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/gfp.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>
51 #define CREATE_TRACE_POINTS
52 #include <trace/events/vmscan.h>
55 /* Incremented by the number of inactive pages that were scanned */
56 unsigned long nr_scanned;
58 /* Number of pages freed so far during a call to shrink_zones() */
59 unsigned long nr_reclaimed;
61 /* How many pages shrink_list() should reclaim */
62 unsigned long nr_to_reclaim;
64 unsigned long hibernation_mode;
66 /* This context's GFP mask */
71 /* Can mapped pages be reclaimed? */
74 /* Can pages be swapped as part of reclaim? */
82 * Intend to reclaim enough contenious memory rather than to reclaim
83 * enough amount memory. I.e, it's the mode for high order allocation.
85 bool lumpy_reclaim_mode;
87 /* Which cgroup do we reclaim from */
88 struct mem_cgroup *mem_cgroup;
91 * Nodemask of nodes allowed by the caller. If NULL, all nodes
97 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
99 #ifdef ARCH_HAS_PREFETCH
100 #define prefetch_prev_lru_page(_page, _base, _field) \
102 if ((_page)->lru.prev != _base) { \
105 prev = lru_to_page(&(_page->lru)); \
106 prefetch(&prev->_field); \
110 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
113 #ifdef ARCH_HAS_PREFETCHW
114 #define prefetchw_prev_lru_page(_page, _base, _field) \
116 if ((_page)->lru.prev != _base) { \
119 prev = lru_to_page(&(_page->lru)); \
120 prefetchw(&prev->_field); \
124 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
128 * From 0 .. 100. Higher means more swappy.
130 int vm_swappiness = 60;
131 long vm_total_pages; /* The total number of pages which the VM controls */
133 static LIST_HEAD(shrinker_list);
134 static DECLARE_RWSEM(shrinker_rwsem);
136 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
137 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
139 #define scanning_global_lru(sc) (1)
142 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
143 struct scan_control *sc)
145 if (!scanning_global_lru(sc))
146 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
148 return &zone->reclaim_stat;
151 static unsigned long zone_nr_lru_pages(struct zone *zone,
152 struct scan_control *sc, enum lru_list lru)
154 if (!scanning_global_lru(sc))
155 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
157 return zone_page_state(zone, NR_LRU_BASE + lru);
162 * Add a shrinker callback to be called from the vm
164 void register_shrinker(struct shrinker *shrinker)
167 down_write(&shrinker_rwsem);
168 list_add_tail(&shrinker->list, &shrinker_list);
169 up_write(&shrinker_rwsem);
171 EXPORT_SYMBOL(register_shrinker);
176 void unregister_shrinker(struct shrinker *shrinker)
178 down_write(&shrinker_rwsem);
179 list_del(&shrinker->list);
180 up_write(&shrinker_rwsem);
182 EXPORT_SYMBOL(unregister_shrinker);
184 #define SHRINK_BATCH 128
186 * Call the shrink functions to age shrinkable caches
188 * Here we assume it costs one seek to replace a lru page and that it also
189 * takes a seek to recreate a cache object. With this in mind we age equal
190 * percentages of the lru and ageable caches. This should balance the seeks
191 * generated by these structures.
193 * If the vm encountered mapped pages on the LRU it increase the pressure on
194 * slab to avoid swapping.
196 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
198 * `lru_pages' represents the number of on-LRU pages in all the zones which
199 * are eligible for the caller's allocation attempt. It is used for balancing
200 * slab reclaim versus page reclaim.
202 * Returns the number of slab objects which we shrunk.
204 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
205 unsigned long lru_pages)
207 struct shrinker *shrinker;
208 unsigned long ret = 0;
211 scanned = SWAP_CLUSTER_MAX;
213 if (!down_read_trylock(&shrinker_rwsem))
214 return 1; /* Assume we'll be able to shrink next time */
216 list_for_each_entry(shrinker, &shrinker_list, list) {
217 unsigned long long delta;
218 unsigned long total_scan;
219 unsigned long max_pass;
221 max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask);
222 delta = (4 * scanned) / shrinker->seeks;
224 do_div(delta, lru_pages + 1);
225 shrinker->nr += delta;
226 if (shrinker->nr < 0) {
227 printk(KERN_ERR "shrink_slab: %pF negative objects to "
229 shrinker->shrink, shrinker->nr);
230 shrinker->nr = max_pass;
234 * Avoid risking looping forever due to too large nr value:
235 * never try to free more than twice the estimate number of
238 if (shrinker->nr > max_pass * 2)
239 shrinker->nr = max_pass * 2;
241 total_scan = shrinker->nr;
244 while (total_scan >= SHRINK_BATCH) {
245 long this_scan = SHRINK_BATCH;
249 nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask);
250 shrink_ret = (*shrinker->shrink)(shrinker, this_scan,
252 if (shrink_ret == -1)
254 if (shrink_ret < nr_before)
255 ret += nr_before - shrink_ret;
256 count_vm_events(SLABS_SCANNED, this_scan);
257 total_scan -= this_scan;
262 shrinker->nr += total_scan;
264 up_read(&shrinker_rwsem);
268 static inline int is_page_cache_freeable(struct page *page)
271 * A freeable page cache page is referenced only by the caller
272 * that isolated the page, the page cache radix tree and
273 * optional buffer heads at page->private.
275 return page_count(page) - page_has_private(page) == 2;
278 static int may_write_to_queue(struct backing_dev_info *bdi)
280 if (current->flags & PF_SWAPWRITE)
282 if (!bdi_write_congested(bdi))
284 if (bdi == current->backing_dev_info)
290 * We detected a synchronous write error writing a page out. Probably
291 * -ENOSPC. We need to propagate that into the address_space for a subsequent
292 * fsync(), msync() or close().
294 * The tricky part is that after writepage we cannot touch the mapping: nothing
295 * prevents it from being freed up. But we have a ref on the page and once
296 * that page is locked, the mapping is pinned.
298 * We're allowed to run sleeping lock_page() here because we know the caller has
301 static void handle_write_error(struct address_space *mapping,
302 struct page *page, int error)
304 lock_page_nosync(page);
305 if (page_mapping(page) == mapping)
306 mapping_set_error(mapping, error);
310 /* Request for sync pageout. */
316 /* possible outcome of pageout() */
318 /* failed to write page out, page is locked */
320 /* move page to the active list, page is locked */
322 /* page has been sent to the disk successfully, page is unlocked */
324 /* page is clean and locked */
329 * pageout is called by shrink_page_list() for each dirty page.
330 * Calls ->writepage().
332 static pageout_t pageout(struct page *page, struct address_space *mapping,
333 enum pageout_io sync_writeback)
336 * If the page is dirty, only perform writeback if that write
337 * will be non-blocking. To prevent this allocation from being
338 * stalled by pagecache activity. But note that there may be
339 * stalls if we need to run get_block(). We could test
340 * PagePrivate for that.
342 * If this process is currently in __generic_file_aio_write() against
343 * this page's queue, we can perform writeback even if that
346 * If the page is swapcache, write it back even if that would
347 * block, for some throttling. This happens by accident, because
348 * swap_backing_dev_info is bust: it doesn't reflect the
349 * congestion state of the swapdevs. Easy to fix, if needed.
351 if (!is_page_cache_freeable(page))
355 * Some data journaling orphaned pages can have
356 * page->mapping == NULL while being dirty with clean buffers.
358 if (page_has_private(page)) {
359 if (try_to_free_buffers(page)) {
360 ClearPageDirty(page);
361 printk("%s: orphaned page\n", __func__);
367 if (mapping->a_ops->writepage == NULL)
368 return PAGE_ACTIVATE;
369 if (!may_write_to_queue(mapping->backing_dev_info))
372 if (clear_page_dirty_for_io(page)) {
374 struct writeback_control wbc = {
375 .sync_mode = WB_SYNC_NONE,
376 .nr_to_write = SWAP_CLUSTER_MAX,
378 .range_end = LLONG_MAX,
383 SetPageReclaim(page);
384 res = mapping->a_ops->writepage(page, &wbc);
386 handle_write_error(mapping, page, res);
387 if (res == AOP_WRITEPAGE_ACTIVATE) {
388 ClearPageReclaim(page);
389 return PAGE_ACTIVATE;
393 * Wait on writeback if requested to. This happens when
394 * direct reclaiming a large contiguous area and the
395 * first attempt to free a range of pages fails.
397 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
398 wait_on_page_writeback(page);
400 if (!PageWriteback(page)) {
401 /* synchronous write or broken a_ops? */
402 ClearPageReclaim(page);
404 inc_zone_page_state(page, NR_VMSCAN_WRITE);
412 * Same as remove_mapping, but if the page is removed from the mapping, it
413 * gets returned with a refcount of 0.
415 static int __remove_mapping(struct address_space *mapping, struct page *page)
417 BUG_ON(!PageLocked(page));
418 BUG_ON(mapping != page_mapping(page));
420 spin_lock_irq(&mapping->tree_lock);
422 * The non racy check for a busy page.
424 * Must be careful with the order of the tests. When someone has
425 * a ref to the page, it may be possible that they dirty it then
426 * drop the reference. So if PageDirty is tested before page_count
427 * here, then the following race may occur:
429 * get_user_pages(&page);
430 * [user mapping goes away]
432 * !PageDirty(page) [good]
433 * SetPageDirty(page);
435 * !page_count(page) [good, discard it]
437 * [oops, our write_to data is lost]
439 * Reversing the order of the tests ensures such a situation cannot
440 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
441 * load is not satisfied before that of page->_count.
443 * Note that if SetPageDirty is always performed via set_page_dirty,
444 * and thus under tree_lock, then this ordering is not required.
446 if (!page_freeze_refs(page, 2))
448 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
449 if (unlikely(PageDirty(page))) {
450 page_unfreeze_refs(page, 2);
454 if (PageSwapCache(page)) {
455 swp_entry_t swap = { .val = page_private(page) };
456 __delete_from_swap_cache(page);
457 spin_unlock_irq(&mapping->tree_lock);
458 swapcache_free(swap, page);
460 __remove_from_page_cache(page);
461 spin_unlock_irq(&mapping->tree_lock);
462 mem_cgroup_uncharge_cache_page(page);
468 spin_unlock_irq(&mapping->tree_lock);
473 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
474 * someone else has a ref on the page, abort and return 0. If it was
475 * successfully detached, return 1. Assumes the caller has a single ref on
478 int remove_mapping(struct address_space *mapping, struct page *page)
480 if (__remove_mapping(mapping, page)) {
482 * Unfreezing the refcount with 1 rather than 2 effectively
483 * drops the pagecache ref for us without requiring another
486 page_unfreeze_refs(page, 1);
493 * putback_lru_page - put previously isolated page onto appropriate LRU list
494 * @page: page to be put back to appropriate lru list
496 * Add previously isolated @page to appropriate LRU list.
497 * Page may still be unevictable for other reasons.
499 * lru_lock must not be held, interrupts must be enabled.
501 void putback_lru_page(struct page *page)
504 int active = !!TestClearPageActive(page);
505 int was_unevictable = PageUnevictable(page);
507 VM_BUG_ON(PageLRU(page));
510 ClearPageUnevictable(page);
512 if (page_evictable(page, NULL)) {
514 * For evictable pages, we can use the cache.
515 * In event of a race, worst case is we end up with an
516 * unevictable page on [in]active list.
517 * We know how to handle that.
519 lru = active + page_lru_base_type(page);
520 lru_cache_add_lru(page, lru);
523 * Put unevictable pages directly on zone's unevictable
526 lru = LRU_UNEVICTABLE;
527 add_page_to_unevictable_list(page);
529 * When racing with an mlock clearing (page is
530 * unlocked), make sure that if the other thread does
531 * not observe our setting of PG_lru and fails
532 * isolation, we see PG_mlocked cleared below and move
533 * the page back to the evictable list.
535 * The other side is TestClearPageMlocked().
541 * page's status can change while we move it among lru. If an evictable
542 * page is on unevictable list, it never be freed. To avoid that,
543 * check after we added it to the list, again.
545 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
546 if (!isolate_lru_page(page)) {
550 /* This means someone else dropped this page from LRU
551 * So, it will be freed or putback to LRU again. There is
552 * nothing to do here.
556 if (was_unevictable && lru != LRU_UNEVICTABLE)
557 count_vm_event(UNEVICTABLE_PGRESCUED);
558 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
559 count_vm_event(UNEVICTABLE_PGCULLED);
561 put_page(page); /* drop ref from isolate */
564 enum page_references {
566 PAGEREF_RECLAIM_CLEAN,
571 static enum page_references page_check_references(struct page *page,
572 struct scan_control *sc)
574 int referenced_ptes, referenced_page;
575 unsigned long vm_flags;
577 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
578 referenced_page = TestClearPageReferenced(page);
580 /* Lumpy reclaim - ignore references */
581 if (sc->lumpy_reclaim_mode)
582 return PAGEREF_RECLAIM;
585 * Mlock lost the isolation race with us. Let try_to_unmap()
586 * move the page to the unevictable list.
588 if (vm_flags & VM_LOCKED)
589 return PAGEREF_RECLAIM;
591 if (referenced_ptes) {
593 return PAGEREF_ACTIVATE;
595 * All mapped pages start out with page table
596 * references from the instantiating fault, so we need
597 * to look twice if a mapped file page is used more
600 * Mark it and spare it for another trip around the
601 * inactive list. Another page table reference will
602 * lead to its activation.
604 * Note: the mark is set for activated pages as well
605 * so that recently deactivated but used pages are
608 SetPageReferenced(page);
611 return PAGEREF_ACTIVATE;
616 /* Reclaim if clean, defer dirty pages to writeback */
618 return PAGEREF_RECLAIM_CLEAN;
620 return PAGEREF_RECLAIM;
624 * shrink_page_list() returns the number of reclaimed pages
626 static unsigned long shrink_page_list(struct list_head *page_list,
627 struct scan_control *sc,
628 enum pageout_io sync_writeback)
630 LIST_HEAD(ret_pages);
631 struct pagevec freed_pvec;
633 unsigned long nr_reclaimed = 0;
637 pagevec_init(&freed_pvec, 1);
638 while (!list_empty(page_list)) {
639 enum page_references references;
640 struct address_space *mapping;
646 page = lru_to_page(page_list);
647 list_del(&page->lru);
649 if (!trylock_page(page))
652 VM_BUG_ON(PageActive(page));
656 if (unlikely(!page_evictable(page, NULL)))
659 if (!sc->may_unmap && page_mapped(page))
662 /* Double the slab pressure for mapped and swapcache pages */
663 if (page_mapped(page) || PageSwapCache(page))
666 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
667 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
669 if (PageWriteback(page)) {
671 * Synchronous reclaim is performed in two passes,
672 * first an asynchronous pass over the list to
673 * start parallel writeback, and a second synchronous
674 * pass to wait for the IO to complete. Wait here
675 * for any page for which writeback has already
678 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
679 wait_on_page_writeback(page);
684 references = page_check_references(page, sc);
685 switch (references) {
686 case PAGEREF_ACTIVATE:
687 goto activate_locked;
690 case PAGEREF_RECLAIM:
691 case PAGEREF_RECLAIM_CLEAN:
692 ; /* try to reclaim the page below */
696 * Anonymous process memory has backing store?
697 * Try to allocate it some swap space here.
699 if (PageAnon(page) && !PageSwapCache(page)) {
700 if (!(sc->gfp_mask & __GFP_IO))
702 if (!add_to_swap(page))
703 goto activate_locked;
707 mapping = page_mapping(page);
710 * The page is mapped into the page tables of one or more
711 * processes. Try to unmap it here.
713 if (page_mapped(page) && mapping) {
714 switch (try_to_unmap(page, TTU_UNMAP)) {
716 goto activate_locked;
722 ; /* try to free the page below */
726 if (PageDirty(page)) {
727 if (references == PAGEREF_RECLAIM_CLEAN)
731 if (!sc->may_writepage)
734 /* Page is dirty, try to write it out here */
735 switch (pageout(page, mapping, sync_writeback)) {
739 goto activate_locked;
741 if (PageWriteback(page) || PageDirty(page))
744 * A synchronous write - probably a ramdisk. Go
745 * ahead and try to reclaim the page.
747 if (!trylock_page(page))
749 if (PageDirty(page) || PageWriteback(page))
751 mapping = page_mapping(page);
753 ; /* try to free the page below */
758 * If the page has buffers, try to free the buffer mappings
759 * associated with this page. If we succeed we try to free
762 * We do this even if the page is PageDirty().
763 * try_to_release_page() does not perform I/O, but it is
764 * possible for a page to have PageDirty set, but it is actually
765 * clean (all its buffers are clean). This happens if the
766 * buffers were written out directly, with submit_bh(). ext3
767 * will do this, as well as the blockdev mapping.
768 * try_to_release_page() will discover that cleanness and will
769 * drop the buffers and mark the page clean - it can be freed.
771 * Rarely, pages can have buffers and no ->mapping. These are
772 * the pages which were not successfully invalidated in
773 * truncate_complete_page(). We try to drop those buffers here
774 * and if that worked, and the page is no longer mapped into
775 * process address space (page_count == 1) it can be freed.
776 * Otherwise, leave the page on the LRU so it is swappable.
778 if (page_has_private(page)) {
779 if (!try_to_release_page(page, sc->gfp_mask))
780 goto activate_locked;
781 if (!mapping && page_count(page) == 1) {
783 if (put_page_testzero(page))
787 * rare race with speculative reference.
788 * the speculative reference will free
789 * this page shortly, so we may
790 * increment nr_reclaimed here (and
791 * leave it off the LRU).
799 if (!mapping || !__remove_mapping(mapping, page))
803 * At this point, we have no other references and there is
804 * no way to pick any more up (removed from LRU, removed
805 * from pagecache). Can use non-atomic bitops now (and
806 * we obviously don't have to worry about waking up a process
807 * waiting on the page lock, because there are no references.
809 __clear_page_locked(page);
812 if (!pagevec_add(&freed_pvec, page)) {
813 __pagevec_free(&freed_pvec);
814 pagevec_reinit(&freed_pvec);
819 if (PageSwapCache(page))
820 try_to_free_swap(page);
822 putback_lru_page(page);
826 /* Not a candidate for swapping, so reclaim swap space. */
827 if (PageSwapCache(page) && vm_swap_full())
828 try_to_free_swap(page);
829 VM_BUG_ON(PageActive(page));
835 list_add(&page->lru, &ret_pages);
836 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
838 list_splice(&ret_pages, page_list);
839 if (pagevec_count(&freed_pvec))
840 __pagevec_free(&freed_pvec);
841 count_vm_events(PGACTIVATE, pgactivate);
846 * Attempt to remove the specified page from its LRU. Only take this page
847 * if it is of the appropriate PageActive status. Pages which are being
848 * freed elsewhere are also ignored.
850 * page: page to consider
851 * mode: one of the LRU isolation modes defined above
853 * returns 0 on success, -ve errno on failure.
855 int __isolate_lru_page(struct page *page, int mode, int file)
859 /* Only take pages on the LRU. */
864 * When checking the active state, we need to be sure we are
865 * dealing with comparible boolean values. Take the logical not
868 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
871 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
875 * When this function is being called for lumpy reclaim, we
876 * initially look into all LRU pages, active, inactive and
877 * unevictable; only give shrink_page_list evictable pages.
879 if (PageUnevictable(page))
884 if (likely(get_page_unless_zero(page))) {
886 * Be careful not to clear PageLRU until after we're
887 * sure the page is not being freed elsewhere -- the
888 * page release code relies on it.
898 * zone->lru_lock is heavily contended. Some of the functions that
899 * shrink the lists perform better by taking out a batch of pages
900 * and working on them outside the LRU lock.
902 * For pagecache intensive workloads, this function is the hottest
903 * spot in the kernel (apart from copy_*_user functions).
905 * Appropriate locks must be held before calling this function.
907 * @nr_to_scan: The number of pages to look through on the list.
908 * @src: The LRU list to pull pages off.
909 * @dst: The temp list to put pages on to.
910 * @scanned: The number of pages that were scanned.
911 * @order: The caller's attempted allocation order
912 * @mode: One of the LRU isolation modes
913 * @file: True [1] if isolating file [!anon] pages
915 * returns how many pages were moved onto *@dst.
917 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
918 struct list_head *src, struct list_head *dst,
919 unsigned long *scanned, int order, int mode, int file)
921 unsigned long nr_taken = 0;
924 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
927 unsigned long end_pfn;
928 unsigned long page_pfn;
931 page = lru_to_page(src);
932 prefetchw_prev_lru_page(page, src, flags);
934 VM_BUG_ON(!PageLRU(page));
936 switch (__isolate_lru_page(page, mode, file)) {
938 list_move(&page->lru, dst);
939 mem_cgroup_del_lru(page);
944 /* else it is being freed elsewhere */
945 list_move(&page->lru, src);
946 mem_cgroup_rotate_lru_list(page, page_lru(page));
957 * Attempt to take all pages in the order aligned region
958 * surrounding the tag page. Only take those pages of
959 * the same active state as that tag page. We may safely
960 * round the target page pfn down to the requested order
961 * as the mem_map is guarenteed valid out to MAX_ORDER,
962 * where that page is in a different zone we will detect
963 * it from its zone id and abort this block scan.
965 zone_id = page_zone_id(page);
966 page_pfn = page_to_pfn(page);
967 pfn = page_pfn & ~((1 << order) - 1);
968 end_pfn = pfn + (1 << order);
969 for (; pfn < end_pfn; pfn++) {
970 struct page *cursor_page;
972 /* The target page is in the block, ignore it. */
973 if (unlikely(pfn == page_pfn))
976 /* Avoid holes within the zone. */
977 if (unlikely(!pfn_valid_within(pfn)))
980 cursor_page = pfn_to_page(pfn);
982 /* Check that we have not crossed a zone boundary. */
983 if (unlikely(page_zone_id(cursor_page) != zone_id))
987 * If we don't have enough swap space, reclaiming of
988 * anon page which don't already have a swap slot is
991 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
992 !PageSwapCache(cursor_page))
995 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
996 list_move(&cursor_page->lru, dst);
997 mem_cgroup_del_lru(cursor_page);
1008 static unsigned long isolate_pages_global(unsigned long nr,
1009 struct list_head *dst,
1010 unsigned long *scanned, int order,
1011 int mode, struct zone *z,
1012 int active, int file)
1019 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1024 * clear_active_flags() is a helper for shrink_active_list(), clearing
1025 * any active bits from the pages in the list.
1027 static unsigned long clear_active_flags(struct list_head *page_list,
1028 unsigned int *count)
1034 list_for_each_entry(page, page_list, lru) {
1035 lru = page_lru_base_type(page);
1036 if (PageActive(page)) {
1038 ClearPageActive(page);
1048 * isolate_lru_page - tries to isolate a page from its LRU list
1049 * @page: page to isolate from its LRU list
1051 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1052 * vmstat statistic corresponding to whatever LRU list the page was on.
1054 * Returns 0 if the page was removed from an LRU list.
1055 * Returns -EBUSY if the page was not on an LRU list.
1057 * The returned page will have PageLRU() cleared. If it was found on
1058 * the active list, it will have PageActive set. If it was found on
1059 * the unevictable list, it will have the PageUnevictable bit set. That flag
1060 * may need to be cleared by the caller before letting the page go.
1062 * The vmstat statistic corresponding to the list on which the page was
1063 * found will be decremented.
1066 * (1) Must be called with an elevated refcount on the page. This is a
1067 * fundamentnal difference from isolate_lru_pages (which is called
1068 * without a stable reference).
1069 * (2) the lru_lock must not be held.
1070 * (3) interrupts must be enabled.
1072 int isolate_lru_page(struct page *page)
1076 if (PageLRU(page)) {
1077 struct zone *zone = page_zone(page);
1079 spin_lock_irq(&zone->lru_lock);
1080 if (PageLRU(page) && get_page_unless_zero(page)) {
1081 int lru = page_lru(page);
1085 del_page_from_lru_list(zone, page, lru);
1087 spin_unlock_irq(&zone->lru_lock);
1093 * Are there way too many processes in the direct reclaim path already?
1095 static int too_many_isolated(struct zone *zone, int file,
1096 struct scan_control *sc)
1098 unsigned long inactive, isolated;
1100 if (current_is_kswapd())
1103 if (!scanning_global_lru(sc))
1107 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1108 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1110 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1111 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1114 return isolated > inactive;
1118 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1119 * of reclaimed pages
1121 static unsigned long shrink_inactive_list(unsigned long max_scan,
1122 struct zone *zone, struct scan_control *sc,
1123 int priority, int file)
1125 LIST_HEAD(page_list);
1126 struct pagevec pvec;
1127 unsigned long nr_scanned = 0;
1128 unsigned long nr_reclaimed = 0;
1129 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1131 while (unlikely(too_many_isolated(zone, file, sc))) {
1132 congestion_wait(BLK_RW_ASYNC, HZ/10);
1134 /* We are about to die and free our memory. Return now. */
1135 if (fatal_signal_pending(current))
1136 return SWAP_CLUSTER_MAX;
1140 pagevec_init(&pvec, 1);
1143 spin_lock_irq(&zone->lru_lock);
1146 unsigned long nr_taken;
1147 unsigned long nr_scan;
1148 unsigned long nr_freed;
1149 unsigned long nr_active;
1150 unsigned int count[NR_LRU_LISTS] = { 0, };
1151 int mode = sc->lumpy_reclaim_mode ? ISOLATE_BOTH : ISOLATE_INACTIVE;
1152 unsigned long nr_anon;
1153 unsigned long nr_file;
1155 if (scanning_global_lru(sc)) {
1156 nr_taken = isolate_pages_global(SWAP_CLUSTER_MAX,
1157 &page_list, &nr_scan,
1160 zone->pages_scanned += nr_scan;
1161 if (current_is_kswapd())
1162 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1165 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1168 nr_taken = mem_cgroup_isolate_pages(SWAP_CLUSTER_MAX,
1169 &page_list, &nr_scan,
1171 zone, sc->mem_cgroup,
1174 * mem_cgroup_isolate_pages() keeps track of
1175 * scanned pages on its own.
1182 nr_active = clear_active_flags(&page_list, count);
1183 __count_vm_events(PGDEACTIVATE, nr_active);
1185 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1186 -count[LRU_ACTIVE_FILE]);
1187 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1188 -count[LRU_INACTIVE_FILE]);
1189 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1190 -count[LRU_ACTIVE_ANON]);
1191 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1192 -count[LRU_INACTIVE_ANON]);
1194 nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1195 nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1196 __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
1197 __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
1199 reclaim_stat->recent_scanned[0] += nr_anon;
1200 reclaim_stat->recent_scanned[1] += nr_file;
1202 spin_unlock_irq(&zone->lru_lock);
1204 nr_scanned += nr_scan;
1205 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1208 * If we are direct reclaiming for contiguous pages and we do
1209 * not reclaim everything in the list, try again and wait
1210 * for IO to complete. This will stall high-order allocations
1211 * but that should be acceptable to the caller
1213 if (nr_freed < nr_taken && !current_is_kswapd() &&
1214 sc->lumpy_reclaim_mode) {
1215 congestion_wait(BLK_RW_ASYNC, HZ/10);
1218 * The attempt at page out may have made some
1219 * of the pages active, mark them inactive again.
1221 nr_active = clear_active_flags(&page_list, count);
1222 count_vm_events(PGDEACTIVATE, nr_active);
1224 nr_freed += shrink_page_list(&page_list, sc,
1228 nr_reclaimed += nr_freed;
1230 local_irq_disable();
1231 if (current_is_kswapd())
1232 __count_vm_events(KSWAPD_STEAL, nr_freed);
1233 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1235 spin_lock(&zone->lru_lock);
1237 * Put back any unfreeable pages.
1239 while (!list_empty(&page_list)) {
1241 page = lru_to_page(&page_list);
1242 VM_BUG_ON(PageLRU(page));
1243 list_del(&page->lru);
1244 if (unlikely(!page_evictable(page, NULL))) {
1245 spin_unlock_irq(&zone->lru_lock);
1246 putback_lru_page(page);
1247 spin_lock_irq(&zone->lru_lock);
1251 lru = page_lru(page);
1252 add_page_to_lru_list(zone, page, lru);
1253 if (is_active_lru(lru)) {
1254 int file = is_file_lru(lru);
1255 reclaim_stat->recent_rotated[file]++;
1257 if (!pagevec_add(&pvec, page)) {
1258 spin_unlock_irq(&zone->lru_lock);
1259 __pagevec_release(&pvec);
1260 spin_lock_irq(&zone->lru_lock);
1263 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1264 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1266 } while (nr_scanned < max_scan);
1269 spin_unlock_irq(&zone->lru_lock);
1270 pagevec_release(&pvec);
1271 return nr_reclaimed;
1275 * We are about to scan this zone at a certain priority level. If that priority
1276 * level is smaller (ie: more urgent) than the previous priority, then note
1277 * that priority level within the zone. This is done so that when the next
1278 * process comes in to scan this zone, it will immediately start out at this
1279 * priority level rather than having to build up its own scanning priority.
1280 * Here, this priority affects only the reclaim-mapped threshold.
1282 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1284 if (priority < zone->prev_priority)
1285 zone->prev_priority = priority;
1289 * This moves pages from the active list to the inactive list.
1291 * We move them the other way if the page is referenced by one or more
1292 * processes, from rmap.
1294 * If the pages are mostly unmapped, the processing is fast and it is
1295 * appropriate to hold zone->lru_lock across the whole operation. But if
1296 * the pages are mapped, the processing is slow (page_referenced()) so we
1297 * should drop zone->lru_lock around each page. It's impossible to balance
1298 * this, so instead we remove the pages from the LRU while processing them.
1299 * It is safe to rely on PG_active against the non-LRU pages in here because
1300 * nobody will play with that bit on a non-LRU page.
1302 * The downside is that we have to touch page->_count against each page.
1303 * But we had to alter page->flags anyway.
1306 static void move_active_pages_to_lru(struct zone *zone,
1307 struct list_head *list,
1310 unsigned long pgmoved = 0;
1311 struct pagevec pvec;
1314 pagevec_init(&pvec, 1);
1316 while (!list_empty(list)) {
1317 page = lru_to_page(list);
1319 VM_BUG_ON(PageLRU(page));
1322 list_move(&page->lru, &zone->lru[lru].list);
1323 mem_cgroup_add_lru_list(page, lru);
1326 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1327 spin_unlock_irq(&zone->lru_lock);
1328 if (buffer_heads_over_limit)
1329 pagevec_strip(&pvec);
1330 __pagevec_release(&pvec);
1331 spin_lock_irq(&zone->lru_lock);
1334 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1335 if (!is_active_lru(lru))
1336 __count_vm_events(PGDEACTIVATE, pgmoved);
1339 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1340 struct scan_control *sc, int priority, int file)
1342 unsigned long nr_taken;
1343 unsigned long pgscanned;
1344 unsigned long vm_flags;
1345 LIST_HEAD(l_hold); /* The pages which were snipped off */
1346 LIST_HEAD(l_active);
1347 LIST_HEAD(l_inactive);
1349 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1350 unsigned long nr_rotated = 0;
1353 spin_lock_irq(&zone->lru_lock);
1354 if (scanning_global_lru(sc)) {
1355 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1356 &pgscanned, sc->order,
1357 ISOLATE_ACTIVE, zone,
1359 zone->pages_scanned += pgscanned;
1361 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1362 &pgscanned, sc->order,
1363 ISOLATE_ACTIVE, zone,
1364 sc->mem_cgroup, 1, file);
1366 * mem_cgroup_isolate_pages() keeps track of
1367 * scanned pages on its own.
1371 reclaim_stat->recent_scanned[file] += nr_taken;
1373 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1375 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1377 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1378 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1379 spin_unlock_irq(&zone->lru_lock);
1381 while (!list_empty(&l_hold)) {
1383 page = lru_to_page(&l_hold);
1384 list_del(&page->lru);
1386 if (unlikely(!page_evictable(page, NULL))) {
1387 putback_lru_page(page);
1391 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1394 * Identify referenced, file-backed active pages and
1395 * give them one more trip around the active list. So
1396 * that executable code get better chances to stay in
1397 * memory under moderate memory pressure. Anon pages
1398 * are not likely to be evicted by use-once streaming
1399 * IO, plus JVM can create lots of anon VM_EXEC pages,
1400 * so we ignore them here.
1402 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1403 list_add(&page->lru, &l_active);
1408 ClearPageActive(page); /* we are de-activating */
1409 list_add(&page->lru, &l_inactive);
1413 * Move pages back to the lru list.
1415 spin_lock_irq(&zone->lru_lock);
1417 * Count referenced pages from currently used mappings as rotated,
1418 * even though only some of them are actually re-activated. This
1419 * helps balance scan pressure between file and anonymous pages in
1422 reclaim_stat->recent_rotated[file] += nr_rotated;
1424 move_active_pages_to_lru(zone, &l_active,
1425 LRU_ACTIVE + file * LRU_FILE);
1426 move_active_pages_to_lru(zone, &l_inactive,
1427 LRU_BASE + file * LRU_FILE);
1428 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1429 spin_unlock_irq(&zone->lru_lock);
1432 static int inactive_anon_is_low_global(struct zone *zone)
1434 unsigned long active, inactive;
1436 active = zone_page_state(zone, NR_ACTIVE_ANON);
1437 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1439 if (inactive * zone->inactive_ratio < active)
1446 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1447 * @zone: zone to check
1448 * @sc: scan control of this context
1450 * Returns true if the zone does not have enough inactive anon pages,
1451 * meaning some active anon pages need to be deactivated.
1453 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1457 if (scanning_global_lru(sc))
1458 low = inactive_anon_is_low_global(zone);
1460 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1464 static int inactive_file_is_low_global(struct zone *zone)
1466 unsigned long active, inactive;
1468 active = zone_page_state(zone, NR_ACTIVE_FILE);
1469 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1471 return (active > inactive);
1475 * inactive_file_is_low - check if file pages need to be deactivated
1476 * @zone: zone to check
1477 * @sc: scan control of this context
1479 * When the system is doing streaming IO, memory pressure here
1480 * ensures that active file pages get deactivated, until more
1481 * than half of the file pages are on the inactive list.
1483 * Once we get to that situation, protect the system's working
1484 * set from being evicted by disabling active file page aging.
1486 * This uses a different ratio than the anonymous pages, because
1487 * the page cache uses a use-once replacement algorithm.
1489 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1493 if (scanning_global_lru(sc))
1494 low = inactive_file_is_low_global(zone);
1496 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1500 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1504 return inactive_file_is_low(zone, sc);
1506 return inactive_anon_is_low(zone, sc);
1509 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1510 struct zone *zone, struct scan_control *sc, int priority)
1512 int file = is_file_lru(lru);
1514 if (is_active_lru(lru)) {
1515 if (inactive_list_is_low(zone, sc, file))
1516 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1520 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1524 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1525 * until we collected @swap_cluster_max pages to scan.
1527 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
1528 unsigned long *nr_saved_scan)
1532 *nr_saved_scan += nr_to_scan;
1533 nr = *nr_saved_scan;
1535 if (nr >= SWAP_CLUSTER_MAX)
1544 * Determine how aggressively the anon and file LRU lists should be
1545 * scanned. The relative value of each set of LRU lists is determined
1546 * by looking at the fraction of the pages scanned we did rotate back
1547 * onto the active list instead of evict.
1549 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1551 static void get_scan_count(struct zone *zone, struct scan_control *sc,
1552 unsigned long *nr, int priority)
1554 unsigned long anon, file, free;
1555 unsigned long anon_prio, file_prio;
1556 unsigned long ap, fp;
1557 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1558 u64 fraction[2], denominator;
1562 /* If we have no swap space, do not bother scanning anon pages. */
1563 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1571 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1572 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1573 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1574 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1576 if (scanning_global_lru(sc)) {
1577 free = zone_page_state(zone, NR_FREE_PAGES);
1578 /* If we have very few page cache pages,
1579 force-scan anon pages. */
1580 if (unlikely(file + free <= high_wmark_pages(zone))) {
1589 * OK, so we have swap space and a fair amount of page cache
1590 * pages. We use the recently rotated / recently scanned
1591 * ratios to determine how valuable each cache is.
1593 * Because workloads change over time (and to avoid overflow)
1594 * we keep these statistics as a floating average, which ends
1595 * up weighing recent references more than old ones.
1597 * anon in [0], file in [1]
1599 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1600 spin_lock_irq(&zone->lru_lock);
1601 reclaim_stat->recent_scanned[0] /= 2;
1602 reclaim_stat->recent_rotated[0] /= 2;
1603 spin_unlock_irq(&zone->lru_lock);
1606 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1607 spin_lock_irq(&zone->lru_lock);
1608 reclaim_stat->recent_scanned[1] /= 2;
1609 reclaim_stat->recent_rotated[1] /= 2;
1610 spin_unlock_irq(&zone->lru_lock);
1614 * With swappiness at 100, anonymous and file have the same priority.
1615 * This scanning priority is essentially the inverse of IO cost.
1617 anon_prio = sc->swappiness;
1618 file_prio = 200 - sc->swappiness;
1621 * The amount of pressure on anon vs file pages is inversely
1622 * proportional to the fraction of recently scanned pages on
1623 * each list that were recently referenced and in active use.
1625 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1626 ap /= reclaim_stat->recent_rotated[0] + 1;
1628 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1629 fp /= reclaim_stat->recent_rotated[1] + 1;
1633 denominator = ap + fp + 1;
1635 for_each_evictable_lru(l) {
1636 int file = is_file_lru(l);
1639 scan = zone_nr_lru_pages(zone, sc, l);
1640 if (priority || noswap) {
1642 scan = div64_u64(scan * fraction[file], denominator);
1644 nr[l] = nr_scan_try_batch(scan,
1645 &reclaim_stat->nr_saved_scan[l]);
1649 static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc)
1652 * If we need a large contiguous chunk of memory, or have
1653 * trouble getting a small set of contiguous pages, we
1654 * will reclaim both active and inactive pages.
1656 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1657 sc->lumpy_reclaim_mode = 1;
1658 else if (sc->order && priority < DEF_PRIORITY - 2)
1659 sc->lumpy_reclaim_mode = 1;
1661 sc->lumpy_reclaim_mode = 0;
1665 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1667 static void shrink_zone(int priority, struct zone *zone,
1668 struct scan_control *sc)
1670 unsigned long nr[NR_LRU_LISTS];
1671 unsigned long nr_to_scan;
1673 unsigned long nr_reclaimed = sc->nr_reclaimed;
1674 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1676 get_scan_count(zone, sc, nr, priority);
1678 set_lumpy_reclaim_mode(priority, sc);
1680 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1681 nr[LRU_INACTIVE_FILE]) {
1682 for_each_evictable_lru(l) {
1684 nr_to_scan = min_t(unsigned long,
1685 nr[l], SWAP_CLUSTER_MAX);
1686 nr[l] -= nr_to_scan;
1688 nr_reclaimed += shrink_list(l, nr_to_scan,
1689 zone, sc, priority);
1693 * On large memory systems, scan >> priority can become
1694 * really large. This is fine for the starting priority;
1695 * we want to put equal scanning pressure on each zone.
1696 * However, if the VM has a harder time of freeing pages,
1697 * with multiple processes reclaiming pages, the total
1698 * freeing target can get unreasonably large.
1700 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1704 sc->nr_reclaimed = nr_reclaimed;
1707 * Even if we did not try to evict anon pages at all, we want to
1708 * rebalance the anon lru active/inactive ratio.
1710 if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
1711 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1713 throttle_vm_writeout(sc->gfp_mask);
1717 * This is the direct reclaim path, for page-allocating processes. We only
1718 * try to reclaim pages from zones which will satisfy the caller's allocation
1721 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1723 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1725 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1726 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1727 * zone defense algorithm.
1729 * If a zone is deemed to be full of pinned pages then just give it a light
1730 * scan then give up on it.
1732 static bool shrink_zones(int priority, struct zonelist *zonelist,
1733 struct scan_control *sc)
1735 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1738 bool all_unreclaimable = true;
1740 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1742 if (!populated_zone(zone))
1745 * Take care memory controller reclaiming has small influence
1748 if (scanning_global_lru(sc)) {
1749 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1751 note_zone_scanning_priority(zone, priority);
1753 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1754 continue; /* Let kswapd poll it */
1757 * Ignore cpuset limitation here. We just want to reduce
1758 * # of used pages by us regardless of memory shortage.
1760 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1764 shrink_zone(priority, zone, sc);
1765 all_unreclaimable = false;
1767 return all_unreclaimable;
1771 * This is the main entry point to direct page reclaim.
1773 * If a full scan of the inactive list fails to free enough memory then we
1774 * are "out of memory" and something needs to be killed.
1776 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1777 * high - the zone may be full of dirty or under-writeback pages, which this
1778 * caller can't do much about. We kick the writeback threads and take explicit
1779 * naps in the hope that some of these pages can be written. But if the
1780 * allocating task holds filesystem locks which prevent writeout this might not
1781 * work, and the allocation attempt will fail.
1783 * returns: 0, if no pages reclaimed
1784 * else, the number of pages reclaimed
1786 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1787 struct scan_control *sc)
1790 bool all_unreclaimable;
1791 unsigned long total_scanned = 0;
1792 struct reclaim_state *reclaim_state = current->reclaim_state;
1795 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1796 unsigned long writeback_threshold;
1799 delayacct_freepages_start();
1801 if (scanning_global_lru(sc))
1802 count_vm_event(ALLOCSTALL);
1804 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1807 disable_swap_token();
1808 all_unreclaimable = shrink_zones(priority, zonelist, sc);
1810 * Don't shrink slabs when reclaiming memory from
1811 * over limit cgroups
1813 if (scanning_global_lru(sc)) {
1814 unsigned long lru_pages = 0;
1815 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1816 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1819 lru_pages += zone_reclaimable_pages(zone);
1822 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1823 if (reclaim_state) {
1824 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1825 reclaim_state->reclaimed_slab = 0;
1828 total_scanned += sc->nr_scanned;
1829 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
1833 * Try to write back as many pages as we just scanned. This
1834 * tends to cause slow streaming writers to write data to the
1835 * disk smoothly, at the dirtying rate, which is nice. But
1836 * that's undesirable in laptop mode, where we *want* lumpy
1837 * writeout. So in laptop mode, write out the whole world.
1839 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
1840 if (total_scanned > writeback_threshold) {
1841 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
1842 sc->may_writepage = 1;
1845 /* Take a nap, wait for some writeback to complete */
1846 if (!sc->hibernation_mode && sc->nr_scanned &&
1847 priority < DEF_PRIORITY - 2)
1848 congestion_wait(BLK_RW_ASYNC, HZ/10);
1853 * Now that we've scanned all the zones at this priority level, note
1854 * that level within the zone so that the next thread which performs
1855 * scanning of this zone will immediately start out at this priority
1856 * level. This affects only the decision whether or not to bring
1857 * mapped pages onto the inactive list.
1862 if (scanning_global_lru(sc)) {
1863 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1865 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1868 zone->prev_priority = priority;
1871 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1873 delayacct_freepages_end();
1876 if (sc->nr_reclaimed)
1877 return sc->nr_reclaimed;
1879 /* top priority shrink_zones still had more to do? don't OOM, then */
1880 if (scanning_global_lru(sc) && !all_unreclaimable)
1886 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1887 gfp_t gfp_mask, nodemask_t *nodemask)
1889 unsigned long nr_reclaimed;
1890 struct scan_control sc = {
1891 .gfp_mask = gfp_mask,
1892 .may_writepage = !laptop_mode,
1893 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1896 .swappiness = vm_swappiness,
1899 .nodemask = nodemask,
1902 trace_mm_vmscan_direct_reclaim_begin(order,
1906 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
1908 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
1910 return nr_reclaimed;
1913 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1915 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
1916 gfp_t gfp_mask, bool noswap,
1917 unsigned int swappiness,
1918 struct zone *zone, int nid)
1920 struct scan_control sc = {
1921 .may_writepage = !laptop_mode,
1923 .may_swap = !noswap,
1924 .swappiness = swappiness,
1928 nodemask_t nm = nodemask_of_node(nid);
1930 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1931 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1933 sc.nr_reclaimed = 0;
1936 * NOTE: Although we can get the priority field, using it
1937 * here is not a good idea, since it limits the pages we can scan.
1938 * if we don't reclaim here, the shrink_zone from balance_pgdat
1939 * will pick up pages from other mem cgroup's as well. We hack
1940 * the priority and make it zero.
1942 shrink_zone(0, zone, &sc);
1943 return sc.nr_reclaimed;
1946 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1949 unsigned int swappiness)
1951 struct zonelist *zonelist;
1952 struct scan_control sc = {
1953 .may_writepage = !laptop_mode,
1955 .may_swap = !noswap,
1956 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1957 .swappiness = swappiness,
1959 .mem_cgroup = mem_cont,
1960 .nodemask = NULL, /* we don't care the placement */
1963 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1964 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1965 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1966 return do_try_to_free_pages(zonelist, &sc);
1970 /* is kswapd sleeping prematurely? */
1971 static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
1975 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
1979 /* If after HZ/10, a zone is below the high mark, it's premature */
1980 for (i = 0; i < pgdat->nr_zones; i++) {
1981 struct zone *zone = pgdat->node_zones + i;
1983 if (!populated_zone(zone))
1986 if (zone->all_unreclaimable)
1989 if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
1998 * For kswapd, balance_pgdat() will work across all this node's zones until
1999 * they are all at high_wmark_pages(zone).
2001 * Returns the number of pages which were actually freed.
2003 * There is special handling here for zones which are full of pinned pages.
2004 * This can happen if the pages are all mlocked, or if they are all used by
2005 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2006 * What we do is to detect the case where all pages in the zone have been
2007 * scanned twice and there has been zero successful reclaim. Mark the zone as
2008 * dead and from now on, only perform a short scan. Basically we're polling
2009 * the zone for when the problem goes away.
2011 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2012 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2013 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2014 * lower zones regardless of the number of free pages in the lower zones. This
2015 * interoperates with the page allocator fallback scheme to ensure that aging
2016 * of pages is balanced across the zones.
2018 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
2023 unsigned long total_scanned;
2024 struct reclaim_state *reclaim_state = current->reclaim_state;
2025 struct scan_control sc = {
2026 .gfp_mask = GFP_KERNEL,
2030 * kswapd doesn't want to be bailed out while reclaim. because
2031 * we want to put equal scanning pressure on each zone.
2033 .nr_to_reclaim = ULONG_MAX,
2034 .swappiness = vm_swappiness,
2039 * temp_priority is used to remember the scanning priority at which
2040 * this zone was successfully refilled to
2041 * free_pages == high_wmark_pages(zone).
2043 int temp_priority[MAX_NR_ZONES];
2047 sc.nr_reclaimed = 0;
2048 sc.may_writepage = !laptop_mode;
2049 count_vm_event(PAGEOUTRUN);
2051 for (i = 0; i < pgdat->nr_zones; i++)
2052 temp_priority[i] = DEF_PRIORITY;
2054 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2055 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2056 unsigned long lru_pages = 0;
2057 int has_under_min_watermark_zone = 0;
2059 /* The swap token gets in the way of swapout... */
2061 disable_swap_token();
2066 * Scan in the highmem->dma direction for the highest
2067 * zone which needs scanning
2069 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2070 struct zone *zone = pgdat->node_zones + i;
2072 if (!populated_zone(zone))
2075 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2079 * Do some background aging of the anon list, to give
2080 * pages a chance to be referenced before reclaiming.
2082 if (inactive_anon_is_low(zone, &sc))
2083 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2086 if (!zone_watermark_ok(zone, order,
2087 high_wmark_pages(zone), 0, 0)) {
2095 for (i = 0; i <= end_zone; i++) {
2096 struct zone *zone = pgdat->node_zones + i;
2098 lru_pages += zone_reclaimable_pages(zone);
2102 * Now scan the zone in the dma->highmem direction, stopping
2103 * at the last zone which needs scanning.
2105 * We do this because the page allocator works in the opposite
2106 * direction. This prevents the page allocator from allocating
2107 * pages behind kswapd's direction of progress, which would
2108 * cause too much scanning of the lower zones.
2110 for (i = 0; i <= end_zone; i++) {
2111 struct zone *zone = pgdat->node_zones + i;
2115 if (!populated_zone(zone))
2118 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2121 temp_priority[i] = priority;
2123 note_zone_scanning_priority(zone, priority);
2125 nid = pgdat->node_id;
2126 zid = zone_idx(zone);
2128 * Call soft limit reclaim before calling shrink_zone.
2129 * For now we ignore the return value
2131 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask,
2134 * We put equal pressure on every zone, unless one
2135 * zone has way too many pages free already.
2137 if (!zone_watermark_ok(zone, order,
2138 8*high_wmark_pages(zone), end_zone, 0))
2139 shrink_zone(priority, zone, &sc);
2140 reclaim_state->reclaimed_slab = 0;
2141 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
2143 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2144 total_scanned += sc.nr_scanned;
2145 if (zone->all_unreclaimable)
2148 zone->pages_scanned >= (zone_reclaimable_pages(zone) * 6))
2149 zone->all_unreclaimable = 1;
2151 * If we've done a decent amount of scanning and
2152 * the reclaim ratio is low, start doing writepage
2153 * even in laptop mode
2155 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2156 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2157 sc.may_writepage = 1;
2159 if (!zone_watermark_ok(zone, order,
2160 high_wmark_pages(zone), end_zone, 0)) {
2163 * We are still under min water mark. This
2164 * means that we have a GFP_ATOMIC allocation
2165 * failure risk. Hurry up!
2167 if (!zone_watermark_ok(zone, order,
2168 min_wmark_pages(zone), end_zone, 0))
2169 has_under_min_watermark_zone = 1;
2174 break; /* kswapd: all done */
2176 * OK, kswapd is getting into trouble. Take a nap, then take
2177 * another pass across the zones.
2179 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2180 if (has_under_min_watermark_zone)
2181 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2183 congestion_wait(BLK_RW_ASYNC, HZ/10);
2187 * We do this so kswapd doesn't build up large priorities for
2188 * example when it is freeing in parallel with allocators. It
2189 * matches the direct reclaim path behaviour in terms of impact
2190 * on zone->*_priority.
2192 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2197 * Note within each zone the priority level at which this zone was
2198 * brought into a happy state. So that the next thread which scans this
2199 * zone will start out at that priority level.
2201 for (i = 0; i < pgdat->nr_zones; i++) {
2202 struct zone *zone = pgdat->node_zones + i;
2204 zone->prev_priority = temp_priority[i];
2206 if (!all_zones_ok) {
2212 * Fragmentation may mean that the system cannot be
2213 * rebalanced for high-order allocations in all zones.
2214 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2215 * it means the zones have been fully scanned and are still
2216 * not balanced. For high-order allocations, there is
2217 * little point trying all over again as kswapd may
2220 * Instead, recheck all watermarks at order-0 as they
2221 * are the most important. If watermarks are ok, kswapd will go
2222 * back to sleep. High-order users can still perform direct
2223 * reclaim if they wish.
2225 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2226 order = sc.order = 0;
2231 return sc.nr_reclaimed;
2235 * The background pageout daemon, started as a kernel thread
2236 * from the init process.
2238 * This basically trickles out pages so that we have _some_
2239 * free memory available even if there is no other activity
2240 * that frees anything up. This is needed for things like routing
2241 * etc, where we otherwise might have all activity going on in
2242 * asynchronous contexts that cannot page things out.
2244 * If there are applications that are active memory-allocators
2245 * (most normal use), this basically shouldn't matter.
2247 static int kswapd(void *p)
2249 unsigned long order;
2250 pg_data_t *pgdat = (pg_data_t*)p;
2251 struct task_struct *tsk = current;
2253 struct reclaim_state reclaim_state = {
2254 .reclaimed_slab = 0,
2256 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2258 lockdep_set_current_reclaim_state(GFP_KERNEL);
2260 if (!cpumask_empty(cpumask))
2261 set_cpus_allowed_ptr(tsk, cpumask);
2262 current->reclaim_state = &reclaim_state;
2265 * Tell the memory management that we're a "memory allocator",
2266 * and that if we need more memory we should get access to it
2267 * regardless (see "__alloc_pages()"). "kswapd" should
2268 * never get caught in the normal page freeing logic.
2270 * (Kswapd normally doesn't need memory anyway, but sometimes
2271 * you need a small amount of memory in order to be able to
2272 * page out something else, and this flag essentially protects
2273 * us from recursively trying to free more memory as we're
2274 * trying to free the first piece of memory in the first place).
2276 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2281 unsigned long new_order;
2284 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2285 new_order = pgdat->kswapd_max_order;
2286 pgdat->kswapd_max_order = 0;
2287 if (order < new_order) {
2289 * Don't sleep if someone wants a larger 'order'
2294 if (!freezing(current) && !kthread_should_stop()) {
2297 /* Try to sleep for a short interval */
2298 if (!sleeping_prematurely(pgdat, order, remaining)) {
2299 remaining = schedule_timeout(HZ/10);
2300 finish_wait(&pgdat->kswapd_wait, &wait);
2301 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2305 * After a short sleep, check if it was a
2306 * premature sleep. If not, then go fully
2307 * to sleep until explicitly woken up
2309 if (!sleeping_prematurely(pgdat, order, remaining)) {
2310 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2314 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2316 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2320 order = pgdat->kswapd_max_order;
2322 finish_wait(&pgdat->kswapd_wait, &wait);
2324 ret = try_to_freeze();
2325 if (kthread_should_stop())
2329 * We can speed up thawing tasks if we don't call balance_pgdat
2330 * after returning from the refrigerator
2333 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2334 balance_pgdat(pgdat, order);
2341 * A zone is low on free memory, so wake its kswapd task to service it.
2343 void wakeup_kswapd(struct zone *zone, int order)
2347 if (!populated_zone(zone))
2350 pgdat = zone->zone_pgdat;
2351 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
2353 if (pgdat->kswapd_max_order < order)
2354 pgdat->kswapd_max_order = order;
2355 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2356 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2358 if (!waitqueue_active(&pgdat->kswapd_wait))
2360 wake_up_interruptible(&pgdat->kswapd_wait);
2364 * The reclaimable count would be mostly accurate.
2365 * The less reclaimable pages may be
2366 * - mlocked pages, which will be moved to unevictable list when encountered
2367 * - mapped pages, which may require several travels to be reclaimed
2368 * - dirty pages, which is not "instantly" reclaimable
2370 unsigned long global_reclaimable_pages(void)
2374 nr = global_page_state(NR_ACTIVE_FILE) +
2375 global_page_state(NR_INACTIVE_FILE);
2377 if (nr_swap_pages > 0)
2378 nr += global_page_state(NR_ACTIVE_ANON) +
2379 global_page_state(NR_INACTIVE_ANON);
2384 unsigned long zone_reclaimable_pages(struct zone *zone)
2388 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2389 zone_page_state(zone, NR_INACTIVE_FILE);
2391 if (nr_swap_pages > 0)
2392 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2393 zone_page_state(zone, NR_INACTIVE_ANON);
2398 #ifdef CONFIG_HIBERNATION
2400 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2403 * Rather than trying to age LRUs the aim is to preserve the overall
2404 * LRU order by reclaiming preferentially
2405 * inactive > active > active referenced > active mapped
2407 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2409 struct reclaim_state reclaim_state;
2410 struct scan_control sc = {
2411 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2415 .nr_to_reclaim = nr_to_reclaim,
2416 .hibernation_mode = 1,
2417 .swappiness = vm_swappiness,
2420 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2421 struct task_struct *p = current;
2422 unsigned long nr_reclaimed;
2424 p->flags |= PF_MEMALLOC;
2425 lockdep_set_current_reclaim_state(sc.gfp_mask);
2426 reclaim_state.reclaimed_slab = 0;
2427 p->reclaim_state = &reclaim_state;
2429 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2431 p->reclaim_state = NULL;
2432 lockdep_clear_current_reclaim_state();
2433 p->flags &= ~PF_MEMALLOC;
2435 return nr_reclaimed;
2437 #endif /* CONFIG_HIBERNATION */
2439 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2440 not required for correctness. So if the last cpu in a node goes
2441 away, we get changed to run anywhere: as the first one comes back,
2442 restore their cpu bindings. */
2443 static int __devinit cpu_callback(struct notifier_block *nfb,
2444 unsigned long action, void *hcpu)
2448 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2449 for_each_node_state(nid, N_HIGH_MEMORY) {
2450 pg_data_t *pgdat = NODE_DATA(nid);
2451 const struct cpumask *mask;
2453 mask = cpumask_of_node(pgdat->node_id);
2455 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2456 /* One of our CPUs online: restore mask */
2457 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2464 * This kswapd start function will be called by init and node-hot-add.
2465 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2467 int kswapd_run(int nid)
2469 pg_data_t *pgdat = NODE_DATA(nid);
2475 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2476 if (IS_ERR(pgdat->kswapd)) {
2477 /* failure at boot is fatal */
2478 BUG_ON(system_state == SYSTEM_BOOTING);
2479 printk("Failed to start kswapd on node %d\n",nid);
2486 * Called by memory hotplug when all memory in a node is offlined.
2488 void kswapd_stop(int nid)
2490 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2493 kthread_stop(kswapd);
2496 static int __init kswapd_init(void)
2501 for_each_node_state(nid, N_HIGH_MEMORY)
2503 hotcpu_notifier(cpu_callback, 0);
2507 module_init(kswapd_init)
2513 * If non-zero call zone_reclaim when the number of free pages falls below
2516 int zone_reclaim_mode __read_mostly;
2518 #define RECLAIM_OFF 0
2519 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2520 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2521 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2524 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2525 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2528 #define ZONE_RECLAIM_PRIORITY 4
2531 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2534 int sysctl_min_unmapped_ratio = 1;
2537 * If the number of slab pages in a zone grows beyond this percentage then
2538 * slab reclaim needs to occur.
2540 int sysctl_min_slab_ratio = 5;
2542 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
2544 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
2545 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
2546 zone_page_state(zone, NR_ACTIVE_FILE);
2549 * It's possible for there to be more file mapped pages than
2550 * accounted for by the pages on the file LRU lists because
2551 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2553 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
2556 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2557 static long zone_pagecache_reclaimable(struct zone *zone)
2559 long nr_pagecache_reclaimable;
2563 * If RECLAIM_SWAP is set, then all file pages are considered
2564 * potentially reclaimable. Otherwise, we have to worry about
2565 * pages like swapcache and zone_unmapped_file_pages() provides
2568 if (zone_reclaim_mode & RECLAIM_SWAP)
2569 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
2571 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
2573 /* If we can't clean pages, remove dirty pages from consideration */
2574 if (!(zone_reclaim_mode & RECLAIM_WRITE))
2575 delta += zone_page_state(zone, NR_FILE_DIRTY);
2577 /* Watch for any possible underflows due to delta */
2578 if (unlikely(delta > nr_pagecache_reclaimable))
2579 delta = nr_pagecache_reclaimable;
2581 return nr_pagecache_reclaimable - delta;
2585 * Try to free up some pages from this zone through reclaim.
2587 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2589 /* Minimum pages needed in order to stay on node */
2590 const unsigned long nr_pages = 1 << order;
2591 struct task_struct *p = current;
2592 struct reclaim_state reclaim_state;
2594 struct scan_control sc = {
2595 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2596 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2598 .nr_to_reclaim = max_t(unsigned long, nr_pages,
2600 .gfp_mask = gfp_mask,
2601 .swappiness = vm_swappiness,
2604 unsigned long slab_reclaimable;
2608 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2609 * and we also need to be able to write out pages for RECLAIM_WRITE
2612 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2613 lockdep_set_current_reclaim_state(gfp_mask);
2614 reclaim_state.reclaimed_slab = 0;
2615 p->reclaim_state = &reclaim_state;
2617 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2619 * Free memory by calling shrink zone with increasing
2620 * priorities until we have enough memory freed.
2622 priority = ZONE_RECLAIM_PRIORITY;
2624 note_zone_scanning_priority(zone, priority);
2625 shrink_zone(priority, zone, &sc);
2627 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2630 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2631 if (slab_reclaimable > zone->min_slab_pages) {
2633 * shrink_slab() does not currently allow us to determine how
2634 * many pages were freed in this zone. So we take the current
2635 * number of slab pages and shake the slab until it is reduced
2636 * by the same nr_pages that we used for reclaiming unmapped
2639 * Note that shrink_slab will free memory on all zones and may
2642 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2643 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2644 slab_reclaimable - nr_pages)
2648 * Update nr_reclaimed by the number of slab pages we
2649 * reclaimed from this zone.
2651 sc.nr_reclaimed += slab_reclaimable -
2652 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2655 p->reclaim_state = NULL;
2656 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2657 lockdep_clear_current_reclaim_state();
2658 return sc.nr_reclaimed >= nr_pages;
2661 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2667 * Zone reclaim reclaims unmapped file backed pages and
2668 * slab pages if we are over the defined limits.
2670 * A small portion of unmapped file backed pages is needed for
2671 * file I/O otherwise pages read by file I/O will be immediately
2672 * thrown out if the zone is overallocated. So we do not reclaim
2673 * if less than a specified percentage of the zone is used by
2674 * unmapped file backed pages.
2676 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
2677 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
2678 return ZONE_RECLAIM_FULL;
2680 if (zone->all_unreclaimable)
2681 return ZONE_RECLAIM_FULL;
2684 * Do not scan if the allocation should not be delayed.
2686 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2687 return ZONE_RECLAIM_NOSCAN;
2690 * Only run zone reclaim on the local zone or on zones that do not
2691 * have associated processors. This will favor the local processor
2692 * over remote processors and spread off node memory allocations
2693 * as wide as possible.
2695 node_id = zone_to_nid(zone);
2696 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2697 return ZONE_RECLAIM_NOSCAN;
2699 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2700 return ZONE_RECLAIM_NOSCAN;
2702 ret = __zone_reclaim(zone, gfp_mask, order);
2703 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2706 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
2713 * page_evictable - test whether a page is evictable
2714 * @page: the page to test
2715 * @vma: the VMA in which the page is or will be mapped, may be NULL
2717 * Test whether page is evictable--i.e., should be placed on active/inactive
2718 * lists vs unevictable list. The vma argument is !NULL when called from the
2719 * fault path to determine how to instantate a new page.
2721 * Reasons page might not be evictable:
2722 * (1) page's mapping marked unevictable
2723 * (2) page is part of an mlocked VMA
2726 int page_evictable(struct page *page, struct vm_area_struct *vma)
2729 if (mapping_unevictable(page_mapping(page)))
2732 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2739 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2740 * @page: page to check evictability and move to appropriate lru list
2741 * @zone: zone page is in
2743 * Checks a page for evictability and moves the page to the appropriate
2746 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2747 * have PageUnevictable set.
2749 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2751 VM_BUG_ON(PageActive(page));
2754 ClearPageUnevictable(page);
2755 if (page_evictable(page, NULL)) {
2756 enum lru_list l = page_lru_base_type(page);
2758 __dec_zone_state(zone, NR_UNEVICTABLE);
2759 list_move(&page->lru, &zone->lru[l].list);
2760 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2761 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2762 __count_vm_event(UNEVICTABLE_PGRESCUED);
2765 * rotate unevictable list
2767 SetPageUnevictable(page);
2768 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2769 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2770 if (page_evictable(page, NULL))
2776 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2777 * @mapping: struct address_space to scan for evictable pages
2779 * Scan all pages in mapping. Check unevictable pages for
2780 * evictability and move them to the appropriate zone lru list.
2782 void scan_mapping_unevictable_pages(struct address_space *mapping)
2785 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2788 struct pagevec pvec;
2790 if (mapping->nrpages == 0)
2793 pagevec_init(&pvec, 0);
2794 while (next < end &&
2795 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2801 for (i = 0; i < pagevec_count(&pvec); i++) {
2802 struct page *page = pvec.pages[i];
2803 pgoff_t page_index = page->index;
2804 struct zone *pagezone = page_zone(page);
2807 if (page_index > next)
2811 if (pagezone != zone) {
2813 spin_unlock_irq(&zone->lru_lock);
2815 spin_lock_irq(&zone->lru_lock);
2818 if (PageLRU(page) && PageUnevictable(page))
2819 check_move_unevictable_page(page, zone);
2822 spin_unlock_irq(&zone->lru_lock);
2823 pagevec_release(&pvec);
2825 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2831 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2832 * @zone - zone of which to scan the unevictable list
2834 * Scan @zone's unevictable LRU lists to check for pages that have become
2835 * evictable. Move those that have to @zone's inactive list where they
2836 * become candidates for reclaim, unless shrink_inactive_zone() decides
2837 * to reactivate them. Pages that are still unevictable are rotated
2838 * back onto @zone's unevictable list.
2840 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2841 static void scan_zone_unevictable_pages(struct zone *zone)
2843 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2845 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2847 while (nr_to_scan > 0) {
2848 unsigned long batch_size = min(nr_to_scan,
2849 SCAN_UNEVICTABLE_BATCH_SIZE);
2851 spin_lock_irq(&zone->lru_lock);
2852 for (scan = 0; scan < batch_size; scan++) {
2853 struct page *page = lru_to_page(l_unevictable);
2855 if (!trylock_page(page))
2858 prefetchw_prev_lru_page(page, l_unevictable, flags);
2860 if (likely(PageLRU(page) && PageUnevictable(page)))
2861 check_move_unevictable_page(page, zone);
2865 spin_unlock_irq(&zone->lru_lock);
2867 nr_to_scan -= batch_size;
2873 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2875 * A really big hammer: scan all zones' unevictable LRU lists to check for
2876 * pages that have become evictable. Move those back to the zones'
2877 * inactive list where they become candidates for reclaim.
2878 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2879 * and we add swap to the system. As such, it runs in the context of a task
2880 * that has possibly/probably made some previously unevictable pages
2883 static void scan_all_zones_unevictable_pages(void)
2887 for_each_zone(zone) {
2888 scan_zone_unevictable_pages(zone);
2893 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2894 * all nodes' unevictable lists for evictable pages
2896 unsigned long scan_unevictable_pages;
2898 int scan_unevictable_handler(struct ctl_table *table, int write,
2899 void __user *buffer,
2900 size_t *length, loff_t *ppos)
2902 proc_doulongvec_minmax(table, write, buffer, length, ppos);
2904 if (write && *(unsigned long *)table->data)
2905 scan_all_zones_unevictable_pages();
2907 scan_unevictable_pages = 0;
2912 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2913 * a specified node's per zone unevictable lists for evictable pages.
2916 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2917 struct sysdev_attribute *attr,
2920 return sprintf(buf, "0\n"); /* always zero; should fit... */
2923 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2924 struct sysdev_attribute *attr,
2925 const char *buf, size_t count)
2927 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2930 unsigned long req = strict_strtoul(buf, 10, &res);
2933 return 1; /* zero is no-op */
2935 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2936 if (!populated_zone(zone))
2938 scan_zone_unevictable_pages(zone);
2944 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2945 read_scan_unevictable_node,
2946 write_scan_unevictable_node);
2948 int scan_unevictable_register_node(struct node *node)
2950 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2953 void scan_unevictable_unregister_node(struct node *node)
2955 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);