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 *
9 * This code is derived from software contributed to Berkeley by
10 * The Mach Operating System project at Carnegie-Mellon University.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Berkeley and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
39 *
40 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
41 *
42 *
43 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
44 * All rights reserved.
45 *
46 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
47 *
48 * Permission to use, copy, modify and distribute this software and
49 * its documentation is hereby granted, provided that both the copyright
50 * notice and this permission notice appear in all copies of the
51 * software, derivative works or modified versions, and any portions
52 * thereof, and that both notices appear in supporting documentation.
53 *
54 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
55 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
56 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
57 *
58 * Carnegie Mellon requests users of this software to return to
59 *
60 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
61 * School of Computer Science
62 * Carnegie Mellon University
63 * Pittsburgh PA 15213-3890
64 *
65 * any improvements or extensions that they make and grant Carnegie the
66 * rights to redistribute these changes.
67 */
68
69 /*
70 * The proverbial page-out daemon.
71 */
72
73 #include <sys/cdefs.h>
74 __FBSDID("$FreeBSD: releng/5.2/sys/vm/vm_pageout.c 121455 2003-10-24 06:43:04Z alc $");
75
76 #include "opt_vm.h"
77 #include <sys/param.h>
78 #include <sys/systm.h>
79 #include <sys/kernel.h>
80 #include <sys/eventhandler.h>
81 #include <sys/lock.h>
82 #include <sys/mutex.h>
83 #include <sys/proc.h>
84 #include <sys/kthread.h>
85 #include <sys/ktr.h>
86 #include <sys/resourcevar.h>
87 #include <sys/sched.h>
88 #include <sys/signalvar.h>
89 #include <sys/vnode.h>
90 #include <sys/vmmeter.h>
91 #include <sys/sx.h>
92 #include <sys/sysctl.h>
93
94 #include <vm/vm.h>
95 #include <vm/vm_param.h>
96 #include <vm/vm_object.h>
97 #include <vm/vm_page.h>
98 #include <vm/vm_map.h>
99 #include <vm/vm_pageout.h>
100 #include <vm/vm_pager.h>
101 #include <vm/swap_pager.h>
102 #include <vm/vm_extern.h>
103 #include <vm/uma.h>
104
105 #include <machine/mutex.h>
106
107 /*
108 * System initialization
109 */
110
111 /* the kernel process "vm_pageout"*/
112 static void vm_pageout(void);
113 static int vm_pageout_clean(vm_page_t);
114 static void vm_pageout_pmap_collect(void);
115 static void vm_pageout_scan(int pass);
116
117 struct proc *pageproc;
118
119 static struct kproc_desc page_kp = {
120 "pagedaemon",
121 vm_pageout,
122 &pageproc
123 };
124 SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start, &page_kp)
125
126 #if !defined(NO_SWAPPING)
127 /* the kernel process "vm_daemon"*/
128 static void vm_daemon(void);
129 static struct proc *vmproc;
130
131 static struct kproc_desc vm_kp = {
132 "vmdaemon",
133 vm_daemon,
134 &vmproc
135 };
136 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp)
137 #endif
138
139
140 int vm_pages_needed; /* Event on which pageout daemon sleeps */
141 int vm_pageout_deficit; /* Estimated number of pages deficit */
142 int vm_pageout_pages_needed; /* flag saying that the pageout daemon needs pages */
143
144 #if !defined(NO_SWAPPING)
145 static int vm_pageout_req_swapout; /* XXX */
146 static int vm_daemon_needed;
147 #endif
148 static int vm_max_launder = 32;
149 static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0;
150 static int vm_pageout_full_stats_interval = 0;
151 static int vm_pageout_stats_free_max=0, vm_pageout_algorithm=0;
152 static int defer_swap_pageouts=0;
153 static int disable_swap_pageouts=0;
154
155 #if defined(NO_SWAPPING)
156 static int vm_swap_enabled=0;
157 static int vm_swap_idle_enabled=0;
158 #else
159 static int vm_swap_enabled=1;
160 static int vm_swap_idle_enabled=0;
161 #endif
162
163 SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm,
164 CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt");
165
166 SYSCTL_INT(_vm, OID_AUTO, max_launder,
167 CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
168
169 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max,
170 CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length");
171
172 SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval,
173 CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan");
174
175 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval,
176 CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan");
177
178 SYSCTL_INT(_vm, OID_AUTO, pageout_stats_free_max,
179 CTLFLAG_RW, &vm_pageout_stats_free_max, 0, "Not implemented");
180
181 #if defined(NO_SWAPPING)
182 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
183 CTLFLAG_RD, &vm_swap_enabled, 0, "");
184 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
185 CTLFLAG_RD, &vm_swap_idle_enabled, 0, "");
186 #else
187 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
188 CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
189 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
190 CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
191 #endif
192
193 SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
194 CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
195
196 SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
197 CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
198
199 static int pageout_lock_miss;
200 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
201 CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
202
203 #define VM_PAGEOUT_PAGE_COUNT 16
204 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
205
206 int vm_page_max_wired; /* XXX max # of wired pages system-wide */
207
208 #if !defined(NO_SWAPPING)
209 static void vm_pageout_map_deactivate_pages(vm_map_t, long);
210 static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
211 static void vm_req_vmdaemon(void);
212 #endif
213 static void vm_pageout_page_stats(void);
214
215 /*
216 * vm_pageout_clean:
217 *
218 * Clean the page and remove it from the laundry.
219 *
220 * We set the busy bit to cause potential page faults on this page to
221 * block. Note the careful timing, however, the busy bit isn't set till
222 * late and we cannot do anything that will mess with the page.
223 */
224 static int
225 vm_pageout_clean(m)
226 vm_page_t m;
227 {
228 vm_object_t object;
229 vm_page_t mc[2*vm_pageout_page_count];
230 int pageout_count;
231 int ib, is, page_base;
232 vm_pindex_t pindex = m->pindex;
233
234 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
235 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
236
237 /*
238 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
239 * with the new swapper, but we could have serious problems paging
240 * out other object types if there is insufficient memory.
241 *
242 * Unfortunately, checking free memory here is far too late, so the
243 * check has been moved up a procedural level.
244 */
245
246 /*
247 * Don't mess with the page if it's busy, held, or special
248 */
249 if ((m->hold_count != 0) ||
250 ((m->busy != 0) || (m->flags & (PG_BUSY|PG_UNMANAGED)))) {
251 return 0;
252 }
253
254 mc[vm_pageout_page_count] = m;
255 pageout_count = 1;
256 page_base = vm_pageout_page_count;
257 ib = 1;
258 is = 1;
259
260 /*
261 * Scan object for clusterable pages.
262 *
263 * We can cluster ONLY if: ->> the page is NOT
264 * clean, wired, busy, held, or mapped into a
265 * buffer, and one of the following:
266 * 1) The page is inactive, or a seldom used
267 * active page.
268 * -or-
269 * 2) we force the issue.
270 *
271 * During heavy mmap/modification loads the pageout
272 * daemon can really fragment the underlying file
273 * due to flushing pages out of order and not trying
274 * align the clusters (which leave sporatic out-of-order
275 * holes). To solve this problem we do the reverse scan
276 * first and attempt to align our cluster, then do a
277 * forward scan if room remains.
278 */
279 object = m->object;
280 more:
281 while (ib && pageout_count < vm_pageout_page_count) {
282 vm_page_t p;
283
284 if (ib > pindex) {
285 ib = 0;
286 break;
287 }
288
289 if ((p = vm_page_lookup(object, pindex - ib)) == NULL) {
290 ib = 0;
291 break;
292 }
293 if (((p->queue - p->pc) == PQ_CACHE) ||
294 (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) {
295 ib = 0;
296 break;
297 }
298 vm_page_test_dirty(p);
299 if ((p->dirty & p->valid) == 0 ||
300 p->queue != PQ_INACTIVE ||
301 p->wire_count != 0 || /* may be held by buf cache */
302 p->hold_count != 0) { /* may be undergoing I/O */
303 ib = 0;
304 break;
305 }
306 mc[--page_base] = p;
307 ++pageout_count;
308 ++ib;
309 /*
310 * alignment boundry, stop here and switch directions. Do
311 * not clear ib.
312 */
313 if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
314 break;
315 }
316
317 while (pageout_count < vm_pageout_page_count &&
318 pindex + is < object->size) {
319 vm_page_t p;
320
321 if ((p = vm_page_lookup(object, pindex + is)) == NULL)
322 break;
323 if (((p->queue - p->pc) == PQ_CACHE) ||
324 (p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) {
325 break;
326 }
327 vm_page_test_dirty(p);
328 if ((p->dirty & p->valid) == 0 ||
329 p->queue != PQ_INACTIVE ||
330 p->wire_count != 0 || /* may be held by buf cache */
331 p->hold_count != 0) { /* may be undergoing I/O */
332 break;
333 }
334 mc[page_base + pageout_count] = p;
335 ++pageout_count;
336 ++is;
337 }
338
339 /*
340 * If we exhausted our forward scan, continue with the reverse scan
341 * when possible, even past a page boundry. This catches boundry
342 * conditions.
343 */
344 if (ib && pageout_count < vm_pageout_page_count)
345 goto more;
346
347 /*
348 * we allow reads during pageouts...
349 */
350 return (vm_pageout_flush(&mc[page_base], pageout_count, 0));
351 }
352
353 /*
354 * vm_pageout_flush() - launder the given pages
355 *
356 * The given pages are laundered. Note that we setup for the start of
357 * I/O ( i.e. busy the page ), mark it read-only, and bump the object
358 * reference count all in here rather then in the parent. If we want
359 * the parent to do more sophisticated things we may have to change
360 * the ordering.
361 */
362 int
363 vm_pageout_flush(vm_page_t *mc, int count, int flags)
364 {
365 vm_object_t object = mc[0]->object;
366 int pageout_status[count];
367 int numpagedout = 0;
368 int i;
369
370 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
371 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
372 /*
373 * Initiate I/O. Bump the vm_page_t->busy counter and
374 * mark the pages read-only.
375 *
376 * We do not have to fixup the clean/dirty bits here... we can
377 * allow the pager to do it after the I/O completes.
378 *
379 * NOTE! mc[i]->dirty may be partial or fragmented due to an
380 * edge case with file fragments.
381 */
382 for (i = 0; i < count; i++) {
383 KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
384 ("vm_pageout_flush: partially invalid page %p index %d/%d",
385 mc[i], i, count));
386 vm_page_io_start(mc[i]);
387 pmap_page_protect(mc[i], VM_PROT_READ);
388 }
389 vm_page_unlock_queues();
390 vm_object_pip_add(object, count);
391
392 vm_pager_put_pages(object, mc, count,
393 (flags | ((object == kernel_object) ? VM_PAGER_PUT_SYNC : 0)),
394 pageout_status);
395
396 vm_page_lock_queues();
397 for (i = 0; i < count; i++) {
398 vm_page_t mt = mc[i];
399
400 switch (pageout_status[i]) {
401 case VM_PAGER_OK:
402 case VM_PAGER_PEND:
403 numpagedout++;
404 break;
405 case VM_PAGER_BAD:
406 /*
407 * Page outside of range of object. Right now we
408 * essentially lose the changes by pretending it
409 * worked.
410 */
411 pmap_clear_modify(mt);
412 vm_page_undirty(mt);
413 break;
414 case VM_PAGER_ERROR:
415 case VM_PAGER_FAIL:
416 /*
417 * If page couldn't be paged out, then reactivate the
418 * page so it doesn't clog the inactive list. (We
419 * will try paging out it again later).
420 */
421 vm_page_activate(mt);
422 break;
423 case VM_PAGER_AGAIN:
424 break;
425 }
426
427 /*
428 * If the operation is still going, leave the page busy to
429 * block all other accesses. Also, leave the paging in
430 * progress indicator set so that we don't attempt an object
431 * collapse.
432 */
433 if (pageout_status[i] != VM_PAGER_PEND) {
434 vm_object_pip_wakeup(object);
435 vm_page_io_finish(mt);
436 if (!vm_page_count_severe() || !vm_page_try_to_cache(mt))
437 pmap_page_protect(mt, VM_PROT_READ);
438 }
439 }
440 return numpagedout;
441 }
442
443 #if !defined(NO_SWAPPING)
444 /*
445 * vm_pageout_object_deactivate_pages
446 *
447 * deactivate enough pages to satisfy the inactive target
448 * requirements or if vm_page_proc_limit is set, then
449 * deactivate all of the pages in the object and its
450 * backing_objects.
451 *
452 * The object and map must be locked.
453 */
454 static void
455 vm_pageout_object_deactivate_pages(pmap, first_object, desired)
456 pmap_t pmap;
457 vm_object_t first_object;
458 long desired;
459 {
460 vm_object_t backing_object, object;
461 vm_page_t p, next;
462 int actcount, rcount, remove_mode;
463
464 VM_OBJECT_LOCK_ASSERT(first_object, MA_OWNED);
465 if (first_object->type == OBJT_DEVICE || first_object->type == OBJT_PHYS)
466 return;
467 for (object = first_object;; object = backing_object) {
468 if (pmap_resident_count(pmap) <= desired)
469 goto unlock_return;
470 if (object->paging_in_progress)
471 goto unlock_return;
472
473 remove_mode = 0;
474 if (object->shadow_count > 1)
475 remove_mode = 1;
476 /*
477 * scan the objects entire memory queue
478 */
479 rcount = object->resident_page_count;
480 p = TAILQ_FIRST(&object->memq);
481 vm_page_lock_queues();
482 while (p && (rcount-- > 0)) {
483 if (pmap_resident_count(pmap) <= desired) {
484 vm_page_unlock_queues();
485 goto unlock_return;
486 }
487 next = TAILQ_NEXT(p, listq);
488 cnt.v_pdpages++;
489 if (p->wire_count != 0 ||
490 p->hold_count != 0 ||
491 p->busy != 0 ||
492 (p->flags & (PG_BUSY|PG_UNMANAGED)) ||
493 !pmap_page_exists_quick(pmap, p)) {
494 p = next;
495 continue;
496 }
497 actcount = pmap_ts_referenced(p);
498 if (actcount) {
499 vm_page_flag_set(p, PG_REFERENCED);
500 } else if (p->flags & PG_REFERENCED) {
501 actcount = 1;
502 }
503 if ((p->queue != PQ_ACTIVE) &&
504 (p->flags & PG_REFERENCED)) {
505 vm_page_activate(p);
506 p->act_count += actcount;
507 vm_page_flag_clear(p, PG_REFERENCED);
508 } else if (p->queue == PQ_ACTIVE) {
509 if ((p->flags & PG_REFERENCED) == 0) {
510 p->act_count -= min(p->act_count, ACT_DECLINE);
511 if (!remove_mode && (vm_pageout_algorithm || (p->act_count == 0))) {
512 pmap_remove_all(p);
513 vm_page_deactivate(p);
514 } else {
515 vm_pageq_requeue(p);
516 }
517 } else {
518 vm_page_activate(p);
519 vm_page_flag_clear(p, PG_REFERENCED);
520 if (p->act_count < (ACT_MAX - ACT_ADVANCE))
521 p->act_count += ACT_ADVANCE;
522 vm_pageq_requeue(p);
523 }
524 } else if (p->queue == PQ_INACTIVE) {
525 pmap_remove_all(p);
526 }
527 p = next;
528 }
529 vm_page_unlock_queues();
530 if ((backing_object = object->backing_object) == NULL)
531 goto unlock_return;
532 VM_OBJECT_LOCK(backing_object);
533 if (object != first_object)
534 VM_OBJECT_UNLOCK(object);
535 }
536 unlock_return:
537 if (object != first_object)
538 VM_OBJECT_UNLOCK(object);
539 }
540
541 /*
542 * deactivate some number of pages in a map, try to do it fairly, but
543 * that is really hard to do.
544 */
545 static void
546 vm_pageout_map_deactivate_pages(map, desired)
547 vm_map_t map;
548 long desired;
549 {
550 vm_map_entry_t tmpe;
551 vm_object_t obj, bigobj;
552 int nothingwired;
553
554 if (!vm_map_trylock(map))
555 return;
556
557 bigobj = NULL;
558 nothingwired = TRUE;
559
560 /*
561 * first, search out the biggest object, and try to free pages from
562 * that.
563 */
564 tmpe = map->header.next;
565 while (tmpe != &map->header) {
566 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
567 obj = tmpe->object.vm_object;
568 if (obj != NULL && VM_OBJECT_TRYLOCK(obj)) {
569 if (obj->shadow_count <= 1 &&
570 (bigobj == NULL ||
571 bigobj->resident_page_count < obj->resident_page_count)) {
572 if (bigobj != NULL)
573 VM_OBJECT_UNLOCK(bigobj);
574 bigobj = obj;
575 } else
576 VM_OBJECT_UNLOCK(obj);
577 }
578 }
579 if (tmpe->wired_count > 0)
580 nothingwired = FALSE;
581 tmpe = tmpe->next;
582 }
583
584 if (bigobj != NULL) {
585 vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
586 VM_OBJECT_UNLOCK(bigobj);
587 }
588 /*
589 * Next, hunt around for other pages to deactivate. We actually
590 * do this search sort of wrong -- .text first is not the best idea.
591 */
592 tmpe = map->header.next;
593 while (tmpe != &map->header) {
594 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
595 break;
596 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
597 obj = tmpe->object.vm_object;
598 if (obj != NULL) {
599 VM_OBJECT_LOCK(obj);
600 vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
601 VM_OBJECT_UNLOCK(obj);
602 }
603 }
604 tmpe = tmpe->next;
605 }
606
607 /*
608 * Remove all mappings if a process is swapped out, this will free page
609 * table pages.
610 */
611 if (desired == 0 && nothingwired) {
612 GIANT_REQUIRED;
613 vm_page_lock_queues();
614 pmap_remove(vm_map_pmap(map), vm_map_min(map),
615 vm_map_max(map));
616 vm_page_unlock_queues();
617 }
618 vm_map_unlock(map);
619 }
620 #endif /* !defined(NO_SWAPPING) */
621
622 /*
623 * This routine is very drastic, but can save the system
624 * in a pinch.
625 */
626 static void
627 vm_pageout_pmap_collect(void)
628 {
629 int i;
630 vm_page_t m;
631 static int warningdone;
632
633 if (pmap_pagedaemon_waken == 0)
634 return;
635 if (warningdone < 5) {
636 printf("collecting pv entries -- suggest increasing PMAP_SHPGPERPROC\n");
637 warningdone++;
638 }
639 vm_page_lock_queues();
640 for (i = 0; i < vm_page_array_size; i++) {
641 m = &vm_page_array[i];
642 if (m->wire_count || m->hold_count || m->busy ||
643 (m->flags & (PG_BUSY | PG_UNMANAGED)))
644 continue;
645 pmap_remove_all(m);
646 }
647 vm_page_unlock_queues();
648 pmap_pagedaemon_waken = 0;
649 }
650
651 /*
652 * vm_pageout_scan does the dirty work for the pageout daemon.
653 */
654 static void
655 vm_pageout_scan(int pass)
656 {
657 vm_page_t m, next;
658 struct vm_page marker;
659 int page_shortage, maxscan, pcount;
660 int addl_page_shortage, addl_page_shortage_init;
661 struct proc *p, *bigproc;
662 vm_offset_t size, bigsize;
663 vm_object_t object;
664 int actcount;
665 int vnodes_skipped = 0;
666 int maxlaunder;
667 int s;
668 struct thread *td;
669
670 mtx_lock(&Giant);
671 /*
672 * Decrease registered cache sizes.
673 */
674 EVENTHANDLER_INVOKE(vm_lowmem, 0);
675 /*
676 * We do this explicitly after the caches have been drained above.
677 */
678 uma_reclaim();
679 /*
680 * Do whatever cleanup that the pmap code can.
681 */
682 vm_pageout_pmap_collect();
683
684 addl_page_shortage_init = atomic_readandclear_int(&vm_pageout_deficit);
685
686 /*
687 * Calculate the number of pages we want to either free or move
688 * to the cache.
689 */
690 page_shortage = vm_paging_target() + addl_page_shortage_init;
691
692 /*
693 * Initialize our marker
694 */
695 bzero(&marker, sizeof(marker));
696 marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
697 marker.queue = PQ_INACTIVE;
698 marker.wire_count = 1;
699
700 /*
701 * Start scanning the inactive queue for pages we can move to the
702 * cache or free. The scan will stop when the target is reached or
703 * we have scanned the entire inactive queue. Note that m->act_count
704 * is not used to form decisions for the inactive queue, only for the
705 * active queue.
706 *
707 * maxlaunder limits the number of dirty pages we flush per scan.
708 * For most systems a smaller value (16 or 32) is more robust under
709 * extreme memory and disk pressure because any unnecessary writes
710 * to disk can result in extreme performance degredation. However,
711 * systems with excessive dirty pages (especially when MAP_NOSYNC is
712 * used) will die horribly with limited laundering. If the pageout
713 * daemon cannot clean enough pages in the first pass, we let it go
714 * all out in succeeding passes.
715 */
716 if ((maxlaunder = vm_max_launder) <= 1)
717 maxlaunder = 1;
718 if (pass)
719 maxlaunder = 10000;
720 vm_page_lock_queues();
721 rescan0:
722 addl_page_shortage = addl_page_shortage_init;
723 maxscan = cnt.v_inactive_count;
724
725 for (m = TAILQ_FIRST(&vm_page_queues[PQ_INACTIVE].pl);
726 m != NULL && maxscan-- > 0 && page_shortage > 0;
727 m = next) {
728
729 cnt.v_pdpages++;
730
731 if (m->queue != PQ_INACTIVE) {
732 goto rescan0;
733 }
734
735 next = TAILQ_NEXT(m, pageq);
736
737 /*
738 * skip marker pages
739 */
740 if (m->flags & PG_MARKER)
741 continue;
742
743 /*
744 * A held page may be undergoing I/O, so skip it.
745 */
746 if (m->hold_count) {
747 vm_pageq_requeue(m);
748 addl_page_shortage++;
749 continue;
750 }
751 /*
752 * Don't mess with busy pages, keep in the front of the
753 * queue, most likely are being paged out.
754 */
755 if (m->busy || (m->flags & PG_BUSY)) {
756 addl_page_shortage++;
757 continue;
758 }
759
760 /*
761 * If the object is not being used, we ignore previous
762 * references.
763 */
764 if (m->object->ref_count == 0) {
765 vm_page_flag_clear(m, PG_REFERENCED);
766 pmap_clear_reference(m);
767
768 /*
769 * Otherwise, if the page has been referenced while in the
770 * inactive queue, we bump the "activation count" upwards,
771 * making it less likely that the page will be added back to
772 * the inactive queue prematurely again. Here we check the
773 * page tables (or emulated bits, if any), given the upper
774 * level VM system not knowing anything about existing
775 * references.
776 */
777 } else if (((m->flags & PG_REFERENCED) == 0) &&
778 (actcount = pmap_ts_referenced(m))) {
779 vm_page_activate(m);
780 m->act_count += (actcount + ACT_ADVANCE);
781 continue;
782 }
783
784 /*
785 * If the upper level VM system knows about any page
786 * references, we activate the page. We also set the
787 * "activation count" higher than normal so that we will less
788 * likely place pages back onto the inactive queue again.
789 */
790 if ((m->flags & PG_REFERENCED) != 0) {
791 vm_page_flag_clear(m, PG_REFERENCED);
792 actcount = pmap_ts_referenced(m);
793 vm_page_activate(m);
794 m->act_count += (actcount + ACT_ADVANCE + 1);
795 continue;
796 }
797
798 /*
799 * If the upper level VM system doesn't know anything about
800 * the page being dirty, we have to check for it again. As
801 * far as the VM code knows, any partially dirty pages are
802 * fully dirty.
803 */
804 if (m->dirty == 0) {
805 vm_page_test_dirty(m);
806 } else {
807 vm_page_dirty(m);
808 }
809 object = m->object;
810 if (!VM_OBJECT_TRYLOCK(object))
811 continue;
812 if (m->valid == 0) {
813 /*
814 * Invalid pages can be easily freed
815 */
816 vm_page_busy(m);
817 pmap_remove_all(m);
818 vm_page_free(m);
819 cnt.v_dfree++;
820 --page_shortage;
821 } else if (m->dirty == 0) {
822 /*
823 * Clean pages can be placed onto the cache queue.
824 * This effectively frees them.
825 */
826 vm_page_cache(m);
827 --page_shortage;
828 } else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) {
829 /*
830 * Dirty pages need to be paged out, but flushing
831 * a page is extremely expensive verses freeing
832 * a clean page. Rather then artificially limiting
833 * the number of pages we can flush, we instead give
834 * dirty pages extra priority on the inactive queue
835 * by forcing them to be cycled through the queue
836 * twice before being flushed, after which the
837 * (now clean) page will cycle through once more
838 * before being freed. This significantly extends
839 * the thrash point for a heavily loaded machine.
840 */
841 vm_page_flag_set(m, PG_WINATCFLS);
842 vm_pageq_requeue(m);
843 } else if (maxlaunder > 0) {
844 /*
845 * We always want to try to flush some dirty pages if
846 * we encounter them, to keep the system stable.
847 * Normally this number is small, but under extreme
848 * pressure where there are insufficient clean pages
849 * on the inactive queue, we may have to go all out.
850 */
851 int swap_pageouts_ok;
852 struct vnode *vp = NULL;
853 struct mount *mp;
854
855 if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
856 swap_pageouts_ok = 1;
857 } else {
858 swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
859 swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
860 vm_page_count_min());
861
862 }
863
864 /*
865 * We don't bother paging objects that are "dead".
866 * Those objects are in a "rundown" state.
867 */
868 if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
869 VM_OBJECT_UNLOCK(object);
870 vm_pageq_requeue(m);
871 continue;
872 }
873
874 /*
875 * The object is already known NOT to be dead. It
876 * is possible for the vget() to block the whole
877 * pageout daemon, but the new low-memory handling
878 * code should prevent it.
879 *
880 * The previous code skipped locked vnodes and, worse,
881 * reordered pages in the queue. This results in
882 * completely non-deterministic operation and, on a
883 * busy system, can lead to extremely non-optimal
884 * pageouts. For example, it can cause clean pages
885 * to be freed and dirty pages to be moved to the end
886 * of the queue. Since dirty pages are also moved to
887 * the end of the queue once-cleaned, this gives
888 * way too large a weighting to defering the freeing
889 * of dirty pages.
890 *
891 * We can't wait forever for the vnode lock, we might
892 * deadlock due to a vn_read() getting stuck in
893 * vm_wait while holding this vnode. We skip the
894 * vnode if we can't get it in a reasonable amount
895 * of time.
896 */
897 if (object->type == OBJT_VNODE) {
898 vp = object->handle;
899 mp = NULL;
900 if (vp->v_type == VREG)
901 vn_start_write(vp, &mp, V_NOWAIT);
902 vm_page_unlock_queues();
903 VI_LOCK(vp);
904 VM_OBJECT_UNLOCK(object);
905 if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK |
906 LK_TIMELOCK, curthread)) {
907 VM_OBJECT_LOCK(object);
908 vm_page_lock_queues();
909 ++pageout_lock_miss;
910 vn_finished_write(mp);
911 if (object->flags & OBJ_MIGHTBEDIRTY)
912 vnodes_skipped++;
913 VM_OBJECT_UNLOCK(object);
914 continue;
915 }
916 VM_OBJECT_LOCK(object);
917 vm_page_lock_queues();
918 /*
919 * The page might have been moved to another
920 * queue during potential blocking in vget()
921 * above. The page might have been freed and
922 * reused for another vnode. The object might
923 * have been reused for another vnode.
924 */
925 if (m->queue != PQ_INACTIVE ||
926 m->object != object ||
927 object->handle != vp) {
928 if (object->flags & OBJ_MIGHTBEDIRTY)
929 vnodes_skipped++;
930 goto unlock_and_continue;
931 }
932
933 /*
934 * The page may have been busied during the
935 * blocking in vput(); We don't move the
936 * page back onto the end of the queue so that
937 * statistics are more correct if we don't.
938 */
939 if (m->busy || (m->flags & PG_BUSY)) {
940 goto unlock_and_continue;
941 }
942
943 /*
944 * If the page has become held it might
945 * be undergoing I/O, so skip it
946 */
947 if (m->hold_count) {
948 vm_pageq_requeue(m);
949 if (object->flags & OBJ_MIGHTBEDIRTY)
950 vnodes_skipped++;
951 goto unlock_and_continue;
952 }
953 }
954
955 /*
956 * If a page is dirty, then it is either being washed
957 * (but not yet cleaned) or it is still in the
958 * laundry. If it is still in the laundry, then we
959 * start the cleaning operation.
960 *
961 * This operation may cluster, invalidating the 'next'
962 * pointer. To prevent an inordinate number of
963 * restarts we use our marker to remember our place.
964 *
965 * decrement page_shortage on success to account for
966 * the (future) cleaned page. Otherwise we could wind
967 * up laundering or cleaning too many pages.
968 */
969 s = splvm();
970 TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE].pl, m, &marker, pageq);
971 splx(s);
972 if (vm_pageout_clean(m) != 0) {
973 --page_shortage;
974 --maxlaunder;
975 }
976 s = splvm();
977 next = TAILQ_NEXT(&marker, pageq);
978 TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, &marker, pageq);
979 splx(s);
980 unlock_and_continue:
981 VM_OBJECT_UNLOCK(object);
982 if (vp) {
983 vm_page_unlock_queues();
984 vput(vp);
985 vn_finished_write(mp);
986 vm_page_lock_queues();
987 }
988 continue;
989 }
990 VM_OBJECT_UNLOCK(object);
991 }
992
993 /*
994 * Compute the number of pages we want to try to move from the
995 * active queue to the inactive queue.
996 */
997 page_shortage = vm_paging_target() +
998 cnt.v_inactive_target - cnt.v_inactive_count;
999 page_shortage += addl_page_shortage;
1000
1001 /*
1002 * Scan the active queue for things we can deactivate. We nominally
1003 * track the per-page activity counter and use it to locate
1004 * deactivation candidates.
1005 */
1006 pcount = cnt.v_active_count;
1007 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
1008
1009 while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) {
1010
1011 KASSERT(m->queue == PQ_ACTIVE,
1012 ("vm_pageout_scan: page %p isn't active", m));
1013
1014 next = TAILQ_NEXT(m, pageq);
1015 /*
1016 * Don't deactivate pages that are busy.
1017 */
1018 if ((m->busy != 0) ||
1019 (m->flags & PG_BUSY) ||
1020 (m->hold_count != 0)) {
1021 vm_pageq_requeue(m);
1022 m = next;
1023 continue;
1024 }
1025
1026 /*
1027 * The count for pagedaemon pages is done after checking the
1028 * page for eligibility...
1029 */
1030 cnt.v_pdpages++;
1031
1032 /*
1033 * Check to see "how much" the page has been used.
1034 */
1035 actcount = 0;
1036 if (m->object->ref_count != 0) {
1037 if (m->flags & PG_REFERENCED) {
1038 actcount += 1;
1039 }
1040 actcount += pmap_ts_referenced(m);
1041 if (actcount) {
1042 m->act_count += ACT_ADVANCE + actcount;
1043 if (m->act_count > ACT_MAX)
1044 m->act_count = ACT_MAX;
1045 }
1046 }
1047
1048 /*
1049 * Since we have "tested" this bit, we need to clear it now.
1050 */
1051 vm_page_flag_clear(m, PG_REFERENCED);
1052
1053 /*
1054 * Only if an object is currently being used, do we use the
1055 * page activation count stats.
1056 */
1057 if (actcount && (m->object->ref_count != 0)) {
1058 vm_pageq_requeue(m);
1059 } else {
1060 m->act_count -= min(m->act_count, ACT_DECLINE);
1061 if (vm_pageout_algorithm ||
1062 m->object->ref_count == 0 ||
1063 m->act_count == 0) {
1064 page_shortage--;
1065 if (m->object->ref_count == 0) {
1066 pmap_remove_all(m);
1067 if (m->dirty == 0)
1068 vm_page_cache(m);
1069 else
1070 vm_page_deactivate(m);
1071 } else {
1072 vm_page_deactivate(m);
1073 }
1074 } else {
1075 vm_pageq_requeue(m);
1076 }
1077 }
1078 m = next;
1079 }
1080 s = splvm();
1081
1082 /*
1083 * We try to maintain some *really* free pages, this allows interrupt
1084 * code to be guaranteed space. Since both cache and free queues
1085 * are considered basically 'free', moving pages from cache to free
1086 * does not effect other calculations.
1087 */
1088 while (cnt.v_free_count < cnt.v_free_reserved) {
1089 static int cache_rover = 0;
1090
1091 if ((m = vm_page_select_cache(cache_rover)) == NULL)
1092 break;
1093 cache_rover = (m->pc + PQ_PRIME2) & PQ_L2_MASK;
1094 object = m->object;
1095 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
1096 vm_page_busy(m);
1097 pmap_remove_all(m);
1098 vm_page_free(m);
1099 VM_OBJECT_UNLOCK(object);
1100 cnt.v_dfree++;
1101 }
1102 splx(s);
1103 vm_page_unlock_queues();
1104 #if !defined(NO_SWAPPING)
1105 /*
1106 * Idle process swapout -- run once per second.
1107 */
1108 if (vm_swap_idle_enabled) {
1109 static long lsec;
1110 if (time_second != lsec) {
1111 vm_pageout_req_swapout |= VM_SWAP_IDLE;
1112 vm_req_vmdaemon();
1113 lsec = time_second;
1114 }
1115 }
1116 #endif
1117
1118 /*
1119 * If we didn't get enough free pages, and we have skipped a vnode
1120 * in a writeable object, wakeup the sync daemon. And kick swapout
1121 * if we did not get enough free pages.
1122 */
1123 if (vm_paging_target() > 0) {
1124 if (vnodes_skipped && vm_page_count_min())
1125 (void) speedup_syncer();
1126 #if !defined(NO_SWAPPING)
1127 if (vm_swap_enabled && vm_page_count_target()) {
1128 vm_req_vmdaemon();
1129 vm_pageout_req_swapout |= VM_SWAP_NORMAL;
1130 }
1131 #endif
1132 }
1133
1134 /*
1135 * If we are critically low on one of RAM or swap and low on
1136 * the other, kill the largest process. However, we avoid
1137 * doing this on the first pass in order to give ourselves a
1138 * chance to flush out dirty vnode-backed pages and to allow
1139 * active pages to be moved to the inactive queue and reclaimed.
1140 *
1141 * We keep the process bigproc locked once we find it to keep anyone
1142 * from messing with it; however, there is a possibility of
1143 * deadlock if process B is bigproc and one of it's child processes
1144 * attempts to propagate a signal to B while we are waiting for A's
1145 * lock while walking this list. To avoid this, we don't block on
1146 * the process lock but just skip a process if it is already locked.
1147 */
1148 if (pass != 0 &&
1149 ((swap_pager_avail < 64 && vm_page_count_min()) ||
1150 (swap_pager_full && vm_paging_target() > 0))) {
1151 bigproc = NULL;
1152 bigsize = 0;
1153 sx_slock(&allproc_lock);
1154 FOREACH_PROC_IN_SYSTEM(p) {
1155 int breakout;
1156 /*
1157 * If this process is already locked, skip it.
1158 */
1159 if (PROC_TRYLOCK(p) == 0)
1160 continue;
1161 /*
1162 * If this is a system or protected process, skip it.
1163 */
1164 if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) ||
1165 (p->p_flag & P_PROTECTED) ||
1166 ((p->p_pid < 48) && (swap_pager_avail != 0))) {
1167 PROC_UNLOCK(p);
1168 continue;
1169 }
1170 /*
1171 * if the process is in a non-running type state,
1172 * don't touch it. Check all the threads individually.
1173 */
1174 mtx_lock_spin(&sched_lock);
1175 breakout = 0;
1176 FOREACH_THREAD_IN_PROC(p, td) {
1177 if (!TD_ON_RUNQ(td) &&
1178 !TD_IS_RUNNING(td) &&
1179 !TD_IS_SLEEPING(td)) {
1180 breakout = 1;
1181 break;
1182 }
1183 }
1184 if (breakout) {
1185 mtx_unlock_spin(&sched_lock);
1186 PROC_UNLOCK(p);
1187 continue;
1188 }
1189 mtx_unlock_spin(&sched_lock);
1190 /*
1191 * get the process size
1192 */
1193 if (!vm_map_trylock_read(&p->p_vmspace->vm_map)) {
1194 PROC_UNLOCK(p);
1195 continue;
1196 }
1197 size = vmspace_swap_count(p->p_vmspace);
1198 vm_map_unlock_read(&p->p_vmspace->vm_map);
1199 size += vmspace_resident_count(p->p_vmspace);
1200 /*
1201 * if the this process is bigger than the biggest one
1202 * remember it.
1203 */
1204 if (size > bigsize) {
1205 if (bigproc != NULL)
1206 PROC_UNLOCK(bigproc);
1207 bigproc = p;
1208 bigsize = size;
1209 } else
1210 PROC_UNLOCK(p);
1211 }
1212 sx_sunlock(&allproc_lock);
1213 if (bigproc != NULL) {
1214 struct ksegrp *kg;
1215 killproc(bigproc, "out of swap space");
1216 mtx_lock_spin(&sched_lock);
1217 FOREACH_KSEGRP_IN_PROC(bigproc, kg) {
1218 sched_nice(kg, PRIO_MIN); /* XXXKSE ??? */
1219 }
1220 mtx_unlock_spin(&sched_lock);
1221 PROC_UNLOCK(bigproc);
1222 wakeup(&cnt.v_free_count);
1223 }
1224 }
1225 mtx_unlock(&Giant);
1226 }
1227
1228 /*
1229 * This routine tries to maintain the pseudo LRU active queue,
1230 * so that during long periods of time where there is no paging,
1231 * that some statistic accumulation still occurs. This code
1232 * helps the situation where paging just starts to occur.
1233 */
1234 static void
1235 vm_pageout_page_stats()
1236 {
1237 vm_page_t m,next;
1238 int pcount,tpcount; /* Number of pages to check */
1239 static int fullintervalcount = 0;
1240 int page_shortage;
1241 int s0;
1242
1243 page_shortage =
1244 (cnt.v_inactive_target + cnt.v_cache_max + cnt.v_free_min) -
1245 (cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
1246
1247 if (page_shortage <= 0)
1248 return;
1249
1250 s0 = splvm();
1251 vm_page_lock_queues();
1252 pcount = cnt.v_active_count;
1253 fullintervalcount += vm_pageout_stats_interval;
1254 if (fullintervalcount < vm_pageout_full_stats_interval) {
1255 tpcount = (vm_pageout_stats_max * cnt.v_active_count) / cnt.v_page_count;
1256 if (pcount > tpcount)
1257 pcount = tpcount;
1258 } else {
1259 fullintervalcount = 0;
1260 }
1261
1262 m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
1263 while ((m != NULL) && (pcount-- > 0)) {
1264 int actcount;
1265
1266 KASSERT(m->queue == PQ_ACTIVE,
1267 ("vm_pageout_page_stats: page %p isn't active", m));
1268
1269 next = TAILQ_NEXT(m, pageq);
1270 /*
1271 * Don't deactivate pages that are busy.
1272 */
1273 if ((m->busy != 0) ||
1274 (m->flags & PG_BUSY) ||
1275 (m->hold_count != 0)) {
1276 vm_pageq_requeue(m);
1277 m = next;
1278 continue;
1279 }
1280
1281 actcount = 0;
1282 if (m->flags & PG_REFERENCED) {
1283 vm_page_flag_clear(m, PG_REFERENCED);
1284 actcount += 1;
1285 }
1286
1287 actcount += pmap_ts_referenced(m);
1288 if (actcount) {
1289 m->act_count += ACT_ADVANCE + actcount;
1290 if (m->act_count > ACT_MAX)
1291 m->act_count = ACT_MAX;
1292 vm_pageq_requeue(m);
1293 } else {
1294 if (m->act_count == 0) {
1295 /*
1296 * We turn off page access, so that we have
1297 * more accurate RSS stats. We don't do this
1298 * in the normal page deactivation when the
1299 * system is loaded VM wise, because the
1300 * cost of the large number of page protect
1301 * operations would be higher than the value
1302 * of doing the operation.
1303 */
1304 pmap_remove_all(m);
1305 vm_page_deactivate(m);
1306 } else {
1307 m->act_count -= min(m->act_count, ACT_DECLINE);
1308 vm_pageq_requeue(m);
1309 }
1310 }
1311
1312 m = next;
1313 }
1314 vm_page_unlock_queues();
1315 splx(s0);
1316 }
1317
1318 /*
1319 * vm_pageout is the high level pageout daemon.
1320 */
1321 static void
1322 vm_pageout()
1323 {
1324 int error, pass, s;
1325
1326 /*
1327 * Initialize some paging parameters.
1328 */
1329 cnt.v_interrupt_free_min = 2;
1330 if (cnt.v_page_count < 2000)
1331 vm_pageout_page_count = 8;
1332
1333 /*
1334 * v_free_reserved needs to include enough for the largest
1335 * swap pager structures plus enough for any pv_entry structs
1336 * when paging.
1337 */
1338 if (cnt.v_page_count > 1024)
1339 cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
1340 else
1341 cnt.v_free_min = 4;
1342 cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
1343 cnt.v_interrupt_free_min;
1344 cnt.v_free_reserved = vm_pageout_page_count +
1345 cnt.v_pageout_free_min + (cnt.v_page_count / 768) + PQ_L2_SIZE;
1346 cnt.v_free_severe = cnt.v_free_min / 2;
1347 cnt.v_free_min += cnt.v_free_reserved;
1348 cnt.v_free_severe += cnt.v_free_reserved;
1349
1350 /*
1351 * v_free_target and v_cache_min control pageout hysteresis. Note
1352 * that these are more a measure of the VM cache queue hysteresis
1353 * then the VM free queue. Specifically, v_free_target is the
1354 * high water mark (free+cache pages).
1355 *
1356 * v_free_reserved + v_cache_min (mostly means v_cache_min) is the
1357 * low water mark, while v_free_min is the stop. v_cache_min must
1358 * be big enough to handle memory needs while the pageout daemon
1359 * is signalled and run to free more pages.
1360 */
1361 if (cnt.v_free_count > 6144)
1362 cnt.v_free_target = 4 * cnt.v_free_min + cnt.v_free_reserved;
1363 else
1364 cnt.v_free_target = 2 * cnt.v_free_min + cnt.v_free_reserved;
1365
1366 if (cnt.v_free_count > 2048) {
1367 cnt.v_cache_min = cnt.v_free_target;
1368 cnt.v_cache_max = 2 * cnt.v_cache_min;
1369 cnt.v_inactive_target = (3 * cnt.v_free_target) / 2;
1370 } else {
1371 cnt.v_cache_min = 0;
1372 cnt.v_cache_max = 0;
1373 cnt.v_inactive_target = cnt.v_free_count / 4;
1374 }
1375 if (cnt.v_inactive_target > cnt.v_free_count / 3)
1376 cnt.v_inactive_target = cnt.v_free_count / 3;
1377
1378 /* XXX does not really belong here */
1379 if (vm_page_max_wired == 0)
1380 vm_page_max_wired = cnt.v_free_count / 3;
1381
1382 if (vm_pageout_stats_max == 0)
1383 vm_pageout_stats_max = cnt.v_free_target;
1384
1385 /*
1386 * Set interval in seconds for stats scan.
1387 */
1388 if (vm_pageout_stats_interval == 0)
1389 vm_pageout_stats_interval = 5;
1390 if (vm_pageout_full_stats_interval == 0)
1391 vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
1392
1393 /*
1394 * Set maximum free per pass
1395 */
1396 if (vm_pageout_stats_free_max == 0)
1397 vm_pageout_stats_free_max = 5;
1398
1399 swap_pager_swap_init();
1400 pass = 0;
1401 /*
1402 * The pageout daemon is never done, so loop forever.
1403 */
1404 while (TRUE) {
1405 s = splvm();
1406 vm_page_lock_queues();
1407 /*
1408 * If we have enough free memory, wakeup waiters. Do
1409 * not clear vm_pages_needed until we reach our target,
1410 * otherwise we may be woken up over and over again and
1411 * waste a lot of cpu.
1412 */
1413 if (vm_pages_needed && !vm_page_count_min()) {
1414 if (!vm_paging_needed())
1415 vm_pages_needed = 0;
1416 wakeup(&cnt.v_free_count);
1417 }
1418 if (vm_pages_needed) {
1419 /*
1420 * Still not done, take a second pass without waiting
1421 * (unlimited dirty cleaning), otherwise sleep a bit
1422 * and try again.
1423 */
1424 ++pass;
1425 if (pass > 1)
1426 msleep(&vm_pages_needed, &vm_page_queue_mtx, PVM,
1427 "psleep", hz/2);
1428 } else {
1429 /*
1430 * Good enough, sleep & handle stats. Prime the pass
1431 * for the next run.
1432 */
1433 if (pass > 1)
1434 pass = 1;
1435 else
1436 pass = 0;
1437 error = msleep(&vm_pages_needed, &vm_page_queue_mtx, PVM,
1438 "psleep", vm_pageout_stats_interval * hz);
1439 if (error && !vm_pages_needed) {
1440 vm_page_unlock_queues();
1441 splx(s);
1442 pass = 0;
1443 vm_pageout_page_stats();
1444 continue;
1445 }
1446 }
1447 if (vm_pages_needed)
1448 cnt.v_pdwakeups++;
1449 vm_page_unlock_queues();
1450 splx(s);
1451 vm_pageout_scan(pass);
1452 }
1453 }
1454
1455 /*
1456 * Unless the page queue lock is held by the caller, this function
1457 * should be regarded as advisory. Specifically, the caller should
1458 * not msleep() on &cnt.v_free_count following this function unless
1459 * the page queue lock is held until the msleep() is performed.
1460 */
1461 void
1462 pagedaemon_wakeup()
1463 {
1464
1465 if (!vm_pages_needed && curthread->td_proc != pageproc) {
1466 vm_pages_needed = 1;
1467 wakeup(&vm_pages_needed);
1468 }
1469 }
1470
1471 #if !defined(NO_SWAPPING)
1472 static void
1473 vm_req_vmdaemon()
1474 {
1475 static int lastrun = 0;
1476
1477 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
1478 wakeup(&vm_daemon_needed);
1479 lastrun = ticks;
1480 }
1481 }
1482
1483 static void
1484 vm_daemon()
1485 {
1486 struct proc *p;
1487 int breakout;
1488 struct thread *td;
1489
1490 mtx_lock(&Giant);
1491 while (TRUE) {
1492 tsleep(&vm_daemon_needed, PPAUSE, "psleep", 0);
1493 if (vm_pageout_req_swapout) {
1494 swapout_procs(vm_pageout_req_swapout);
1495 vm_pageout_req_swapout = 0;
1496 }
1497 /*
1498 * scan the processes for exceeding their rlimits or if
1499 * process is swapped out -- deactivate pages
1500 */
1501 sx_slock(&allproc_lock);
1502 LIST_FOREACH(p, &allproc, p_list) {
1503 vm_pindex_t limit, size;
1504
1505 /*
1506 * if this is a system process or if we have already
1507 * looked at this process, skip it.
1508 */
1509 PROC_LOCK(p);
1510 if (p->p_flag & (P_SYSTEM | P_WEXIT)) {
1511 PROC_UNLOCK(p);
1512 continue;
1513 }
1514 /*
1515 * if the process is in a non-running type state,
1516 * don't touch it.
1517 */
1518 mtx_lock_spin(&sched_lock);
1519 breakout = 0;
1520 FOREACH_THREAD_IN_PROC(p, td) {
1521 if (!TD_ON_RUNQ(td) &&
1522 !TD_IS_RUNNING(td) &&
1523 !TD_IS_SLEEPING(td)) {
1524 breakout = 1;
1525 break;
1526 }
1527 }
1528 mtx_unlock_spin(&sched_lock);
1529 if (breakout) {
1530 PROC_UNLOCK(p);
1531 continue;
1532 }
1533 /*
1534 * get a limit
1535 */
1536 limit = OFF_TO_IDX(
1537 qmin(p->p_rlimit[RLIMIT_RSS].rlim_cur,
1538 p->p_rlimit[RLIMIT_RSS].rlim_max));
1539
1540 /*
1541 * let processes that are swapped out really be
1542 * swapped out set the limit to nothing (will force a
1543 * swap-out.)
1544 */
1545 if ((p->p_sflag & PS_INMEM) == 0)
1546 limit = 0; /* XXX */
1547 PROC_UNLOCK(p);
1548
1549 size = vmspace_resident_count(p->p_vmspace);
1550 if (limit >= 0 && size >= limit) {
1551 vm_pageout_map_deactivate_pages(
1552 &p->p_vmspace->vm_map, limit);
1553 }
1554 }
1555 sx_sunlock(&allproc_lock);
1556 }
1557 }
1558 #endif /* !defined(NO_SWAPPING) */
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