x86/PCI: use host bridge _CRS info on ASRock ALiveSATA2-GLAN
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / mm / vmscan.c
blob3ff3311447f58c2122a5154a85b6cd034d6c7e0e
1 /*
2 * linux/mm/vmscan.c
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
14 #include <linux/mm.h>
15 #include <linux/module.h>
16 #include <linux/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>
49 #include "internal.h"
51 struct scan_control {
52 /* Incremented by the number of inactive pages that were scanned */
53 unsigned long nr_scanned;
55 /* Number of pages freed so far during a call to shrink_zones() */
56 unsigned long nr_reclaimed;
58 /* How many pages shrink_list() should reclaim */
59 unsigned long nr_to_reclaim;
61 unsigned long hibernation_mode;
63 /* This context's GFP mask */
64 gfp_t gfp_mask;
66 int may_writepage;
68 /* Can mapped pages be reclaimed? */
69 int may_unmap;
71 /* Can pages be swapped as part of reclaim? */
72 int may_swap;
74 int swappiness;
76 int all_unreclaimable;
78 int order;
80 /* Which cgroup do we reclaim from */
81 struct mem_cgroup *mem_cgroup;
84 * Nodemask of nodes allowed by the caller. If NULL, all nodes
85 * are scanned.
87 nodemask_t *nodemask;
89 /* Pluggable isolate pages callback */
90 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
91 unsigned long *scanned, int order, int mode,
92 struct zone *z, struct mem_cgroup *mem_cont,
93 int active, int file);
96 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
98 #ifdef ARCH_HAS_PREFETCH
99 #define prefetch_prev_lru_page(_page, _base, _field) \
100 do { \
101 if ((_page)->lru.prev != _base) { \
102 struct page *prev; \
104 prev = lru_to_page(&(_page->lru)); \
105 prefetch(&prev->_field); \
107 } while (0)
108 #else
109 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
110 #endif
112 #ifdef ARCH_HAS_PREFETCHW
113 #define prefetchw_prev_lru_page(_page, _base, _field) \
114 do { \
115 if ((_page)->lru.prev != _base) { \
116 struct page *prev; \
118 prev = lru_to_page(&(_page->lru)); \
119 prefetchw(&prev->_field); \
121 } while (0)
122 #else
123 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
124 #endif
127 * From 0 .. 100. Higher means more swappy.
129 int vm_swappiness = 60;
130 long vm_total_pages; /* The total number of pages which the VM controls */
132 static LIST_HEAD(shrinker_list);
133 static DECLARE_RWSEM(shrinker_rwsem);
135 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
136 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
137 #else
138 #define scanning_global_lru(sc) (1)
139 #endif
141 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
142 struct scan_control *sc)
144 if (!scanning_global_lru(sc))
145 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
147 return &zone->reclaim_stat;
150 static unsigned long zone_nr_lru_pages(struct zone *zone,
151 struct scan_control *sc, enum lru_list lru)
153 if (!scanning_global_lru(sc))
154 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
156 return zone_page_state(zone, NR_LRU_BASE + lru);
161 * Add a shrinker callback to be called from the vm
163 void register_shrinker(struct shrinker *shrinker)
165 shrinker->nr = 0;
166 down_write(&shrinker_rwsem);
167 list_add_tail(&shrinker->list, &shrinker_list);
168 up_write(&shrinker_rwsem);
170 EXPORT_SYMBOL(register_shrinker);
173 * Remove one
175 void unregister_shrinker(struct shrinker *shrinker)
177 down_write(&shrinker_rwsem);
178 list_del(&shrinker->list);
179 up_write(&shrinker_rwsem);
181 EXPORT_SYMBOL(unregister_shrinker);
183 #define SHRINK_BATCH 128
185 * Call the shrink functions to age shrinkable caches
187 * Here we assume it costs one seek to replace a lru page and that it also
188 * takes a seek to recreate a cache object. With this in mind we age equal
189 * percentages of the lru and ageable caches. This should balance the seeks
190 * generated by these structures.
192 * If the vm encountered mapped pages on the LRU it increase the pressure on
193 * slab to avoid swapping.
195 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
197 * `lru_pages' represents the number of on-LRU pages in all the zones which
198 * are eligible for the caller's allocation attempt. It is used for balancing
199 * slab reclaim versus page reclaim.
201 * Returns the number of slab objects which we shrunk.
203 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
204 unsigned long lru_pages)
206 struct shrinker *shrinker;
207 unsigned long ret = 0;
209 if (scanned == 0)
210 scanned = SWAP_CLUSTER_MAX;
212 if (!down_read_trylock(&shrinker_rwsem))
213 return 1; /* Assume we'll be able to shrink next time */
215 list_for_each_entry(shrinker, &shrinker_list, list) {
216 unsigned long long delta;
217 unsigned long total_scan;
218 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
220 delta = (4 * scanned) / shrinker->seeks;
221 delta *= max_pass;
222 do_div(delta, lru_pages + 1);
223 shrinker->nr += delta;
224 if (shrinker->nr < 0) {
225 printk(KERN_ERR "shrink_slab: %pF negative objects to "
226 "delete nr=%ld\n",
227 shrinker->shrink, shrinker->nr);
228 shrinker->nr = max_pass;
232 * Avoid risking looping forever due to too large nr value:
233 * never try to free more than twice the estimate number of
234 * freeable entries.
236 if (shrinker->nr > max_pass * 2)
237 shrinker->nr = max_pass * 2;
239 total_scan = shrinker->nr;
240 shrinker->nr = 0;
242 while (total_scan >= SHRINK_BATCH) {
243 long this_scan = SHRINK_BATCH;
244 int shrink_ret;
245 int nr_before;
247 nr_before = (*shrinker->shrink)(0, gfp_mask);
248 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
249 if (shrink_ret == -1)
250 break;
251 if (shrink_ret < nr_before)
252 ret += nr_before - shrink_ret;
253 count_vm_events(SLABS_SCANNED, this_scan);
254 total_scan -= this_scan;
256 cond_resched();
259 shrinker->nr += total_scan;
261 up_read(&shrinker_rwsem);
262 return ret;
265 static inline int is_page_cache_freeable(struct page *page)
268 * A freeable page cache page is referenced only by the caller
269 * that isolated the page, the page cache radix tree and
270 * optional buffer heads at page->private.
272 return page_count(page) - page_has_private(page) == 2;
275 static int may_write_to_queue(struct backing_dev_info *bdi)
277 if (current->flags & PF_SWAPWRITE)
278 return 1;
279 if (!bdi_write_congested(bdi))
280 return 1;
281 if (bdi == current->backing_dev_info)
282 return 1;
283 return 0;
287 * We detected a synchronous write error writing a page out. Probably
288 * -ENOSPC. We need to propagate that into the address_space for a subsequent
289 * fsync(), msync() or close().
291 * The tricky part is that after writepage we cannot touch the mapping: nothing
292 * prevents it from being freed up. But we have a ref on the page and once
293 * that page is locked, the mapping is pinned.
295 * We're allowed to run sleeping lock_page() here because we know the caller has
296 * __GFP_FS.
298 static void handle_write_error(struct address_space *mapping,
299 struct page *page, int error)
301 lock_page(page);
302 if (page_mapping(page) == mapping)
303 mapping_set_error(mapping, error);
304 unlock_page(page);
307 /* Request for sync pageout. */
308 enum pageout_io {
309 PAGEOUT_IO_ASYNC,
310 PAGEOUT_IO_SYNC,
313 /* possible outcome of pageout() */
314 typedef enum {
315 /* failed to write page out, page is locked */
316 PAGE_KEEP,
317 /* move page to the active list, page is locked */
318 PAGE_ACTIVATE,
319 /* page has been sent to the disk successfully, page is unlocked */
320 PAGE_SUCCESS,
321 /* page is clean and locked */
322 PAGE_CLEAN,
323 } pageout_t;
326 * pageout is called by shrink_page_list() for each dirty page.
327 * Calls ->writepage().
329 static pageout_t pageout(struct page *page, struct address_space *mapping,
330 enum pageout_io sync_writeback)
333 * If the page is dirty, only perform writeback if that write
334 * will be non-blocking. To prevent this allocation from being
335 * stalled by pagecache activity. But note that there may be
336 * stalls if we need to run get_block(). We could test
337 * PagePrivate for that.
339 * If this process is currently in __generic_file_aio_write() against
340 * this page's queue, we can perform writeback even if that
341 * will block.
343 * If the page is swapcache, write it back even if that would
344 * block, for some throttling. This happens by accident, because
345 * swap_backing_dev_info is bust: it doesn't reflect the
346 * congestion state of the swapdevs. Easy to fix, if needed.
348 if (!is_page_cache_freeable(page))
349 return PAGE_KEEP;
350 if (!mapping) {
352 * Some data journaling orphaned pages can have
353 * page->mapping == NULL while being dirty with clean buffers.
355 if (page_has_private(page)) {
356 if (try_to_free_buffers(page)) {
357 ClearPageDirty(page);
358 printk("%s: orphaned page\n", __func__);
359 return PAGE_CLEAN;
362 return PAGE_KEEP;
364 if (mapping->a_ops->writepage == NULL)
365 return PAGE_ACTIVATE;
366 if (!may_write_to_queue(mapping->backing_dev_info))
367 return PAGE_KEEP;
369 if (clear_page_dirty_for_io(page)) {
370 int res;
371 struct writeback_control wbc = {
372 .sync_mode = WB_SYNC_NONE,
373 .nr_to_write = SWAP_CLUSTER_MAX,
374 .range_start = 0,
375 .range_end = LLONG_MAX,
376 .nonblocking = 1,
377 .for_reclaim = 1,
380 SetPageReclaim(page);
381 res = mapping->a_ops->writepage(page, &wbc);
382 if (res < 0)
383 handle_write_error(mapping, page, res);
384 if (res == AOP_WRITEPAGE_ACTIVATE) {
385 ClearPageReclaim(page);
386 return PAGE_ACTIVATE;
390 * Wait on writeback if requested to. This happens when
391 * direct reclaiming a large contiguous area and the
392 * first attempt to free a range of pages fails.
394 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
395 wait_on_page_writeback(page);
397 if (!PageWriteback(page)) {
398 /* synchronous write or broken a_ops? */
399 ClearPageReclaim(page);
401 inc_zone_page_state(page, NR_VMSCAN_WRITE);
402 return PAGE_SUCCESS;
405 return PAGE_CLEAN;
409 * Same as remove_mapping, but if the page is removed from the mapping, it
410 * gets returned with a refcount of 0.
412 static int __remove_mapping(struct address_space *mapping, struct page *page)
414 BUG_ON(!PageLocked(page));
415 BUG_ON(mapping != page_mapping(page));
417 spin_lock_irq(&mapping->tree_lock);
419 * The non racy check for a busy page.
421 * Must be careful with the order of the tests. When someone has
422 * a ref to the page, it may be possible that they dirty it then
423 * drop the reference. So if PageDirty is tested before page_count
424 * here, then the following race may occur:
426 * get_user_pages(&page);
427 * [user mapping goes away]
428 * write_to(page);
429 * !PageDirty(page) [good]
430 * SetPageDirty(page);
431 * put_page(page);
432 * !page_count(page) [good, discard it]
434 * [oops, our write_to data is lost]
436 * Reversing the order of the tests ensures such a situation cannot
437 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
438 * load is not satisfied before that of page->_count.
440 * Note that if SetPageDirty is always performed via set_page_dirty,
441 * and thus under tree_lock, then this ordering is not required.
443 if (!page_freeze_refs(page, 2))
444 goto cannot_free;
445 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
446 if (unlikely(PageDirty(page))) {
447 page_unfreeze_refs(page, 2);
448 goto cannot_free;
451 if (PageSwapCache(page)) {
452 swp_entry_t swap = { .val = page_private(page) };
453 __delete_from_swap_cache(page);
454 spin_unlock_irq(&mapping->tree_lock);
455 swapcache_free(swap, page);
456 } else {
457 __remove_from_page_cache(page);
458 spin_unlock_irq(&mapping->tree_lock);
459 mem_cgroup_uncharge_cache_page(page);
462 return 1;
464 cannot_free:
465 spin_unlock_irq(&mapping->tree_lock);
466 return 0;
470 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
471 * someone else has a ref on the page, abort and return 0. If it was
472 * successfully detached, return 1. Assumes the caller has a single ref on
473 * this page.
475 int remove_mapping(struct address_space *mapping, struct page *page)
477 if (__remove_mapping(mapping, page)) {
479 * Unfreezing the refcount with 1 rather than 2 effectively
480 * drops the pagecache ref for us without requiring another
481 * atomic operation.
483 page_unfreeze_refs(page, 1);
484 return 1;
486 return 0;
490 * putback_lru_page - put previously isolated page onto appropriate LRU list
491 * @page: page to be put back to appropriate lru list
493 * Add previously isolated @page to appropriate LRU list.
494 * Page may still be unevictable for other reasons.
496 * lru_lock must not be held, interrupts must be enabled.
498 void putback_lru_page(struct page *page)
500 int lru;
501 int active = !!TestClearPageActive(page);
502 int was_unevictable = PageUnevictable(page);
504 VM_BUG_ON(PageLRU(page));
506 redo:
507 ClearPageUnevictable(page);
509 if (page_evictable(page, NULL)) {
511 * For evictable pages, we can use the cache.
512 * In event of a race, worst case is we end up with an
513 * unevictable page on [in]active list.
514 * We know how to handle that.
516 lru = active + page_lru_base_type(page);
517 lru_cache_add_lru(page, lru);
518 } else {
520 * Put unevictable pages directly on zone's unevictable
521 * list.
523 lru = LRU_UNEVICTABLE;
524 add_page_to_unevictable_list(page);
526 * When racing with an mlock clearing (page is
527 * unlocked), make sure that if the other thread does
528 * not observe our setting of PG_lru and fails
529 * isolation, we see PG_mlocked cleared below and move
530 * the page back to the evictable list.
532 * The other side is TestClearPageMlocked().
534 smp_mb();
538 * page's status can change while we move it among lru. If an evictable
539 * page is on unevictable list, it never be freed. To avoid that,
540 * check after we added it to the list, again.
542 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
543 if (!isolate_lru_page(page)) {
544 put_page(page);
545 goto redo;
547 /* This means someone else dropped this page from LRU
548 * So, it will be freed or putback to LRU again. There is
549 * nothing to do here.
553 if (was_unevictable && lru != LRU_UNEVICTABLE)
554 count_vm_event(UNEVICTABLE_PGRESCUED);
555 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
556 count_vm_event(UNEVICTABLE_PGCULLED);
558 put_page(page); /* drop ref from isolate */
561 enum page_references {
562 PAGEREF_RECLAIM,
563 PAGEREF_RECLAIM_CLEAN,
564 PAGEREF_KEEP,
565 PAGEREF_ACTIVATE,
568 static enum page_references page_check_references(struct page *page,
569 struct scan_control *sc)
571 int referenced_ptes, referenced_page;
572 unsigned long vm_flags;
574 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
575 referenced_page = TestClearPageReferenced(page);
577 /* Lumpy reclaim - ignore references */
578 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
579 return PAGEREF_RECLAIM;
582 * Mlock lost the isolation race with us. Let try_to_unmap()
583 * move the page to the unevictable list.
585 if (vm_flags & VM_LOCKED)
586 return PAGEREF_RECLAIM;
588 if (referenced_ptes) {
589 if (PageAnon(page))
590 return PAGEREF_ACTIVATE;
592 * All mapped pages start out with page table
593 * references from the instantiating fault, so we need
594 * to look twice if a mapped file page is used more
595 * than once.
597 * Mark it and spare it for another trip around the
598 * inactive list. Another page table reference will
599 * lead to its activation.
601 * Note: the mark is set for activated pages as well
602 * so that recently deactivated but used pages are
603 * quickly recovered.
605 SetPageReferenced(page);
607 if (referenced_page)
608 return PAGEREF_ACTIVATE;
610 return PAGEREF_KEEP;
613 /* Reclaim if clean, defer dirty pages to writeback */
614 if (referenced_page)
615 return PAGEREF_RECLAIM_CLEAN;
617 return PAGEREF_RECLAIM;
621 * shrink_page_list() returns the number of reclaimed pages
623 static unsigned long shrink_page_list(struct list_head *page_list,
624 struct scan_control *sc,
625 enum pageout_io sync_writeback)
627 LIST_HEAD(ret_pages);
628 struct pagevec freed_pvec;
629 int pgactivate = 0;
630 unsigned long nr_reclaimed = 0;
632 cond_resched();
634 pagevec_init(&freed_pvec, 1);
635 while (!list_empty(page_list)) {
636 enum page_references references;
637 struct address_space *mapping;
638 struct page *page;
639 int may_enter_fs;
641 cond_resched();
643 page = lru_to_page(page_list);
644 list_del(&page->lru);
646 if (!trylock_page(page))
647 goto keep;
649 VM_BUG_ON(PageActive(page));
651 sc->nr_scanned++;
653 if (unlikely(!page_evictable(page, NULL)))
654 goto cull_mlocked;
656 if (!sc->may_unmap && page_mapped(page))
657 goto keep_locked;
659 /* Double the slab pressure for mapped and swapcache pages */
660 if (page_mapped(page) || PageSwapCache(page))
661 sc->nr_scanned++;
663 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
664 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
666 if (PageWriteback(page)) {
668 * Synchronous reclaim is performed in two passes,
669 * first an asynchronous pass over the list to
670 * start parallel writeback, and a second synchronous
671 * pass to wait for the IO to complete. Wait here
672 * for any page for which writeback has already
673 * started.
675 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
676 wait_on_page_writeback(page);
677 else
678 goto keep_locked;
681 references = page_check_references(page, sc);
682 switch (references) {
683 case PAGEREF_ACTIVATE:
684 goto activate_locked;
685 case PAGEREF_KEEP:
686 goto keep_locked;
687 case PAGEREF_RECLAIM:
688 case PAGEREF_RECLAIM_CLEAN:
689 ; /* try to reclaim the page below */
693 * Anonymous process memory has backing store?
694 * Try to allocate it some swap space here.
696 if (PageAnon(page) && !PageSwapCache(page)) {
697 if (!(sc->gfp_mask & __GFP_IO))
698 goto keep_locked;
699 if (!add_to_swap(page))
700 goto activate_locked;
701 may_enter_fs = 1;
704 mapping = page_mapping(page);
707 * The page is mapped into the page tables of one or more
708 * processes. Try to unmap it here.
710 if (page_mapped(page) && mapping) {
711 switch (try_to_unmap(page, TTU_UNMAP)) {
712 case SWAP_FAIL:
713 goto activate_locked;
714 case SWAP_AGAIN:
715 goto keep_locked;
716 case SWAP_MLOCK:
717 goto cull_mlocked;
718 case SWAP_SUCCESS:
719 ; /* try to free the page below */
723 if (PageDirty(page)) {
724 if (references == PAGEREF_RECLAIM_CLEAN)
725 goto keep_locked;
726 if (!may_enter_fs)
727 goto keep_locked;
728 if (!sc->may_writepage)
729 goto keep_locked;
731 /* Page is dirty, try to write it out here */
732 switch (pageout(page, mapping, sync_writeback)) {
733 case PAGE_KEEP:
734 goto keep_locked;
735 case PAGE_ACTIVATE:
736 goto activate_locked;
737 case PAGE_SUCCESS:
738 if (PageWriteback(page) || PageDirty(page))
739 goto keep;
741 * A synchronous write - probably a ramdisk. Go
742 * ahead and try to reclaim the page.
744 if (!trylock_page(page))
745 goto keep;
746 if (PageDirty(page) || PageWriteback(page))
747 goto keep_locked;
748 mapping = page_mapping(page);
749 case PAGE_CLEAN:
750 ; /* try to free the page below */
755 * If the page has buffers, try to free the buffer mappings
756 * associated with this page. If we succeed we try to free
757 * the page as well.
759 * We do this even if the page is PageDirty().
760 * try_to_release_page() does not perform I/O, but it is
761 * possible for a page to have PageDirty set, but it is actually
762 * clean (all its buffers are clean). This happens if the
763 * buffers were written out directly, with submit_bh(). ext3
764 * will do this, as well as the blockdev mapping.
765 * try_to_release_page() will discover that cleanness and will
766 * drop the buffers and mark the page clean - it can be freed.
768 * Rarely, pages can have buffers and no ->mapping. These are
769 * the pages which were not successfully invalidated in
770 * truncate_complete_page(). We try to drop those buffers here
771 * and if that worked, and the page is no longer mapped into
772 * process address space (page_count == 1) it can be freed.
773 * Otherwise, leave the page on the LRU so it is swappable.
775 if (page_has_private(page)) {
776 if (!try_to_release_page(page, sc->gfp_mask))
777 goto activate_locked;
778 if (!mapping && page_count(page) == 1) {
779 unlock_page(page);
780 if (put_page_testzero(page))
781 goto free_it;
782 else {
784 * rare race with speculative reference.
785 * the speculative reference will free
786 * this page shortly, so we may
787 * increment nr_reclaimed here (and
788 * leave it off the LRU).
790 nr_reclaimed++;
791 continue;
796 if (!mapping || !__remove_mapping(mapping, page))
797 goto keep_locked;
800 * At this point, we have no other references and there is
801 * no way to pick any more up (removed from LRU, removed
802 * from pagecache). Can use non-atomic bitops now (and
803 * we obviously don't have to worry about waking up a process
804 * waiting on the page lock, because there are no references.
806 __clear_page_locked(page);
807 free_it:
808 nr_reclaimed++;
809 if (!pagevec_add(&freed_pvec, page)) {
810 __pagevec_free(&freed_pvec);
811 pagevec_reinit(&freed_pvec);
813 continue;
815 cull_mlocked:
816 if (PageSwapCache(page))
817 try_to_free_swap(page);
818 unlock_page(page);
819 putback_lru_page(page);
820 continue;
822 activate_locked:
823 /* Not a candidate for swapping, so reclaim swap space. */
824 if (PageSwapCache(page) && vm_swap_full())
825 try_to_free_swap(page);
826 VM_BUG_ON(PageActive(page));
827 SetPageActive(page);
828 pgactivate++;
829 keep_locked:
830 unlock_page(page);
831 keep:
832 list_add(&page->lru, &ret_pages);
833 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
835 list_splice(&ret_pages, page_list);
836 if (pagevec_count(&freed_pvec))
837 __pagevec_free(&freed_pvec);
838 count_vm_events(PGACTIVATE, pgactivate);
839 return nr_reclaimed;
842 /* LRU Isolation modes. */
843 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
844 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
845 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
848 * Attempt to remove the specified page from its LRU. Only take this page
849 * if it is of the appropriate PageActive status. Pages which are being
850 * freed elsewhere are also ignored.
852 * page: page to consider
853 * mode: one of the LRU isolation modes defined above
855 * returns 0 on success, -ve errno on failure.
857 int __isolate_lru_page(struct page *page, int mode, int file)
859 int ret = -EINVAL;
861 /* Only take pages on the LRU. */
862 if (!PageLRU(page))
863 return ret;
866 * When checking the active state, we need to be sure we are
867 * dealing with comparible boolean values. Take the logical not
868 * of each.
870 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
871 return ret;
873 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
874 return ret;
877 * When this function is being called for lumpy reclaim, we
878 * initially look into all LRU pages, active, inactive and
879 * unevictable; only give shrink_page_list evictable pages.
881 if (PageUnevictable(page))
882 return ret;
884 ret = -EBUSY;
886 if (likely(get_page_unless_zero(page))) {
888 * Be careful not to clear PageLRU until after we're
889 * sure the page is not being freed elsewhere -- the
890 * page release code relies on it.
892 ClearPageLRU(page);
893 ret = 0;
896 return ret;
900 * zone->lru_lock is heavily contended. Some of the functions that
901 * shrink the lists perform better by taking out a batch of pages
902 * and working on them outside the LRU lock.
904 * For pagecache intensive workloads, this function is the hottest
905 * spot in the kernel (apart from copy_*_user functions).
907 * Appropriate locks must be held before calling this function.
909 * @nr_to_scan: The number of pages to look through on the list.
910 * @src: The LRU list to pull pages off.
911 * @dst: The temp list to put pages on to.
912 * @scanned: The number of pages that were scanned.
913 * @order: The caller's attempted allocation order
914 * @mode: One of the LRU isolation modes
915 * @file: True [1] if isolating file [!anon] pages
917 * returns how many pages were moved onto *@dst.
919 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
920 struct list_head *src, struct list_head *dst,
921 unsigned long *scanned, int order, int mode, int file)
923 unsigned long nr_taken = 0;
924 unsigned long scan;
926 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
927 struct page *page;
928 unsigned long pfn;
929 unsigned long end_pfn;
930 unsigned long page_pfn;
931 int zone_id;
933 page = lru_to_page(src);
934 prefetchw_prev_lru_page(page, src, flags);
936 VM_BUG_ON(!PageLRU(page));
938 switch (__isolate_lru_page(page, mode, file)) {
939 case 0:
940 list_move(&page->lru, dst);
941 mem_cgroup_del_lru(page);
942 nr_taken++;
943 break;
945 case -EBUSY:
946 /* else it is being freed elsewhere */
947 list_move(&page->lru, src);
948 mem_cgroup_rotate_lru_list(page, page_lru(page));
949 continue;
951 default:
952 BUG();
955 if (!order)
956 continue;
959 * Attempt to take all pages in the order aligned region
960 * surrounding the tag page. Only take those pages of
961 * the same active state as that tag page. We may safely
962 * round the target page pfn down to the requested order
963 * as the mem_map is guarenteed valid out to MAX_ORDER,
964 * where that page is in a different zone we will detect
965 * it from its zone id and abort this block scan.
967 zone_id = page_zone_id(page);
968 page_pfn = page_to_pfn(page);
969 pfn = page_pfn & ~((1 << order) - 1);
970 end_pfn = pfn + (1 << order);
971 for (; pfn < end_pfn; pfn++) {
972 struct page *cursor_page;
974 /* The target page is in the block, ignore it. */
975 if (unlikely(pfn == page_pfn))
976 continue;
978 /* Avoid holes within the zone. */
979 if (unlikely(!pfn_valid_within(pfn)))
980 break;
982 cursor_page = pfn_to_page(pfn);
984 /* Check that we have not crossed a zone boundary. */
985 if (unlikely(page_zone_id(cursor_page) != zone_id))
986 continue;
989 * If we don't have enough swap space, reclaiming of
990 * anon page which don't already have a swap slot is
991 * pointless.
993 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
994 !PageSwapCache(cursor_page))
995 continue;
997 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
998 list_move(&cursor_page->lru, dst);
999 mem_cgroup_del_lru(cursor_page);
1000 nr_taken++;
1001 scan++;
1006 *scanned = scan;
1007 return nr_taken;
1010 static unsigned long isolate_pages_global(unsigned long nr,
1011 struct list_head *dst,
1012 unsigned long *scanned, int order,
1013 int mode, struct zone *z,
1014 struct mem_cgroup *mem_cont,
1015 int active, int file)
1017 int lru = LRU_BASE;
1018 if (active)
1019 lru += LRU_ACTIVE;
1020 if (file)
1021 lru += LRU_FILE;
1022 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1023 mode, file);
1027 * clear_active_flags() is a helper for shrink_active_list(), clearing
1028 * any active bits from the pages in the list.
1030 static unsigned long clear_active_flags(struct list_head *page_list,
1031 unsigned int *count)
1033 int nr_active = 0;
1034 int lru;
1035 struct page *page;
1037 list_for_each_entry(page, page_list, lru) {
1038 lru = page_lru_base_type(page);
1039 if (PageActive(page)) {
1040 lru += LRU_ACTIVE;
1041 ClearPageActive(page);
1042 nr_active++;
1044 count[lru]++;
1047 return nr_active;
1051 * isolate_lru_page - tries to isolate a page from its LRU list
1052 * @page: page to isolate from its LRU list
1054 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1055 * vmstat statistic corresponding to whatever LRU list the page was on.
1057 * Returns 0 if the page was removed from an LRU list.
1058 * Returns -EBUSY if the page was not on an LRU list.
1060 * The returned page will have PageLRU() cleared. If it was found on
1061 * the active list, it will have PageActive set. If it was found on
1062 * the unevictable list, it will have the PageUnevictable bit set. That flag
1063 * may need to be cleared by the caller before letting the page go.
1065 * The vmstat statistic corresponding to the list on which the page was
1066 * found will be decremented.
1068 * Restrictions:
1069 * (1) Must be called with an elevated refcount on the page. This is a
1070 * fundamentnal difference from isolate_lru_pages (which is called
1071 * without a stable reference).
1072 * (2) the lru_lock must not be held.
1073 * (3) interrupts must be enabled.
1075 int isolate_lru_page(struct page *page)
1077 int ret = -EBUSY;
1079 if (PageLRU(page)) {
1080 struct zone *zone = page_zone(page);
1082 spin_lock_irq(&zone->lru_lock);
1083 if (PageLRU(page) && get_page_unless_zero(page)) {
1084 int lru = page_lru(page);
1085 ret = 0;
1086 ClearPageLRU(page);
1088 del_page_from_lru_list(zone, page, lru);
1090 spin_unlock_irq(&zone->lru_lock);
1092 return ret;
1096 * Are there way too many processes in the direct reclaim path already?
1098 static int too_many_isolated(struct zone *zone, int file,
1099 struct scan_control *sc)
1101 unsigned long inactive, isolated;
1103 if (current_is_kswapd())
1104 return 0;
1106 if (!scanning_global_lru(sc))
1107 return 0;
1109 if (file) {
1110 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1111 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1112 } else {
1113 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1114 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1117 return isolated > inactive;
1121 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1122 * of reclaimed pages
1124 static unsigned long shrink_inactive_list(unsigned long max_scan,
1125 struct zone *zone, struct scan_control *sc,
1126 int priority, int file)
1128 LIST_HEAD(page_list);
1129 struct pagevec pvec;
1130 unsigned long nr_scanned = 0;
1131 unsigned long nr_reclaimed = 0;
1132 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1133 int lumpy_reclaim = 0;
1135 while (unlikely(too_many_isolated(zone, file, sc))) {
1136 congestion_wait(BLK_RW_ASYNC, HZ/10);
1138 /* We are about to die and free our memory. Return now. */
1139 if (fatal_signal_pending(current))
1140 return SWAP_CLUSTER_MAX;
1144 * If we need a large contiguous chunk of memory, or have
1145 * trouble getting a small set of contiguous pages, we
1146 * will reclaim both active and inactive pages.
1148 * We use the same threshold as pageout congestion_wait below.
1150 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1151 lumpy_reclaim = 1;
1152 else if (sc->order && priority < DEF_PRIORITY - 2)
1153 lumpy_reclaim = 1;
1155 pagevec_init(&pvec, 1);
1157 lru_add_drain();
1158 spin_lock_irq(&zone->lru_lock);
1159 do {
1160 struct page *page;
1161 unsigned long nr_taken;
1162 unsigned long nr_scan;
1163 unsigned long nr_freed;
1164 unsigned long nr_active;
1165 unsigned int count[NR_LRU_LISTS] = { 0, };
1166 int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
1167 unsigned long nr_anon;
1168 unsigned long nr_file;
1170 nr_taken = sc->isolate_pages(SWAP_CLUSTER_MAX,
1171 &page_list, &nr_scan, sc->order, mode,
1172 zone, sc->mem_cgroup, 0, file);
1174 if (scanning_global_lru(sc)) {
1175 zone->pages_scanned += nr_scan;
1176 if (current_is_kswapd())
1177 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1178 nr_scan);
1179 else
1180 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1181 nr_scan);
1184 if (nr_taken == 0)
1185 goto done;
1187 nr_active = clear_active_flags(&page_list, count);
1188 __count_vm_events(PGDEACTIVATE, nr_active);
1190 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1191 -count[LRU_ACTIVE_FILE]);
1192 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1193 -count[LRU_INACTIVE_FILE]);
1194 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1195 -count[LRU_ACTIVE_ANON]);
1196 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1197 -count[LRU_INACTIVE_ANON]);
1199 nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1200 nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1201 __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
1202 __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
1204 reclaim_stat->recent_scanned[0] += nr_anon;
1205 reclaim_stat->recent_scanned[1] += nr_file;
1207 spin_unlock_irq(&zone->lru_lock);
1209 nr_scanned += nr_scan;
1210 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1213 * If we are direct reclaiming for contiguous pages and we do
1214 * not reclaim everything in the list, try again and wait
1215 * for IO to complete. This will stall high-order allocations
1216 * but that should be acceptable to the caller
1218 if (nr_freed < nr_taken && !current_is_kswapd() &&
1219 lumpy_reclaim) {
1220 congestion_wait(BLK_RW_ASYNC, HZ/10);
1223 * The attempt at page out may have made some
1224 * of the pages active, mark them inactive again.
1226 nr_active = clear_active_flags(&page_list, count);
1227 count_vm_events(PGDEACTIVATE, nr_active);
1229 nr_freed += shrink_page_list(&page_list, sc,
1230 PAGEOUT_IO_SYNC);
1233 nr_reclaimed += nr_freed;
1235 local_irq_disable();
1236 if (current_is_kswapd())
1237 __count_vm_events(KSWAPD_STEAL, nr_freed);
1238 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1240 spin_lock(&zone->lru_lock);
1242 * Put back any unfreeable pages.
1244 while (!list_empty(&page_list)) {
1245 int lru;
1246 page = lru_to_page(&page_list);
1247 VM_BUG_ON(PageLRU(page));
1248 list_del(&page->lru);
1249 if (unlikely(!page_evictable(page, NULL))) {
1250 spin_unlock_irq(&zone->lru_lock);
1251 putback_lru_page(page);
1252 spin_lock_irq(&zone->lru_lock);
1253 continue;
1255 SetPageLRU(page);
1256 lru = page_lru(page);
1257 add_page_to_lru_list(zone, page, lru);
1258 if (is_active_lru(lru)) {
1259 int file = is_file_lru(lru);
1260 reclaim_stat->recent_rotated[file]++;
1262 if (!pagevec_add(&pvec, page)) {
1263 spin_unlock_irq(&zone->lru_lock);
1264 __pagevec_release(&pvec);
1265 spin_lock_irq(&zone->lru_lock);
1268 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1269 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1271 } while (nr_scanned < max_scan);
1273 done:
1274 spin_unlock_irq(&zone->lru_lock);
1275 pagevec_release(&pvec);
1276 return nr_reclaimed;
1280 * We are about to scan this zone at a certain priority level. If that priority
1281 * level is smaller (ie: more urgent) than the previous priority, then note
1282 * that priority level within the zone. This is done so that when the next
1283 * process comes in to scan this zone, it will immediately start out at this
1284 * priority level rather than having to build up its own scanning priority.
1285 * Here, this priority affects only the reclaim-mapped threshold.
1287 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1289 if (priority < zone->prev_priority)
1290 zone->prev_priority = priority;
1294 * This moves pages from the active list to the inactive list.
1296 * We move them the other way if the page is referenced by one or more
1297 * processes, from rmap.
1299 * If the pages are mostly unmapped, the processing is fast and it is
1300 * appropriate to hold zone->lru_lock across the whole operation. But if
1301 * the pages are mapped, the processing is slow (page_referenced()) so we
1302 * should drop zone->lru_lock around each page. It's impossible to balance
1303 * this, so instead we remove the pages from the LRU while processing them.
1304 * It is safe to rely on PG_active against the non-LRU pages in here because
1305 * nobody will play with that bit on a non-LRU page.
1307 * The downside is that we have to touch page->_count against each page.
1308 * But we had to alter page->flags anyway.
1311 static void move_active_pages_to_lru(struct zone *zone,
1312 struct list_head *list,
1313 enum lru_list lru)
1315 unsigned long pgmoved = 0;
1316 struct pagevec pvec;
1317 struct page *page;
1319 pagevec_init(&pvec, 1);
1321 while (!list_empty(list)) {
1322 page = lru_to_page(list);
1324 VM_BUG_ON(PageLRU(page));
1325 SetPageLRU(page);
1327 list_move(&page->lru, &zone->lru[lru].list);
1328 mem_cgroup_add_lru_list(page, lru);
1329 pgmoved++;
1331 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1332 spin_unlock_irq(&zone->lru_lock);
1333 if (buffer_heads_over_limit)
1334 pagevec_strip(&pvec);
1335 __pagevec_release(&pvec);
1336 spin_lock_irq(&zone->lru_lock);
1339 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1340 if (!is_active_lru(lru))
1341 __count_vm_events(PGDEACTIVATE, pgmoved);
1344 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1345 struct scan_control *sc, int priority, int file)
1347 unsigned long nr_taken;
1348 unsigned long pgscanned;
1349 unsigned long vm_flags;
1350 LIST_HEAD(l_hold); /* The pages which were snipped off */
1351 LIST_HEAD(l_active);
1352 LIST_HEAD(l_inactive);
1353 struct page *page;
1354 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1355 unsigned long nr_rotated = 0;
1357 lru_add_drain();
1358 spin_lock_irq(&zone->lru_lock);
1359 nr_taken = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1360 ISOLATE_ACTIVE, zone,
1361 sc->mem_cgroup, 1, file);
1363 * zone->pages_scanned is used for detect zone's oom
1364 * mem_cgroup remembers nr_scan by itself.
1366 if (scanning_global_lru(sc)) {
1367 zone->pages_scanned += pgscanned;
1369 reclaim_stat->recent_scanned[file] += nr_taken;
1371 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1372 if (file)
1373 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1374 else
1375 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1376 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1377 spin_unlock_irq(&zone->lru_lock);
1379 while (!list_empty(&l_hold)) {
1380 cond_resched();
1381 page = lru_to_page(&l_hold);
1382 list_del(&page->lru);
1384 if (unlikely(!page_evictable(page, NULL))) {
1385 putback_lru_page(page);
1386 continue;
1389 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1390 nr_rotated++;
1392 * Identify referenced, file-backed active pages and
1393 * give them one more trip around the active list. So
1394 * that executable code get better chances to stay in
1395 * memory under moderate memory pressure. Anon pages
1396 * are not likely to be evicted by use-once streaming
1397 * IO, plus JVM can create lots of anon VM_EXEC pages,
1398 * so we ignore them here.
1400 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1401 list_add(&page->lru, &l_active);
1402 continue;
1406 ClearPageActive(page); /* we are de-activating */
1407 list_add(&page->lru, &l_inactive);
1411 * Move pages back to the lru list.
1413 spin_lock_irq(&zone->lru_lock);
1415 * Count referenced pages from currently used mappings as rotated,
1416 * even though only some of them are actually re-activated. This
1417 * helps balance scan pressure between file and anonymous pages in
1418 * get_scan_ratio.
1420 reclaim_stat->recent_rotated[file] += nr_rotated;
1422 move_active_pages_to_lru(zone, &l_active,
1423 LRU_ACTIVE + file * LRU_FILE);
1424 move_active_pages_to_lru(zone, &l_inactive,
1425 LRU_BASE + file * LRU_FILE);
1426 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1427 spin_unlock_irq(&zone->lru_lock);
1430 static int inactive_anon_is_low_global(struct zone *zone)
1432 unsigned long active, inactive;
1434 active = zone_page_state(zone, NR_ACTIVE_ANON);
1435 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1437 if (inactive * zone->inactive_ratio < active)
1438 return 1;
1440 return 0;
1444 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1445 * @zone: zone to check
1446 * @sc: scan control of this context
1448 * Returns true if the zone does not have enough inactive anon pages,
1449 * meaning some active anon pages need to be deactivated.
1451 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1453 int low;
1455 if (scanning_global_lru(sc))
1456 low = inactive_anon_is_low_global(zone);
1457 else
1458 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1459 return low;
1462 static int inactive_file_is_low_global(struct zone *zone)
1464 unsigned long active, inactive;
1466 active = zone_page_state(zone, NR_ACTIVE_FILE);
1467 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1469 return (active > inactive);
1473 * inactive_file_is_low - check if file pages need to be deactivated
1474 * @zone: zone to check
1475 * @sc: scan control of this context
1477 * When the system is doing streaming IO, memory pressure here
1478 * ensures that active file pages get deactivated, until more
1479 * than half of the file pages are on the inactive list.
1481 * Once we get to that situation, protect the system's working
1482 * set from being evicted by disabling active file page aging.
1484 * This uses a different ratio than the anonymous pages, because
1485 * the page cache uses a use-once replacement algorithm.
1487 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1489 int low;
1491 if (scanning_global_lru(sc))
1492 low = inactive_file_is_low_global(zone);
1493 else
1494 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1495 return low;
1498 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1499 int file)
1501 if (file)
1502 return inactive_file_is_low(zone, sc);
1503 else
1504 return inactive_anon_is_low(zone, sc);
1507 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1508 struct zone *zone, struct scan_control *sc, int priority)
1510 int file = is_file_lru(lru);
1512 if (is_active_lru(lru)) {
1513 if (inactive_list_is_low(zone, sc, file))
1514 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1515 return 0;
1518 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1522 * Determine how aggressively the anon and file LRU lists should be
1523 * scanned. The relative value of each set of LRU lists is determined
1524 * by looking at the fraction of the pages scanned we did rotate back
1525 * onto the active list instead of evict.
1527 * percent[0] specifies how much pressure to put on ram/swap backed
1528 * memory, while percent[1] determines pressure on the file LRUs.
1530 static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1531 unsigned long *percent)
1533 unsigned long anon, file, free;
1534 unsigned long anon_prio, file_prio;
1535 unsigned long ap, fp;
1536 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1538 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1539 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1540 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1541 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1543 if (scanning_global_lru(sc)) {
1544 free = zone_page_state(zone, NR_FREE_PAGES);
1545 /* If we have very few page cache pages,
1546 force-scan anon pages. */
1547 if (unlikely(file + free <= high_wmark_pages(zone))) {
1548 percent[0] = 100;
1549 percent[1] = 0;
1550 return;
1555 * OK, so we have swap space and a fair amount of page cache
1556 * pages. We use the recently rotated / recently scanned
1557 * ratios to determine how valuable each cache is.
1559 * Because workloads change over time (and to avoid overflow)
1560 * we keep these statistics as a floating average, which ends
1561 * up weighing recent references more than old ones.
1563 * anon in [0], file in [1]
1565 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1566 spin_lock_irq(&zone->lru_lock);
1567 reclaim_stat->recent_scanned[0] /= 2;
1568 reclaim_stat->recent_rotated[0] /= 2;
1569 spin_unlock_irq(&zone->lru_lock);
1572 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1573 spin_lock_irq(&zone->lru_lock);
1574 reclaim_stat->recent_scanned[1] /= 2;
1575 reclaim_stat->recent_rotated[1] /= 2;
1576 spin_unlock_irq(&zone->lru_lock);
1580 * With swappiness at 100, anonymous and file have the same priority.
1581 * This scanning priority is essentially the inverse of IO cost.
1583 anon_prio = sc->swappiness;
1584 file_prio = 200 - sc->swappiness;
1587 * The amount of pressure on anon vs file pages is inversely
1588 * proportional to the fraction of recently scanned pages on
1589 * each list that were recently referenced and in active use.
1591 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1592 ap /= reclaim_stat->recent_rotated[0] + 1;
1594 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1595 fp /= reclaim_stat->recent_rotated[1] + 1;
1597 /* Normalize to percentages */
1598 percent[0] = 100 * ap / (ap + fp + 1);
1599 percent[1] = 100 - percent[0];
1603 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1604 * until we collected @swap_cluster_max pages to scan.
1606 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
1607 unsigned long *nr_saved_scan)
1609 unsigned long nr;
1611 *nr_saved_scan += nr_to_scan;
1612 nr = *nr_saved_scan;
1614 if (nr >= SWAP_CLUSTER_MAX)
1615 *nr_saved_scan = 0;
1616 else
1617 nr = 0;
1619 return nr;
1623 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1625 static void shrink_zone(int priority, struct zone *zone,
1626 struct scan_control *sc)
1628 unsigned long nr[NR_LRU_LISTS];
1629 unsigned long nr_to_scan;
1630 unsigned long percent[2]; /* anon @ 0; file @ 1 */
1631 enum lru_list l;
1632 unsigned long nr_reclaimed = sc->nr_reclaimed;
1633 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1634 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1635 int noswap = 0;
1637 /* If we have no swap space, do not bother scanning anon pages. */
1638 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1639 noswap = 1;
1640 percent[0] = 0;
1641 percent[1] = 100;
1642 } else
1643 get_scan_ratio(zone, sc, percent);
1645 for_each_evictable_lru(l) {
1646 int file = is_file_lru(l);
1647 unsigned long scan;
1649 scan = zone_nr_lru_pages(zone, sc, l);
1650 if (priority || noswap) {
1651 scan >>= priority;
1652 scan = (scan * percent[file]) / 100;
1654 nr[l] = nr_scan_try_batch(scan,
1655 &reclaim_stat->nr_saved_scan[l]);
1658 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1659 nr[LRU_INACTIVE_FILE]) {
1660 for_each_evictable_lru(l) {
1661 if (nr[l]) {
1662 nr_to_scan = min_t(unsigned long,
1663 nr[l], SWAP_CLUSTER_MAX);
1664 nr[l] -= nr_to_scan;
1666 nr_reclaimed += shrink_list(l, nr_to_scan,
1667 zone, sc, priority);
1671 * On large memory systems, scan >> priority can become
1672 * really large. This is fine for the starting priority;
1673 * we want to put equal scanning pressure on each zone.
1674 * However, if the VM has a harder time of freeing pages,
1675 * with multiple processes reclaiming pages, the total
1676 * freeing target can get unreasonably large.
1678 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1679 break;
1682 sc->nr_reclaimed = nr_reclaimed;
1685 * Even if we did not try to evict anon pages at all, we want to
1686 * rebalance the anon lru active/inactive ratio.
1688 if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
1689 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1691 throttle_vm_writeout(sc->gfp_mask);
1695 * This is the direct reclaim path, for page-allocating processes. We only
1696 * try to reclaim pages from zones which will satisfy the caller's allocation
1697 * request.
1699 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1700 * Because:
1701 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1702 * allocation or
1703 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1704 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1705 * zone defense algorithm.
1707 * If a zone is deemed to be full of pinned pages then just give it a light
1708 * scan then give up on it.
1710 static void shrink_zones(int priority, struct zonelist *zonelist,
1711 struct scan_control *sc)
1713 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1714 struct zoneref *z;
1715 struct zone *zone;
1717 sc->all_unreclaimable = 1;
1718 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1719 sc->nodemask) {
1720 if (!populated_zone(zone))
1721 continue;
1723 * Take care memory controller reclaiming has small influence
1724 * to global LRU.
1726 if (scanning_global_lru(sc)) {
1727 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1728 continue;
1729 note_zone_scanning_priority(zone, priority);
1731 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1732 continue; /* Let kswapd poll it */
1733 sc->all_unreclaimable = 0;
1734 } else {
1736 * Ignore cpuset limitation here. We just want to reduce
1737 * # of used pages by us regardless of memory shortage.
1739 sc->all_unreclaimable = 0;
1740 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1741 priority);
1744 shrink_zone(priority, zone, sc);
1749 * This is the main entry point to direct page reclaim.
1751 * If a full scan of the inactive list fails to free enough memory then we
1752 * are "out of memory" and something needs to be killed.
1754 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1755 * high - the zone may be full of dirty or under-writeback pages, which this
1756 * caller can't do much about. We kick the writeback threads and take explicit
1757 * naps in the hope that some of these pages can be written. But if the
1758 * allocating task holds filesystem locks which prevent writeout this might not
1759 * work, and the allocation attempt will fail.
1761 * returns: 0, if no pages reclaimed
1762 * else, the number of pages reclaimed
1764 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1765 struct scan_control *sc)
1767 int priority;
1768 unsigned long ret = 0;
1769 unsigned long total_scanned = 0;
1770 struct reclaim_state *reclaim_state = current->reclaim_state;
1771 unsigned long lru_pages = 0;
1772 struct zoneref *z;
1773 struct zone *zone;
1774 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1775 unsigned long writeback_threshold;
1777 delayacct_freepages_start();
1779 if (scanning_global_lru(sc))
1780 count_vm_event(ALLOCSTALL);
1782 * mem_cgroup will not do shrink_slab.
1784 if (scanning_global_lru(sc)) {
1785 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1787 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1788 continue;
1790 lru_pages += zone_reclaimable_pages(zone);
1794 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1795 sc->nr_scanned = 0;
1796 if (!priority)
1797 disable_swap_token();
1798 shrink_zones(priority, zonelist, sc);
1800 * Don't shrink slabs when reclaiming memory from
1801 * over limit cgroups
1803 if (scanning_global_lru(sc)) {
1804 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1805 if (reclaim_state) {
1806 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1807 reclaim_state->reclaimed_slab = 0;
1810 total_scanned += sc->nr_scanned;
1811 if (sc->nr_reclaimed >= sc->nr_to_reclaim) {
1812 ret = sc->nr_reclaimed;
1813 goto out;
1817 * Try to write back as many pages as we just scanned. This
1818 * tends to cause slow streaming writers to write data to the
1819 * disk smoothly, at the dirtying rate, which is nice. But
1820 * that's undesirable in laptop mode, where we *want* lumpy
1821 * writeout. So in laptop mode, write out the whole world.
1823 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
1824 if (total_scanned > writeback_threshold) {
1825 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
1826 sc->may_writepage = 1;
1829 /* Take a nap, wait for some writeback to complete */
1830 if (!sc->hibernation_mode && sc->nr_scanned &&
1831 priority < DEF_PRIORITY - 2)
1832 congestion_wait(BLK_RW_ASYNC, HZ/10);
1834 /* top priority shrink_zones still had more to do? don't OOM, then */
1835 if (!sc->all_unreclaimable && scanning_global_lru(sc))
1836 ret = sc->nr_reclaimed;
1837 out:
1839 * Now that we've scanned all the zones at this priority level, note
1840 * that level within the zone so that the next thread which performs
1841 * scanning of this zone will immediately start out at this priority
1842 * level. This affects only the decision whether or not to bring
1843 * mapped pages onto the inactive list.
1845 if (priority < 0)
1846 priority = 0;
1848 if (scanning_global_lru(sc)) {
1849 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1851 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1852 continue;
1854 zone->prev_priority = priority;
1856 } else
1857 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1859 delayacct_freepages_end();
1861 return ret;
1864 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1865 gfp_t gfp_mask, nodemask_t *nodemask)
1867 struct scan_control sc = {
1868 .gfp_mask = gfp_mask,
1869 .may_writepage = !laptop_mode,
1870 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1871 .may_unmap = 1,
1872 .may_swap = 1,
1873 .swappiness = vm_swappiness,
1874 .order = order,
1875 .mem_cgroup = NULL,
1876 .isolate_pages = isolate_pages_global,
1877 .nodemask = nodemask,
1880 return do_try_to_free_pages(zonelist, &sc);
1883 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1885 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
1886 gfp_t gfp_mask, bool noswap,
1887 unsigned int swappiness,
1888 struct zone *zone, int nid)
1890 struct scan_control sc = {
1891 .may_writepage = !laptop_mode,
1892 .may_unmap = 1,
1893 .may_swap = !noswap,
1894 .swappiness = swappiness,
1895 .order = 0,
1896 .mem_cgroup = mem,
1897 .isolate_pages = mem_cgroup_isolate_pages,
1899 nodemask_t nm = nodemask_of_node(nid);
1901 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1902 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1903 sc.nodemask = &nm;
1904 sc.nr_reclaimed = 0;
1905 sc.nr_scanned = 0;
1907 * NOTE: Although we can get the priority field, using it
1908 * here is not a good idea, since it limits the pages we can scan.
1909 * if we don't reclaim here, the shrink_zone from balance_pgdat
1910 * will pick up pages from other mem cgroup's as well. We hack
1911 * the priority and make it zero.
1913 shrink_zone(0, zone, &sc);
1914 return sc.nr_reclaimed;
1917 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1918 gfp_t gfp_mask,
1919 bool noswap,
1920 unsigned int swappiness)
1922 struct zonelist *zonelist;
1923 struct scan_control sc = {
1924 .may_writepage = !laptop_mode,
1925 .may_unmap = 1,
1926 .may_swap = !noswap,
1927 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1928 .swappiness = swappiness,
1929 .order = 0,
1930 .mem_cgroup = mem_cont,
1931 .isolate_pages = mem_cgroup_isolate_pages,
1932 .nodemask = NULL, /* we don't care the placement */
1935 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1936 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1937 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1938 return do_try_to_free_pages(zonelist, &sc);
1940 #endif
1942 /* is kswapd sleeping prematurely? */
1943 static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
1945 int i;
1947 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
1948 if (remaining)
1949 return 1;
1951 /* If after HZ/10, a zone is below the high mark, it's premature */
1952 for (i = 0; i < pgdat->nr_zones; i++) {
1953 struct zone *zone = pgdat->node_zones + i;
1955 if (!populated_zone(zone))
1956 continue;
1958 if (zone->all_unreclaimable)
1959 continue;
1961 if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
1962 0, 0))
1963 return 1;
1966 return 0;
1970 * For kswapd, balance_pgdat() will work across all this node's zones until
1971 * they are all at high_wmark_pages(zone).
1973 * Returns the number of pages which were actually freed.
1975 * There is special handling here for zones which are full of pinned pages.
1976 * This can happen if the pages are all mlocked, or if they are all used by
1977 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1978 * What we do is to detect the case where all pages in the zone have been
1979 * scanned twice and there has been zero successful reclaim. Mark the zone as
1980 * dead and from now on, only perform a short scan. Basically we're polling
1981 * the zone for when the problem goes away.
1983 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1984 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
1985 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
1986 * lower zones regardless of the number of free pages in the lower zones. This
1987 * interoperates with the page allocator fallback scheme to ensure that aging
1988 * of pages is balanced across the zones.
1990 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1992 int all_zones_ok;
1993 int priority;
1994 int i;
1995 unsigned long total_scanned;
1996 struct reclaim_state *reclaim_state = current->reclaim_state;
1997 struct scan_control sc = {
1998 .gfp_mask = GFP_KERNEL,
1999 .may_unmap = 1,
2000 .may_swap = 1,
2002 * kswapd doesn't want to be bailed out while reclaim. because
2003 * we want to put equal scanning pressure on each zone.
2005 .nr_to_reclaim = ULONG_MAX,
2006 .swappiness = vm_swappiness,
2007 .order = order,
2008 .mem_cgroup = NULL,
2009 .isolate_pages = isolate_pages_global,
2012 * temp_priority is used to remember the scanning priority at which
2013 * this zone was successfully refilled to
2014 * free_pages == high_wmark_pages(zone).
2016 int temp_priority[MAX_NR_ZONES];
2018 loop_again:
2019 total_scanned = 0;
2020 sc.nr_reclaimed = 0;
2021 sc.may_writepage = !laptop_mode;
2022 count_vm_event(PAGEOUTRUN);
2024 for (i = 0; i < pgdat->nr_zones; i++)
2025 temp_priority[i] = DEF_PRIORITY;
2027 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2028 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2029 unsigned long lru_pages = 0;
2030 int has_under_min_watermark_zone = 0;
2032 /* The swap token gets in the way of swapout... */
2033 if (!priority)
2034 disable_swap_token();
2036 all_zones_ok = 1;
2039 * Scan in the highmem->dma direction for the highest
2040 * zone which needs scanning
2042 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2043 struct zone *zone = pgdat->node_zones + i;
2045 if (!populated_zone(zone))
2046 continue;
2048 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2049 continue;
2052 * Do some background aging of the anon list, to give
2053 * pages a chance to be referenced before reclaiming.
2055 if (inactive_anon_is_low(zone, &sc))
2056 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2057 &sc, priority, 0);
2059 if (!zone_watermark_ok(zone, order,
2060 high_wmark_pages(zone), 0, 0)) {
2061 end_zone = i;
2062 break;
2065 if (i < 0)
2066 goto out;
2068 for (i = 0; i <= end_zone; i++) {
2069 struct zone *zone = pgdat->node_zones + i;
2071 lru_pages += zone_reclaimable_pages(zone);
2075 * Now scan the zone in the dma->highmem direction, stopping
2076 * at the last zone which needs scanning.
2078 * We do this because the page allocator works in the opposite
2079 * direction. This prevents the page allocator from allocating
2080 * pages behind kswapd's direction of progress, which would
2081 * cause too much scanning of the lower zones.
2083 for (i = 0; i <= end_zone; i++) {
2084 struct zone *zone = pgdat->node_zones + i;
2085 int nr_slab;
2086 int nid, zid;
2088 if (!populated_zone(zone))
2089 continue;
2091 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2092 continue;
2094 temp_priority[i] = priority;
2095 sc.nr_scanned = 0;
2096 note_zone_scanning_priority(zone, priority);
2098 nid = pgdat->node_id;
2099 zid = zone_idx(zone);
2101 * Call soft limit reclaim before calling shrink_zone.
2102 * For now we ignore the return value
2104 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask,
2105 nid, zid);
2107 * We put equal pressure on every zone, unless one
2108 * zone has way too many pages free already.
2110 if (!zone_watermark_ok(zone, order,
2111 8*high_wmark_pages(zone), end_zone, 0))
2112 shrink_zone(priority, zone, &sc);
2113 reclaim_state->reclaimed_slab = 0;
2114 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
2115 lru_pages);
2116 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2117 total_scanned += sc.nr_scanned;
2118 if (zone->all_unreclaimable)
2119 continue;
2120 if (nr_slab == 0 &&
2121 zone->pages_scanned >= (zone_reclaimable_pages(zone) * 6))
2122 zone->all_unreclaimable = 1;
2124 * If we've done a decent amount of scanning and
2125 * the reclaim ratio is low, start doing writepage
2126 * even in laptop mode
2128 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2129 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2130 sc.may_writepage = 1;
2132 if (!zone_watermark_ok(zone, order,
2133 high_wmark_pages(zone), end_zone, 0)) {
2134 all_zones_ok = 0;
2136 * We are still under min water mark. This
2137 * means that we have a GFP_ATOMIC allocation
2138 * failure risk. Hurry up!
2140 if (!zone_watermark_ok(zone, order,
2141 min_wmark_pages(zone), end_zone, 0))
2142 has_under_min_watermark_zone = 1;
2146 if (all_zones_ok)
2147 break; /* kswapd: all done */
2149 * OK, kswapd is getting into trouble. Take a nap, then take
2150 * another pass across the zones.
2152 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2153 if (has_under_min_watermark_zone)
2154 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2155 else
2156 congestion_wait(BLK_RW_ASYNC, HZ/10);
2160 * We do this so kswapd doesn't build up large priorities for
2161 * example when it is freeing in parallel with allocators. It
2162 * matches the direct reclaim path behaviour in terms of impact
2163 * on zone->*_priority.
2165 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2166 break;
2168 out:
2170 * Note within each zone the priority level at which this zone was
2171 * brought into a happy state. So that the next thread which scans this
2172 * zone will start out at that priority level.
2174 for (i = 0; i < pgdat->nr_zones; i++) {
2175 struct zone *zone = pgdat->node_zones + i;
2177 zone->prev_priority = temp_priority[i];
2179 if (!all_zones_ok) {
2180 cond_resched();
2182 try_to_freeze();
2185 * Fragmentation may mean that the system cannot be
2186 * rebalanced for high-order allocations in all zones.
2187 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2188 * it means the zones have been fully scanned and are still
2189 * not balanced. For high-order allocations, there is
2190 * little point trying all over again as kswapd may
2191 * infinite loop.
2193 * Instead, recheck all watermarks at order-0 as they
2194 * are the most important. If watermarks are ok, kswapd will go
2195 * back to sleep. High-order users can still perform direct
2196 * reclaim if they wish.
2198 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2199 order = sc.order = 0;
2201 goto loop_again;
2204 return sc.nr_reclaimed;
2208 * The background pageout daemon, started as a kernel thread
2209 * from the init process.
2211 * This basically trickles out pages so that we have _some_
2212 * free memory available even if there is no other activity
2213 * that frees anything up. This is needed for things like routing
2214 * etc, where we otherwise might have all activity going on in
2215 * asynchronous contexts that cannot page things out.
2217 * If there are applications that are active memory-allocators
2218 * (most normal use), this basically shouldn't matter.
2220 static int kswapd(void *p)
2222 unsigned long order;
2223 pg_data_t *pgdat = (pg_data_t*)p;
2224 struct task_struct *tsk = current;
2225 DEFINE_WAIT(wait);
2226 struct reclaim_state reclaim_state = {
2227 .reclaimed_slab = 0,
2229 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2231 lockdep_set_current_reclaim_state(GFP_KERNEL);
2233 if (!cpumask_empty(cpumask))
2234 set_cpus_allowed_ptr(tsk, cpumask);
2235 current->reclaim_state = &reclaim_state;
2238 * Tell the memory management that we're a "memory allocator",
2239 * and that if we need more memory we should get access to it
2240 * regardless (see "__alloc_pages()"). "kswapd" should
2241 * never get caught in the normal page freeing logic.
2243 * (Kswapd normally doesn't need memory anyway, but sometimes
2244 * you need a small amount of memory in order to be able to
2245 * page out something else, and this flag essentially protects
2246 * us from recursively trying to free more memory as we're
2247 * trying to free the first piece of memory in the first place).
2249 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2250 set_freezable();
2252 order = 0;
2253 for ( ; ; ) {
2254 unsigned long new_order;
2255 int ret;
2257 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2258 new_order = pgdat->kswapd_max_order;
2259 pgdat->kswapd_max_order = 0;
2260 if (order < new_order) {
2262 * Don't sleep if someone wants a larger 'order'
2263 * allocation
2265 order = new_order;
2266 } else {
2267 if (!freezing(current) && !kthread_should_stop()) {
2268 long remaining = 0;
2270 /* Try to sleep for a short interval */
2271 if (!sleeping_prematurely(pgdat, order, remaining)) {
2272 remaining = schedule_timeout(HZ/10);
2273 finish_wait(&pgdat->kswapd_wait, &wait);
2274 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2278 * After a short sleep, check if it was a
2279 * premature sleep. If not, then go fully
2280 * to sleep until explicitly woken up
2282 if (!sleeping_prematurely(pgdat, order, remaining))
2283 schedule();
2284 else {
2285 if (remaining)
2286 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2287 else
2288 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2292 order = pgdat->kswapd_max_order;
2294 finish_wait(&pgdat->kswapd_wait, &wait);
2296 ret = try_to_freeze();
2297 if (kthread_should_stop())
2298 break;
2301 * We can speed up thawing tasks if we don't call balance_pgdat
2302 * after returning from the refrigerator
2304 if (!ret)
2305 balance_pgdat(pgdat, order);
2307 return 0;
2311 * A zone is low on free memory, so wake its kswapd task to service it.
2313 void wakeup_kswapd(struct zone *zone, int order)
2315 pg_data_t *pgdat;
2317 if (!populated_zone(zone))
2318 return;
2320 pgdat = zone->zone_pgdat;
2321 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
2322 return;
2323 if (pgdat->kswapd_max_order < order)
2324 pgdat->kswapd_max_order = order;
2325 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2326 return;
2327 if (!waitqueue_active(&pgdat->kswapd_wait))
2328 return;
2329 wake_up_interruptible(&pgdat->kswapd_wait);
2333 * The reclaimable count would be mostly accurate.
2334 * The less reclaimable pages may be
2335 * - mlocked pages, which will be moved to unevictable list when encountered
2336 * - mapped pages, which may require several travels to be reclaimed
2337 * - dirty pages, which is not "instantly" reclaimable
2339 unsigned long global_reclaimable_pages(void)
2341 int nr;
2343 nr = global_page_state(NR_ACTIVE_FILE) +
2344 global_page_state(NR_INACTIVE_FILE);
2346 if (nr_swap_pages > 0)
2347 nr += global_page_state(NR_ACTIVE_ANON) +
2348 global_page_state(NR_INACTIVE_ANON);
2350 return nr;
2353 unsigned long zone_reclaimable_pages(struct zone *zone)
2355 int nr;
2357 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2358 zone_page_state(zone, NR_INACTIVE_FILE);
2360 if (nr_swap_pages > 0)
2361 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2362 zone_page_state(zone, NR_INACTIVE_ANON);
2364 return nr;
2367 #ifdef CONFIG_HIBERNATION
2369 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2370 * freed pages.
2372 * Rather than trying to age LRUs the aim is to preserve the overall
2373 * LRU order by reclaiming preferentially
2374 * inactive > active > active referenced > active mapped
2376 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2378 struct reclaim_state reclaim_state;
2379 struct scan_control sc = {
2380 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2381 .may_swap = 1,
2382 .may_unmap = 1,
2383 .may_writepage = 1,
2384 .nr_to_reclaim = nr_to_reclaim,
2385 .hibernation_mode = 1,
2386 .swappiness = vm_swappiness,
2387 .order = 0,
2388 .isolate_pages = isolate_pages_global,
2390 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2391 struct task_struct *p = current;
2392 unsigned long nr_reclaimed;
2394 p->flags |= PF_MEMALLOC;
2395 lockdep_set_current_reclaim_state(sc.gfp_mask);
2396 reclaim_state.reclaimed_slab = 0;
2397 p->reclaim_state = &reclaim_state;
2399 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2401 p->reclaim_state = NULL;
2402 lockdep_clear_current_reclaim_state();
2403 p->flags &= ~PF_MEMALLOC;
2405 return nr_reclaimed;
2407 #endif /* CONFIG_HIBERNATION */
2409 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2410 not required for correctness. So if the last cpu in a node goes
2411 away, we get changed to run anywhere: as the first one comes back,
2412 restore their cpu bindings. */
2413 static int __devinit cpu_callback(struct notifier_block *nfb,
2414 unsigned long action, void *hcpu)
2416 int nid;
2418 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2419 for_each_node_state(nid, N_HIGH_MEMORY) {
2420 pg_data_t *pgdat = NODE_DATA(nid);
2421 const struct cpumask *mask;
2423 mask = cpumask_of_node(pgdat->node_id);
2425 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2426 /* One of our CPUs online: restore mask */
2427 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2430 return NOTIFY_OK;
2434 * This kswapd start function will be called by init and node-hot-add.
2435 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2437 int kswapd_run(int nid)
2439 pg_data_t *pgdat = NODE_DATA(nid);
2440 int ret = 0;
2442 if (pgdat->kswapd)
2443 return 0;
2445 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2446 if (IS_ERR(pgdat->kswapd)) {
2447 /* failure at boot is fatal */
2448 BUG_ON(system_state == SYSTEM_BOOTING);
2449 printk("Failed to start kswapd on node %d\n",nid);
2450 ret = -1;
2452 return ret;
2456 * Called by memory hotplug when all memory in a node is offlined.
2458 void kswapd_stop(int nid)
2460 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2462 if (kswapd)
2463 kthread_stop(kswapd);
2466 static int __init kswapd_init(void)
2468 int nid;
2470 swap_setup();
2471 for_each_node_state(nid, N_HIGH_MEMORY)
2472 kswapd_run(nid);
2473 hotcpu_notifier(cpu_callback, 0);
2474 return 0;
2477 module_init(kswapd_init)
2479 #ifdef CONFIG_NUMA
2481 * Zone reclaim mode
2483 * If non-zero call zone_reclaim when the number of free pages falls below
2484 * the watermarks.
2486 int zone_reclaim_mode __read_mostly;
2488 #define RECLAIM_OFF 0
2489 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2490 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2491 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2494 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2495 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2496 * a zone.
2498 #define ZONE_RECLAIM_PRIORITY 4
2501 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2502 * occur.
2504 int sysctl_min_unmapped_ratio = 1;
2507 * If the number of slab pages in a zone grows beyond this percentage then
2508 * slab reclaim needs to occur.
2510 int sysctl_min_slab_ratio = 5;
2512 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
2514 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
2515 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
2516 zone_page_state(zone, NR_ACTIVE_FILE);
2519 * It's possible for there to be more file mapped pages than
2520 * accounted for by the pages on the file LRU lists because
2521 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2523 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
2526 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2527 static long zone_pagecache_reclaimable(struct zone *zone)
2529 long nr_pagecache_reclaimable;
2530 long delta = 0;
2533 * If RECLAIM_SWAP is set, then all file pages are considered
2534 * potentially reclaimable. Otherwise, we have to worry about
2535 * pages like swapcache and zone_unmapped_file_pages() provides
2536 * a better estimate
2538 if (zone_reclaim_mode & RECLAIM_SWAP)
2539 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
2540 else
2541 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
2543 /* If we can't clean pages, remove dirty pages from consideration */
2544 if (!(zone_reclaim_mode & RECLAIM_WRITE))
2545 delta += zone_page_state(zone, NR_FILE_DIRTY);
2547 /* Watch for any possible underflows due to delta */
2548 if (unlikely(delta > nr_pagecache_reclaimable))
2549 delta = nr_pagecache_reclaimable;
2551 return nr_pagecache_reclaimable - delta;
2555 * Try to free up some pages from this zone through reclaim.
2557 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2559 /* Minimum pages needed in order to stay on node */
2560 const unsigned long nr_pages = 1 << order;
2561 struct task_struct *p = current;
2562 struct reclaim_state reclaim_state;
2563 int priority;
2564 struct scan_control sc = {
2565 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2566 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2567 .may_swap = 1,
2568 .nr_to_reclaim = max_t(unsigned long, nr_pages,
2569 SWAP_CLUSTER_MAX),
2570 .gfp_mask = gfp_mask,
2571 .swappiness = vm_swappiness,
2572 .order = order,
2573 .isolate_pages = isolate_pages_global,
2575 unsigned long slab_reclaimable;
2577 disable_swap_token();
2578 cond_resched();
2580 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2581 * and we also need to be able to write out pages for RECLAIM_WRITE
2582 * and RECLAIM_SWAP.
2584 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2585 lockdep_set_current_reclaim_state(gfp_mask);
2586 reclaim_state.reclaimed_slab = 0;
2587 p->reclaim_state = &reclaim_state;
2589 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2591 * Free memory by calling shrink zone with increasing
2592 * priorities until we have enough memory freed.
2594 priority = ZONE_RECLAIM_PRIORITY;
2595 do {
2596 note_zone_scanning_priority(zone, priority);
2597 shrink_zone(priority, zone, &sc);
2598 priority--;
2599 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2602 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2603 if (slab_reclaimable > zone->min_slab_pages) {
2605 * shrink_slab() does not currently allow us to determine how
2606 * many pages were freed in this zone. So we take the current
2607 * number of slab pages and shake the slab until it is reduced
2608 * by the same nr_pages that we used for reclaiming unmapped
2609 * pages.
2611 * Note that shrink_slab will free memory on all zones and may
2612 * take a long time.
2614 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2615 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2616 slab_reclaimable - nr_pages)
2620 * Update nr_reclaimed by the number of slab pages we
2621 * reclaimed from this zone.
2623 sc.nr_reclaimed += slab_reclaimable -
2624 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2627 p->reclaim_state = NULL;
2628 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2629 lockdep_clear_current_reclaim_state();
2630 return sc.nr_reclaimed >= nr_pages;
2633 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2635 int node_id;
2636 int ret;
2639 * Zone reclaim reclaims unmapped file backed pages and
2640 * slab pages if we are over the defined limits.
2642 * A small portion of unmapped file backed pages is needed for
2643 * file I/O otherwise pages read by file I/O will be immediately
2644 * thrown out if the zone is overallocated. So we do not reclaim
2645 * if less than a specified percentage of the zone is used by
2646 * unmapped file backed pages.
2648 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
2649 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
2650 return ZONE_RECLAIM_FULL;
2652 if (zone->all_unreclaimable)
2653 return ZONE_RECLAIM_FULL;
2656 * Do not scan if the allocation should not be delayed.
2658 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2659 return ZONE_RECLAIM_NOSCAN;
2662 * Only run zone reclaim on the local zone or on zones that do not
2663 * have associated processors. This will favor the local processor
2664 * over remote processors and spread off node memory allocations
2665 * as wide as possible.
2667 node_id = zone_to_nid(zone);
2668 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2669 return ZONE_RECLAIM_NOSCAN;
2671 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2672 return ZONE_RECLAIM_NOSCAN;
2674 ret = __zone_reclaim(zone, gfp_mask, order);
2675 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2677 if (!ret)
2678 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
2680 return ret;
2682 #endif
2685 * page_evictable - test whether a page is evictable
2686 * @page: the page to test
2687 * @vma: the VMA in which the page is or will be mapped, may be NULL
2689 * Test whether page is evictable--i.e., should be placed on active/inactive
2690 * lists vs unevictable list. The vma argument is !NULL when called from the
2691 * fault path to determine how to instantate a new page.
2693 * Reasons page might not be evictable:
2694 * (1) page's mapping marked unevictable
2695 * (2) page is part of an mlocked VMA
2698 int page_evictable(struct page *page, struct vm_area_struct *vma)
2701 if (mapping_unevictable(page_mapping(page)))
2702 return 0;
2704 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2705 return 0;
2707 return 1;
2711 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2712 * @page: page to check evictability and move to appropriate lru list
2713 * @zone: zone page is in
2715 * Checks a page for evictability and moves the page to the appropriate
2716 * zone lru list.
2718 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2719 * have PageUnevictable set.
2721 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2723 VM_BUG_ON(PageActive(page));
2725 retry:
2726 ClearPageUnevictable(page);
2727 if (page_evictable(page, NULL)) {
2728 enum lru_list l = page_lru_base_type(page);
2730 __dec_zone_state(zone, NR_UNEVICTABLE);
2731 list_move(&page->lru, &zone->lru[l].list);
2732 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2733 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2734 __count_vm_event(UNEVICTABLE_PGRESCUED);
2735 } else {
2737 * rotate unevictable list
2739 SetPageUnevictable(page);
2740 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2741 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2742 if (page_evictable(page, NULL))
2743 goto retry;
2748 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2749 * @mapping: struct address_space to scan for evictable pages
2751 * Scan all pages in mapping. Check unevictable pages for
2752 * evictability and move them to the appropriate zone lru list.
2754 void scan_mapping_unevictable_pages(struct address_space *mapping)
2756 pgoff_t next = 0;
2757 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2758 PAGE_CACHE_SHIFT;
2759 struct zone *zone;
2760 struct pagevec pvec;
2762 if (mapping->nrpages == 0)
2763 return;
2765 pagevec_init(&pvec, 0);
2766 while (next < end &&
2767 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2768 int i;
2769 int pg_scanned = 0;
2771 zone = NULL;
2773 for (i = 0; i < pagevec_count(&pvec); i++) {
2774 struct page *page = pvec.pages[i];
2775 pgoff_t page_index = page->index;
2776 struct zone *pagezone = page_zone(page);
2778 pg_scanned++;
2779 if (page_index > next)
2780 next = page_index;
2781 next++;
2783 if (pagezone != zone) {
2784 if (zone)
2785 spin_unlock_irq(&zone->lru_lock);
2786 zone = pagezone;
2787 spin_lock_irq(&zone->lru_lock);
2790 if (PageLRU(page) && PageUnevictable(page))
2791 check_move_unevictable_page(page, zone);
2793 if (zone)
2794 spin_unlock_irq(&zone->lru_lock);
2795 pagevec_release(&pvec);
2797 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2803 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2804 * @zone - zone of which to scan the unevictable list
2806 * Scan @zone's unevictable LRU lists to check for pages that have become
2807 * evictable. Move those that have to @zone's inactive list where they
2808 * become candidates for reclaim, unless shrink_inactive_zone() decides
2809 * to reactivate them. Pages that are still unevictable are rotated
2810 * back onto @zone's unevictable list.
2812 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2813 static void scan_zone_unevictable_pages(struct zone *zone)
2815 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2816 unsigned long scan;
2817 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2819 while (nr_to_scan > 0) {
2820 unsigned long batch_size = min(nr_to_scan,
2821 SCAN_UNEVICTABLE_BATCH_SIZE);
2823 spin_lock_irq(&zone->lru_lock);
2824 for (scan = 0; scan < batch_size; scan++) {
2825 struct page *page = lru_to_page(l_unevictable);
2827 if (!trylock_page(page))
2828 continue;
2830 prefetchw_prev_lru_page(page, l_unevictable, flags);
2832 if (likely(PageLRU(page) && PageUnevictable(page)))
2833 check_move_unevictable_page(page, zone);
2835 unlock_page(page);
2837 spin_unlock_irq(&zone->lru_lock);
2839 nr_to_scan -= batch_size;
2845 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2847 * A really big hammer: scan all zones' unevictable LRU lists to check for
2848 * pages that have become evictable. Move those back to the zones'
2849 * inactive list where they become candidates for reclaim.
2850 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2851 * and we add swap to the system. As such, it runs in the context of a task
2852 * that has possibly/probably made some previously unevictable pages
2853 * evictable.
2855 static void scan_all_zones_unevictable_pages(void)
2857 struct zone *zone;
2859 for_each_zone(zone) {
2860 scan_zone_unevictable_pages(zone);
2865 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2866 * all nodes' unevictable lists for evictable pages
2868 unsigned long scan_unevictable_pages;
2870 int scan_unevictable_handler(struct ctl_table *table, int write,
2871 void __user *buffer,
2872 size_t *length, loff_t *ppos)
2874 proc_doulongvec_minmax(table, write, buffer, length, ppos);
2876 if (write && *(unsigned long *)table->data)
2877 scan_all_zones_unevictable_pages();
2879 scan_unevictable_pages = 0;
2880 return 0;
2884 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2885 * a specified node's per zone unevictable lists for evictable pages.
2888 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2889 struct sysdev_attribute *attr,
2890 char *buf)
2892 return sprintf(buf, "0\n"); /* always zero; should fit... */
2895 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2896 struct sysdev_attribute *attr,
2897 const char *buf, size_t count)
2899 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2900 struct zone *zone;
2901 unsigned long res;
2902 unsigned long req = strict_strtoul(buf, 10, &res);
2904 if (!req)
2905 return 1; /* zero is no-op */
2907 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2908 if (!populated_zone(zone))
2909 continue;
2910 scan_zone_unevictable_pages(zone);
2912 return 1;
2916 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2917 read_scan_unevictable_node,
2918 write_scan_unevictable_node);
2920 int scan_unevictable_register_node(struct node *node)
2922 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2925 void scan_unevictable_unregister_node(struct node *node)
2927 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);