uvm_pdaemon.c revision 1.37 1 /* $NetBSD: uvm_pdaemon.c,v 1.37 2001/09/15 20:36:47 chs Exp $ */
2
3 /*
4 * Copyright (c) 1997 Charles D. Cranor and Washington University.
5 * Copyright (c) 1991, 1993, The Regents of the University of California.
6 *
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 Charles D. Cranor,
23 * Washington University, the University of California, Berkeley and
24 * its contributors.
25 * 4. Neither the name of the University nor the names of its contributors
26 * may be used to endorse or promote products derived from this software
27 * without specific prior written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
39 * SUCH DAMAGE.
40 *
41 * @(#)vm_pageout.c 8.5 (Berkeley) 2/14/94
42 * from: Id: uvm_pdaemon.c,v 1.1.2.32 1998/02/06 05:26:30 chs Exp
43 *
44 *
45 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
46 * All rights reserved.
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 (at) 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 #include "opt_uvmhist.h"
70
71 /*
72 * uvm_pdaemon.c: the page daemon
73 */
74
75 #include <sys/param.h>
76 #include <sys/proc.h>
77 #include <sys/systm.h>
78 #include <sys/kernel.h>
79 #include <sys/pool.h>
80 #include <sys/buf.h>
81 #include <sys/vnode.h>
82
83 #include <uvm/uvm.h>
84
85 /*
86 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedeamon will reactivate
87 * in a pass thru the inactive list when swap is full. the value should be
88 * "small"... if it's too large we'll cycle the active pages thru the inactive
89 * queue too quickly to for them to be referenced and avoid being freed.
90 */
91
92 #define UVMPD_NUMDIRTYREACTS 16
93
94
95 /*
96 * local prototypes
97 */
98
99 void uvmpd_scan __P((void));
100 boolean_t uvmpd_scan_inactive __P((struct pglist *));
101 void uvmpd_tune __P((void));
102
103 /*
104 * uvm_wait: wait (sleep) for the page daemon to free some pages
105 *
106 * => should be called with all locks released
107 * => should _not_ be called by the page daemon (to avoid deadlock)
108 */
109
110 void
111 uvm_wait(wmsg)
112 const char *wmsg;
113 {
114 int timo = 0;
115 int s = splbio();
116
117 /*
118 * check for page daemon going to sleep (waiting for itself)
119 */
120
121 if (curproc == uvm.pagedaemon_proc && uvmexp.paging == 0) {
122 /*
123 * now we have a problem: the pagedaemon wants to go to
124 * sleep until it frees more memory. but how can it
125 * free more memory if it is asleep? that is a deadlock.
126 * we have two options:
127 * [1] panic now
128 * [2] put a timeout on the sleep, thus causing the
129 * pagedaemon to only pause (rather than sleep forever)
130 *
131 * note that option [2] will only help us if we get lucky
132 * and some other process on the system breaks the deadlock
133 * by exiting or freeing memory (thus allowing the pagedaemon
134 * to continue). for now we panic if DEBUG is defined,
135 * otherwise we hope for the best with option [2] (better
136 * yet, this should never happen in the first place!).
137 */
138
139 printf("pagedaemon: deadlock detected!\n");
140 timo = hz >> 3; /* set timeout */
141 #if defined(DEBUG)
142 /* DEBUG: panic so we can debug it */
143 panic("pagedaemon deadlock");
144 #endif
145 }
146
147 simple_lock(&uvm.pagedaemon_lock);
148 wakeup(&uvm.pagedaemon); /* wake the daemon! */
149 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm.pagedaemon_lock, FALSE, wmsg,
150 timo);
151
152 splx(s);
153 }
154
155
156 /*
157 * uvmpd_tune: tune paging parameters
158 *
159 * => called when ever memory is added (or removed?) to the system
160 * => caller must call with page queues locked
161 */
162
163 void
164 uvmpd_tune(void)
165 {
166 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist);
167
168 uvmexp.freemin = uvmexp.npages / 20;
169
170 /* between 16k and 256k */
171 /* XXX: what are these values good for? */
172 uvmexp.freemin = MAX(uvmexp.freemin, (16*1024) >> PAGE_SHIFT);
173 uvmexp.freemin = MIN(uvmexp.freemin, (256*1024) >> PAGE_SHIFT);
174
175 /* Make sure there's always a user page free. */
176 if (uvmexp.freemin < uvmexp.reserve_kernel + 1)
177 uvmexp.freemin = uvmexp.reserve_kernel + 1;
178
179 uvmexp.freetarg = (uvmexp.freemin * 4) / 3;
180 if (uvmexp.freetarg <= uvmexp.freemin)
181 uvmexp.freetarg = uvmexp.freemin + 1;
182
183 /* uvmexp.inactarg: computed in main daemon loop */
184
185 uvmexp.wiredmax = uvmexp.npages / 3;
186 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d",
187 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0);
188 }
189
190 /*
191 * uvm_pageout: the main loop for the pagedaemon
192 */
193
194 void
195 uvm_pageout(void *arg)
196 {
197 int npages = 0;
198 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist);
199
200 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0);
201
202 /*
203 * ensure correct priority and set paging parameters...
204 */
205
206 uvm.pagedaemon_proc = curproc;
207 uvm_lock_pageq();
208 npages = uvmexp.npages;
209 uvmpd_tune();
210 uvm_unlock_pageq();
211
212 /*
213 * main loop
214 */
215
216 for (;;) {
217 simple_lock(&uvm.pagedaemon_lock);
218
219 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0);
220 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon,
221 &uvm.pagedaemon_lock, FALSE, "pgdaemon", 0);
222 uvmexp.pdwoke++;
223 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0);
224
225 /* drain pool resources */
226 pool_drain(0);
227
228 /*
229 * now lock page queues and recompute inactive count
230 */
231
232 uvm_lock_pageq();
233 if (npages != uvmexp.npages) { /* check for new pages? */
234 npages = uvmexp.npages;
235 uvmpd_tune();
236 }
237
238 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3;
239 if (uvmexp.inactarg <= uvmexp.freetarg) {
240 uvmexp.inactarg = uvmexp.freetarg + 1;
241 }
242
243 UVMHIST_LOG(pdhist," free/ftarg=%d/%d, inact/itarg=%d/%d",
244 uvmexp.free, uvmexp.freetarg, uvmexp.inactive,
245 uvmexp.inactarg);
246
247 /*
248 * scan if needed
249 */
250
251 if (uvmexp.free + uvmexp.paging < uvmexp.freetarg ||
252 uvmexp.inactive < uvmexp.inactarg) {
253 uvmpd_scan();
254 }
255
256 /*
257 * if there's any free memory to be had,
258 * wake up any waiters.
259 */
260
261 if (uvmexp.free > uvmexp.reserve_kernel ||
262 uvmexp.paging == 0) {
263 wakeup(&uvmexp.free);
264 }
265
266 /*
267 * scan done. unlock page queues (the only lock we are holding)
268 */
269
270 uvm_unlock_pageq();
271 }
272 /*NOTREACHED*/
273 }
274
275
276 /*
277 * uvm_aiodone_daemon: main loop for the aiodone daemon.
278 */
279
280 void
281 uvm_aiodone_daemon(void *arg)
282 {
283 int s, free;
284 struct buf *bp, *nbp;
285 UVMHIST_FUNC("uvm_aiodoned"); UVMHIST_CALLED(pdhist);
286
287 for (;;) {
288
289 /*
290 * carefully attempt to go to sleep (without losing "wakeups"!).
291 * we need splbio because we want to make sure the aio_done list
292 * is totally empty before we go to sleep.
293 */
294
295 s = splbio();
296 simple_lock(&uvm.aiodoned_lock);
297 if (TAILQ_FIRST(&uvm.aio_done) == NULL) {
298 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0);
299 UVM_UNLOCK_AND_WAIT(&uvm.aiodoned,
300 &uvm.aiodoned_lock, FALSE, "aiodoned", 0);
301 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0);
302
303 /* relock aiodoned_lock, still at splbio */
304 simple_lock(&uvm.aiodoned_lock);
305 }
306
307 /*
308 * check for done aio structures
309 */
310
311 bp = TAILQ_FIRST(&uvm.aio_done);
312 if (bp) {
313 TAILQ_INIT(&uvm.aio_done);
314 }
315
316 simple_unlock(&uvm.aiodoned_lock);
317 splx(s);
318
319 /*
320 * process each i/o that's done.
321 */
322
323 free = uvmexp.free;
324 while (bp != NULL) {
325 nbp = TAILQ_NEXT(bp, b_freelist);
326 (*bp->b_iodone)(bp);
327 bp = nbp;
328 }
329 if (free <= uvmexp.reserve_kernel) {
330 s = uvm_lock_fpageq();
331 wakeup(&uvm.pagedaemon);
332 uvm_unlock_fpageq(s);
333 } else {
334 simple_lock(&uvm.pagedaemon_lock);
335 wakeup(&uvmexp.free);
336 simple_unlock(&uvm.pagedaemon_lock);
337 }
338 }
339 }
340
341 /*
342 * uvmpd_scan_inactive: scan an inactive list for pages to clean or free.
343 *
344 * => called with page queues locked
345 * => we work on meeting our free target by converting inactive pages
346 * into free pages.
347 * => we handle the building of swap-backed clusters
348 * => we return TRUE if we are exiting because we met our target
349 */
350
351 boolean_t
352 uvmpd_scan_inactive(pglst)
353 struct pglist *pglst;
354 {
355 boolean_t retval = FALSE; /* assume we haven't hit target */
356 int error;
357 struct vm_page *p, *nextpg;
358 struct uvm_object *uobj;
359 struct vm_anon *anon;
360 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT];
361 struct simplelock *slock;
362 int swnpages, swcpages;
363 int swslot;
364 int dirtyreacts, t, result;
365 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist);
366
367 /*
368 * swslot is non-zero if we are building a swap cluster. we want
369 * to stay in the loop while we have a page to scan or we have
370 * a swap-cluster to build.
371 */
372
373 swslot = 0;
374 swnpages = swcpages = 0;
375 dirtyreacts = 0;
376 for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) {
377 uobj = NULL;
378 anon = NULL;
379 if (p) {
380
381 /*
382 * see if we've met the free target.
383 */
384
385 if (uvmexp.free + uvmexp.paging >=
386 uvmexp.freetarg << 2 ||
387 dirtyreacts == UVMPD_NUMDIRTYREACTS) {
388 UVMHIST_LOG(pdhist," met free target: "
389 "exit loop", 0, 0, 0, 0);
390 retval = TRUE;
391
392 if (swslot == 0) {
393 /* exit now if no swap-i/o pending */
394 break;
395 }
396
397 /* set p to null to signal final swap i/o */
398 p = NULL;
399 nextpg = NULL;
400 }
401 }
402 if (p) { /* if (we have a new page to consider) */
403
404 /*
405 * we are below target and have a new page to consider.
406 */
407
408 uvmexp.pdscans++;
409 nextpg = TAILQ_NEXT(p, pageq);
410
411 /*
412 * move referenced pages back to active queue and
413 * skip to next page.
414 */
415
416 if (pmap_clear_reference(p)) {
417 uvm_pageactivate(p);
418 uvmexp.pdreact++;
419 continue;
420 }
421 anon = p->uanon;
422 uobj = p->uobject;
423
424 /*
425 * enforce the minimum thresholds on different
426 * types of memory usage. if reusing the current
427 * page would reduce that type of usage below its
428 * minimum, reactivate the page instead and move
429 * on to the next page.
430 */
431
432 t = uvmexp.active + uvmexp.inactive + uvmexp.free;
433 if (anon &&
434 uvmexp.anonpages <= (t * uvmexp.anonmin) >> 8) {
435 uvm_pageactivate(p);
436 uvmexp.pdreanon++;
437 continue;
438 }
439 if (uobj && UVM_OBJ_IS_VTEXT(uobj) &&
440 uvmexp.vtextpages <= (t * uvmexp.vtextmin) >> 8) {
441 uvm_pageactivate(p);
442 uvmexp.pdrevtext++;
443 continue;
444 }
445 if (uobj && UVM_OBJ_IS_VNODE(uobj) &&
446 !UVM_OBJ_IS_VTEXT(uobj) &&
447 uvmexp.vnodepages <= (t * uvmexp.vnodemin) >> 8) {
448 uvm_pageactivate(p);
449 uvmexp.pdrevnode++;
450 continue;
451 }
452
453 /*
454 * first we attempt to lock the object that this page
455 * belongs to. if our attempt fails we skip on to
456 * the next page (no harm done). it is important to
457 * "try" locking the object as we are locking in the
458 * wrong order (pageq -> object) and we don't want to
459 * deadlock.
460 *
461 * the only time we expect to see an ownerless page
462 * (i.e. a page with no uobject and !PQ_ANON) is if an
463 * anon has loaned a page from a uvm_object and the
464 * uvm_object has dropped the ownership. in that
465 * case, the anon can "take over" the loaned page
466 * and make it its own.
467 */
468
469 /* is page part of an anon or ownerless ? */
470 if ((p->pqflags & PQ_ANON) || uobj == NULL) {
471 KASSERT(anon != NULL);
472 slock = &anon->an_lock;
473 if (!simple_lock_try(slock)) {
474 /* lock failed, skip this page */
475 continue;
476 }
477
478 /*
479 * if the page is ownerless, claim it in the
480 * name of "anon"!
481 */
482
483 if ((p->pqflags & PQ_ANON) == 0) {
484 KASSERT(p->loan_count > 0);
485 p->loan_count--;
486 p->pqflags |= PQ_ANON;
487 /* anon now owns it */
488 }
489 if (p->flags & PG_BUSY) {
490 simple_unlock(slock);
491 uvmexp.pdbusy++;
492 continue;
493 }
494 uvmexp.pdanscan++;
495 } else {
496 KASSERT(uobj != NULL);
497 slock = &uobj->vmobjlock;
498 if (!simple_lock_try(slock)) {
499 continue;
500 }
501 if (p->flags & PG_BUSY) {
502 simple_unlock(slock);
503 uvmexp.pdbusy++;
504 continue;
505 }
506 uvmexp.pdobscan++;
507 }
508
509
510 /*
511 * we now have the object and the page queues locked.
512 * if the page is not swap-backed, call the object's
513 * pager to flush and free the page.
514 */
515
516 if ((p->pqflags & PQ_SWAPBACKED) == 0) {
517 uvm_unlock_pageq();
518 error = (uobj->pgops->pgo_put)(uobj, p->offset,
519 p->offset + PAGE_SIZE,
520 PGO_CLEANIT|PGO_FREE);
521 uvm_lock_pageq();
522 if (nextpg &&
523 (nextpg->flags & PQ_INACTIVE) == 0) {
524 nextpg = TAILQ_FIRST(pglst);
525 }
526 continue;
527 }
528
529 /*
530 * the page is swap-backed. remove all the permissions
531 * from the page so we can sync the modified info
532 * without any race conditions. if the page is clean
533 * we can free it now and continue.
534 */
535
536 pmap_page_protect(p, VM_PROT_NONE);
537 if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) {
538 p->flags &= ~(PG_CLEAN);
539 }
540 if (p->flags & PG_CLEAN) {
541 uvm_pagefree(p);
542 uvmexp.pdfreed++;
543
544 /*
545 * for anons, we need to remove the page
546 * from the anon ourselves. for aobjs,
547 * pagefree did that for us.
548 */
549
550 if (anon) {
551 KASSERT(anon->an_swslot != 0);
552 anon->u.an_page = NULL;
553 }
554 simple_unlock(slock);
555 continue;
556 }
557
558 /*
559 * this page is dirty, skip it if we'll have met our
560 * free target when all the current pageouts complete.
561 */
562
563 if (uvmexp.free + uvmexp.paging >
564 uvmexp.freetarg << 2) {
565 simple_unlock(slock);
566 continue;
567 }
568
569 /*
570 * free any swap space allocated to the page since
571 * we'll have to write it again with its new data.
572 */
573
574 if ((p->pqflags & PQ_ANON) && anon->an_swslot) {
575 uvm_swap_free(anon->an_swslot, 1);
576 anon->an_swslot = 0;
577 } else if (p->pqflags & PQ_AOBJ) {
578 uao_dropswap(uobj, p->offset >> PAGE_SHIFT);
579 }
580
581 /*
582 * if all pages in swap are only in swap,
583 * the swap space is full and we can't page out
584 * any more swap-backed pages. reactivate this page
585 * so that we eventually cycle all pages through
586 * the inactive queue.
587 */
588
589 KASSERT(uvmexp.swpgonly <= uvmexp.swpages);
590 if (uvmexp.swpgonly == uvmexp.swpages) {
591 dirtyreacts++;
592 uvm_pageactivate(p);
593 simple_unlock(slock);
594 continue;
595 }
596
597 /*
598 * start new swap pageout cluster (if necessary).
599 */
600
601 if (swslot == 0) {
602 swnpages = MAXBSIZE >> PAGE_SHIFT;
603 swslot = uvm_swap_alloc(&swnpages, TRUE);
604 if (swslot == 0) {
605 simple_unlock(slock);
606 continue;
607 }
608 swcpages = 0;
609 }
610
611 /*
612 * at this point, we're definitely going reuse this
613 * page. mark the page busy and delayed-free.
614 * we should remove the page from the page queues
615 * so we don't ever look at it again.
616 * adjust counters and such.
617 */
618
619 p->flags |= PG_BUSY;
620 UVM_PAGE_OWN(p, "scan_inactive");
621
622 p->flags |= PG_PAGEOUT;
623 uvmexp.paging++;
624 uvm_pagedequeue(p);
625
626 uvmexp.pgswapout++;
627
628 /*
629 * add the new page to the cluster.
630 */
631
632 if (anon) {
633 anon->an_swslot = swslot + swcpages;
634 simple_unlock(slock);
635 } else {
636 result = uao_set_swslot(uobj,
637 p->offset >> PAGE_SHIFT, swslot + swcpages);
638 if (result == -1) {
639 p->flags &= ~(PG_BUSY|PG_PAGEOUT);
640 UVM_PAGE_OWN(p, NULL);
641 uvmexp.paging--;
642 uvm_pageactivate(p);
643 simple_unlock(slock);
644 continue;
645 }
646 simple_unlock(slock);
647 }
648 swpps[swcpages] = p;
649 swcpages++;
650
651 /*
652 * if the cluster isn't full, look for more pages
653 * before starting the i/o.
654 */
655
656 if (swcpages < swnpages) {
657 continue;
658 }
659 }
660
661 /*
662 * if this is the final pageout we could have a few
663 * unused swap blocks. if so, free them now.
664 */
665
666 if (swcpages < swnpages) {
667 uvm_swap_free(swslot + swcpages, (swnpages - swcpages));
668 }
669
670 /*
671 * now start the pageout.
672 */
673
674 uvm_unlock_pageq();
675 uvmexp.pdpageouts++;
676 error = uvm_swap_put(swslot, swpps, swcpages, 0);
677 KASSERT(error == 0);
678 uvm_lock_pageq();
679
680 /*
681 * zero swslot to indicate that we are
682 * no longer building a swap-backed cluster.
683 */
684
685 swslot = 0;
686
687 /*
688 * the pageout is in progress. bump counters and set up
689 * for the next loop.
690 */
691
692 uvmexp.pdpending++;
693 if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) {
694 nextpg = TAILQ_FIRST(pglst);
695 }
696 }
697 return (error);
698 }
699
700 /*
701 * uvmpd_scan: scan the page queues and attempt to meet our targets.
702 *
703 * => called with pageq's locked
704 */
705
706 void
707 uvmpd_scan(void)
708 {
709 int inactive_shortage, swap_shortage, pages_freed;
710 struct vm_page *p, *nextpg;
711 struct uvm_object *uobj;
712 struct vm_anon *anon;
713 boolean_t got_it;
714 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist);
715
716 uvmexp.pdrevs++;
717 uobj = NULL;
718 anon = NULL;
719
720 #ifndef __SWAP_BROKEN
721 /*
722 * swap out some processes if we are below our free target.
723 * we need to unlock the page queues for this.
724 */
725 if (uvmexp.free < uvmexp.freetarg) {
726 uvmexp.pdswout++;
727 UVMHIST_LOG(pdhist," free %d < target %d: swapout",
728 uvmexp.free, uvmexp.freetarg, 0, 0);
729 uvm_unlock_pageq();
730 uvm_swapout_threads();
731 uvm_lock_pageq();
732
733 }
734 #endif
735
736 /*
737 * now we want to work on meeting our targets. first we work on our
738 * free target by converting inactive pages into free pages. then
739 * we work on meeting our inactive target by converting active pages
740 * to inactive ones.
741 */
742
743 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0);
744
745 /*
746 * alternate starting queue between swap and object based on the
747 * low bit of uvmexp.pdrevs (which we bump by one each call).
748 */
749
750 got_it = FALSE;
751 pages_freed = uvmexp.pdfreed;
752 (void) uvmpd_scan_inactive(&uvm.page_inactive);
753 pages_freed = uvmexp.pdfreed - pages_freed;
754
755 /*
756 * we have done the scan to get free pages. now we work on meeting
757 * our inactive target.
758 */
759
760 inactive_shortage = uvmexp.inactarg - uvmexp.inactive;
761
762 /*
763 * detect if we're not going to be able to page anything out
764 * until we free some swap resources from active pages.
765 */
766
767 swap_shortage = 0;
768 if (uvmexp.free < uvmexp.freetarg &&
769 uvmexp.swpginuse == uvmexp.swpages &&
770 uvmexp.swpgonly < uvmexp.swpages &&
771 pages_freed == 0) {
772 swap_shortage = uvmexp.freetarg - uvmexp.free;
773 }
774
775 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%d swap_shortage=%d",
776 inactive_shortage, swap_shortage,0,0);
777 for (p = TAILQ_FIRST(&uvm.page_active);
778 p != NULL && (inactive_shortage > 0 || swap_shortage > 0);
779 p = nextpg) {
780 nextpg = TAILQ_NEXT(p, pageq);
781 if (p->flags & PG_BUSY) {
782 continue;
783 }
784
785 /*
786 * lock the page's owner.
787 */
788 /* is page anon owned or ownerless? */
789 if ((p->pqflags & PQ_ANON) || p->uobject == NULL) {
790 anon = p->uanon;
791 KASSERT(anon != NULL);
792 if (!simple_lock_try(&anon->an_lock)) {
793 continue;
794 }
795
796 /* take over the page? */
797 if ((p->pqflags & PQ_ANON) == 0) {
798 KASSERT(p->loan_count > 0);
799 p->loan_count--;
800 p->pqflags |= PQ_ANON;
801 }
802 } else {
803 uobj = p->uobject;
804 if (!simple_lock_try(&uobj->vmobjlock)) {
805 continue;
806 }
807 }
808
809 /*
810 * skip this page if it's busy.
811 */
812
813 if ((p->flags & PG_BUSY) != 0) {
814 if (p->pqflags & PQ_ANON)
815 simple_unlock(&anon->an_lock);
816 else
817 simple_unlock(&uobj->vmobjlock);
818 continue;
819 }
820
821 /*
822 * if there's a shortage of swap, free any swap allocated
823 * to this page so that other pages can be paged out.
824 */
825
826 if (swap_shortage > 0) {
827 if ((p->pqflags & PQ_ANON) && anon->an_swslot) {
828 uvm_swap_free(anon->an_swslot, 1);
829 anon->an_swslot = 0;
830 p->flags &= ~PG_CLEAN;
831 swap_shortage--;
832 } else if (p->pqflags & PQ_AOBJ) {
833 int slot = uao_set_swslot(uobj,
834 p->offset >> PAGE_SHIFT, 0);
835 if (slot) {
836 uvm_swap_free(slot, 1);
837 p->flags &= ~PG_CLEAN;
838 swap_shortage--;
839 }
840 }
841 }
842
843 /*
844 * if there's a shortage of inactive pages, deactivate.
845 */
846
847 if (inactive_shortage > 0) {
848 /* no need to check wire_count as pg is "active" */
849 uvm_pagedeactivate(p);
850 uvmexp.pddeact++;
851 inactive_shortage--;
852 }
853
854 /*
855 * we're done with this page.
856 */
857
858 if (p->pqflags & PQ_ANON)
859 simple_unlock(&anon->an_lock);
860 else
861 simple_unlock(&uobj->vmobjlock);
862 }
863 }
864