mm: remove try_to_munlock from vmscan
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / mm / vmscan.c
blob74f875733e2be859b4f6e8917f36866ae9208393
1 /*
2 * linux/mm/vmscan.c
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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.
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>
44 #include <asm/tlbflush.h>
45 #include <asm/div64.h>
47 #include <linux/swapops.h>
49 #include "internal.h"
51 struct scan_control {
52 /* Incremented by the number of inactive pages that were scanned */
53 unsigned long nr_scanned;
55 /* This context's GFP mask */
56 gfp_t gfp_mask;
58 int may_writepage;
60 /* Can pages be swapped as part of reclaim? */
61 int may_swap;
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;
69 int swappiness;
71 int all_unreclaimable;
73 int order;
75 /* Which cgroup do we reclaim from */
76 struct mem_cgroup *mem_cgroup;
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);
85 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
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; \
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
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; \
107 prev = lru_to_page(&(_page->lru)); \
108 prefetchw(&prev->_field); \
110 } while (0)
111 #else
112 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
113 #endif
116 * From 0 .. 100. Higher means more swappy.
118 int vm_swappiness = 60;
119 long vm_total_pages; /* The total number of pages which the VM controls */
121 static LIST_HEAD(shrinker_list);
122 static DECLARE_RWSEM(shrinker_rwsem);
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
131 * Add a shrinker callback to be called from the vm
133 void register_shrinker(struct shrinker *shrinker)
135 shrinker->nr = 0;
136 down_write(&shrinker_rwsem);
137 list_add_tail(&shrinker->list, &shrinker_list);
138 up_write(&shrinker_rwsem);
140 EXPORT_SYMBOL(register_shrinker);
143 * Remove one
145 void unregister_shrinker(struct shrinker *shrinker)
147 down_write(&shrinker_rwsem);
148 list_del(&shrinker->list);
149 up_write(&shrinker_rwsem);
151 EXPORT_SYMBOL(unregister_shrinker);
153 #define SHRINK_BATCH 128
155 * Call the shrink functions to age shrinkable caches
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.
162 * If the vm encountered mapped pages on the LRU it increase the pressure on
163 * slab to avoid swapping.
165 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
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.
171 * Returns the number of slab objects which we shrunk.
173 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
174 unsigned long lru_pages)
176 struct shrinker *shrinker;
177 unsigned long ret = 0;
179 if (scanned == 0)
180 scanned = SWAP_CLUSTER_MAX;
182 if (!down_read_trylock(&shrinker_rwsem))
183 return 1; /* Assume we'll be able to shrink next time */
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);
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;
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.
205 if (shrinker->nr > max_pass * 2)
206 shrinker->nr = max_pass * 2;
208 total_scan = shrinker->nr;
209 shrinker->nr = 0;
211 while (total_scan >= SHRINK_BATCH) {
212 long this_scan = SHRINK_BATCH;
213 int shrink_ret;
214 int nr_before;
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;
225 cond_resched();
228 shrinker->nr += total_scan;
230 up_read(&shrinker_rwsem);
231 return ret;
234 /* Called without lock on whether page is mapped, so answer is unstable */
235 static inline int page_mapping_inuse(struct page *page)
237 struct address_space *mapping;
239 /* Page is in somebody's page tables. */
240 if (page_mapped(page))
241 return 1;
243 /* Be more reluctant to reclaim swapcache than pagecache */
244 if (PageSwapCache(page))
245 return 1;
247 mapping = page_mapping(page);
248 if (!mapping)
249 return 0;
251 /* File is mmap'd by somebody? */
252 return mapping_mapped(mapping);
255 static inline int is_page_cache_freeable(struct page *page)
257 return page_count(page) - !!PagePrivate(page) == 2;
260 static int may_write_to_queue(struct backing_dev_info *bdi)
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;
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().
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.
280 * We're allowed to run sleeping lock_page() here because we know the caller has
281 * __GFP_FS.
283 static void handle_write_error(struct address_space *mapping,
284 struct page *page, int error)
286 lock_page(page);
287 if (page_mapping(page) == mapping)
288 mapping_set_error(mapping, error);
289 unlock_page(page);
292 /* Request for sync pageout. */
293 enum pageout_io {
294 PAGEOUT_IO_ASYNC,
295 PAGEOUT_IO_SYNC,
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;
311 * pageout is called by shrink_page_list() for each dirty page.
312 * Calls ->writepage().
314 static pageout_t pageout(struct page *page, struct address_space *mapping,
315 enum pageout_io sync_writeback)
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.
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.
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().
334 if (!is_page_cache_freeable(page))
335 return PAGE_KEEP;
336 if (!mapping) {
338 * Some data journaling orphaned pages can have
339 * page->mapping == NULL while being dirty with clean buffers.
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;
348 return PAGE_KEEP;
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;
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,
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;
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.
380 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
381 wait_on_page_writeback(page);
383 if (!PageWriteback(page)) {
384 /* synchronous write or broken a_ops? */
385 ClearPageReclaim(page);
387 inc_zone_page_state(page, NR_VMSCAN_WRITE);
388 return PAGE_SUCCESS;
391 return PAGE_CLEAN;
395 * Same as remove_mapping, but if the page is removed from the mapping, it
396 * gets returned with a refcount of 0.
398 static int __remove_mapping(struct address_space *mapping, struct page *page)
400 BUG_ON(!PageLocked(page));
401 BUG_ON(mapping != page_mapping(page));
403 spin_lock_irq(&mapping->tree_lock);
405 * The non racy check for a busy page.
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:
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]
420 * [oops, our write_to data is lost]
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.
426 * Note that if SetPageDirty is always performed via set_page_dirty,
427 * and thus under tree_lock, then this ordering is not required.
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;
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);
447 return 1;
449 cannot_free:
450 spin_unlock_irq(&mapping->tree_lock);
451 return 0;
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.
460 int remove_mapping(struct address_space *mapping, struct page *page)
462 if (__remove_mapping(mapping, page)) {
464 * Unfreezing the refcount with 1 rather than 2 effectively
465 * drops the pagecache ref for us without requiring another
466 * atomic operation.
468 page_unfreeze_refs(page, 1);
469 return 1;
471 return 0;
475 * putback_lru_page - put previously isolated page onto appropriate LRU list
476 * @page: page to be put back to appropriate lru list
478 * Add previously isolated @page to appropriate LRU list.
479 * Page may still be unevictable for other reasons.
481 * lru_lock must not be held, interrupts must be enabled.
483 #ifdef CONFIG_UNEVICTABLE_LRU
484 void putback_lru_page(struct page *page)
486 int lru;
487 int active = !!TestClearPageActive(page);
488 int was_unevictable = PageUnevictable(page);
490 VM_BUG_ON(PageLRU(page));
492 redo:
493 ClearPageUnevictable(page);
495 if (page_evictable(page, NULL)) {
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.
502 lru = active + page_is_file_cache(page);
503 lru_cache_add_lru(page, lru);
504 } else {
506 * Put unevictable pages directly on zone's unevictable
507 * list.
509 lru = LRU_UNEVICTABLE;
510 add_page_to_unevictable_list(page);
512 mem_cgroup_move_lists(page, lru);
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.
519 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
520 if (!isolate_lru_page(page)) {
521 put_page(page);
522 goto redo;
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.
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);
535 put_page(page); /* drop ref from isolate */
538 #else /* CONFIG_UNEVICTABLE_LRU */
540 void putback_lru_page(struct page *page)
542 int lru;
543 VM_BUG_ON(PageLRU(page));
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);
550 #endif /* CONFIG_UNEVICTABLE_LRU */
554 * shrink_page_list() returns the number of reclaimed pages
556 static unsigned long shrink_page_list(struct list_head *page_list,
557 struct scan_control *sc,
558 enum pageout_io sync_writeback)
560 LIST_HEAD(ret_pages);
561 struct pagevec freed_pvec;
562 int pgactivate = 0;
563 unsigned long nr_reclaimed = 0;
565 cond_resched();
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;
574 cond_resched();
576 page = lru_to_page(page_list);
577 list_del(&page->lru);
579 if (!trylock_page(page))
580 goto keep;
582 VM_BUG_ON(PageActive(page));
584 sc->nr_scanned++;
586 if (unlikely(!page_evictable(page, NULL)))
587 goto cull_mlocked;
589 if (!sc->may_swap && page_mapped(page))
590 goto keep_locked;
592 /* Double the slab pressure for mapped and swapcache pages */
593 if (page_mapped(page) || PageSwapCache(page))
594 sc->nr_scanned++;
596 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
597 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
599 if (PageWriteback(page)) {
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.
608 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
609 wait_on_page_writeback(page);
610 else
611 goto keep_locked;
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;
620 #ifdef CONFIG_SWAP
622 * Anonymous process memory has backing store?
623 * Try to allocate it some swap space here.
625 if (PageAnon(page) && !PageSwapCache(page)) {
626 if (!(sc->gfp_mask & __GFP_IO))
627 goto keep_locked;
628 if (!add_to_swap(page, GFP_ATOMIC))
629 goto activate_locked;
630 may_enter_fs = 1;
632 #endif /* CONFIG_SWAP */
634 mapping = page_mapping(page);
637 * The page is mapped into the page tables of one or more
638 * processes. Try to unmap it here.
640 if (page_mapped(page) && mapping) {
641 switch (try_to_unmap(page, 0)) {
642 case SWAP_FAIL:
643 goto activate_locked;
644 case SWAP_AGAIN:
645 goto keep_locked;
646 case SWAP_MLOCK:
647 goto cull_mlocked;
648 case SWAP_SUCCESS:
649 ; /* try to free the page below */
653 if (PageDirty(page)) {
654 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
655 goto keep_locked;
656 if (!may_enter_fs)
657 goto keep_locked;
658 if (!sc->may_writepage)
659 goto keep_locked;
661 /* Page is dirty, try to write it out here */
662 switch (pageout(page, mapping, sync_writeback)) {
663 case PAGE_KEEP:
664 goto keep_locked;
665 case PAGE_ACTIVATE:
666 goto activate_locked;
667 case PAGE_SUCCESS:
668 if (PageWriteback(page) || PageDirty(page))
669 goto keep;
671 * A synchronous write - probably a ramdisk. Go
672 * ahead and try to reclaim the page.
674 if (!trylock_page(page))
675 goto keep;
676 if (PageDirty(page) || PageWriteback(page))
677 goto keep_locked;
678 mapping = page_mapping(page);
679 case PAGE_CLEAN:
680 ; /* try to free the page below */
685 * If the page has buffers, try to free the buffer mappings
686 * associated with this page. If we succeed we try to free
687 * the page as well.
689 * We do this even if the page is PageDirty().
690 * try_to_release_page() does not perform I/O, but it is
691 * possible for a page to have PageDirty set, but it is actually
692 * clean (all its buffers are clean). This happens if the
693 * buffers were written out directly, with submit_bh(). ext3
694 * will do this, as well as the blockdev mapping.
695 * try_to_release_page() will discover that cleanness and will
696 * drop the buffers and mark the page clean - it can be freed.
698 * Rarely, pages can have buffers and no ->mapping. These are
699 * the pages which were not successfully invalidated in
700 * truncate_complete_page(). We try to drop those buffers here
701 * and if that worked, and the page is no longer mapped into
702 * process address space (page_count == 1) it can be freed.
703 * Otherwise, leave the page on the LRU so it is swappable.
705 if (PagePrivate(page)) {
706 if (!try_to_release_page(page, sc->gfp_mask))
707 goto activate_locked;
708 if (!mapping && page_count(page) == 1) {
709 unlock_page(page);
710 if (put_page_testzero(page))
711 goto free_it;
712 else {
714 * rare race with speculative reference.
715 * the speculative reference will free
716 * this page shortly, so we may
717 * increment nr_reclaimed here (and
718 * leave it off the LRU).
720 nr_reclaimed++;
721 continue;
726 if (!mapping || !__remove_mapping(mapping, page))
727 goto keep_locked;
730 * At this point, we have no other references and there is
731 * no way to pick any more up (removed from LRU, removed
732 * from pagecache). Can use non-atomic bitops now (and
733 * we obviously don't have to worry about waking up a process
734 * waiting on the page lock, because there are no references.
736 __clear_page_locked(page);
737 free_it:
738 nr_reclaimed++;
739 if (!pagevec_add(&freed_pvec, page)) {
740 __pagevec_free(&freed_pvec);
741 pagevec_reinit(&freed_pvec);
743 continue;
745 cull_mlocked:
746 if (PageSwapCache(page))
747 try_to_free_swap(page);
748 unlock_page(page);
749 putback_lru_page(page);
750 continue;
752 activate_locked:
753 /* Not a candidate for swapping, so reclaim swap space. */
754 if (PageSwapCache(page) && vm_swap_full())
755 try_to_free_swap(page);
756 VM_BUG_ON(PageActive(page));
757 SetPageActive(page);
758 pgactivate++;
759 keep_locked:
760 unlock_page(page);
761 keep:
762 list_add(&page->lru, &ret_pages);
763 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
765 list_splice(&ret_pages, page_list);
766 if (pagevec_count(&freed_pvec))
767 __pagevec_free(&freed_pvec);
768 count_vm_events(PGACTIVATE, pgactivate);
769 return nr_reclaimed;
772 /* LRU Isolation modes. */
773 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
774 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
775 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
778 * Attempt to remove the specified page from its LRU. Only take this page
779 * if it is of the appropriate PageActive status. Pages which are being
780 * freed elsewhere are also ignored.
782 * page: page to consider
783 * mode: one of the LRU isolation modes defined above
785 * returns 0 on success, -ve errno on failure.
787 int __isolate_lru_page(struct page *page, int mode, int file)
789 int ret = -EINVAL;
791 /* Only take pages on the LRU. */
792 if (!PageLRU(page))
793 return ret;
796 * When checking the active state, we need to be sure we are
797 * dealing with comparible boolean values. Take the logical not
798 * of each.
800 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
801 return ret;
803 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
804 return ret;
807 * When this function is being called for lumpy reclaim, we
808 * initially look into all LRU pages, active, inactive and
809 * unevictable; only give shrink_page_list evictable pages.
811 if (PageUnevictable(page))
812 return ret;
814 ret = -EBUSY;
815 if (likely(get_page_unless_zero(page))) {
817 * Be careful not to clear PageLRU until after we're
818 * sure the page is not being freed elsewhere -- the
819 * page release code relies on it.
821 ClearPageLRU(page);
822 ret = 0;
825 return ret;
829 * zone->lru_lock is heavily contended. Some of the functions that
830 * shrink the lists perform better by taking out a batch of pages
831 * and working on them outside the LRU lock.
833 * For pagecache intensive workloads, this function is the hottest
834 * spot in the kernel (apart from copy_*_user functions).
836 * Appropriate locks must be held before calling this function.
838 * @nr_to_scan: The number of pages to look through on the list.
839 * @src: The LRU list to pull pages off.
840 * @dst: The temp list to put pages on to.
841 * @scanned: The number of pages that were scanned.
842 * @order: The caller's attempted allocation order
843 * @mode: One of the LRU isolation modes
844 * @file: True [1] if isolating file [!anon] pages
846 * returns how many pages were moved onto *@dst.
848 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
849 struct list_head *src, struct list_head *dst,
850 unsigned long *scanned, int order, int mode, int file)
852 unsigned long nr_taken = 0;
853 unsigned long scan;
855 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
856 struct page *page;
857 unsigned long pfn;
858 unsigned long end_pfn;
859 unsigned long page_pfn;
860 int zone_id;
862 page = lru_to_page(src);
863 prefetchw_prev_lru_page(page, src, flags);
865 VM_BUG_ON(!PageLRU(page));
867 switch (__isolate_lru_page(page, mode, file)) {
868 case 0:
869 list_move(&page->lru, dst);
870 nr_taken++;
871 break;
873 case -EBUSY:
874 /* else it is being freed elsewhere */
875 list_move(&page->lru, src);
876 continue;
878 default:
879 BUG();
882 if (!order)
883 continue;
886 * Attempt to take all pages in the order aligned region
887 * surrounding the tag page. Only take those pages of
888 * the same active state as that tag page. We may safely
889 * round the target page pfn down to the requested order
890 * as the mem_map is guarenteed valid out to MAX_ORDER,
891 * where that page is in a different zone we will detect
892 * it from its zone id and abort this block scan.
894 zone_id = page_zone_id(page);
895 page_pfn = page_to_pfn(page);
896 pfn = page_pfn & ~((1 << order) - 1);
897 end_pfn = pfn + (1 << order);
898 for (; pfn < end_pfn; pfn++) {
899 struct page *cursor_page;
901 /* The target page is in the block, ignore it. */
902 if (unlikely(pfn == page_pfn))
903 continue;
905 /* Avoid holes within the zone. */
906 if (unlikely(!pfn_valid_within(pfn)))
907 break;
909 cursor_page = pfn_to_page(pfn);
911 /* Check that we have not crossed a zone boundary. */
912 if (unlikely(page_zone_id(cursor_page) != zone_id))
913 continue;
914 switch (__isolate_lru_page(cursor_page, mode, file)) {
915 case 0:
916 list_move(&cursor_page->lru, dst);
917 nr_taken++;
918 scan++;
919 break;
921 case -EBUSY:
922 /* else it is being freed elsewhere */
923 list_move(&cursor_page->lru, src);
924 default:
925 break; /* ! on LRU or wrong list */
930 *scanned = scan;
931 return nr_taken;
934 static unsigned long isolate_pages_global(unsigned long nr,
935 struct list_head *dst,
936 unsigned long *scanned, int order,
937 int mode, struct zone *z,
938 struct mem_cgroup *mem_cont,
939 int active, int file)
941 int lru = LRU_BASE;
942 if (active)
943 lru += LRU_ACTIVE;
944 if (file)
945 lru += LRU_FILE;
946 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
947 mode, !!file);
951 * clear_active_flags() is a helper for shrink_active_list(), clearing
952 * any active bits from the pages in the list.
954 static unsigned long clear_active_flags(struct list_head *page_list,
955 unsigned int *count)
957 int nr_active = 0;
958 int lru;
959 struct page *page;
961 list_for_each_entry(page, page_list, lru) {
962 lru = page_is_file_cache(page);
963 if (PageActive(page)) {
964 lru += LRU_ACTIVE;
965 ClearPageActive(page);
966 nr_active++;
968 count[lru]++;
971 return nr_active;
975 * isolate_lru_page - tries to isolate a page from its LRU list
976 * @page: page to isolate from its LRU list
978 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
979 * vmstat statistic corresponding to whatever LRU list the page was on.
981 * Returns 0 if the page was removed from an LRU list.
982 * Returns -EBUSY if the page was not on an LRU list.
984 * The returned page will have PageLRU() cleared. If it was found on
985 * the active list, it will have PageActive set. If it was found on
986 * the unevictable list, it will have the PageUnevictable bit set. That flag
987 * may need to be cleared by the caller before letting the page go.
989 * The vmstat statistic corresponding to the list on which the page was
990 * found will be decremented.
992 * Restrictions:
993 * (1) Must be called with an elevated refcount on the page. This is a
994 * fundamentnal difference from isolate_lru_pages (which is called
995 * without a stable reference).
996 * (2) the lru_lock must not be held.
997 * (3) interrupts must be enabled.
999 int isolate_lru_page(struct page *page)
1001 int ret = -EBUSY;
1003 if (PageLRU(page)) {
1004 struct zone *zone = page_zone(page);
1006 spin_lock_irq(&zone->lru_lock);
1007 if (PageLRU(page) && get_page_unless_zero(page)) {
1008 int lru = page_lru(page);
1009 ret = 0;
1010 ClearPageLRU(page);
1012 del_page_from_lru_list(zone, page, lru);
1014 spin_unlock_irq(&zone->lru_lock);
1016 return ret;
1020 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1021 * of reclaimed pages
1023 static unsigned long shrink_inactive_list(unsigned long max_scan,
1024 struct zone *zone, struct scan_control *sc,
1025 int priority, int file)
1027 LIST_HEAD(page_list);
1028 struct pagevec pvec;
1029 unsigned long nr_scanned = 0;
1030 unsigned long nr_reclaimed = 0;
1032 pagevec_init(&pvec, 1);
1034 lru_add_drain();
1035 spin_lock_irq(&zone->lru_lock);
1036 do {
1037 struct page *page;
1038 unsigned long nr_taken;
1039 unsigned long nr_scan;
1040 unsigned long nr_freed;
1041 unsigned long nr_active;
1042 unsigned int count[NR_LRU_LISTS] = { 0, };
1043 int mode = ISOLATE_INACTIVE;
1046 * If we need a large contiguous chunk of memory, or have
1047 * trouble getting a small set of contiguous pages, we
1048 * will reclaim both active and inactive pages.
1050 * We use the same threshold as pageout congestion_wait below.
1052 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1053 mode = ISOLATE_BOTH;
1054 else if (sc->order && priority < DEF_PRIORITY - 2)
1055 mode = ISOLATE_BOTH;
1057 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1058 &page_list, &nr_scan, sc->order, mode,
1059 zone, sc->mem_cgroup, 0, file);
1060 nr_active = clear_active_flags(&page_list, count);
1061 __count_vm_events(PGDEACTIVATE, nr_active);
1063 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1064 -count[LRU_ACTIVE_FILE]);
1065 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1066 -count[LRU_INACTIVE_FILE]);
1067 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1068 -count[LRU_ACTIVE_ANON]);
1069 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1070 -count[LRU_INACTIVE_ANON]);
1072 if (scan_global_lru(sc)) {
1073 zone->pages_scanned += nr_scan;
1074 zone->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1075 zone->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1076 zone->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1077 zone->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1079 spin_unlock_irq(&zone->lru_lock);
1081 nr_scanned += nr_scan;
1082 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1085 * If we are direct reclaiming for contiguous pages and we do
1086 * not reclaim everything in the list, try again and wait
1087 * for IO to complete. This will stall high-order allocations
1088 * but that should be acceptable to the caller
1090 if (nr_freed < nr_taken && !current_is_kswapd() &&
1091 sc->order > PAGE_ALLOC_COSTLY_ORDER) {
1092 congestion_wait(WRITE, HZ/10);
1095 * The attempt at page out may have made some
1096 * of the pages active, mark them inactive again.
1098 nr_active = clear_active_flags(&page_list, count);
1099 count_vm_events(PGDEACTIVATE, nr_active);
1101 nr_freed += shrink_page_list(&page_list, sc,
1102 PAGEOUT_IO_SYNC);
1105 nr_reclaimed += nr_freed;
1106 local_irq_disable();
1107 if (current_is_kswapd()) {
1108 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
1109 __count_vm_events(KSWAPD_STEAL, nr_freed);
1110 } else if (scan_global_lru(sc))
1111 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1113 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1115 if (nr_taken == 0)
1116 goto done;
1118 spin_lock(&zone->lru_lock);
1120 * Put back any unfreeable pages.
1122 while (!list_empty(&page_list)) {
1123 int lru;
1124 page = lru_to_page(&page_list);
1125 VM_BUG_ON(PageLRU(page));
1126 list_del(&page->lru);
1127 if (unlikely(!page_evictable(page, NULL))) {
1128 spin_unlock_irq(&zone->lru_lock);
1129 putback_lru_page(page);
1130 spin_lock_irq(&zone->lru_lock);
1131 continue;
1133 SetPageLRU(page);
1134 lru = page_lru(page);
1135 add_page_to_lru_list(zone, page, lru);
1136 mem_cgroup_move_lists(page, lru);
1137 if (PageActive(page) && scan_global_lru(sc)) {
1138 int file = !!page_is_file_cache(page);
1139 zone->recent_rotated[file]++;
1141 if (!pagevec_add(&pvec, page)) {
1142 spin_unlock_irq(&zone->lru_lock);
1143 __pagevec_release(&pvec);
1144 spin_lock_irq(&zone->lru_lock);
1147 } while (nr_scanned < max_scan);
1148 spin_unlock(&zone->lru_lock);
1149 done:
1150 local_irq_enable();
1151 pagevec_release(&pvec);
1152 return nr_reclaimed;
1156 * We are about to scan this zone at a certain priority level. If that priority
1157 * level is smaller (ie: more urgent) than the previous priority, then note
1158 * that priority level within the zone. This is done so that when the next
1159 * process comes in to scan this zone, it will immediately start out at this
1160 * priority level rather than having to build up its own scanning priority.
1161 * Here, this priority affects only the reclaim-mapped threshold.
1163 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1165 if (priority < zone->prev_priority)
1166 zone->prev_priority = priority;
1169 static inline int zone_is_near_oom(struct zone *zone)
1171 return zone->pages_scanned >= (zone_lru_pages(zone) * 3);
1175 * This moves pages from the active list to the inactive list.
1177 * We move them the other way if the page is referenced by one or more
1178 * processes, from rmap.
1180 * If the pages are mostly unmapped, the processing is fast and it is
1181 * appropriate to hold zone->lru_lock across the whole operation. But if
1182 * the pages are mapped, the processing is slow (page_referenced()) so we
1183 * should drop zone->lru_lock around each page. It's impossible to balance
1184 * this, so instead we remove the pages from the LRU while processing them.
1185 * It is safe to rely on PG_active against the non-LRU pages in here because
1186 * nobody will play with that bit on a non-LRU page.
1188 * The downside is that we have to touch page->_count against each page.
1189 * But we had to alter page->flags anyway.
1193 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1194 struct scan_control *sc, int priority, int file)
1196 unsigned long pgmoved;
1197 int pgdeactivate = 0;
1198 unsigned long pgscanned;
1199 LIST_HEAD(l_hold); /* The pages which were snipped off */
1200 LIST_HEAD(l_inactive);
1201 struct page *page;
1202 struct pagevec pvec;
1203 enum lru_list lru;
1205 lru_add_drain();
1206 spin_lock_irq(&zone->lru_lock);
1207 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1208 ISOLATE_ACTIVE, zone,
1209 sc->mem_cgroup, 1, file);
1211 * zone->pages_scanned is used for detect zone's oom
1212 * mem_cgroup remembers nr_scan by itself.
1214 if (scan_global_lru(sc)) {
1215 zone->pages_scanned += pgscanned;
1216 zone->recent_scanned[!!file] += pgmoved;
1219 if (file)
1220 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1221 else
1222 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
1223 spin_unlock_irq(&zone->lru_lock);
1225 pgmoved = 0;
1226 while (!list_empty(&l_hold)) {
1227 cond_resched();
1228 page = lru_to_page(&l_hold);
1229 list_del(&page->lru);
1231 if (unlikely(!page_evictable(page, NULL))) {
1232 putback_lru_page(page);
1233 continue;
1236 /* page_referenced clears PageReferenced */
1237 if (page_mapping_inuse(page) &&
1238 page_referenced(page, 0, sc->mem_cgroup))
1239 pgmoved++;
1241 list_add(&page->lru, &l_inactive);
1244 spin_lock_irq(&zone->lru_lock);
1246 * Count referenced pages from currently used mappings as
1247 * rotated, even though they are moved to the inactive list.
1248 * This helps balance scan pressure between file and anonymous
1249 * pages in get_scan_ratio.
1251 zone->recent_rotated[!!file] += pgmoved;
1254 * Move the pages to the [file or anon] inactive list.
1256 pagevec_init(&pvec, 1);
1258 pgmoved = 0;
1259 lru = LRU_BASE + file * LRU_FILE;
1260 while (!list_empty(&l_inactive)) {
1261 page = lru_to_page(&l_inactive);
1262 prefetchw_prev_lru_page(page, &l_inactive, flags);
1263 VM_BUG_ON(PageLRU(page));
1264 SetPageLRU(page);
1265 VM_BUG_ON(!PageActive(page));
1266 ClearPageActive(page);
1268 list_move(&page->lru, &zone->lru[lru].list);
1269 mem_cgroup_move_lists(page, lru);
1270 pgmoved++;
1271 if (!pagevec_add(&pvec, page)) {
1272 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1273 spin_unlock_irq(&zone->lru_lock);
1274 pgdeactivate += pgmoved;
1275 pgmoved = 0;
1276 if (buffer_heads_over_limit)
1277 pagevec_strip(&pvec);
1278 __pagevec_release(&pvec);
1279 spin_lock_irq(&zone->lru_lock);
1282 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1283 pgdeactivate += pgmoved;
1284 if (buffer_heads_over_limit) {
1285 spin_unlock_irq(&zone->lru_lock);
1286 pagevec_strip(&pvec);
1287 spin_lock_irq(&zone->lru_lock);
1289 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1290 __count_vm_events(PGDEACTIVATE, pgdeactivate);
1291 spin_unlock_irq(&zone->lru_lock);
1292 if (vm_swap_full())
1293 pagevec_swap_free(&pvec);
1295 pagevec_release(&pvec);
1298 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1299 struct zone *zone, struct scan_control *sc, int priority)
1301 int file = is_file_lru(lru);
1303 if (lru == LRU_ACTIVE_FILE) {
1304 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1305 return 0;
1308 if (lru == LRU_ACTIVE_ANON &&
1309 (!scan_global_lru(sc) || inactive_anon_is_low(zone))) {
1310 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1311 return 0;
1313 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1317 * Determine how aggressively the anon and file LRU lists should be
1318 * scanned. The relative value of each set of LRU lists is determined
1319 * by looking at the fraction of the pages scanned we did rotate back
1320 * onto the active list instead of evict.
1322 * percent[0] specifies how much pressure to put on ram/swap backed
1323 * memory, while percent[1] determines pressure on the file LRUs.
1325 static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1326 unsigned long *percent)
1328 unsigned long anon, file, free;
1329 unsigned long anon_prio, file_prio;
1330 unsigned long ap, fp;
1332 anon = zone_page_state(zone, NR_ACTIVE_ANON) +
1333 zone_page_state(zone, NR_INACTIVE_ANON);
1334 file = zone_page_state(zone, NR_ACTIVE_FILE) +
1335 zone_page_state(zone, NR_INACTIVE_FILE);
1336 free = zone_page_state(zone, NR_FREE_PAGES);
1338 /* If we have no swap space, do not bother scanning anon pages. */
1339 if (nr_swap_pages <= 0) {
1340 percent[0] = 0;
1341 percent[1] = 100;
1342 return;
1345 /* If we have very few page cache pages, force-scan anon pages. */
1346 if (unlikely(file + free <= zone->pages_high)) {
1347 percent[0] = 100;
1348 percent[1] = 0;
1349 return;
1353 * OK, so we have swap space and a fair amount of page cache
1354 * pages. We use the recently rotated / recently scanned
1355 * ratios to determine how valuable each cache is.
1357 * Because workloads change over time (and to avoid overflow)
1358 * we keep these statistics as a floating average, which ends
1359 * up weighing recent references more than old ones.
1361 * anon in [0], file in [1]
1363 if (unlikely(zone->recent_scanned[0] > anon / 4)) {
1364 spin_lock_irq(&zone->lru_lock);
1365 zone->recent_scanned[0] /= 2;
1366 zone->recent_rotated[0] /= 2;
1367 spin_unlock_irq(&zone->lru_lock);
1370 if (unlikely(zone->recent_scanned[1] > file / 4)) {
1371 spin_lock_irq(&zone->lru_lock);
1372 zone->recent_scanned[1] /= 2;
1373 zone->recent_rotated[1] /= 2;
1374 spin_unlock_irq(&zone->lru_lock);
1378 * With swappiness at 100, anonymous and file have the same priority.
1379 * This scanning priority is essentially the inverse of IO cost.
1381 anon_prio = sc->swappiness;
1382 file_prio = 200 - sc->swappiness;
1385 * The amount of pressure on anon vs file pages is inversely
1386 * proportional to the fraction of recently scanned pages on
1387 * each list that were recently referenced and in active use.
1389 ap = (anon_prio + 1) * (zone->recent_scanned[0] + 1);
1390 ap /= zone->recent_rotated[0] + 1;
1392 fp = (file_prio + 1) * (zone->recent_scanned[1] + 1);
1393 fp /= zone->recent_rotated[1] + 1;
1395 /* Normalize to percentages */
1396 percent[0] = 100 * ap / (ap + fp + 1);
1397 percent[1] = 100 - percent[0];
1402 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1404 static unsigned long shrink_zone(int priority, struct zone *zone,
1405 struct scan_control *sc)
1407 unsigned long nr[NR_LRU_LISTS];
1408 unsigned long nr_to_scan;
1409 unsigned long nr_reclaimed = 0;
1410 unsigned long percent[2]; /* anon @ 0; file @ 1 */
1411 enum lru_list l;
1413 get_scan_ratio(zone, sc, percent);
1415 for_each_evictable_lru(l) {
1416 if (scan_global_lru(sc)) {
1417 int file = is_file_lru(l);
1418 int scan;
1420 scan = zone_page_state(zone, NR_LRU_BASE + l);
1421 if (priority) {
1422 scan >>= priority;
1423 scan = (scan * percent[file]) / 100;
1425 zone->lru[l].nr_scan += scan;
1426 nr[l] = zone->lru[l].nr_scan;
1427 if (nr[l] >= sc->swap_cluster_max)
1428 zone->lru[l].nr_scan = 0;
1429 else
1430 nr[l] = 0;
1431 } else {
1433 * This reclaim occurs not because zone memory shortage
1434 * but because memory controller hits its limit.
1435 * Don't modify zone reclaim related data.
1437 nr[l] = mem_cgroup_calc_reclaim(sc->mem_cgroup, zone,
1438 priority, l);
1442 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1443 nr[LRU_INACTIVE_FILE]) {
1444 for_each_evictable_lru(l) {
1445 if (nr[l]) {
1446 nr_to_scan = min(nr[l],
1447 (unsigned long)sc->swap_cluster_max);
1448 nr[l] -= nr_to_scan;
1450 nr_reclaimed += shrink_list(l, nr_to_scan,
1451 zone, sc, priority);
1457 * Even if we did not try to evict anon pages at all, we want to
1458 * rebalance the anon lru active/inactive ratio.
1460 if (!scan_global_lru(sc) || inactive_anon_is_low(zone))
1461 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1462 else if (!scan_global_lru(sc))
1463 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1465 throttle_vm_writeout(sc->gfp_mask);
1466 return nr_reclaimed;
1470 * This is the direct reclaim path, for page-allocating processes. We only
1471 * try to reclaim pages from zones which will satisfy the caller's allocation
1472 * request.
1474 * We reclaim from a zone even if that zone is over pages_high. Because:
1475 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1476 * allocation or
1477 * b) The zones may be over pages_high but they must go *over* pages_high to
1478 * satisfy the `incremental min' zone defense algorithm.
1480 * Returns the number of reclaimed pages.
1482 * If a zone is deemed to be full of pinned pages then just give it a light
1483 * scan then give up on it.
1485 static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
1486 struct scan_control *sc)
1488 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1489 unsigned long nr_reclaimed = 0;
1490 struct zoneref *z;
1491 struct zone *zone;
1493 sc->all_unreclaimable = 1;
1494 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1495 if (!populated_zone(zone))
1496 continue;
1498 * Take care memory controller reclaiming has small influence
1499 * to global LRU.
1501 if (scan_global_lru(sc)) {
1502 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1503 continue;
1504 note_zone_scanning_priority(zone, priority);
1506 if (zone_is_all_unreclaimable(zone) &&
1507 priority != DEF_PRIORITY)
1508 continue; /* Let kswapd poll it */
1509 sc->all_unreclaimable = 0;
1510 } else {
1512 * Ignore cpuset limitation here. We just want to reduce
1513 * # of used pages by us regardless of memory shortage.
1515 sc->all_unreclaimable = 0;
1516 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1517 priority);
1520 nr_reclaimed += shrink_zone(priority, zone, sc);
1523 return nr_reclaimed;
1527 * This is the main entry point to direct page reclaim.
1529 * If a full scan of the inactive list fails to free enough memory then we
1530 * are "out of memory" and something needs to be killed.
1532 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1533 * high - the zone may be full of dirty or under-writeback pages, which this
1534 * caller can't do much about. We kick pdflush and take explicit naps in the
1535 * hope that some of these pages can be written. But if the allocating task
1536 * holds filesystem locks which prevent writeout this might not work, and the
1537 * allocation attempt will fail.
1539 * returns: 0, if no pages reclaimed
1540 * else, the number of pages reclaimed
1542 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1543 struct scan_control *sc)
1545 int priority;
1546 unsigned long ret = 0;
1547 unsigned long total_scanned = 0;
1548 unsigned long nr_reclaimed = 0;
1549 struct reclaim_state *reclaim_state = current->reclaim_state;
1550 unsigned long lru_pages = 0;
1551 struct zoneref *z;
1552 struct zone *zone;
1553 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1555 delayacct_freepages_start();
1557 if (scan_global_lru(sc))
1558 count_vm_event(ALLOCSTALL);
1560 * mem_cgroup will not do shrink_slab.
1562 if (scan_global_lru(sc)) {
1563 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1565 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1566 continue;
1568 lru_pages += zone_lru_pages(zone);
1572 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1573 sc->nr_scanned = 0;
1574 if (!priority)
1575 disable_swap_token();
1576 nr_reclaimed += shrink_zones(priority, zonelist, sc);
1578 * Don't shrink slabs when reclaiming memory from
1579 * over limit cgroups
1581 if (scan_global_lru(sc)) {
1582 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1583 if (reclaim_state) {
1584 nr_reclaimed += reclaim_state->reclaimed_slab;
1585 reclaim_state->reclaimed_slab = 0;
1588 total_scanned += sc->nr_scanned;
1589 if (nr_reclaimed >= sc->swap_cluster_max) {
1590 ret = nr_reclaimed;
1591 goto out;
1595 * Try to write back as many pages as we just scanned. This
1596 * tends to cause slow streaming writers to write data to the
1597 * disk smoothly, at the dirtying rate, which is nice. But
1598 * that's undesirable in laptop mode, where we *want* lumpy
1599 * writeout. So in laptop mode, write out the whole world.
1601 if (total_scanned > sc->swap_cluster_max +
1602 sc->swap_cluster_max / 2) {
1603 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1604 sc->may_writepage = 1;
1607 /* Take a nap, wait for some writeback to complete */
1608 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1609 congestion_wait(WRITE, HZ/10);
1611 /* top priority shrink_zones still had more to do? don't OOM, then */
1612 if (!sc->all_unreclaimable && scan_global_lru(sc))
1613 ret = nr_reclaimed;
1614 out:
1616 * Now that we've scanned all the zones at this priority level, note
1617 * that level within the zone so that the next thread which performs
1618 * scanning of this zone will immediately start out at this priority
1619 * level. This affects only the decision whether or not to bring
1620 * mapped pages onto the inactive list.
1622 if (priority < 0)
1623 priority = 0;
1625 if (scan_global_lru(sc)) {
1626 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1628 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1629 continue;
1631 zone->prev_priority = priority;
1633 } else
1634 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1636 delayacct_freepages_end();
1638 return ret;
1641 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1642 gfp_t gfp_mask)
1644 struct scan_control sc = {
1645 .gfp_mask = gfp_mask,
1646 .may_writepage = !laptop_mode,
1647 .swap_cluster_max = SWAP_CLUSTER_MAX,
1648 .may_swap = 1,
1649 .swappiness = vm_swappiness,
1650 .order = order,
1651 .mem_cgroup = NULL,
1652 .isolate_pages = isolate_pages_global,
1655 return do_try_to_free_pages(zonelist, &sc);
1658 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1660 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1661 gfp_t gfp_mask)
1663 struct scan_control sc = {
1664 .may_writepage = !laptop_mode,
1665 .may_swap = 1,
1666 .swap_cluster_max = SWAP_CLUSTER_MAX,
1667 .swappiness = vm_swappiness,
1668 .order = 0,
1669 .mem_cgroup = mem_cont,
1670 .isolate_pages = mem_cgroup_isolate_pages,
1672 struct zonelist *zonelist;
1674 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1675 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1676 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1677 return do_try_to_free_pages(zonelist, &sc);
1679 #endif
1682 * For kswapd, balance_pgdat() will work across all this node's zones until
1683 * they are all at pages_high.
1685 * Returns the number of pages which were actually freed.
1687 * There is special handling here for zones which are full of pinned pages.
1688 * This can happen if the pages are all mlocked, or if they are all used by
1689 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1690 * What we do is to detect the case where all pages in the zone have been
1691 * scanned twice and there has been zero successful reclaim. Mark the zone as
1692 * dead and from now on, only perform a short scan. Basically we're polling
1693 * the zone for when the problem goes away.
1695 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1696 * zones which have free_pages > pages_high, but once a zone is found to have
1697 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1698 * of the number of free pages in the lower zones. This interoperates with
1699 * the page allocator fallback scheme to ensure that aging of pages is balanced
1700 * across the zones.
1702 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1704 int all_zones_ok;
1705 int priority;
1706 int i;
1707 unsigned long total_scanned;
1708 unsigned long nr_reclaimed;
1709 struct reclaim_state *reclaim_state = current->reclaim_state;
1710 struct scan_control sc = {
1711 .gfp_mask = GFP_KERNEL,
1712 .may_swap = 1,
1713 .swap_cluster_max = SWAP_CLUSTER_MAX,
1714 .swappiness = vm_swappiness,
1715 .order = order,
1716 .mem_cgroup = NULL,
1717 .isolate_pages = isolate_pages_global,
1720 * temp_priority is used to remember the scanning priority at which
1721 * this zone was successfully refilled to free_pages == pages_high.
1723 int temp_priority[MAX_NR_ZONES];
1725 loop_again:
1726 total_scanned = 0;
1727 nr_reclaimed = 0;
1728 sc.may_writepage = !laptop_mode;
1729 count_vm_event(PAGEOUTRUN);
1731 for (i = 0; i < pgdat->nr_zones; i++)
1732 temp_priority[i] = DEF_PRIORITY;
1734 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1735 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1736 unsigned long lru_pages = 0;
1738 /* The swap token gets in the way of swapout... */
1739 if (!priority)
1740 disable_swap_token();
1742 all_zones_ok = 1;
1745 * Scan in the highmem->dma direction for the highest
1746 * zone which needs scanning
1748 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1749 struct zone *zone = pgdat->node_zones + i;
1751 if (!populated_zone(zone))
1752 continue;
1754 if (zone_is_all_unreclaimable(zone) &&
1755 priority != DEF_PRIORITY)
1756 continue;
1759 * Do some background aging of the anon list, to give
1760 * pages a chance to be referenced before reclaiming.
1762 if (inactive_anon_is_low(zone))
1763 shrink_active_list(SWAP_CLUSTER_MAX, zone,
1764 &sc, priority, 0);
1766 if (!zone_watermark_ok(zone, order, zone->pages_high,
1767 0, 0)) {
1768 end_zone = i;
1769 break;
1772 if (i < 0)
1773 goto out;
1775 for (i = 0; i <= end_zone; i++) {
1776 struct zone *zone = pgdat->node_zones + i;
1778 lru_pages += zone_lru_pages(zone);
1782 * Now scan the zone in the dma->highmem direction, stopping
1783 * at the last zone which needs scanning.
1785 * We do this because the page allocator works in the opposite
1786 * direction. This prevents the page allocator from allocating
1787 * pages behind kswapd's direction of progress, which would
1788 * cause too much scanning of the lower zones.
1790 for (i = 0; i <= end_zone; i++) {
1791 struct zone *zone = pgdat->node_zones + i;
1792 int nr_slab;
1794 if (!populated_zone(zone))
1795 continue;
1797 if (zone_is_all_unreclaimable(zone) &&
1798 priority != DEF_PRIORITY)
1799 continue;
1801 if (!zone_watermark_ok(zone, order, zone->pages_high,
1802 end_zone, 0))
1803 all_zones_ok = 0;
1804 temp_priority[i] = priority;
1805 sc.nr_scanned = 0;
1806 note_zone_scanning_priority(zone, priority);
1808 * We put equal pressure on every zone, unless one
1809 * zone has way too many pages free already.
1811 if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
1812 end_zone, 0))
1813 nr_reclaimed += shrink_zone(priority, zone, &sc);
1814 reclaim_state->reclaimed_slab = 0;
1815 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1816 lru_pages);
1817 nr_reclaimed += reclaim_state->reclaimed_slab;
1818 total_scanned += sc.nr_scanned;
1819 if (zone_is_all_unreclaimable(zone))
1820 continue;
1821 if (nr_slab == 0 && zone->pages_scanned >=
1822 (zone_lru_pages(zone) * 6))
1823 zone_set_flag(zone,
1824 ZONE_ALL_UNRECLAIMABLE);
1826 * If we've done a decent amount of scanning and
1827 * the reclaim ratio is low, start doing writepage
1828 * even in laptop mode
1830 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1831 total_scanned > nr_reclaimed + nr_reclaimed / 2)
1832 sc.may_writepage = 1;
1834 if (all_zones_ok)
1835 break; /* kswapd: all done */
1837 * OK, kswapd is getting into trouble. Take a nap, then take
1838 * another pass across the zones.
1840 if (total_scanned && priority < DEF_PRIORITY - 2)
1841 congestion_wait(WRITE, HZ/10);
1844 * We do this so kswapd doesn't build up large priorities for
1845 * example when it is freeing in parallel with allocators. It
1846 * matches the direct reclaim path behaviour in terms of impact
1847 * on zone->*_priority.
1849 if (nr_reclaimed >= SWAP_CLUSTER_MAX)
1850 break;
1852 out:
1854 * Note within each zone the priority level at which this zone was
1855 * brought into a happy state. So that the next thread which scans this
1856 * zone will start out at that priority level.
1858 for (i = 0; i < pgdat->nr_zones; i++) {
1859 struct zone *zone = pgdat->node_zones + i;
1861 zone->prev_priority = temp_priority[i];
1863 if (!all_zones_ok) {
1864 cond_resched();
1866 try_to_freeze();
1868 goto loop_again;
1871 return nr_reclaimed;
1875 * The background pageout daemon, started as a kernel thread
1876 * from the init process.
1878 * This basically trickles out pages so that we have _some_
1879 * free memory available even if there is no other activity
1880 * that frees anything up. This is needed for things like routing
1881 * etc, where we otherwise might have all activity going on in
1882 * asynchronous contexts that cannot page things out.
1884 * If there are applications that are active memory-allocators
1885 * (most normal use), this basically shouldn't matter.
1887 static int kswapd(void *p)
1889 unsigned long order;
1890 pg_data_t *pgdat = (pg_data_t*)p;
1891 struct task_struct *tsk = current;
1892 DEFINE_WAIT(wait);
1893 struct reclaim_state reclaim_state = {
1894 .reclaimed_slab = 0,
1896 node_to_cpumask_ptr(cpumask, pgdat->node_id);
1898 if (!cpumask_empty(cpumask))
1899 set_cpus_allowed_ptr(tsk, cpumask);
1900 current->reclaim_state = &reclaim_state;
1903 * Tell the memory management that we're a "memory allocator",
1904 * and that if we need more memory we should get access to it
1905 * regardless (see "__alloc_pages()"). "kswapd" should
1906 * never get caught in the normal page freeing logic.
1908 * (Kswapd normally doesn't need memory anyway, but sometimes
1909 * you need a small amount of memory in order to be able to
1910 * page out something else, and this flag essentially protects
1911 * us from recursively trying to free more memory as we're
1912 * trying to free the first piece of memory in the first place).
1914 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1915 set_freezable();
1917 order = 0;
1918 for ( ; ; ) {
1919 unsigned long new_order;
1921 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1922 new_order = pgdat->kswapd_max_order;
1923 pgdat->kswapd_max_order = 0;
1924 if (order < new_order) {
1926 * Don't sleep if someone wants a larger 'order'
1927 * allocation
1929 order = new_order;
1930 } else {
1931 if (!freezing(current))
1932 schedule();
1934 order = pgdat->kswapd_max_order;
1936 finish_wait(&pgdat->kswapd_wait, &wait);
1938 if (!try_to_freeze()) {
1939 /* We can speed up thawing tasks if we don't call
1940 * balance_pgdat after returning from the refrigerator
1942 balance_pgdat(pgdat, order);
1945 return 0;
1949 * A zone is low on free memory, so wake its kswapd task to service it.
1951 void wakeup_kswapd(struct zone *zone, int order)
1953 pg_data_t *pgdat;
1955 if (!populated_zone(zone))
1956 return;
1958 pgdat = zone->zone_pgdat;
1959 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
1960 return;
1961 if (pgdat->kswapd_max_order < order)
1962 pgdat->kswapd_max_order = order;
1963 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1964 return;
1965 if (!waitqueue_active(&pgdat->kswapd_wait))
1966 return;
1967 wake_up_interruptible(&pgdat->kswapd_wait);
1970 unsigned long global_lru_pages(void)
1972 return global_page_state(NR_ACTIVE_ANON)
1973 + global_page_state(NR_ACTIVE_FILE)
1974 + global_page_state(NR_INACTIVE_ANON)
1975 + global_page_state(NR_INACTIVE_FILE);
1978 #ifdef CONFIG_PM
1980 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1981 * from LRU lists system-wide, for given pass and priority, and returns the
1982 * number of reclaimed pages
1984 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1986 static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
1987 int pass, struct scan_control *sc)
1989 struct zone *zone;
1990 unsigned long nr_to_scan, ret = 0;
1991 enum lru_list l;
1993 for_each_zone(zone) {
1995 if (!populated_zone(zone))
1996 continue;
1998 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
1999 continue;
2001 for_each_evictable_lru(l) {
2002 /* For pass = 0, we don't shrink the active list */
2003 if (pass == 0 &&
2004 (l == LRU_ACTIVE || l == LRU_ACTIVE_FILE))
2005 continue;
2007 zone->lru[l].nr_scan +=
2008 (zone_page_state(zone, NR_LRU_BASE + l)
2009 >> prio) + 1;
2010 if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
2011 zone->lru[l].nr_scan = 0;
2012 nr_to_scan = min(nr_pages,
2013 zone_page_state(zone,
2014 NR_LRU_BASE + l));
2015 ret += shrink_list(l, nr_to_scan, zone,
2016 sc, prio);
2017 if (ret >= nr_pages)
2018 return ret;
2023 return ret;
2027 * Try to free `nr_pages' of memory, system-wide, and return the number of
2028 * freed pages.
2030 * Rather than trying to age LRUs the aim is to preserve the overall
2031 * LRU order by reclaiming preferentially
2032 * inactive > active > active referenced > active mapped
2034 unsigned long shrink_all_memory(unsigned long nr_pages)
2036 unsigned long lru_pages, nr_slab;
2037 unsigned long ret = 0;
2038 int pass;
2039 struct reclaim_state reclaim_state;
2040 struct scan_control sc = {
2041 .gfp_mask = GFP_KERNEL,
2042 .may_swap = 0,
2043 .swap_cluster_max = nr_pages,
2044 .may_writepage = 1,
2045 .swappiness = vm_swappiness,
2046 .isolate_pages = isolate_pages_global,
2049 current->reclaim_state = &reclaim_state;
2051 lru_pages = global_lru_pages();
2052 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2053 /* If slab caches are huge, it's better to hit them first */
2054 while (nr_slab >= lru_pages) {
2055 reclaim_state.reclaimed_slab = 0;
2056 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
2057 if (!reclaim_state.reclaimed_slab)
2058 break;
2060 ret += reclaim_state.reclaimed_slab;
2061 if (ret >= nr_pages)
2062 goto out;
2064 nr_slab -= reclaim_state.reclaimed_slab;
2068 * We try to shrink LRUs in 5 passes:
2069 * 0 = Reclaim from inactive_list only
2070 * 1 = Reclaim from active list but don't reclaim mapped
2071 * 2 = 2nd pass of type 1
2072 * 3 = Reclaim mapped (normal reclaim)
2073 * 4 = 2nd pass of type 3
2075 for (pass = 0; pass < 5; pass++) {
2076 int prio;
2078 /* Force reclaiming mapped pages in the passes #3 and #4 */
2079 if (pass > 2) {
2080 sc.may_swap = 1;
2081 sc.swappiness = 100;
2084 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2085 unsigned long nr_to_scan = nr_pages - ret;
2087 sc.nr_scanned = 0;
2088 ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
2089 if (ret >= nr_pages)
2090 goto out;
2092 reclaim_state.reclaimed_slab = 0;
2093 shrink_slab(sc.nr_scanned, sc.gfp_mask,
2094 global_lru_pages());
2095 ret += reclaim_state.reclaimed_slab;
2096 if (ret >= nr_pages)
2097 goto out;
2099 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2100 congestion_wait(WRITE, HZ / 10);
2105 * If ret = 0, we could not shrink LRUs, but there may be something
2106 * in slab caches
2108 if (!ret) {
2109 do {
2110 reclaim_state.reclaimed_slab = 0;
2111 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2112 ret += reclaim_state.reclaimed_slab;
2113 } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
2116 out:
2117 current->reclaim_state = NULL;
2119 return ret;
2121 #endif
2123 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2124 not required for correctness. So if the last cpu in a node goes
2125 away, we get changed to run anywhere: as the first one comes back,
2126 restore their cpu bindings. */
2127 static int __devinit cpu_callback(struct notifier_block *nfb,
2128 unsigned long action, void *hcpu)
2130 int nid;
2132 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2133 for_each_node_state(nid, N_HIGH_MEMORY) {
2134 pg_data_t *pgdat = NODE_DATA(nid);
2135 node_to_cpumask_ptr(mask, pgdat->node_id);
2137 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2138 /* One of our CPUs online: restore mask */
2139 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2142 return NOTIFY_OK;
2146 * This kswapd start function will be called by init and node-hot-add.
2147 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2149 int kswapd_run(int nid)
2151 pg_data_t *pgdat = NODE_DATA(nid);
2152 int ret = 0;
2154 if (pgdat->kswapd)
2155 return 0;
2157 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2158 if (IS_ERR(pgdat->kswapd)) {
2159 /* failure at boot is fatal */
2160 BUG_ON(system_state == SYSTEM_BOOTING);
2161 printk("Failed to start kswapd on node %d\n",nid);
2162 ret = -1;
2164 return ret;
2167 static int __init kswapd_init(void)
2169 int nid;
2171 swap_setup();
2172 for_each_node_state(nid, N_HIGH_MEMORY)
2173 kswapd_run(nid);
2174 hotcpu_notifier(cpu_callback, 0);
2175 return 0;
2178 module_init(kswapd_init)
2180 #ifdef CONFIG_NUMA
2182 * Zone reclaim mode
2184 * If non-zero call zone_reclaim when the number of free pages falls below
2185 * the watermarks.
2187 int zone_reclaim_mode __read_mostly;
2189 #define RECLAIM_OFF 0
2190 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2191 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2192 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2195 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2196 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2197 * a zone.
2199 #define ZONE_RECLAIM_PRIORITY 4
2202 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2203 * occur.
2205 int sysctl_min_unmapped_ratio = 1;
2208 * If the number of slab pages in a zone grows beyond this percentage then
2209 * slab reclaim needs to occur.
2211 int sysctl_min_slab_ratio = 5;
2214 * Try to free up some pages from this zone through reclaim.
2216 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2218 /* Minimum pages needed in order to stay on node */
2219 const unsigned long nr_pages = 1 << order;
2220 struct task_struct *p = current;
2221 struct reclaim_state reclaim_state;
2222 int priority;
2223 unsigned long nr_reclaimed = 0;
2224 struct scan_control sc = {
2225 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2226 .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2227 .swap_cluster_max = max_t(unsigned long, nr_pages,
2228 SWAP_CLUSTER_MAX),
2229 .gfp_mask = gfp_mask,
2230 .swappiness = vm_swappiness,
2231 .isolate_pages = isolate_pages_global,
2233 unsigned long slab_reclaimable;
2235 disable_swap_token();
2236 cond_resched();
2238 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2239 * and we also need to be able to write out pages for RECLAIM_WRITE
2240 * and RECLAIM_SWAP.
2242 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2243 reclaim_state.reclaimed_slab = 0;
2244 p->reclaim_state = &reclaim_state;
2246 if (zone_page_state(zone, NR_FILE_PAGES) -
2247 zone_page_state(zone, NR_FILE_MAPPED) >
2248 zone->min_unmapped_pages) {
2250 * Free memory by calling shrink zone with increasing
2251 * priorities until we have enough memory freed.
2253 priority = ZONE_RECLAIM_PRIORITY;
2254 do {
2255 note_zone_scanning_priority(zone, priority);
2256 nr_reclaimed += shrink_zone(priority, zone, &sc);
2257 priority--;
2258 } while (priority >= 0 && nr_reclaimed < nr_pages);
2261 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2262 if (slab_reclaimable > zone->min_slab_pages) {
2264 * shrink_slab() does not currently allow us to determine how
2265 * many pages were freed in this zone. So we take the current
2266 * number of slab pages and shake the slab until it is reduced
2267 * by the same nr_pages that we used for reclaiming unmapped
2268 * pages.
2270 * Note that shrink_slab will free memory on all zones and may
2271 * take a long time.
2273 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2274 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2275 slab_reclaimable - nr_pages)
2279 * Update nr_reclaimed by the number of slab pages we
2280 * reclaimed from this zone.
2282 nr_reclaimed += slab_reclaimable -
2283 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2286 p->reclaim_state = NULL;
2287 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2288 return nr_reclaimed >= nr_pages;
2291 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2293 int node_id;
2294 int ret;
2297 * Zone reclaim reclaims unmapped file backed pages and
2298 * slab pages if we are over the defined limits.
2300 * A small portion of unmapped file backed pages is needed for
2301 * file I/O otherwise pages read by file I/O will be immediately
2302 * thrown out if the zone is overallocated. So we do not reclaim
2303 * if less than a specified percentage of the zone is used by
2304 * unmapped file backed pages.
2306 if (zone_page_state(zone, NR_FILE_PAGES) -
2307 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
2308 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
2309 <= zone->min_slab_pages)
2310 return 0;
2312 if (zone_is_all_unreclaimable(zone))
2313 return 0;
2316 * Do not scan if the allocation should not be delayed.
2318 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2319 return 0;
2322 * Only run zone reclaim on the local zone or on zones that do not
2323 * have associated processors. This will favor the local processor
2324 * over remote processors and spread off node memory allocations
2325 * as wide as possible.
2327 node_id = zone_to_nid(zone);
2328 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2329 return 0;
2331 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2332 return 0;
2333 ret = __zone_reclaim(zone, gfp_mask, order);
2334 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2336 return ret;
2338 #endif
2340 #ifdef CONFIG_UNEVICTABLE_LRU
2342 * page_evictable - test whether a page is evictable
2343 * @page: the page to test
2344 * @vma: the VMA in which the page is or will be mapped, may be NULL
2346 * Test whether page is evictable--i.e., should be placed on active/inactive
2347 * lists vs unevictable list. The vma argument is !NULL when called from the
2348 * fault path to determine how to instantate a new page.
2350 * Reasons page might not be evictable:
2351 * (1) page's mapping marked unevictable
2352 * (2) page is part of an mlocked VMA
2355 int page_evictable(struct page *page, struct vm_area_struct *vma)
2358 if (mapping_unevictable(page_mapping(page)))
2359 return 0;
2361 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2362 return 0;
2364 return 1;
2368 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2369 * @page: page to check evictability and move to appropriate lru list
2370 * @zone: zone page is in
2372 * Checks a page for evictability and moves the page to the appropriate
2373 * zone lru list.
2375 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2376 * have PageUnevictable set.
2378 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2380 VM_BUG_ON(PageActive(page));
2382 retry:
2383 ClearPageUnevictable(page);
2384 if (page_evictable(page, NULL)) {
2385 enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
2387 __dec_zone_state(zone, NR_UNEVICTABLE);
2388 list_move(&page->lru, &zone->lru[l].list);
2389 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2390 __count_vm_event(UNEVICTABLE_PGRESCUED);
2391 } else {
2393 * rotate unevictable list
2395 SetPageUnevictable(page);
2396 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2397 if (page_evictable(page, NULL))
2398 goto retry;
2403 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2404 * @mapping: struct address_space to scan for evictable pages
2406 * Scan all pages in mapping. Check unevictable pages for
2407 * evictability and move them to the appropriate zone lru list.
2409 void scan_mapping_unevictable_pages(struct address_space *mapping)
2411 pgoff_t next = 0;
2412 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2413 PAGE_CACHE_SHIFT;
2414 struct zone *zone;
2415 struct pagevec pvec;
2417 if (mapping->nrpages == 0)
2418 return;
2420 pagevec_init(&pvec, 0);
2421 while (next < end &&
2422 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2423 int i;
2424 int pg_scanned = 0;
2426 zone = NULL;
2428 for (i = 0; i < pagevec_count(&pvec); i++) {
2429 struct page *page = pvec.pages[i];
2430 pgoff_t page_index = page->index;
2431 struct zone *pagezone = page_zone(page);
2433 pg_scanned++;
2434 if (page_index > next)
2435 next = page_index;
2436 next++;
2438 if (pagezone != zone) {
2439 if (zone)
2440 spin_unlock_irq(&zone->lru_lock);
2441 zone = pagezone;
2442 spin_lock_irq(&zone->lru_lock);
2445 if (PageLRU(page) && PageUnevictable(page))
2446 check_move_unevictable_page(page, zone);
2448 if (zone)
2449 spin_unlock_irq(&zone->lru_lock);
2450 pagevec_release(&pvec);
2452 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2458 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2459 * @zone - zone of which to scan the unevictable list
2461 * Scan @zone's unevictable LRU lists to check for pages that have become
2462 * evictable. Move those that have to @zone's inactive list where they
2463 * become candidates for reclaim, unless shrink_inactive_zone() decides
2464 * to reactivate them. Pages that are still unevictable are rotated
2465 * back onto @zone's unevictable list.
2467 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2468 void scan_zone_unevictable_pages(struct zone *zone)
2470 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2471 unsigned long scan;
2472 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2474 while (nr_to_scan > 0) {
2475 unsigned long batch_size = min(nr_to_scan,
2476 SCAN_UNEVICTABLE_BATCH_SIZE);
2478 spin_lock_irq(&zone->lru_lock);
2479 for (scan = 0; scan < batch_size; scan++) {
2480 struct page *page = lru_to_page(l_unevictable);
2482 if (!trylock_page(page))
2483 continue;
2485 prefetchw_prev_lru_page(page, l_unevictable, flags);
2487 if (likely(PageLRU(page) && PageUnevictable(page)))
2488 check_move_unevictable_page(page, zone);
2490 unlock_page(page);
2492 spin_unlock_irq(&zone->lru_lock);
2494 nr_to_scan -= batch_size;
2500 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2502 * A really big hammer: scan all zones' unevictable LRU lists to check for
2503 * pages that have become evictable. Move those back to the zones'
2504 * inactive list where they become candidates for reclaim.
2505 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2506 * and we add swap to the system. As such, it runs in the context of a task
2507 * that has possibly/probably made some previously unevictable pages
2508 * evictable.
2510 void scan_all_zones_unevictable_pages(void)
2512 struct zone *zone;
2514 for_each_zone(zone) {
2515 scan_zone_unevictable_pages(zone);
2520 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2521 * all nodes' unevictable lists for evictable pages
2523 unsigned long scan_unevictable_pages;
2525 int scan_unevictable_handler(struct ctl_table *table, int write,
2526 struct file *file, void __user *buffer,
2527 size_t *length, loff_t *ppos)
2529 proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
2531 if (write && *(unsigned long *)table->data)
2532 scan_all_zones_unevictable_pages();
2534 scan_unevictable_pages = 0;
2535 return 0;
2539 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2540 * a specified node's per zone unevictable lists for evictable pages.
2543 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2544 struct sysdev_attribute *attr,
2545 char *buf)
2547 return sprintf(buf, "0\n"); /* always zero; should fit... */
2550 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2551 struct sysdev_attribute *attr,
2552 const char *buf, size_t count)
2554 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2555 struct zone *zone;
2556 unsigned long res;
2557 unsigned long req = strict_strtoul(buf, 10, &res);
2559 if (!req)
2560 return 1; /* zero is no-op */
2562 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2563 if (!populated_zone(zone))
2564 continue;
2565 scan_zone_unevictable_pages(zone);
2567 return 1;
2571 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2572 read_scan_unevictable_node,
2573 write_scan_unevictable_node);
2575 int scan_unevictable_register_node(struct node *node)
2577 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2580 void scan_unevictable_unregister_node(struct node *node)
2582 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
2585 #endif