1 /* $NetBSD: uvm_pdaemon.c,v 1.133 2021/04/17 21:37:21 mrg 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. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 * @(#)vm_pageout.c 8.5 (Berkeley) 2/14/94
37 * from: Id: uvm_pdaemon.c,v 1.1.2.32 1998/02/06 05:26:30 chs Exp
38 *
39 *
40 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
41 * All rights reserved.
42 *
43 * Permission to use, copy, modify and distribute this software and
44 * its documentation is hereby granted, provided that both the copyright
45 * notice and this permission notice appear in all copies of the
46 * software, derivative works or modified versions, and any portions
47 * thereof, and that both notices appear in supporting documentation.
48 *
49 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
50 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
51 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
52 *
53 * Carnegie Mellon requests users of this software to return to
54 *
55 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
56 * School of Computer Science
57 * Carnegie Mellon University
58 * Pittsburgh PA 15213-3890
59 *
60 * any improvements or extensions that they make and grant Carnegie the
61 * rights to redistribute these changes.
62 */
63
64 /*
65 * uvm_pdaemon.c: the page daemon
66 */
67
68 #include <sys/cdefs.h>
69 __KERNEL_RCSID(0, "$NetBSD: uvm_pdaemon.c,v 1.133 2021/04/17 21:37:21 mrg Exp $");
70
71 #include "opt_uvmhist.h"
72 #include "opt_readahead.h"
73
74 #define __RWLOCK_PRIVATE
75
76 #include <sys/param.h>
77 #include <sys/proc.h>
78 #include <sys/systm.h>
79 #include <sys/kernel.h>
80 #include <sys/pool.h>
81 #include <sys/buf.h>
82 #include <sys/module.h>
83 #include <sys/atomic.h>
84 #include <sys/kthread.h>
85
86 #include <uvm/uvm.h>
87 #include <uvm/uvm_pdpolicy.h>
88 #include <uvm/uvm_pgflcache.h>
89
90 #ifdef UVMHIST
91 #ifndef UVMHIST_PDHIST_SIZE
92 #define UVMHIST_PDHIST_SIZE 100
93 #endif
94 static struct kern_history_ent pdhistbuf[UVMHIST_PDHIST_SIZE];
95 UVMHIST_DEFINE(pdhist) = UVMHIST_INITIALIZER(pdhisthist, pdhistbuf);
96 #endif
97
98 /*
99 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate
100 * in a pass thru the inactive list when swap is full. the value should be
101 * "small"... if it's too large we'll cycle the active pages thru the inactive
102 * queue too quickly to for them to be referenced and avoid being freed.
103 */
104
105 #define UVMPD_NUMDIRTYREACTS 16
106
107 /*
108 * local prototypes
109 */
110
111 static void uvmpd_scan(void);
112 static void uvmpd_scan_queue(void);
113 static void uvmpd_tune(void);
114 static void uvmpd_pool_drain_thread(void *);
115 static void uvmpd_pool_drain_wakeup(void);
116
117 static unsigned int uvm_pagedaemon_waiters;
118
119 /* State for the pool drainer thread */
120 static kmutex_t uvmpd_lock __cacheline_aligned;
121 static kcondvar_t uvmpd_pool_drain_cv;
122 static bool uvmpd_pool_drain_run = false;
123
124 /*
125 * XXX hack to avoid hangs when large processes fork.
126 */
127 u_int uvm_extrapages;
128
129 /*
130 * uvm_wait: wait (sleep) for the page daemon to free some pages
131 *
132 * => should be called with all locks released
133 * => should _not_ be called by the page daemon (to avoid deadlock)
134 */
135
136 void
uvm_wait(const char * wmsg)137 uvm_wait(const char *wmsg)
138 {
139 int timo = 0;
140
141 if (uvm.pagedaemon_lwp == NULL)
142 panic("out of memory before the pagedaemon thread exists");
143
144 mutex_spin_enter(&uvmpd_lock);
145
146 /*
147 * check for page daemon going to sleep (waiting for itself)
148 */
149
150 if (curlwp == uvm.pagedaemon_lwp && uvmexp.paging == 0) {
151 /*
152 * now we have a problem: the pagedaemon wants to go to
153 * sleep until it frees more memory. but how can it
154 * free more memory if it is asleep? that is a deadlock.
155 * we have two options:
156 * [1] panic now
157 * [2] put a timeout on the sleep, thus causing the
158 * pagedaemon to only pause (rather than sleep forever)
159 *
160 * note that option [2] will only help us if we get lucky
161 * and some other process on the system breaks the deadlock
162 * by exiting or freeing memory (thus allowing the pagedaemon
163 * to continue). for now we panic if DEBUG is defined,
164 * otherwise we hope for the best with option [2] (better
165 * yet, this should never happen in the first place!).
166 */
167
168 printf("pagedaemon: deadlock detected!\n");
169 timo = hz >> 3; /* set timeout */
170 #if defined(DEBUG)
171 /* DEBUG: panic so we can debug it */
172 panic("pagedaemon deadlock");
173 #endif
174 }
175
176 uvm_pagedaemon_waiters++;
177 wakeup(&uvm.pagedaemon); /* wake the daemon! */
178 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvmpd_lock, false, wmsg, timo);
179 }
180
181 /*
182 * uvm_kick_pdaemon: perform checks to determine if we need to
183 * give the pagedaemon a nudge, and do so if necessary.
184 */
185
186 void
uvm_kick_pdaemon(void)187 uvm_kick_pdaemon(void)
188 {
189 int fpages = uvm_availmem(false);
190
191 if (fpages + uvmexp.paging < uvmexp.freemin ||
192 (fpages + uvmexp.paging < uvmexp.freetarg &&
193 uvmpdpol_needsscan_p()) ||
194 uvm_km_va_starved_p()) {
195 mutex_spin_enter(&uvmpd_lock);
196 wakeup(&uvm.pagedaemon);
197 mutex_spin_exit(&uvmpd_lock);
198 }
199 }
200
201 /*
202 * uvmpd_tune: tune paging parameters
203 *
204 * => called when ever memory is added (or removed?) to the system
205 */
206
207 static void
uvmpd_tune(void)208 uvmpd_tune(void)
209 {
210 int val;
211
212 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist);
213
214 /*
215 * try to keep 0.5% of available RAM free, but limit to between
216 * 128k and 1024k per-CPU. XXX: what are these values good for?
217 */
218 val = uvmexp.npages / 200;
219 val = MAX(val, (128*1024) >> PAGE_SHIFT);
220 val = MIN(val, (1024*1024) >> PAGE_SHIFT);
221 val *= ncpu;
222
223 /* Make sure there's always a user page free. */
224 if (val < uvmexp.reserve_kernel + 1)
225 val = uvmexp.reserve_kernel + 1;
226 uvmexp.freemin = val;
227
228 /* Calculate free target. */
229 val = (uvmexp.freemin * 4) / 3;
230 if (val <= uvmexp.freemin)
231 val = uvmexp.freemin + 1;
232 uvmexp.freetarg = val + atomic_swap_uint(&uvm_extrapages, 0);
233
234 uvmexp.wiredmax = uvmexp.npages / 3;
235 UVMHIST_LOG(pdhist, "<- done, freemin=%jd, freetarg=%jd, wiredmax=%jd",
236 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0);
237 }
238
239 /*
240 * uvm_pageout: the main loop for the pagedaemon
241 */
242
243 void
uvm_pageout(void * arg)244 uvm_pageout(void *arg)
245 {
246 int npages = 0;
247 int extrapages = 0;
248 int fpages;
249
250 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist);
251
252 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0);
253
254 mutex_init(&uvmpd_lock, MUTEX_DEFAULT, IPL_VM);
255 cv_init(&uvmpd_pool_drain_cv, "pooldrain");
256
257 /* Create the pool drainer kernel thread. */
258 if (kthread_create(PRI_VM, KTHREAD_MPSAFE, NULL,
259 uvmpd_pool_drain_thread, NULL, NULL, "pooldrain"))
260 panic("fork pooldrain");
261
262 /*
263 * ensure correct priority and set paging parameters...
264 */
265
266 uvm.pagedaemon_lwp = curlwp;
267 npages = uvmexp.npages;
268 uvmpd_tune();
269
270 /*
271 * main loop
272 */
273
274 for (;;) {
275 bool needsscan, needsfree, kmem_va_starved;
276
277 kmem_va_starved = uvm_km_va_starved_p();
278
279 mutex_spin_enter(&uvmpd_lock);
280 if ((uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) &&
281 !kmem_va_starved) {
282 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0);
283 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon,
284 &uvmpd_lock, false, "pgdaemon", 0);
285 uvmexp.pdwoke++;
286 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0);
287 } else {
288 mutex_spin_exit(&uvmpd_lock);
289 }
290
291 /*
292 * now recompute inactive count
293 */
294
295 if (npages != uvmexp.npages || extrapages != uvm_extrapages) {
296 npages = uvmexp.npages;
297 extrapages = uvm_extrapages;
298 uvmpd_tune();
299 }
300
301 uvmpdpol_tune();
302
303 /*
304 * Estimate a hint. Note that bufmem are returned to
305 * system only when entire pool page is empty.
306 */
307 fpages = uvm_availmem(false);
308 UVMHIST_LOG(pdhist," free/ftarg=%jd/%jd",
309 fpages, uvmexp.freetarg, 0,0);
310
311 needsfree = fpages + uvmexp.paging < uvmexp.freetarg;
312 needsscan = needsfree || uvmpdpol_needsscan_p();
313
314 /*
315 * scan if needed
316 */
317 if (needsscan) {
318 uvmpd_scan();
319 }
320
321 /*
322 * if there's any free memory to be had,
323 * wake up any waiters.
324 */
325 if (uvm_availmem(false) > uvmexp.reserve_kernel ||
326 uvmexp.paging == 0) {
327 mutex_spin_enter(&uvmpd_lock);
328 wakeup(&uvmexp.free);
329 uvm_pagedaemon_waiters = 0;
330 mutex_spin_exit(&uvmpd_lock);
331 }
332
333 /*
334 * scan done. if we don't need free memory, we're done.
335 */
336
337 if (!needsfree && !kmem_va_starved)
338 continue;
339
340 /*
341 * kick the pool drainer thread.
342 */
343
344 uvmpd_pool_drain_wakeup();
345 }
346 /*NOTREACHED*/
347 }
348
349 void
uvm_pageout_start(int npages)350 uvm_pageout_start(int npages)
351 {
352
353 atomic_add_int(&uvmexp.paging, npages);
354 }
355
356 void
uvm_pageout_done(int npages)357 uvm_pageout_done(int npages)
358 {
359
360 KASSERT(atomic_load_relaxed(&uvmexp.paging) >= npages);
361
362 if (npages == 0) {
363 return;
364 }
365
366 atomic_add_int(&uvmexp.paging, -npages);
367
368 /*
369 * wake up either of pagedaemon or LWPs waiting for it.
370 */
371
372 mutex_spin_enter(&uvmpd_lock);
373 if (uvm_availmem(false) <= uvmexp.reserve_kernel) {
374 wakeup(&uvm.pagedaemon);
375 } else if (uvm_pagedaemon_waiters != 0) {
376 wakeup(&uvmexp.free);
377 uvm_pagedaemon_waiters = 0;
378 }
379 mutex_spin_exit(&uvmpd_lock);
380 }
381
382 static krwlock_t *
uvmpd_page_owner_lock(struct vm_page * pg)383 uvmpd_page_owner_lock(struct vm_page *pg)
384 {
385 struct uvm_object *uobj = pg->uobject;
386 struct vm_anon *anon = pg->uanon;
387 krwlock_t *slock;
388
389 KASSERT(mutex_owned(&pg->interlock));
390
391 #ifdef DEBUG
392 if (uobj == (void *)0xdeadbeef || anon == (void *)0xdeadbeef) {
393 return NULL;
394 }
395 #endif
396 if (uobj != NULL) {
397 slock = uobj->vmobjlock;
398 KASSERTMSG(slock != NULL, "pg %p uobj %p, NULL lock", pg, uobj);
399 } else if (anon != NULL) {
400 slock = anon->an_lock;
401 KASSERTMSG(slock != NULL, "pg %p anon %p, NULL lock", pg, anon);
402 } else {
403 slock = NULL;
404 }
405 return slock;
406 }
407
408 /*
409 * uvmpd_trylockowner: trylock the page's owner.
410 *
411 * => called with page interlock held.
412 * => resolve orphaned O->A loaned page.
413 * => return the locked mutex on success. otherwise, return NULL.
414 */
415
416 krwlock_t *
uvmpd_trylockowner(struct vm_page * pg)417 uvmpd_trylockowner(struct vm_page *pg)
418 {
419 krwlock_t *slock, *heldslock;
420
421 KASSERT(mutex_owned(&pg->interlock));
422
423 slock = uvmpd_page_owner_lock(pg);
424 if (slock == NULL) {
425 /* Page may be in state of flux - ignore. */
426 mutex_exit(&pg->interlock);
427 return NULL;
428 }
429
430 if (rw_tryenter(slock, RW_WRITER)) {
431 goto success;
432 }
433
434 /*
435 * The try-lock didn't work, so now do a blocking lock after
436 * dropping the page interlock. Prevent the owner lock from
437 * being freed by taking a hold on it first.
438 */
439
440 rw_obj_hold(slock);
441 mutex_exit(&pg->interlock);
442 rw_enter(slock, RW_WRITER);
443 heldslock = slock;
444
445 /*
446 * Now we hold some owner lock. Check if the lock we hold
447 * is still the lock for the owner of the page.
448 * If it is then return it, otherwise release it and return NULL.
449 */
450
451 mutex_enter(&pg->interlock);
452 slock = uvmpd_page_owner_lock(pg);
453 if (heldslock != slock) {
454 rw_exit(heldslock);
455 slock = NULL;
456 }
457 rw_obj_free(heldslock);
458 if (slock != NULL) {
459 success:
460 /*
461 * Set PG_ANON if it isn't set already.
462 */
463 if (pg->uobject == NULL && (pg->flags & PG_ANON) == 0) {
464 KASSERT(pg->loan_count > 0);
465 pg->loan_count--;
466 pg->flags |= PG_ANON;
467 /* anon now owns it */
468 }
469 }
470 mutex_exit(&pg->interlock);
471 return slock;
472 }
473
474 #if defined(VMSWAP)
475 struct swapcluster {
476 int swc_slot;
477 int swc_nallocated;
478 int swc_nused;
479 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)];
480 };
481
482 static void
swapcluster_init(struct swapcluster * swc)483 swapcluster_init(struct swapcluster *swc)
484 {
485
486 swc->swc_slot = 0;
487 swc->swc_nused = 0;
488 }
489
490 static int
swapcluster_allocslots(struct swapcluster * swc)491 swapcluster_allocslots(struct swapcluster *swc)
492 {
493 int slot;
494 int npages;
495
496 if (swc->swc_slot != 0) {
497 return 0;
498 }
499
500 /* Even with strange MAXPHYS, the shift
501 implicitly rounds down to a page. */
502 npages = MAXPHYS >> PAGE_SHIFT;
503 slot = uvm_swap_alloc(&npages, true);
504 if (slot == 0) {
505 return ENOMEM;
506 }
507 swc->swc_slot = slot;
508 swc->swc_nallocated = npages;
509 swc->swc_nused = 0;
510
511 return 0;
512 }
513
514 static int
swapcluster_add(struct swapcluster * swc,struct vm_page * pg)515 swapcluster_add(struct swapcluster *swc, struct vm_page *pg)
516 {
517 int slot;
518 struct uvm_object *uobj;
519
520 KASSERT(swc->swc_slot != 0);
521 KASSERT(swc->swc_nused < swc->swc_nallocated);
522 KASSERT((pg->flags & PG_SWAPBACKED) != 0);
523
524 slot = swc->swc_slot + swc->swc_nused;
525 uobj = pg->uobject;
526 if (uobj == NULL) {
527 KASSERT(rw_write_held(pg->uanon->an_lock));
528 pg->uanon->an_swslot = slot;
529 } else {
530 int result;
531
532 KASSERT(rw_write_held(uobj->vmobjlock));
533 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot);
534 if (result == -1) {
535 return ENOMEM;
536 }
537 }
538 swc->swc_pages[swc->swc_nused] = pg;
539 swc->swc_nused++;
540
541 return 0;
542 }
543
544 static void
swapcluster_flush(struct swapcluster * swc,bool now)545 swapcluster_flush(struct swapcluster *swc, bool now)
546 {
547 int slot;
548 int nused;
549 int nallocated;
550 int error __diagused;
551
552 if (swc->swc_slot == 0) {
553 return;
554 }
555 KASSERT(swc->swc_nused <= swc->swc_nallocated);
556
557 slot = swc->swc_slot;
558 nused = swc->swc_nused;
559 nallocated = swc->swc_nallocated;
560
561 /*
562 * if this is the final pageout we could have a few
563 * unused swap blocks. if so, free them now.
564 */
565
566 if (nused < nallocated) {
567 if (!now) {
568 return;
569 }
570 uvm_swap_free(slot + nused, nallocated - nused);
571 }
572
573 /*
574 * now start the pageout.
575 */
576
577 if (nused > 0) {
578 uvmexp.pdpageouts++;
579 uvm_pageout_start(nused);
580 error = uvm_swap_put(slot, swc->swc_pages, nused, 0);
581 KASSERT(error == 0 || error == ENOMEM);
582 }
583
584 /*
585 * zero swslot to indicate that we are
586 * no longer building a swap-backed cluster.
587 */
588
589 swc->swc_slot = 0;
590 swc->swc_nused = 0;
591 }
592
593 static int
swapcluster_nused(struct swapcluster * swc)594 swapcluster_nused(struct swapcluster *swc)
595 {
596
597 return swc->swc_nused;
598 }
599
600 /*
601 * uvmpd_dropswap: free any swap allocated to this page.
602 *
603 * => called with owner locked.
604 * => return true if a page had an associated slot.
605 */
606
607 bool
uvmpd_dropswap(struct vm_page * pg)608 uvmpd_dropswap(struct vm_page *pg)
609 {
610 bool result = false;
611 struct vm_anon *anon = pg->uanon;
612
613 if ((pg->flags & PG_ANON) && anon->an_swslot) {
614 uvm_swap_free(anon->an_swslot, 1);
615 anon->an_swslot = 0;
616 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY);
617 result = true;
618 } else if (pg->flags & PG_AOBJ) {
619 int slot = uao_set_swslot(pg->uobject,
620 pg->offset >> PAGE_SHIFT, 0);
621 if (slot) {
622 uvm_swap_free(slot, 1);
623 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY);
624 result = true;
625 }
626 }
627
628 return result;
629 }
630
631 #endif /* defined(VMSWAP) */
632
633 /*
634 * uvmpd_scan_queue: scan an replace candidate list for pages
635 * to clean or free.
636 *
637 * => we work on meeting our free target by converting inactive pages
638 * into free pages.
639 * => we handle the building of swap-backed clusters
640 */
641
642 static void
uvmpd_scan_queue(void)643 uvmpd_scan_queue(void)
644 {
645 struct vm_page *p;
646 struct uvm_object *uobj;
647 struct vm_anon *anon;
648 #if defined(VMSWAP)
649 struct swapcluster swc;
650 #endif /* defined(VMSWAP) */
651 int dirtyreacts;
652 krwlock_t *slock;
653 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist);
654
655 /*
656 * swslot is non-zero if we are building a swap cluster. we want
657 * to stay in the loop while we have a page to scan or we have
658 * a swap-cluster to build.
659 */
660
661 #if defined(VMSWAP)
662 swapcluster_init(&swc);
663 #endif /* defined(VMSWAP) */
664
665 dirtyreacts = 0;
666 uvmpdpol_scaninit();
667
668 while (/* CONSTCOND */ 1) {
669
670 /*
671 * see if we've met the free target.
672 */
673
674 if (uvm_availmem(false) + uvmexp.paging
675 #if defined(VMSWAP)
676 + swapcluster_nused(&swc)
677 #endif /* defined(VMSWAP) */
678 >= uvmexp.freetarg << 2 ||
679 dirtyreacts == UVMPD_NUMDIRTYREACTS) {
680 UVMHIST_LOG(pdhist," met free target: "
681 "exit loop", 0, 0, 0, 0);
682 break;
683 }
684
685 /*
686 * first we have the pdpolicy select a victim page
687 * and attempt to lock the object that the page
688 * belongs to. if our attempt fails we skip on to
689 * the next page (no harm done). it is important to
690 * "try" locking the object as we are locking in the
691 * wrong order (pageq -> object) and we don't want to
692 * deadlock.
693 *
694 * the only time we expect to see an ownerless page
695 * (i.e. a page with no uobject and !PG_ANON) is if an
696 * anon has loaned a page from a uvm_object and the
697 * uvm_object has dropped the ownership. in that
698 * case, the anon can "take over" the loaned page
699 * and make it its own.
700 */
701
702 p = uvmpdpol_selectvictim(&slock);
703 if (p == NULL) {
704 break;
705 }
706 KASSERT(uvmpdpol_pageisqueued_p(p));
707 KASSERT(uvm_page_owner_locked_p(p, true));
708 KASSERT(p->wire_count == 0);
709
710 /*
711 * we are below target and have a new page to consider.
712 */
713
714 anon = p->uanon;
715 uobj = p->uobject;
716
717 if (p->flags & PG_BUSY) {
718 rw_exit(slock);
719 uvmexp.pdbusy++;
720 continue;
721 }
722
723 /* does the page belong to an object? */
724 if (uobj != NULL) {
725 uvmexp.pdobscan++;
726 } else {
727 #if defined(VMSWAP)
728 KASSERT(anon != NULL);
729 uvmexp.pdanscan++;
730 #else /* defined(VMSWAP) */
731 panic("%s: anon", __func__);
732 #endif /* defined(VMSWAP) */
733 }
734
735
736 /*
737 * we now have the object locked.
738 * if the page is not swap-backed, call the object's
739 * pager to flush and free the page.
740 */
741
742 #if defined(READAHEAD_STATS)
743 if ((p->flags & PG_READAHEAD) != 0) {
744 p->flags &= ~PG_READAHEAD;
745 uvm_ra_miss.ev_count++;
746 }
747 #endif /* defined(READAHEAD_STATS) */
748
749 if ((p->flags & PG_SWAPBACKED) == 0) {
750 KASSERT(uobj != NULL);
751 (void) (uobj->pgops->pgo_put)(uobj, p->offset,
752 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE);
753 continue;
754 }
755
756 /*
757 * the page is swap-backed. remove all the permissions
758 * from the page so we can sync the modified info
759 * without any race conditions. if the page is clean
760 * we can free it now and continue.
761 */
762
763 pmap_page_protect(p, VM_PROT_NONE);
764 if (uvm_pagegetdirty(p) == UVM_PAGE_STATUS_UNKNOWN) {
765 if (pmap_clear_modify(p)) {
766 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_DIRTY);
767 } else {
768 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_CLEAN);
769 }
770 }
771 if (uvm_pagegetdirty(p) != UVM_PAGE_STATUS_DIRTY) {
772 int slot;
773 int pageidx;
774
775 pageidx = p->offset >> PAGE_SHIFT;
776 uvm_pagefree(p);
777 atomic_inc_uint(&uvmexp.pdfreed);
778
779 /*
780 * for anons, we need to remove the page
781 * from the anon ourselves. for aobjs,
782 * pagefree did that for us.
783 */
784
785 if (anon) {
786 KASSERT(anon->an_swslot != 0);
787 anon->an_page = NULL;
788 slot = anon->an_swslot;
789 } else {
790 slot = uao_find_swslot(uobj, pageidx);
791 }
792 if (slot > 0) {
793 /* this page is now only in swap. */
794 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse);
795 atomic_inc_uint(&uvmexp.swpgonly);
796 }
797 rw_exit(slock);
798 continue;
799 }
800
801 #if defined(VMSWAP)
802 /*
803 * this page is dirty, skip it if we'll have met our
804 * free target when all the current pageouts complete.
805 */
806
807 if (uvm_availmem(false) + uvmexp.paging >
808 uvmexp.freetarg << 2) {
809 rw_exit(slock);
810 continue;
811 }
812
813 /*
814 * free any swap space allocated to the page since
815 * we'll have to write it again with its new data.
816 */
817
818 uvmpd_dropswap(p);
819
820 /*
821 * start new swap pageout cluster (if necessary).
822 *
823 * if swap is full reactivate this page so that
824 * we eventually cycle all pages through the
825 * inactive queue.
826 */
827
828 if (swapcluster_allocslots(&swc)) {
829 dirtyreacts++;
830 uvm_pagelock(p);
831 uvm_pageactivate(p);
832 uvm_pageunlock(p);
833 rw_exit(slock);
834 continue;
835 }
836
837 /*
838 * at this point, we're definitely going reuse this
839 * page. mark the page busy and delayed-free.
840 * we should remove the page from the page queues
841 * so we don't ever look at it again.
842 * adjust counters and such.
843 */
844
845 p->flags |= PG_BUSY;
846 UVM_PAGE_OWN(p, "scan_queue");
847 p->flags |= PG_PAGEOUT;
848 uvmexp.pgswapout++;
849
850 uvm_pagelock(p);
851 uvm_pagedequeue(p);
852 uvm_pageunlock(p);
853
854 /*
855 * add the new page to the cluster.
856 */
857
858 if (swapcluster_add(&swc, p)) {
859 p->flags &= ~(PG_BUSY|PG_PAGEOUT);
860 UVM_PAGE_OWN(p, NULL);
861 dirtyreacts++;
862 uvm_pagelock(p);
863 uvm_pageactivate(p);
864 uvm_pageunlock(p);
865 rw_exit(slock);
866 continue;
867 }
868 rw_exit(slock);
869
870 swapcluster_flush(&swc, false);
871
872 /*
873 * the pageout is in progress. bump counters and set up
874 * for the next loop.
875 */
876
877 atomic_inc_uint(&uvmexp.pdpending);
878
879 #else /* defined(VMSWAP) */
880 uvm_pagelock(p);
881 uvm_pageactivate(p);
882 uvm_pageunlock(p);
883 rw_exit(slock);
884 #endif /* defined(VMSWAP) */
885 }
886
887 uvmpdpol_scanfini();
888
889 #if defined(VMSWAP)
890 swapcluster_flush(&swc, true);
891 #endif /* defined(VMSWAP) */
892 }
893
894 /*
895 * uvmpd_scan: scan the page queues and attempt to meet our targets.
896 */
897
898 static void
uvmpd_scan(void)899 uvmpd_scan(void)
900 {
901 int swap_shortage, pages_freed, fpages;
902 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist);
903
904 uvmexp.pdrevs++;
905
906 /*
907 * work on meeting our targets. first we work on our free target
908 * by converting inactive pages into free pages. then we work on
909 * meeting our inactive target by converting active pages to
910 * inactive ones.
911 */
912
913 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0);
914
915 pages_freed = uvmexp.pdfreed;
916 uvmpd_scan_queue();
917 pages_freed = uvmexp.pdfreed - pages_freed;
918
919 /*
920 * detect if we're not going to be able to page anything out
921 * until we free some swap resources from active pages.
922 */
923
924 swap_shortage = 0;
925 fpages = uvm_availmem(false);
926 if (fpages < uvmexp.freetarg &&
927 uvmexp.swpginuse >= uvmexp.swpgavail &&
928 !uvm_swapisfull() &&
929 pages_freed == 0) {
930 swap_shortage = uvmexp.freetarg - fpages;
931 }
932
933 uvmpdpol_balancequeue(swap_shortage);
934
935 /*
936 * if still below the minimum target, try unloading kernel
937 * modules.
938 */
939
940 if (uvm_availmem(false) < uvmexp.freemin) {
941 module_thread_kick();
942 }
943 }
944
945 /*
946 * uvm_reclaimable: decide whether to wait for pagedaemon.
947 *
948 * => return true if it seems to be worth to do uvm_wait.
949 *
950 * XXX should be tunable.
951 * XXX should consider pools, etc?
952 */
953
954 bool
uvm_reclaimable(void)955 uvm_reclaimable(void)
956 {
957 int filepages;
958 int active, inactive;
959
960 /*
961 * if swap is not full, no problem.
962 */
963
964 if (!uvm_swapisfull()) {
965 return true;
966 }
967
968 /*
969 * file-backed pages can be reclaimed even when swap is full.
970 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim.
971 * NB: filepages calculation does not exclude EXECPAGES - intentional.
972 *
973 * XXX assume the worst case, ie. all wired pages are file-backed.
974 *
975 * XXX should consider about other reclaimable memory.
976 * XXX ie. pools, traditional buffer cache.
977 */
978
979 cpu_count_sync(false);
980 filepages = (int)(cpu_count_get(CPU_COUNT_FILECLEAN) +
981 cpu_count_get(CPU_COUNT_FILEUNKNOWN) +
982 cpu_count_get(CPU_COUNT_FILEDIRTY) - uvmexp.wired);
983 uvm_estimatepageable(&active, &inactive);
984 if (filepages >= MIN((active + inactive) >> 4,
985 5 * 1024 * 1024 >> PAGE_SHIFT)) {
986 return true;
987 }
988
989 /*
990 * kill the process, fail allocation, etc..
991 */
992
993 return false;
994 }
995
996 void
uvm_estimatepageable(int * active,int * inactive)997 uvm_estimatepageable(int *active, int *inactive)
998 {
999
1000 uvmpdpol_estimatepageable(active, inactive);
1001 }
1002
1003
1004 /*
1005 * Use a separate thread for draining pools.
1006 * This work can't done from the main pagedaemon thread because
1007 * some pool allocators need to take vm_map locks.
1008 */
1009
1010 static void
uvmpd_pool_drain_thread(void * arg)1011 uvmpd_pool_drain_thread(void *arg)
1012 {
1013 struct pool *firstpool, *curpool;
1014 int bufcnt, lastslept;
1015 bool cycled;
1016
1017 firstpool = NULL;
1018 cycled = true;
1019 for (;;) {
1020 /*
1021 * sleep until awoken by the pagedaemon.
1022 */
1023 mutex_enter(&uvmpd_lock);
1024 if (!uvmpd_pool_drain_run) {
1025 lastslept = getticks();
1026 cv_wait(&uvmpd_pool_drain_cv, &uvmpd_lock);
1027 if (getticks() != lastslept) {
1028 cycled = false;
1029 firstpool = NULL;
1030 }
1031 }
1032 uvmpd_pool_drain_run = false;
1033 mutex_exit(&uvmpd_lock);
1034
1035 /*
1036 * rate limit draining, otherwise in desperate circumstances
1037 * this can totally saturate the system with xcall activity.
1038 */
1039 if (cycled) {
1040 kpause("uvmpdlmt", false, 1, NULL);
1041 cycled = false;
1042 firstpool = NULL;
1043 }
1044
1045 /*
1046 * drain and temporarily disable the freelist cache.
1047 */
1048 uvm_pgflcache_pause();
1049
1050 /*
1051 * kill unused metadata buffers.
1052 */
1053 bufcnt = uvmexp.freetarg - uvm_availmem(false);
1054 if (bufcnt < 0)
1055 bufcnt = 0;
1056
1057 mutex_enter(&bufcache_lock);
1058 buf_drain(bufcnt << PAGE_SHIFT);
1059 mutex_exit(&bufcache_lock);
1060
1061 /*
1062 * drain a pool, and then re-enable the freelist cache.
1063 */
1064 (void)pool_drain(&curpool);
1065 KASSERT(curpool != NULL);
1066 if (firstpool == NULL) {
1067 firstpool = curpool;
1068 } else if (firstpool == curpool) {
1069 cycled = true;
1070 }
1071 uvm_pgflcache_resume();
1072 }
1073 /*NOTREACHED*/
1074 }
1075
1076 static void
uvmpd_pool_drain_wakeup(void)1077 uvmpd_pool_drain_wakeup(void)
1078 {
1079
1080 mutex_enter(&uvmpd_lock);
1081 uvmpd_pool_drain_run = true;
1082 cv_signal(&uvmpd_pool_drain_cv);
1083 mutex_exit(&uvmpd_lock);
1084 }
1085