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.
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>
43 #include <asm/tlbflush.h>
44 #include <asm/div64.h>
46 #include <linux/swapops.h>
51 /* Incremented by the number of inactive pages that were scanned */
52 unsigned long nr_scanned;
54 /* This context's GFP mask */
59 /* Can pages be swapped as part of reclaim? */
62 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
63 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
64 * In this context, it doesn't matter that we scan the
65 * whole list at once. */
70 int all_unreclaimable;
74 /* Which cgroup do we reclaim from */
75 struct mem_cgroup *mem_cgroup;
77 /* Pluggable isolate pages callback */
78 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
79 unsigned long *scanned, int order, int mode,
80 struct zone *z, struct mem_cgroup *mem_cont,
81 int active, int file);
84 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
86 #ifdef ARCH_HAS_PREFETCH
87 #define prefetch_prev_lru_page(_page, _base, _field) \
89 if ((_page)->lru.prev != _base) { \
92 prev = lru_to_page(&(_page->lru)); \
93 prefetch(&prev->_field); \
97 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
100 #ifdef ARCH_HAS_PREFETCHW
101 #define prefetchw_prev_lru_page(_page, _base, _field) \
103 if ((_page)->lru.prev != _base) { \
106 prev = lru_to_page(&(_page->lru)); \
107 prefetchw(&prev->_field); \
111 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
115 * From 0 .. 100. Higher means more swappy.
117 int vm_swappiness = 60;
118 long vm_total_pages; /* The total number of pages which the VM controls */
120 static LIST_HEAD(shrinker_list);
121 static DECLARE_RWSEM(shrinker_rwsem);
123 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
124 #define scan_global_lru(sc) (!(sc)->mem_cgroup)
126 #define scan_global_lru(sc) (1)
130 * Add a shrinker callback to be called from the vm
132 void register_shrinker(struct shrinker *shrinker)
135 down_write(&shrinker_rwsem);
136 list_add_tail(&shrinker->list, &shrinker_list);
137 up_write(&shrinker_rwsem);
139 EXPORT_SYMBOL(register_shrinker);
144 void unregister_shrinker(struct shrinker *shrinker)
146 down_write(&shrinker_rwsem);
147 list_del(&shrinker->list);
148 up_write(&shrinker_rwsem);
150 EXPORT_SYMBOL(unregister_shrinker);
152 #define SHRINK_BATCH 128
154 * Call the shrink functions to age shrinkable caches
156 * Here we assume it costs one seek to replace a lru page and that it also
157 * takes a seek to recreate a cache object. With this in mind we age equal
158 * percentages of the lru and ageable caches. This should balance the seeks
159 * generated by these structures.
161 * If the vm encountered mapped pages on the LRU it increase the pressure on
162 * slab to avoid swapping.
164 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
166 * `lru_pages' represents the number of on-LRU pages in all the zones which
167 * are eligible for the caller's allocation attempt. It is used for balancing
168 * slab reclaim versus page reclaim.
170 * Returns the number of slab objects which we shrunk.
172 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
173 unsigned long lru_pages)
175 struct shrinker *shrinker;
176 unsigned long ret = 0;
179 scanned = SWAP_CLUSTER_MAX;
181 if (!down_read_trylock(&shrinker_rwsem))
182 return 1; /* Assume we'll be able to shrink next time */
184 list_for_each_entry(shrinker, &shrinker_list, list) {
185 unsigned long long delta;
186 unsigned long total_scan;
187 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
189 delta = (4 * scanned) / shrinker->seeks;
191 do_div(delta, lru_pages + 1);
192 shrinker->nr += delta;
193 if (shrinker->nr < 0) {
194 printk(KERN_ERR "%s: nr=%ld\n",
195 __func__, shrinker->nr);
196 shrinker->nr = max_pass;
200 * Avoid risking looping forever due to too large nr value:
201 * never try to free more than twice the estimate number of
204 if (shrinker->nr > max_pass * 2)
205 shrinker->nr = max_pass * 2;
207 total_scan = shrinker->nr;
210 while (total_scan >= SHRINK_BATCH) {
211 long this_scan = SHRINK_BATCH;
215 nr_before = (*shrinker->shrink)(0, gfp_mask);
216 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
217 if (shrink_ret == -1)
219 if (shrink_ret < nr_before)
220 ret += nr_before - shrink_ret;
221 count_vm_events(SLABS_SCANNED, this_scan);
222 total_scan -= this_scan;
227 shrinker->nr += total_scan;
229 up_read(&shrinker_rwsem);
233 /* Called without lock on whether page is mapped, so answer is unstable */
234 static inline int page_mapping_inuse(struct page *page)
236 struct address_space *mapping;
238 /* Page is in somebody's page tables. */
239 if (page_mapped(page))
242 /* Be more reluctant to reclaim swapcache than pagecache */
243 if (PageSwapCache(page))
246 mapping = page_mapping(page);
250 /* File is mmap'd by somebody? */
251 return mapping_mapped(mapping);
254 static inline int is_page_cache_freeable(struct page *page)
256 return page_count(page) - !!PagePrivate(page) == 2;
259 static int may_write_to_queue(struct backing_dev_info *bdi)
261 if (current->flags & PF_SWAPWRITE)
263 if (!bdi_write_congested(bdi))
265 if (bdi == current->backing_dev_info)
271 * We detected a synchronous write error writing a page out. Probably
272 * -ENOSPC. We need to propagate that into the address_space for a subsequent
273 * fsync(), msync() or close().
275 * The tricky part is that after writepage we cannot touch the mapping: nothing
276 * prevents it from being freed up. But we have a ref on the page and once
277 * that page is locked, the mapping is pinned.
279 * We're allowed to run sleeping lock_page() here because we know the caller has
282 static void handle_write_error(struct address_space *mapping,
283 struct page *page, int error)
286 if (page_mapping(page) == mapping)
287 mapping_set_error(mapping, error);
291 /* Request for sync pageout. */
297 /* possible outcome of pageout() */
299 /* failed to write page out, page is locked */
301 /* move page to the active list, page is locked */
303 /* page has been sent to the disk successfully, page is unlocked */
305 /* page is clean and locked */
310 * pageout is called by shrink_page_list() for each dirty page.
311 * Calls ->writepage().
313 static pageout_t pageout(struct page *page, struct address_space *mapping,
314 enum pageout_io sync_writeback)
317 * If the page is dirty, only perform writeback if that write
318 * will be non-blocking. To prevent this allocation from being
319 * stalled by pagecache activity. But note that there may be
320 * stalls if we need to run get_block(). We could test
321 * PagePrivate for that.
323 * If this process is currently in generic_file_write() against
324 * this page's queue, we can perform writeback even if that
327 * If the page is swapcache, write it back even if that would
328 * block, for some throttling. This happens by accident, because
329 * swap_backing_dev_info is bust: it doesn't reflect the
330 * congestion state of the swapdevs. Easy to fix, if needed.
331 * See swapfile.c:page_queue_congested().
333 if (!is_page_cache_freeable(page))
337 * Some data journaling orphaned pages can have
338 * page->mapping == NULL while being dirty with clean buffers.
340 if (PagePrivate(page)) {
341 if (try_to_free_buffers(page)) {
342 ClearPageDirty(page);
343 printk("%s: orphaned page\n", __func__);
349 if (mapping->a_ops->writepage == NULL)
350 return PAGE_ACTIVATE;
351 if (!may_write_to_queue(mapping->backing_dev_info))
354 if (clear_page_dirty_for_io(page)) {
356 struct writeback_control wbc = {
357 .sync_mode = WB_SYNC_NONE,
358 .nr_to_write = SWAP_CLUSTER_MAX,
360 .range_end = LLONG_MAX,
365 SetPageReclaim(page);
366 res = mapping->a_ops->writepage(page, &wbc);
368 handle_write_error(mapping, page, res);
369 if (res == AOP_WRITEPAGE_ACTIVATE) {
370 ClearPageReclaim(page);
371 return PAGE_ACTIVATE;
375 * Wait on writeback if requested to. This happens when
376 * direct reclaiming a large contiguous area and the
377 * first attempt to free a range of pages fails.
379 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
380 wait_on_page_writeback(page);
382 if (!PageWriteback(page)) {
383 /* synchronous write or broken a_ops? */
384 ClearPageReclaim(page);
386 inc_zone_page_state(page, NR_VMSCAN_WRITE);
394 * Same as remove_mapping, but if the page is removed from the mapping, it
395 * gets returned with a refcount of 0.
397 static int __remove_mapping(struct address_space *mapping, struct page *page)
399 BUG_ON(!PageLocked(page));
400 BUG_ON(mapping != page_mapping(page));
402 spin_lock_irq(&mapping->tree_lock);
404 * The non racy check for a busy page.
406 * Must be careful with the order of the tests. When someone has
407 * a ref to the page, it may be possible that they dirty it then
408 * drop the reference. So if PageDirty is tested before page_count
409 * here, then the following race may occur:
411 * get_user_pages(&page);
412 * [user mapping goes away]
414 * !PageDirty(page) [good]
415 * SetPageDirty(page);
417 * !page_count(page) [good, discard it]
419 * [oops, our write_to data is lost]
421 * Reversing the order of the tests ensures such a situation cannot
422 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
423 * load is not satisfied before that of page->_count.
425 * Note that if SetPageDirty is always performed via set_page_dirty,
426 * and thus under tree_lock, then this ordering is not required.
428 if (!page_freeze_refs(page, 2))
430 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
431 if (unlikely(PageDirty(page))) {
432 page_unfreeze_refs(page, 2);
436 if (PageSwapCache(page)) {
437 swp_entry_t swap = { .val = page_private(page) };
438 __delete_from_swap_cache(page);
439 spin_unlock_irq(&mapping->tree_lock);
442 __remove_from_page_cache(page);
443 spin_unlock_irq(&mapping->tree_lock);
449 spin_unlock_irq(&mapping->tree_lock);
454 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
455 * someone else has a ref on the page, abort and return 0. If it was
456 * successfully detached, return 1. Assumes the caller has a single ref on
459 int remove_mapping(struct address_space *mapping, struct page *page)
461 if (__remove_mapping(mapping, page)) {
463 * Unfreezing the refcount with 1 rather than 2 effectively
464 * drops the pagecache ref for us without requiring another
467 page_unfreeze_refs(page, 1);
474 * putback_lru_page - put previously isolated page onto appropriate LRU list
475 * @page: page to be put back to appropriate lru list
477 * Add previously isolated @page to appropriate LRU list.
478 * Page may still be unevictable for other reasons.
480 * lru_lock must not be held, interrupts must be enabled.
482 #ifdef CONFIG_UNEVICTABLE_LRU
483 void putback_lru_page(struct page *page)
486 int active = !!TestClearPageActive(page);
487 int was_unevictable = PageUnevictable(page);
489 VM_BUG_ON(PageLRU(page));
492 ClearPageUnevictable(page);
494 if (page_evictable(page, NULL)) {
496 * For evictable pages, we can use the cache.
497 * In event of a race, worst case is we end up with an
498 * unevictable page on [in]active list.
499 * We know how to handle that.
501 lru = active + page_is_file_cache(page);
502 lru_cache_add_lru(page, lru);
505 * Put unevictable pages directly on zone's unevictable
508 lru = LRU_UNEVICTABLE;
509 add_page_to_unevictable_list(page);
511 mem_cgroup_move_lists(page, lru);
514 * page's status can change while we move it among lru. If an evictable
515 * page is on unevictable list, it never be freed. To avoid that,
516 * check after we added it to the list, again.
518 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
519 if (!isolate_lru_page(page)) {
523 /* This means someone else dropped this page from LRU
524 * So, it will be freed or putback to LRU again. There is
525 * nothing to do here.
529 if (was_unevictable && lru != LRU_UNEVICTABLE)
530 count_vm_event(UNEVICTABLE_PGRESCUED);
531 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
532 count_vm_event(UNEVICTABLE_PGCULLED);
534 put_page(page); /* drop ref from isolate */
537 #else /* CONFIG_UNEVICTABLE_LRU */
539 void putback_lru_page(struct page *page)
542 VM_BUG_ON(PageLRU(page));
544 lru = !!TestClearPageActive(page) + page_is_file_cache(page);
545 lru_cache_add_lru(page, lru);
546 mem_cgroup_move_lists(page, lru);
549 #endif /* CONFIG_UNEVICTABLE_LRU */
553 * shrink_page_list() returns the number of reclaimed pages
555 static unsigned long shrink_page_list(struct list_head *page_list,
556 struct scan_control *sc,
557 enum pageout_io sync_writeback)
559 LIST_HEAD(ret_pages);
560 struct pagevec freed_pvec;
562 unsigned long nr_reclaimed = 0;
566 pagevec_init(&freed_pvec, 1);
567 while (!list_empty(page_list)) {
568 struct address_space *mapping;
575 page = lru_to_page(page_list);
576 list_del(&page->lru);
578 if (!trylock_page(page))
581 VM_BUG_ON(PageActive(page));
585 if (unlikely(!page_evictable(page, NULL)))
588 if (!sc->may_swap && page_mapped(page))
591 /* Double the slab pressure for mapped and swapcache pages */
592 if (page_mapped(page) || PageSwapCache(page))
595 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
596 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
598 if (PageWriteback(page)) {
600 * Synchronous reclaim is performed in two passes,
601 * first an asynchronous pass over the list to
602 * start parallel writeback, and a second synchronous
603 * pass to wait for the IO to complete. Wait here
604 * for any page for which writeback has already
607 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
608 wait_on_page_writeback(page);
613 referenced = page_referenced(page, 1, sc->mem_cgroup);
614 /* In active use or really unfreeable? Activate it. */
615 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
616 referenced && page_mapping_inuse(page))
617 goto activate_locked;
621 * Anonymous process memory has backing store?
622 * Try to allocate it some swap space here.
624 if (PageAnon(page) && !PageSwapCache(page)) {
625 switch (try_to_munlock(page)) {
626 case SWAP_FAIL: /* shouldn't happen */
632 ; /* fall thru'; add to swap cache */
634 if (!add_to_swap(page, GFP_ATOMIC))
635 goto activate_locked;
637 #endif /* CONFIG_SWAP */
639 mapping = page_mapping(page);
642 * The page is mapped into the page tables of one or more
643 * processes. Try to unmap it here.
645 if (page_mapped(page) && mapping) {
646 switch (try_to_unmap(page, 0)) {
648 goto activate_locked;
654 ; /* try to free the page below */
658 if (PageDirty(page)) {
659 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
663 if (!sc->may_writepage)
666 /* Page is dirty, try to write it out here */
667 switch (pageout(page, mapping, sync_writeback)) {
671 goto activate_locked;
673 if (PageWriteback(page) || PageDirty(page))
676 * A synchronous write - probably a ramdisk. Go
677 * ahead and try to reclaim the page.
679 if (!trylock_page(page))
681 if (PageDirty(page) || PageWriteback(page))
683 mapping = page_mapping(page);
685 ; /* try to free the page below */
690 * If the page has buffers, try to free the buffer mappings
691 * associated with this page. If we succeed we try to free
694 * We do this even if the page is PageDirty().
695 * try_to_release_page() does not perform I/O, but it is
696 * possible for a page to have PageDirty set, but it is actually
697 * clean (all its buffers are clean). This happens if the
698 * buffers were written out directly, with submit_bh(). ext3
699 * will do this, as well as the blockdev mapping.
700 * try_to_release_page() will discover that cleanness and will
701 * drop the buffers and mark the page clean - it can be freed.
703 * Rarely, pages can have buffers and no ->mapping. These are
704 * the pages which were not successfully invalidated in
705 * truncate_complete_page(). We try to drop those buffers here
706 * and if that worked, and the page is no longer mapped into
707 * process address space (page_count == 1) it can be freed.
708 * Otherwise, leave the page on the LRU so it is swappable.
710 if (PagePrivate(page)) {
711 if (!try_to_release_page(page, sc->gfp_mask))
712 goto activate_locked;
713 if (!mapping && page_count(page) == 1) {
715 if (put_page_testzero(page))
719 * rare race with speculative reference.
720 * the speculative reference will free
721 * this page shortly, so we may
722 * increment nr_reclaimed here (and
723 * leave it off the LRU).
731 if (!mapping || !__remove_mapping(mapping, page))
737 if (!pagevec_add(&freed_pvec, page)) {
738 __pagevec_free(&freed_pvec);
739 pagevec_reinit(&freed_pvec);
745 putback_lru_page(page);
749 /* Not a candidate for swapping, so reclaim swap space. */
750 if (PageSwapCache(page) && vm_swap_full())
751 remove_exclusive_swap_page_ref(page);
752 VM_BUG_ON(PageActive(page));
758 list_add(&page->lru, &ret_pages);
759 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
761 list_splice(&ret_pages, page_list);
762 if (pagevec_count(&freed_pvec))
763 __pagevec_free(&freed_pvec);
764 count_vm_events(PGACTIVATE, pgactivate);
768 /* LRU Isolation modes. */
769 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
770 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
771 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
774 * Attempt to remove the specified page from its LRU. Only take this page
775 * if it is of the appropriate PageActive status. Pages which are being
776 * freed elsewhere are also ignored.
778 * page: page to consider
779 * mode: one of the LRU isolation modes defined above
781 * returns 0 on success, -ve errno on failure.
783 int __isolate_lru_page(struct page *page, int mode, int file)
787 /* Only take pages on the LRU. */
792 * When checking the active state, we need to be sure we are
793 * dealing with comparible boolean values. Take the logical not
796 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
799 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
803 * When this function is being called for lumpy reclaim, we
804 * initially look into all LRU pages, active, inactive and
805 * unevictable; only give shrink_page_list evictable pages.
807 if (PageUnevictable(page))
811 if (likely(get_page_unless_zero(page))) {
813 * Be careful not to clear PageLRU until after we're
814 * sure the page is not being freed elsewhere -- the
815 * page release code relies on it.
825 * zone->lru_lock is heavily contended. Some of the functions that
826 * shrink the lists perform better by taking out a batch of pages
827 * and working on them outside the LRU lock.
829 * For pagecache intensive workloads, this function is the hottest
830 * spot in the kernel (apart from copy_*_user functions).
832 * Appropriate locks must be held before calling this function.
834 * @nr_to_scan: The number of pages to look through on the list.
835 * @src: The LRU list to pull pages off.
836 * @dst: The temp list to put pages on to.
837 * @scanned: The number of pages that were scanned.
838 * @order: The caller's attempted allocation order
839 * @mode: One of the LRU isolation modes
840 * @file: True [1] if isolating file [!anon] pages
842 * returns how many pages were moved onto *@dst.
844 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
845 struct list_head *src, struct list_head *dst,
846 unsigned long *scanned, int order, int mode, int file)
848 unsigned long nr_taken = 0;
851 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
854 unsigned long end_pfn;
855 unsigned long page_pfn;
858 page = lru_to_page(src);
859 prefetchw_prev_lru_page(page, src, flags);
861 VM_BUG_ON(!PageLRU(page));
863 switch (__isolate_lru_page(page, mode, file)) {
865 list_move(&page->lru, dst);
870 /* else it is being freed elsewhere */
871 list_move(&page->lru, src);
882 * Attempt to take all pages in the order aligned region
883 * surrounding the tag page. Only take those pages of
884 * the same active state as that tag page. We may safely
885 * round the target page pfn down to the requested order
886 * as the mem_map is guarenteed valid out to MAX_ORDER,
887 * where that page is in a different zone we will detect
888 * it from its zone id and abort this block scan.
890 zone_id = page_zone_id(page);
891 page_pfn = page_to_pfn(page);
892 pfn = page_pfn & ~((1 << order) - 1);
893 end_pfn = pfn + (1 << order);
894 for (; pfn < end_pfn; pfn++) {
895 struct page *cursor_page;
897 /* The target page is in the block, ignore it. */
898 if (unlikely(pfn == page_pfn))
901 /* Avoid holes within the zone. */
902 if (unlikely(!pfn_valid_within(pfn)))
905 cursor_page = pfn_to_page(pfn);
907 /* Check that we have not crossed a zone boundary. */
908 if (unlikely(page_zone_id(cursor_page) != zone_id))
910 switch (__isolate_lru_page(cursor_page, mode, file)) {
912 list_move(&cursor_page->lru, dst);
918 /* else it is being freed elsewhere */
919 list_move(&cursor_page->lru, src);
921 break; /* ! on LRU or wrong list */
930 static unsigned long isolate_pages_global(unsigned long nr,
931 struct list_head *dst,
932 unsigned long *scanned, int order,
933 int mode, struct zone *z,
934 struct mem_cgroup *mem_cont,
935 int active, int file)
942 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
947 * clear_active_flags() is a helper for shrink_active_list(), clearing
948 * any active bits from the pages in the list.
950 static unsigned long clear_active_flags(struct list_head *page_list,
957 list_for_each_entry(page, page_list, lru) {
958 lru = page_is_file_cache(page);
959 if (PageActive(page)) {
961 ClearPageActive(page);
971 * isolate_lru_page - tries to isolate a page from its LRU list
972 * @page: page to isolate from its LRU list
974 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
975 * vmstat statistic corresponding to whatever LRU list the page was on.
977 * Returns 0 if the page was removed from an LRU list.
978 * Returns -EBUSY if the page was not on an LRU list.
980 * The returned page will have PageLRU() cleared. If it was found on
981 * the active list, it will have PageActive set. If it was found on
982 * the unevictable list, it will have the PageUnevictable bit set. That flag
983 * may need to be cleared by the caller before letting the page go.
985 * The vmstat statistic corresponding to the list on which the page was
986 * found will be decremented.
989 * (1) Must be called with an elevated refcount on the page. This is a
990 * fundamentnal difference from isolate_lru_pages (which is called
991 * without a stable reference).
992 * (2) the lru_lock must not be held.
993 * (3) interrupts must be enabled.
995 int isolate_lru_page(struct page *page)
1000 struct zone *zone = page_zone(page);
1002 spin_lock_irq(&zone->lru_lock);
1003 if (PageLRU(page) && get_page_unless_zero(page)) {
1004 int lru = page_lru(page);
1008 del_page_from_lru_list(zone, page, lru);
1010 spin_unlock_irq(&zone->lru_lock);
1016 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1017 * of reclaimed pages
1019 static unsigned long shrink_inactive_list(unsigned long max_scan,
1020 struct zone *zone, struct scan_control *sc,
1021 int priority, int file)
1023 LIST_HEAD(page_list);
1024 struct pagevec pvec;
1025 unsigned long nr_scanned = 0;
1026 unsigned long nr_reclaimed = 0;
1028 pagevec_init(&pvec, 1);
1031 spin_lock_irq(&zone->lru_lock);
1034 unsigned long nr_taken;
1035 unsigned long nr_scan;
1036 unsigned long nr_freed;
1037 unsigned long nr_active;
1038 unsigned int count[NR_LRU_LISTS] = { 0, };
1039 int mode = ISOLATE_INACTIVE;
1042 * If we need a large contiguous chunk of memory, or have
1043 * trouble getting a small set of contiguous pages, we
1044 * will reclaim both active and inactive pages.
1046 * We use the same threshold as pageout congestion_wait below.
1048 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1049 mode = ISOLATE_BOTH;
1050 else if (sc->order && priority < DEF_PRIORITY - 2)
1051 mode = ISOLATE_BOTH;
1053 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1054 &page_list, &nr_scan, sc->order, mode,
1055 zone, sc->mem_cgroup, 0, file);
1056 nr_active = clear_active_flags(&page_list, count);
1057 __count_vm_events(PGDEACTIVATE, nr_active);
1059 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1060 -count[LRU_ACTIVE_FILE]);
1061 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1062 -count[LRU_INACTIVE_FILE]);
1063 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1064 -count[LRU_ACTIVE_ANON]);
1065 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1066 -count[LRU_INACTIVE_ANON]);
1068 if (scan_global_lru(sc)) {
1069 zone->pages_scanned += nr_scan;
1070 zone->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1071 zone->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1072 zone->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1073 zone->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1075 spin_unlock_irq(&zone->lru_lock);
1077 nr_scanned += nr_scan;
1078 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1081 * If we are direct reclaiming for contiguous pages and we do
1082 * not reclaim everything in the list, try again and wait
1083 * for IO to complete. This will stall high-order allocations
1084 * but that should be acceptable to the caller
1086 if (nr_freed < nr_taken && !current_is_kswapd() &&
1087 sc->order > PAGE_ALLOC_COSTLY_ORDER) {
1088 congestion_wait(WRITE, HZ/10);
1091 * The attempt at page out may have made some
1092 * of the pages active, mark them inactive again.
1094 nr_active = clear_active_flags(&page_list, count);
1095 count_vm_events(PGDEACTIVATE, nr_active);
1097 nr_freed += shrink_page_list(&page_list, sc,
1101 nr_reclaimed += nr_freed;
1102 local_irq_disable();
1103 if (current_is_kswapd()) {
1104 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
1105 __count_vm_events(KSWAPD_STEAL, nr_freed);
1106 } else if (scan_global_lru(sc))
1107 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1109 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1114 spin_lock(&zone->lru_lock);
1116 * Put back any unfreeable pages.
1118 while (!list_empty(&page_list)) {
1120 page = lru_to_page(&page_list);
1121 VM_BUG_ON(PageLRU(page));
1122 list_del(&page->lru);
1123 if (unlikely(!page_evictable(page, NULL))) {
1124 spin_unlock_irq(&zone->lru_lock);
1125 putback_lru_page(page);
1126 spin_lock_irq(&zone->lru_lock);
1130 lru = page_lru(page);
1131 add_page_to_lru_list(zone, page, lru);
1132 mem_cgroup_move_lists(page, lru);
1133 if (PageActive(page) && scan_global_lru(sc)) {
1134 int file = !!page_is_file_cache(page);
1135 zone->recent_rotated[file]++;
1137 if (!pagevec_add(&pvec, page)) {
1138 spin_unlock_irq(&zone->lru_lock);
1139 __pagevec_release(&pvec);
1140 spin_lock_irq(&zone->lru_lock);
1143 } while (nr_scanned < max_scan);
1144 spin_unlock(&zone->lru_lock);
1147 pagevec_release(&pvec);
1148 return nr_reclaimed;
1152 * We are about to scan this zone at a certain priority level. If that priority
1153 * level is smaller (ie: more urgent) than the previous priority, then note
1154 * that priority level within the zone. This is done so that when the next
1155 * process comes in to scan this zone, it will immediately start out at this
1156 * priority level rather than having to build up its own scanning priority.
1157 * Here, this priority affects only the reclaim-mapped threshold.
1159 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1161 if (priority < zone->prev_priority)
1162 zone->prev_priority = priority;
1165 static inline int zone_is_near_oom(struct zone *zone)
1167 return zone->pages_scanned >= (zone_lru_pages(zone) * 3);
1171 * This moves pages from the active list to the inactive list.
1173 * We move them the other way if the page is referenced by one or more
1174 * processes, from rmap.
1176 * If the pages are mostly unmapped, the processing is fast and it is
1177 * appropriate to hold zone->lru_lock across the whole operation. But if
1178 * the pages are mapped, the processing is slow (page_referenced()) so we
1179 * should drop zone->lru_lock around each page. It's impossible to balance
1180 * this, so instead we remove the pages from the LRU while processing them.
1181 * It is safe to rely on PG_active against the non-LRU pages in here because
1182 * nobody will play with that bit on a non-LRU page.
1184 * The downside is that we have to touch page->_count against each page.
1185 * But we had to alter page->flags anyway.
1189 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1190 struct scan_control *sc, int priority, int file)
1192 unsigned long pgmoved;
1193 int pgdeactivate = 0;
1194 unsigned long pgscanned;
1195 LIST_HEAD(l_hold); /* The pages which were snipped off */
1196 LIST_HEAD(l_inactive);
1198 struct pagevec pvec;
1202 spin_lock_irq(&zone->lru_lock);
1203 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1204 ISOLATE_ACTIVE, zone,
1205 sc->mem_cgroup, 1, file);
1207 * zone->pages_scanned is used for detect zone's oom
1208 * mem_cgroup remembers nr_scan by itself.
1210 if (scan_global_lru(sc)) {
1211 zone->pages_scanned += pgscanned;
1212 zone->recent_scanned[!!file] += pgmoved;
1216 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1218 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
1219 spin_unlock_irq(&zone->lru_lock);
1222 while (!list_empty(&l_hold)) {
1224 page = lru_to_page(&l_hold);
1225 list_del(&page->lru);
1227 if (unlikely(!page_evictable(page, NULL))) {
1228 putback_lru_page(page);
1232 /* page_referenced clears PageReferenced */
1233 if (page_mapping_inuse(page) &&
1234 page_referenced(page, 0, sc->mem_cgroup))
1237 list_add(&page->lru, &l_inactive);
1241 * Count referenced pages from currently used mappings as
1242 * rotated, even though they are moved to the inactive list.
1243 * This helps balance scan pressure between file and anonymous
1244 * pages in get_scan_ratio.
1246 zone->recent_rotated[!!file] += pgmoved;
1249 * Move the pages to the [file or anon] inactive list.
1251 pagevec_init(&pvec, 1);
1254 lru = LRU_BASE + file * LRU_FILE;
1255 spin_lock_irq(&zone->lru_lock);
1256 while (!list_empty(&l_inactive)) {
1257 page = lru_to_page(&l_inactive);
1258 prefetchw_prev_lru_page(page, &l_inactive, flags);
1259 VM_BUG_ON(PageLRU(page));
1261 VM_BUG_ON(!PageActive(page));
1262 ClearPageActive(page);
1264 list_move(&page->lru, &zone->lru[lru].list);
1265 mem_cgroup_move_lists(page, lru);
1267 if (!pagevec_add(&pvec, page)) {
1268 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1269 spin_unlock_irq(&zone->lru_lock);
1270 pgdeactivate += pgmoved;
1272 if (buffer_heads_over_limit)
1273 pagevec_strip(&pvec);
1274 __pagevec_release(&pvec);
1275 spin_lock_irq(&zone->lru_lock);
1278 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1279 pgdeactivate += pgmoved;
1280 if (buffer_heads_over_limit) {
1281 spin_unlock_irq(&zone->lru_lock);
1282 pagevec_strip(&pvec);
1283 spin_lock_irq(&zone->lru_lock);
1285 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1286 __count_vm_events(PGDEACTIVATE, pgdeactivate);
1287 spin_unlock_irq(&zone->lru_lock);
1289 pagevec_swap_free(&pvec);
1291 pagevec_release(&pvec);
1294 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1295 struct zone *zone, struct scan_control *sc, int priority)
1297 int file = is_file_lru(lru);
1299 if (lru == LRU_ACTIVE_FILE) {
1300 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1304 if (lru == LRU_ACTIVE_ANON &&
1305 (!scan_global_lru(sc) || inactive_anon_is_low(zone))) {
1306 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1309 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1313 * Determine how aggressively the anon and file LRU lists should be
1314 * scanned. The relative value of each set of LRU lists is determined
1315 * by looking at the fraction of the pages scanned we did rotate back
1316 * onto the active list instead of evict.
1318 * percent[0] specifies how much pressure to put on ram/swap backed
1319 * memory, while percent[1] determines pressure on the file LRUs.
1321 static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1322 unsigned long *percent)
1324 unsigned long anon, file, free;
1325 unsigned long anon_prio, file_prio;
1326 unsigned long ap, fp;
1328 anon = zone_page_state(zone, NR_ACTIVE_ANON) +
1329 zone_page_state(zone, NR_INACTIVE_ANON);
1330 file = zone_page_state(zone, NR_ACTIVE_FILE) +
1331 zone_page_state(zone, NR_INACTIVE_FILE);
1332 free = zone_page_state(zone, NR_FREE_PAGES);
1334 /* If we have no swap space, do not bother scanning anon pages. */
1335 if (nr_swap_pages <= 0) {
1341 /* If we have very few page cache pages, force-scan anon pages. */
1342 if (unlikely(file + free <= zone->pages_high)) {
1349 * OK, so we have swap space and a fair amount of page cache
1350 * pages. We use the recently rotated / recently scanned
1351 * ratios to determine how valuable each cache is.
1353 * Because workloads change over time (and to avoid overflow)
1354 * we keep these statistics as a floating average, which ends
1355 * up weighing recent references more than old ones.
1357 * anon in [0], file in [1]
1359 if (unlikely(zone->recent_scanned[0] > anon / 4)) {
1360 spin_lock_irq(&zone->lru_lock);
1361 zone->recent_scanned[0] /= 2;
1362 zone->recent_rotated[0] /= 2;
1363 spin_unlock_irq(&zone->lru_lock);
1366 if (unlikely(zone->recent_scanned[1] > file / 4)) {
1367 spin_lock_irq(&zone->lru_lock);
1368 zone->recent_scanned[1] /= 2;
1369 zone->recent_rotated[1] /= 2;
1370 spin_unlock_irq(&zone->lru_lock);
1374 * With swappiness at 100, anonymous and file have the same priority.
1375 * This scanning priority is essentially the inverse of IO cost.
1377 anon_prio = sc->swappiness;
1378 file_prio = 200 - sc->swappiness;
1381 * anon recent_rotated[0]
1382 * %anon = 100 * ----------- / ----------------- * IO cost
1383 * anon + file rotate_sum
1385 ap = (anon_prio + 1) * (zone->recent_scanned[0] + 1);
1386 ap /= zone->recent_rotated[0] + 1;
1388 fp = (file_prio + 1) * (zone->recent_scanned[1] + 1);
1389 fp /= zone->recent_rotated[1] + 1;
1391 /* Normalize to percentages */
1392 percent[0] = 100 * ap / (ap + fp + 1);
1393 percent[1] = 100 - percent[0];
1398 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1400 static unsigned long shrink_zone(int priority, struct zone *zone,
1401 struct scan_control *sc)
1403 unsigned long nr[NR_LRU_LISTS];
1404 unsigned long nr_to_scan;
1405 unsigned long nr_reclaimed = 0;
1406 unsigned long percent[2]; /* anon @ 0; file @ 1 */
1409 get_scan_ratio(zone, sc, percent);
1411 for_each_evictable_lru(l) {
1412 if (scan_global_lru(sc)) {
1413 int file = is_file_lru(l);
1416 * Add one to nr_to_scan just to make sure that the
1417 * kernel will slowly sift through each list.
1419 scan = zone_page_state(zone, NR_LRU_BASE + l);
1422 scan = (scan * percent[file]) / 100;
1424 zone->lru[l].nr_scan += scan + 1;
1425 nr[l] = zone->lru[l].nr_scan;
1426 if (nr[l] >= sc->swap_cluster_max)
1427 zone->lru[l].nr_scan = 0;
1432 * This reclaim occurs not because zone memory shortage
1433 * but because memory controller hits its limit.
1434 * Don't modify zone reclaim related data.
1436 nr[l] = mem_cgroup_calc_reclaim(sc->mem_cgroup, zone,
1441 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1442 nr[LRU_INACTIVE_FILE]) {
1443 for_each_evictable_lru(l) {
1445 nr_to_scan = min(nr[l],
1446 (unsigned long)sc->swap_cluster_max);
1447 nr[l] -= nr_to_scan;
1449 nr_reclaimed += shrink_list(l, nr_to_scan,
1450 zone, sc, priority);
1456 * Even if we did not try to evict anon pages at all, we want to
1457 * rebalance the anon lru active/inactive ratio.
1459 if (!scan_global_lru(sc) || inactive_anon_is_low(zone))
1460 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1461 else if (!scan_global_lru(sc))
1462 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1464 throttle_vm_writeout(sc->gfp_mask);
1465 return nr_reclaimed;
1469 * This is the direct reclaim path, for page-allocating processes. We only
1470 * try to reclaim pages from zones which will satisfy the caller's allocation
1473 * We reclaim from a zone even if that zone is over pages_high. Because:
1474 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1476 * b) The zones may be over pages_high but they must go *over* pages_high to
1477 * satisfy the `incremental min' zone defense algorithm.
1479 * Returns the number of reclaimed pages.
1481 * If a zone is deemed to be full of pinned pages then just give it a light
1482 * scan then give up on it.
1484 static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
1485 struct scan_control *sc)
1487 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1488 unsigned long nr_reclaimed = 0;
1492 sc->all_unreclaimable = 1;
1493 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1494 if (!populated_zone(zone))
1497 * Take care memory controller reclaiming has small influence
1500 if (scan_global_lru(sc)) {
1501 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1503 note_zone_scanning_priority(zone, priority);
1505 if (zone_is_all_unreclaimable(zone) &&
1506 priority != DEF_PRIORITY)
1507 continue; /* Let kswapd poll it */
1508 sc->all_unreclaimable = 0;
1511 * Ignore cpuset limitation here. We just want to reduce
1512 * # of used pages by us regardless of memory shortage.
1514 sc->all_unreclaimable = 0;
1515 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1519 nr_reclaimed += shrink_zone(priority, zone, sc);
1522 return nr_reclaimed;
1526 * This is the main entry point to direct page reclaim.
1528 * If a full scan of the inactive list fails to free enough memory then we
1529 * are "out of memory" and something needs to be killed.
1531 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1532 * high - the zone may be full of dirty or under-writeback pages, which this
1533 * caller can't do much about. We kick pdflush and take explicit naps in the
1534 * hope that some of these pages can be written. But if the allocating task
1535 * holds filesystem locks which prevent writeout this might not work, and the
1536 * allocation attempt will fail.
1538 * returns: 0, if no pages reclaimed
1539 * else, the number of pages reclaimed
1541 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1542 struct scan_control *sc)
1545 unsigned long ret = 0;
1546 unsigned long total_scanned = 0;
1547 unsigned long nr_reclaimed = 0;
1548 struct reclaim_state *reclaim_state = current->reclaim_state;
1549 unsigned long lru_pages = 0;
1552 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1554 delayacct_freepages_start();
1556 if (scan_global_lru(sc))
1557 count_vm_event(ALLOCSTALL);
1559 * mem_cgroup will not do shrink_slab.
1561 if (scan_global_lru(sc)) {
1562 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1564 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1567 lru_pages += zone_lru_pages(zone);
1571 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1574 disable_swap_token();
1575 nr_reclaimed += shrink_zones(priority, zonelist, sc);
1577 * Don't shrink slabs when reclaiming memory from
1578 * over limit cgroups
1580 if (scan_global_lru(sc)) {
1581 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1582 if (reclaim_state) {
1583 nr_reclaimed += reclaim_state->reclaimed_slab;
1584 reclaim_state->reclaimed_slab = 0;
1587 total_scanned += sc->nr_scanned;
1588 if (nr_reclaimed >= sc->swap_cluster_max) {
1594 * Try to write back as many pages as we just scanned. This
1595 * tends to cause slow streaming writers to write data to the
1596 * disk smoothly, at the dirtying rate, which is nice. But
1597 * that's undesirable in laptop mode, where we *want* lumpy
1598 * writeout. So in laptop mode, write out the whole world.
1600 if (total_scanned > sc->swap_cluster_max +
1601 sc->swap_cluster_max / 2) {
1602 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1603 sc->may_writepage = 1;
1606 /* Take a nap, wait for some writeback to complete */
1607 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1608 congestion_wait(WRITE, HZ/10);
1610 /* top priority shrink_zones still had more to do? don't OOM, then */
1611 if (!sc->all_unreclaimable && scan_global_lru(sc))
1615 * Now that we've scanned all the zones at this priority level, note
1616 * that level within the zone so that the next thread which performs
1617 * scanning of this zone will immediately start out at this priority
1618 * level. This affects only the decision whether or not to bring
1619 * mapped pages onto the inactive list.
1624 if (scan_global_lru(sc)) {
1625 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1627 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1630 zone->prev_priority = priority;
1633 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1635 delayacct_freepages_end();
1640 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1643 struct scan_control sc = {
1644 .gfp_mask = gfp_mask,
1645 .may_writepage = !laptop_mode,
1646 .swap_cluster_max = SWAP_CLUSTER_MAX,
1648 .swappiness = vm_swappiness,
1651 .isolate_pages = isolate_pages_global,
1654 return do_try_to_free_pages(zonelist, &sc);
1657 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1659 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1662 struct scan_control sc = {
1663 .may_writepage = !laptop_mode,
1665 .swap_cluster_max = SWAP_CLUSTER_MAX,
1666 .swappiness = vm_swappiness,
1668 .mem_cgroup = mem_cont,
1669 .isolate_pages = mem_cgroup_isolate_pages,
1671 struct zonelist *zonelist;
1673 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1674 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1675 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1676 return do_try_to_free_pages(zonelist, &sc);
1681 * For kswapd, balance_pgdat() will work across all this node's zones until
1682 * they are all at pages_high.
1684 * Returns the number of pages which were actually freed.
1686 * There is special handling here for zones which are full of pinned pages.
1687 * This can happen if the pages are all mlocked, or if they are all used by
1688 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1689 * What we do is to detect the case where all pages in the zone have been
1690 * scanned twice and there has been zero successful reclaim. Mark the zone as
1691 * dead and from now on, only perform a short scan. Basically we're polling
1692 * the zone for when the problem goes away.
1694 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1695 * zones which have free_pages > pages_high, but once a zone is found to have
1696 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1697 * of the number of free pages in the lower zones. This interoperates with
1698 * the page allocator fallback scheme to ensure that aging of pages is balanced
1701 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1706 unsigned long total_scanned;
1707 unsigned long nr_reclaimed;
1708 struct reclaim_state *reclaim_state = current->reclaim_state;
1709 struct scan_control sc = {
1710 .gfp_mask = GFP_KERNEL,
1712 .swap_cluster_max = SWAP_CLUSTER_MAX,
1713 .swappiness = vm_swappiness,
1716 .isolate_pages = isolate_pages_global,
1719 * temp_priority is used to remember the scanning priority at which
1720 * this zone was successfully refilled to free_pages == pages_high.
1722 int temp_priority[MAX_NR_ZONES];
1727 sc.may_writepage = !laptop_mode;
1728 count_vm_event(PAGEOUTRUN);
1730 for (i = 0; i < pgdat->nr_zones; i++)
1731 temp_priority[i] = DEF_PRIORITY;
1733 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1734 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1735 unsigned long lru_pages = 0;
1737 /* The swap token gets in the way of swapout... */
1739 disable_swap_token();
1744 * Scan in the highmem->dma direction for the highest
1745 * zone which needs scanning
1747 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1748 struct zone *zone = pgdat->node_zones + i;
1750 if (!populated_zone(zone))
1753 if (zone_is_all_unreclaimable(zone) &&
1754 priority != DEF_PRIORITY)
1758 * Do some background aging of the anon list, to give
1759 * pages a chance to be referenced before reclaiming.
1761 if (inactive_anon_is_low(zone))
1762 shrink_active_list(SWAP_CLUSTER_MAX, zone,
1765 if (!zone_watermark_ok(zone, order, zone->pages_high,
1774 for (i = 0; i <= end_zone; i++) {
1775 struct zone *zone = pgdat->node_zones + i;
1777 lru_pages += zone_lru_pages(zone);
1781 * Now scan the zone in the dma->highmem direction, stopping
1782 * at the last zone which needs scanning.
1784 * We do this because the page allocator works in the opposite
1785 * direction. This prevents the page allocator from allocating
1786 * pages behind kswapd's direction of progress, which would
1787 * cause too much scanning of the lower zones.
1789 for (i = 0; i <= end_zone; i++) {
1790 struct zone *zone = pgdat->node_zones + i;
1793 if (!populated_zone(zone))
1796 if (zone_is_all_unreclaimable(zone) &&
1797 priority != DEF_PRIORITY)
1800 if (!zone_watermark_ok(zone, order, zone->pages_high,
1803 temp_priority[i] = priority;
1805 note_zone_scanning_priority(zone, priority);
1807 * We put equal pressure on every zone, unless one
1808 * zone has way too many pages free already.
1810 if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
1812 nr_reclaimed += shrink_zone(priority, zone, &sc);
1813 reclaim_state->reclaimed_slab = 0;
1814 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1816 nr_reclaimed += reclaim_state->reclaimed_slab;
1817 total_scanned += sc.nr_scanned;
1818 if (zone_is_all_unreclaimable(zone))
1820 if (nr_slab == 0 && zone->pages_scanned >=
1821 (zone_lru_pages(zone) * 6))
1823 ZONE_ALL_UNRECLAIMABLE);
1825 * If we've done a decent amount of scanning and
1826 * the reclaim ratio is low, start doing writepage
1827 * even in laptop mode
1829 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1830 total_scanned > nr_reclaimed + nr_reclaimed / 2)
1831 sc.may_writepage = 1;
1834 break; /* kswapd: all done */
1836 * OK, kswapd is getting into trouble. Take a nap, then take
1837 * another pass across the zones.
1839 if (total_scanned && priority < DEF_PRIORITY - 2)
1840 congestion_wait(WRITE, HZ/10);
1843 * We do this so kswapd doesn't build up large priorities for
1844 * example when it is freeing in parallel with allocators. It
1845 * matches the direct reclaim path behaviour in terms of impact
1846 * on zone->*_priority.
1848 if (nr_reclaimed >= SWAP_CLUSTER_MAX)
1853 * Note within each zone the priority level at which this zone was
1854 * brought into a happy state. So that the next thread which scans this
1855 * zone will start out at that priority level.
1857 for (i = 0; i < pgdat->nr_zones; i++) {
1858 struct zone *zone = pgdat->node_zones + i;
1860 zone->prev_priority = temp_priority[i];
1862 if (!all_zones_ok) {
1870 return nr_reclaimed;
1874 * The background pageout daemon, started as a kernel thread
1875 * from the init process.
1877 * This basically trickles out pages so that we have _some_
1878 * free memory available even if there is no other activity
1879 * that frees anything up. This is needed for things like routing
1880 * etc, where we otherwise might have all activity going on in
1881 * asynchronous contexts that cannot page things out.
1883 * If there are applications that are active memory-allocators
1884 * (most normal use), this basically shouldn't matter.
1886 static int kswapd(void *p)
1888 unsigned long order;
1889 pg_data_t *pgdat = (pg_data_t*)p;
1890 struct task_struct *tsk = current;
1892 struct reclaim_state reclaim_state = {
1893 .reclaimed_slab = 0,
1895 node_to_cpumask_ptr(cpumask, pgdat->node_id);
1897 if (!cpus_empty(*cpumask))
1898 set_cpus_allowed_ptr(tsk, cpumask);
1899 current->reclaim_state = &reclaim_state;
1902 * Tell the memory management that we're a "memory allocator",
1903 * and that if we need more memory we should get access to it
1904 * regardless (see "__alloc_pages()"). "kswapd" should
1905 * never get caught in the normal page freeing logic.
1907 * (Kswapd normally doesn't need memory anyway, but sometimes
1908 * you need a small amount of memory in order to be able to
1909 * page out something else, and this flag essentially protects
1910 * us from recursively trying to free more memory as we're
1911 * trying to free the first piece of memory in the first place).
1913 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1918 unsigned long new_order;
1920 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1921 new_order = pgdat->kswapd_max_order;
1922 pgdat->kswapd_max_order = 0;
1923 if (order < new_order) {
1925 * Don't sleep if someone wants a larger 'order'
1930 if (!freezing(current))
1933 order = pgdat->kswapd_max_order;
1935 finish_wait(&pgdat->kswapd_wait, &wait);
1937 if (!try_to_freeze()) {
1938 /* We can speed up thawing tasks if we don't call
1939 * balance_pgdat after returning from the refrigerator
1941 balance_pgdat(pgdat, order);
1948 * A zone is low on free memory, so wake its kswapd task to service it.
1950 void wakeup_kswapd(struct zone *zone, int order)
1954 if (!populated_zone(zone))
1957 pgdat = zone->zone_pgdat;
1958 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
1960 if (pgdat->kswapd_max_order < order)
1961 pgdat->kswapd_max_order = order;
1962 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1964 if (!waitqueue_active(&pgdat->kswapd_wait))
1966 wake_up_interruptible(&pgdat->kswapd_wait);
1969 unsigned long global_lru_pages(void)
1971 return global_page_state(NR_ACTIVE_ANON)
1972 + global_page_state(NR_ACTIVE_FILE)
1973 + global_page_state(NR_INACTIVE_ANON)
1974 + global_page_state(NR_INACTIVE_FILE);
1979 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1980 * from LRU lists system-wide, for given pass and priority, and returns the
1981 * number of reclaimed pages
1983 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1985 static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
1986 int pass, struct scan_control *sc)
1989 unsigned long nr_to_scan, ret = 0;
1992 for_each_zone(zone) {
1994 if (!populated_zone(zone))
1997 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2000 for_each_evictable_lru(l) {
2001 /* For pass = 0, we don't shrink the active list */
2003 (l == LRU_ACTIVE || l == LRU_ACTIVE_FILE))
2006 zone->lru[l].nr_scan +=
2007 (zone_page_state(zone, NR_LRU_BASE + l)
2009 if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
2010 zone->lru[l].nr_scan = 0;
2011 nr_to_scan = min(nr_pages,
2012 zone_page_state(zone,
2014 ret += shrink_list(l, nr_to_scan, zone,
2016 if (ret >= nr_pages)
2026 * Try to free `nr_pages' of memory, system-wide, and return the number of
2029 * Rather than trying to age LRUs the aim is to preserve the overall
2030 * LRU order by reclaiming preferentially
2031 * inactive > active > active referenced > active mapped
2033 unsigned long shrink_all_memory(unsigned long nr_pages)
2035 unsigned long lru_pages, nr_slab;
2036 unsigned long ret = 0;
2038 struct reclaim_state reclaim_state;
2039 struct scan_control sc = {
2040 .gfp_mask = GFP_KERNEL,
2042 .swap_cluster_max = nr_pages,
2044 .swappiness = vm_swappiness,
2045 .isolate_pages = isolate_pages_global,
2048 current->reclaim_state = &reclaim_state;
2050 lru_pages = global_lru_pages();
2051 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2052 /* If slab caches are huge, it's better to hit them first */
2053 while (nr_slab >= lru_pages) {
2054 reclaim_state.reclaimed_slab = 0;
2055 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
2056 if (!reclaim_state.reclaimed_slab)
2059 ret += reclaim_state.reclaimed_slab;
2060 if (ret >= nr_pages)
2063 nr_slab -= reclaim_state.reclaimed_slab;
2067 * We try to shrink LRUs in 5 passes:
2068 * 0 = Reclaim from inactive_list only
2069 * 1 = Reclaim from active list but don't reclaim mapped
2070 * 2 = 2nd pass of type 1
2071 * 3 = Reclaim mapped (normal reclaim)
2072 * 4 = 2nd pass of type 3
2074 for (pass = 0; pass < 5; pass++) {
2077 /* Force reclaiming mapped pages in the passes #3 and #4 */
2080 sc.swappiness = 100;
2083 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2084 unsigned long nr_to_scan = nr_pages - ret;
2087 ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
2088 if (ret >= nr_pages)
2091 reclaim_state.reclaimed_slab = 0;
2092 shrink_slab(sc.nr_scanned, sc.gfp_mask,
2093 global_lru_pages());
2094 ret += reclaim_state.reclaimed_slab;
2095 if (ret >= nr_pages)
2098 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2099 congestion_wait(WRITE, HZ / 10);
2104 * If ret = 0, we could not shrink LRUs, but there may be something
2109 reclaim_state.reclaimed_slab = 0;
2110 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2111 ret += reclaim_state.reclaimed_slab;
2112 } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
2116 current->reclaim_state = NULL;
2122 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2123 not required for correctness. So if the last cpu in a node goes
2124 away, we get changed to run anywhere: as the first one comes back,
2125 restore their cpu bindings. */
2126 static int __devinit cpu_callback(struct notifier_block *nfb,
2127 unsigned long action, void *hcpu)
2131 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2132 for_each_node_state(nid, N_HIGH_MEMORY) {
2133 pg_data_t *pgdat = NODE_DATA(nid);
2134 node_to_cpumask_ptr(mask, pgdat->node_id);
2136 if (any_online_cpu(*mask) < nr_cpu_ids)
2137 /* One of our CPUs online: restore mask */
2138 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2145 * This kswapd start function will be called by init and node-hot-add.
2146 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2148 int kswapd_run(int nid)
2150 pg_data_t *pgdat = NODE_DATA(nid);
2156 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2157 if (IS_ERR(pgdat->kswapd)) {
2158 /* failure at boot is fatal */
2159 BUG_ON(system_state == SYSTEM_BOOTING);
2160 printk("Failed to start kswapd on node %d\n",nid);
2166 static int __init kswapd_init(void)
2171 for_each_node_state(nid, N_HIGH_MEMORY)
2173 hotcpu_notifier(cpu_callback, 0);
2177 module_init(kswapd_init)
2183 * If non-zero call zone_reclaim when the number of free pages falls below
2186 int zone_reclaim_mode __read_mostly;
2188 #define RECLAIM_OFF 0
2189 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2190 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2191 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2194 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2195 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2198 #define ZONE_RECLAIM_PRIORITY 4
2201 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2204 int sysctl_min_unmapped_ratio = 1;
2207 * If the number of slab pages in a zone grows beyond this percentage then
2208 * slab reclaim needs to occur.
2210 int sysctl_min_slab_ratio = 5;
2213 * Try to free up some pages from this zone through reclaim.
2215 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2217 /* Minimum pages needed in order to stay on node */
2218 const unsigned long nr_pages = 1 << order;
2219 struct task_struct *p = current;
2220 struct reclaim_state reclaim_state;
2222 unsigned long nr_reclaimed = 0;
2223 struct scan_control sc = {
2224 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2225 .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2226 .swap_cluster_max = max_t(unsigned long, nr_pages,
2228 .gfp_mask = gfp_mask,
2229 .swappiness = vm_swappiness,
2230 .isolate_pages = isolate_pages_global,
2232 unsigned long slab_reclaimable;
2234 disable_swap_token();
2237 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2238 * and we also need to be able to write out pages for RECLAIM_WRITE
2241 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2242 reclaim_state.reclaimed_slab = 0;
2243 p->reclaim_state = &reclaim_state;
2245 if (zone_page_state(zone, NR_FILE_PAGES) -
2246 zone_page_state(zone, NR_FILE_MAPPED) >
2247 zone->min_unmapped_pages) {
2249 * Free memory by calling shrink zone with increasing
2250 * priorities until we have enough memory freed.
2252 priority = ZONE_RECLAIM_PRIORITY;
2254 note_zone_scanning_priority(zone, priority);
2255 nr_reclaimed += shrink_zone(priority, zone, &sc);
2257 } while (priority >= 0 && nr_reclaimed < nr_pages);
2260 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2261 if (slab_reclaimable > zone->min_slab_pages) {
2263 * shrink_slab() does not currently allow us to determine how
2264 * many pages were freed in this zone. So we take the current
2265 * number of slab pages and shake the slab until it is reduced
2266 * by the same nr_pages that we used for reclaiming unmapped
2269 * Note that shrink_slab will free memory on all zones and may
2272 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2273 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2274 slab_reclaimable - nr_pages)
2278 * Update nr_reclaimed by the number of slab pages we
2279 * reclaimed from this zone.
2281 nr_reclaimed += slab_reclaimable -
2282 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2285 p->reclaim_state = NULL;
2286 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2287 return nr_reclaimed >= nr_pages;
2290 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2296 * Zone reclaim reclaims unmapped file backed pages and
2297 * slab pages if we are over the defined limits.
2299 * A small portion of unmapped file backed pages is needed for
2300 * file I/O otherwise pages read by file I/O will be immediately
2301 * thrown out if the zone is overallocated. So we do not reclaim
2302 * if less than a specified percentage of the zone is used by
2303 * unmapped file backed pages.
2305 if (zone_page_state(zone, NR_FILE_PAGES) -
2306 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
2307 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
2308 <= zone->min_slab_pages)
2311 if (zone_is_all_unreclaimable(zone))
2315 * Do not scan if the allocation should not be delayed.
2317 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2321 * Only run zone reclaim on the local zone or on zones that do not
2322 * have associated processors. This will favor the local processor
2323 * over remote processors and spread off node memory allocations
2324 * as wide as possible.
2326 node_id = zone_to_nid(zone);
2327 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2330 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2332 ret = __zone_reclaim(zone, gfp_mask, order);
2333 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2339 #ifdef CONFIG_UNEVICTABLE_LRU
2341 * page_evictable - test whether a page is evictable
2342 * @page: the page to test
2343 * @vma: the VMA in which the page is or will be mapped, may be NULL
2345 * Test whether page is evictable--i.e., should be placed on active/inactive
2346 * lists vs unevictable list. The vma argument is !NULL when called from the
2347 * fault path to determine how to instantate a new page.
2349 * Reasons page might not be evictable:
2350 * (1) page's mapping marked unevictable
2351 * (2) page is part of an mlocked VMA
2354 int page_evictable(struct page *page, struct vm_area_struct *vma)
2357 if (mapping_unevictable(page_mapping(page)))
2360 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2367 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2368 * @page: page to check evictability and move to appropriate lru list
2369 * @zone: zone page is in
2371 * Checks a page for evictability and moves the page to the appropriate
2374 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2375 * have PageUnevictable set.
2377 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2379 VM_BUG_ON(PageActive(page));
2382 ClearPageUnevictable(page);
2383 if (page_evictable(page, NULL)) {
2384 enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
2385 __dec_zone_state(zone, NR_UNEVICTABLE);
2386 list_move(&page->lru, &zone->lru[l].list);
2387 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2388 __count_vm_event(UNEVICTABLE_PGRESCUED);
2391 * rotate unevictable list
2393 SetPageUnevictable(page);
2394 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2395 if (page_evictable(page, NULL))
2401 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2402 * @mapping: struct address_space to scan for evictable pages
2404 * Scan all pages in mapping. Check unevictable pages for
2405 * evictability and move them to the appropriate zone lru list.
2407 void scan_mapping_unevictable_pages(struct address_space *mapping)
2410 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2413 struct pagevec pvec;
2415 if (mapping->nrpages == 0)
2418 pagevec_init(&pvec, 0);
2419 while (next < end &&
2420 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2426 for (i = 0; i < pagevec_count(&pvec); i++) {
2427 struct page *page = pvec.pages[i];
2428 pgoff_t page_index = page->index;
2429 struct zone *pagezone = page_zone(page);
2432 if (page_index > next)
2436 if (pagezone != zone) {
2438 spin_unlock_irq(&zone->lru_lock);
2440 spin_lock_irq(&zone->lru_lock);
2443 if (PageLRU(page) && PageUnevictable(page))
2444 check_move_unevictable_page(page, zone);
2447 spin_unlock_irq(&zone->lru_lock);
2448 pagevec_release(&pvec);
2450 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);