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CommitLineData
1da177e4
LT
1/*
2 * linux/mm/vmscan.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 *
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
12 */
13
14#include <linux/mm.h>
15#include <linux/module.h>
16#include <linux/slab.h>
17#include <linux/kernel_stat.h>
18#include <linux/swap.h>
19#include <linux/pagemap.h>
20#include <linux/init.h>
21#include <linux/highmem.h>
e129b5c2 22#include <linux/vmstat.h>
1da177e4
LT
23#include <linux/file.h>
24#include <linux/writeback.h>
25#include <linux/blkdev.h>
26#include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28#include <linux/mm_inline.h>
29#include <linux/pagevec.h>
30#include <linux/backing-dev.h>
31#include <linux/rmap.h>
32#include <linux/topology.h>
33#include <linux/cpu.h>
34#include <linux/cpuset.h>
35#include <linux/notifier.h>
36#include <linux/rwsem.h>
248a0301 37#include <linux/delay.h>
3218ae14 38#include <linux/kthread.h>
7dfb7103 39#include <linux/freezer.h>
66e1707b 40#include <linux/memcontrol.h>
873b4771 41#include <linux/delayacct.h>
af936a16 42#include <linux/sysctl.h>
1da177e4
LT
43
44#include <asm/tlbflush.h>
45#include <asm/div64.h>
46
47#include <linux/swapops.h>
48
0f8053a5
NP
49#include "internal.h"
50
1da177e4 51struct scan_control {
1da177e4
LT
52 /* Incremented by the number of inactive pages that were scanned */
53 unsigned long nr_scanned;
54
a79311c1
RR
55 /* Number of pages freed so far during a call to shrink_zones() */
56 unsigned long nr_reclaimed;
57
1da177e4 58 /* This context's GFP mask */
6daa0e28 59 gfp_t gfp_mask;
1da177e4
LT
60
61 int may_writepage;
62
a6dc60f8
JW
63 /* Can mapped pages be reclaimed? */
64 int may_unmap;
f1fd1067 65
2e2e4259
KM
66 /* Can pages be swapped as part of reclaim? */
67 int may_swap;
68
1da177e4
LT
69 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
70 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
71 * In this context, it doesn't matter that we scan the
72 * whole list at once. */
73 int swap_cluster_max;
d6277db4
RW
74
75 int swappiness;
408d8544
NP
76
77 int all_unreclaimable;
5ad333eb
AW
78
79 int order;
66e1707b
BS
80
81 /* Which cgroup do we reclaim from */
82 struct mem_cgroup *mem_cgroup;
83
327c0e96
KH
84 /*
85 * Nodemask of nodes allowed by the caller. If NULL, all nodes
86 * are scanned.
87 */
88 nodemask_t *nodemask;
89
66e1707b
BS
90 /* Pluggable isolate pages callback */
91 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
92 unsigned long *scanned, int order, int mode,
93 struct zone *z, struct mem_cgroup *mem_cont,
4f98a2fe 94 int active, int file);
1da177e4
LT
95};
96
1da177e4
LT
97#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
98
99#ifdef ARCH_HAS_PREFETCH
100#define prefetch_prev_lru_page(_page, _base, _field) \
101 do { \
102 if ((_page)->lru.prev != _base) { \
103 struct page *prev; \
104 \
105 prev = lru_to_page(&(_page->lru)); \
106 prefetch(&prev->_field); \
107 } \
108 } while (0)
109#else
110#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
111#endif
112
113#ifdef ARCH_HAS_PREFETCHW
114#define prefetchw_prev_lru_page(_page, _base, _field) \
115 do { \
116 if ((_page)->lru.prev != _base) { \
117 struct page *prev; \
118 \
119 prev = lru_to_page(&(_page->lru)); \
120 prefetchw(&prev->_field); \
121 } \
122 } while (0)
123#else
124#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
125#endif
126
127/*
128 * From 0 .. 100. Higher means more swappy.
129 */
130int vm_swappiness = 60;
bd1e22b8 131long vm_total_pages; /* The total number of pages which the VM controls */
1da177e4
LT
132
133static LIST_HEAD(shrinker_list);
134static DECLARE_RWSEM(shrinker_rwsem);
135
00f0b825 136#ifdef CONFIG_CGROUP_MEM_RES_CTLR
e72e2bd6 137#define scanning_global_lru(sc) (!(sc)->mem_cgroup)
91a45470 138#else
e72e2bd6 139#define scanning_global_lru(sc) (1)
91a45470
KH
140#endif
141
6e901571
KM
142static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
143 struct scan_control *sc)
144{
e72e2bd6 145 if (!scanning_global_lru(sc))
3e2f41f1
KM
146 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
147
6e901571
KM
148 return &zone->reclaim_stat;
149}
150
c9f299d9
KM
151static unsigned long zone_nr_pages(struct zone *zone, struct scan_control *sc,
152 enum lru_list lru)
153{
e72e2bd6 154 if (!scanning_global_lru(sc))
a3d8e054
KM
155 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
156
c9f299d9
KM
157 return zone_page_state(zone, NR_LRU_BASE + lru);
158}
159
160
1da177e4
LT
161/*
162 * Add a shrinker callback to be called from the vm
163 */
8e1f936b 164void register_shrinker(struct shrinker *shrinker)
1da177e4 165{
8e1f936b
RR
166 shrinker->nr = 0;
167 down_write(&shrinker_rwsem);
168 list_add_tail(&shrinker->list, &shrinker_list);
169 up_write(&shrinker_rwsem);
1da177e4 170}
8e1f936b 171EXPORT_SYMBOL(register_shrinker);
1da177e4
LT
172
173/*
174 * Remove one
175 */
8e1f936b 176void unregister_shrinker(struct shrinker *shrinker)
1da177e4
LT
177{
178 down_write(&shrinker_rwsem);
179 list_del(&shrinker->list);
180 up_write(&shrinker_rwsem);
1da177e4 181}
8e1f936b 182EXPORT_SYMBOL(unregister_shrinker);
1da177e4
LT
183
184#define SHRINK_BATCH 128
185/*
186 * Call the shrink functions to age shrinkable caches
187 *
188 * Here we assume it costs one seek to replace a lru page and that it also
189 * takes a seek to recreate a cache object. With this in mind we age equal
190 * percentages of the lru and ageable caches. This should balance the seeks
191 * generated by these structures.
192 *
183ff22b 193 * If the vm encountered mapped pages on the LRU it increase the pressure on
1da177e4
LT
194 * slab to avoid swapping.
195 *
196 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
197 *
198 * `lru_pages' represents the number of on-LRU pages in all the zones which
199 * are eligible for the caller's allocation attempt. It is used for balancing
200 * slab reclaim versus page reclaim.
b15e0905 201 *
202 * Returns the number of slab objects which we shrunk.
1da177e4 203 */
69e05944
AM
204unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
205 unsigned long lru_pages)
1da177e4
LT
206{
207 struct shrinker *shrinker;
69e05944 208 unsigned long ret = 0;
1da177e4
LT
209
210 if (scanned == 0)
211 scanned = SWAP_CLUSTER_MAX;
212
213 if (!down_read_trylock(&shrinker_rwsem))
b15e0905 214 return 1; /* Assume we'll be able to shrink next time */
1da177e4
LT
215
216 list_for_each_entry(shrinker, &shrinker_list, list) {
217 unsigned long long delta;
218 unsigned long total_scan;
8e1f936b 219 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
1da177e4
LT
220
221 delta = (4 * scanned) / shrinker->seeks;
ea164d73 222 delta *= max_pass;
1da177e4
LT
223 do_div(delta, lru_pages + 1);
224 shrinker->nr += delta;
ea164d73 225 if (shrinker->nr < 0) {
88c3bd70
DR
226 printk(KERN_ERR "shrink_slab: %pF negative objects to "
227 "delete nr=%ld\n",
228 shrinker->shrink, shrinker->nr);
ea164d73
AA
229 shrinker->nr = max_pass;
230 }
231
232 /*
233 * Avoid risking looping forever due to too large nr value:
234 * never try to free more than twice the estimate number of
235 * freeable entries.
236 */
237 if (shrinker->nr > max_pass * 2)
238 shrinker->nr = max_pass * 2;
1da177e4
LT
239
240 total_scan = shrinker->nr;
241 shrinker->nr = 0;
242
243 while (total_scan >= SHRINK_BATCH) {
244 long this_scan = SHRINK_BATCH;
245 int shrink_ret;
b15e0905 246 int nr_before;
1da177e4 247
8e1f936b
RR
248 nr_before = (*shrinker->shrink)(0, gfp_mask);
249 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
1da177e4
LT
250 if (shrink_ret == -1)
251 break;
b15e0905 252 if (shrink_ret < nr_before)
253 ret += nr_before - shrink_ret;
f8891e5e 254 count_vm_events(SLABS_SCANNED, this_scan);
1da177e4
LT
255 total_scan -= this_scan;
256
257 cond_resched();
258 }
259
260 shrinker->nr += total_scan;
261 }
262 up_read(&shrinker_rwsem);
b15e0905 263 return ret;
1da177e4
LT
264}
265
266/* Called without lock on whether page is mapped, so answer is unstable */
267static inline int page_mapping_inuse(struct page *page)
268{
269 struct address_space *mapping;
270
271 /* Page is in somebody's page tables. */
272 if (page_mapped(page))
273 return 1;
274
275 /* Be more reluctant to reclaim swapcache than pagecache */
276 if (PageSwapCache(page))
277 return 1;
278
279 mapping = page_mapping(page);
280 if (!mapping)
281 return 0;
282
283 /* File is mmap'd by somebody? */
284 return mapping_mapped(mapping);
285}
286
287static inline int is_page_cache_freeable(struct page *page)
288{
266cf658 289 return page_count(page) - !!page_has_private(page) == 2;
1da177e4
LT
290}
291
292static int may_write_to_queue(struct backing_dev_info *bdi)
293{
930d9152 294 if (current->flags & PF_SWAPWRITE)
1da177e4
LT
295 return 1;
296 if (!bdi_write_congested(bdi))
297 return 1;
298 if (bdi == current->backing_dev_info)
299 return 1;
300 return 0;
301}
302
303/*
304 * We detected a synchronous write error writing a page out. Probably
305 * -ENOSPC. We need to propagate that into the address_space for a subsequent
306 * fsync(), msync() or close().
307 *
308 * The tricky part is that after writepage we cannot touch the mapping: nothing
309 * prevents it from being freed up. But we have a ref on the page and once
310 * that page is locked, the mapping is pinned.
311 *
312 * We're allowed to run sleeping lock_page() here because we know the caller has
313 * __GFP_FS.
314 */
315static void handle_write_error(struct address_space *mapping,
316 struct page *page, int error)
317{
318 lock_page(page);
3e9f45bd
GC
319 if (page_mapping(page) == mapping)
320 mapping_set_error(mapping, error);
1da177e4
LT
321 unlock_page(page);
322}
323
c661b078
AW
324/* Request for sync pageout. */
325enum pageout_io {
326 PAGEOUT_IO_ASYNC,
327 PAGEOUT_IO_SYNC,
328};
329
04e62a29
CL
330/* possible outcome of pageout() */
331typedef enum {
332 /* failed to write page out, page is locked */
333 PAGE_KEEP,
334 /* move page to the active list, page is locked */
335 PAGE_ACTIVATE,
336 /* page has been sent to the disk successfully, page is unlocked */
337 PAGE_SUCCESS,
338 /* page is clean and locked */
339 PAGE_CLEAN,
340} pageout_t;
341
1da177e4 342/*
1742f19f
AM
343 * pageout is called by shrink_page_list() for each dirty page.
344 * Calls ->writepage().
1da177e4 345 */
c661b078
AW
346static pageout_t pageout(struct page *page, struct address_space *mapping,
347 enum pageout_io sync_writeback)
1da177e4
LT
348{
349 /*
350 * If the page is dirty, only perform writeback if that write
351 * will be non-blocking. To prevent this allocation from being
352 * stalled by pagecache activity. But note that there may be
353 * stalls if we need to run get_block(). We could test
354 * PagePrivate for that.
355 *
356 * If this process is currently in generic_file_write() against
357 * this page's queue, we can perform writeback even if that
358 * will block.
359 *
360 * If the page is swapcache, write it back even if that would
361 * block, for some throttling. This happens by accident, because
362 * swap_backing_dev_info is bust: it doesn't reflect the
363 * congestion state of the swapdevs. Easy to fix, if needed.
364 * See swapfile.c:page_queue_congested().
365 */
366 if (!is_page_cache_freeable(page))
367 return PAGE_KEEP;
368 if (!mapping) {
369 /*
370 * Some data journaling orphaned pages can have
371 * page->mapping == NULL while being dirty with clean buffers.
372 */
266cf658 373 if (page_has_private(page)) {
1da177e4
LT
374 if (try_to_free_buffers(page)) {
375 ClearPageDirty(page);
d40cee24 376 printk("%s: orphaned page\n", __func__);
1da177e4
LT
377 return PAGE_CLEAN;
378 }
379 }
380 return PAGE_KEEP;
381 }
382 if (mapping->a_ops->writepage == NULL)
383 return PAGE_ACTIVATE;
384 if (!may_write_to_queue(mapping->backing_dev_info))
385 return PAGE_KEEP;
386
387 if (clear_page_dirty_for_io(page)) {
388 int res;
389 struct writeback_control wbc = {
390 .sync_mode = WB_SYNC_NONE,
391 .nr_to_write = SWAP_CLUSTER_MAX,
111ebb6e
OH
392 .range_start = 0,
393 .range_end = LLONG_MAX,
1da177e4
LT
394 .nonblocking = 1,
395 .for_reclaim = 1,
396 };
397
398 SetPageReclaim(page);
399 res = mapping->a_ops->writepage(page, &wbc);
400 if (res < 0)
401 handle_write_error(mapping, page, res);
994fc28c 402 if (res == AOP_WRITEPAGE_ACTIVATE) {
1da177e4
LT
403 ClearPageReclaim(page);
404 return PAGE_ACTIVATE;
405 }
c661b078
AW
406
407 /*
408 * Wait on writeback if requested to. This happens when
409 * direct reclaiming a large contiguous area and the
410 * first attempt to free a range of pages fails.
411 */
412 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
413 wait_on_page_writeback(page);
414
1da177e4
LT
415 if (!PageWriteback(page)) {
416 /* synchronous write or broken a_ops? */
417 ClearPageReclaim(page);
418 }
e129b5c2 419 inc_zone_page_state(page, NR_VMSCAN_WRITE);
1da177e4
LT
420 return PAGE_SUCCESS;
421 }
422
423 return PAGE_CLEAN;
424}
425
a649fd92 426/*
e286781d
NP
427 * Same as remove_mapping, but if the page is removed from the mapping, it
428 * gets returned with a refcount of 0.
a649fd92 429 */
e286781d 430static int __remove_mapping(struct address_space *mapping, struct page *page)
49d2e9cc 431{
28e4d965
NP
432 BUG_ON(!PageLocked(page));
433 BUG_ON(mapping != page_mapping(page));
49d2e9cc 434
19fd6231 435 spin_lock_irq(&mapping->tree_lock);
49d2e9cc 436 /*
0fd0e6b0
NP
437 * The non racy check for a busy page.
438 *
439 * Must be careful with the order of the tests. When someone has
440 * a ref to the page, it may be possible that they dirty it then
441 * drop the reference. So if PageDirty is tested before page_count
442 * here, then the following race may occur:
443 *
444 * get_user_pages(&page);
445 * [user mapping goes away]
446 * write_to(page);
447 * !PageDirty(page) [good]
448 * SetPageDirty(page);
449 * put_page(page);
450 * !page_count(page) [good, discard it]
451 *
452 * [oops, our write_to data is lost]
453 *
454 * Reversing the order of the tests ensures such a situation cannot
455 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
456 * load is not satisfied before that of page->_count.
457 *
458 * Note that if SetPageDirty is always performed via set_page_dirty,
459 * and thus under tree_lock, then this ordering is not required.
49d2e9cc 460 */
e286781d 461 if (!page_freeze_refs(page, 2))
49d2e9cc 462 goto cannot_free;
e286781d
NP
463 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
464 if (unlikely(PageDirty(page))) {
465 page_unfreeze_refs(page, 2);
49d2e9cc 466 goto cannot_free;
e286781d 467 }
49d2e9cc
CL
468
469 if (PageSwapCache(page)) {
470 swp_entry_t swap = { .val = page_private(page) };
471 __delete_from_swap_cache(page);
19fd6231 472 spin_unlock_irq(&mapping->tree_lock);
cb4b86ba 473 swapcache_free(swap, page);
e286781d
NP
474 } else {
475 __remove_from_page_cache(page);
19fd6231 476 spin_unlock_irq(&mapping->tree_lock);
e767e056 477 mem_cgroup_uncharge_cache_page(page);
49d2e9cc
CL
478 }
479
49d2e9cc
CL
480 return 1;
481
482cannot_free:
19fd6231 483 spin_unlock_irq(&mapping->tree_lock);
49d2e9cc
CL
484 return 0;
485}
486
e286781d
NP
487/*
488 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
489 * someone else has a ref on the page, abort and return 0. If it was
490 * successfully detached, return 1. Assumes the caller has a single ref on
491 * this page.
492 */
493int remove_mapping(struct address_space *mapping, struct page *page)
494{
495 if (__remove_mapping(mapping, page)) {
496 /*
497 * Unfreezing the refcount with 1 rather than 2 effectively
498 * drops the pagecache ref for us without requiring another
499 * atomic operation.
500 */
501 page_unfreeze_refs(page, 1);
502 return 1;
503 }
504 return 0;
505}
506
894bc310
LS
507/**
508 * putback_lru_page - put previously isolated page onto appropriate LRU list
509 * @page: page to be put back to appropriate lru list
510 *
511 * Add previously isolated @page to appropriate LRU list.
512 * Page may still be unevictable for other reasons.
513 *
514 * lru_lock must not be held, interrupts must be enabled.
515 */
894bc310
LS
516void putback_lru_page(struct page *page)
517{
518 int lru;
519 int active = !!TestClearPageActive(page);
bbfd28ee 520 int was_unevictable = PageUnevictable(page);
894bc310
LS
521
522 VM_BUG_ON(PageLRU(page));
523
524redo:
525 ClearPageUnevictable(page);
526
527 if (page_evictable(page, NULL)) {
528 /*
529 * For evictable pages, we can use the cache.
530 * In event of a race, worst case is we end up with an
531 * unevictable page on [in]active list.
532 * We know how to handle that.
533 */
534 lru = active + page_is_file_cache(page);
535 lru_cache_add_lru(page, lru);
536 } else {
537 /*
538 * Put unevictable pages directly on zone's unevictable
539 * list.
540 */
541 lru = LRU_UNEVICTABLE;
542 add_page_to_unevictable_list(page);
543 }
894bc310
LS
544
545 /*
546 * page's status can change while we move it among lru. If an evictable
547 * page is on unevictable list, it never be freed. To avoid that,
548 * check after we added it to the list, again.
549 */
550 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
551 if (!isolate_lru_page(page)) {
552 put_page(page);
553 goto redo;
554 }
555 /* This means someone else dropped this page from LRU
556 * So, it will be freed or putback to LRU again. There is
557 * nothing to do here.
558 */
559 }
560
bbfd28ee
LS
561 if (was_unevictable && lru != LRU_UNEVICTABLE)
562 count_vm_event(UNEVICTABLE_PGRESCUED);
563 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
564 count_vm_event(UNEVICTABLE_PGCULLED);
565
894bc310
LS
566 put_page(page); /* drop ref from isolate */
567}
568
1da177e4 569/*
1742f19f 570 * shrink_page_list() returns the number of reclaimed pages
1da177e4 571 */
1742f19f 572static unsigned long shrink_page_list(struct list_head *page_list,
c661b078
AW
573 struct scan_control *sc,
574 enum pageout_io sync_writeback)
1da177e4
LT
575{
576 LIST_HEAD(ret_pages);
577 struct pagevec freed_pvec;
578 int pgactivate = 0;
05ff5137 579 unsigned long nr_reclaimed = 0;
6fe6b7e3 580 unsigned long vm_flags;
1da177e4
LT
581
582 cond_resched();
583
584 pagevec_init(&freed_pvec, 1);
585 while (!list_empty(page_list)) {
586 struct address_space *mapping;
587 struct page *page;
588 int may_enter_fs;
589 int referenced;
590
591 cond_resched();
592
593 page = lru_to_page(page_list);
594 list_del(&page->lru);
595
529ae9aa 596 if (!trylock_page(page))
1da177e4
LT
597 goto keep;
598
725d704e 599 VM_BUG_ON(PageActive(page));
1da177e4
LT
600
601 sc->nr_scanned++;
80e43426 602
b291f000
NP
603 if (unlikely(!page_evictable(page, NULL)))
604 goto cull_mlocked;
894bc310 605
a6dc60f8 606 if (!sc->may_unmap && page_mapped(page))
80e43426
CL
607 goto keep_locked;
608
1da177e4
LT
609 /* Double the slab pressure for mapped and swapcache pages */
610 if (page_mapped(page) || PageSwapCache(page))
611 sc->nr_scanned++;
612
c661b078
AW
613 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
614 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
615
616 if (PageWriteback(page)) {
617 /*
618 * Synchronous reclaim is performed in two passes,
619 * first an asynchronous pass over the list to
620 * start parallel writeback, and a second synchronous
621 * pass to wait for the IO to complete. Wait here
622 * for any page for which writeback has already
623 * started.
624 */
625 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
626 wait_on_page_writeback(page);
4dd4b920 627 else
c661b078
AW
628 goto keep_locked;
629 }
1da177e4 630
6fe6b7e3
WF
631 referenced = page_referenced(page, 1,
632 sc->mem_cgroup, &vm_flags);
03ef83af
MK
633 /*
634 * In active use or really unfreeable? Activate it.
635 * If page which have PG_mlocked lost isoltation race,
636 * try_to_unmap moves it to unevictable list
637 */
5ad333eb 638 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
03ef83af
MK
639 referenced && page_mapping_inuse(page)
640 && !(vm_flags & VM_LOCKED))
1da177e4
LT
641 goto activate_locked;
642
1da177e4
LT
643 /*
644 * Anonymous process memory has backing store?
645 * Try to allocate it some swap space here.
646 */
b291f000 647 if (PageAnon(page) && !PageSwapCache(page)) {
63eb6b93
HD
648 if (!(sc->gfp_mask & __GFP_IO))
649 goto keep_locked;
ac47b003 650 if (!add_to_swap(page))
1da177e4 651 goto activate_locked;
63eb6b93 652 may_enter_fs = 1;
b291f000 653 }
1da177e4
LT
654
655 mapping = page_mapping(page);
1da177e4
LT
656
657 /*
658 * The page is mapped into the page tables of one or more
659 * processes. Try to unmap it here.
660 */
661 if (page_mapped(page) && mapping) {
a48d07af 662 switch (try_to_unmap(page, 0)) {
1da177e4
LT
663 case SWAP_FAIL:
664 goto activate_locked;
665 case SWAP_AGAIN:
666 goto keep_locked;
b291f000
NP
667 case SWAP_MLOCK:
668 goto cull_mlocked;
1da177e4
LT
669 case SWAP_SUCCESS:
670 ; /* try to free the page below */
671 }
672 }
673
674 if (PageDirty(page)) {
5ad333eb 675 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
1da177e4 676 goto keep_locked;
4dd4b920 677 if (!may_enter_fs)
1da177e4 678 goto keep_locked;
52a8363e 679 if (!sc->may_writepage)
1da177e4
LT
680 goto keep_locked;
681
682 /* Page is dirty, try to write it out here */
c661b078 683 switch (pageout(page, mapping, sync_writeback)) {
1da177e4
LT
684 case PAGE_KEEP:
685 goto keep_locked;
686 case PAGE_ACTIVATE:
687 goto activate_locked;
688 case PAGE_SUCCESS:
4dd4b920 689 if (PageWriteback(page) || PageDirty(page))
1da177e4
LT
690 goto keep;
691 /*
692 * A synchronous write - probably a ramdisk. Go
693 * ahead and try to reclaim the page.
694 */
529ae9aa 695 if (!trylock_page(page))
1da177e4
LT
696 goto keep;
697 if (PageDirty(page) || PageWriteback(page))
698 goto keep_locked;
699 mapping = page_mapping(page);
700 case PAGE_CLEAN:
701 ; /* try to free the page below */
702 }
703 }
704
705 /*
706 * If the page has buffers, try to free the buffer mappings
707 * associated with this page. If we succeed we try to free
708 * the page as well.
709 *
710 * We do this even if the page is PageDirty().
711 * try_to_release_page() does not perform I/O, but it is
712 * possible for a page to have PageDirty set, but it is actually
713 * clean (all its buffers are clean). This happens if the
714 * buffers were written out directly, with submit_bh(). ext3
894bc310 715 * will do this, as well as the blockdev mapping.
1da177e4
LT
716 * try_to_release_page() will discover that cleanness and will
717 * drop the buffers and mark the page clean - it can be freed.
718 *
719 * Rarely, pages can have buffers and no ->mapping. These are
720 * the pages which were not successfully invalidated in
721 * truncate_complete_page(). We try to drop those buffers here
722 * and if that worked, and the page is no longer mapped into
723 * process address space (page_count == 1) it can be freed.
724 * Otherwise, leave the page on the LRU so it is swappable.
725 */
266cf658 726 if (page_has_private(page)) {
1da177e4
LT
727 if (!try_to_release_page(page, sc->gfp_mask))
728 goto activate_locked;
e286781d
NP
729 if (!mapping && page_count(page) == 1) {
730 unlock_page(page);
731 if (put_page_testzero(page))
732 goto free_it;
733 else {
734 /*
735 * rare race with speculative reference.
736 * the speculative reference will free
737 * this page shortly, so we may
738 * increment nr_reclaimed here (and
739 * leave it off the LRU).
740 */
741 nr_reclaimed++;
742 continue;
743 }
744 }
1da177e4
LT
745 }
746
e286781d 747 if (!mapping || !__remove_mapping(mapping, page))
49d2e9cc 748 goto keep_locked;
1da177e4 749
a978d6f5
NP
750 /*
751 * At this point, we have no other references and there is
752 * no way to pick any more up (removed from LRU, removed
753 * from pagecache). Can use non-atomic bitops now (and
754 * we obviously don't have to worry about waking up a process
755 * waiting on the page lock, because there are no references.
756 */
757 __clear_page_locked(page);
e286781d 758free_it:
05ff5137 759 nr_reclaimed++;
e286781d
NP
760 if (!pagevec_add(&freed_pvec, page)) {
761 __pagevec_free(&freed_pvec);
762 pagevec_reinit(&freed_pvec);
763 }
1da177e4
LT
764 continue;
765
b291f000 766cull_mlocked:
63d6c5ad
HD
767 if (PageSwapCache(page))
768 try_to_free_swap(page);
b291f000
NP
769 unlock_page(page);
770 putback_lru_page(page);
771 continue;
772
1da177e4 773activate_locked:
68a22394
RR
774 /* Not a candidate for swapping, so reclaim swap space. */
775 if (PageSwapCache(page) && vm_swap_full())
a2c43eed 776 try_to_free_swap(page);
894bc310 777 VM_BUG_ON(PageActive(page));
1da177e4
LT
778 SetPageActive(page);
779 pgactivate++;
780keep_locked:
781 unlock_page(page);
782keep:
783 list_add(&page->lru, &ret_pages);
b291f000 784 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
1da177e4
LT
785 }
786 list_splice(&ret_pages, page_list);
787 if (pagevec_count(&freed_pvec))
e286781d 788 __pagevec_free(&freed_pvec);
f8891e5e 789 count_vm_events(PGACTIVATE, pgactivate);
05ff5137 790 return nr_reclaimed;
1da177e4
LT
791}
792
5ad333eb
AW
793/* LRU Isolation modes. */
794#define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
795#define ISOLATE_ACTIVE 1 /* Isolate active pages. */
796#define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
797
798/*
799 * Attempt to remove the specified page from its LRU. Only take this page
800 * if it is of the appropriate PageActive status. Pages which are being
801 * freed elsewhere are also ignored.
802 *
803 * page: page to consider
804 * mode: one of the LRU isolation modes defined above
805 *
806 * returns 0 on success, -ve errno on failure.
807 */
4f98a2fe 808int __isolate_lru_page(struct page *page, int mode, int file)
5ad333eb
AW
809{
810 int ret = -EINVAL;
811
812 /* Only take pages on the LRU. */
813 if (!PageLRU(page))
814 return ret;
815
816 /*
817 * When checking the active state, we need to be sure we are
818 * dealing with comparible boolean values. Take the logical not
819 * of each.
820 */
821 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
822 return ret;
823
4f98a2fe
RR
824 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
825 return ret;
826
894bc310
LS
827 /*
828 * When this function is being called for lumpy reclaim, we
829 * initially look into all LRU pages, active, inactive and
830 * unevictable; only give shrink_page_list evictable pages.
831 */
832 if (PageUnevictable(page))
833 return ret;
834
5ad333eb 835 ret = -EBUSY;
08e552c6 836
5ad333eb
AW
837 if (likely(get_page_unless_zero(page))) {
838 /*
839 * Be careful not to clear PageLRU until after we're
840 * sure the page is not being freed elsewhere -- the
841 * page release code relies on it.
842 */
843 ClearPageLRU(page);
844 ret = 0;
845 }
846
847 return ret;
848}
849
1da177e4
LT
850/*
851 * zone->lru_lock is heavily contended. Some of the functions that
852 * shrink the lists perform better by taking out a batch of pages
853 * and working on them outside the LRU lock.
854 *
855 * For pagecache intensive workloads, this function is the hottest
856 * spot in the kernel (apart from copy_*_user functions).
857 *
858 * Appropriate locks must be held before calling this function.
859 *
860 * @nr_to_scan: The number of pages to look through on the list.
861 * @src: The LRU list to pull pages off.
862 * @dst: The temp list to put pages on to.
863 * @scanned: The number of pages that were scanned.
5ad333eb
AW
864 * @order: The caller's attempted allocation order
865 * @mode: One of the LRU isolation modes
4f98a2fe 866 * @file: True [1] if isolating file [!anon] pages
1da177e4
LT
867 *
868 * returns how many pages were moved onto *@dst.
869 */
69e05944
AM
870static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
871 struct list_head *src, struct list_head *dst,
4f98a2fe 872 unsigned long *scanned, int order, int mode, int file)
1da177e4 873{
69e05944 874 unsigned long nr_taken = 0;
c9b02d97 875 unsigned long scan;
1da177e4 876
c9b02d97 877 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
5ad333eb
AW
878 struct page *page;
879 unsigned long pfn;
880 unsigned long end_pfn;
881 unsigned long page_pfn;
882 int zone_id;
883
1da177e4
LT
884 page = lru_to_page(src);
885 prefetchw_prev_lru_page(page, src, flags);
886
725d704e 887 VM_BUG_ON(!PageLRU(page));
8d438f96 888
4f98a2fe 889 switch (__isolate_lru_page(page, mode, file)) {
5ad333eb
AW
890 case 0:
891 list_move(&page->lru, dst);
2ffebca6 892 mem_cgroup_del_lru(page);
7c8ee9a8 893 nr_taken++;
5ad333eb
AW
894 break;
895
896 case -EBUSY:
897 /* else it is being freed elsewhere */
898 list_move(&page->lru, src);
2ffebca6 899 mem_cgroup_rotate_lru_list(page, page_lru(page));
5ad333eb 900 continue;
46453a6e 901
5ad333eb
AW
902 default:
903 BUG();
904 }
905
906 if (!order)
907 continue;
908
909 /*
910 * Attempt to take all pages in the order aligned region
911 * surrounding the tag page. Only take those pages of
912 * the same active state as that tag page. We may safely
913 * round the target page pfn down to the requested order
914 * as the mem_map is guarenteed valid out to MAX_ORDER,
915 * where that page is in a different zone we will detect
916 * it from its zone id and abort this block scan.
917 */
918 zone_id = page_zone_id(page);
919 page_pfn = page_to_pfn(page);
920 pfn = page_pfn & ~((1 << order) - 1);
921 end_pfn = pfn + (1 << order);
922 for (; pfn < end_pfn; pfn++) {
923 struct page *cursor_page;
924
925 /* The target page is in the block, ignore it. */
926 if (unlikely(pfn == page_pfn))
927 continue;
928
929 /* Avoid holes within the zone. */
930 if (unlikely(!pfn_valid_within(pfn)))
931 break;
932
933 cursor_page = pfn_to_page(pfn);
4f98a2fe 934
5ad333eb
AW
935 /* Check that we have not crossed a zone boundary. */
936 if (unlikely(page_zone_id(cursor_page) != zone_id))
937 continue;
ee993b13 938 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
5ad333eb 939 list_move(&cursor_page->lru, dst);
cb4cbcf6 940 mem_cgroup_del_lru(cursor_page);
5ad333eb
AW
941 nr_taken++;
942 scan++;
5ad333eb
AW
943 }
944 }
1da177e4
LT
945 }
946
947 *scanned = scan;
948 return nr_taken;
949}
950
66e1707b
BS
951static unsigned long isolate_pages_global(unsigned long nr,
952 struct list_head *dst,
953 unsigned long *scanned, int order,
954 int mode, struct zone *z,
955 struct mem_cgroup *mem_cont,
4f98a2fe 956 int active, int file)
66e1707b 957{
4f98a2fe 958 int lru = LRU_BASE;
66e1707b 959 if (active)
4f98a2fe
RR
960 lru += LRU_ACTIVE;
961 if (file)
962 lru += LRU_FILE;
963 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
964 mode, !!file);
66e1707b
BS
965}
966
5ad333eb
AW
967/*
968 * clear_active_flags() is a helper for shrink_active_list(), clearing
969 * any active bits from the pages in the list.
970 */
4f98a2fe
RR
971static unsigned long clear_active_flags(struct list_head *page_list,
972 unsigned int *count)
5ad333eb
AW
973{
974 int nr_active = 0;
4f98a2fe 975 int lru;
5ad333eb
AW
976 struct page *page;
977
4f98a2fe
RR
978 list_for_each_entry(page, page_list, lru) {
979 lru = page_is_file_cache(page);
5ad333eb 980 if (PageActive(page)) {
4f98a2fe 981 lru += LRU_ACTIVE;
5ad333eb
AW
982 ClearPageActive(page);
983 nr_active++;
984 }
4f98a2fe
RR
985 count[lru]++;
986 }
5ad333eb
AW
987
988 return nr_active;
989}
990
62695a84
NP
991/**
992 * isolate_lru_page - tries to isolate a page from its LRU list
993 * @page: page to isolate from its LRU list
994 *
995 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
996 * vmstat statistic corresponding to whatever LRU list the page was on.
997 *
998 * Returns 0 if the page was removed from an LRU list.
999 * Returns -EBUSY if the page was not on an LRU list.
1000 *
1001 * The returned page will have PageLRU() cleared. If it was found on
894bc310
LS
1002 * the active list, it will have PageActive set. If it was found on
1003 * the unevictable list, it will have the PageUnevictable bit set. That flag
1004 * may need to be cleared by the caller before letting the page go.
62695a84
NP
1005 *
1006 * The vmstat statistic corresponding to the list on which the page was
1007 * found will be decremented.
1008 *
1009 * Restrictions:
1010 * (1) Must be called with an elevated refcount on the page. This is a
1011 * fundamentnal difference from isolate_lru_pages (which is called
1012 * without a stable reference).
1013 * (2) the lru_lock must not be held.
1014 * (3) interrupts must be enabled.
1015 */
1016int isolate_lru_page(struct page *page)
1017{
1018 int ret = -EBUSY;
1019
1020 if (PageLRU(page)) {
1021 struct zone *zone = page_zone(page);
1022
1023 spin_lock_irq(&zone->lru_lock);
1024 if (PageLRU(page) && get_page_unless_zero(page)) {
894bc310 1025 int lru = page_lru(page);
62695a84
NP
1026 ret = 0;
1027 ClearPageLRU(page);
4f98a2fe 1028
4f98a2fe 1029 del_page_from_lru_list(zone, page, lru);
62695a84
NP
1030 }
1031 spin_unlock_irq(&zone->lru_lock);
1032 }
1033 return ret;
1034}
1035
1da177e4 1036/*
1742f19f
AM
1037 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1038 * of reclaimed pages
1da177e4 1039 */
1742f19f 1040static unsigned long shrink_inactive_list(unsigned long max_scan,
33c120ed
RR
1041 struct zone *zone, struct scan_control *sc,
1042 int priority, int file)
1da177e4
LT
1043{
1044 LIST_HEAD(page_list);
1045 struct pagevec pvec;
69e05944 1046 unsigned long nr_scanned = 0;
05ff5137 1047 unsigned long nr_reclaimed = 0;
6e901571 1048 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
78dc583d
KM
1049 int lumpy_reclaim = 0;
1050
1051 /*
1052 * If we need a large contiguous chunk of memory, or have
1053 * trouble getting a small set of contiguous pages, we
1054 * will reclaim both active and inactive pages.
1055 *
1056 * We use the same threshold as pageout congestion_wait below.
1057 */
1058 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1059 lumpy_reclaim = 1;
1060 else if (sc->order && priority < DEF_PRIORITY - 2)
1061 lumpy_reclaim = 1;
1da177e4
LT
1062
1063 pagevec_init(&pvec, 1);
1064
1065 lru_add_drain();
1066 spin_lock_irq(&zone->lru_lock);
69e05944 1067 do {
1da177e4 1068 struct page *page;
69e05944
AM
1069 unsigned long nr_taken;
1070 unsigned long nr_scan;
1071 unsigned long nr_freed;
5ad333eb 1072 unsigned long nr_active;
4f98a2fe 1073 unsigned int count[NR_LRU_LISTS] = { 0, };
78dc583d 1074 int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
1da177e4 1075
66e1707b 1076 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
4f98a2fe
RR
1077 &page_list, &nr_scan, sc->order, mode,
1078 zone, sc->mem_cgroup, 0, file);
1079 nr_active = clear_active_flags(&page_list, count);
e9187bdc 1080 __count_vm_events(PGDEACTIVATE, nr_active);
5ad333eb 1081
4f98a2fe
RR
1082 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1083 -count[LRU_ACTIVE_FILE]);
1084 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1085 -count[LRU_INACTIVE_FILE]);
1086 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1087 -count[LRU_ACTIVE_ANON]);
1088 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1089 -count[LRU_INACTIVE_ANON]);
1090
e72e2bd6 1091 if (scanning_global_lru(sc))
1cfb419b 1092 zone->pages_scanned += nr_scan;
3e2f41f1
KM
1093
1094 reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1095 reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1096 reclaim_stat->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1097 reclaim_stat->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1098
1da177e4
LT
1099 spin_unlock_irq(&zone->lru_lock);
1100
69e05944 1101 nr_scanned += nr_scan;
c661b078
AW
1102 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1103
1104 /*
1105 * If we are direct reclaiming for contiguous pages and we do
1106 * not reclaim everything in the list, try again and wait
1107 * for IO to complete. This will stall high-order allocations
1108 * but that should be acceptable to the caller
1109 */
1110 if (nr_freed < nr_taken && !current_is_kswapd() &&
78dc583d 1111 lumpy_reclaim) {
8aa7e847 1112 congestion_wait(BLK_RW_ASYNC, HZ/10);
c661b078
AW
1113
1114 /*
1115 * The attempt at page out may have made some
1116 * of the pages active, mark them inactive again.
1117 */
4f98a2fe 1118 nr_active = clear_active_flags(&page_list, count);
c661b078
AW
1119 count_vm_events(PGDEACTIVATE, nr_active);
1120
1121 nr_freed += shrink_page_list(&page_list, sc,
1122 PAGEOUT_IO_SYNC);
1123 }
1124
05ff5137 1125 nr_reclaimed += nr_freed;
a74609fa
NP
1126 local_irq_disable();
1127 if (current_is_kswapd()) {
f8891e5e
CL
1128 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
1129 __count_vm_events(KSWAPD_STEAL, nr_freed);
e72e2bd6 1130 } else if (scanning_global_lru(sc))
f8891e5e 1131 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1cfb419b 1132
918d3f90 1133 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
a74609fa 1134
fb8d14e1
WF
1135 if (nr_taken == 0)
1136 goto done;
1137
a74609fa 1138 spin_lock(&zone->lru_lock);
1da177e4
LT
1139 /*
1140 * Put back any unfreeable pages.
1141 */
1142 while (!list_empty(&page_list)) {
894bc310 1143 int lru;
1da177e4 1144 page = lru_to_page(&page_list);
725d704e 1145 VM_BUG_ON(PageLRU(page));
1da177e4 1146 list_del(&page->lru);
894bc310
LS
1147 if (unlikely(!page_evictable(page, NULL))) {
1148 spin_unlock_irq(&zone->lru_lock);
1149 putback_lru_page(page);
1150 spin_lock_irq(&zone->lru_lock);
1151 continue;
1152 }
1153 SetPageLRU(page);
1154 lru = page_lru(page);
1155 add_page_to_lru_list(zone, page, lru);
3e2f41f1 1156 if (PageActive(page)) {
4f98a2fe 1157 int file = !!page_is_file_cache(page);
6e901571 1158 reclaim_stat->recent_rotated[file]++;
4f98a2fe 1159 }
1da177e4
LT
1160 if (!pagevec_add(&pvec, page)) {
1161 spin_unlock_irq(&zone->lru_lock);
1162 __pagevec_release(&pvec);
1163 spin_lock_irq(&zone->lru_lock);
1164 }
1165 }
69e05944 1166 } while (nr_scanned < max_scan);
fb8d14e1 1167 spin_unlock(&zone->lru_lock);
1da177e4 1168done:
fb8d14e1 1169 local_irq_enable();
1da177e4 1170 pagevec_release(&pvec);
05ff5137 1171 return nr_reclaimed;
1da177e4
LT
1172}
1173
3bb1a852
MB
1174/*
1175 * We are about to scan this zone at a certain priority level. If that priority
1176 * level is smaller (ie: more urgent) than the previous priority, then note
1177 * that priority level within the zone. This is done so that when the next
1178 * process comes in to scan this zone, it will immediately start out at this
1179 * priority level rather than having to build up its own scanning priority.
1180 * Here, this priority affects only the reclaim-mapped threshold.
1181 */
1182static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1183{
1184 if (priority < zone->prev_priority)
1185 zone->prev_priority = priority;
1186}
1187
1da177e4
LT
1188/*
1189 * This moves pages from the active list to the inactive list.
1190 *
1191 * We move them the other way if the page is referenced by one or more
1192 * processes, from rmap.
1193 *
1194 * If the pages are mostly unmapped, the processing is fast and it is
1195 * appropriate to hold zone->lru_lock across the whole operation. But if
1196 * the pages are mapped, the processing is slow (page_referenced()) so we
1197 * should drop zone->lru_lock around each page. It's impossible to balance
1198 * this, so instead we remove the pages from the LRU while processing them.
1199 * It is safe to rely on PG_active against the non-LRU pages in here because
1200 * nobody will play with that bit on a non-LRU page.
1201 *
1202 * The downside is that we have to touch page->_count against each page.
1203 * But we had to alter page->flags anyway.
1204 */
1cfb419b 1205
3eb4140f
WF
1206static void move_active_pages_to_lru(struct zone *zone,
1207 struct list_head *list,
1208 enum lru_list lru)
1209{
1210 unsigned long pgmoved = 0;
1211 struct pagevec pvec;
1212 struct page *page;
1213
1214 pagevec_init(&pvec, 1);
1215
1216 while (!list_empty(list)) {
1217 page = lru_to_page(list);
1218 prefetchw_prev_lru_page(page, list, flags);
1219
1220 VM_BUG_ON(PageLRU(page));
1221 SetPageLRU(page);
1222
1223 VM_BUG_ON(!PageActive(page));
1224 if (!is_active_lru(lru))
1225 ClearPageActive(page); /* we are de-activating */
1226
1227 list_move(&page->lru, &zone->lru[lru].list);
1228 mem_cgroup_add_lru_list(page, lru);
1229 pgmoved++;
1230
1231 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1232 spin_unlock_irq(&zone->lru_lock);
1233 if (buffer_heads_over_limit)
1234 pagevec_strip(&pvec);
1235 __pagevec_release(&pvec);
1236 spin_lock_irq(&zone->lru_lock);
1237 }
1238 }
1239 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1240 if (!is_active_lru(lru))
1241 __count_vm_events(PGDEACTIVATE, pgmoved);
1242}
1cfb419b 1243
1742f19f 1244static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
4f98a2fe 1245 struct scan_control *sc, int priority, int file)
1da177e4 1246{
69e05944 1247 unsigned long pgmoved;
69e05944 1248 unsigned long pgscanned;
6fe6b7e3 1249 unsigned long vm_flags;
1da177e4 1250 LIST_HEAD(l_hold); /* The pages which were snipped off */
8cab4754 1251 LIST_HEAD(l_active);
b69408e8 1252 LIST_HEAD(l_inactive);
1da177e4 1253 struct page *page;
6e901571 1254 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1da177e4
LT
1255
1256 lru_add_drain();
1257 spin_lock_irq(&zone->lru_lock);
66e1707b
BS
1258 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1259 ISOLATE_ACTIVE, zone,
4f98a2fe 1260 sc->mem_cgroup, 1, file);
1cfb419b
KH
1261 /*
1262 * zone->pages_scanned is used for detect zone's oom
1263 * mem_cgroup remembers nr_scan by itself.
1264 */
e72e2bd6 1265 if (scanning_global_lru(sc)) {
1cfb419b 1266 zone->pages_scanned += pgscanned;
4f98a2fe 1267 }
3e2f41f1 1268 reclaim_stat->recent_scanned[!!file] += pgmoved;
1cfb419b 1269
3eb4140f 1270 __count_zone_vm_events(PGREFILL, zone, pgscanned);
4f98a2fe
RR
1271 if (file)
1272 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1273 else
1274 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
1da177e4
LT
1275 spin_unlock_irq(&zone->lru_lock);
1276
af166777 1277 pgmoved = 0; /* count referenced (mapping) mapped pages */
1da177e4
LT
1278 while (!list_empty(&l_hold)) {
1279 cond_resched();
1280 page = lru_to_page(&l_hold);
1281 list_del(&page->lru);
7e9cd484 1282
894bc310
LS
1283 if (unlikely(!page_evictable(page, NULL))) {
1284 putback_lru_page(page);
1285 continue;
1286 }
1287
7e9cd484
RR
1288 /* page_referenced clears PageReferenced */
1289 if (page_mapping_inuse(page) &&
8cab4754 1290 page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
7e9cd484 1291 pgmoved++;
8cab4754
WF
1292 /*
1293 * Identify referenced, file-backed active pages and
1294 * give them one more trip around the active list. So
1295 * that executable code get better chances to stay in
1296 * memory under moderate memory pressure. Anon pages
1297 * are not likely to be evicted by use-once streaming
1298 * IO, plus JVM can create lots of anon VM_EXEC pages,
1299 * so we ignore them here.
1300 */
1301 if ((vm_flags & VM_EXEC) && !PageAnon(page)) {
1302 list_add(&page->lru, &l_active);
1303 continue;
1304 }
1305 }
7e9cd484 1306
1da177e4
LT
1307 list_add(&page->lru, &l_inactive);
1308 }
1309
b555749a 1310 /*
8cab4754 1311 * Move pages back to the lru list.
b555749a 1312 */
2a1dc509 1313 spin_lock_irq(&zone->lru_lock);
556adecb 1314 /*
8cab4754
WF
1315 * Count referenced pages from currently used mappings as rotated,
1316 * even though only some of them are actually re-activated. This
1317 * helps balance scan pressure between file and anonymous pages in
1318 * get_scan_ratio.
7e9cd484 1319 */
3e2f41f1 1320 reclaim_stat->recent_rotated[!!file] += pgmoved;
556adecb 1321
3eb4140f
WF
1322 move_active_pages_to_lru(zone, &l_active,
1323 LRU_ACTIVE + file * LRU_FILE);
1324 move_active_pages_to_lru(zone, &l_inactive,
1325 LRU_BASE + file * LRU_FILE);
8cab4754 1326
f8891e5e 1327 spin_unlock_irq(&zone->lru_lock);
1da177e4
LT
1328}
1329
14797e23 1330static int inactive_anon_is_low_global(struct zone *zone)
f89eb90e
KM
1331{
1332 unsigned long active, inactive;
1333
1334 active = zone_page_state(zone, NR_ACTIVE_ANON);
1335 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1336
1337 if (inactive * zone->inactive_ratio < active)
1338 return 1;
1339
1340 return 0;
1341}
1342
14797e23
KM
1343/**
1344 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1345 * @zone: zone to check
1346 * @sc: scan control of this context
1347 *
1348 * Returns true if the zone does not have enough inactive anon pages,
1349 * meaning some active anon pages need to be deactivated.
1350 */
1351static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1352{
1353 int low;
1354
e72e2bd6 1355 if (scanning_global_lru(sc))
14797e23
KM
1356 low = inactive_anon_is_low_global(zone);
1357 else
c772be93 1358 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
14797e23
KM
1359 return low;
1360}
1361
56e49d21
RR
1362static int inactive_file_is_low_global(struct zone *zone)
1363{
1364 unsigned long active, inactive;
1365
1366 active = zone_page_state(zone, NR_ACTIVE_FILE);
1367 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1368
1369 return (active > inactive);
1370}
1371
1372/**
1373 * inactive_file_is_low - check if file pages need to be deactivated
1374 * @zone: zone to check
1375 * @sc: scan control of this context
1376 *
1377 * When the system is doing streaming IO, memory pressure here
1378 * ensures that active file pages get deactivated, until more
1379 * than half of the file pages are on the inactive list.
1380 *
1381 * Once we get to that situation, protect the system's working
1382 * set from being evicted by disabling active file page aging.
1383 *
1384 * This uses a different ratio than the anonymous pages, because
1385 * the page cache uses a use-once replacement algorithm.
1386 */
1387static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1388{
1389 int low;
1390
1391 if (scanning_global_lru(sc))
1392 low = inactive_file_is_low_global(zone);
1393 else
1394 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1395 return low;
1396}
1397
4f98a2fe 1398static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
b69408e8
CL
1399 struct zone *zone, struct scan_control *sc, int priority)
1400{
4f98a2fe
RR
1401 int file = is_file_lru(lru);
1402
56e49d21 1403 if (lru == LRU_ACTIVE_FILE && inactive_file_is_low(zone, sc)) {
556adecb
RR
1404 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1405 return 0;
1406 }
1407
14797e23 1408 if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
4f98a2fe 1409 shrink_active_list(nr_to_scan, zone, sc, priority, file);
b69408e8
CL
1410 return 0;
1411 }
33c120ed 1412 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
4f98a2fe
RR
1413}
1414
1415/*
1416 * Determine how aggressively the anon and file LRU lists should be
1417 * scanned. The relative value of each set of LRU lists is determined
1418 * by looking at the fraction of the pages scanned we did rotate back
1419 * onto the active list instead of evict.
1420 *
1421 * percent[0] specifies how much pressure to put on ram/swap backed
1422 * memory, while percent[1] determines pressure on the file LRUs.
1423 */
1424static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1425 unsigned long *percent)
1426{
1427 unsigned long anon, file, free;
1428 unsigned long anon_prio, file_prio;
1429 unsigned long ap, fp;
6e901571 1430 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
4f98a2fe 1431
c9f299d9
KM
1432 anon = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) +
1433 zone_nr_pages(zone, sc, LRU_INACTIVE_ANON);
1434 file = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) +
1435 zone_nr_pages(zone, sc, LRU_INACTIVE_FILE);
b962716b 1436
e72e2bd6 1437 if (scanning_global_lru(sc)) {
eeee9a8c
KM
1438 free = zone_page_state(zone, NR_FREE_PAGES);
1439 /* If we have very few page cache pages,
1440 force-scan anon pages. */
41858966 1441 if (unlikely(file + free <= high_wmark_pages(zone))) {
eeee9a8c
KM
1442 percent[0] = 100;
1443 percent[1] = 0;
1444 return;
1445 }
4f98a2fe
RR
1446 }
1447
1448 /*
1449 * OK, so we have swap space and a fair amount of page cache
1450 * pages. We use the recently rotated / recently scanned
1451 * ratios to determine how valuable each cache is.
1452 *
1453 * Because workloads change over time (and to avoid overflow)
1454 * we keep these statistics as a floating average, which ends
1455 * up weighing recent references more than old ones.
1456 *
1457 * anon in [0], file in [1]
1458 */
6e901571 1459 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
4f98a2fe 1460 spin_lock_irq(&zone->lru_lock);
6e901571
KM
1461 reclaim_stat->recent_scanned[0] /= 2;
1462 reclaim_stat->recent_rotated[0] /= 2;
4f98a2fe
RR
1463 spin_unlock_irq(&zone->lru_lock);
1464 }
1465
6e901571 1466 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
4f98a2fe 1467 spin_lock_irq(&zone->lru_lock);
6e901571
KM
1468 reclaim_stat->recent_scanned[1] /= 2;
1469 reclaim_stat->recent_rotated[1] /= 2;
4f98a2fe
RR
1470 spin_unlock_irq(&zone->lru_lock);
1471 }
1472
1473 /*
1474 * With swappiness at 100, anonymous and file have the same priority.
1475 * This scanning priority is essentially the inverse of IO cost.
1476 */
1477 anon_prio = sc->swappiness;
1478 file_prio = 200 - sc->swappiness;
1479
1480 /*
00d8089c
RR
1481 * The amount of pressure on anon vs file pages is inversely
1482 * proportional to the fraction of recently scanned pages on
1483 * each list that were recently referenced and in active use.
4f98a2fe 1484 */
6e901571
KM
1485 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1486 ap /= reclaim_stat->recent_rotated[0] + 1;
4f98a2fe 1487
6e901571
KM
1488 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1489 fp /= reclaim_stat->recent_rotated[1] + 1;
4f98a2fe
RR
1490
1491 /* Normalize to percentages */
1492 percent[0] = 100 * ap / (ap + fp + 1);
1493 percent[1] = 100 - percent[0];
b69408e8
CL
1494}
1495
6e08a369
WF
1496/*
1497 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1498 * until we collected @swap_cluster_max pages to scan.
1499 */
1500static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
1501 unsigned long *nr_saved_scan,
1502 unsigned long swap_cluster_max)
1503{
1504 unsigned long nr;
1505
1506 *nr_saved_scan += nr_to_scan;
1507 nr = *nr_saved_scan;
1508
1509 if (nr >= swap_cluster_max)
1510 *nr_saved_scan = 0;
1511 else
1512 nr = 0;
1513
1514 return nr;
1515}
4f98a2fe 1516
1da177e4
LT
1517/*
1518 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1519 */
a79311c1 1520static void shrink_zone(int priority, struct zone *zone,
05ff5137 1521 struct scan_control *sc)
1da177e4 1522{
b69408e8 1523 unsigned long nr[NR_LRU_LISTS];
8695949a 1524 unsigned long nr_to_scan;
4f98a2fe 1525 unsigned long percent[2]; /* anon @ 0; file @ 1 */
b69408e8 1526 enum lru_list l;
01dbe5c9
KM
1527 unsigned long nr_reclaimed = sc->nr_reclaimed;
1528 unsigned long swap_cluster_max = sc->swap_cluster_max;
9198e96c 1529 int noswap = 0;
1da177e4 1530
9198e96c
DN
1531 /* If we have no swap space, do not bother scanning anon pages. */
1532 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1533 noswap = 1;
1534 percent[0] = 0;
1535 percent[1] = 100;
1536 } else
1537 get_scan_ratio(zone, sc, percent);
4f98a2fe 1538
894bc310 1539 for_each_evictable_lru(l) {
9439c1c9 1540 int file = is_file_lru(l);
8713e012 1541 unsigned long scan;
e0f79b8f 1542
f272b7bc 1543 scan = zone_nr_pages(zone, sc, l);
9198e96c 1544 if (priority || noswap) {
9439c1c9
KM
1545 scan >>= priority;
1546 scan = (scan * percent[file]) / 100;
1547 }
6e08a369
WF
1548 if (scanning_global_lru(sc))
1549 nr[l] = nr_scan_try_batch(scan,
1550 &zone->lru[l].nr_saved_scan,
1551 swap_cluster_max);
1552 else
9439c1c9 1553 nr[l] = scan;
1cfb419b 1554 }
1da177e4 1555
556adecb
RR
1556 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1557 nr[LRU_INACTIVE_FILE]) {
894bc310 1558 for_each_evictable_lru(l) {
b69408e8 1559 if (nr[l]) {
01dbe5c9 1560 nr_to_scan = min(nr[l], swap_cluster_max);
b69408e8 1561 nr[l] -= nr_to_scan;
1da177e4 1562
01dbe5c9
KM
1563 nr_reclaimed += shrink_list(l, nr_to_scan,
1564 zone, sc, priority);
b69408e8 1565 }
1da177e4 1566 }
a79311c1
RR
1567 /*
1568 * On large memory systems, scan >> priority can become
1569 * really large. This is fine for the starting priority;
1570 * we want to put equal scanning pressure on each zone.
1571 * However, if the VM has a harder time of freeing pages,
1572 * with multiple processes reclaiming pages, the total
1573 * freeing target can get unreasonably large.
1574 */
01dbe5c9 1575 if (nr_reclaimed > swap_cluster_max &&
a79311c1
RR
1576 priority < DEF_PRIORITY && !current_is_kswapd())
1577 break;
1da177e4
LT
1578 }
1579
01dbe5c9
KM
1580 sc->nr_reclaimed = nr_reclaimed;
1581
556adecb
RR
1582 /*
1583 * Even if we did not try to evict anon pages at all, we want to
1584 * rebalance the anon lru active/inactive ratio.
1585 */
69c85481 1586 if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
556adecb
RR
1587 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1588
232ea4d6 1589 throttle_vm_writeout(sc->gfp_mask);
1da177e4
LT
1590}
1591
1592/*
1593 * This is the direct reclaim path, for page-allocating processes. We only
1594 * try to reclaim pages from zones which will satisfy the caller's allocation
1595 * request.
1596 *
41858966
MG
1597 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1598 * Because:
1da177e4
LT
1599 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1600 * allocation or
41858966
MG
1601 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1602 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1603 * zone defense algorithm.
1da177e4 1604 *
1da177e4
LT
1605 * If a zone is deemed to be full of pinned pages then just give it a light
1606 * scan then give up on it.
1607 */
a79311c1 1608static void shrink_zones(int priority, struct zonelist *zonelist,
05ff5137 1609 struct scan_control *sc)
1da177e4 1610{
54a6eb5c 1611 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
dd1a239f 1612 struct zoneref *z;
54a6eb5c 1613 struct zone *zone;
1cfb419b 1614
408d8544 1615 sc->all_unreclaimable = 1;
327c0e96
KH
1616 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1617 sc->nodemask) {
f3fe6512 1618 if (!populated_zone(zone))
1da177e4 1619 continue;
1cfb419b
KH
1620 /*
1621 * Take care memory controller reclaiming has small influence
1622 * to global LRU.
1623 */
e72e2bd6 1624 if (scanning_global_lru(sc)) {
1cfb419b
KH
1625 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1626 continue;
1627 note_zone_scanning_priority(zone, priority);
1da177e4 1628
1cfb419b
KH
1629 if (zone_is_all_unreclaimable(zone) &&
1630 priority != DEF_PRIORITY)
1631 continue; /* Let kswapd poll it */
1632 sc->all_unreclaimable = 0;
1633 } else {
1634 /*
1635 * Ignore cpuset limitation here. We just want to reduce
1636 * # of used pages by us regardless of memory shortage.
1637 */
1638 sc->all_unreclaimable = 0;
1639 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1640 priority);
1641 }
408d8544 1642
a79311c1 1643 shrink_zone(priority, zone, sc);
1da177e4
LT
1644 }
1645}
4f98a2fe 1646
1da177e4
LT
1647/*
1648 * This is the main entry point to direct page reclaim.
1649 *
1650 * If a full scan of the inactive list fails to free enough memory then we
1651 * are "out of memory" and something needs to be killed.
1652 *
1653 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1654 * high - the zone may be full of dirty or under-writeback pages, which this
1655 * caller can't do much about. We kick pdflush and take explicit naps in the
1656 * hope that some of these pages can be written. But if the allocating task
1657 * holds filesystem locks which prevent writeout this might not work, and the
1658 * allocation attempt will fail.
a41f24ea
NA
1659 *
1660 * returns: 0, if no pages reclaimed
1661 * else, the number of pages reclaimed
1da177e4 1662 */
dac1d27b 1663static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
dd1a239f 1664 struct scan_control *sc)
1da177e4
LT
1665{
1666 int priority;
c700be3d 1667 unsigned long ret = 0;
69e05944 1668 unsigned long total_scanned = 0;
1da177e4 1669 struct reclaim_state *reclaim_state = current->reclaim_state;
1da177e4 1670 unsigned long lru_pages = 0;
dd1a239f 1671 struct zoneref *z;
54a6eb5c 1672 struct zone *zone;
dd1a239f 1673 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1da177e4 1674
873b4771
KK
1675 delayacct_freepages_start();
1676
e72e2bd6 1677 if (scanning_global_lru(sc))
1cfb419b
KH
1678 count_vm_event(ALLOCSTALL);
1679 /*
1680 * mem_cgroup will not do shrink_slab.
1681 */
e72e2bd6 1682 if (scanning_global_lru(sc)) {
54a6eb5c 1683 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1da177e4 1684
1cfb419b
KH
1685 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1686 continue;
1da177e4 1687
4f98a2fe 1688 lru_pages += zone_lru_pages(zone);
1cfb419b 1689 }
1da177e4
LT
1690 }
1691
1692 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
66e1707b 1693 sc->nr_scanned = 0;
f7b7fd8f
RR
1694 if (!priority)
1695 disable_swap_token();
a79311c1 1696 shrink_zones(priority, zonelist, sc);
66e1707b
BS
1697 /*
1698 * Don't shrink slabs when reclaiming memory from
1699 * over limit cgroups
1700 */
e72e2bd6 1701 if (scanning_global_lru(sc)) {
dd1a239f 1702 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
91a45470 1703 if (reclaim_state) {
a79311c1 1704 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
91a45470
KH
1705 reclaim_state->reclaimed_slab = 0;
1706 }
1da177e4 1707 }
66e1707b 1708 total_scanned += sc->nr_scanned;
a79311c1
RR
1709 if (sc->nr_reclaimed >= sc->swap_cluster_max) {
1710 ret = sc->nr_reclaimed;
1da177e4
LT
1711 goto out;
1712 }
1713
1714 /*
1715 * Try to write back as many pages as we just scanned. This
1716 * tends to cause slow streaming writers to write data to the
1717 * disk smoothly, at the dirtying rate, which is nice. But
1718 * that's undesirable in laptop mode, where we *want* lumpy
1719 * writeout. So in laptop mode, write out the whole world.
1720 */
66e1707b
BS
1721 if (total_scanned > sc->swap_cluster_max +
1722 sc->swap_cluster_max / 2) {
03ba3782 1723 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
66e1707b 1724 sc->may_writepage = 1;
1da177e4
LT
1725 }
1726
1727 /* Take a nap, wait for some writeback to complete */
4dd4b920 1728 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
8aa7e847 1729 congestion_wait(BLK_RW_ASYNC, HZ/10);
1da177e4 1730 }
87547ee9 1731 /* top priority shrink_zones still had more to do? don't OOM, then */
e72e2bd6 1732 if (!sc->all_unreclaimable && scanning_global_lru(sc))
a79311c1 1733 ret = sc->nr_reclaimed;
1da177e4 1734out:
3bb1a852
MB
1735 /*
1736 * Now that we've scanned all the zones at this priority level, note
1737 * that level within the zone so that the next thread which performs
1738 * scanning of this zone will immediately start out at this priority
1739 * level. This affects only the decision whether or not to bring
1740 * mapped pages onto the inactive list.
1741 */
1742 if (priority < 0)
1743 priority = 0;
1da177e4 1744
e72e2bd6 1745 if (scanning_global_lru(sc)) {
54a6eb5c 1746 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1cfb419b
KH
1747
1748 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1749 continue;
1750
1751 zone->prev_priority = priority;
1752 }
1753 } else
1754 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1da177e4 1755
873b4771
KK
1756 delayacct_freepages_end();
1757
1da177e4
LT
1758 return ret;
1759}
1760
dac1d27b 1761unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
327c0e96 1762 gfp_t gfp_mask, nodemask_t *nodemask)
66e1707b
BS
1763{
1764 struct scan_control sc = {
1765 .gfp_mask = gfp_mask,
1766 .may_writepage = !laptop_mode,
1767 .swap_cluster_max = SWAP_CLUSTER_MAX,
a6dc60f8 1768 .may_unmap = 1,
2e2e4259 1769 .may_swap = 1,
66e1707b
BS
1770 .swappiness = vm_swappiness,
1771 .order = order,
1772 .mem_cgroup = NULL,
1773 .isolate_pages = isolate_pages_global,
327c0e96 1774 .nodemask = nodemask,
66e1707b
BS
1775 };
1776
dd1a239f 1777 return do_try_to_free_pages(zonelist, &sc);
66e1707b
BS
1778}
1779
00f0b825 1780#ifdef CONFIG_CGROUP_MEM_RES_CTLR
66e1707b 1781
e1a1cd59 1782unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
a7885eb8
KM
1783 gfp_t gfp_mask,
1784 bool noswap,
1785 unsigned int swappiness)
66e1707b
BS
1786{
1787 struct scan_control sc = {
66e1707b 1788 .may_writepage = !laptop_mode,
a6dc60f8 1789 .may_unmap = 1,
2e2e4259 1790 .may_swap = !noswap,
66e1707b 1791 .swap_cluster_max = SWAP_CLUSTER_MAX,
a7885eb8 1792 .swappiness = swappiness,
66e1707b
BS
1793 .order = 0,
1794 .mem_cgroup = mem_cont,
1795 .isolate_pages = mem_cgroup_isolate_pages,
327c0e96 1796 .nodemask = NULL, /* we don't care the placement */
66e1707b 1797 };
dac1d27b 1798 struct zonelist *zonelist;
66e1707b 1799
dd1a239f
MG
1800 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1801 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1802 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1803 return do_try_to_free_pages(zonelist, &sc);
66e1707b
BS
1804}
1805#endif
1806
1da177e4
LT
1807/*
1808 * For kswapd, balance_pgdat() will work across all this node's zones until
41858966 1809 * they are all at high_wmark_pages(zone).
1da177e4 1810 *
1da177e4
LT
1811 * Returns the number of pages which were actually freed.
1812 *
1813 * There is special handling here for zones which are full of pinned pages.
1814 * This can happen if the pages are all mlocked, or if they are all used by
1815 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1816 * What we do is to detect the case where all pages in the zone have been
1817 * scanned twice and there has been zero successful reclaim. Mark the zone as
1818 * dead and from now on, only perform a short scan. Basically we're polling
1819 * the zone for when the problem goes away.
1820 *
1821 * kswapd scans the zones in the highmem->normal->dma direction. It skips
41858966
MG
1822 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
1823 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
1824 * lower zones regardless of the number of free pages in the lower zones. This
1825 * interoperates with the page allocator fallback scheme to ensure that aging
1826 * of pages is balanced across the zones.
1da177e4 1827 */
d6277db4 1828static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1da177e4 1829{
1da177e4
LT
1830 int all_zones_ok;
1831 int priority;
1832 int i;
69e05944 1833 unsigned long total_scanned;
1da177e4 1834 struct reclaim_state *reclaim_state = current->reclaim_state;
179e9639
AM
1835 struct scan_control sc = {
1836 .gfp_mask = GFP_KERNEL,
a6dc60f8 1837 .may_unmap = 1,
2e2e4259 1838 .may_swap = 1,
d6277db4
RW
1839 .swap_cluster_max = SWAP_CLUSTER_MAX,
1840 .swappiness = vm_swappiness,
5ad333eb 1841 .order = order,
66e1707b
BS
1842 .mem_cgroup = NULL,
1843 .isolate_pages = isolate_pages_global,
179e9639 1844 };
3bb1a852
MB
1845 /*
1846 * temp_priority is used to remember the scanning priority at which
41858966
MG
1847 * this zone was successfully refilled to
1848 * free_pages == high_wmark_pages(zone).
3bb1a852
MB
1849 */
1850 int temp_priority[MAX_NR_ZONES];
1da177e4
LT
1851
1852loop_again:
1853 total_scanned = 0;
a79311c1 1854 sc.nr_reclaimed = 0;
c0bbbc73 1855 sc.may_writepage = !laptop_mode;
f8891e5e 1856 count_vm_event(PAGEOUTRUN);
1da177e4 1857
3bb1a852
MB
1858 for (i = 0; i < pgdat->nr_zones; i++)
1859 temp_priority[i] = DEF_PRIORITY;
1da177e4
LT
1860
1861 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1862 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1863 unsigned long lru_pages = 0;
1864
f7b7fd8f
RR
1865 /* The swap token gets in the way of swapout... */
1866 if (!priority)
1867 disable_swap_token();
1868
1da177e4
LT
1869 all_zones_ok = 1;
1870
d6277db4
RW
1871 /*
1872 * Scan in the highmem->dma direction for the highest
1873 * zone which needs scanning
1874 */
1875 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1876 struct zone *zone = pgdat->node_zones + i;
1da177e4 1877
d6277db4
RW
1878 if (!populated_zone(zone))
1879 continue;
1da177e4 1880
e815af95
DR
1881 if (zone_is_all_unreclaimable(zone) &&
1882 priority != DEF_PRIORITY)
d6277db4 1883 continue;
1da177e4 1884
556adecb
RR
1885 /*
1886 * Do some background aging of the anon list, to give
1887 * pages a chance to be referenced before reclaiming.
1888 */
14797e23 1889 if (inactive_anon_is_low(zone, &sc))
556adecb
RR
1890 shrink_active_list(SWAP_CLUSTER_MAX, zone,
1891 &sc, priority, 0);
1892
41858966
MG
1893 if (!zone_watermark_ok(zone, order,
1894 high_wmark_pages(zone), 0, 0)) {
d6277db4 1895 end_zone = i;
e1dbeda6 1896 break;
1da177e4 1897 }
1da177e4 1898 }
e1dbeda6
AM
1899 if (i < 0)
1900 goto out;
1901
1da177e4
LT
1902 for (i = 0; i <= end_zone; i++) {
1903 struct zone *zone = pgdat->node_zones + i;
1904
4f98a2fe 1905 lru_pages += zone_lru_pages(zone);
1da177e4
LT
1906 }
1907
1908 /*
1909 * Now scan the zone in the dma->highmem direction, stopping
1910 * at the last zone which needs scanning.
1911 *
1912 * We do this because the page allocator works in the opposite
1913 * direction. This prevents the page allocator from allocating
1914 * pages behind kswapd's direction of progress, which would
1915 * cause too much scanning of the lower zones.
1916 */
1917 for (i = 0; i <= end_zone; i++) {
1918 struct zone *zone = pgdat->node_zones + i;
b15e0905 1919 int nr_slab;
1da177e4 1920
f3fe6512 1921 if (!populated_zone(zone))
1da177e4
LT
1922 continue;
1923
e815af95
DR
1924 if (zone_is_all_unreclaimable(zone) &&
1925 priority != DEF_PRIORITY)
1da177e4
LT
1926 continue;
1927
41858966
MG
1928 if (!zone_watermark_ok(zone, order,
1929 high_wmark_pages(zone), end_zone, 0))
d6277db4 1930 all_zones_ok = 0;
3bb1a852 1931 temp_priority[i] = priority;
1da177e4 1932 sc.nr_scanned = 0;
3bb1a852 1933 note_zone_scanning_priority(zone, priority);
32a4330d
RR
1934 /*
1935 * We put equal pressure on every zone, unless one
1936 * zone has way too many pages free already.
1937 */
41858966
MG
1938 if (!zone_watermark_ok(zone, order,
1939 8*high_wmark_pages(zone), end_zone, 0))
a79311c1 1940 shrink_zone(priority, zone, &sc);
1da177e4 1941 reclaim_state->reclaimed_slab = 0;
b15e0905 1942 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1943 lru_pages);
a79311c1 1944 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
1da177e4 1945 total_scanned += sc.nr_scanned;
e815af95 1946 if (zone_is_all_unreclaimable(zone))
1da177e4 1947 continue;
b15e0905 1948 if (nr_slab == 0 && zone->pages_scanned >=
4f98a2fe 1949 (zone_lru_pages(zone) * 6))
e815af95
DR
1950 zone_set_flag(zone,
1951 ZONE_ALL_UNRECLAIMABLE);
1da177e4
LT
1952 /*
1953 * If we've done a decent amount of scanning and
1954 * the reclaim ratio is low, start doing writepage
1955 * even in laptop mode
1956 */
1957 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
a79311c1 1958 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
1da177e4
LT
1959 sc.may_writepage = 1;
1960 }
1da177e4
LT
1961 if (all_zones_ok)
1962 break; /* kswapd: all done */
1963 /*
1964 * OK, kswapd is getting into trouble. Take a nap, then take
1965 * another pass across the zones.
1966 */
4dd4b920 1967 if (total_scanned && priority < DEF_PRIORITY - 2)
8aa7e847 1968 congestion_wait(BLK_RW_ASYNC, HZ/10);
1da177e4
LT
1969
1970 /*
1971 * We do this so kswapd doesn't build up large priorities for
1972 * example when it is freeing in parallel with allocators. It
1973 * matches the direct reclaim path behaviour in terms of impact
1974 * on zone->*_priority.
1975 */
a79311c1 1976 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
1da177e4
LT
1977 break;
1978 }
1979out:
3bb1a852
MB
1980 /*
1981 * Note within each zone the priority level at which this zone was
1982 * brought into a happy state. So that the next thread which scans this
1983 * zone will start out at that priority level.
1984 */
1da177e4
LT
1985 for (i = 0; i < pgdat->nr_zones; i++) {
1986 struct zone *zone = pgdat->node_zones + i;
1987
3bb1a852 1988 zone->prev_priority = temp_priority[i];
1da177e4
LT
1989 }
1990 if (!all_zones_ok) {
1991 cond_resched();
8357376d
RW
1992
1993 try_to_freeze();
1994
73ce02e9
KM
1995 /*
1996 * Fragmentation may mean that the system cannot be
1997 * rebalanced for high-order allocations in all zones.
1998 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
1999 * it means the zones have been fully scanned and are still
2000 * not balanced. For high-order allocations, there is
2001 * little point trying all over again as kswapd may
2002 * infinite loop.
2003 *
2004 * Instead, recheck all watermarks at order-0 as they
2005 * are the most important. If watermarks are ok, kswapd will go
2006 * back to sleep. High-order users can still perform direct
2007 * reclaim if they wish.
2008 */
2009 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2010 order = sc.order = 0;
2011
1da177e4
LT
2012 goto loop_again;
2013 }
2014
a79311c1 2015 return sc.nr_reclaimed;
1da177e4
LT
2016}
2017
2018/*
2019 * The background pageout daemon, started as a kernel thread
4f98a2fe 2020 * from the init process.
1da177e4
LT
2021 *
2022 * This basically trickles out pages so that we have _some_
2023 * free memory available even if there is no other activity
2024 * that frees anything up. This is needed for things like routing
2025 * etc, where we otherwise might have all activity going on in
2026 * asynchronous contexts that cannot page things out.
2027 *
2028 * If there are applications that are active memory-allocators
2029 * (most normal use), this basically shouldn't matter.
2030 */
2031static int kswapd(void *p)
2032{
2033 unsigned long order;
2034 pg_data_t *pgdat = (pg_data_t*)p;
2035 struct task_struct *tsk = current;
2036 DEFINE_WAIT(wait);
2037 struct reclaim_state reclaim_state = {
2038 .reclaimed_slab = 0,
2039 };
a70f7302 2040 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
1da177e4 2041
cf40bd16
NP
2042 lockdep_set_current_reclaim_state(GFP_KERNEL);
2043
174596a0 2044 if (!cpumask_empty(cpumask))
c5f59f08 2045 set_cpus_allowed_ptr(tsk, cpumask);
1da177e4
LT
2046 current->reclaim_state = &reclaim_state;
2047
2048 /*
2049 * Tell the memory management that we're a "memory allocator",
2050 * and that if we need more memory we should get access to it
2051 * regardless (see "__alloc_pages()"). "kswapd" should
2052 * never get caught in the normal page freeing logic.
2053 *
2054 * (Kswapd normally doesn't need memory anyway, but sometimes
2055 * you need a small amount of memory in order to be able to
2056 * page out something else, and this flag essentially protects
2057 * us from recursively trying to free more memory as we're
2058 * trying to free the first piece of memory in the first place).
2059 */
930d9152 2060 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
83144186 2061 set_freezable();
1da177e4
LT
2062
2063 order = 0;
2064 for ( ; ; ) {
2065 unsigned long new_order;
3e1d1d28 2066
1da177e4
LT
2067 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2068 new_order = pgdat->kswapd_max_order;
2069 pgdat->kswapd_max_order = 0;
2070 if (order < new_order) {
2071 /*
2072 * Don't sleep if someone wants a larger 'order'
2073 * allocation
2074 */
2075 order = new_order;
2076 } else {
b1296cc4
RW
2077 if (!freezing(current))
2078 schedule();
2079
1da177e4
LT
2080 order = pgdat->kswapd_max_order;
2081 }
2082 finish_wait(&pgdat->kswapd_wait, &wait);
2083
b1296cc4
RW
2084 if (!try_to_freeze()) {
2085 /* We can speed up thawing tasks if we don't call
2086 * balance_pgdat after returning from the refrigerator
2087 */
2088 balance_pgdat(pgdat, order);
2089 }
1da177e4
LT
2090 }
2091 return 0;
2092}
2093
2094/*
2095 * A zone is low on free memory, so wake its kswapd task to service it.
2096 */
2097void wakeup_kswapd(struct zone *zone, int order)
2098{
2099 pg_data_t *pgdat;
2100
f3fe6512 2101 if (!populated_zone(zone))
1da177e4
LT
2102 return;
2103
2104 pgdat = zone->zone_pgdat;
41858966 2105 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
1da177e4
LT
2106 return;
2107 if (pgdat->kswapd_max_order < order)
2108 pgdat->kswapd_max_order = order;
02a0e53d 2109 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1da177e4 2110 return;
8d0986e2 2111 if (!waitqueue_active(&pgdat->kswapd_wait))
1da177e4 2112 return;
8d0986e2 2113 wake_up_interruptible(&pgdat->kswapd_wait);
1da177e4
LT
2114}
2115
4f98a2fe
RR
2116unsigned long global_lru_pages(void)
2117{
2118 return global_page_state(NR_ACTIVE_ANON)
2119 + global_page_state(NR_ACTIVE_FILE)
2120 + global_page_state(NR_INACTIVE_ANON)
2121 + global_page_state(NR_INACTIVE_FILE);
2122}
2123
c6f37f12 2124#ifdef CONFIG_HIBERNATION
1da177e4 2125/*
d6277db4 2126 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
d979677c 2127 * from LRU lists system-wide, for given pass and priority.
d6277db4
RW
2128 *
2129 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
2130 */
d979677c 2131static void shrink_all_zones(unsigned long nr_pages, int prio,
e07aa05b 2132 int pass, struct scan_control *sc)
d6277db4
RW
2133{
2134 struct zone *zone;
d979677c 2135 unsigned long nr_reclaimed = 0;
d6277db4 2136
ee99c71c 2137 for_each_populated_zone(zone) {
0cb57258 2138 enum lru_list l;
d6277db4 2139
e815af95 2140 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
d6277db4
RW
2141 continue;
2142
894bc310 2143 for_each_evictable_lru(l) {
0cb57258
JW
2144 enum zone_stat_item ls = NR_LRU_BASE + l;
2145 unsigned long lru_pages = zone_page_state(zone, ls);
2146
894bc310 2147 /* For pass = 0, we don't shrink the active list */
0cb57258
JW
2148 if (pass == 0 && (l == LRU_ACTIVE_ANON ||
2149 l == LRU_ACTIVE_FILE))
b69408e8
CL
2150 continue;
2151
6e08a369
WF
2152 zone->lru[l].nr_saved_scan += (lru_pages >> prio) + 1;
2153 if (zone->lru[l].nr_saved_scan >= nr_pages || pass > 3) {
0cb57258
JW
2154 unsigned long nr_to_scan;
2155
6e08a369 2156 zone->lru[l].nr_saved_scan = 0;
0cb57258 2157 nr_to_scan = min(nr_pages, lru_pages);
d979677c 2158 nr_reclaimed += shrink_list(l, nr_to_scan, zone,
b69408e8 2159 sc, prio);
d979677c 2160 if (nr_reclaimed >= nr_pages) {
a21e2553 2161 sc->nr_reclaimed += nr_reclaimed;
d979677c
MK
2162 return;
2163 }
d6277db4
RW
2164 }
2165 }
d6277db4 2166 }
a21e2553 2167 sc->nr_reclaimed += nr_reclaimed;
d6277db4
RW
2168}
2169
2170/*
2171 * Try to free `nr_pages' of memory, system-wide, and return the number of
2172 * freed pages.
2173 *
2174 * Rather than trying to age LRUs the aim is to preserve the overall
2175 * LRU order by reclaiming preferentially
2176 * inactive > active > active referenced > active mapped
1da177e4 2177 */
69e05944 2178unsigned long shrink_all_memory(unsigned long nr_pages)
1da177e4 2179{
d6277db4 2180 unsigned long lru_pages, nr_slab;
d6277db4
RW
2181 int pass;
2182 struct reclaim_state reclaim_state;
d6277db4
RW
2183 struct scan_control sc = {
2184 .gfp_mask = GFP_KERNEL,
a6dc60f8 2185 .may_unmap = 0,
d6277db4 2186 .may_writepage = 1,
66e1707b 2187 .isolate_pages = isolate_pages_global,
a21e2553 2188 .nr_reclaimed = 0,
1da177e4
LT
2189 };
2190
2191 current->reclaim_state = &reclaim_state;
69e05944 2192
4f98a2fe 2193 lru_pages = global_lru_pages();
972d1a7b 2194 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
d6277db4
RW
2195 /* If slab caches are huge, it's better to hit them first */
2196 while (nr_slab >= lru_pages) {
2197 reclaim_state.reclaimed_slab = 0;
2198 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
2199 if (!reclaim_state.reclaimed_slab)
1da177e4 2200 break;
d6277db4 2201
d979677c
MK
2202 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2203 if (sc.nr_reclaimed >= nr_pages)
d6277db4
RW
2204 goto out;
2205
2206 nr_slab -= reclaim_state.reclaimed_slab;
1da177e4 2207 }
d6277db4
RW
2208
2209 /*
2210 * We try to shrink LRUs in 5 passes:
2211 * 0 = Reclaim from inactive_list only
2212 * 1 = Reclaim from active list but don't reclaim mapped
2213 * 2 = 2nd pass of type 1
2214 * 3 = Reclaim mapped (normal reclaim)
2215 * 4 = 2nd pass of type 3
2216 */
2217 for (pass = 0; pass < 5; pass++) {
2218 int prio;
2219
d6277db4 2220 /* Force reclaiming mapped pages in the passes #3 and #4 */
3049103d 2221 if (pass > 2)
a6dc60f8 2222 sc.may_unmap = 1;
d6277db4
RW
2223
2224 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
d979677c 2225 unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed;
d6277db4 2226
d6277db4 2227 sc.nr_scanned = 0;
9786bf84 2228 sc.swap_cluster_max = nr_to_scan;
d979677c
MK
2229 shrink_all_zones(nr_to_scan, prio, pass, &sc);
2230 if (sc.nr_reclaimed >= nr_pages)
d6277db4
RW
2231 goto out;
2232
2233 reclaim_state.reclaimed_slab = 0;
76395d37 2234 shrink_slab(sc.nr_scanned, sc.gfp_mask,
4f98a2fe 2235 global_lru_pages());
d979677c
MK
2236 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2237 if (sc.nr_reclaimed >= nr_pages)
d6277db4
RW
2238 goto out;
2239
2240 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
8aa7e847 2241 congestion_wait(BLK_RW_ASYNC, HZ / 10);
d6277db4 2242 }
248a0301 2243 }
d6277db4
RW
2244
2245 /*
d979677c
MK
2246 * If sc.nr_reclaimed = 0, we could not shrink LRUs, but there may be
2247 * something in slab caches
d6277db4 2248 */
d979677c 2249 if (!sc.nr_reclaimed) {
d6277db4
RW
2250 do {
2251 reclaim_state.reclaimed_slab = 0;
4f98a2fe 2252 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
d979677c
MK
2253 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2254 } while (sc.nr_reclaimed < nr_pages &&
2255 reclaim_state.reclaimed_slab > 0);
76395d37 2256 }
d6277db4 2257
d979677c 2258
d6277db4 2259out:
1da177e4 2260 current->reclaim_state = NULL;
d6277db4 2261
d979677c 2262 return sc.nr_reclaimed;
1da177e4 2263}
c6f37f12 2264#endif /* CONFIG_HIBERNATION */
1da177e4 2265
1da177e4
LT
2266/* It's optimal to keep kswapds on the same CPUs as their memory, but
2267 not required for correctness. So if the last cpu in a node goes
2268 away, we get changed to run anywhere: as the first one comes back,
2269 restore their cpu bindings. */
9c7b216d 2270static int __devinit cpu_callback(struct notifier_block *nfb,
69e05944 2271 unsigned long action, void *hcpu)
1da177e4 2272{
58c0a4a7 2273 int nid;
1da177e4 2274
8bb78442 2275 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
58c0a4a7 2276 for_each_node_state(nid, N_HIGH_MEMORY) {
c5f59f08 2277 pg_data_t *pgdat = NODE_DATA(nid);
a70f7302
RR
2278 const struct cpumask *mask;
2279
2280 mask = cpumask_of_node(pgdat->node_id);
c5f59f08 2281
3e597945 2282 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
1da177e4 2283 /* One of our CPUs online: restore mask */
c5f59f08 2284 set_cpus_allowed_ptr(pgdat->kswapd, mask);
1da177e4
LT
2285 }
2286 }
2287 return NOTIFY_OK;
2288}
1da177e4 2289
3218ae14
YG
2290/*
2291 * This kswapd start function will be called by init and node-hot-add.
2292 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2293 */
2294int kswapd_run(int nid)
2295{
2296 pg_data_t *pgdat = NODE_DATA(nid);
2297 int ret = 0;
2298
2299 if (pgdat->kswapd)
2300 return 0;
2301
2302 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2303 if (IS_ERR(pgdat->kswapd)) {
2304 /* failure at boot is fatal */
2305 BUG_ON(system_state == SYSTEM_BOOTING);
2306 printk("Failed to start kswapd on node %d\n",nid);
2307 ret = -1;
2308 }
2309 return ret;
2310}
2311
1da177e4
LT
2312static int __init kswapd_init(void)
2313{
3218ae14 2314 int nid;
69e05944 2315
1da177e4 2316 swap_setup();
9422ffba 2317 for_each_node_state(nid, N_HIGH_MEMORY)
3218ae14 2318 kswapd_run(nid);
1da177e4
LT
2319 hotcpu_notifier(cpu_callback, 0);
2320 return 0;
2321}
2322
2323module_init(kswapd_init)
9eeff239
CL
2324
2325#ifdef CONFIG_NUMA
2326/*
2327 * Zone reclaim mode
2328 *
2329 * If non-zero call zone_reclaim when the number of free pages falls below
2330 * the watermarks.
9eeff239
CL
2331 */
2332int zone_reclaim_mode __read_mostly;
2333
1b2ffb78 2334#define RECLAIM_OFF 0
7d03431c 2335#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
1b2ffb78
CL
2336#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2337#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2338
a92f7126
CL
2339/*
2340 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2341 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2342 * a zone.
2343 */
2344#define ZONE_RECLAIM_PRIORITY 4
2345
9614634f
CL
2346/*
2347 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2348 * occur.
2349 */
2350int sysctl_min_unmapped_ratio = 1;
2351
0ff38490
CL
2352/*
2353 * If the number of slab pages in a zone grows beyond this percentage then
2354 * slab reclaim needs to occur.
2355 */
2356int sysctl_min_slab_ratio = 5;
2357
90afa5de
MG
2358static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
2359{
2360 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
2361 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
2362 zone_page_state(zone, NR_ACTIVE_FILE);
2363
2364 /*
2365 * It's possible for there to be more file mapped pages than
2366 * accounted for by the pages on the file LRU lists because
2367 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2368 */
2369 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
2370}
2371
2372/* Work out how many page cache pages we can reclaim in this reclaim_mode */
2373static long zone_pagecache_reclaimable(struct zone *zone)
2374{
2375 long nr_pagecache_reclaimable;
2376 long delta = 0;
2377
2378 /*
2379 * If RECLAIM_SWAP is set, then all file pages are considered
2380 * potentially reclaimable. Otherwise, we have to worry about
2381 * pages like swapcache and zone_unmapped_file_pages() provides
2382 * a better estimate
2383 */
2384 if (zone_reclaim_mode & RECLAIM_SWAP)
2385 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
2386 else
2387 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
2388
2389 /* If we can't clean pages, remove dirty pages from consideration */
2390 if (!(zone_reclaim_mode & RECLAIM_WRITE))
2391 delta += zone_page_state(zone, NR_FILE_DIRTY);
2392
2393 /* Watch for any possible underflows due to delta */
2394 if (unlikely(delta > nr_pagecache_reclaimable))
2395 delta = nr_pagecache_reclaimable;
2396
2397 return nr_pagecache_reclaimable - delta;
2398}
2399
9eeff239
CL
2400/*
2401 * Try to free up some pages from this zone through reclaim.
2402 */
179e9639 2403static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
9eeff239 2404{
7fb2d46d 2405 /* Minimum pages needed in order to stay on node */
69e05944 2406 const unsigned long nr_pages = 1 << order;
9eeff239
CL
2407 struct task_struct *p = current;
2408 struct reclaim_state reclaim_state;
8695949a 2409 int priority;
179e9639
AM
2410 struct scan_control sc = {
2411 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
a6dc60f8 2412 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2e2e4259 2413 .may_swap = 1,
69e05944
AM
2414 .swap_cluster_max = max_t(unsigned long, nr_pages,
2415 SWAP_CLUSTER_MAX),
179e9639 2416 .gfp_mask = gfp_mask,
d6277db4 2417 .swappiness = vm_swappiness,
bd2f6199 2418 .order = order,
66e1707b 2419 .isolate_pages = isolate_pages_global,
179e9639 2420 };
83e33a47 2421 unsigned long slab_reclaimable;
9eeff239
CL
2422
2423 disable_swap_token();
9eeff239 2424 cond_resched();
d4f7796e
CL
2425 /*
2426 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2427 * and we also need to be able to write out pages for RECLAIM_WRITE
2428 * and RECLAIM_SWAP.
2429 */
2430 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
9eeff239
CL
2431 reclaim_state.reclaimed_slab = 0;
2432 p->reclaim_state = &reclaim_state;
c84db23c 2433
90afa5de 2434 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
0ff38490
CL
2435 /*
2436 * Free memory by calling shrink zone with increasing
2437 * priorities until we have enough memory freed.
2438 */
2439 priority = ZONE_RECLAIM_PRIORITY;
2440 do {
3bb1a852 2441 note_zone_scanning_priority(zone, priority);
a79311c1 2442 shrink_zone(priority, zone, &sc);
0ff38490 2443 priority--;
a79311c1 2444 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
0ff38490 2445 }
c84db23c 2446
83e33a47
CL
2447 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2448 if (slab_reclaimable > zone->min_slab_pages) {
2a16e3f4 2449 /*
7fb2d46d 2450 * shrink_slab() does not currently allow us to determine how
0ff38490
CL
2451 * many pages were freed in this zone. So we take the current
2452 * number of slab pages and shake the slab until it is reduced
2453 * by the same nr_pages that we used for reclaiming unmapped
2454 * pages.
2a16e3f4 2455 *
0ff38490
CL
2456 * Note that shrink_slab will free memory on all zones and may
2457 * take a long time.
2a16e3f4 2458 */
0ff38490 2459 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
83e33a47
CL
2460 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2461 slab_reclaimable - nr_pages)
0ff38490 2462 ;
83e33a47
CL
2463
2464 /*
2465 * Update nr_reclaimed by the number of slab pages we
2466 * reclaimed from this zone.
2467 */
a79311c1 2468 sc.nr_reclaimed += slab_reclaimable -
83e33a47 2469 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2a16e3f4
CL
2470 }
2471
9eeff239 2472 p->reclaim_state = NULL;
d4f7796e 2473 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
a79311c1 2474 return sc.nr_reclaimed >= nr_pages;
9eeff239 2475}
179e9639
AM
2476
2477int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2478{
179e9639 2479 int node_id;
d773ed6b 2480 int ret;
179e9639
AM
2481
2482 /*
0ff38490
CL
2483 * Zone reclaim reclaims unmapped file backed pages and
2484 * slab pages if we are over the defined limits.
34aa1330 2485 *
9614634f
CL
2486 * A small portion of unmapped file backed pages is needed for
2487 * file I/O otherwise pages read by file I/O will be immediately
2488 * thrown out if the zone is overallocated. So we do not reclaim
2489 * if less than a specified percentage of the zone is used by
2490 * unmapped file backed pages.
179e9639 2491 */
90afa5de
MG
2492 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
2493 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
fa5e084e 2494 return ZONE_RECLAIM_FULL;
179e9639 2495
d773ed6b 2496 if (zone_is_all_unreclaimable(zone))
fa5e084e 2497 return ZONE_RECLAIM_FULL;
d773ed6b 2498
179e9639 2499 /*
d773ed6b 2500 * Do not scan if the allocation should not be delayed.
179e9639 2501 */
d773ed6b 2502 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
fa5e084e 2503 return ZONE_RECLAIM_NOSCAN;
179e9639
AM
2504
2505 /*
2506 * Only run zone reclaim on the local zone or on zones that do not
2507 * have associated processors. This will favor the local processor
2508 * over remote processors and spread off node memory allocations
2509 * as wide as possible.
2510 */
89fa3024 2511 node_id = zone_to_nid(zone);
37c0708d 2512 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
fa5e084e 2513 return ZONE_RECLAIM_NOSCAN;
d773ed6b
DR
2514
2515 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
fa5e084e
MG
2516 return ZONE_RECLAIM_NOSCAN;
2517
d773ed6b
DR
2518 ret = __zone_reclaim(zone, gfp_mask, order);
2519 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2520
24cf7251
MG
2521 if (!ret)
2522 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
2523
d773ed6b 2524 return ret;
179e9639 2525}
9eeff239 2526#endif
894bc310 2527
894bc310
LS
2528/*
2529 * page_evictable - test whether a page is evictable
2530 * @page: the page to test
2531 * @vma: the VMA in which the page is or will be mapped, may be NULL
2532 *
2533 * Test whether page is evictable--i.e., should be placed on active/inactive
b291f000
NP
2534 * lists vs unevictable list. The vma argument is !NULL when called from the
2535 * fault path to determine how to instantate a new page.
894bc310
LS
2536 *
2537 * Reasons page might not be evictable:
ba9ddf49 2538 * (1) page's mapping marked unevictable
b291f000 2539 * (2) page is part of an mlocked VMA
ba9ddf49 2540 *
894bc310
LS
2541 */
2542int page_evictable(struct page *page, struct vm_area_struct *vma)
2543{
2544
ba9ddf49
LS
2545 if (mapping_unevictable(page_mapping(page)))
2546 return 0;
2547
b291f000
NP
2548 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2549 return 0;
894bc310
LS
2550
2551 return 1;
2552}
89e004ea
LS
2553
2554/**
2555 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2556 * @page: page to check evictability and move to appropriate lru list
2557 * @zone: zone page is in
2558 *
2559 * Checks a page for evictability and moves the page to the appropriate
2560 * zone lru list.
2561 *
2562 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2563 * have PageUnevictable set.
2564 */
2565static void check_move_unevictable_page(struct page *page, struct zone *zone)
2566{
2567 VM_BUG_ON(PageActive(page));
2568
2569retry:
2570 ClearPageUnevictable(page);
2571 if (page_evictable(page, NULL)) {
2572 enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
af936a16 2573
89e004ea
LS
2574 __dec_zone_state(zone, NR_UNEVICTABLE);
2575 list_move(&page->lru, &zone->lru[l].list);
08e552c6 2576 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
89e004ea
LS
2577 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2578 __count_vm_event(UNEVICTABLE_PGRESCUED);
2579 } else {
2580 /*
2581 * rotate unevictable list
2582 */
2583 SetPageUnevictable(page);
2584 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
08e552c6 2585 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
89e004ea
LS
2586 if (page_evictable(page, NULL))
2587 goto retry;
2588 }
2589}
2590
2591/**
2592 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2593 * @mapping: struct address_space to scan for evictable pages
2594 *
2595 * Scan all pages in mapping. Check unevictable pages for
2596 * evictability and move them to the appropriate zone lru list.
2597 */
2598void scan_mapping_unevictable_pages(struct address_space *mapping)
2599{
2600 pgoff_t next = 0;
2601 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2602 PAGE_CACHE_SHIFT;
2603 struct zone *zone;
2604 struct pagevec pvec;
2605
2606 if (mapping->nrpages == 0)
2607 return;
2608
2609 pagevec_init(&pvec, 0);
2610 while (next < end &&
2611 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2612 int i;
2613 int pg_scanned = 0;
2614
2615 zone = NULL;
2616
2617 for (i = 0; i < pagevec_count(&pvec); i++) {
2618 struct page *page = pvec.pages[i];
2619 pgoff_t page_index = page->index;
2620 struct zone *pagezone = page_zone(page);
2621
2622 pg_scanned++;
2623 if (page_index > next)
2624 next = page_index;
2625 next++;
2626
2627 if (pagezone != zone) {
2628 if (zone)
2629 spin_unlock_irq(&zone->lru_lock);
2630 zone = pagezone;
2631 spin_lock_irq(&zone->lru_lock);
2632 }
2633
2634 if (PageLRU(page) && PageUnevictable(page))
2635 check_move_unevictable_page(page, zone);
2636 }
2637 if (zone)
2638 spin_unlock_irq(&zone->lru_lock);
2639 pagevec_release(&pvec);
2640
2641 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2642 }
2643
2644}
af936a16
LS
2645
2646/**
2647 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2648 * @zone - zone of which to scan the unevictable list
2649 *
2650 * Scan @zone's unevictable LRU lists to check for pages that have become
2651 * evictable. Move those that have to @zone's inactive list where they
2652 * become candidates for reclaim, unless shrink_inactive_zone() decides
2653 * to reactivate them. Pages that are still unevictable are rotated
2654 * back onto @zone's unevictable list.
2655 */
2656#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
14b90b22 2657static void scan_zone_unevictable_pages(struct zone *zone)
af936a16
LS
2658{
2659 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2660 unsigned long scan;
2661 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2662
2663 while (nr_to_scan > 0) {
2664 unsigned long batch_size = min(nr_to_scan,
2665 SCAN_UNEVICTABLE_BATCH_SIZE);
2666
2667 spin_lock_irq(&zone->lru_lock);
2668 for (scan = 0; scan < batch_size; scan++) {
2669 struct page *page = lru_to_page(l_unevictable);
2670
2671 if (!trylock_page(page))
2672 continue;
2673
2674 prefetchw_prev_lru_page(page, l_unevictable, flags);
2675
2676 if (likely(PageLRU(page) && PageUnevictable(page)))
2677 check_move_unevictable_page(page, zone);
2678
2679 unlock_page(page);
2680 }
2681 spin_unlock_irq(&zone->lru_lock);
2682
2683 nr_to_scan -= batch_size;
2684 }
2685}
2686
2687
2688/**
2689 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2690 *
2691 * A really big hammer: scan all zones' unevictable LRU lists to check for
2692 * pages that have become evictable. Move those back to the zones'
2693 * inactive list where they become candidates for reclaim.
2694 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2695 * and we add swap to the system. As such, it runs in the context of a task
2696 * that has possibly/probably made some previously unevictable pages
2697 * evictable.
2698 */
ff30153b 2699static void scan_all_zones_unevictable_pages(void)
af936a16
LS
2700{
2701 struct zone *zone;
2702
2703 for_each_zone(zone) {
2704 scan_zone_unevictable_pages(zone);
2705 }
2706}
2707
2708/*
2709 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2710 * all nodes' unevictable lists for evictable pages
2711 */
2712unsigned long scan_unevictable_pages;
2713
2714int scan_unevictable_handler(struct ctl_table *table, int write,
2715 struct file *file, void __user *buffer,
2716 size_t *length, loff_t *ppos)
2717{
2718 proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
2719
2720 if (write && *(unsigned long *)table->data)
2721 scan_all_zones_unevictable_pages();
2722
2723 scan_unevictable_pages = 0;
2724 return 0;
2725}
2726
2727/*
2728 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2729 * a specified node's per zone unevictable lists for evictable pages.
2730 */
2731
2732static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2733 struct sysdev_attribute *attr,
2734 char *buf)
2735{
2736 return sprintf(buf, "0\n"); /* always zero; should fit... */
2737}
2738
2739static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2740 struct sysdev_attribute *attr,
2741 const char *buf, size_t count)
2742{
2743 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2744 struct zone *zone;
2745 unsigned long res;
2746 unsigned long req = strict_strtoul(buf, 10, &res);
2747
2748 if (!req)
2749 return 1; /* zero is no-op */
2750
2751 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2752 if (!populated_zone(zone))
2753 continue;
2754 scan_zone_unevictable_pages(zone);
2755 }
2756 return 1;
2757}
2758
2759
2760static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2761 read_scan_unevictable_node,
2762 write_scan_unevictable_node);
2763
2764int scan_unevictable_register_node(struct node *node)
2765{
2766 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2767}
2768
2769void scan_unevictable_unregister_node(struct node *node)
2770{
2771 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
2772}
2773