FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_pageout.c
1 /*-
2 * Copyright (c) 1991 Regents of the University of California.
3 * All rights reserved.
4 * Copyright (c) 1994 John S. Dyson
5 * All rights reserved.
6 * Copyright (c) 1994 David Greenman
7 * All rights reserved.
8 * Copyright (c) 2005 Yahoo! Technologies Norway AS
9 * All rights reserved.
10 *
11 * This code is derived from software contributed to Berkeley by
12 * The Mach Operating System project at Carnegie-Mellon University.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
16 * are met:
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.
29 *
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
40 * SUCH DAMAGE.
41 *
42 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
43 *
44 *
45 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
46 * All rights reserved.
47 *
48 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
49 *
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.
55 *
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.
59 *
60 * Carnegie Mellon requests users of this software to return to
61 *
62 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
63 * School of Computer Science
64 * Carnegie Mellon University
65 * Pittsburgh PA 15213-3890
66 *
67 * any improvements or extensions that they make and grant Carnegie the
68 * rights to redistribute these changes.
69 */
70
71 /*
72 * The proverbial page-out daemon.
73 */
74
75 #include <sys/cdefs.h>
76 __FBSDID("$FreeBSD$");
77
78 #include "opt_vm.h"
79 #include <sys/param.h>
80 #include <sys/systm.h>
81 #include <sys/kernel.h>
82 #include <sys/eventhandler.h>
83 #include <sys/lock.h>
84 #include <sys/mutex.h>
85 #include <sys/proc.h>
86 #include <sys/kthread.h>
87 #include <sys/ktr.h>
88 #include <sys/mount.h>
89 #include <sys/resourcevar.h>
90 #include <sys/sched.h>
91 #include <sys/signalvar.h>
92 #include <sys/vnode.h>
93 #include <sys/vmmeter.h>
94 #include <sys/sx.h>
95 #include <sys/sysctl.h>
96
97 #include <vm/vm.h>
98 #include <vm/vm_param.h>
99 #include <vm/vm_object.h>
100 #include <vm/vm_page.h>
101 #include <vm/vm_map.h>
102 #include <vm/vm_pageout.h>
103 #include <vm/vm_pager.h>
104 #include <vm/swap_pager.h>
105 #include <vm/vm_extern.h>
106 #include <vm/uma.h>
107
108 #include <machine/mutex.h>
109
110 /*
111 * System initialization
112 */
113
114 /* the kernel process "vm_pageout"*/
115 static void vm_pageout(void);
116 static int vm_pageout_clean(vm_page_t);
117 static void vm_pageout_scan(int pass);
118
119 struct proc *pageproc;
120
121 static struct kproc_desc page_kp = {
122 "pagedaemon",
123 vm_pageout,
124 &pageproc
125 };
126 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start,
127 &page_kp);
128
129 #if !defined(NO_SWAPPING)
130 /* the kernel process "vm_daemon"*/
131 static void vm_daemon(void);
132 static struct proc *vmproc;
133
134 static struct kproc_desc vm_kp = {
135 "vmdaemon",
136 vm_daemon,
137 &vmproc
138 };
139 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
140 #endif
141
142
143 int vm_pages_needed; /* Event on which pageout daemon sleeps */
144 int vm_pageout_deficit; /* Estimated number of pages deficit */
145 int vm_pageout_pages_needed; /* flag saying that the pageout daemon needs pages */
146
147 #if !defined(NO_SWAPPING)
148 static int vm_pageout_req_swapout; /* XXX */
149 static int vm_daemon_needed;
150 static struct mtx vm_daemon_mtx;
151 /* Allow for use by vm_pageout before vm_daemon is initialized. */
152 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
153 #endif
154 static int vm_max_launder = 32;
155 static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0;
156 static int vm_pageout_full_stats_interval = 0;
157 static int vm_pageout_algorithm=0;
158 static int defer_swap_pageouts=0;
159 static int disable_swap_pageouts=0;
160
161 #if defined(NO_SWAPPING)
162 static int vm_swap_enabled=0;
163 static int vm_swap_idle_enabled=0;
164 #else
165 static int vm_swap_enabled=1;
166 static int vm_swap_idle_enabled=0;
167 #endif
168
169 SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm,
170 CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt");
171
172 SYSCTL_INT(_vm, OID_AUTO, max_launder,
173 CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
174
175 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max,
176 CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length");
177
178 SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval,
179 CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan");
180
181 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval,
182 CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan");
183
184 #if defined(NO_SWAPPING)
185 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
186 CTLFLAG_RD, &vm_swap_enabled, 0, "");
187 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
188 CTLFLAG_RD, &vm_swap_idle_enabled, 0, "");
189 #else
190 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
191 CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
192 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
193 CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
194 #endif
195
196 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
197 CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
198
199 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
200 CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
201
202 static int pageout_lock_miss;
203 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
204 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
205
206 #define VM_PAGEOUT_PAGE_COUNT 16
207 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
208
209 int vm_page_max_wired; /* XXX max # of wired pages system-wide */
210 SYSCTL_INT(_vm, OID_AUTO, max_wired,
211 CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
212
213 #if !defined(NO_SWAPPING)
214 static void vm_pageout_map_deactivate_pages(vm_map_t, long);
215 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
216 static void vm_req_vmdaemon(int req);
217 #endif
218 static void vm_pageout_page_stats(void);
219
220 /*
221 * vm_pageout_fallback_object_lock:
222 *
223 * Lock vm object currently associated with `m'. VM_OBJECT_TRYLOCK is
224 * known to have failed and page queue must be either PQ_ACTIVE or
225 * PQ_INACTIVE. To avoid lock order violation, unlock the page queues
226 * while locking the vm object. Use marker page to detect page queue
227 * changes and maintain notion of next page on page queue. Return
228 * TRUE if no changes were detected, FALSE otherwise. vm object is
229 * locked on return.
230 *
231 * This function depends on both the lock portion of struct vm_object
232 * and normal struct vm_page being type stable.
233 */
234 boolean_t
235 vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
236 {
237 struct vm_page marker;
238 boolean_t unchanged;
239 u_short queue;
240 vm_object_t object;
241
242 /*
243 * Initialize our marker
244 */
245 bzero(&marker, sizeof(marker));
246 marker.flags = PG_FICTITIOUS | PG_MARKER;
247 marker.oflags = VPO_BUSY;
248 marker.queue = m->queue;
249 marker.wire_count = 1;
250
251 queue = m->queue;
252 object = m->object;
253
254 TAILQ_INSERT_AFTER(&vm_page_queues[queue].pl,
255 m, &marker, pageq);
256 vm_page_unlock_queues();
257 VM_OBJECT_LOCK(object);
258 vm_page_lock_queues();
259
260 /* Page queue might have changed. */
261 *next = TAILQ_NEXT(&marker, pageq);
262 unchanged = (m->queue == queue &&
263 m->object == object &&
264 &marker == TAILQ_NEXT(m, pageq));
265 TAILQ_REMOVE(&vm_page_queues[queue].pl,
266 &marker, pageq);
267 return (unchanged);
268 }
269
270 /*
271 * vm_pageout_clean:
272 *
273 * Clean the page and remove it from the laundry.
274 *
275 * We set the busy bit to cause potential page faults on this page to
276 * block. Note the careful timing, however, the busy bit isn't set till
277 * late and we cannot do anything that will mess with the page.
278 */
279 static int
280 vm_pageout_clean(m)
281 vm_page_t m;
282 {
283 vm_object_t object;
284 vm_page_t mc[2*vm_pageout_page_count], pb, ps;
285 int pageout_count;
286 int ib, is, page_base;
287 vm_pindex_t pindex = m->pindex;
288
289 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
290 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
291
292 /*
293 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
294 * with the new swapper, but we could have serious problems paging
295 * out other object types if there is insufficient memory.
296 *
297 * Unfortunately, checking free memory here is far too late, so the
298 * check has been moved up a procedural level.
299 */
300
301 /*
302 * Can't clean the page if it's busy or held.
303 */
304 if ((m->hold_count != 0) ||
305 ((m->busy != 0) || (m->oflags & VPO_BUSY))) {
306 return 0;
307 }
308
309 mc[vm_pageout_page_count] = pb = ps = m;
310 pageout_count = 1;
311 page_base = vm_pageout_page_count;
312 ib = 1;
313 is = 1;
314
315 /*
316 * Scan object for clusterable pages.
317 *
318 * We can cluster ONLY if: ->> the page is NOT
319 * clean, wired, busy, held, or mapped into a
320 * buffer, and one of the following:
321 * 1) The page is inactive, or a seldom used
322 * active page.
323 * -or-
324 * 2) we force the issue.
325 *
326 * During heavy mmap/modification loads the pageout
327 * daemon can really fragment the underlying file
328 * due to flushing pages out of order and not trying
329 * align the clusters (which leave sporatic out-of-order
330 * holes). To solve this problem we do the reverse scan
331 * first and attempt to align our cluster, then do a
332 * forward scan if room remains.
333 */
334 object = m->object;
335 more:
336 while (ib && pageout_count < vm_pageout_page_count) {
337 vm_page_t p;
338
339 if (ib > pindex) {
340 ib = 0;
341 break;
342 }
343
344 if ((p = vm_page_prev(pb)) == NULL ||
345 (p->oflags & VPO_BUSY) != 0 || p->busy != 0) {
346 ib = 0;
347 break;
348 }
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 */
354 ib = 0;
355 break;
356 }
357 mc[--page_base] = pb = p;
358 ++pageout_count;
359 ++ib;
360 /*
361 * alignment boundry, stop here and switch directions. Do
362 * not clear ib.
363 */
364 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
365 break;
366 }
367
368 while (pageout_count < vm_pageout_page_count &&
369 pindex + is < object->size) {
370 vm_page_t p;
371
372 if ((p = vm_page_next(ps)) == NULL ||
373 (p->oflags & VPO_BUSY) != 0 || p->busy != 0)
374 break;
375 vm_page_test_dirty(p);
376 if ((p->dirty & p->valid) == 0 ||
377 p->queue != PQ_INACTIVE ||
378 p->wire_count != 0 || /* may be held by buf cache */
379 p->hold_count != 0) { /* may be undergoing I/O */
380 break;
381 }
382 mc[page_base + pageout_count] = ps = p;
383 ++pageout_count;
384 ++is;
385 }
386
387 /*
388 * If we exhausted our forward scan, continue with the reverse scan
389 * when possible, even past a page boundry. This catches boundry
390 * conditions.
391 */
392 if (ib && pageout_count < vm_pageout_page_count)
393 goto more;
394
395 /*
396 * we allow reads during pageouts...
397 */
398 return (vm_pageout_flush(&mc[page_base], pageout_count, 0));
399 }
400
401 /*
402 * vm_pageout_flush() - launder the given pages
403 *
404 * The given pages are laundered. Note that we setup for the start of
405 * I/O ( i.e. busy the page ), mark it read-only, and bump the object
406 * reference count all in here rather then in the parent. If we want
407 * the parent to do more sophisticated things we may have to change
408 * the ordering.
409 */
410 int
411 vm_pageout_flush(vm_page_t *mc, int count, int flags)
412 {
413 vm_object_t object = mc[0]->object;
414 int pageout_status[count];
415 int numpagedout = 0;
416 int i;
417
418 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
419 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
420 /*
421 * Initiate I/O. Bump the vm_page_t->busy counter and
422 * mark the pages read-only.
423 *
424 * We do not have to fixup the clean/dirty bits here... we can
425 * allow the pager to do it after the I/O completes.
426 *
427 * NOTE! mc[i]->dirty may be partial or fragmented due to an
428 * edge case with file fragments.
429 */
430 for (i = 0; i < count; i++) {
431 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
432 ("vm_pageout_flush: partially invalid page %p index %d/%d",
433 mc[i], i, count));
434 vm_page_io_start(mc[i]);
435 pmap_remove_write(mc[i]);
436 }
437 vm_page_unlock_queues();
438 vm_object_pip_add(object, count);
439
440 vm_pager_put_pages(object, mc, count, flags, pageout_status);
441
442 vm_page_lock_queues();
443 for (i = 0; i < count; i++) {
444 vm_page_t mt = mc[i];
445
446 KASSERT(pageout_status[i] == VM_PAGER_PEND ||
447 (mt->flags & PG_WRITEABLE) == 0,
448 ("vm_pageout_flush: page %p is not write protected", mt));
449 switch (pageout_status[i]) {
450 case VM_PAGER_OK:
451 case VM_PAGER_PEND:
452 numpagedout++;
453 break;
454 case VM_PAGER_BAD:
455 /*
456 * Page outside of range of object. Right now we
457 * essentially lose the changes by pretending it
458 * worked.
459 */
460 pmap_clear_modify(mt);
461 vm_page_undirty(mt);
462 break;
463 case VM_PAGER_ERROR:
464 case VM_PAGER_FAIL:
465 /*
466 * If page couldn't be paged out, then reactivate the
467 * page so it doesn't clog the inactive list. (We
468 * will try paging out it again later).
469 */
470 vm_page_activate(mt);
471 break;
472 case VM_PAGER_AGAIN:
473 break;
474 }
475
476 /*
477 * If the operation is still going, leave the page busy to
478 * block all other accesses. Also, leave the paging in
479 * progress indicator set so that we don't attempt an object
480 * collapse.
481 */
482 if (pageout_status[i] != VM_PAGER_PEND) {
483 vm_object_pip_wakeup(object);
484 vm_page_io_finish(mt);
485 if (vm_page_count_severe())
486 vm_page_try_to_cache(mt);
487 }
488 }
489 return numpagedout;
490 }
491
492 #if !defined(NO_SWAPPING)
493 /*
494 * vm_pageout_object_deactivate_pages
495 *
496 * deactivate enough pages to satisfy the inactive target
497 * requirements or if vm_page_proc_limit is set, then
498 * deactivate all of the pages in the object and its
499 * backing_objects.
500 *
501 * The object and map must be locked.
502 */
503 static void
504 vm_pageout_object_deactivate_pages(pmap, first_object, desired)
505 pmap_t pmap;
506 vm_object_t first_object;
507 long desired;
508 {
509 vm_object_t backing_object, object;
510 vm_page_t p, next;
511 int actcount, rcount, remove_mode;
512
513 VM_OBJECT_LOCK_ASSERT(first_object, MA_OWNED);
514 if (first_object->type == OBJT_DEVICE ||
515 first_object->type == OBJT_SG ||
516 first_object->type == OBJT_PHYS)
517 return;
518 for (object = first_object;; object = backing_object) {
519 if (pmap_resident_count(pmap) <= desired)
520 goto unlock_return;
521 if (object->paging_in_progress)
522 goto unlock_return;
523
524 remove_mode = 0;
525 if (object->shadow_count > 1)
526 remove_mode = 1;
527 /*
528 * scan the objects entire memory queue
529 */
530 rcount = object->resident_page_count;
531 p = TAILQ_FIRST(&object->memq);
532 vm_page_lock_queues();
533 while (p && (rcount-- > 0)) {
534 if (pmap_resident_count(pmap) <= desired) {
535 vm_page_unlock_queues();
536 goto unlock_return;
537 }
538 next = TAILQ_NEXT(p, listq);
539 cnt.v_pdpages++;
540 if (p->wire_count != 0 ||
541 p->hold_count != 0 ||
542 p->busy != 0 ||
543 (p->oflags & VPO_BUSY) ||
544 (p->flags & PG_UNMANAGED) ||
545 !pmap_page_exists_quick(pmap, p)) {
546 p = next;
547 continue;
548 }
549 actcount = pmap_ts_referenced(p);
550 if (actcount) {
551 vm_page_flag_set(p, PG_REFERENCED);
552 } else if (p->flags & PG_REFERENCED) {
553 actcount = 1;
554 }
555 if ((p->queue != PQ_ACTIVE) &&
556 (p->flags & PG_REFERENCED)) {
557 vm_page_activate(p);
558 p->act_count += actcount;
559 vm_page_flag_clear(p, PG_REFERENCED);
560 } else if (p->queue == PQ_ACTIVE) {
561 if ((p->flags & PG_REFERENCED) == 0) {
562 p->act_count -= min(p->act_count, ACT_DECLINE);
563 if (!remove_mode && (vm_pageout_algorithm || (p->act_count == 0))) {
564 pmap_remove_all(p);
565 vm_page_deactivate(p);
566 } else {
567 vm_page_requeue(p);
568 }
569 } else {
570 vm_page_activate(p);
571 vm_page_flag_clear(p, PG_REFERENCED);
572 if (p->act_count < (ACT_MAX - ACT_ADVANCE))
573 p->act_count += ACT_ADVANCE;
574 vm_page_requeue(p);
575 }
576 } else if (p->queue == PQ_INACTIVE) {
577 pmap_remove_all(p);
578 }
579 p = next;
580 }
581 vm_page_unlock_queues();
582 if ((backing_object = object->backing_object) == NULL)
583 goto unlock_return;
584 VM_OBJECT_LOCK(backing_object);
585 if (object != first_object)
586 VM_OBJECT_UNLOCK(object);
587 }
588 unlock_return:
589 if (object != first_object)
590 VM_OBJECT_UNLOCK(object);
591 }
592
593 /*
594 * deactivate some number of pages in a map, try to do it fairly, but
595 * that is really hard to do.
596 */
597 static void
598 vm_pageout_map_deactivate_pages(map, desired)
599 vm_map_t map;
600 long desired;
601 {
602 vm_map_entry_t tmpe;
603 vm_object_t obj, bigobj;
604 int nothingwired;
605
606 if (!vm_map_trylock(map))
607 return;
608
609 bigobj = NULL;
610 nothingwired = TRUE;
611
612 /*
613 * first, search out the biggest object, and try to free pages from
614 * that.
615 */
616 tmpe = map->header.next;
617 while (tmpe != &map->header) {
618 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
619 obj = tmpe->object.vm_object;
620 if (obj != NULL && VM_OBJECT_TRYLOCK(obj)) {
621 if (obj->shadow_count <= 1 &&
622 (bigobj == NULL ||
623 bigobj->resident_page_count < obj->resident_page_count)) {
624 if (bigobj != NULL)
625 VM_OBJECT_UNLOCK(bigobj);
626 bigobj = obj;
627 } else
628 VM_OBJECT_UNLOCK(obj);
629 }
630 }
631 if (tmpe->wired_count > 0)
632 nothingwired = FALSE;
633 tmpe = tmpe->next;
634 }
635
636 if (bigobj != NULL) {
637 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
638 VM_OBJECT_UNLOCK(bigobj);
639 }
640 /*
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.
643 */
644 tmpe = map->header.next;
645 while (tmpe != &map->header) {
646 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
647 break;
648 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
649 obj = tmpe->object.vm_object;
650 if (obj != NULL) {
651 VM_OBJECT_LOCK(obj);
652 vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
653 VM_OBJECT_UNLOCK(obj);
654 }
655 }
656 tmpe = tmpe->next;
657 }
658
659 /*
660 * Remove all mappings if a process is swapped out, this will free page
661 * table pages.
662 */
663 if (desired == 0 && nothingwired) {
664 pmap_remove(vm_map_pmap(map), vm_map_min(map),
665 vm_map_max(map));
666 }
667 vm_map_unlock(map);
668 }
669 #endif /* !defined(NO_SWAPPING) */
670
671 /*
672 * vm_pageout_scan does the dirty work for the pageout daemon.
673 */
674 static void
675 vm_pageout_scan(int pass)
676 {
677 vm_page_t m, next;
678 struct vm_page marker;
679 int page_shortage, maxscan, pcount;
680 int addl_page_shortage, addl_page_shortage_init;
681 vm_object_t object;
682 int actcount;
683 int vnodes_skipped = 0;
684 int maxlaunder;
685
686 /*
687 * Decrease registered cache sizes.
688 */
689 EVENTHANDLER_INVOKE(vm_lowmem, 0);
690 /*
691 * We do this explicitly after the caches have been drained above.
692 */
693 uma_reclaim();
694
695 addl_page_shortage_init = atomic_readandclear_int(&vm_pageout_deficit);
696
697 /*
698 * Calculate the number of pages we want to either free or move
699 * to the cache.
700 */
701 page_shortage = vm_paging_target() + addl_page_shortage_init;
702
703 /*
704 * Initialize our marker
705 */
706 bzero(&marker, sizeof(marker));
707 marker.flags = PG_FICTITIOUS | PG_MARKER;
708 marker.oflags = VPO_BUSY;
709 marker.queue = PQ_INACTIVE;
710 marker.wire_count = 1;
711
712 /*
713 * Start scanning the inactive queue for pages we can move to the
714 * cache or free. The scan will stop when the target is reached or
715 * we have scanned the entire inactive queue. Note that m->act_count
716 * is not used to form decisions for the inactive queue, only for the
717 * active queue.
718 *
719 * maxlaunder limits the number of dirty pages we flush per scan.
720 * For most systems a smaller value (16 or 32) is more robust under
721 * extreme memory and disk pressure because any unnecessary writes
722 * to disk can result in extreme performance degredation. However,
723 * systems with excessive dirty pages (especially when MAP_NOSYNC is
724 * used) will die horribly with limited laundering. If the pageout
725 * daemon cannot clean enough pages in the first pass, we let it go
726 * all out in succeeding passes.
727 */
728 if ((maxlaunder = vm_max_launder) <= 1)
729 maxlaunder = 1;
730 if (pass)
731 maxlaunder = 10000;
732 vm_page_lock_queues();
733 rescan0:
734 addl_page_shortage = addl_page_shortage_init;
735 maxscan = cnt.v_inactive_count;
736
737 for (m = TAILQ_FIRST(&vm_page_queues[PQ_INACTIVE].pl);
738 m != NULL && maxscan-- > 0 && page_shortage > 0;
739 m = next) {
740
741 cnt.v_pdpages++;
742
743 if (VM_PAGE_GETQUEUE(m) != PQ_INACTIVE) {
744 goto rescan0;
745 }
746
747 next = TAILQ_NEXT(m, pageq);
748 object = m->object;
749
750 /*
751 * skip marker pages
752 */
753 if (m->flags & PG_MARKER)
754 continue;
755
756 /*
757 * A held page may be undergoing I/O, so skip it.
758 */
759 if (m->hold_count) {
760 vm_page_requeue(m);
761 addl_page_shortage++;
762 continue;
763 }
764 /*
765 * Don't mess with busy pages, keep in the front of the
766 * queue, most likely are being paged out.
767 */
768 if (!VM_OBJECT_TRYLOCK(object) &&
769 (!vm_pageout_fallback_object_lock(m, &next) ||
770 m->hold_count != 0)) {
771 VM_OBJECT_UNLOCK(object);
772 addl_page_shortage++;
773 continue;
774 }
775 if (m->busy || (m->oflags & VPO_BUSY)) {
776 VM_OBJECT_UNLOCK(object);
777 addl_page_shortage++;
778 continue;
779 }
780
781 /*
782 * If the object is not being used, we ignore previous
783 * references.
784 */
785 if (object->ref_count == 0) {
786 vm_page_flag_clear(m, PG_REFERENCED);
787 pmap_clear_reference(m);
788
789 /*
790 * Otherwise, if the page has been referenced while in the
791 * inactive queue, we bump the "activation count" upwards,
792 * making it less likely that the page will be added back to
793 * the inactive queue prematurely again. Here we check the
794 * page tables (or emulated bits, if any), given the upper
795 * level VM system not knowing anything about existing
796 * references.
797 */
798 } else if (((m->flags & PG_REFERENCED) == 0) &&
799 (actcount = pmap_ts_referenced(m))) {
800 vm_page_activate(m);
801 VM_OBJECT_UNLOCK(object);
802 m->act_count += (actcount + ACT_ADVANCE);
803 continue;
804 }
805
806 /*
807 * If the upper level VM system knows about any page
808 * references, we activate the page. We also set the
809 * "activation count" higher than normal so that we will less
810 * likely place pages back onto the inactive queue again.
811 */
812 if ((m->flags & PG_REFERENCED) != 0) {
813 vm_page_flag_clear(m, PG_REFERENCED);
814 actcount = pmap_ts_referenced(m);
815 vm_page_activate(m);
816 VM_OBJECT_UNLOCK(object);
817 m->act_count += (actcount + ACT_ADVANCE + 1);
818 continue;
819 }
820
821 /*
822 * If the upper level VM system doesn't know anything about
823 * the page being dirty, we have to check for it again. As
824 * far as the VM code knows, any partially dirty pages are
825 * fully dirty.
826 */
827 if (m->dirty == 0 && !pmap_is_modified(m)) {
828 /*
829 * Avoid a race condition: Unless write access is
830 * removed from the page, another processor could
831 * modify it before all access is removed by the call
832 * to vm_page_cache() below. If vm_page_cache() finds
833 * that the page has been modified when it removes all
834 * access, it panics because it cannot cache dirty
835 * pages. In principle, we could eliminate just write
836 * access here rather than all access. In the expected
837 * case, when there are no last instant modifications
838 * to the page, removing all access will be cheaper
839 * overall.
840 */
841 if ((m->flags & PG_WRITEABLE) != 0)
842 pmap_remove_all(m);
843 } else {
844 vm_page_dirty(m);
845 }
846
847 if (m->valid == 0) {
848 /*
849 * Invalid pages can be easily freed
850 */
851 vm_page_free(m);
852 cnt.v_dfree++;
853 --page_shortage;
854 } else if (m->dirty == 0) {
855 /*
856 * Clean pages can be placed onto the cache queue.
857 * This effectively frees them.
858 */
859 vm_page_cache(m);
860 --page_shortage;
861 } else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) {
862 /*
863 * Dirty pages need to be paged out, but flushing
864 * a page is extremely expensive verses freeing
865 * a clean page. Rather then artificially limiting
866 * the number of pages we can flush, we instead give
867 * dirty pages extra priority on the inactive queue
868 * by forcing them to be cycled through the queue
869 * twice before being flushed, after which the
870 * (now clean) page will cycle through once more
871 * before being freed. This significantly extends
872 * the thrash point for a heavily loaded machine.
873 */
874 vm_page_flag_set(m, PG_WINATCFLS);
875 vm_page_requeue(m);
876 } else if (maxlaunder > 0) {
877 /*
878 * We always want to try to flush some dirty pages if
879 * we encounter them, to keep the system stable.
880 * Normally this number is small, but under extreme
881 * pressure where there are insufficient clean pages
882 * on the inactive queue, we may have to go all out.
883 */
884 int swap_pageouts_ok, vfslocked = 0;
885 struct vnode *vp = NULL;
886 struct mount *mp = NULL;
887
888 if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
889 swap_pageouts_ok = 1;
890 } else {
891 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
892 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
893 vm_page_count_min());
894
895 }
896
897 /*
898 * We don't bother paging objects that are "dead".
899 * Those objects are in a "rundown" state.
900 */
901 if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
902 VM_OBJECT_UNLOCK(object);
903 vm_page_requeue(m);
904 continue;
905 }
906
907 /*
908 * Following operations may unlock
909 * vm_page_queue_mtx, invalidating the 'next'
910 * pointer. To prevent an inordinate number
911 * of restarts we use our marker to remember
912 * our place.
913 *
914 */
915 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE].pl,
916 m, &marker, pageq);
917 /*
918 * The object is already known NOT to be dead. It
919 * is possible for the vget() to block the whole
920 * pageout daemon, but the new low-memory handling
921 * code should prevent it.
922 *
923 * The previous code skipped locked vnodes and, worse,
924 * reordered pages in the queue. This results in
925 * completely non-deterministic operation and, on a
926 * busy system, can lead to extremely non-optimal
927 * pageouts. For example, it can cause clean pages
928 * to be freed and dirty pages to be moved to the end
929 * of the queue. Since dirty pages are also moved to
930 * the end of the queue once-cleaned, this gives
931 * way too large a weighting to defering the freeing
932 * of dirty pages.
933 *
934 * We can't wait forever for the vnode lock, we might
935 * deadlock due to a vn_read() getting stuck in
936 * vm_wait while holding this vnode. We skip the
937 * vnode if we can't get it in a reasonable amount
938 * of time.
939 */
940 if (object->type == OBJT_VNODE) {
941 vp = object->handle;
942 if (vp->v_type == VREG &&
943 vn_start_write(vp, &mp, V_NOWAIT) != 0) {
944 mp = NULL;
945 ++pageout_lock_miss;
946 if (object->flags & OBJ_MIGHTBEDIRTY)
947 vnodes_skipped++;
948 goto unlock_and_continue;
949 }
950 vm_page_unlock_queues();
951 vm_object_reference_locked(object);
952 VM_OBJECT_UNLOCK(object);
953 vfslocked = VFS_LOCK_GIANT(vp->v_mount);
954 if (vget(vp, LK_EXCLUSIVE | LK_TIMELOCK,
955 curthread)) {
956 VM_OBJECT_LOCK(object);
957 vm_page_lock_queues();
958 ++pageout_lock_miss;
959 if (object->flags & OBJ_MIGHTBEDIRTY)
960 vnodes_skipped++;
961 vp = NULL;
962 goto unlock_and_continue;
963 }
964 VM_OBJECT_LOCK(object);
965 vm_page_lock_queues();
966 /*
967 * The page might have been moved to another
968 * queue during potential blocking in vget()
969 * above. The page might have been freed and
970 * reused for another vnode.
971 */
972 if (VM_PAGE_GETQUEUE(m) != PQ_INACTIVE ||
973 m->object != object ||
974 TAILQ_NEXT(m, pageq) != &marker) {
975 if (object->flags & OBJ_MIGHTBEDIRTY)
976 vnodes_skipped++;
977 goto unlock_and_continue;
978 }
979
980 /*
981 * The page may have been busied during the
982 * blocking in vget(). We don't move the
983 * page back onto the end of the queue so that
984 * statistics are more correct if we don't.
985 */
986 if (m->busy || (m->oflags & VPO_BUSY)) {
987 goto unlock_and_continue;
988 }
989
990 /*
991 * If the page has become held it might
992 * be undergoing I/O, so skip it
993 */
994 if (m->hold_count) {
995 vm_page_requeue(m);
996 if (object->flags & OBJ_MIGHTBEDIRTY)
997 vnodes_skipped++;
998 goto unlock_and_continue;
999 }
1000 }
1001
1002 /*
1003 * If a page is dirty, then it is either being washed
1004 * (but not yet cleaned) or it is still in the
1005 * laundry. If it is still in the laundry, then we
1006 * start the cleaning operation.
1007 *
1008 * decrement page_shortage on success to account for
1009 * the (future) cleaned page. Otherwise we could wind
1010 * up laundering or cleaning too many pages.
1011 */
1012 if (vm_pageout_clean(m) != 0) {
1013 --page_shortage;
1014 --maxlaunder;
1015 }
1016 unlock_and_continue:
1017 VM_OBJECT_UNLOCK(object);
1018 if (mp != NULL) {
1019 vm_page_unlock_queues();
1020 if (vp != NULL)
1021 vput(vp);
1022 VFS_UNLOCK_GIANT(vfslocked);
1023 vm_object_deallocate(object);
1024 vn_finished_write(mp);
1025 vm_page_lock_queues();
1026 }
1027 next = TAILQ_NEXT(&marker, pageq);
1028 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl,
1029 &marker, pageq);
1030 continue;
1031 }
1032 VM_OBJECT_UNLOCK(object);
1033 }
1034
1035 /*
1036 * Compute the number of pages we want to try to move from the
1037 * active queue to the inactive queue.
1038 */
1039 page_shortage = vm_paging_target() +
1040 cnt.v_inactive_target - cnt.v_inactive_count;
1041 page_shortage += addl_page_shortage;
1042
1043 /*
1044 * Scan the active queue for things we can deactivate. We nominally
1045 * track the per-page activity counter and use it to locate
1046 * deactivation candidates.
1047 */
1048 pcount = cnt.v_active_count;
1049 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
1050
1051 while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) {
1052
1053 KASSERT(VM_PAGE_INQUEUE2(m, PQ_ACTIVE),
1054 ("vm_pageout_scan: page %p isn't active", m));
1055
1056 next = TAILQ_NEXT(m, pageq);
1057 object = m->object;
1058 if ((m->flags & PG_MARKER) != 0) {
1059 m = next;
1060 continue;
1061 }
1062 if (!VM_OBJECT_TRYLOCK(object) &&
1063 !vm_pageout_fallback_object_lock(m, &next)) {
1064 VM_OBJECT_UNLOCK(object);
1065 m = next;
1066 continue;
1067 }
1068
1069 /*
1070 * Don't deactivate pages that are busy.
1071 */
1072 if ((m->busy != 0) ||
1073 (m->oflags & VPO_BUSY) ||
1074 (m->hold_count != 0)) {
1075 VM_OBJECT_UNLOCK(object);
1076 vm_page_requeue(m);
1077 m = next;
1078 continue;
1079 }
1080
1081 /*
1082 * The count for pagedaemon pages is done after checking the
1083 * page for eligibility...
1084 */
1085 cnt.v_pdpages++;
1086
1087 /*
1088 * Check to see "how much" the page has been used.
1089 */
1090 actcount = 0;
1091 if (object->ref_count != 0) {
1092 if (m->flags & PG_REFERENCED) {
1093 actcount += 1;
1094 }
1095 actcount += pmap_ts_referenced(m);
1096 if (actcount) {
1097 m->act_count += ACT_ADVANCE + actcount;
1098 if (m->act_count > ACT_MAX)
1099 m->act_count = ACT_MAX;
1100 }
1101 }
1102
1103 /*
1104 * Since we have "tested" this bit, we need to clear it now.
1105 */
1106 vm_page_flag_clear(m, PG_REFERENCED);
1107
1108 /*
1109 * Only if an object is currently being used, do we use the
1110 * page activation count stats.
1111 */
1112 if (actcount && (object->ref_count != 0)) {
1113 vm_page_requeue(m);
1114 } else {
1115 m->act_count -= min(m->act_count, ACT_DECLINE);
1116 if (vm_pageout_algorithm ||
1117 object->ref_count == 0 ||
1118 m->act_count == 0) {
1119 page_shortage--;
1120 if (object->ref_count == 0) {
1121 pmap_remove_all(m);
1122 if (m->dirty == 0)
1123 vm_page_cache(m);
1124 else
1125 vm_page_deactivate(m);
1126 } else {
1127 vm_page_deactivate(m);
1128 }
1129 } else {
1130 vm_page_requeue(m);
1131 }
1132 }
1133 VM_OBJECT_UNLOCK(object);
1134 m = next;
1135 }
1136 vm_page_unlock_queues();
1137 #if !defined(NO_SWAPPING)
1138 /*
1139 * Idle process swapout -- run once per second.
1140 */
1141 if (vm_swap_idle_enabled) {
1142 static long lsec;
1143 if (time_second != lsec) {
1144 vm_req_vmdaemon(VM_SWAP_IDLE);
1145 lsec = time_second;
1146 }
1147 }
1148 #endif
1149
1150 /*
1151 * If we didn't get enough free pages, and we have skipped a vnode
1152 * in a writeable object, wakeup the sync daemon. And kick swapout
1153 * if we did not get enough free pages.
1154 */
1155 if (vm_paging_target() > 0) {
1156 if (vnodes_skipped && vm_page_count_min())
1157 (void) speedup_syncer();
1158 #if !defined(NO_SWAPPING)
1159 if (vm_swap_enabled && vm_page_count_target())
1160 vm_req_vmdaemon(VM_SWAP_NORMAL);
1161 #endif
1162 }
1163
1164 /*
1165 * If we are critically low on one of RAM or swap and low on
1166 * the other, kill the largest process. However, we avoid
1167 * doing this on the first pass in order to give ourselves a
1168 * chance to flush out dirty vnode-backed pages and to allow
1169 * active pages to be moved to the inactive queue and reclaimed.
1170 */
1171 if (pass != 0 &&
1172 ((swap_pager_avail < 64 && vm_page_count_min()) ||
1173 (swap_pager_full && vm_paging_target() > 0)))
1174 vm_pageout_oom(VM_OOM_MEM);
1175 }
1176
1177
1178 void
1179 vm_pageout_oom(int shortage)
1180 {
1181 struct proc *p, *bigproc;
1182 vm_offset_t size, bigsize;
1183 struct thread *td;
1184 struct vmspace *vm;
1185
1186 /*
1187 * We keep the process bigproc locked once we find it to keep anyone
1188 * from messing with it; however, there is a possibility of
1189 * deadlock if process B is bigproc and one of it's child processes
1190 * attempts to propagate a signal to B while we are waiting for A's
1191 * lock while walking this list. To avoid this, we don't block on
1192 * the process lock but just skip a process if it is already locked.
1193 */
1194 bigproc = NULL;
1195 bigsize = 0;
1196 sx_slock(&allproc_lock);
1197 FOREACH_PROC_IN_SYSTEM(p) {
1198 int breakout;
1199
1200 if (PROC_TRYLOCK(p) == 0)
1201 continue;
1202 /*
1203 * If this is a system or protected process, skip it.
1204 */
1205 if ((p->p_flag & (P_INEXEC | P_PROTECTED | P_SYSTEM)) ||
1206 (p->p_pid == 1) ||
1207 ((p->p_pid < 48) && (swap_pager_avail != 0))) {
1208 PROC_UNLOCK(p);
1209 continue;
1210 }
1211 /*
1212 * If the process is in a non-running type state,
1213 * don't touch it. Check all the threads individually.
1214 */
1215 PROC_SLOCK(p);
1216 breakout = 0;
1217 FOREACH_THREAD_IN_PROC(p, td) {
1218 thread_lock(td);
1219 if (!TD_ON_RUNQ(td) &&
1220 !TD_IS_RUNNING(td) &&
1221 !TD_IS_SLEEPING(td)) {
1222 thread_unlock(td);
1223 breakout = 1;
1224 break;
1225 }
1226 thread_unlock(td);
1227 }
1228 PROC_SUNLOCK(p);
1229 if (breakout) {
1230 PROC_UNLOCK(p);
1231 continue;
1232 }
1233 /*
1234 * get the process size
1235 */
1236 vm = vmspace_acquire_ref(p);
1237 if (vm == NULL) {
1238 PROC_UNLOCK(p);
1239 continue;
1240 }
1241 if (!vm_map_trylock_read(&vm->vm_map)) {
1242 vmspace_free(vm);
1243 PROC_UNLOCK(p);
1244 continue;
1245 }
1246 size = vmspace_swap_count(vm);
1247 vm_map_unlock_read(&vm->vm_map);
1248 if (shortage == VM_OOM_MEM)
1249 size += vmspace_resident_count(vm);
1250 vmspace_free(vm);
1251 /*
1252 * if the this process is bigger than the biggest one
1253 * remember it.
1254 */
1255 if (size > bigsize) {
1256 if (bigproc != NULL)
1257 PROC_UNLOCK(bigproc);
1258 bigproc = p;
1259 bigsize = size;
1260 } else
1261 PROC_UNLOCK(p);
1262 }
1263 sx_sunlock(&allproc_lock);
1264 if (bigproc != NULL) {
1265 killproc(bigproc, "out of swap space");
1266 PROC_SLOCK(bigproc);
1267 sched_nice(bigproc, PRIO_MIN);
1268 PROC_SUNLOCK(bigproc);
1269 PROC_UNLOCK(bigproc);
1270 wakeup(&cnt.v_free_count);
1271 }
1272 }
1273
1274 /*
1275 * This routine tries to maintain the pseudo LRU active queue,
1276 * so that during long periods of time where there is no paging,
1277 * that some statistic accumulation still occurs. This code
1278 * helps the situation where paging just starts to occur.
1279 */
1280 static void
1281 vm_pageout_page_stats()
1282 {
1283 vm_object_t object;
1284 vm_page_t m,next;
1285 int pcount,tpcount; /* Number of pages to check */
1286 static int fullintervalcount = 0;
1287 int page_shortage;
1288
1289 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1290 page_shortage =
1291 (cnt.v_inactive_target + cnt.v_cache_max + cnt.v_free_min) -
1292 (cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
1293
1294 if (page_shortage <= 0)
1295 return;
1296
1297 pcount = cnt.v_active_count;
1298 fullintervalcount += vm_pageout_stats_interval;
1299 if (fullintervalcount < vm_pageout_full_stats_interval) {
1300 tpcount = (int64_t)vm_pageout_stats_max * cnt.v_active_count /
1301 cnt.v_page_count;
1302 if (pcount > tpcount)
1303 pcount = tpcount;
1304 } else {
1305 fullintervalcount = 0;
1306 }
1307
1308 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
1309 while ((m != NULL) && (pcount-- > 0)) {
1310 int actcount;
1311
1312 KASSERT(VM_PAGE_INQUEUE2(m, PQ_ACTIVE),
1313 ("vm_pageout_page_stats: page %p isn't active", m));
1314
1315 next = TAILQ_NEXT(m, pageq);
1316 object = m->object;
1317
1318 if ((m->flags & PG_MARKER) != 0) {
1319 m = next;
1320 continue;
1321 }
1322 if (!VM_OBJECT_TRYLOCK(object) &&
1323 !vm_pageout_fallback_object_lock(m, &next)) {
1324 VM_OBJECT_UNLOCK(object);
1325 m = next;
1326 continue;
1327 }
1328
1329 /*
1330 * Don't deactivate pages that are busy.
1331 */
1332 if ((m->busy != 0) ||
1333 (m->oflags & VPO_BUSY) ||
1334 (m->hold_count != 0)) {
1335 VM_OBJECT_UNLOCK(object);
1336 vm_page_requeue(m);
1337 m = next;
1338 continue;
1339 }
1340
1341 actcount = 0;
1342 if (m->flags & PG_REFERENCED) {
1343 vm_page_flag_clear(m, PG_REFERENCED);
1344 actcount += 1;
1345 }
1346
1347 actcount += pmap_ts_referenced(m);
1348 if (actcount) {
1349 m->act_count += ACT_ADVANCE + actcount;
1350 if (m->act_count > ACT_MAX)
1351 m->act_count = ACT_MAX;
1352 vm_page_requeue(m);
1353 } else {
1354 if (m->act_count == 0) {
1355 /*
1356 * We turn off page access, so that we have
1357 * more accurate RSS stats. We don't do this
1358 * in the normal page deactivation when the
1359 * system is loaded VM wise, because the
1360 * cost of the large number of page protect
1361 * operations would be higher than the value
1362 * of doing the operation.
1363 */
1364 pmap_remove_all(m);
1365 vm_page_deactivate(m);
1366 } else {
1367 m->act_count -= min(m->act_count, ACT_DECLINE);
1368 vm_page_requeue(m);
1369 }
1370 }
1371 VM_OBJECT_UNLOCK(object);
1372 m = next;
1373 }
1374 }
1375
1376 /*
1377 * vm_pageout is the high level pageout daemon.
1378 */
1379 static void
1380 vm_pageout()
1381 {
1382 int error, pass;
1383
1384 /*
1385 * Initialize some paging parameters.
1386 */
1387 cnt.v_interrupt_free_min = 2;
1388 if (cnt.v_page_count < 2000)
1389 vm_pageout_page_count = 8;
1390
1391 /*
1392 * v_free_reserved needs to include enough for the largest
1393 * swap pager structures plus enough for any pv_entry structs
1394 * when paging.
1395 */
1396 if (cnt.v_page_count > 1024)
1397 cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
1398 else
1399 cnt.v_free_min = 4;
1400 cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
1401 cnt.v_interrupt_free_min;
1402 cnt.v_free_reserved = vm_pageout_page_count +
1403 cnt.v_pageout_free_min + (cnt.v_page_count / 768);
1404 cnt.v_free_severe = cnt.v_free_min / 2;
1405 cnt.v_free_min += cnt.v_free_reserved;
1406 cnt.v_free_severe += cnt.v_free_reserved;
1407
1408 /*
1409 * v_free_target and v_cache_min control pageout hysteresis. Note
1410 * that these are more a measure of the VM cache queue hysteresis
1411 * then the VM free queue. Specifically, v_free_target is the
1412 * high water mark (free+cache pages).
1413 *
1414 * v_free_reserved + v_cache_min (mostly means v_cache_min) is the
1415 * low water mark, while v_free_min is the stop. v_cache_min must
1416 * be big enough to handle memory needs while the pageout daemon
1417 * is signalled and run to free more pages.
1418 */
1419 if (cnt.v_free_count > 6144)
1420 cnt.v_free_target = 4 * cnt.v_free_min + cnt.v_free_reserved;
1421 else
1422 cnt.v_free_target = 2 * cnt.v_free_min + cnt.v_free_reserved;
1423
1424 if (cnt.v_free_count > 2048) {
1425 cnt.v_cache_min = cnt.v_free_target;
1426 cnt.v_cache_max = 2 * cnt.v_cache_min;
1427 cnt.v_inactive_target = (3 * cnt.v_free_target) / 2;
1428 } else {
1429 cnt.v_cache_min = 0;
1430 cnt.v_cache_max = 0;
1431 cnt.v_inactive_target = cnt.v_free_count / 4;
1432 }
1433 if (cnt.v_inactive_target > cnt.v_free_count / 3)
1434 cnt.v_inactive_target = cnt.v_free_count / 3;
1435
1436 /* XXX does not really belong here */
1437 if (vm_page_max_wired == 0)
1438 vm_page_max_wired = cnt.v_free_count / 3;
1439
1440 if (vm_pageout_stats_max == 0)
1441 vm_pageout_stats_max = cnt.v_free_target;
1442
1443 /*
1444 * Set interval in seconds for stats scan.
1445 */
1446 if (vm_pageout_stats_interval == 0)
1447 vm_pageout_stats_interval = 5;
1448 if (vm_pageout_full_stats_interval == 0)
1449 vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
1450
1451 swap_pager_swap_init();
1452 pass = 0;
1453 /*
1454 * The pageout daemon is never done, so loop forever.
1455 */
1456 while (TRUE) {
1457 /*
1458 * If we have enough free memory, wakeup waiters. Do
1459 * not clear vm_pages_needed until we reach our target,
1460 * otherwise we may be woken up over and over again and
1461 * waste a lot of cpu.
1462 */
1463 mtx_lock(&vm_page_queue_free_mtx);
1464 if (vm_pages_needed && !vm_page_count_min()) {
1465 if (!vm_paging_needed())
1466 vm_pages_needed = 0;
1467 wakeup(&cnt.v_free_count);
1468 }
1469 if (vm_pages_needed) {
1470 /*
1471 * Still not done, take a second pass without waiting
1472 * (unlimited dirty cleaning), otherwise sleep a bit
1473 * and try again.
1474 */
1475 ++pass;
1476 if (pass > 1)
1477 msleep(&vm_pages_needed,
1478 &vm_page_queue_free_mtx, PVM, "psleep",
1479 hz / 2);
1480 } else {
1481 /*
1482 * Good enough, sleep & handle stats. Prime the pass
1483 * for the next run.
1484 */
1485 if (pass > 1)
1486 pass = 1;
1487 else
1488 pass = 0;
1489 error = msleep(&vm_pages_needed,
1490 &vm_page_queue_free_mtx, PVM, "psleep",
1491 vm_pageout_stats_interval * hz);
1492 if (error && !vm_pages_needed) {
1493 mtx_unlock(&vm_page_queue_free_mtx);
1494 pass = 0;
1495 vm_page_lock_queues();
1496 vm_pageout_page_stats();
1497 vm_page_unlock_queues();
1498 continue;
1499 }
1500 }
1501 if (vm_pages_needed)
1502 cnt.v_pdwakeups++;
1503 mtx_unlock(&vm_page_queue_free_mtx);
1504 vm_pageout_scan(pass);
1505 }
1506 }
1507
1508 /*
1509 * Unless the free page queue lock is held by the caller, this function
1510 * should be regarded as advisory. Specifically, the caller should
1511 * not msleep() on &cnt.v_free_count following this function unless
1512 * the free page queue lock is held until the msleep() is performed.
1513 */
1514 void
1515 pagedaemon_wakeup()
1516 {
1517
1518 if (!vm_pages_needed && curthread->td_proc != pageproc) {
1519 vm_pages_needed = 1;
1520 wakeup(&vm_pages_needed);
1521 }
1522 }
1523
1524 #if !defined(NO_SWAPPING)
1525 static void
1526 vm_req_vmdaemon(int req)
1527 {
1528 static int lastrun = 0;
1529
1530 mtx_lock(&vm_daemon_mtx);
1531 vm_pageout_req_swapout |= req;
1532 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
1533 wakeup(&vm_daemon_needed);
1534 lastrun = ticks;
1535 }
1536 mtx_unlock(&vm_daemon_mtx);
1537 }
1538
1539 static void
1540 vm_daemon()
1541 {
1542 struct rlimit rsslim;
1543 struct proc *p;
1544 struct thread *td;
1545 struct vmspace *vm;
1546 int breakout, swapout_flags;
1547
1548 while (TRUE) {
1549 mtx_lock(&vm_daemon_mtx);
1550 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 0);
1551 swapout_flags = vm_pageout_req_swapout;
1552 vm_pageout_req_swapout = 0;
1553 mtx_unlock(&vm_daemon_mtx);
1554 if (swapout_flags)
1555 swapout_procs(swapout_flags);
1556
1557 /*
1558 * scan the processes for exceeding their rlimits or if
1559 * process is swapped out -- deactivate pages
1560 */
1561 sx_slock(&allproc_lock);
1562 FOREACH_PROC_IN_SYSTEM(p) {
1563 vm_pindex_t limit, size;
1564
1565 /*
1566 * if this is a system process or if we have already
1567 * looked at this process, skip it.
1568 */
1569 PROC_LOCK(p);
1570 if (p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
1571 PROC_UNLOCK(p);
1572 continue;
1573 }
1574 /*
1575 * if the process is in a non-running type state,
1576 * don't touch it.
1577 */
1578 PROC_SLOCK(p);
1579 breakout = 0;
1580 FOREACH_THREAD_IN_PROC(p, td) {
1581 thread_lock(td);
1582 if (!TD_ON_RUNQ(td) &&
1583 !TD_IS_RUNNING(td) &&
1584 !TD_IS_SLEEPING(td)) {
1585 thread_unlock(td);
1586 breakout = 1;
1587 break;
1588 }
1589 thread_unlock(td);
1590 }
1591 PROC_SUNLOCK(p);
1592 if (breakout) {
1593 PROC_UNLOCK(p);
1594 continue;
1595 }
1596 /*
1597 * get a limit
1598 */
1599 lim_rlimit(p, RLIMIT_RSS, &rsslim);
1600 limit = OFF_TO_IDX(
1601 qmin(rsslim.rlim_cur, rsslim.rlim_max));
1602
1603 /*
1604 * let processes that are swapped out really be
1605 * swapped out set the limit to nothing (will force a
1606 * swap-out.)
1607 */
1608 if ((p->p_flag & P_INMEM) == 0)
1609 limit = 0; /* XXX */
1610 vm = vmspace_acquire_ref(p);
1611 PROC_UNLOCK(p);
1612 if (vm == NULL)
1613 continue;
1614
1615 size = vmspace_resident_count(vm);
1616 if (limit >= 0 && size >= limit) {
1617 vm_pageout_map_deactivate_pages(
1618 &vm->vm_map, limit);
1619 }
1620 vmspace_free(vm);
1621 }
1622 sx_sunlock(&allproc_lock);
1623 }
1624 }
1625 #endif /* !defined(NO_SWAPPING) */
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