACTIVE
].pl
);
1089 while ((m
!= NULL
) && (pcount
-- > 0) &&
1090 (inactive_shortage
> 0 || active_shortage
> 0)
1093 * Give interrupts a chance.
1099 * If the page was ripped out from under us, just stop.
1101 if (m
->queue
!= PQ_ACTIVE
)
1103 next
= TAILQ_NEXT(m
, pageq
);
1106 * Don't deactivate pages that are busy.
1108 if ((m
->busy
!= 0) ||
1109 (m
->flags
& PG_BUSY
) ||
1110 (m
->hold_count
!= 0)) {
1111 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1112 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1118 * The count for pagedaemon pages is done after checking the
1119 * page for eligibility...
1121 mycpu
->gd_cnt
.v_pdpages
++;
1124 * Check to see "how much" the page has been used and clear
1125 * the tracking access bits. If the object has no references
1126 * don't bother paying the expense.
1129 if (m
->object
->ref_count
!= 0) {
1130 if (m
->flags
& PG_REFERENCED
)
1132 actcount
+= pmap_ts_referenced(m
);
1134 m
->act_count
+= ACT_ADVANCE
+ actcount
;
1135 if (m
->act_count
> ACT_MAX
)
1136 m
->act_count
= ACT_MAX
;
1139 vm_page_flag_clear(m
, PG_REFERENCED
);
1142 * actcount is only valid if the object ref_count is non-zero.
1144 if (actcount
&& m
->object
->ref_count
!= 0) {
1145 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1146 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1148 m
->act_count
-= min(m
->act_count
, ACT_DECLINE
);
1149 if (vm_pageout_algorithm
||
1150 m
->object
->ref_count
== 0 ||
1151 m
->act_count
< pass
+ 1
1154 * Deactivate the page. If we had a
1155 * shortage from our inactive scan try to
1156 * free (cache) the page instead.
1158 * Don't just blindly cache the page if
1159 * we do not have a shortage from the
1160 * inactive scan, that could lead to
1161 * gigabytes being moved.
1164 if (inactive_shortage
> 0 ||
1165 m
->object
->ref_count
== 0) {
1166 if (inactive_shortage
> 0)
1169 vm_page_protect(m
, VM_PROT_NONE
);
1171 if (m
->dirty
== 0 &&
1172 inactive_shortage
> 0) {
1173 --inactive_shortage
;
1176 vm_page_deactivate(m
);
1179 vm_page_deactivate(m
);
1182 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1183 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1190 * We try to maintain some *really* free pages, this allows interrupt
1191 * code to be guaranteed space. Since both cache and free queues
1192 * are considered basically 'free', moving pages from cache to free
1193 * does not effect other calculations.
1195 * NOTE: we are still in a critical section.
1197 * Pages moved from PQ_CACHE to totally free are not counted in the
1198 * pages_freed counter.
1200 while (vmstats
.v_free_count
< vmstats
.v_free_reserved
) {
1201 static int cache_rover
= 0;
1202 m
= vm_page_list_find(PQ_CACHE
, cache_rover
, FALSE
);
1205 if ((m
->flags
& (PG_BUSY
|PG_UNMANAGED
)) ||
1210 kprintf("Warning: busy page %p found in cache\n", m
);
1212 vm_page_deactivate(m
);
1215 KKASSERT((m
->flags
& PG_MAPPED
) == 0);
1216 KKASSERT(m
->dirty
== 0);
1217 cache_rover
= (cache_rover
+ PQ_PRIME2
) & PQ_L2_MASK
;
1218 vm_pageout_page_free(m
);
1219 mycpu
->gd_cnt
.v_dfree
++;
1224 #if !defined(NO_SWAPPING)
1226 * Idle process swapout -- run once per second.
1228 if (vm_swap_idle_enabled
) {
1230 if (time_second
!= lsec
) {
1231 vm_pageout_req_swapout
|= VM_SWAP_IDLE
;
1239 * If we didn't get enough free pages, and we have skipped a vnode
1240 * in a writeable object, wakeup the sync daemon. And kick swapout
1241 * if we did not get enough free pages.
1243 if (vm_paging_target() > 0) {
1244 if (vnodes_skipped
&& vm_page_count_min(0))
1246 #if !defined(NO_SWAPPING)
1247 if (vm_swap_enabled
&& vm_page_count_target()) {
1249 vm_pageout_req_swapout
|= VM_SWAP_NORMAL
;
1255 * Handle catastrophic conditions. Under good conditions we should
1256 * be at the target, well beyond our minimum. If we could not even
1257 * reach our minimum the system is under heavy stress.
1259 * Determine whether we have run out of memory. This occurs when
1260 * swap_pager_full is TRUE and the only pages left in the page
1261 * queues are dirty. We will still likely have page shortages.
1263 * - swap_pager_full is set if insufficient swap was
1264 * available to satisfy a requested pageout.
1266 * - the inactive queue is bloated (4 x size of active queue),
1267 * meaning it is unable to get rid of dirty pages and.
1269 * - vm_page_count_min() without counting pages recycled from the
1270 * active queue (recycle_count) means we could not recover
1271 * enough pages to meet bare minimum needs. This test only
1272 * works if the inactive queue is bloated.
1274 * - due to a positive inactive_shortage we shifted the remaining
1275 * dirty pages from the active queue to the inactive queue
1276 * trying to find clean ones to free.
1278 if (swap_pager_full
&& vm_page_count_min(recycle_count
))
1279 kprintf("Warning: system low on memory+swap!\n");
1280 if (swap_pager_full
&& vm_page_count_min(recycle_count
) &&
1281 vmstats
.v_inactive_count
> vmstats
.v_active_count
* 4 &&
1282 inactive_shortage
> 0) {
1286 info
.bigproc
= NULL
;
1288 allproc_scan(vm_pageout_scan_callback
, &info
);
1289 if (info
.bigproc
!= NULL
) {
1290 killproc(info
.bigproc
, "out of swap space");
1291 info
.bigproc
->p_nice
= PRIO_MIN
;
1292 info
.bigproc
->p_usched
->resetpriority(
1293 FIRST_LWP_IN_PROC(info
.bigproc
));
1294 wakeup(&vmstats
.v_free_count
);
1295 PRELE(info
.bigproc
);
1298 return(inactive_shortage
);
1302 * The caller must hold vm_token and proc_token.
1305 vm_pageout_scan_callback(struct proc
*p
, void *data
)
1307 struct vm_pageout_scan_info
*info
= data
;
1311 * Never kill system processes or init. If we have configured swap
1312 * then try to avoid killing low-numbered pids.
1314 if ((p
->p_flag
& P_SYSTEM
) || (p
->p_pid
== 1) ||
1315 ((p
->p_pid
< 48) && (vm_swap_size
!= 0))) {
1320 * if the process is in a non-running type state,
1323 if (p
->p_stat
!= SACTIVE
&& p
->p_stat
!= SSTOP
)
1327 * Get the approximate process size. Note that anonymous pages
1328 * with backing swap will be counted twice, but there should not
1329 * be too many such pages due to the stress the VM system is
1330 * under at this point.
1332 size
= vmspace_anonymous_count(p
->p_vmspace
) +
1333 vmspace_swap_count(p
->p_vmspace
);
1336 * If the this process is bigger than the biggest one
1339 if (info
->bigsize
< size
) {
1341 PRELE(info
->bigproc
);
1344 info
->bigsize
= size
;
1350 * This routine tries to maintain the pseudo LRU active queue,
1351 * so that during long periods of time where there is no paging,
1352 * that some statistic accumulation still occurs. This code
1353 * helps the situation where paging just starts to occur.
1355 * The caller must hold vm_token.
1358 vm_pageout_page_stats(void)
1361 int pcount
,tpcount
; /* Number of pages to check */
1362 static int fullintervalcount
= 0;
1366 (vmstats
.v_inactive_target
+ vmstats
.v_cache_max
+ vmstats
.v_free_min
) -
1367 (vmstats
.v_free_count
+ vmstats
.v_inactive_count
+ vmstats
.v_cache_count
);
1369 if (page_shortage
<= 0)
1374 pcount
= vmstats
.v_active_count
;
1375 fullintervalcount
+= vm_pageout_stats_interval
;
1376 if (fullintervalcount
< vm_pageout_full_stats_interval
) {
1377 tpcount
= (vm_pageout_stats_max
* vmstats
.v_active_count
) / vmstats
.v_page_count
;
1378 if (pcount
> tpcount
)
1381 fullintervalcount
= 0;
1384 m
= TAILQ_FIRST(&vm_page_queues
[PQ_ACTIVE
].pl
);
1385 while ((m
!= NULL
) && (pcount
-- > 0)) {
1388 if (m
->queue
!= PQ_ACTIVE
) {
1392 next
= TAILQ_NEXT(m
, pageq
);
1394 * Don't deactivate pages that are busy.
1396 if ((m
->busy
!= 0) ||
1397 (m
->flags
& PG_BUSY
) ||
1398 (m
->hold_count
!= 0)) {
1399 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1400 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1406 if (m
->flags
& PG_REFERENCED
) {
1407 vm_page_flag_clear(m
, PG_REFERENCED
);
1411 actcount
+= pmap_ts_referenced(m
);
1413 m
->act_count
+= ACT_ADVANCE
+ actcount
;
1414 if (m
->act_count
> ACT_MAX
)
1415 m
->act_count
= ACT_MAX
;
1416 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1417 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1419 if (m
->act_count
== 0) {
1421 * We turn off page access, so that we have
1422 * more accurate RSS stats. We don't do this
1423 * in the normal page deactivation when the
1424 * system is loaded VM wise, because the
1425 * cost of the large number of page protect
1426 * operations would be higher than the value
1427 * of doing the operation.
1430 vm_page_protect(m
, VM_PROT_NONE
);
1432 vm_page_deactivate(m
);
1434 m
->act_count
-= min(m
->act_count
, ACT_DECLINE
);
1435 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1436 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1446 * The caller must hold vm_token.
1449 vm_pageout_free_page_calc(vm_size_t count
)
1451 if (count
< vmstats
.v_page_count
)
1454 * free_reserved needs to include enough for the largest swap pager
1455 * structures plus enough for any pv_entry structs when paging.
1457 if (vmstats
.v_page_count
> 1024)
1458 vmstats
.v_free_min
= 4 + (vmstats
.v_page_count
- 1024) / 200;
1460 vmstats
.v_free_min
= 4;
1461 vmstats
.v_pageout_free_min
= (2*MAXBSIZE
)/PAGE_SIZE
+
1462 vmstats
.v_interrupt_free_min
;
1463 vmstats
.v_free_reserved
= vm_pageout_page_count
+
1464 vmstats
.v_pageout_free_min
+ (count
/ 768) + PQ_L2_SIZE
;
1465 vmstats
.v_free_severe
= vmstats
.v_free_min
/ 2;
1466 vmstats
.v_free_min
+= vmstats
.v_free_reserved
;
1467 vmstats
.v_free_severe
+= vmstats
.v_free_reserved
;
1473 * vm_pageout is the high level pageout daemon.
1478 vm_pageout_thread(void)
1481 int inactive_shortage
;
1484 * Permanently hold vm_token.
1486 lwkt_gettoken(&vm_token
);
1489 * Initialize some paging parameters.
1491 curthread
->td_flags
|= TDF_SYSTHREAD
;
1493 vmstats
.v_interrupt_free_min
= 2;
1494 if (vmstats
.v_page_count
< 2000)
1495 vm_pageout_page_count
= 8;
1497 vm_pageout_free_page_calc(vmstats
.v_page_count
);
1500 * v_free_target and v_cache_min control pageout hysteresis. Note
1501 * that these are more a measure of the VM cache queue hysteresis
1502 * then the VM free queue. Specifically, v_free_target is the
1503 * high water mark (free+cache pages).
1505 * v_free_reserved + v_cache_min (mostly means v_cache_min) is the
1506 * low water mark, while v_free_min is the stop. v_cache_min must
1507 * be big enough to handle memory needs while the pageout daemon
1508 * is signalled and run to free more pages.
1510 if (vmstats
.v_free_count
> 6144)
1511 vmstats
.v_free_target
= 4 * vmstats
.v_free_min
+ vmstats
.v_free_reserved
;
1513 vmstats
.v_free_target
= 2 * vmstats
.v_free_min
+ vmstats
.v_free_reserved
;
1516 * NOTE: With the new buffer cache b_act_count we want the default
1517 * inactive target to be a percentage of available memory.
1519 * The inactive target essentially determines the minimum
1520 * number of 'temporary' pages capable of caching one-time-use
1521 * files when the VM system is otherwise full of pages
1522 * belonging to multi-time-use files or active program data.
1524 * NOTE: The inactive target is aggressively persued only if the
1525 * inactive queue becomes too small. If the inactive queue
1526 * is large enough to satisfy page movement to free+cache
1527 * then it is repopulated more slowly from the active queue.
1528 * This allows a general inactive_target default to be set.
1530 * There is an issue here for processes which sit mostly idle
1531 * 'overnight', such as sshd, tcsh, and X. Any movement from
1532 * the active queue will eventually cause such pages to
1533 * recycle eventually causing a lot of paging in the morning.
1534 * To reduce the incidence of this pages cycled out of the
1535 * buffer cache are moved directly to the inactive queue if
1536 * they were only used once or twice.
1538 * The vfs.vm_cycle_point sysctl can be used to adjust this.
1539 * Increasing the value (up to 64) increases the number of
1540 * buffer recyclements which go directly to the inactive queue.
1542 if (vmstats
.v_free_count
> 2048) {
1543 vmstats
.v_cache_min
= vmstats
.v_free_target
;
1544 vmstats
.v_cache_max
= 2 * vmstats
.v_cache_min
;
1546 vmstats
.v_cache_min
= 0;
1547 vmstats
.v_cache_max
= 0;
1549 vmstats
.v_inactive_target
= vmstats
.v_free_count
/ 4;
1551 /* XXX does not really belong here */
1552 if (vm_page_max_wired
== 0)
1553 vm_page_max_wired
= vmstats
.v_free_count
/ 3;
1555 if (vm_pageout_stats_max
== 0)
1556 vm_pageout_stats_max
= vmstats
.v_free_target
;
1559 * Set interval in seconds for stats scan.
1561 if (vm_pageout_stats_interval
== 0)
1562 vm_pageout_stats_interval
= 5;
1563 if (vm_pageout_full_stats_interval
== 0)
1564 vm_pageout_full_stats_interval
= vm_pageout_stats_interval
* 4;
1568 * Set maximum free per pass
1570 if (vm_pageout_stats_free_max
== 0)
1571 vm_pageout_stats_free_max
= 5;
1573 swap_pager_swap_init();
1577 * The pageout daemon is never done, so loop forever.
1583 * Wait for an action request. If we timeout check to
1584 * see if paging is needed (in case the normal wakeup
1588 if (vm_pages_needed
== 0) {
1589 error
= tsleep(&vm_pages_needed
,
1591 vm_pageout_stats_interval
* hz
);
1593 vm_paging_needed() == 0 &&
1594 vm_pages_needed
== 0) {
1595 vm_pageout_page_stats();
1598 vm_pages_needed
= 1;
1603 * If we have enough free memory, wakeup waiters.
1604 * (This is optional here)
1607 if (!vm_page_count_min(0))
1608 wakeup(&vmstats
.v_free_count
);
1609 mycpu
->gd_cnt
.v_pdwakeups
++;
1613 * Scan for pageout. Try to avoid thrashing the system
1616 inactive_shortage
= vm_pageout_scan(pass
);
1617 if (inactive_shortage
> 0) {
1619 if (swap_pager_full
) {
1621 * Running out of memory, catastrophic back-off
1622 * to one-second intervals.
1624 tsleep(&vm_pages_needed
, 0, "pdelay", hz
);
1625 } else if (pass
< 10 && vm_pages_needed
> 1) {
1627 * Normal operation, additional processes
1628 * have already kicked us. Retry immediately.
1630 } else if (pass
< 10) {
1632 * Normal operation, fewer processes. Delay
1633 * a bit but allow wakeups.
1635 vm_pages_needed
= 0;
1636 tsleep(&vm_pages_needed
, 0, "pdelay", hz
/ 10);
1637 vm_pages_needed
= 1;
1640 * We've taken too many passes, forced delay.
1642 tsleep(&vm_pages_needed
, 0, "pdelay", hz
/ 10);
1646 * Interlocked wakeup of waiters (non-optional)
1649 if (vm_pages_needed
&& !vm_page_count_min(0)) {
1650 wakeup(&vmstats
.v_free_count
);
1651 vm_pages_needed
= 0;
1657 static struct kproc_desc page_kp
= {
1662 SYSINIT(pagedaemon
, SI_SUB_KTHREAD_PAGE
, SI_ORDER_FIRST
, kproc_start
, &page_kp
)
1666 * Called after allocating a page out of the cache or free queue
1667 * to possibly wake the pagedaemon up to replentish our supply.
1669 * We try to generate some hysteresis by waking the pagedaemon up
1670 * when our free+cache pages go below the free_min+cache_min level.
1671 * The pagedaemon tries to get the count back up to at least the
1672 * minimum, and through to the target level if possible.
1674 * If the pagedaemon is already active bump vm_pages_needed as a hint
1675 * that there are even more requests pending.
1681 pagedaemon_wakeup(void)
1683 if (vm_paging_needed() && curthread
!= pagethread
) {
1684 if (vm_pages_needed
== 0) {
1685 vm_pages_needed
= 1; /* SMP race ok */
1686 wakeup(&vm_pages_needed
);
1687 } else if (vm_page_count_min(0)) {
1688 ++vm_pages_needed
; /* SMP race ok */
1693 #if !defined(NO_SWAPPING)
1700 vm_req_vmdaemon(void)
1702 static int lastrun
= 0;
1704 if ((ticks
> (lastrun
+ hz
)) || (ticks
< lastrun
)) {
1705 wakeup(&vm_daemon_needed
);
1710 static int vm_daemon_callback(struct proc
*p
, void *data __unused
);
1719 * Permanently hold vm_token.
1721 lwkt_gettoken(&vm_token
);
1724 tsleep(&vm_daemon_needed
, 0, "psleep", 0);
1725 if (vm_pageout_req_swapout
) {
1726 swapout_procs(vm_pageout_req_swapout
);
1727 vm_pageout_req_swapout
= 0;
1730 * scan the processes for exceeding their rlimits or if
1731 * process is swapped out -- deactivate pages
1733 allproc_scan(vm_daemon_callback
, NULL
);
1738 * Caller must hold vm_token and proc_token.
1741 vm_daemon_callback(struct proc
*p
, void *data __unused
)
1743 vm_pindex_t limit
, size
;
1746 * if this is a system process or if we have already
1747 * looked at this process, skip it.
1749 if (p
->p_flag
& (P_SYSTEM
| P_WEXIT
))
1753 * if the process is in a non-running type state,
1756 if (p
->p_stat
!= SACTIVE
&& p
->p_stat
!= SSTOP
)
1762 limit
= OFF_TO_IDX(qmin(p
->p_rlimit
[RLIMIT_RSS
].rlim_cur
,
1763 p
->p_rlimit
[RLIMIT_RSS
].rlim_max
));
1766 * let processes that are swapped out really be
1767 * swapped out. Set the limit to nothing to get as
1768 * many pages out to swap as possible.
1770 if (p
->p_flag
& P_SWAPPEDOUT
)
1773 size
= vmspace_resident_count(p
->p_vmspace
);
1774 if (limit
>= 0 && size
>= limit
) {
1775 vm_pageout_map_deactivate_pages(
1776 &p
->p_vmspace
->vm_map
, limit
);