1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 */
25
26 /* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
27 /* All Rights Reserved */
28
29 /*
30 * University Copyright- Copyright (c) 1982, 1986, 1988
31 * The Regents of the University of California
32 * All Rights Reserved
33 *
34 * University Acknowledgment- Portions of this document are derived from
35 * software developed by the University of California, Berkeley, and its
36 * contributors.
37 */
38
39 #include <sys/types.h>
40 #include <sys/t_lock.h>
41 #include <sys/param.h>
42 #include <sys/buf.h>
43 #include <sys/uio.h>
44 #include <sys/proc.h>
45 #include <sys/systm.h>
46 #include <sys/mman.h>
47 #include <sys/cred.h>
48 #include <sys/vnode.h>
49 #include <sys/vm.h>
50 #include <sys/vmparam.h>
51 #include <sys/vtrace.h>
52 #include <sys/cmn_err.h>
53 #include <sys/cpuvar.h>
54 #include <sys/user.h>
55 #include <sys/kmem.h>
56 #include <sys/debug.h>
57 #include <sys/callb.h>
58 #include <sys/tnf_probe.h>
59 #include <sys/mem_cage.h>
60 #include <sys/time.h>
61
62 #include <vm/hat.h>
63 #include <vm/as.h>
64 #include <vm/seg.h>
65 #include <vm/page.h>
66 #include <vm/pvn.h>
67 #include <vm/seg_kmem.h>
68
69 static int checkpage(page_t *, int);
70
71 /*
72 * The following parameters control operation of the page replacement
73 * algorithm. They are initialized to 0, and then computed at boot time
74 * based on the size of the system. If they are patched non-zero in
75 * a loaded vmunix they are left alone and may thus be changed per system
76 * using adb on the loaded system.
77 */
78 pgcnt_t slowscan = 0;
79 pgcnt_t fastscan = 0;
80
81 static pgcnt_t handspreadpages = 0;
82 static int loopfraction = 2;
83 static pgcnt_t looppages;
84 static int min_percent_cpu = 4;
85 static int max_percent_cpu = 80;
86 static pgcnt_t maxfastscan = 0;
87 static pgcnt_t maxslowscan = 100;
88
89 pgcnt_t maxpgio = 0;
90 pgcnt_t minfree = 0;
91 pgcnt_t desfree = 0;
92 pgcnt_t lotsfree = 0;
93 pgcnt_t needfree = 0;
94 pgcnt_t throttlefree = 0;
95 pgcnt_t pageout_reserve = 0;
96
97 pgcnt_t deficit;
98 pgcnt_t nscan;
99 pgcnt_t desscan;
100
101 /*
102 * Values for min_pageout_ticks, max_pageout_ticks and pageout_ticks
103 * are the number of ticks in each wakeup cycle that gives the
104 * equivalent of some underlying %CPU duty cycle.
105 * When RATETOSCHEDPAGING is 4, and hz is 100, pageout_scanner is
106 * awakened every 25 clock ticks. So, converting from %CPU to ticks
107 * per wakeup cycle would be x% of 25, that is (x * 100) / 25.
108 * So, for example, 4% == 1 tick and 80% == 20 ticks.
109 *
110 * min_pageout_ticks:
111 * ticks/wakeup equivalent of min_percent_cpu.
112 *
113 * max_pageout_ticks:
114 * ticks/wakeup equivalent of max_percent_cpu.
115 *
116 * pageout_ticks:
117 * Number of clock ticks budgeted for each wakeup cycle.
118 * Computed each time around by schedpaging().
119 * Varies between min_pageout_ticks .. max_pageout_ticks,
120 * depending on memory pressure.
121 *
122 * pageout_lbolt:
123 * Timestamp of the last time pageout_scanner woke up and started
124 * (or resumed) scanning for not recently referenced pages.
125 */
126
127 static clock_t min_pageout_ticks;
128 static clock_t max_pageout_ticks;
129 static clock_t pageout_ticks;
130 static clock_t pageout_lbolt;
131
132 static uint_t reset_hands;
133
134 #define PAGES_POLL_MASK 1023
135
136 /*
137 * pageout_sample_lim:
138 * The limit on the number of samples needed to establish a value
139 * for new pageout parameters, fastscan, slowscan, and handspreadpages.
140 *
141 * pageout_sample_cnt:
142 * Current sample number. Once the sample gets large enough,
143 * set new values for handspreadpages, fastscan and slowscan.
144 *
145 * pageout_sample_pages:
146 * The accumulated number of pages scanned during sampling.
147 *
148 * pageout_sample_ticks:
149 * The accumulated clock ticks for the sample.
150 *
151 * pageout_rate:
152 * Rate in pages/nanosecond, computed at the end of sampling.
153 *
154 * pageout_new_spread:
155 * The new value to use for fastscan and handspreadpages.
156 * Calculated after enough samples have been taken.
157 */
158
159 typedef hrtime_t hrrate_t;
160
161 static uint64_t pageout_sample_lim = 4;
162 static uint64_t pageout_sample_cnt = 0;
163 static pgcnt_t pageout_sample_pages = 0;
164 static hrrate_t pageout_rate = 0;
165 static pgcnt_t pageout_new_spread = 0;
166
167 static clock_t pageout_cycle_ticks;
168 static hrtime_t sample_start, sample_end;
169 static hrtime_t pageout_sample_etime = 0;
170
171 /*
172 * Record number of times a pageout_scanner wakeup cycle finished because it
173 * timed out (exceeded its CPU budget), rather than because it visited
174 * its budgeted number of pages.
175 */
176 uint64_t pageout_timeouts = 0;
177
178 #ifdef VM_STATS
179 static struct pageoutvmstats_str {
180 ulong_t checkpage[3];
181 } pageoutvmstats;
182 #endif /* VM_STATS */
183
184 /*
185 * Threads waiting for free memory use this condition variable and lock until
186 * memory becomes available.
187 */
188 kmutex_t memavail_lock;
189 kcondvar_t memavail_cv;
190
191 /*
192 * The size of the clock loop.
193 */
194 #define LOOPPAGES total_pages
195
196 /*
197 * Set up the paging constants for the clock algorithm.
198 * Called after the system is initialized and the amount of memory
199 * and number of paging devices is known.
200 *
201 * lotsfree is 1/64 of memory, but at least 512K.
202 * desfree is 1/2 of lotsfree.
203 * minfree is 1/2 of desfree.
204 *
205 * Note: to revert to the paging algorithm of Solaris 2.4/2.5, set:
206 *
207 * lotsfree = btop(512K)
208 * desfree = btop(200K)
209 * minfree = btop(100K)
210 * throttlefree = INT_MIN
211 * max_percent_cpu = 4
212 */
213 void
214 setupclock(int recalc)
215 {
216
217 static spgcnt_t init_lfree, init_dfree, init_mfree;
218 static spgcnt_t init_tfree, init_preserve, init_mpgio;
219 static spgcnt_t init_mfscan, init_fscan, init_sscan, init_hspages;
220
221 looppages = LOOPPAGES;
222
223 /*
224 * setupclock can now be called to recalculate the paging
225 * parameters in the case of dynamic addition of memory.
226 * So to make sure we make the proper calculations, if such a
227 * situation should arise, we save away the initial values
228 * of each parameter so we can recall them when needed. This
229 * way we don't lose the settings an admin might have made
230 * through the /etc/system file.
231 */
232
233 if (!recalc) {
234 init_lfree = lotsfree;
235 init_dfree = desfree;
236 init_mfree = minfree;
237 init_tfree = throttlefree;
238 init_preserve = pageout_reserve;
239 init_mpgio = maxpgio;
240 init_mfscan = maxfastscan;
241 init_fscan = fastscan;
242 init_sscan = slowscan;
243 init_hspages = handspreadpages;
244 }
245
246 /*
247 * Set up thresholds for paging:
248 */
249
250 /*
251 * Lotsfree is threshold where paging daemon turns on.
252 */
253 if (init_lfree == 0 || init_lfree >= looppages)
254 lotsfree = MAX(looppages / 64, btop(512 * 1024));
255 else
256 lotsfree = init_lfree;
257
258 /*
259 * Desfree is amount of memory desired free.
260 * If less than this for extended period, start swapping.
261 */
262 if (init_dfree == 0 || init_dfree >= lotsfree)
263 desfree = lotsfree / 2;
264 else
265 desfree = init_dfree;
266
267 /*
268 * Minfree is minimal amount of free memory which is tolerable.
269 */
270 if (init_mfree == 0 || init_mfree >= desfree)
271 minfree = desfree / 2;
272 else
273 minfree = init_mfree;
274
275 /*
276 * Throttlefree is the point at which we start throttling
277 * PG_WAIT requests until enough memory becomes available.
278 */
279 if (init_tfree == 0 || init_tfree >= desfree)
280 throttlefree = minfree;
281 else
282 throttlefree = init_tfree;
283
284 /*
285 * Pageout_reserve is the number of pages that we keep in
286 * stock for pageout's own use. Having a few such pages
287 * provides insurance against system deadlock due to
288 * pageout needing pages. When freemem < pageout_reserve,
289 * non-blocking allocations are denied to any threads
290 * other than pageout and sched. (At some point we might
291 * want to consider a per-thread flag like T_PUSHING_PAGES
292 * to indicate that a thread is part of the page-pushing
293 * dance (e.g. an interrupt thread) and thus is entitled
294 * to the same special dispensation we accord pageout.)
295 */
296 if (init_preserve == 0 || init_preserve >= throttlefree)
297 pageout_reserve = throttlefree / 2;
298 else
299 pageout_reserve = init_preserve;
300
301 /*
302 * Maxpgio thresholds how much paging is acceptable.
303 * This figures that 2/3 busy on an arm is all that is
304 * tolerable for paging. We assume one operation per disk rev.
305 *
306 * XXX - Does not account for multiple swap devices.
307 */
308 if (init_mpgio == 0)
309 maxpgio = (DISKRPM * 2) / 3;
310 else
311 maxpgio = init_mpgio;
312
313 /*
314 * The clock scan rate varies between fastscan and slowscan
315 * based on the amount of free memory available. Fastscan
316 * rate should be set based on the number pages that can be
317 * scanned per sec using ~10% of processor time. Since this
318 * value depends on the processor, MMU, Mhz etc., it is
319 * difficult to determine it in a generic manner for all
320 * architectures.
321 *
322 * Instead of trying to determine the number of pages scanned
323 * per sec for every processor, fastscan is set to be the smaller
324 * of 1/2 of memory or MAXHANDSPREADPAGES and the sampling
325 * time is limited to ~4% of processor time.
326 *
327 * Setting fastscan to be 1/2 of memory allows pageout to scan
328 * all of memory in ~2 secs. This implies that user pages not
329 * accessed within 1 sec (assuming, handspreadpages == fastscan)
330 * can be reclaimed when free memory is very low. Stealing pages
331 * not accessed within 1 sec seems reasonable and ensures that
332 * active user processes don't thrash.
333 *
334 * Smaller values of fastscan result in scanning fewer pages
335 * every second and consequently pageout may not be able to free
336 * sufficient memory to maintain the minimum threshold. Larger
337 * values of fastscan result in scanning a lot more pages which
338 * could lead to thrashing and higher CPU usage.
339 *
340 * Fastscan needs to be limited to a maximum value and should not
341 * scale with memory to prevent pageout from consuming too much
342 * time for scanning on slow CPU's and avoid thrashing, as a
343 * result of scanning too many pages, on faster CPU's.
344 * The value of 64 Meg was chosen for MAXHANDSPREADPAGES
345 * (the upper bound for fastscan) based on the average number
346 * of pages that can potentially be scanned in ~1 sec (using ~4%
347 * of the CPU) on some of the following machines that currently
348 * run Solaris 2.x:
349 *
350 * average memory scanned in ~1 sec
351 *
352 * 25 Mhz SS1+: 23 Meg
353 * LX: 37 Meg
354 * 50 Mhz SC2000: 68 Meg
355 *
356 * 40 Mhz 486: 26 Meg
357 * 66 Mhz 486: 42 Meg
358 *
359 * When free memory falls just below lotsfree, the scan rate
360 * goes from 0 to slowscan (i.e., pageout starts running). This
361 * transition needs to be smooth and is achieved by ensuring that
362 * pageout scans a small number of pages to satisfy the transient
363 * memory demand. This is set to not exceed 100 pages/sec (25 per
364 * wakeup) since scanning that many pages has no noticible impact
365 * on system performance.
366 *
367 * In addition to setting fastscan and slowscan, pageout is
368 * limited to using ~4% of the CPU. This results in increasing
369 * the time taken to scan all of memory, which in turn means that
370 * user processes have a better opportunity of preventing their
371 * pages from being stolen. This has a positive effect on
372 * interactive and overall system performance when memory demand
373 * is high.
374 *
375 * Thus, the rate at which pages are scanned for replacement will
376 * vary linearly between slowscan and the number of pages that
377 * can be scanned using ~4% of processor time instead of varying
378 * linearly between slowscan and fastscan.
379 *
380 * Also, the processor time used by pageout will vary from ~1%
381 * at slowscan to ~4% at fastscan instead of varying between
382 * ~1% at slowscan and ~10% at fastscan.
383 *
384 * The values chosen for the various VM parameters (fastscan,
385 * handspreadpages, etc) are not universally true for all machines,
386 * but appear to be a good rule of thumb for the machines we've
387 * tested. They have the following ranges:
388 *
389 * cpu speed: 20 to 70 Mhz
390 * page size: 4K to 8K
391 * memory size: 16M to 5G
392 * page scan rate: 4000 - 17400 4K pages per sec
393 *
394 * The values need to be re-examined for machines which don't
395 * fall into the various ranges (e.g., slower or faster CPUs,
396 * smaller or larger pagesizes etc) shown above.
397 *
398 * On an MP machine, pageout is often unable to maintain the
399 * minimum paging thresholds under heavy load. This is due to
400 * the fact that user processes running on other CPU's can be
401 * dirtying memory at a much faster pace than pageout can find
402 * pages to free. The memory demands could be met by enabling
403 * more than one CPU to run the clock algorithm in such a manner
404 * that the various clock hands don't overlap. This also makes
405 * it more difficult to determine the values for fastscan, slowscan
406 * and handspreadpages.
407 *
408 * The swapper is currently used to free up memory when pageout
409 * is unable to meet memory demands by swapping out processes.
410 * In addition to freeing up memory, swapping also reduces the
411 * demand for memory by preventing user processes from running
412 * and thereby consuming memory.
413 */
414 if (init_mfscan == 0) {
415 if (pageout_new_spread != 0)
416 maxfastscan = pageout_new_spread;
417 else
418 maxfastscan = MAXHANDSPREADPAGES;
419 } else {
420 maxfastscan = init_mfscan;
421 }
422 if (init_fscan == 0)
423 fastscan = MIN(looppages / loopfraction, maxfastscan);
424 else
425 fastscan = init_fscan;
426 if (fastscan > looppages / loopfraction)
427 fastscan = looppages / loopfraction;
428
429 /*
430 * Set slow scan time to 1/10 the fast scan time, but
431 * not to exceed maxslowscan.
432 */
433 if (init_sscan == 0)
434 slowscan = MIN(fastscan / 10, maxslowscan);
435 else
436 slowscan = init_sscan;
437 if (slowscan > fastscan / 2)
438 slowscan = fastscan / 2;
439
440 /*
441 * Handspreadpages is distance (in pages) between front and back
442 * pageout daemon hands. The amount of time to reclaim a page
443 * once pageout examines it increases with this distance and
444 * decreases as the scan rate rises. It must be < the amount
445 * of pageable memory.
446 *
447 * Since pageout is limited to ~4% of the CPU, setting handspreadpages
448 * to be "fastscan" results in the front hand being a few secs
449 * (varies based on the processor speed) ahead of the back hand
450 * at fastscan rates. This distance can be further reduced, if
451 * necessary, by increasing the processor time used by pageout
452 * to be more than ~4% and preferrably not more than ~10%.
453 *
454 * As a result, user processes have a much better chance of
455 * referencing their pages before the back hand examines them.
456 * This also significantly lowers the number of reclaims from
457 * the freelist since pageout does not end up freeing pages which
458 * may be referenced a sec later.
459 */
460 if (init_hspages == 0)
461 handspreadpages = fastscan;
462 else
463 handspreadpages = init_hspages;
464
465 /*
466 * Make sure that back hand follows front hand by at least
467 * 1/RATETOSCHEDPAGING seconds. Without this test, it is possible
468 * for the back hand to look at a page during the same wakeup of
469 * the pageout daemon in which the front hand cleared its ref bit.
470 */
471 if (handspreadpages >= looppages)
472 handspreadpages = looppages - 1;
473
474 /*
475 * If we have been called to recalculate the parameters,
476 * set a flag to re-evaluate the clock hand pointers.
477 */
478 if (recalc)
479 reset_hands = 1;
480 }
481
482 /*
483 * Pageout scheduling.
484 *
485 * Schedpaging controls the rate at which the page out daemon runs by
486 * setting the global variables nscan and desscan RATETOSCHEDPAGING
487 * times a second. Nscan records the number of pages pageout has examined
488 * in its current pass; schedpaging resets this value to zero each time
489 * it runs. Desscan records the number of pages pageout should examine
490 * in its next pass; schedpaging sets this value based on the amount of
491 * currently available memory.
492 */
493
494 #define RATETOSCHEDPAGING 4 /* hz that is */
495
496 static kmutex_t pageout_mutex; /* held while pageout or schedpaging running */
497
498 /*
499 * Pool of available async pageout putpage requests.
500 */
501 static struct async_reqs *push_req;
502 static struct async_reqs *req_freelist; /* available req structs */
503 static struct async_reqs *push_list; /* pending reqs */
504 static kmutex_t push_lock; /* protects req pool */
505 static kcondvar_t push_cv;
506
507 static int async_list_size = 256; /* number of async request structs */
508
509 static void pageout_scanner(void);
510
511 /*
512 * If a page is being shared more than "po_share" times
513 * then leave it alone- don't page it out.
514 */
515 #define MIN_PO_SHARE (8)
516 #define MAX_PO_SHARE ((MIN_PO_SHARE) << 24)
517 ulong_t po_share = MIN_PO_SHARE;
518
519 /*
520 * Schedule rate for paging.
521 * Rate is linear interpolation between
522 * slowscan with lotsfree and fastscan when out of memory.
523 */
524 static void
525 schedpaging(void *arg)
526 {
527 spgcnt_t vavail;
528
529 if (freemem < lotsfree + needfree + kmem_reapahead)
530 kmem_reap();
531
532 if (freemem < lotsfree + needfree)
533 seg_preap();
534
535 if (kcage_on && (kcage_freemem < kcage_desfree || kcage_needfree))
536 kcage_cageout_wakeup();
537
538 if (mutex_tryenter(&pageout_mutex)) {
539 /* pageout() not running */
540 nscan = 0;
541 vavail = freemem - deficit;
542 if (pageout_new_spread != 0)
543 vavail -= needfree;
544 if (vavail < 0)
545 vavail = 0;
546 if (vavail > lotsfree)
547 vavail = lotsfree;
548
549 /*
550 * Fix for 1161438 (CRS SPR# 73922). All variables
551 * in the original calculation for desscan were 32 bit signed
552 * ints. As freemem approaches 0x0 on a system with 1 Gig or
553 * more of memory, the calculation can overflow. When this
554 * happens, desscan becomes negative and pageout_scanner()
555 * stops paging out.
556 */
557 if ((needfree) && (pageout_new_spread == 0)) {
558 /*
559 * If we've not yet collected enough samples to
560 * calculate a spread, use the old logic of kicking
561 * into high gear anytime needfree is non-zero.
562 */
563 desscan = fastscan / RATETOSCHEDPAGING;
564 } else {
565 /*
566 * Once we've calculated a spread based on system
567 * memory and usage, just treat needfree as another
568 * form of deficit.
569 */
570 spgcnt_t faststmp, slowstmp, result;
571
572 slowstmp = slowscan * vavail;
573 faststmp = fastscan * (lotsfree - vavail);
574 result = (slowstmp + faststmp) /
575 nz(lotsfree) / RATETOSCHEDPAGING;
576 desscan = (pgcnt_t)result;
577 }
578
579 pageout_ticks = min_pageout_ticks + (lotsfree - vavail) *
580 (max_pageout_ticks - min_pageout_ticks) / nz(lotsfree);
581
582 if (freemem < lotsfree + needfree ||
583 pageout_sample_cnt < pageout_sample_lim) {
584 TRACE_1(TR_FAC_VM, TR_PAGEOUT_CV_SIGNAL,
585 "pageout_cv_signal:freemem %ld", freemem);
586 cv_signal(&proc_pageout->p_cv);
587 } else {
588 /*
589 * There are enough free pages, no need to
590 * kick the scanner thread. And next time
591 * around, keep more of the `highly shared'
592 * pages.
593 */
594 cv_signal_pageout();
595 if (po_share > MIN_PO_SHARE) {
596 po_share >>= 1;
597 }
598 }
599 mutex_exit(&pageout_mutex);
600 }
601
602 /*
603 * Signal threads waiting for available memory.
604 * NOTE: usually we need to grab memavail_lock before cv_broadcast, but
605 * in this case it is not needed - the waiters will be waken up during
606 * the next invocation of this function.
607 */
608 if (kmem_avail() > 0)
609 cv_broadcast(&memavail_cv);
610
611 (void) timeout(schedpaging, arg, hz / RATETOSCHEDPAGING);
612 }
613
614 pgcnt_t pushes;
615 ulong_t push_list_size; /* # of requests on pageout queue */
616
617 #define FRONT 1
618 #define BACK 2
619
620 int dopageout = 1; /* must be non-zero to turn page stealing on */
621
622 /*
623 * The page out daemon, which runs as process 2.
624 *
625 * As long as there are at least lotsfree pages,
626 * this process is not run. When the number of free
627 * pages stays in the range desfree to lotsfree,
628 * this daemon runs through the pages in the loop
629 * at a rate determined in schedpaging(). Pageout manages
630 * two hands on the clock. The front hand moves through
631 * memory, clearing the reference bit,
632 * and stealing pages from procs that are over maxrss.
633 * The back hand travels a distance behind the front hand,
634 * freeing the pages that have not been referenced in the time
635 * since the front hand passed. If modified, they are pushed to
636 * swap before being freed.
637 *
638 * There are 2 threads that act on behalf of the pageout process.
639 * One thread scans pages (pageout_scanner) and frees them up if
640 * they don't require any VOP_PUTPAGE operation. If a page must be
641 * written back to its backing store, the request is put on a list
642 * and the other (pageout) thread is signaled. The pageout thread
643 * grabs VOP_PUTPAGE requests from the list, and processes them.
644 * Some filesystems may require resources for the VOP_PUTPAGE
645 * operations (like memory) and hence can block the pageout
646 * thread, but the scanner thread can still operate. There is still
647 * no guarantee that memory deadlocks cannot occur.
648 *
649 * For now, this thing is in very rough form.
650 */
651 void
652 pageout()
653 {
654 struct async_reqs *arg;
655 pri_t pageout_pri;
656 int i;
657 pgcnt_t max_pushes;
658 callb_cpr_t cprinfo;
659
660 proc_pageout = ttoproc(curthread);
661 proc_pageout->p_cstime = 0;
662 proc_pageout->p_stime = 0;
663 proc_pageout->p_cutime = 0;
664 proc_pageout->p_utime = 0;
665 bcopy("pageout", PTOU(curproc)->u_psargs, 8);
666 bcopy("pageout", PTOU(curproc)->u_comm, 7);
667
668 /*
669 * Create pageout scanner thread
670 */
671 mutex_init(&pageout_mutex, NULL, MUTEX_DEFAULT, NULL);
672 mutex_init(&push_lock, NULL, MUTEX_DEFAULT, NULL);
673
674 /*
675 * Allocate and initialize the async request structures
676 * for pageout.
677 */
678 push_req = (struct async_reqs *)
679 kmem_zalloc(async_list_size * sizeof (struct async_reqs), KM_SLEEP);
680
681 req_freelist = push_req;
682 for (i = 0; i < async_list_size - 1; i++)
683 push_req[i].a_next = &push_req[i + 1];
684
685 pageout_pri = curthread->t_pri;
686
687 /* Create the pageout scanner thread. */
688 (void) lwp_kernel_create(proc_pageout, pageout_scanner, NULL, TS_RUN,
689 pageout_pri - 1);
690
691 /*
692 * kick off pageout scheduler.
693 */
694 schedpaging(NULL);
695
696 /*
697 * Create kernel cage thread.
698 * The kernel cage thread is started under the pageout process
699 * to take advantage of the less restricted page allocation
700 * in page_create_throttle().
701 */
702 kcage_cageout_init();
703
704 /*
705 * Limit pushes to avoid saturating pageout devices.
706 */
707 max_pushes = maxpgio / RATETOSCHEDPAGING;
708 CALLB_CPR_INIT(&cprinfo, &push_lock, callb_generic_cpr, "pageout");
709
710 for (;;) {
711 mutex_enter(&push_lock);
712
713 while ((arg = push_list) == NULL || pushes > max_pushes) {
714 CALLB_CPR_SAFE_BEGIN(&cprinfo);
715 cv_wait(&push_cv, &push_lock);
716 pushes = 0;
717 CALLB_CPR_SAFE_END(&cprinfo, &push_lock);
718 }
719 push_list = arg->a_next;
720 arg->a_next = NULL;
721 mutex_exit(&push_lock);
722
723 if (VOP_PUTPAGE(arg->a_vp, (offset_t)arg->a_off,
724 arg->a_len, arg->a_flags, arg->a_cred, NULL) == 0) {
725 pushes++;
726 }
727
728 /* vp held by checkpage() */
729 VN_RELE(arg->a_vp);
730
731 mutex_enter(&push_lock);
732 arg->a_next = req_freelist; /* back on freelist */
733 req_freelist = arg;
734 push_list_size--;
735 mutex_exit(&push_lock);
736 }
737 }
738
739 /*
740 * Kernel thread that scans pages looking for ones to free
741 */
742 static void
743 pageout_scanner(void)
744 {
745 struct page *fronthand, *backhand;
746 uint_t count;
747 callb_cpr_t cprinfo;
748 pgcnt_t nscan_limit;
749 pgcnt_t pcount;
750
751 CALLB_CPR_INIT(&cprinfo, &pageout_mutex, callb_generic_cpr, "poscan");
752 mutex_enter(&pageout_mutex);
753
754 /*
755 * The restart case does not attempt to point the hands at roughly
756 * the right point on the assumption that after one circuit things
757 * will have settled down - and restarts shouldn't be that often.
758 */
759
760 /*
761 * Set the two clock hands to be separated by a reasonable amount,
762 * but no more than 360 degrees apart.
763 */
764 backhand = page_first();
765 if (handspreadpages >= total_pages)
766 fronthand = page_nextn(backhand, total_pages - 1);
767 else
768 fronthand = page_nextn(backhand, handspreadpages);
769
770 min_pageout_ticks = MAX(1,
771 ((hz * min_percent_cpu) / 100) / RATETOSCHEDPAGING);
772 max_pageout_ticks = MAX(min_pageout_ticks,
773 ((hz * max_percent_cpu) / 100) / RATETOSCHEDPAGING);
774
775 loop:
776 cv_signal_pageout();
777
778 CALLB_CPR_SAFE_BEGIN(&cprinfo);
779 cv_wait(&proc_pageout->p_cv, &pageout_mutex);
780 CALLB_CPR_SAFE_END(&cprinfo, &pageout_mutex);
781
782 if (!dopageout)
783 goto loop;
784
785 if (reset_hands) {
786 reset_hands = 0;
787
788 backhand = page_first();
789 if (handspreadpages >= total_pages)
790 fronthand = page_nextn(backhand, total_pages - 1);
791 else
792 fronthand = page_nextn(backhand, handspreadpages);
793 }
794
795 CPU_STATS_ADDQ(CPU, vm, pgrrun, 1);
796 count = 0;
797
798 TRACE_4(TR_FAC_VM, TR_PAGEOUT_START,
799 "pageout_start:freemem %ld lotsfree %ld nscan %ld desscan %ld",
800 freemem, lotsfree, nscan, desscan);
801
802 /* Kernel probe */
803 TNF_PROBE_2(pageout_scan_start, "vm pagedaemon", /* CSTYLED */,
804 tnf_ulong, pages_free, freemem, tnf_ulong, pages_needed, needfree);
805
806 pcount = 0;
807 if (pageout_sample_cnt < pageout_sample_lim) {
808 nscan_limit = total_pages;
809 } else {
810 nscan_limit = desscan;
811 }
812 pageout_lbolt = ddi_get_lbolt();
813 sample_start = gethrtime();
814
815 /*
816 * Scan the appropriate number of pages for a single duty cycle.
817 * However, stop scanning as soon as there is enough free memory.
818 * For a short while, we will be sampling the performance of the
819 * scanner and need to keep running just to get sample data, in
820 * which case we keep going and don't pay attention to whether
821 * or not there is enough free memory.
822 */
823
824 while (nscan < nscan_limit && (freemem < lotsfree + needfree ||
825 pageout_sample_cnt < pageout_sample_lim)) {
826 int rvfront, rvback;
827
828 /*
829 * Check to see if we have exceeded our %CPU budget
830 * for this wakeup, but not on every single page visited,
831 * just every once in a while.
832 */
833 if ((pcount & PAGES_POLL_MASK) == PAGES_POLL_MASK) {
834 pageout_cycle_ticks = ddi_get_lbolt() - pageout_lbolt;
835 if (pageout_cycle_ticks >= pageout_ticks) {
836 ++pageout_timeouts;
837 break;
838 }
839 }
840
841 /*
842 * If checkpage manages to add a page to the free list,
843 * we give ourselves another couple of trips around the loop.
844 */
845 if ((rvfront = checkpage(fronthand, FRONT)) == 1)
846 count = 0;
847 if ((rvback = checkpage(backhand, BACK)) == 1)
848 count = 0;
849
850 ++pcount;
851
852 /*
853 * protected by pageout_mutex instead of cpu_stat_lock
854 */
855 CPU_STATS_ADDQ(CPU, vm, scan, 1);
856
857 /*
858 * Don't include ineligible pages in the number scanned.
859 */
860 if (rvfront != -1 || rvback != -1)
861 nscan++;
862
863 backhand = page_next(backhand);
864
865 /*
866 * backhand update and wraparound check are done separately
867 * because lint barks when it finds an empty "if" body
868 */
869
870 if ((fronthand = page_next(fronthand)) == page_first()) {
871 TRACE_2(TR_FAC_VM, TR_PAGEOUT_HAND_WRAP,
872 "pageout_hand_wrap:freemem %ld whichhand %d",
873 freemem, FRONT);
874
875 /*
876 * protected by pageout_mutex instead of cpu_stat_lock
877 */
878 CPU_STATS_ADDQ(CPU, vm, rev, 1);
879 if (++count > 1) {
880 /*
881 * Extremely unlikely, but it happens.
882 * We went around the loop at least once
883 * and didn't get far enough.
884 * If we are still skipping `highly shared'
885 * pages, skip fewer of them. Otherwise,
886 * give up till the next clock tick.
887 */
888 if (po_share < MAX_PO_SHARE) {
889 po_share <<= 1;
890 } else {
891 /*
892 * Really a "goto loop", but
893 * if someone is TRACing or
894 * TNF_PROBE_ing, at least
895 * make records to show
896 * where we are.
897 */
898 break;
899 }
900 }
901 }
902 }
903
904 sample_end = gethrtime();
905
906 TRACE_5(TR_FAC_VM, TR_PAGEOUT_END,
907 "pageout_end:freemem %ld lots %ld nscan %ld des %ld count %u",
908 freemem, lotsfree, nscan, desscan, count);
909
910 /* Kernel probe */
911 TNF_PROBE_2(pageout_scan_end, "vm pagedaemon", /* CSTYLED */,
912 tnf_ulong, pages_scanned, nscan, tnf_ulong, pages_free, freemem);
913
914 if (pageout_sample_cnt < pageout_sample_lim) {
915 pageout_sample_pages += pcount;
916 pageout_sample_etime += sample_end - sample_start;
917 ++pageout_sample_cnt;
918 }
919 if (pageout_sample_cnt >= pageout_sample_lim &&
920 pageout_new_spread == 0) {
921 pageout_rate = (hrrate_t)pageout_sample_pages *
922 (hrrate_t)(NANOSEC) / pageout_sample_etime;
923 pageout_new_spread = pageout_rate / 10;
924 setupclock(1);
925 }
926
927 goto loop;
928 }
929
930 /*
931 * Look at the page at hand. If it is locked (e.g., for physical i/o),
932 * system (u., page table) or free, then leave it alone. Otherwise,
933 * if we are running the front hand, turn off the page's reference bit.
934 * If the proc is over maxrss, we take it. If running the back hand,
935 * check whether the page has been reclaimed. If not, free the page,
936 * pushing it to disk first if necessary.
937 *
938 * Return values:
939 * -1 if the page is not a candidate at all,
940 * 0 if not freed, or
941 * 1 if we freed it.
942 */
943 static int
944 checkpage(struct page *pp, int whichhand)
945 {
946 int ppattr;
947 int isfs = 0;
948 int isexec = 0;
949 int pagesync_flag;
950
951 /*
952 * Skip pages:
953 * - associated with the kernel vnode since
954 * they are always "exclusively" locked.
955 * - that are free
956 * - that are shared more than po_share'd times
957 * - its already locked
958 *
959 * NOTE: These optimizations assume that reads are atomic.
960 */
961
962 if (PP_ISKAS(pp) || PAGE_LOCKED(pp) || PP_ISFREE(pp) ||
963 pp->p_lckcnt != 0 || pp->p_cowcnt != 0 ||
964 hat_page_checkshare(pp, po_share)) {
965 return (-1);
966 }
967
968 if (!page_trylock(pp, SE_EXCL)) {
969 /*
970 * Skip the page if we can't acquire the "exclusive" lock.
971 */
972 return (-1);
973 } else if (PP_ISFREE(pp)) {
974 /*
975 * It became free between the above check and our actually
976 * locking the page. Oh, well there will be other pages.
977 */
978 page_unlock(pp);
979 return (-1);
980 }
981
982 /*
983 * Reject pages that cannot be freed. The page_struct_lock
984 * need not be acquired to examine these
985 * fields since the page has an "exclusive" lock.
986 */
987 if (pp->p_lckcnt != 0 || pp->p_cowcnt != 0) {
988 page_unlock(pp);
989 return (-1);
990 }
991
992 /*
993 * Maintain statistics for what we are freeing
994 */
995
996 if (pp->p_vnode != NULL) {
997 if (pp->p_vnode->v_flag & VVMEXEC)
998 isexec = 1;
999
1000 if (!IS_SWAPFSVP(pp->p_vnode))
1001 isfs = 1;
1002 }
1003
1004 /*
1005 * Turn off REF and MOD bits with the front hand.
1006 * The back hand examines the REF bit and always considers
1007 * SHARED pages as referenced.
1008 */
1009 if (whichhand == FRONT)
1010 pagesync_flag = HAT_SYNC_ZERORM;
1011 else
1012 pagesync_flag = HAT_SYNC_DONTZERO | HAT_SYNC_STOPON_REF |
1013 HAT_SYNC_STOPON_SHARED;
1014
1015 ppattr = hat_pagesync(pp, pagesync_flag);
1016
1017 recheck:
1018 /*
1019 * If page is referenced; make unreferenced but reclaimable.
1020 * If this page is not referenced, then it must be reclaimable
1021 * and we can add it to the free list.
1022 */
1023 if (ppattr & P_REF) {
1024 TRACE_2(TR_FAC_VM, TR_PAGEOUT_ISREF,
1025 "pageout_isref:pp %p whichhand %d", pp, whichhand);
1026 if (whichhand == FRONT) {
1027 /*
1028 * Checking of rss or madvise flags needed here...
1029 *
1030 * If not "well-behaved", fall through into the code
1031 * for not referenced.
1032 */
1033 hat_clrref(pp);
1034 }
1035 /*
1036 * Somebody referenced the page since the front
1037 * hand went by, so it's not a candidate for
1038 * freeing up.
1039 */
1040 page_unlock(pp);
1041 return (0);
1042 }
1043
1044 VM_STAT_ADD(pageoutvmstats.checkpage[0]);
1045
1046 /*
1047 * If large page, attempt to demote it. If successfully demoted,
1048 * retry the checkpage.
1049 */
1050 if (pp->p_szc != 0) {
1051 if (!page_try_demote_pages(pp)) {
1052 VM_STAT_ADD(pageoutvmstats.checkpage[1]);
1053 page_unlock(pp);
1054 return (-1);
1055 }
1056 ASSERT(pp->p_szc == 0);
1057 VM_STAT_ADD(pageoutvmstats.checkpage[2]);
1058 /*
1059 * since page_try_demote_pages() could have unloaded some
1060 * mappings it makes sense to reload ppattr.
1061 */
1062 ppattr = hat_page_getattr(pp, P_MOD | P_REF);
1063 }
1064
1065 /*
1066 * If the page is currently dirty, we have to arrange
1067 * to have it cleaned before it can be freed.
1068 *
1069 * XXX - ASSERT(pp->p_vnode != NULL);
1070 */
1071 if ((ppattr & P_MOD) && pp->p_vnode) {
1072 struct vnode *vp = pp->p_vnode;
1073 u_offset_t offset = pp->p_offset;
1074
1075 /*
1076 * XXX - Test for process being swapped out or about to exit?
1077 * [Can't get back to process(es) using the page.]
1078 */
1079
1080 /*
1081 * Hold the vnode before releasing the page lock to
1082 * prevent it from being freed and re-used by some
1083 * other thread.
1084 */
1085 VN_HOLD(vp);
1086 page_unlock(pp);
1087
1088 /*
1089 * Queue i/o request for the pageout thread.
1090 */
1091 if (!queue_io_request(vp, offset)) {
1092 VN_RELE(vp);
1093 return (0);
1094 }
1095 return (1);
1096 }
1097
1098 /*
1099 * Now we unload all the translations,
1100 * and put the page back on to the free list.
1101 * If the page was used (referenced or modified) after
1102 * the pagesync but before it was unloaded we catch it
1103 * and handle the page properly.
1104 */
1105 TRACE_2(TR_FAC_VM, TR_PAGEOUT_FREE,
1106 "pageout_free:pp %p whichhand %d", pp, whichhand);
1107 (void) hat_pageunload(pp, HAT_FORCE_PGUNLOAD);
1108 ppattr = hat_page_getattr(pp, P_MOD | P_REF);
1109 if ((ppattr & P_REF) || ((ppattr & P_MOD) && pp->p_vnode))
1110 goto recheck;
1111
1112 /*LINTED: constant in conditional context*/
1113 VN_DISPOSE(pp, B_FREE, 0, kcred);
1114
1115 CPU_STATS_ADD_K(vm, dfree, 1);
1116
1117 if (isfs) {
1118 if (isexec) {
1119 CPU_STATS_ADD_K(vm, execfree, 1);
1120 } else {
1121 CPU_STATS_ADD_K(vm, fsfree, 1);
1122 }
1123 } else {
1124 CPU_STATS_ADD_K(vm, anonfree, 1);
1125 }
1126
1127 return (1); /* freed a page! */
1128 }
1129
1130 /*
1131 * Queue async i/o request from pageout_scanner and segment swapout
1132 * routines on one common list. This ensures that pageout devices (swap)
1133 * are not saturated by pageout_scanner or swapout requests.
1134 * The pageout thread empties this list by initiating i/o operations.
1135 */
1136 int
1137 queue_io_request(vnode_t *vp, u_offset_t off)
1138 {
1139 struct async_reqs *arg;
1140
1141 /*
1142 * If we cannot allocate an async request struct,
1143 * skip this page.
1144 */
1145 mutex_enter(&push_lock);
1146 if ((arg = req_freelist) == NULL) {
1147 mutex_exit(&push_lock);
1148 return (0);
1149 }
1150 req_freelist = arg->a_next; /* adjust freelist */
1151 push_list_size++;
1152
1153 arg->a_vp = vp;
1154 arg->a_off = off;
1155 arg->a_len = PAGESIZE;
1156 arg->a_flags = B_ASYNC | B_FREE;
1157 arg->a_cred = kcred; /* always held */
1158
1159 /*
1160 * Add to list of pending write requests.
1161 */
1162 arg->a_next = push_list;
1163 push_list = arg;
1164
1165 if (req_freelist == NULL) {
1166 /*
1167 * No free async requests left. The lock is held so we
1168 * might as well signal the pusher thread now.
1169 */
1170 cv_signal(&push_cv);
1171 }
1172 mutex_exit(&push_lock);
1173 return (1);
1174 }
1175
1176 /*
1177 * Wakeup pageout to initiate i/o if push_list is not empty.
1178 */
1179 void
1180 cv_signal_pageout()
1181 {
1182 if (push_list != NULL) {
1183 mutex_enter(&push_lock);
1184 cv_signal(&push_cv);
1185 mutex_exit(&push_lock);
1186 }
1187 }