]> git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - mm/vmscan.c
Merge branch 'sh/for-2.6.28' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal...
[mirror_ubuntu-bionic-kernel.git] / mm / vmscan.c
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>
22 #include <linux/vmstat.h>
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>
37 #include <linux/delay.h>
38 #include <linux/kthread.h>
39 #include <linux/freezer.h>
40 #include <linux/memcontrol.h>
41 #include <linux/delayacct.h>
42 #include <linux/sysctl.h>
43
44 #include <asm/tlbflush.h>
45 #include <asm/div64.h>
46
47 #include <linux/swapops.h>
48
49 #include "internal.h"
50
51 struct scan_control {
52 /* Incremented by the number of inactive pages that were scanned */
53 unsigned long nr_scanned;
54
55 /* This context's GFP mask */
56 gfp_t gfp_mask;
57
58 int may_writepage;
59
60 /* Can pages be swapped as part of reclaim? */
61 int may_swap;
62
63 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
64 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
65 * In this context, it doesn't matter that we scan the
66 * whole list at once. */
67 int swap_cluster_max;
68
69 int swappiness;
70
71 int all_unreclaimable;
72
73 int order;
74
75 /* Which cgroup do we reclaim from */
76 struct mem_cgroup *mem_cgroup;
77
78 /* Pluggable isolate pages callback */
79 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
80 unsigned long *scanned, int order, int mode,
81 struct zone *z, struct mem_cgroup *mem_cont,
82 int active, int file);
83 };
84
85 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
86
87 #ifdef ARCH_HAS_PREFETCH
88 #define prefetch_prev_lru_page(_page, _base, _field) \
89 do { \
90 if ((_page)->lru.prev != _base) { \
91 struct page *prev; \
92 \
93 prev = lru_to_page(&(_page->lru)); \
94 prefetch(&prev->_field); \
95 } \
96 } while (0)
97 #else
98 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
99 #endif
100
101 #ifdef ARCH_HAS_PREFETCHW
102 #define prefetchw_prev_lru_page(_page, _base, _field) \
103 do { \
104 if ((_page)->lru.prev != _base) { \
105 struct page *prev; \
106 \
107 prev = lru_to_page(&(_page->lru)); \
108 prefetchw(&prev->_field); \
109 } \
110 } while (0)
111 #else
112 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
113 #endif
114
115 /*
116 * From 0 .. 100. Higher means more swappy.
117 */
118 int vm_swappiness = 60;
119 long vm_total_pages; /* The total number of pages which the VM controls */
120
121 static LIST_HEAD(shrinker_list);
122 static DECLARE_RWSEM(shrinker_rwsem);
123
124 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
125 #define scan_global_lru(sc) (!(sc)->mem_cgroup)
126 #else
127 #define scan_global_lru(sc) (1)
128 #endif
129
130 /*
131 * Add a shrinker callback to be called from the vm
132 */
133 void register_shrinker(struct shrinker *shrinker)
134 {
135 shrinker->nr = 0;
136 down_write(&shrinker_rwsem);
137 list_add_tail(&shrinker->list, &shrinker_list);
138 up_write(&shrinker_rwsem);
139 }
140 EXPORT_SYMBOL(register_shrinker);
141
142 /*
143 * Remove one
144 */
145 void unregister_shrinker(struct shrinker *shrinker)
146 {
147 down_write(&shrinker_rwsem);
148 list_del(&shrinker->list);
149 up_write(&shrinker_rwsem);
150 }
151 EXPORT_SYMBOL(unregister_shrinker);
152
153 #define SHRINK_BATCH 128
154 /*
155 * Call the shrink functions to age shrinkable caches
156 *
157 * Here we assume it costs one seek to replace a lru page and that it also
158 * takes a seek to recreate a cache object. With this in mind we age equal
159 * percentages of the lru and ageable caches. This should balance the seeks
160 * generated by these structures.
161 *
162 * If the vm encountered mapped pages on the LRU it increase the pressure on
163 * slab to avoid swapping.
164 *
165 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
166 *
167 * `lru_pages' represents the number of on-LRU pages in all the zones which
168 * are eligible for the caller's allocation attempt. It is used for balancing
169 * slab reclaim versus page reclaim.
170 *
171 * Returns the number of slab objects which we shrunk.
172 */
173 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
174 unsigned long lru_pages)
175 {
176 struct shrinker *shrinker;
177 unsigned long ret = 0;
178
179 if (scanned == 0)
180 scanned = SWAP_CLUSTER_MAX;
181
182 if (!down_read_trylock(&shrinker_rwsem))
183 return 1; /* Assume we'll be able to shrink next time */
184
185 list_for_each_entry(shrinker, &shrinker_list, list) {
186 unsigned long long delta;
187 unsigned long total_scan;
188 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
189
190 delta = (4 * scanned) / shrinker->seeks;
191 delta *= max_pass;
192 do_div(delta, lru_pages + 1);
193 shrinker->nr += delta;
194 if (shrinker->nr < 0) {
195 printk(KERN_ERR "%s: nr=%ld\n",
196 __func__, shrinker->nr);
197 shrinker->nr = max_pass;
198 }
199
200 /*
201 * Avoid risking looping forever due to too large nr value:
202 * never try to free more than twice the estimate number of
203 * freeable entries.
204 */
205 if (shrinker->nr > max_pass * 2)
206 shrinker->nr = max_pass * 2;
207
208 total_scan = shrinker->nr;
209 shrinker->nr = 0;
210
211 while (total_scan >= SHRINK_BATCH) {
212 long this_scan = SHRINK_BATCH;
213 int shrink_ret;
214 int nr_before;
215
216 nr_before = (*shrinker->shrink)(0, gfp_mask);
217 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
218 if (shrink_ret == -1)
219 break;
220 if (shrink_ret < nr_before)
221 ret += nr_before - shrink_ret;
222 count_vm_events(SLABS_SCANNED, this_scan);
223 total_scan -= this_scan;
224
225 cond_resched();
226 }
227
228 shrinker->nr += total_scan;
229 }
230 up_read(&shrinker_rwsem);
231 return ret;
232 }
233
234 /* Called without lock on whether page is mapped, so answer is unstable */
235 static inline int page_mapping_inuse(struct page *page)
236 {
237 struct address_space *mapping;
238
239 /* Page is in somebody's page tables. */
240 if (page_mapped(page))
241 return 1;
242
243 /* Be more reluctant to reclaim swapcache than pagecache */
244 if (PageSwapCache(page))
245 return 1;
246
247 mapping = page_mapping(page);
248 if (!mapping)
249 return 0;
250
251 /* File is mmap'd by somebody? */
252 return mapping_mapped(mapping);
253 }
254
255 static inline int is_page_cache_freeable(struct page *page)
256 {
257 return page_count(page) - !!PagePrivate(page) == 2;
258 }
259
260 static int may_write_to_queue(struct backing_dev_info *bdi)
261 {
262 if (current->flags & PF_SWAPWRITE)
263 return 1;
264 if (!bdi_write_congested(bdi))
265 return 1;
266 if (bdi == current->backing_dev_info)
267 return 1;
268 return 0;
269 }
270
271 /*
272 * We detected a synchronous write error writing a page out. Probably
273 * -ENOSPC. We need to propagate that into the address_space for a subsequent
274 * fsync(), msync() or close().
275 *
276 * The tricky part is that after writepage we cannot touch the mapping: nothing
277 * prevents it from being freed up. But we have a ref on the page and once
278 * that page is locked, the mapping is pinned.
279 *
280 * We're allowed to run sleeping lock_page() here because we know the caller has
281 * __GFP_FS.
282 */
283 static void handle_write_error(struct address_space *mapping,
284 struct page *page, int error)
285 {
286 lock_page(page);
287 if (page_mapping(page) == mapping)
288 mapping_set_error(mapping, error);
289 unlock_page(page);
290 }
291
292 /* Request for sync pageout. */
293 enum pageout_io {
294 PAGEOUT_IO_ASYNC,
295 PAGEOUT_IO_SYNC,
296 };
297
298 /* possible outcome of pageout() */
299 typedef enum {
300 /* failed to write page out, page is locked */
301 PAGE_KEEP,
302 /* move page to the active list, page is locked */
303 PAGE_ACTIVATE,
304 /* page has been sent to the disk successfully, page is unlocked */
305 PAGE_SUCCESS,
306 /* page is clean and locked */
307 PAGE_CLEAN,
308 } pageout_t;
309
310 /*
311 * pageout is called by shrink_page_list() for each dirty page.
312 * Calls ->writepage().
313 */
314 static pageout_t pageout(struct page *page, struct address_space *mapping,
315 enum pageout_io sync_writeback)
316 {
317 /*
318 * If the page is dirty, only perform writeback if that write
319 * will be non-blocking. To prevent this allocation from being
320 * stalled by pagecache activity. But note that there may be
321 * stalls if we need to run get_block(). We could test
322 * PagePrivate for that.
323 *
324 * If this process is currently in generic_file_write() against
325 * this page's queue, we can perform writeback even if that
326 * will block.
327 *
328 * If the page is swapcache, write it back even if that would
329 * block, for some throttling. This happens by accident, because
330 * swap_backing_dev_info is bust: it doesn't reflect the
331 * congestion state of the swapdevs. Easy to fix, if needed.
332 * See swapfile.c:page_queue_congested().
333 */
334 if (!is_page_cache_freeable(page))
335 return PAGE_KEEP;
336 if (!mapping) {
337 /*
338 * Some data journaling orphaned pages can have
339 * page->mapping == NULL while being dirty with clean buffers.
340 */
341 if (PagePrivate(page)) {
342 if (try_to_free_buffers(page)) {
343 ClearPageDirty(page);
344 printk("%s: orphaned page\n", __func__);
345 return PAGE_CLEAN;
346 }
347 }
348 return PAGE_KEEP;
349 }
350 if (mapping->a_ops->writepage == NULL)
351 return PAGE_ACTIVATE;
352 if (!may_write_to_queue(mapping->backing_dev_info))
353 return PAGE_KEEP;
354
355 if (clear_page_dirty_for_io(page)) {
356 int res;
357 struct writeback_control wbc = {
358 .sync_mode = WB_SYNC_NONE,
359 .nr_to_write = SWAP_CLUSTER_MAX,
360 .range_start = 0,
361 .range_end = LLONG_MAX,
362 .nonblocking = 1,
363 .for_reclaim = 1,
364 };
365
366 SetPageReclaim(page);
367 res = mapping->a_ops->writepage(page, &wbc);
368 if (res < 0)
369 handle_write_error(mapping, page, res);
370 if (res == AOP_WRITEPAGE_ACTIVATE) {
371 ClearPageReclaim(page);
372 return PAGE_ACTIVATE;
373 }
374
375 /*
376 * Wait on writeback if requested to. This happens when
377 * direct reclaiming a large contiguous area and the
378 * first attempt to free a range of pages fails.
379 */
380 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
381 wait_on_page_writeback(page);
382
383 if (!PageWriteback(page)) {
384 /* synchronous write or broken a_ops? */
385 ClearPageReclaim(page);
386 }
387 inc_zone_page_state(page, NR_VMSCAN_WRITE);
388 return PAGE_SUCCESS;
389 }
390
391 return PAGE_CLEAN;
392 }
393
394 /*
395 * Same as remove_mapping, but if the page is removed from the mapping, it
396 * gets returned with a refcount of 0.
397 */
398 static int __remove_mapping(struct address_space *mapping, struct page *page)
399 {
400 BUG_ON(!PageLocked(page));
401 BUG_ON(mapping != page_mapping(page));
402
403 spin_lock_irq(&mapping->tree_lock);
404 /*
405 * The non racy check for a busy page.
406 *
407 * Must be careful with the order of the tests. When someone has
408 * a ref to the page, it may be possible that they dirty it then
409 * drop the reference. So if PageDirty is tested before page_count
410 * here, then the following race may occur:
411 *
412 * get_user_pages(&page);
413 * [user mapping goes away]
414 * write_to(page);
415 * !PageDirty(page) [good]
416 * SetPageDirty(page);
417 * put_page(page);
418 * !page_count(page) [good, discard it]
419 *
420 * [oops, our write_to data is lost]
421 *
422 * Reversing the order of the tests ensures such a situation cannot
423 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
424 * load is not satisfied before that of page->_count.
425 *
426 * Note that if SetPageDirty is always performed via set_page_dirty,
427 * and thus under tree_lock, then this ordering is not required.
428 */
429 if (!page_freeze_refs(page, 2))
430 goto cannot_free;
431 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
432 if (unlikely(PageDirty(page))) {
433 page_unfreeze_refs(page, 2);
434 goto cannot_free;
435 }
436
437 if (PageSwapCache(page)) {
438 swp_entry_t swap = { .val = page_private(page) };
439 __delete_from_swap_cache(page);
440 spin_unlock_irq(&mapping->tree_lock);
441 swap_free(swap);
442 } else {
443 __remove_from_page_cache(page);
444 spin_unlock_irq(&mapping->tree_lock);
445 }
446
447 return 1;
448
449 cannot_free:
450 spin_unlock_irq(&mapping->tree_lock);
451 return 0;
452 }
453
454 /*
455 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
456 * someone else has a ref on the page, abort and return 0. If it was
457 * successfully detached, return 1. Assumes the caller has a single ref on
458 * this page.
459 */
460 int remove_mapping(struct address_space *mapping, struct page *page)
461 {
462 if (__remove_mapping(mapping, page)) {
463 /*
464 * Unfreezing the refcount with 1 rather than 2 effectively
465 * drops the pagecache ref for us without requiring another
466 * atomic operation.
467 */
468 page_unfreeze_refs(page, 1);
469 return 1;
470 }
471 return 0;
472 }
473
474 /**
475 * putback_lru_page - put previously isolated page onto appropriate LRU list
476 * @page: page to be put back to appropriate lru list
477 *
478 * Add previously isolated @page to appropriate LRU list.
479 * Page may still be unevictable for other reasons.
480 *
481 * lru_lock must not be held, interrupts must be enabled.
482 */
483 #ifdef CONFIG_UNEVICTABLE_LRU
484 void putback_lru_page(struct page *page)
485 {
486 int lru;
487 int active = !!TestClearPageActive(page);
488 int was_unevictable = PageUnevictable(page);
489
490 VM_BUG_ON(PageLRU(page));
491
492 redo:
493 ClearPageUnevictable(page);
494
495 if (page_evictable(page, NULL)) {
496 /*
497 * For evictable pages, we can use the cache.
498 * In event of a race, worst case is we end up with an
499 * unevictable page on [in]active list.
500 * We know how to handle that.
501 */
502 lru = active + page_is_file_cache(page);
503 lru_cache_add_lru(page, lru);
504 } else {
505 /*
506 * Put unevictable pages directly on zone's unevictable
507 * list.
508 */
509 lru = LRU_UNEVICTABLE;
510 add_page_to_unevictable_list(page);
511 }
512 mem_cgroup_move_lists(page, lru);
513
514 /*
515 * page's status can change while we move it among lru. If an evictable
516 * page is on unevictable list, it never be freed. To avoid that,
517 * check after we added it to the list, again.
518 */
519 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
520 if (!isolate_lru_page(page)) {
521 put_page(page);
522 goto redo;
523 }
524 /* This means someone else dropped this page from LRU
525 * So, it will be freed or putback to LRU again. There is
526 * nothing to do here.
527 */
528 }
529
530 if (was_unevictable && lru != LRU_UNEVICTABLE)
531 count_vm_event(UNEVICTABLE_PGRESCUED);
532 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
533 count_vm_event(UNEVICTABLE_PGCULLED);
534
535 put_page(page); /* drop ref from isolate */
536 }
537
538 #else /* CONFIG_UNEVICTABLE_LRU */
539
540 void putback_lru_page(struct page *page)
541 {
542 int lru;
543 VM_BUG_ON(PageLRU(page));
544
545 lru = !!TestClearPageActive(page) + page_is_file_cache(page);
546 lru_cache_add_lru(page, lru);
547 mem_cgroup_move_lists(page, lru);
548 put_page(page);
549 }
550 #endif /* CONFIG_UNEVICTABLE_LRU */
551
552
553 /*
554 * shrink_page_list() returns the number of reclaimed pages
555 */
556 static unsigned long shrink_page_list(struct list_head *page_list,
557 struct scan_control *sc,
558 enum pageout_io sync_writeback)
559 {
560 LIST_HEAD(ret_pages);
561 struct pagevec freed_pvec;
562 int pgactivate = 0;
563 unsigned long nr_reclaimed = 0;
564
565 cond_resched();
566
567 pagevec_init(&freed_pvec, 1);
568 while (!list_empty(page_list)) {
569 struct address_space *mapping;
570 struct page *page;
571 int may_enter_fs;
572 int referenced;
573
574 cond_resched();
575
576 page = lru_to_page(page_list);
577 list_del(&page->lru);
578
579 if (!trylock_page(page))
580 goto keep;
581
582 VM_BUG_ON(PageActive(page));
583
584 sc->nr_scanned++;
585
586 if (unlikely(!page_evictable(page, NULL)))
587 goto cull_mlocked;
588
589 if (!sc->may_swap && page_mapped(page))
590 goto keep_locked;
591
592 /* Double the slab pressure for mapped and swapcache pages */
593 if (page_mapped(page) || PageSwapCache(page))
594 sc->nr_scanned++;
595
596 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
597 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
598
599 if (PageWriteback(page)) {
600 /*
601 * Synchronous reclaim is performed in two passes,
602 * first an asynchronous pass over the list to
603 * start parallel writeback, and a second synchronous
604 * pass to wait for the IO to complete. Wait here
605 * for any page for which writeback has already
606 * started.
607 */
608 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
609 wait_on_page_writeback(page);
610 else
611 goto keep_locked;
612 }
613
614 referenced = page_referenced(page, 1, sc->mem_cgroup);
615 /* In active use or really unfreeable? Activate it. */
616 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
617 referenced && page_mapping_inuse(page))
618 goto activate_locked;
619
620 #ifdef CONFIG_SWAP
621 /*
622 * Anonymous process memory has backing store?
623 * Try to allocate it some swap space here.
624 */
625 if (PageAnon(page) && !PageSwapCache(page)) {
626 switch (try_to_munlock(page)) {
627 case SWAP_FAIL: /* shouldn't happen */
628 case SWAP_AGAIN:
629 goto keep_locked;
630 case SWAP_MLOCK:
631 goto cull_mlocked;
632 case SWAP_SUCCESS:
633 ; /* fall thru'; add to swap cache */
634 }
635 if (!add_to_swap(page, GFP_ATOMIC))
636 goto activate_locked;
637 }
638 #endif /* CONFIG_SWAP */
639
640 mapping = page_mapping(page);
641
642 /*
643 * The page is mapped into the page tables of one or more
644 * processes. Try to unmap it here.
645 */
646 if (page_mapped(page) && mapping) {
647 switch (try_to_unmap(page, 0)) {
648 case SWAP_FAIL:
649 goto activate_locked;
650 case SWAP_AGAIN:
651 goto keep_locked;
652 case SWAP_MLOCK:
653 goto cull_mlocked;
654 case SWAP_SUCCESS:
655 ; /* try to free the page below */
656 }
657 }
658
659 if (PageDirty(page)) {
660 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
661 goto keep_locked;
662 if (!may_enter_fs)
663 goto keep_locked;
664 if (!sc->may_writepage)
665 goto keep_locked;
666
667 /* Page is dirty, try to write it out here */
668 switch (pageout(page, mapping, sync_writeback)) {
669 case PAGE_KEEP:
670 goto keep_locked;
671 case PAGE_ACTIVATE:
672 goto activate_locked;
673 case PAGE_SUCCESS:
674 if (PageWriteback(page) || PageDirty(page))
675 goto keep;
676 /*
677 * A synchronous write - probably a ramdisk. Go
678 * ahead and try to reclaim the page.
679 */
680 if (!trylock_page(page))
681 goto keep;
682 if (PageDirty(page) || PageWriteback(page))
683 goto keep_locked;
684 mapping = page_mapping(page);
685 case PAGE_CLEAN:
686 ; /* try to free the page below */
687 }
688 }
689
690 /*
691 * If the page has buffers, try to free the buffer mappings
692 * associated with this page. If we succeed we try to free
693 * the page as well.
694 *
695 * We do this even if the page is PageDirty().
696 * try_to_release_page() does not perform I/O, but it is
697 * possible for a page to have PageDirty set, but it is actually
698 * clean (all its buffers are clean). This happens if the
699 * buffers were written out directly, with submit_bh(). ext3
700 * will do this, as well as the blockdev mapping.
701 * try_to_release_page() will discover that cleanness and will
702 * drop the buffers and mark the page clean - it can be freed.
703 *
704 * Rarely, pages can have buffers and no ->mapping. These are
705 * the pages which were not successfully invalidated in
706 * truncate_complete_page(). We try to drop those buffers here
707 * and if that worked, and the page is no longer mapped into
708 * process address space (page_count == 1) it can be freed.
709 * Otherwise, leave the page on the LRU so it is swappable.
710 */
711 if (PagePrivate(page)) {
712 if (!try_to_release_page(page, sc->gfp_mask))
713 goto activate_locked;
714 if (!mapping && page_count(page) == 1) {
715 unlock_page(page);
716 if (put_page_testzero(page))
717 goto free_it;
718 else {
719 /*
720 * rare race with speculative reference.
721 * the speculative reference will free
722 * this page shortly, so we may
723 * increment nr_reclaimed here (and
724 * leave it off the LRU).
725 */
726 nr_reclaimed++;
727 continue;
728 }
729 }
730 }
731
732 if (!mapping || !__remove_mapping(mapping, page))
733 goto keep_locked;
734
735 /*
736 * At this point, we have no other references and there is
737 * no way to pick any more up (removed from LRU, removed
738 * from pagecache). Can use non-atomic bitops now (and
739 * we obviously don't have to worry about waking up a process
740 * waiting on the page lock, because there are no references.
741 */
742 __clear_page_locked(page);
743 free_it:
744 nr_reclaimed++;
745 if (!pagevec_add(&freed_pvec, page)) {
746 __pagevec_free(&freed_pvec);
747 pagevec_reinit(&freed_pvec);
748 }
749 continue;
750
751 cull_mlocked:
752 unlock_page(page);
753 putback_lru_page(page);
754 continue;
755
756 activate_locked:
757 /* Not a candidate for swapping, so reclaim swap space. */
758 if (PageSwapCache(page) && vm_swap_full())
759 remove_exclusive_swap_page_ref(page);
760 VM_BUG_ON(PageActive(page));
761 SetPageActive(page);
762 pgactivate++;
763 keep_locked:
764 unlock_page(page);
765 keep:
766 list_add(&page->lru, &ret_pages);
767 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
768 }
769 list_splice(&ret_pages, page_list);
770 if (pagevec_count(&freed_pvec))
771 __pagevec_free(&freed_pvec);
772 count_vm_events(PGACTIVATE, pgactivate);
773 return nr_reclaimed;
774 }
775
776 /* LRU Isolation modes. */
777 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
778 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
779 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
780
781 /*
782 * Attempt to remove the specified page from its LRU. Only take this page
783 * if it is of the appropriate PageActive status. Pages which are being
784 * freed elsewhere are also ignored.
785 *
786 * page: page to consider
787 * mode: one of the LRU isolation modes defined above
788 *
789 * returns 0 on success, -ve errno on failure.
790 */
791 int __isolate_lru_page(struct page *page, int mode, int file)
792 {
793 int ret = -EINVAL;
794
795 /* Only take pages on the LRU. */
796 if (!PageLRU(page))
797 return ret;
798
799 /*
800 * When checking the active state, we need to be sure we are
801 * dealing with comparible boolean values. Take the logical not
802 * of each.
803 */
804 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
805 return ret;
806
807 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
808 return ret;
809
810 /*
811 * When this function is being called for lumpy reclaim, we
812 * initially look into all LRU pages, active, inactive and
813 * unevictable; only give shrink_page_list evictable pages.
814 */
815 if (PageUnevictable(page))
816 return ret;
817
818 ret = -EBUSY;
819 if (likely(get_page_unless_zero(page))) {
820 /*
821 * Be careful not to clear PageLRU until after we're
822 * sure the page is not being freed elsewhere -- the
823 * page release code relies on it.
824 */
825 ClearPageLRU(page);
826 ret = 0;
827 }
828
829 return ret;
830 }
831
832 /*
833 * zone->lru_lock is heavily contended. Some of the functions that
834 * shrink the lists perform better by taking out a batch of pages
835 * and working on them outside the LRU lock.
836 *
837 * For pagecache intensive workloads, this function is the hottest
838 * spot in the kernel (apart from copy_*_user functions).
839 *
840 * Appropriate locks must be held before calling this function.
841 *
842 * @nr_to_scan: The number of pages to look through on the list.
843 * @src: The LRU list to pull pages off.
844 * @dst: The temp list to put pages on to.
845 * @scanned: The number of pages that were scanned.
846 * @order: The caller's attempted allocation order
847 * @mode: One of the LRU isolation modes
848 * @file: True [1] if isolating file [!anon] pages
849 *
850 * returns how many pages were moved onto *@dst.
851 */
852 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
853 struct list_head *src, struct list_head *dst,
854 unsigned long *scanned, int order, int mode, int file)
855 {
856 unsigned long nr_taken = 0;
857 unsigned long scan;
858
859 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
860 struct page *page;
861 unsigned long pfn;
862 unsigned long end_pfn;
863 unsigned long page_pfn;
864 int zone_id;
865
866 page = lru_to_page(src);
867 prefetchw_prev_lru_page(page, src, flags);
868
869 VM_BUG_ON(!PageLRU(page));
870
871 switch (__isolate_lru_page(page, mode, file)) {
872 case 0:
873 list_move(&page->lru, dst);
874 nr_taken++;
875 break;
876
877 case -EBUSY:
878 /* else it is being freed elsewhere */
879 list_move(&page->lru, src);
880 continue;
881
882 default:
883 BUG();
884 }
885
886 if (!order)
887 continue;
888
889 /*
890 * Attempt to take all pages in the order aligned region
891 * surrounding the tag page. Only take those pages of
892 * the same active state as that tag page. We may safely
893 * round the target page pfn down to the requested order
894 * as the mem_map is guarenteed valid out to MAX_ORDER,
895 * where that page is in a different zone we will detect
896 * it from its zone id and abort this block scan.
897 */
898 zone_id = page_zone_id(page);
899 page_pfn = page_to_pfn(page);
900 pfn = page_pfn & ~((1 << order) - 1);
901 end_pfn = pfn + (1 << order);
902 for (; pfn < end_pfn; pfn++) {
903 struct page *cursor_page;
904
905 /* The target page is in the block, ignore it. */
906 if (unlikely(pfn == page_pfn))
907 continue;
908
909 /* Avoid holes within the zone. */
910 if (unlikely(!pfn_valid_within(pfn)))
911 break;
912
913 cursor_page = pfn_to_page(pfn);
914
915 /* Check that we have not crossed a zone boundary. */
916 if (unlikely(page_zone_id(cursor_page) != zone_id))
917 continue;
918 switch (__isolate_lru_page(cursor_page, mode, file)) {
919 case 0:
920 list_move(&cursor_page->lru, dst);
921 nr_taken++;
922 scan++;
923 break;
924
925 case -EBUSY:
926 /* else it is being freed elsewhere */
927 list_move(&cursor_page->lru, src);
928 default:
929 break; /* ! on LRU or wrong list */
930 }
931 }
932 }
933
934 *scanned = scan;
935 return nr_taken;
936 }
937
938 static unsigned long isolate_pages_global(unsigned long nr,
939 struct list_head *dst,
940 unsigned long *scanned, int order,
941 int mode, struct zone *z,
942 struct mem_cgroup *mem_cont,
943 int active, int file)
944 {
945 int lru = LRU_BASE;
946 if (active)
947 lru += LRU_ACTIVE;
948 if (file)
949 lru += LRU_FILE;
950 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
951 mode, !!file);
952 }
953
954 /*
955 * clear_active_flags() is a helper for shrink_active_list(), clearing
956 * any active bits from the pages in the list.
957 */
958 static unsigned long clear_active_flags(struct list_head *page_list,
959 unsigned int *count)
960 {
961 int nr_active = 0;
962 int lru;
963 struct page *page;
964
965 list_for_each_entry(page, page_list, lru) {
966 lru = page_is_file_cache(page);
967 if (PageActive(page)) {
968 lru += LRU_ACTIVE;
969 ClearPageActive(page);
970 nr_active++;
971 }
972 count[lru]++;
973 }
974
975 return nr_active;
976 }
977
978 /**
979 * isolate_lru_page - tries to isolate a page from its LRU list
980 * @page: page to isolate from its LRU list
981 *
982 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
983 * vmstat statistic corresponding to whatever LRU list the page was on.
984 *
985 * Returns 0 if the page was removed from an LRU list.
986 * Returns -EBUSY if the page was not on an LRU list.
987 *
988 * The returned page will have PageLRU() cleared. If it was found on
989 * the active list, it will have PageActive set. If it was found on
990 * the unevictable list, it will have the PageUnevictable bit set. That flag
991 * may need to be cleared by the caller before letting the page go.
992 *
993 * The vmstat statistic corresponding to the list on which the page was
994 * found will be decremented.
995 *
996 * Restrictions:
997 * (1) Must be called with an elevated refcount on the page. This is a
998 * fundamentnal difference from isolate_lru_pages (which is called
999 * without a stable reference).
1000 * (2) the lru_lock must not be held.
1001 * (3) interrupts must be enabled.
1002 */
1003 int isolate_lru_page(struct page *page)
1004 {
1005 int ret = -EBUSY;
1006
1007 if (PageLRU(page)) {
1008 struct zone *zone = page_zone(page);
1009
1010 spin_lock_irq(&zone->lru_lock);
1011 if (PageLRU(page) && get_page_unless_zero(page)) {
1012 int lru = page_lru(page);
1013 ret = 0;
1014 ClearPageLRU(page);
1015
1016 del_page_from_lru_list(zone, page, lru);
1017 }
1018 spin_unlock_irq(&zone->lru_lock);
1019 }
1020 return ret;
1021 }
1022
1023 /*
1024 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1025 * of reclaimed pages
1026 */
1027 static unsigned long shrink_inactive_list(unsigned long max_scan,
1028 struct zone *zone, struct scan_control *sc,
1029 int priority, int file)
1030 {
1031 LIST_HEAD(page_list);
1032 struct pagevec pvec;
1033 unsigned long nr_scanned = 0;
1034 unsigned long nr_reclaimed = 0;
1035
1036 pagevec_init(&pvec, 1);
1037
1038 lru_add_drain();
1039 spin_lock_irq(&zone->lru_lock);
1040 do {
1041 struct page *page;
1042 unsigned long nr_taken;
1043 unsigned long nr_scan;
1044 unsigned long nr_freed;
1045 unsigned long nr_active;
1046 unsigned int count[NR_LRU_LISTS] = { 0, };
1047 int mode = ISOLATE_INACTIVE;
1048
1049 /*
1050 * If we need a large contiguous chunk of memory, or have
1051 * trouble getting a small set of contiguous pages, we
1052 * will reclaim both active and inactive pages.
1053 *
1054 * We use the same threshold as pageout congestion_wait below.
1055 */
1056 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1057 mode = ISOLATE_BOTH;
1058 else if (sc->order && priority < DEF_PRIORITY - 2)
1059 mode = ISOLATE_BOTH;
1060
1061 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1062 &page_list, &nr_scan, sc->order, mode,
1063 zone, sc->mem_cgroup, 0, file);
1064 nr_active = clear_active_flags(&page_list, count);
1065 __count_vm_events(PGDEACTIVATE, nr_active);
1066
1067 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1068 -count[LRU_ACTIVE_FILE]);
1069 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1070 -count[LRU_INACTIVE_FILE]);
1071 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1072 -count[LRU_ACTIVE_ANON]);
1073 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1074 -count[LRU_INACTIVE_ANON]);
1075
1076 if (scan_global_lru(sc)) {
1077 zone->pages_scanned += nr_scan;
1078 zone->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1079 zone->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1080 zone->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1081 zone->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1082 }
1083 spin_unlock_irq(&zone->lru_lock);
1084
1085 nr_scanned += nr_scan;
1086 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1087
1088 /*
1089 * If we are direct reclaiming for contiguous pages and we do
1090 * not reclaim everything in the list, try again and wait
1091 * for IO to complete. This will stall high-order allocations
1092 * but that should be acceptable to the caller
1093 */
1094 if (nr_freed < nr_taken && !current_is_kswapd() &&
1095 sc->order > PAGE_ALLOC_COSTLY_ORDER) {
1096 congestion_wait(WRITE, HZ/10);
1097
1098 /*
1099 * The attempt at page out may have made some
1100 * of the pages active, mark them inactive again.
1101 */
1102 nr_active = clear_active_flags(&page_list, count);
1103 count_vm_events(PGDEACTIVATE, nr_active);
1104
1105 nr_freed += shrink_page_list(&page_list, sc,
1106 PAGEOUT_IO_SYNC);
1107 }
1108
1109 nr_reclaimed += nr_freed;
1110 local_irq_disable();
1111 if (current_is_kswapd()) {
1112 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
1113 __count_vm_events(KSWAPD_STEAL, nr_freed);
1114 } else if (scan_global_lru(sc))
1115 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1116
1117 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1118
1119 if (nr_taken == 0)
1120 goto done;
1121
1122 spin_lock(&zone->lru_lock);
1123 /*
1124 * Put back any unfreeable pages.
1125 */
1126 while (!list_empty(&page_list)) {
1127 int lru;
1128 page = lru_to_page(&page_list);
1129 VM_BUG_ON(PageLRU(page));
1130 list_del(&page->lru);
1131 if (unlikely(!page_evictable(page, NULL))) {
1132 spin_unlock_irq(&zone->lru_lock);
1133 putback_lru_page(page);
1134 spin_lock_irq(&zone->lru_lock);
1135 continue;
1136 }
1137 SetPageLRU(page);
1138 lru = page_lru(page);
1139 add_page_to_lru_list(zone, page, lru);
1140 mem_cgroup_move_lists(page, lru);
1141 if (PageActive(page) && scan_global_lru(sc)) {
1142 int file = !!page_is_file_cache(page);
1143 zone->recent_rotated[file]++;
1144 }
1145 if (!pagevec_add(&pvec, page)) {
1146 spin_unlock_irq(&zone->lru_lock);
1147 __pagevec_release(&pvec);
1148 spin_lock_irq(&zone->lru_lock);
1149 }
1150 }
1151 } while (nr_scanned < max_scan);
1152 spin_unlock(&zone->lru_lock);
1153 done:
1154 local_irq_enable();
1155 pagevec_release(&pvec);
1156 return nr_reclaimed;
1157 }
1158
1159 /*
1160 * We are about to scan this zone at a certain priority level. If that priority
1161 * level is smaller (ie: more urgent) than the previous priority, then note
1162 * that priority level within the zone. This is done so that when the next
1163 * process comes in to scan this zone, it will immediately start out at this
1164 * priority level rather than having to build up its own scanning priority.
1165 * Here, this priority affects only the reclaim-mapped threshold.
1166 */
1167 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1168 {
1169 if (priority < zone->prev_priority)
1170 zone->prev_priority = priority;
1171 }
1172
1173 static inline int zone_is_near_oom(struct zone *zone)
1174 {
1175 return zone->pages_scanned >= (zone_lru_pages(zone) * 3);
1176 }
1177
1178 /*
1179 * This moves pages from the active list to the inactive list.
1180 *
1181 * We move them the other way if the page is referenced by one or more
1182 * processes, from rmap.
1183 *
1184 * If the pages are mostly unmapped, the processing is fast and it is
1185 * appropriate to hold zone->lru_lock across the whole operation. But if
1186 * the pages are mapped, the processing is slow (page_referenced()) so we
1187 * should drop zone->lru_lock around each page. It's impossible to balance
1188 * this, so instead we remove the pages from the LRU while processing them.
1189 * It is safe to rely on PG_active against the non-LRU pages in here because
1190 * nobody will play with that bit on a non-LRU page.
1191 *
1192 * The downside is that we have to touch page->_count against each page.
1193 * But we had to alter page->flags anyway.
1194 */
1195
1196
1197 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1198 struct scan_control *sc, int priority, int file)
1199 {
1200 unsigned long pgmoved;
1201 int pgdeactivate = 0;
1202 unsigned long pgscanned;
1203 LIST_HEAD(l_hold); /* The pages which were snipped off */
1204 LIST_HEAD(l_inactive);
1205 struct page *page;
1206 struct pagevec pvec;
1207 enum lru_list lru;
1208
1209 lru_add_drain();
1210 spin_lock_irq(&zone->lru_lock);
1211 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1212 ISOLATE_ACTIVE, zone,
1213 sc->mem_cgroup, 1, file);
1214 /*
1215 * zone->pages_scanned is used for detect zone's oom
1216 * mem_cgroup remembers nr_scan by itself.
1217 */
1218 if (scan_global_lru(sc)) {
1219 zone->pages_scanned += pgscanned;
1220 zone->recent_scanned[!!file] += pgmoved;
1221 }
1222
1223 if (file)
1224 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1225 else
1226 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
1227 spin_unlock_irq(&zone->lru_lock);
1228
1229 pgmoved = 0;
1230 while (!list_empty(&l_hold)) {
1231 cond_resched();
1232 page = lru_to_page(&l_hold);
1233 list_del(&page->lru);
1234
1235 if (unlikely(!page_evictable(page, NULL))) {
1236 putback_lru_page(page);
1237 continue;
1238 }
1239
1240 /* page_referenced clears PageReferenced */
1241 if (page_mapping_inuse(page) &&
1242 page_referenced(page, 0, sc->mem_cgroup))
1243 pgmoved++;
1244
1245 list_add(&page->lru, &l_inactive);
1246 }
1247
1248 /*
1249 * Count referenced pages from currently used mappings as
1250 * rotated, even though they are moved to the inactive list.
1251 * This helps balance scan pressure between file and anonymous
1252 * pages in get_scan_ratio.
1253 */
1254 zone->recent_rotated[!!file] += pgmoved;
1255
1256 /*
1257 * Move the pages to the [file or anon] inactive list.
1258 */
1259 pagevec_init(&pvec, 1);
1260
1261 pgmoved = 0;
1262 lru = LRU_BASE + file * LRU_FILE;
1263 spin_lock_irq(&zone->lru_lock);
1264 while (!list_empty(&l_inactive)) {
1265 page = lru_to_page(&l_inactive);
1266 prefetchw_prev_lru_page(page, &l_inactive, flags);
1267 VM_BUG_ON(PageLRU(page));
1268 SetPageLRU(page);
1269 VM_BUG_ON(!PageActive(page));
1270 ClearPageActive(page);
1271
1272 list_move(&page->lru, &zone->lru[lru].list);
1273 mem_cgroup_move_lists(page, lru);
1274 pgmoved++;
1275 if (!pagevec_add(&pvec, page)) {
1276 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1277 spin_unlock_irq(&zone->lru_lock);
1278 pgdeactivate += pgmoved;
1279 pgmoved = 0;
1280 if (buffer_heads_over_limit)
1281 pagevec_strip(&pvec);
1282 __pagevec_release(&pvec);
1283 spin_lock_irq(&zone->lru_lock);
1284 }
1285 }
1286 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1287 pgdeactivate += pgmoved;
1288 if (buffer_heads_over_limit) {
1289 spin_unlock_irq(&zone->lru_lock);
1290 pagevec_strip(&pvec);
1291 spin_lock_irq(&zone->lru_lock);
1292 }
1293 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1294 __count_vm_events(PGDEACTIVATE, pgdeactivate);
1295 spin_unlock_irq(&zone->lru_lock);
1296 if (vm_swap_full())
1297 pagevec_swap_free(&pvec);
1298
1299 pagevec_release(&pvec);
1300 }
1301
1302 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1303 struct zone *zone, struct scan_control *sc, int priority)
1304 {
1305 int file = is_file_lru(lru);
1306
1307 if (lru == LRU_ACTIVE_FILE) {
1308 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1309 return 0;
1310 }
1311
1312 if (lru == LRU_ACTIVE_ANON &&
1313 (!scan_global_lru(sc) || inactive_anon_is_low(zone))) {
1314 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1315 return 0;
1316 }
1317 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1318 }
1319
1320 /*
1321 * Determine how aggressively the anon and file LRU lists should be
1322 * scanned. The relative value of each set of LRU lists is determined
1323 * by looking at the fraction of the pages scanned we did rotate back
1324 * onto the active list instead of evict.
1325 *
1326 * percent[0] specifies how much pressure to put on ram/swap backed
1327 * memory, while percent[1] determines pressure on the file LRUs.
1328 */
1329 static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1330 unsigned long *percent)
1331 {
1332 unsigned long anon, file, free;
1333 unsigned long anon_prio, file_prio;
1334 unsigned long ap, fp;
1335
1336 anon = zone_page_state(zone, NR_ACTIVE_ANON) +
1337 zone_page_state(zone, NR_INACTIVE_ANON);
1338 file = zone_page_state(zone, NR_ACTIVE_FILE) +
1339 zone_page_state(zone, NR_INACTIVE_FILE);
1340 free = zone_page_state(zone, NR_FREE_PAGES);
1341
1342 /* If we have no swap space, do not bother scanning anon pages. */
1343 if (nr_swap_pages <= 0) {
1344 percent[0] = 0;
1345 percent[1] = 100;
1346 return;
1347 }
1348
1349 /* If we have very few page cache pages, force-scan anon pages. */
1350 if (unlikely(file + free <= zone->pages_high)) {
1351 percent[0] = 100;
1352 percent[1] = 0;
1353 return;
1354 }
1355
1356 /*
1357 * OK, so we have swap space and a fair amount of page cache
1358 * pages. We use the recently rotated / recently scanned
1359 * ratios to determine how valuable each cache is.
1360 *
1361 * Because workloads change over time (and to avoid overflow)
1362 * we keep these statistics as a floating average, which ends
1363 * up weighing recent references more than old ones.
1364 *
1365 * anon in [0], file in [1]
1366 */
1367 if (unlikely(zone->recent_scanned[0] > anon / 4)) {
1368 spin_lock_irq(&zone->lru_lock);
1369 zone->recent_scanned[0] /= 2;
1370 zone->recent_rotated[0] /= 2;
1371 spin_unlock_irq(&zone->lru_lock);
1372 }
1373
1374 if (unlikely(zone->recent_scanned[1] > file / 4)) {
1375 spin_lock_irq(&zone->lru_lock);
1376 zone->recent_scanned[1] /= 2;
1377 zone->recent_rotated[1] /= 2;
1378 spin_unlock_irq(&zone->lru_lock);
1379 }
1380
1381 /*
1382 * With swappiness at 100, anonymous and file have the same priority.
1383 * This scanning priority is essentially the inverse of IO cost.
1384 */
1385 anon_prio = sc->swappiness;
1386 file_prio = 200 - sc->swappiness;
1387
1388 /*
1389 * anon recent_rotated[0]
1390 * %anon = 100 * ----------- / ----------------- * IO cost
1391 * anon + file rotate_sum
1392 */
1393 ap = (anon_prio + 1) * (zone->recent_scanned[0] + 1);
1394 ap /= zone->recent_rotated[0] + 1;
1395
1396 fp = (file_prio + 1) * (zone->recent_scanned[1] + 1);
1397 fp /= zone->recent_rotated[1] + 1;
1398
1399 /* Normalize to percentages */
1400 percent[0] = 100 * ap / (ap + fp + 1);
1401 percent[1] = 100 - percent[0];
1402 }
1403
1404
1405 /*
1406 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1407 */
1408 static unsigned long shrink_zone(int priority, struct zone *zone,
1409 struct scan_control *sc)
1410 {
1411 unsigned long nr[NR_LRU_LISTS];
1412 unsigned long nr_to_scan;
1413 unsigned long nr_reclaimed = 0;
1414 unsigned long percent[2]; /* anon @ 0; file @ 1 */
1415 enum lru_list l;
1416
1417 get_scan_ratio(zone, sc, percent);
1418
1419 for_each_evictable_lru(l) {
1420 if (scan_global_lru(sc)) {
1421 int file = is_file_lru(l);
1422 int scan;
1423
1424 scan = zone_page_state(zone, NR_LRU_BASE + l);
1425 if (priority) {
1426 scan >>= priority;
1427 scan = (scan * percent[file]) / 100;
1428 }
1429 zone->lru[l].nr_scan += scan;
1430 nr[l] = zone->lru[l].nr_scan;
1431 if (nr[l] >= sc->swap_cluster_max)
1432 zone->lru[l].nr_scan = 0;
1433 else
1434 nr[l] = 0;
1435 } else {
1436 /*
1437 * This reclaim occurs not because zone memory shortage
1438 * but because memory controller hits its limit.
1439 * Don't modify zone reclaim related data.
1440 */
1441 nr[l] = mem_cgroup_calc_reclaim(sc->mem_cgroup, zone,
1442 priority, l);
1443 }
1444 }
1445
1446 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1447 nr[LRU_INACTIVE_FILE]) {
1448 for_each_evictable_lru(l) {
1449 if (nr[l]) {
1450 nr_to_scan = min(nr[l],
1451 (unsigned long)sc->swap_cluster_max);
1452 nr[l] -= nr_to_scan;
1453
1454 nr_reclaimed += shrink_list(l, nr_to_scan,
1455 zone, sc, priority);
1456 }
1457 }
1458 }
1459
1460 /*
1461 * Even if we did not try to evict anon pages at all, we want to
1462 * rebalance the anon lru active/inactive ratio.
1463 */
1464 if (!scan_global_lru(sc) || inactive_anon_is_low(zone))
1465 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1466 else if (!scan_global_lru(sc))
1467 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1468
1469 throttle_vm_writeout(sc->gfp_mask);
1470 return nr_reclaimed;
1471 }
1472
1473 /*
1474 * This is the direct reclaim path, for page-allocating processes. We only
1475 * try to reclaim pages from zones which will satisfy the caller's allocation
1476 * request.
1477 *
1478 * We reclaim from a zone even if that zone is over pages_high. Because:
1479 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1480 * allocation or
1481 * b) The zones may be over pages_high but they must go *over* pages_high to
1482 * satisfy the `incremental min' zone defense algorithm.
1483 *
1484 * Returns the number of reclaimed pages.
1485 *
1486 * If a zone is deemed to be full of pinned pages then just give it a light
1487 * scan then give up on it.
1488 */
1489 static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
1490 struct scan_control *sc)
1491 {
1492 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1493 unsigned long nr_reclaimed = 0;
1494 struct zoneref *z;
1495 struct zone *zone;
1496
1497 sc->all_unreclaimable = 1;
1498 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1499 if (!populated_zone(zone))
1500 continue;
1501 /*
1502 * Take care memory controller reclaiming has small influence
1503 * to global LRU.
1504 */
1505 if (scan_global_lru(sc)) {
1506 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1507 continue;
1508 note_zone_scanning_priority(zone, priority);
1509
1510 if (zone_is_all_unreclaimable(zone) &&
1511 priority != DEF_PRIORITY)
1512 continue; /* Let kswapd poll it */
1513 sc->all_unreclaimable = 0;
1514 } else {
1515 /*
1516 * Ignore cpuset limitation here. We just want to reduce
1517 * # of used pages by us regardless of memory shortage.
1518 */
1519 sc->all_unreclaimable = 0;
1520 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1521 priority);
1522 }
1523
1524 nr_reclaimed += shrink_zone(priority, zone, sc);
1525 }
1526
1527 return nr_reclaimed;
1528 }
1529
1530 /*
1531 * This is the main entry point to direct page reclaim.
1532 *
1533 * If a full scan of the inactive list fails to free enough memory then we
1534 * are "out of memory" and something needs to be killed.
1535 *
1536 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1537 * high - the zone may be full of dirty or under-writeback pages, which this
1538 * caller can't do much about. We kick pdflush and take explicit naps in the
1539 * hope that some of these pages can be written. But if the allocating task
1540 * holds filesystem locks which prevent writeout this might not work, and the
1541 * allocation attempt will fail.
1542 *
1543 * returns: 0, if no pages reclaimed
1544 * else, the number of pages reclaimed
1545 */
1546 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1547 struct scan_control *sc)
1548 {
1549 int priority;
1550 unsigned long ret = 0;
1551 unsigned long total_scanned = 0;
1552 unsigned long nr_reclaimed = 0;
1553 struct reclaim_state *reclaim_state = current->reclaim_state;
1554 unsigned long lru_pages = 0;
1555 struct zoneref *z;
1556 struct zone *zone;
1557 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1558
1559 delayacct_freepages_start();
1560
1561 if (scan_global_lru(sc))
1562 count_vm_event(ALLOCSTALL);
1563 /*
1564 * mem_cgroup will not do shrink_slab.
1565 */
1566 if (scan_global_lru(sc)) {
1567 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1568
1569 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1570 continue;
1571
1572 lru_pages += zone_lru_pages(zone);
1573 }
1574 }
1575
1576 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1577 sc->nr_scanned = 0;
1578 if (!priority)
1579 disable_swap_token();
1580 nr_reclaimed += shrink_zones(priority, zonelist, sc);
1581 /*
1582 * Don't shrink slabs when reclaiming memory from
1583 * over limit cgroups
1584 */
1585 if (scan_global_lru(sc)) {
1586 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1587 if (reclaim_state) {
1588 nr_reclaimed += reclaim_state->reclaimed_slab;
1589 reclaim_state->reclaimed_slab = 0;
1590 }
1591 }
1592 total_scanned += sc->nr_scanned;
1593 if (nr_reclaimed >= sc->swap_cluster_max) {
1594 ret = nr_reclaimed;
1595 goto out;
1596 }
1597
1598 /*
1599 * Try to write back as many pages as we just scanned. This
1600 * tends to cause slow streaming writers to write data to the
1601 * disk smoothly, at the dirtying rate, which is nice. But
1602 * that's undesirable in laptop mode, where we *want* lumpy
1603 * writeout. So in laptop mode, write out the whole world.
1604 */
1605 if (total_scanned > sc->swap_cluster_max +
1606 sc->swap_cluster_max / 2) {
1607 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1608 sc->may_writepage = 1;
1609 }
1610
1611 /* Take a nap, wait for some writeback to complete */
1612 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1613 congestion_wait(WRITE, HZ/10);
1614 }
1615 /* top priority shrink_zones still had more to do? don't OOM, then */
1616 if (!sc->all_unreclaimable && scan_global_lru(sc))
1617 ret = nr_reclaimed;
1618 out:
1619 /*
1620 * Now that we've scanned all the zones at this priority level, note
1621 * that level within the zone so that the next thread which performs
1622 * scanning of this zone will immediately start out at this priority
1623 * level. This affects only the decision whether or not to bring
1624 * mapped pages onto the inactive list.
1625 */
1626 if (priority < 0)
1627 priority = 0;
1628
1629 if (scan_global_lru(sc)) {
1630 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1631
1632 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1633 continue;
1634
1635 zone->prev_priority = priority;
1636 }
1637 } else
1638 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1639
1640 delayacct_freepages_end();
1641
1642 return ret;
1643 }
1644
1645 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1646 gfp_t gfp_mask)
1647 {
1648 struct scan_control sc = {
1649 .gfp_mask = gfp_mask,
1650 .may_writepage = !laptop_mode,
1651 .swap_cluster_max = SWAP_CLUSTER_MAX,
1652 .may_swap = 1,
1653 .swappiness = vm_swappiness,
1654 .order = order,
1655 .mem_cgroup = NULL,
1656 .isolate_pages = isolate_pages_global,
1657 };
1658
1659 return do_try_to_free_pages(zonelist, &sc);
1660 }
1661
1662 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1663
1664 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1665 gfp_t gfp_mask)
1666 {
1667 struct scan_control sc = {
1668 .may_writepage = !laptop_mode,
1669 .may_swap = 1,
1670 .swap_cluster_max = SWAP_CLUSTER_MAX,
1671 .swappiness = vm_swappiness,
1672 .order = 0,
1673 .mem_cgroup = mem_cont,
1674 .isolate_pages = mem_cgroup_isolate_pages,
1675 };
1676 struct zonelist *zonelist;
1677
1678 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1679 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1680 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1681 return do_try_to_free_pages(zonelist, &sc);
1682 }
1683 #endif
1684
1685 /*
1686 * For kswapd, balance_pgdat() will work across all this node's zones until
1687 * they are all at pages_high.
1688 *
1689 * Returns the number of pages which were actually freed.
1690 *
1691 * There is special handling here for zones which are full of pinned pages.
1692 * This can happen if the pages are all mlocked, or if they are all used by
1693 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1694 * What we do is to detect the case where all pages in the zone have been
1695 * scanned twice and there has been zero successful reclaim. Mark the zone as
1696 * dead and from now on, only perform a short scan. Basically we're polling
1697 * the zone for when the problem goes away.
1698 *
1699 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1700 * zones which have free_pages > pages_high, but once a zone is found to have
1701 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1702 * of the number of free pages in the lower zones. This interoperates with
1703 * the page allocator fallback scheme to ensure that aging of pages is balanced
1704 * across the zones.
1705 */
1706 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1707 {
1708 int all_zones_ok;
1709 int priority;
1710 int i;
1711 unsigned long total_scanned;
1712 unsigned long nr_reclaimed;
1713 struct reclaim_state *reclaim_state = current->reclaim_state;
1714 struct scan_control sc = {
1715 .gfp_mask = GFP_KERNEL,
1716 .may_swap = 1,
1717 .swap_cluster_max = SWAP_CLUSTER_MAX,
1718 .swappiness = vm_swappiness,
1719 .order = order,
1720 .mem_cgroup = NULL,
1721 .isolate_pages = isolate_pages_global,
1722 };
1723 /*
1724 * temp_priority is used to remember the scanning priority at which
1725 * this zone was successfully refilled to free_pages == pages_high.
1726 */
1727 int temp_priority[MAX_NR_ZONES];
1728
1729 loop_again:
1730 total_scanned = 0;
1731 nr_reclaimed = 0;
1732 sc.may_writepage = !laptop_mode;
1733 count_vm_event(PAGEOUTRUN);
1734
1735 for (i = 0; i < pgdat->nr_zones; i++)
1736 temp_priority[i] = DEF_PRIORITY;
1737
1738 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1739 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1740 unsigned long lru_pages = 0;
1741
1742 /* The swap token gets in the way of swapout... */
1743 if (!priority)
1744 disable_swap_token();
1745
1746 all_zones_ok = 1;
1747
1748 /*
1749 * Scan in the highmem->dma direction for the highest
1750 * zone which needs scanning
1751 */
1752 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1753 struct zone *zone = pgdat->node_zones + i;
1754
1755 if (!populated_zone(zone))
1756 continue;
1757
1758 if (zone_is_all_unreclaimable(zone) &&
1759 priority != DEF_PRIORITY)
1760 continue;
1761
1762 /*
1763 * Do some background aging of the anon list, to give
1764 * pages a chance to be referenced before reclaiming.
1765 */
1766 if (inactive_anon_is_low(zone))
1767 shrink_active_list(SWAP_CLUSTER_MAX, zone,
1768 &sc, priority, 0);
1769
1770 if (!zone_watermark_ok(zone, order, zone->pages_high,
1771 0, 0)) {
1772 end_zone = i;
1773 break;
1774 }
1775 }
1776 if (i < 0)
1777 goto out;
1778
1779 for (i = 0; i <= end_zone; i++) {
1780 struct zone *zone = pgdat->node_zones + i;
1781
1782 lru_pages += zone_lru_pages(zone);
1783 }
1784
1785 /*
1786 * Now scan the zone in the dma->highmem direction, stopping
1787 * at the last zone which needs scanning.
1788 *
1789 * We do this because the page allocator works in the opposite
1790 * direction. This prevents the page allocator from allocating
1791 * pages behind kswapd's direction of progress, which would
1792 * cause too much scanning of the lower zones.
1793 */
1794 for (i = 0; i <= end_zone; i++) {
1795 struct zone *zone = pgdat->node_zones + i;
1796 int nr_slab;
1797
1798 if (!populated_zone(zone))
1799 continue;
1800
1801 if (zone_is_all_unreclaimable(zone) &&
1802 priority != DEF_PRIORITY)
1803 continue;
1804
1805 if (!zone_watermark_ok(zone, order, zone->pages_high,
1806 end_zone, 0))
1807 all_zones_ok = 0;
1808 temp_priority[i] = priority;
1809 sc.nr_scanned = 0;
1810 note_zone_scanning_priority(zone, priority);
1811 /*
1812 * We put equal pressure on every zone, unless one
1813 * zone has way too many pages free already.
1814 */
1815 if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
1816 end_zone, 0))
1817 nr_reclaimed += shrink_zone(priority, zone, &sc);
1818 reclaim_state->reclaimed_slab = 0;
1819 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1820 lru_pages);
1821 nr_reclaimed += reclaim_state->reclaimed_slab;
1822 total_scanned += sc.nr_scanned;
1823 if (zone_is_all_unreclaimable(zone))
1824 continue;
1825 if (nr_slab == 0 && zone->pages_scanned >=
1826 (zone_lru_pages(zone) * 6))
1827 zone_set_flag(zone,
1828 ZONE_ALL_UNRECLAIMABLE);
1829 /*
1830 * If we've done a decent amount of scanning and
1831 * the reclaim ratio is low, start doing writepage
1832 * even in laptop mode
1833 */
1834 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1835 total_scanned > nr_reclaimed + nr_reclaimed / 2)
1836 sc.may_writepage = 1;
1837 }
1838 if (all_zones_ok)
1839 break; /* kswapd: all done */
1840 /*
1841 * OK, kswapd is getting into trouble. Take a nap, then take
1842 * another pass across the zones.
1843 */
1844 if (total_scanned && priority < DEF_PRIORITY - 2)
1845 congestion_wait(WRITE, HZ/10);
1846
1847 /*
1848 * We do this so kswapd doesn't build up large priorities for
1849 * example when it is freeing in parallel with allocators. It
1850 * matches the direct reclaim path behaviour in terms of impact
1851 * on zone->*_priority.
1852 */
1853 if (nr_reclaimed >= SWAP_CLUSTER_MAX)
1854 break;
1855 }
1856 out:
1857 /*
1858 * Note within each zone the priority level at which this zone was
1859 * brought into a happy state. So that the next thread which scans this
1860 * zone will start out at that priority level.
1861 */
1862 for (i = 0; i < pgdat->nr_zones; i++) {
1863 struct zone *zone = pgdat->node_zones + i;
1864
1865 zone->prev_priority = temp_priority[i];
1866 }
1867 if (!all_zones_ok) {
1868 cond_resched();
1869
1870 try_to_freeze();
1871
1872 goto loop_again;
1873 }
1874
1875 return nr_reclaimed;
1876 }
1877
1878 /*
1879 * The background pageout daemon, started as a kernel thread
1880 * from the init process.
1881 *
1882 * This basically trickles out pages so that we have _some_
1883 * free memory available even if there is no other activity
1884 * that frees anything up. This is needed for things like routing
1885 * etc, where we otherwise might have all activity going on in
1886 * asynchronous contexts that cannot page things out.
1887 *
1888 * If there are applications that are active memory-allocators
1889 * (most normal use), this basically shouldn't matter.
1890 */
1891 static int kswapd(void *p)
1892 {
1893 unsigned long order;
1894 pg_data_t *pgdat = (pg_data_t*)p;
1895 struct task_struct *tsk = current;
1896 DEFINE_WAIT(wait);
1897 struct reclaim_state reclaim_state = {
1898 .reclaimed_slab = 0,
1899 };
1900 node_to_cpumask_ptr(cpumask, pgdat->node_id);
1901
1902 if (!cpus_empty(*cpumask))
1903 set_cpus_allowed_ptr(tsk, cpumask);
1904 current->reclaim_state = &reclaim_state;
1905
1906 /*
1907 * Tell the memory management that we're a "memory allocator",
1908 * and that if we need more memory we should get access to it
1909 * regardless (see "__alloc_pages()"). "kswapd" should
1910 * never get caught in the normal page freeing logic.
1911 *
1912 * (Kswapd normally doesn't need memory anyway, but sometimes
1913 * you need a small amount of memory in order to be able to
1914 * page out something else, and this flag essentially protects
1915 * us from recursively trying to free more memory as we're
1916 * trying to free the first piece of memory in the first place).
1917 */
1918 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1919 set_freezable();
1920
1921 order = 0;
1922 for ( ; ; ) {
1923 unsigned long new_order;
1924
1925 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1926 new_order = pgdat->kswapd_max_order;
1927 pgdat->kswapd_max_order = 0;
1928 if (order < new_order) {
1929 /*
1930 * Don't sleep if someone wants a larger 'order'
1931 * allocation
1932 */
1933 order = new_order;
1934 } else {
1935 if (!freezing(current))
1936 schedule();
1937
1938 order = pgdat->kswapd_max_order;
1939 }
1940 finish_wait(&pgdat->kswapd_wait, &wait);
1941
1942 if (!try_to_freeze()) {
1943 /* We can speed up thawing tasks if we don't call
1944 * balance_pgdat after returning from the refrigerator
1945 */
1946 balance_pgdat(pgdat, order);
1947 }
1948 }
1949 return 0;
1950 }
1951
1952 /*
1953 * A zone is low on free memory, so wake its kswapd task to service it.
1954 */
1955 void wakeup_kswapd(struct zone *zone, int order)
1956 {
1957 pg_data_t *pgdat;
1958
1959 if (!populated_zone(zone))
1960 return;
1961
1962 pgdat = zone->zone_pgdat;
1963 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
1964 return;
1965 if (pgdat->kswapd_max_order < order)
1966 pgdat->kswapd_max_order = order;
1967 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1968 return;
1969 if (!waitqueue_active(&pgdat->kswapd_wait))
1970 return;
1971 wake_up_interruptible(&pgdat->kswapd_wait);
1972 }
1973
1974 unsigned long global_lru_pages(void)
1975 {
1976 return global_page_state(NR_ACTIVE_ANON)
1977 + global_page_state(NR_ACTIVE_FILE)
1978 + global_page_state(NR_INACTIVE_ANON)
1979 + global_page_state(NR_INACTIVE_FILE);
1980 }
1981
1982 #ifdef CONFIG_PM
1983 /*
1984 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1985 * from LRU lists system-wide, for given pass and priority, and returns the
1986 * number of reclaimed pages
1987 *
1988 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1989 */
1990 static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
1991 int pass, struct scan_control *sc)
1992 {
1993 struct zone *zone;
1994 unsigned long nr_to_scan, ret = 0;
1995 enum lru_list l;
1996
1997 for_each_zone(zone) {
1998
1999 if (!populated_zone(zone))
2000 continue;
2001
2002 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2003 continue;
2004
2005 for_each_evictable_lru(l) {
2006 /* For pass = 0, we don't shrink the active list */
2007 if (pass == 0 &&
2008 (l == LRU_ACTIVE || l == LRU_ACTIVE_FILE))
2009 continue;
2010
2011 zone->lru[l].nr_scan +=
2012 (zone_page_state(zone, NR_LRU_BASE + l)
2013 >> prio) + 1;
2014 if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
2015 zone->lru[l].nr_scan = 0;
2016 nr_to_scan = min(nr_pages,
2017 zone_page_state(zone,
2018 NR_LRU_BASE + l));
2019 ret += shrink_list(l, nr_to_scan, zone,
2020 sc, prio);
2021 if (ret >= nr_pages)
2022 return ret;
2023 }
2024 }
2025 }
2026
2027 return ret;
2028 }
2029
2030 /*
2031 * Try to free `nr_pages' of memory, system-wide, and return the number of
2032 * freed pages.
2033 *
2034 * Rather than trying to age LRUs the aim is to preserve the overall
2035 * LRU order by reclaiming preferentially
2036 * inactive > active > active referenced > active mapped
2037 */
2038 unsigned long shrink_all_memory(unsigned long nr_pages)
2039 {
2040 unsigned long lru_pages, nr_slab;
2041 unsigned long ret = 0;
2042 int pass;
2043 struct reclaim_state reclaim_state;
2044 struct scan_control sc = {
2045 .gfp_mask = GFP_KERNEL,
2046 .may_swap = 0,
2047 .swap_cluster_max = nr_pages,
2048 .may_writepage = 1,
2049 .swappiness = vm_swappiness,
2050 .isolate_pages = isolate_pages_global,
2051 };
2052
2053 current->reclaim_state = &reclaim_state;
2054
2055 lru_pages = global_lru_pages();
2056 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2057 /* If slab caches are huge, it's better to hit them first */
2058 while (nr_slab >= lru_pages) {
2059 reclaim_state.reclaimed_slab = 0;
2060 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
2061 if (!reclaim_state.reclaimed_slab)
2062 break;
2063
2064 ret += reclaim_state.reclaimed_slab;
2065 if (ret >= nr_pages)
2066 goto out;
2067
2068 nr_slab -= reclaim_state.reclaimed_slab;
2069 }
2070
2071 /*
2072 * We try to shrink LRUs in 5 passes:
2073 * 0 = Reclaim from inactive_list only
2074 * 1 = Reclaim from active list but don't reclaim mapped
2075 * 2 = 2nd pass of type 1
2076 * 3 = Reclaim mapped (normal reclaim)
2077 * 4 = 2nd pass of type 3
2078 */
2079 for (pass = 0; pass < 5; pass++) {
2080 int prio;
2081
2082 /* Force reclaiming mapped pages in the passes #3 and #4 */
2083 if (pass > 2) {
2084 sc.may_swap = 1;
2085 sc.swappiness = 100;
2086 }
2087
2088 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2089 unsigned long nr_to_scan = nr_pages - ret;
2090
2091 sc.nr_scanned = 0;
2092 ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
2093 if (ret >= nr_pages)
2094 goto out;
2095
2096 reclaim_state.reclaimed_slab = 0;
2097 shrink_slab(sc.nr_scanned, sc.gfp_mask,
2098 global_lru_pages());
2099 ret += reclaim_state.reclaimed_slab;
2100 if (ret >= nr_pages)
2101 goto out;
2102
2103 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2104 congestion_wait(WRITE, HZ / 10);
2105 }
2106 }
2107
2108 /*
2109 * If ret = 0, we could not shrink LRUs, but there may be something
2110 * in slab caches
2111 */
2112 if (!ret) {
2113 do {
2114 reclaim_state.reclaimed_slab = 0;
2115 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2116 ret += reclaim_state.reclaimed_slab;
2117 } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
2118 }
2119
2120 out:
2121 current->reclaim_state = NULL;
2122
2123 return ret;
2124 }
2125 #endif
2126
2127 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2128 not required for correctness. So if the last cpu in a node goes
2129 away, we get changed to run anywhere: as the first one comes back,
2130 restore their cpu bindings. */
2131 static int __devinit cpu_callback(struct notifier_block *nfb,
2132 unsigned long action, void *hcpu)
2133 {
2134 int nid;
2135
2136 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2137 for_each_node_state(nid, N_HIGH_MEMORY) {
2138 pg_data_t *pgdat = NODE_DATA(nid);
2139 node_to_cpumask_ptr(mask, pgdat->node_id);
2140
2141 if (any_online_cpu(*mask) < nr_cpu_ids)
2142 /* One of our CPUs online: restore mask */
2143 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2144 }
2145 }
2146 return NOTIFY_OK;
2147 }
2148
2149 /*
2150 * This kswapd start function will be called by init and node-hot-add.
2151 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2152 */
2153 int kswapd_run(int nid)
2154 {
2155 pg_data_t *pgdat = NODE_DATA(nid);
2156 int ret = 0;
2157
2158 if (pgdat->kswapd)
2159 return 0;
2160
2161 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2162 if (IS_ERR(pgdat->kswapd)) {
2163 /* failure at boot is fatal */
2164 BUG_ON(system_state == SYSTEM_BOOTING);
2165 printk("Failed to start kswapd on node %d\n",nid);
2166 ret = -1;
2167 }
2168 return ret;
2169 }
2170
2171 static int __init kswapd_init(void)
2172 {
2173 int nid;
2174
2175 swap_setup();
2176 for_each_node_state(nid, N_HIGH_MEMORY)
2177 kswapd_run(nid);
2178 hotcpu_notifier(cpu_callback, 0);
2179 return 0;
2180 }
2181
2182 module_init(kswapd_init)
2183
2184 #ifdef CONFIG_NUMA
2185 /*
2186 * Zone reclaim mode
2187 *
2188 * If non-zero call zone_reclaim when the number of free pages falls below
2189 * the watermarks.
2190 */
2191 int zone_reclaim_mode __read_mostly;
2192
2193 #define RECLAIM_OFF 0
2194 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2195 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2196 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2197
2198 /*
2199 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2200 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2201 * a zone.
2202 */
2203 #define ZONE_RECLAIM_PRIORITY 4
2204
2205 /*
2206 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2207 * occur.
2208 */
2209 int sysctl_min_unmapped_ratio = 1;
2210
2211 /*
2212 * If the number of slab pages in a zone grows beyond this percentage then
2213 * slab reclaim needs to occur.
2214 */
2215 int sysctl_min_slab_ratio = 5;
2216
2217 /*
2218 * Try to free up some pages from this zone through reclaim.
2219 */
2220 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2221 {
2222 /* Minimum pages needed in order to stay on node */
2223 const unsigned long nr_pages = 1 << order;
2224 struct task_struct *p = current;
2225 struct reclaim_state reclaim_state;
2226 int priority;
2227 unsigned long nr_reclaimed = 0;
2228 struct scan_control sc = {
2229 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2230 .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2231 .swap_cluster_max = max_t(unsigned long, nr_pages,
2232 SWAP_CLUSTER_MAX),
2233 .gfp_mask = gfp_mask,
2234 .swappiness = vm_swappiness,
2235 .isolate_pages = isolate_pages_global,
2236 };
2237 unsigned long slab_reclaimable;
2238
2239 disable_swap_token();
2240 cond_resched();
2241 /*
2242 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2243 * and we also need to be able to write out pages for RECLAIM_WRITE
2244 * and RECLAIM_SWAP.
2245 */
2246 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2247 reclaim_state.reclaimed_slab = 0;
2248 p->reclaim_state = &reclaim_state;
2249
2250 if (zone_page_state(zone, NR_FILE_PAGES) -
2251 zone_page_state(zone, NR_FILE_MAPPED) >
2252 zone->min_unmapped_pages) {
2253 /*
2254 * Free memory by calling shrink zone with increasing
2255 * priorities until we have enough memory freed.
2256 */
2257 priority = ZONE_RECLAIM_PRIORITY;
2258 do {
2259 note_zone_scanning_priority(zone, priority);
2260 nr_reclaimed += shrink_zone(priority, zone, &sc);
2261 priority--;
2262 } while (priority >= 0 && nr_reclaimed < nr_pages);
2263 }
2264
2265 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2266 if (slab_reclaimable > zone->min_slab_pages) {
2267 /*
2268 * shrink_slab() does not currently allow us to determine how
2269 * many pages were freed in this zone. So we take the current
2270 * number of slab pages and shake the slab until it is reduced
2271 * by the same nr_pages that we used for reclaiming unmapped
2272 * pages.
2273 *
2274 * Note that shrink_slab will free memory on all zones and may
2275 * take a long time.
2276 */
2277 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2278 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2279 slab_reclaimable - nr_pages)
2280 ;
2281
2282 /*
2283 * Update nr_reclaimed by the number of slab pages we
2284 * reclaimed from this zone.
2285 */
2286 nr_reclaimed += slab_reclaimable -
2287 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2288 }
2289
2290 p->reclaim_state = NULL;
2291 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2292 return nr_reclaimed >= nr_pages;
2293 }
2294
2295 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2296 {
2297 int node_id;
2298 int ret;
2299
2300 /*
2301 * Zone reclaim reclaims unmapped file backed pages and
2302 * slab pages if we are over the defined limits.
2303 *
2304 * A small portion of unmapped file backed pages is needed for
2305 * file I/O otherwise pages read by file I/O will be immediately
2306 * thrown out if the zone is overallocated. So we do not reclaim
2307 * if less than a specified percentage of the zone is used by
2308 * unmapped file backed pages.
2309 */
2310 if (zone_page_state(zone, NR_FILE_PAGES) -
2311 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
2312 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
2313 <= zone->min_slab_pages)
2314 return 0;
2315
2316 if (zone_is_all_unreclaimable(zone))
2317 return 0;
2318
2319 /*
2320 * Do not scan if the allocation should not be delayed.
2321 */
2322 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2323 return 0;
2324
2325 /*
2326 * Only run zone reclaim on the local zone or on zones that do not
2327 * have associated processors. This will favor the local processor
2328 * over remote processors and spread off node memory allocations
2329 * as wide as possible.
2330 */
2331 node_id = zone_to_nid(zone);
2332 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2333 return 0;
2334
2335 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2336 return 0;
2337 ret = __zone_reclaim(zone, gfp_mask, order);
2338 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2339
2340 return ret;
2341 }
2342 #endif
2343
2344 #ifdef CONFIG_UNEVICTABLE_LRU
2345 /*
2346 * page_evictable - test whether a page is evictable
2347 * @page: the page to test
2348 * @vma: the VMA in which the page is or will be mapped, may be NULL
2349 *
2350 * Test whether page is evictable--i.e., should be placed on active/inactive
2351 * lists vs unevictable list. The vma argument is !NULL when called from the
2352 * fault path to determine how to instantate a new page.
2353 *
2354 * Reasons page might not be evictable:
2355 * (1) page's mapping marked unevictable
2356 * (2) page is part of an mlocked VMA
2357 *
2358 */
2359 int page_evictable(struct page *page, struct vm_area_struct *vma)
2360 {
2361
2362 if (mapping_unevictable(page_mapping(page)))
2363 return 0;
2364
2365 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2366 return 0;
2367
2368 return 1;
2369 }
2370
2371 /**
2372 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2373 * @page: page to check evictability and move to appropriate lru list
2374 * @zone: zone page is in
2375 *
2376 * Checks a page for evictability and moves the page to the appropriate
2377 * zone lru list.
2378 *
2379 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2380 * have PageUnevictable set.
2381 */
2382 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2383 {
2384 VM_BUG_ON(PageActive(page));
2385
2386 retry:
2387 ClearPageUnevictable(page);
2388 if (page_evictable(page, NULL)) {
2389 enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
2390
2391 __dec_zone_state(zone, NR_UNEVICTABLE);
2392 list_move(&page->lru, &zone->lru[l].list);
2393 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2394 __count_vm_event(UNEVICTABLE_PGRESCUED);
2395 } else {
2396 /*
2397 * rotate unevictable list
2398 */
2399 SetPageUnevictable(page);
2400 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2401 if (page_evictable(page, NULL))
2402 goto retry;
2403 }
2404 }
2405
2406 /**
2407 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2408 * @mapping: struct address_space to scan for evictable pages
2409 *
2410 * Scan all pages in mapping. Check unevictable pages for
2411 * evictability and move them to the appropriate zone lru list.
2412 */
2413 void scan_mapping_unevictable_pages(struct address_space *mapping)
2414 {
2415 pgoff_t next = 0;
2416 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2417 PAGE_CACHE_SHIFT;
2418 struct zone *zone;
2419 struct pagevec pvec;
2420
2421 if (mapping->nrpages == 0)
2422 return;
2423
2424 pagevec_init(&pvec, 0);
2425 while (next < end &&
2426 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2427 int i;
2428 int pg_scanned = 0;
2429
2430 zone = NULL;
2431
2432 for (i = 0; i < pagevec_count(&pvec); i++) {
2433 struct page *page = pvec.pages[i];
2434 pgoff_t page_index = page->index;
2435 struct zone *pagezone = page_zone(page);
2436
2437 pg_scanned++;
2438 if (page_index > next)
2439 next = page_index;
2440 next++;
2441
2442 if (pagezone != zone) {
2443 if (zone)
2444 spin_unlock_irq(&zone->lru_lock);
2445 zone = pagezone;
2446 spin_lock_irq(&zone->lru_lock);
2447 }
2448
2449 if (PageLRU(page) && PageUnevictable(page))
2450 check_move_unevictable_page(page, zone);
2451 }
2452 if (zone)
2453 spin_unlock_irq(&zone->lru_lock);
2454 pagevec_release(&pvec);
2455
2456 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2457 }
2458
2459 }
2460
2461 /**
2462 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2463 * @zone - zone of which to scan the unevictable list
2464 *
2465 * Scan @zone's unevictable LRU lists to check for pages that have become
2466 * evictable. Move those that have to @zone's inactive list where they
2467 * become candidates for reclaim, unless shrink_inactive_zone() decides
2468 * to reactivate them. Pages that are still unevictable are rotated
2469 * back onto @zone's unevictable list.
2470 */
2471 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2472 void scan_zone_unevictable_pages(struct zone *zone)
2473 {
2474 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2475 unsigned long scan;
2476 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2477
2478 while (nr_to_scan > 0) {
2479 unsigned long batch_size = min(nr_to_scan,
2480 SCAN_UNEVICTABLE_BATCH_SIZE);
2481
2482 spin_lock_irq(&zone->lru_lock);
2483 for (scan = 0; scan < batch_size; scan++) {
2484 struct page *page = lru_to_page(l_unevictable);
2485
2486 if (!trylock_page(page))
2487 continue;
2488
2489 prefetchw_prev_lru_page(page, l_unevictable, flags);
2490
2491 if (likely(PageLRU(page) && PageUnevictable(page)))
2492 check_move_unevictable_page(page, zone);
2493
2494 unlock_page(page);
2495 }
2496 spin_unlock_irq(&zone->lru_lock);
2497
2498 nr_to_scan -= batch_size;
2499 }
2500 }
2501
2502
2503 /**
2504 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2505 *
2506 * A really big hammer: scan all zones' unevictable LRU lists to check for
2507 * pages that have become evictable. Move those back to the zones'
2508 * inactive list where they become candidates for reclaim.
2509 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2510 * and we add swap to the system. As such, it runs in the context of a task
2511 * that has possibly/probably made some previously unevictable pages
2512 * evictable.
2513 */
2514 void scan_all_zones_unevictable_pages(void)
2515 {
2516 struct zone *zone;
2517
2518 for_each_zone(zone) {
2519 scan_zone_unevictable_pages(zone);
2520 }
2521 }
2522
2523 /*
2524 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2525 * all nodes' unevictable lists for evictable pages
2526 */
2527 unsigned long scan_unevictable_pages;
2528
2529 int scan_unevictable_handler(struct ctl_table *table, int write,
2530 struct file *file, void __user *buffer,
2531 size_t *length, loff_t *ppos)
2532 {
2533 proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
2534
2535 if (write && *(unsigned long *)table->data)
2536 scan_all_zones_unevictable_pages();
2537
2538 scan_unevictable_pages = 0;
2539 return 0;
2540 }
2541
2542 /*
2543 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2544 * a specified node's per zone unevictable lists for evictable pages.
2545 */
2546
2547 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2548 struct sysdev_attribute *attr,
2549 char *buf)
2550 {
2551 return sprintf(buf, "0\n"); /* always zero; should fit... */
2552 }
2553
2554 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2555 struct sysdev_attribute *attr,
2556 const char *buf, size_t count)
2557 {
2558 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2559 struct zone *zone;
2560 unsigned long res;
2561 unsigned long req = strict_strtoul(buf, 10, &res);
2562
2563 if (!req)
2564 return 1; /* zero is no-op */
2565
2566 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2567 if (!populated_zone(zone))
2568 continue;
2569 scan_zone_unevictable_pages(zone);
2570 }
2571 return 1;
2572 }
2573
2574
2575 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2576 read_scan_unevictable_node,
2577 write_scan_unevictable_node);
2578
2579 int scan_unevictable_register_node(struct node *node)
2580 {
2581 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2582 }
2583
2584 void scan_unevictable_unregister_node(struct node *node)
2585 {
2586 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
2587 }
2588
2589 #endif