-
Notifications
You must be signed in to change notification settings - Fork 24
/
uvm_pdaemon.c
881 lines (743 loc) · 22 KB
/
uvm_pdaemon.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
/* $NetBSD: uvm_pdaemon.c,v 1.46.2.1 2002/07/15 10:37:35 gehenna Exp $ */
/*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
* Copyright (c) 1991, 1993, The Regents of the University of California.
*
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Charles D. Cranor,
* Washington University, the University of California, Berkeley and
* its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)vm_pageout.c 8.5 (Berkeley) 2/14/94
* from: Id: uvm_pdaemon.c,v 1.1.2.32 1998/02/06 05:26:30 chs Exp
*
*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* All rights reserved.
*
* Permission to use, copy, modify and distribute this software and
* its documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
/*
* uvm_pdaemon.c: the page daemon
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_pdaemon.c,v 1.46.2.1 2002/07/15 10:37:35 gehenna Exp $");
#include "opt_uvmhist.h"
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/pool.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <uvm/uvm.h>
/*
* UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate
* in a pass thru the inactive list when swap is full. the value should be
* "small"... if it's too large we'll cycle the active pages thru the inactive
* queue too quickly to for them to be referenced and avoid being freed.
*/
#define UVMPD_NUMDIRTYREACTS 16
/*
* local prototypes
*/
void uvmpd_scan __P((void));
void uvmpd_scan_inactive __P((struct pglist *));
void uvmpd_tune __P((void));
/*
* uvm_wait: wait (sleep) for the page daemon to free some pages
*
* => should be called with all locks released
* => should _not_ be called by the page daemon (to avoid deadlock)
*/
void
uvm_wait(wmsg)
const char *wmsg;
{
int timo = 0;
int s = splbio();
/*
* check for page daemon going to sleep (waiting for itself)
*/
if (curproc == uvm.pagedaemon_proc && uvmexp.paging == 0) {
/*
* now we have a problem: the pagedaemon wants to go to
* sleep until it frees more memory. but how can it
* free more memory if it is asleep? that is a deadlock.
* we have two options:
* [1] panic now
* [2] put a timeout on the sleep, thus causing the
* pagedaemon to only pause (rather than sleep forever)
*
* note that option [2] will only help us if we get lucky
* and some other process on the system breaks the deadlock
* by exiting or freeing memory (thus allowing the pagedaemon
* to continue). for now we panic if DEBUG is defined,
* otherwise we hope for the best with option [2] (better
* yet, this should never happen in the first place!).
*/
printf("pagedaemon: deadlock detected!\n");
timo = hz >> 3; /* set timeout */
#if defined(DEBUG)
/* DEBUG: panic so we can debug it */
panic("pagedaemon deadlock");
#endif
}
simple_lock(&uvm.pagedaemon_lock);
wakeup(&uvm.pagedaemon); /* wake the daemon! */
UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm.pagedaemon_lock, FALSE, wmsg,
timo);
splx(s);
}
/*
* uvmpd_tune: tune paging parameters
*
* => called when ever memory is added (or removed?) to the system
* => caller must call with page queues locked
*/
void
uvmpd_tune(void)
{
UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist);
uvmexp.freemin = uvmexp.npages / 20;
/* between 16k and 256k */
/* XXX: what are these values good for? */
uvmexp.freemin = MAX(uvmexp.freemin, (16*1024) >> PAGE_SHIFT);
uvmexp.freemin = MIN(uvmexp.freemin, (256*1024) >> PAGE_SHIFT);
/* Make sure there's always a user page free. */
if (uvmexp.freemin < uvmexp.reserve_kernel + 1)
uvmexp.freemin = uvmexp.reserve_kernel + 1;
uvmexp.freetarg = (uvmexp.freemin * 4) / 3;
if (uvmexp.freetarg <= uvmexp.freemin)
uvmexp.freetarg = uvmexp.freemin + 1;
/* uvmexp.inactarg: computed in main daemon loop */
uvmexp.wiredmax = uvmexp.npages / 3;
UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d",
uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0);
}
/*
* uvm_pageout: the main loop for the pagedaemon
*/
void
uvm_pageout(void *arg)
{
int npages = 0;
UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist);
UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0);
/*
* ensure correct priority and set paging parameters...
*/
uvm.pagedaemon_proc = curproc;
uvm_lock_pageq();
npages = uvmexp.npages;
uvmpd_tune();
uvm_unlock_pageq();
/*
* main loop
*/
for (;;) {
simple_lock(&uvm.pagedaemon_lock);
UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0);
UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon,
&uvm.pagedaemon_lock, FALSE, "pgdaemon", 0);
uvmexp.pdwoke++;
UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0);
/*
* now lock page queues and recompute inactive count
*/
uvm_lock_pageq();
if (npages != uvmexp.npages) { /* check for new pages? */
npages = uvmexp.npages;
uvmpd_tune();
}
uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3;
if (uvmexp.inactarg <= uvmexp.freetarg) {
uvmexp.inactarg = uvmexp.freetarg + 1;
}
UVMHIST_LOG(pdhist," free/ftarg=%d/%d, inact/itarg=%d/%d",
uvmexp.free, uvmexp.freetarg, uvmexp.inactive,
uvmexp.inactarg);
/*
* scan if needed
*/
if (uvmexp.free + uvmexp.paging < uvmexp.freetarg ||
uvmexp.inactive < uvmexp.inactarg) {
uvmpd_scan();
}
/*
* if there's any free memory to be had,
* wake up any waiters.
*/
if (uvmexp.free > uvmexp.reserve_kernel ||
uvmexp.paging == 0) {
wakeup(&uvmexp.free);
}
/*
* scan done. unlock page queues (the only lock we are holding)
*/
uvm_unlock_pageq();
/*
* drain pool resources now that we're not holding any locks
*/
pool_drain(0);
}
/*NOTREACHED*/
}
/*
* uvm_aiodone_daemon: main loop for the aiodone daemon.
*/
void
uvm_aiodone_daemon(void *arg)
{
int s, free;
struct buf *bp, *nbp;
UVMHIST_FUNC("uvm_aiodoned"); UVMHIST_CALLED(pdhist);
for (;;) {
/*
* carefully attempt to go to sleep (without losing "wakeups"!).
* we need splbio because we want to make sure the aio_done list
* is totally empty before we go to sleep.
*/
s = splbio();
simple_lock(&uvm.aiodoned_lock);
if (TAILQ_FIRST(&uvm.aio_done) == NULL) {
UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0);
UVM_UNLOCK_AND_WAIT(&uvm.aiodoned,
&uvm.aiodoned_lock, FALSE, "aiodoned", 0);
UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0);
/* relock aiodoned_lock, still at splbio */
simple_lock(&uvm.aiodoned_lock);
}
/*
* check for done aio structures
*/
bp = TAILQ_FIRST(&uvm.aio_done);
if (bp) {
TAILQ_INIT(&uvm.aio_done);
}
simple_unlock(&uvm.aiodoned_lock);
splx(s);
/*
* process each i/o that's done.
*/
free = uvmexp.free;
while (bp != NULL) {
nbp = TAILQ_NEXT(bp, b_freelist);
(*bp->b_iodone)(bp);
bp = nbp;
}
if (free <= uvmexp.reserve_kernel) {
s = uvm_lock_fpageq();
wakeup(&uvm.pagedaemon);
uvm_unlock_fpageq(s);
} else {
simple_lock(&uvm.pagedaemon_lock);
wakeup(&uvmexp.free);
simple_unlock(&uvm.pagedaemon_lock);
}
}
}
/*
* uvmpd_scan_inactive: scan an inactive list for pages to clean or free.
*
* => called with page queues locked
* => we work on meeting our free target by converting inactive pages
* into free pages.
* => we handle the building of swap-backed clusters
* => we return TRUE if we are exiting because we met our target
*/
void
uvmpd_scan_inactive(pglst)
struct pglist *pglst;
{
int error;
struct vm_page *p, *nextpg;
struct uvm_object *uobj;
struct vm_anon *anon;
struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT];
struct simplelock *slock;
int swnpages, swcpages;
int swslot;
int dirtyreacts, t, result;
boolean_t anonunder, fileunder, execunder;
boolean_t anonover, fileover, execover;
boolean_t anonreact, filereact, execreact;
UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist);
/*
* swslot is non-zero if we are building a swap cluster. we want
* to stay in the loop while we have a page to scan or we have
* a swap-cluster to build.
*/
swslot = 0;
swnpages = swcpages = 0;
dirtyreacts = 0;
/*
* decide which types of pages we want to reactivate instead of freeing
* to keep usage within the minimum and maximum usage limits.
*/
t = uvmexp.active + uvmexp.inactive + uvmexp.free;
anonunder = (uvmexp.anonpages <= (t * uvmexp.anonmin) >> 8);
fileunder = (uvmexp.filepages <= (t * uvmexp.filemin) >> 8);
execunder = (uvmexp.execpages <= (t * uvmexp.execmin) >> 8);
anonover = uvmexp.anonpages > ((t * uvmexp.anonmax) >> 8);
fileover = uvmexp.filepages > ((t * uvmexp.filemax) >> 8);
execover = uvmexp.execpages > ((t * uvmexp.execmax) >> 8);
anonreact = anonunder || (!anonover && (fileover || execover));
filereact = fileunder || (!fileover && (anonover || execover));
execreact = execunder || (!execover && (anonover || fileover));
for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) {
uobj = NULL;
anon = NULL;
if (p) {
/*
* see if we've met the free target.
*/
if (uvmexp.free + uvmexp.paging >=
uvmexp.freetarg << 2 ||
dirtyreacts == UVMPD_NUMDIRTYREACTS) {
UVMHIST_LOG(pdhist," met free target: "
"exit loop", 0, 0, 0, 0);
if (swslot == 0) {
/* exit now if no swap-i/o pending */
break;
}
/* set p to null to signal final swap i/o */
p = NULL;
nextpg = NULL;
}
}
if (p) { /* if (we have a new page to consider) */
/*
* we are below target and have a new page to consider.
*/
uvmexp.pdscans++;
nextpg = TAILQ_NEXT(p, pageq);
/*
* move referenced pages back to active queue and
* skip to next page.
*/
if (pmap_clear_reference(p)) {
uvm_pageactivate(p);
uvmexp.pdreact++;
continue;
}
anon = p->uanon;
uobj = p->uobject;
/*
* enforce the minimum thresholds on different
* types of memory usage. if reusing the current
* page would reduce that type of usage below its
* minimum, reactivate the page instead and move
* on to the next page.
*/
if (uobj && UVM_OBJ_IS_VTEXT(uobj) && execreact) {
uvm_pageactivate(p);
uvmexp.pdreexec++;
continue;
}
if (uobj && UVM_OBJ_IS_VNODE(uobj) &&
!UVM_OBJ_IS_VTEXT(uobj) && filereact) {
uvm_pageactivate(p);
uvmexp.pdrefile++;
continue;
}
if ((anon || UVM_OBJ_IS_AOBJ(uobj)) && anonreact) {
uvm_pageactivate(p);
uvmexp.pdreanon++;
continue;
}
/*
* first we attempt to lock the object that this page
* belongs to. if our attempt fails we skip on to
* the next page (no harm done). it is important to
* "try" locking the object as we are locking in the
* wrong order (pageq -> object) and we don't want to
* deadlock.
*
* the only time we expect to see an ownerless page
* (i.e. a page with no uobject and !PQ_ANON) is if an
* anon has loaned a page from a uvm_object and the
* uvm_object has dropped the ownership. in that
* case, the anon can "take over" the loaned page
* and make it its own.
*/
/* does the page belong to an object? */
if (uobj != NULL) {
slock = &uobj->vmobjlock;
if (!simple_lock_try(slock)) {
continue;
}
if (p->flags & PG_BUSY) {
simple_unlock(slock);
uvmexp.pdbusy++;
continue;
}
uvmexp.pdobscan++;
} else {
KASSERT(anon != NULL);
slock = &anon->an_lock;
if (!simple_lock_try(slock)) {
continue;
}
/*
* set PQ_ANON if it isn't set already.
*/
if ((p->pqflags & PQ_ANON) == 0) {
KASSERT(p->loan_count > 0);
p->loan_count--;
p->pqflags |= PQ_ANON;
/* anon now owns it */
}
if (p->flags & PG_BUSY) {
simple_unlock(slock);
uvmexp.pdbusy++;
continue;
}
uvmexp.pdanscan++;
}
/*
* we now have the object and the page queues locked.
* if the page is not swap-backed, call the object's
* pager to flush and free the page.
*/
if ((p->pqflags & PQ_SWAPBACKED) == 0) {
uvm_unlock_pageq();
error = (uobj->pgops->pgo_put)(uobj, p->offset,
p->offset + PAGE_SIZE,
PGO_CLEANIT|PGO_FREE);
uvm_lock_pageq();
if (nextpg &&
(nextpg->pqflags & PQ_INACTIVE) == 0) {
nextpg = TAILQ_FIRST(pglst);
}
continue;
}
/*
* the page is swap-backed. remove all the permissions
* from the page so we can sync the modified info
* without any race conditions. if the page is clean
* we can free it now and continue.
*/
pmap_page_protect(p, VM_PROT_NONE);
if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) {
p->flags &= ~(PG_CLEAN);
}
if (p->flags & PG_CLEAN) {
uvm_pagefree(p);
uvmexp.pdfreed++;
/*
* for anons, we need to remove the page
* from the anon ourselves. for aobjs,
* pagefree did that for us.
*/
if (anon) {
KASSERT(anon->an_swslot != 0);
anon->u.an_page = NULL;
}
simple_unlock(slock);
/* this page is now only in swap. */
simple_lock(&uvm.swap_data_lock);
KASSERT(uvmexp.swpgonly < uvmexp.swpginuse);
uvmexp.swpgonly++;
simple_unlock(&uvm.swap_data_lock);
continue;
}
/*
* this page is dirty, skip it if we'll have met our
* free target when all the current pageouts complete.
*/
if (uvmexp.free + uvmexp.paging >
uvmexp.freetarg << 2) {
simple_unlock(slock);
continue;
}
/*
* free any swap space allocated to the page since
* we'll have to write it again with its new data.
*/
if ((p->pqflags & PQ_ANON) && anon->an_swslot) {
uvm_swap_free(anon->an_swslot, 1);
anon->an_swslot = 0;
} else if (p->pqflags & PQ_AOBJ) {
uao_dropswap(uobj, p->offset >> PAGE_SHIFT);
}
/*
* if all pages in swap are only in swap,
* the swap space is full and we can't page out
* any more swap-backed pages. reactivate this page
* so that we eventually cycle all pages through
* the inactive queue.
*/
KASSERT(uvmexp.swpgonly <= uvmexp.swpages);
if (uvmexp.swpgonly == uvmexp.swpages) {
dirtyreacts++;
uvm_pageactivate(p);
simple_unlock(slock);
continue;
}
/*
* start new swap pageout cluster (if necessary).
*/
if (swslot == 0) {
swnpages = MAXBSIZE >> PAGE_SHIFT;
swslot = uvm_swap_alloc(&swnpages, TRUE);
if (swslot == 0) {
simple_unlock(slock);
continue;
}
swcpages = 0;
}
/*
* at this point, we're definitely going reuse this
* page. mark the page busy and delayed-free.
* we should remove the page from the page queues
* so we don't ever look at it again.
* adjust counters and such.
*/
p->flags |= PG_BUSY;
UVM_PAGE_OWN(p, "scan_inactive");
p->flags |= PG_PAGEOUT;
uvmexp.paging++;
uvm_pagedequeue(p);
uvmexp.pgswapout++;
/*
* add the new page to the cluster.
*/
if (anon) {
anon->an_swslot = swslot + swcpages;
simple_unlock(slock);
} else {
result = uao_set_swslot(uobj,
p->offset >> PAGE_SHIFT, swslot + swcpages);
if (result == -1) {
p->flags &= ~(PG_BUSY|PG_PAGEOUT);
UVM_PAGE_OWN(p, NULL);
uvmexp.paging--;
uvm_pageactivate(p);
simple_unlock(slock);
continue;
}
simple_unlock(slock);
}
swpps[swcpages] = p;
swcpages++;
/*
* if the cluster isn't full, look for more pages
* before starting the i/o.
*/
if (swcpages < swnpages) {
continue;
}
}
/*
* if this is the final pageout we could have a few
* unused swap blocks. if so, free them now.
*/
if (swcpages < swnpages) {
uvm_swap_free(swslot + swcpages, (swnpages - swcpages));
}
/*
* now start the pageout.
*/
uvm_unlock_pageq();
uvmexp.pdpageouts++;
error = uvm_swap_put(swslot, swpps, swcpages, 0);
KASSERT(error == 0);
uvm_lock_pageq();
/*
* zero swslot to indicate that we are
* no longer building a swap-backed cluster.
*/
swslot = 0;
/*
* the pageout is in progress. bump counters and set up
* for the next loop.
*/
uvmexp.pdpending++;
if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) {
nextpg = TAILQ_FIRST(pglst);
}
}
}
/*
* uvmpd_scan: scan the page queues and attempt to meet our targets.
*
* => called with pageq's locked
*/
void
uvmpd_scan(void)
{
int inactive_shortage, swap_shortage, pages_freed;
struct vm_page *p, *nextpg;
struct uvm_object *uobj;
struct vm_anon *anon;
struct simplelock *slock;
UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist);
uvmexp.pdrevs++;
uobj = NULL;
anon = NULL;
#ifndef __SWAP_BROKEN
/*
* swap out some processes if we are below our free target.
* we need to unlock the page queues for this.
*/
if (uvmexp.free < uvmexp.freetarg && uvmexp.nswapdev != 0) {
uvmexp.pdswout++;
UVMHIST_LOG(pdhist," free %d < target %d: swapout",
uvmexp.free, uvmexp.freetarg, 0, 0);
uvm_unlock_pageq();
uvm_swapout_threads();
uvm_lock_pageq();
}
#endif
/*
* now we want to work on meeting our targets. first we work on our
* free target by converting inactive pages into free pages. then
* we work on meeting our inactive target by converting active pages
* to inactive ones.
*/
UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0);
/*
* alternate starting queue between swap and object based on the
* low bit of uvmexp.pdrevs (which we bump by one each call).
*/
pages_freed = uvmexp.pdfreed;
uvmpd_scan_inactive(&uvm.page_inactive);
pages_freed = uvmexp.pdfreed - pages_freed;
/*
* we have done the scan to get free pages. now we work on meeting
* our inactive target.
*/
inactive_shortage = uvmexp.inactarg - uvmexp.inactive;
/*
* detect if we're not going to be able to page anything out
* until we free some swap resources from active pages.
*/
swap_shortage = 0;
if (uvmexp.free < uvmexp.freetarg &&
uvmexp.swpginuse == uvmexp.swpages &&
uvmexp.swpgonly < uvmexp.swpages &&
pages_freed == 0) {
swap_shortage = uvmexp.freetarg - uvmexp.free;
}
UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%d swap_shortage=%d",
inactive_shortage, swap_shortage,0,0);
for (p = TAILQ_FIRST(&uvm.page_active);
p != NULL && (inactive_shortage > 0 || swap_shortage > 0);
p = nextpg) {
nextpg = TAILQ_NEXT(p, pageq);
if (p->flags & PG_BUSY) {
continue;
}
/*
* lock the page's owner.
*/
if (p->uobject != NULL) {
uobj = p->uobject;
slock = &uobj->vmobjlock;
if (!simple_lock_try(slock)) {
continue;
}
} else {
anon = p->uanon;
KASSERT(anon != NULL);
slock = &anon->an_lock;
if (!simple_lock_try(slock)) {
continue;
}
/* take over the page? */
if ((p->pqflags & PQ_ANON) == 0) {
KASSERT(p->loan_count > 0);
p->loan_count--;
p->pqflags |= PQ_ANON;
}
}
/*
* skip this page if it's busy.
*/
if ((p->flags & PG_BUSY) != 0) {
simple_unlock(slock);
continue;
}
/*
* if there's a shortage of swap, free any swap allocated
* to this page so that other pages can be paged out.
*/
if (swap_shortage > 0) {
if ((p->pqflags & PQ_ANON) && anon->an_swslot) {
uvm_swap_free(anon->an_swslot, 1);
anon->an_swslot = 0;
p->flags &= ~PG_CLEAN;
swap_shortage--;
} else if (p->pqflags & PQ_AOBJ) {
int slot = uao_set_swslot(uobj,
p->offset >> PAGE_SHIFT, 0);
if (slot) {
uvm_swap_free(slot, 1);
p->flags &= ~PG_CLEAN;
swap_shortage--;
}
}
}
/*
* if there's a shortage of inactive pages, deactivate.
*/
if (inactive_shortage > 0) {
/* no need to check wire_count as pg is "active" */
uvm_pagedeactivate(p);
uvmexp.pddeact++;
inactive_shortage--;
}
/*
* we're done with this page.
*/
simple_unlock(slock);
}
}