4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
15 #include <linux/module.h>
16 #include <linux/slab.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/swap.h>
19 #include <linux/pagemap.h>
20 #include <linux/init.h>
21 #include <linux/highmem.h>
22 #include <linux/vmstat.h>
23 #include <linux/file.h>
24 #include <linux/writeback.h>
25 #include <linux/blkdev.h>
26 #include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28 #include <linux/mm_inline.h>
29 #include <linux/pagevec.h>
30 #include <linux/backing-dev.h>
31 #include <linux/rmap.h>
32 #include <linux/topology.h>
33 #include <linux/cpu.h>
34 #include <linux/cpuset.h>
35 #include <linux/notifier.h>
36 #include <linux/rwsem.h>
37 #include <linux/delay.h>
38 #include <linux/kthread.h>
39 #include <linux/freezer.h>
40 #include <linux/memcontrol.h>
41 #include <linux/delayacct.h>
42 #include <linux/sysctl.h>
44 #include <asm/tlbflush.h>
45 #include <asm/div64.h>
47 #include <linux/swapops.h>
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 /* This context's GFP mask */
63 /* Can pages be swapped as part of reclaim? */
66 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
67 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
68 * In this context, it doesn't matter that we scan the
69 * whole list at once. */
74 int all_unreclaimable
;
78 /* Which cgroup do we reclaim from */
79 struct mem_cgroup
*mem_cgroup
;
81 /* Pluggable isolate pages callback */
82 unsigned long (*isolate_pages
)(unsigned long nr
, struct list_head
*dst
,
83 unsigned long *scanned
, int order
, int mode
,
84 struct zone
*z
, struct mem_cgroup
*mem_cont
,
85 int active
, int file
);
88 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
90 #ifdef ARCH_HAS_PREFETCH
91 #define prefetch_prev_lru_page(_page, _base, _field) \
93 if ((_page)->lru.prev != _base) { \
96 prev = lru_to_page(&(_page->lru)); \
97 prefetch(&prev->_field); \
101 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
104 #ifdef ARCH_HAS_PREFETCHW
105 #define prefetchw_prev_lru_page(_page, _base, _field) \
107 if ((_page)->lru.prev != _base) { \
110 prev = lru_to_page(&(_page->lru)); \
111 prefetchw(&prev->_field); \
115 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
119 * From 0 .. 100. Higher means more swappy.
121 int vm_swappiness
= 60;
122 long vm_total_pages
; /* The total number of pages which the VM controls */
124 static LIST_HEAD(shrinker_list
);
125 static DECLARE_RWSEM(shrinker_rwsem
);
127 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
128 #define scan_global_lru(sc) (!(sc)->mem_cgroup)
130 #define scan_global_lru(sc) (1)
133 static struct zone_reclaim_stat
*get_reclaim_stat(struct zone
*zone
,
134 struct scan_control
*sc
)
136 return &zone
->reclaim_stat
;
139 static unsigned long zone_nr_pages(struct zone
*zone
, struct scan_control
*sc
,
142 return zone_page_state(zone
, NR_LRU_BASE
+ lru
);
147 * Add a shrinker callback to be called from the vm
149 void register_shrinker(struct shrinker
*shrinker
)
152 down_write(&shrinker_rwsem
);
153 list_add_tail(&shrinker
->list
, &shrinker_list
);
154 up_write(&shrinker_rwsem
);
156 EXPORT_SYMBOL(register_shrinker
);
161 void unregister_shrinker(struct shrinker
*shrinker
)
163 down_write(&shrinker_rwsem
);
164 list_del(&shrinker
->list
);
165 up_write(&shrinker_rwsem
);
167 EXPORT_SYMBOL(unregister_shrinker
);
169 #define SHRINK_BATCH 128
171 * Call the shrink functions to age shrinkable caches
173 * Here we assume it costs one seek to replace a lru page and that it also
174 * takes a seek to recreate a cache object. With this in mind we age equal
175 * percentages of the lru and ageable caches. This should balance the seeks
176 * generated by these structures.
178 * If the vm encountered mapped pages on the LRU it increase the pressure on
179 * slab to avoid swapping.
181 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
183 * `lru_pages' represents the number of on-LRU pages in all the zones which
184 * are eligible for the caller's allocation attempt. It is used for balancing
185 * slab reclaim versus page reclaim.
187 * Returns the number of slab objects which we shrunk.
189 unsigned long shrink_slab(unsigned long scanned
, gfp_t gfp_mask
,
190 unsigned long lru_pages
)
192 struct shrinker
*shrinker
;
193 unsigned long ret
= 0;
196 scanned
= SWAP_CLUSTER_MAX
;
198 if (!down_read_trylock(&shrinker_rwsem
))
199 return 1; /* Assume we'll be able to shrink next time */
201 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
202 unsigned long long delta
;
203 unsigned long total_scan
;
204 unsigned long max_pass
= (*shrinker
->shrink
)(0, gfp_mask
);
206 delta
= (4 * scanned
) / shrinker
->seeks
;
208 do_div(delta
, lru_pages
+ 1);
209 shrinker
->nr
+= delta
;
210 if (shrinker
->nr
< 0) {
211 printk(KERN_ERR
"%s: nr=%ld\n",
212 __func__
, shrinker
->nr
);
213 shrinker
->nr
= max_pass
;
217 * Avoid risking looping forever due to too large nr value:
218 * never try to free more than twice the estimate number of
221 if (shrinker
->nr
> max_pass
* 2)
222 shrinker
->nr
= max_pass
* 2;
224 total_scan
= shrinker
->nr
;
227 while (total_scan
>= SHRINK_BATCH
) {
228 long this_scan
= SHRINK_BATCH
;
232 nr_before
= (*shrinker
->shrink
)(0, gfp_mask
);
233 shrink_ret
= (*shrinker
->shrink
)(this_scan
, gfp_mask
);
234 if (shrink_ret
== -1)
236 if (shrink_ret
< nr_before
)
237 ret
+= nr_before
- shrink_ret
;
238 count_vm_events(SLABS_SCANNED
, this_scan
);
239 total_scan
-= this_scan
;
244 shrinker
->nr
+= total_scan
;
246 up_read(&shrinker_rwsem
);
250 /* Called without lock on whether page is mapped, so answer is unstable */
251 static inline int page_mapping_inuse(struct page
*page
)
253 struct address_space
*mapping
;
255 /* Page is in somebody's page tables. */
256 if (page_mapped(page
))
259 /* Be more reluctant to reclaim swapcache than pagecache */
260 if (PageSwapCache(page
))
263 mapping
= page_mapping(page
);
267 /* File is mmap'd by somebody? */
268 return mapping_mapped(mapping
);
271 static inline int is_page_cache_freeable(struct page
*page
)
273 return page_count(page
) - !!PagePrivate(page
) == 2;
276 static int may_write_to_queue(struct backing_dev_info
*bdi
)
278 if (current
->flags
& PF_SWAPWRITE
)
280 if (!bdi_write_congested(bdi
))
282 if (bdi
== current
->backing_dev_info
)
288 * We detected a synchronous write error writing a page out. Probably
289 * -ENOSPC. We need to propagate that into the address_space for a subsequent
290 * fsync(), msync() or close().
292 * The tricky part is that after writepage we cannot touch the mapping: nothing
293 * prevents it from being freed up. But we have a ref on the page and once
294 * that page is locked, the mapping is pinned.
296 * We're allowed to run sleeping lock_page() here because we know the caller has
299 static void handle_write_error(struct address_space
*mapping
,
300 struct page
*page
, int error
)
303 if (page_mapping(page
) == mapping
)
304 mapping_set_error(mapping
, error
);
308 /* Request for sync pageout. */
314 /* possible outcome of pageout() */
316 /* failed to write page out, page is locked */
318 /* move page to the active list, page is locked */
320 /* page has been sent to the disk successfully, page is unlocked */
322 /* page is clean and locked */
327 * pageout is called by shrink_page_list() for each dirty page.
328 * Calls ->writepage().
330 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
331 enum pageout_io sync_writeback
)
334 * If the page is dirty, only perform writeback if that write
335 * will be non-blocking. To prevent this allocation from being
336 * stalled by pagecache activity. But note that there may be
337 * stalls if we need to run get_block(). We could test
338 * PagePrivate for that.
340 * If this process is currently in generic_file_write() against
341 * this page's queue, we can perform writeback even if that
344 * If the page is swapcache, write it back even if that would
345 * block, for some throttling. This happens by accident, because
346 * swap_backing_dev_info is bust: it doesn't reflect the
347 * congestion state of the swapdevs. Easy to fix, if needed.
348 * See swapfile.c:page_queue_congested().
350 if (!is_page_cache_freeable(page
))
354 * Some data journaling orphaned pages can have
355 * page->mapping == NULL while being dirty with clean buffers.
357 if (PagePrivate(page
)) {
358 if (try_to_free_buffers(page
)) {
359 ClearPageDirty(page
);
360 printk("%s: orphaned page\n", __func__
);
366 if (mapping
->a_ops
->writepage
== NULL
)
367 return PAGE_ACTIVATE
;
368 if (!may_write_to_queue(mapping
->backing_dev_info
))
371 if (clear_page_dirty_for_io(page
)) {
373 struct writeback_control wbc
= {
374 .sync_mode
= WB_SYNC_NONE
,
375 .nr_to_write
= SWAP_CLUSTER_MAX
,
377 .range_end
= LLONG_MAX
,
382 SetPageReclaim(page
);
383 res
= mapping
->a_ops
->writepage(page
, &wbc
);
385 handle_write_error(mapping
, page
, res
);
386 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
387 ClearPageReclaim(page
);
388 return PAGE_ACTIVATE
;
392 * Wait on writeback if requested to. This happens when
393 * direct reclaiming a large contiguous area and the
394 * first attempt to free a range of pages fails.
396 if (PageWriteback(page
) && sync_writeback
== PAGEOUT_IO_SYNC
)
397 wait_on_page_writeback(page
);
399 if (!PageWriteback(page
)) {
400 /* synchronous write or broken a_ops? */
401 ClearPageReclaim(page
);
403 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
411 * Same as remove_mapping, but if the page is removed from the mapping, it
412 * gets returned with a refcount of 0.
414 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
)
416 BUG_ON(!PageLocked(page
));
417 BUG_ON(mapping
!= page_mapping(page
));
419 spin_lock_irq(&mapping
->tree_lock
);
421 * The non racy check for a busy page.
423 * Must be careful with the order of the tests. When someone has
424 * a ref to the page, it may be possible that they dirty it then
425 * drop the reference. So if PageDirty is tested before page_count
426 * here, then the following race may occur:
428 * get_user_pages(&page);
429 * [user mapping goes away]
431 * !PageDirty(page) [good]
432 * SetPageDirty(page);
434 * !page_count(page) [good, discard it]
436 * [oops, our write_to data is lost]
438 * Reversing the order of the tests ensures such a situation cannot
439 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
440 * load is not satisfied before that of page->_count.
442 * Note that if SetPageDirty is always performed via set_page_dirty,
443 * and thus under tree_lock, then this ordering is not required.
445 if (!page_freeze_refs(page
, 2))
447 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
448 if (unlikely(PageDirty(page
))) {
449 page_unfreeze_refs(page
, 2);
453 if (PageSwapCache(page
)) {
454 swp_entry_t swap
= { .val
= page_private(page
) };
455 __delete_from_swap_cache(page
);
456 spin_unlock_irq(&mapping
->tree_lock
);
459 __remove_from_page_cache(page
);
460 spin_unlock_irq(&mapping
->tree_lock
);
466 spin_unlock_irq(&mapping
->tree_lock
);
471 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
472 * someone else has a ref on the page, abort and return 0. If it was
473 * successfully detached, return 1. Assumes the caller has a single ref on
476 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
478 if (__remove_mapping(mapping
, page
)) {
480 * Unfreezing the refcount with 1 rather than 2 effectively
481 * drops the pagecache ref for us without requiring another
484 page_unfreeze_refs(page
, 1);
491 * putback_lru_page - put previously isolated page onto appropriate LRU list
492 * @page: page to be put back to appropriate lru list
494 * Add previously isolated @page to appropriate LRU list.
495 * Page may still be unevictable for other reasons.
497 * lru_lock must not be held, interrupts must be enabled.
499 #ifdef CONFIG_UNEVICTABLE_LRU
500 void putback_lru_page(struct page
*page
)
503 int active
= !!TestClearPageActive(page
);
504 int was_unevictable
= PageUnevictable(page
);
506 VM_BUG_ON(PageLRU(page
));
509 ClearPageUnevictable(page
);
511 if (page_evictable(page
, NULL
)) {
513 * For evictable pages, we can use the cache.
514 * In event of a race, worst case is we end up with an
515 * unevictable page on [in]active list.
516 * We know how to handle that.
518 lru
= active
+ page_is_file_cache(page
);
519 lru_cache_add_lru(page
, lru
);
522 * Put unevictable pages directly on zone's unevictable
525 lru
= LRU_UNEVICTABLE
;
526 add_page_to_unevictable_list(page
);
530 * page's status can change while we move it among lru. If an evictable
531 * page is on unevictable list, it never be freed. To avoid that,
532 * check after we added it to the list, again.
534 if (lru
== LRU_UNEVICTABLE
&& page_evictable(page
, NULL
)) {
535 if (!isolate_lru_page(page
)) {
539 /* This means someone else dropped this page from LRU
540 * So, it will be freed or putback to LRU again. There is
541 * nothing to do here.
545 if (was_unevictable
&& lru
!= LRU_UNEVICTABLE
)
546 count_vm_event(UNEVICTABLE_PGRESCUED
);
547 else if (!was_unevictable
&& lru
== LRU_UNEVICTABLE
)
548 count_vm_event(UNEVICTABLE_PGCULLED
);
550 put_page(page
); /* drop ref from isolate */
553 #else /* CONFIG_UNEVICTABLE_LRU */
555 void putback_lru_page(struct page
*page
)
558 VM_BUG_ON(PageLRU(page
));
560 lru
= !!TestClearPageActive(page
) + page_is_file_cache(page
);
561 lru_cache_add_lru(page
, lru
);
564 #endif /* CONFIG_UNEVICTABLE_LRU */
568 * shrink_page_list() returns the number of reclaimed pages
570 static unsigned long shrink_page_list(struct list_head
*page_list
,
571 struct scan_control
*sc
,
572 enum pageout_io sync_writeback
)
574 LIST_HEAD(ret_pages
);
575 struct pagevec freed_pvec
;
577 unsigned long nr_reclaimed
= 0;
581 pagevec_init(&freed_pvec
, 1);
582 while (!list_empty(page_list
)) {
583 struct address_space
*mapping
;
590 page
= lru_to_page(page_list
);
591 list_del(&page
->lru
);
593 if (!trylock_page(page
))
596 VM_BUG_ON(PageActive(page
));
600 if (unlikely(!page_evictable(page
, NULL
)))
603 if (!sc
->may_swap
&& page_mapped(page
))
606 /* Double the slab pressure for mapped and swapcache pages */
607 if (page_mapped(page
) || PageSwapCache(page
))
610 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
611 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
613 if (PageWriteback(page
)) {
615 * Synchronous reclaim is performed in two passes,
616 * first an asynchronous pass over the list to
617 * start parallel writeback, and a second synchronous
618 * pass to wait for the IO to complete. Wait here
619 * for any page for which writeback has already
622 if (sync_writeback
== PAGEOUT_IO_SYNC
&& may_enter_fs
)
623 wait_on_page_writeback(page
);
628 referenced
= page_referenced(page
, 1, sc
->mem_cgroup
);
629 /* In active use or really unfreeable? Activate it. */
630 if (sc
->order
<= PAGE_ALLOC_COSTLY_ORDER
&&
631 referenced
&& page_mapping_inuse(page
))
632 goto activate_locked
;
635 * Anonymous process memory has backing store?
636 * Try to allocate it some swap space here.
638 if (PageAnon(page
) && !PageSwapCache(page
)) {
639 if (!(sc
->gfp_mask
& __GFP_IO
))
641 if (!add_to_swap(page
))
642 goto activate_locked
;
646 mapping
= page_mapping(page
);
649 * The page is mapped into the page tables of one or more
650 * processes. Try to unmap it here.
652 if (page_mapped(page
) && mapping
) {
653 switch (try_to_unmap(page
, 0)) {
655 goto activate_locked
;
661 ; /* try to free the page below */
665 if (PageDirty(page
)) {
666 if (sc
->order
<= PAGE_ALLOC_COSTLY_ORDER
&& referenced
)
670 if (!sc
->may_writepage
)
673 /* Page is dirty, try to write it out here */
674 switch (pageout(page
, mapping
, sync_writeback
)) {
678 goto activate_locked
;
680 if (PageWriteback(page
) || PageDirty(page
))
683 * A synchronous write - probably a ramdisk. Go
684 * ahead and try to reclaim the page.
686 if (!trylock_page(page
))
688 if (PageDirty(page
) || PageWriteback(page
))
690 mapping
= page_mapping(page
);
692 ; /* try to free the page below */
697 * If the page has buffers, try to free the buffer mappings
698 * associated with this page. If we succeed we try to free
701 * We do this even if the page is PageDirty().
702 * try_to_release_page() does not perform I/O, but it is
703 * possible for a page to have PageDirty set, but it is actually
704 * clean (all its buffers are clean). This happens if the
705 * buffers were written out directly, with submit_bh(). ext3
706 * will do this, as well as the blockdev mapping.
707 * try_to_release_page() will discover that cleanness and will
708 * drop the buffers and mark the page clean - it can be freed.
710 * Rarely, pages can have buffers and no ->mapping. These are
711 * the pages which were not successfully invalidated in
712 * truncate_complete_page(). We try to drop those buffers here
713 * and if that worked, and the page is no longer mapped into
714 * process address space (page_count == 1) it can be freed.
715 * Otherwise, leave the page on the LRU so it is swappable.
717 if (PagePrivate(page
)) {
718 if (!try_to_release_page(page
, sc
->gfp_mask
))
719 goto activate_locked
;
720 if (!mapping
&& page_count(page
) == 1) {
722 if (put_page_testzero(page
))
726 * rare race with speculative reference.
727 * the speculative reference will free
728 * this page shortly, so we may
729 * increment nr_reclaimed here (and
730 * leave it off the LRU).
738 if (!mapping
|| !__remove_mapping(mapping
, page
))
742 * At this point, we have no other references and there is
743 * no way to pick any more up (removed from LRU, removed
744 * from pagecache). Can use non-atomic bitops now (and
745 * we obviously don't have to worry about waking up a process
746 * waiting on the page lock, because there are no references.
748 __clear_page_locked(page
);
751 if (!pagevec_add(&freed_pvec
, page
)) {
752 __pagevec_free(&freed_pvec
);
753 pagevec_reinit(&freed_pvec
);
758 if (PageSwapCache(page
))
759 try_to_free_swap(page
);
761 putback_lru_page(page
);
765 /* Not a candidate for swapping, so reclaim swap space. */
766 if (PageSwapCache(page
) && vm_swap_full())
767 try_to_free_swap(page
);
768 VM_BUG_ON(PageActive(page
));
774 list_add(&page
->lru
, &ret_pages
);
775 VM_BUG_ON(PageLRU(page
) || PageUnevictable(page
));
777 list_splice(&ret_pages
, page_list
);
778 if (pagevec_count(&freed_pvec
))
779 __pagevec_free(&freed_pvec
);
780 count_vm_events(PGACTIVATE
, pgactivate
);
784 /* LRU Isolation modes. */
785 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
786 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
787 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
790 * Attempt to remove the specified page from its LRU. Only take this page
791 * if it is of the appropriate PageActive status. Pages which are being
792 * freed elsewhere are also ignored.
794 * page: page to consider
795 * mode: one of the LRU isolation modes defined above
797 * returns 0 on success, -ve errno on failure.
799 int __isolate_lru_page(struct page
*page
, int mode
, int file
)
803 /* Only take pages on the LRU. */
808 * When checking the active state, we need to be sure we are
809 * dealing with comparible boolean values. Take the logical not
812 if (mode
!= ISOLATE_BOTH
&& (!PageActive(page
) != !mode
))
815 if (mode
!= ISOLATE_BOTH
&& (!page_is_file_cache(page
) != !file
))
819 * When this function is being called for lumpy reclaim, we
820 * initially look into all LRU pages, active, inactive and
821 * unevictable; only give shrink_page_list evictable pages.
823 if (PageUnevictable(page
))
828 if (likely(get_page_unless_zero(page
))) {
830 * Be careful not to clear PageLRU until after we're
831 * sure the page is not being freed elsewhere -- the
832 * page release code relies on it.
836 mem_cgroup_del_lru(page
);
843 * zone->lru_lock is heavily contended. Some of the functions that
844 * shrink the lists perform better by taking out a batch of pages
845 * and working on them outside the LRU lock.
847 * For pagecache intensive workloads, this function is the hottest
848 * spot in the kernel (apart from copy_*_user functions).
850 * Appropriate locks must be held before calling this function.
852 * @nr_to_scan: The number of pages to look through on the list.
853 * @src: The LRU list to pull pages off.
854 * @dst: The temp list to put pages on to.
855 * @scanned: The number of pages that were scanned.
856 * @order: The caller's attempted allocation order
857 * @mode: One of the LRU isolation modes
858 * @file: True [1] if isolating file [!anon] pages
860 * returns how many pages were moved onto *@dst.
862 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
863 struct list_head
*src
, struct list_head
*dst
,
864 unsigned long *scanned
, int order
, int mode
, int file
)
866 unsigned long nr_taken
= 0;
869 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
872 unsigned long end_pfn
;
873 unsigned long page_pfn
;
876 page
= lru_to_page(src
);
877 prefetchw_prev_lru_page(page
, src
, flags
);
879 VM_BUG_ON(!PageLRU(page
));
881 switch (__isolate_lru_page(page
, mode
, file
)) {
883 list_move(&page
->lru
, dst
);
888 /* else it is being freed elsewhere */
889 list_move(&page
->lru
, src
);
900 * Attempt to take all pages in the order aligned region
901 * surrounding the tag page. Only take those pages of
902 * the same active state as that tag page. We may safely
903 * round the target page pfn down to the requested order
904 * as the mem_map is guarenteed valid out to MAX_ORDER,
905 * where that page is in a different zone we will detect
906 * it from its zone id and abort this block scan.
908 zone_id
= page_zone_id(page
);
909 page_pfn
= page_to_pfn(page
);
910 pfn
= page_pfn
& ~((1 << order
) - 1);
911 end_pfn
= pfn
+ (1 << order
);
912 for (; pfn
< end_pfn
; pfn
++) {
913 struct page
*cursor_page
;
915 /* The target page is in the block, ignore it. */
916 if (unlikely(pfn
== page_pfn
))
919 /* Avoid holes within the zone. */
920 if (unlikely(!pfn_valid_within(pfn
)))
923 cursor_page
= pfn_to_page(pfn
);
925 /* Check that we have not crossed a zone boundary. */
926 if (unlikely(page_zone_id(cursor_page
) != zone_id
))
928 switch (__isolate_lru_page(cursor_page
, mode
, file
)) {
930 list_move(&cursor_page
->lru
, dst
);
936 /* else it is being freed elsewhere */
937 list_move(&cursor_page
->lru
, src
);
939 break; /* ! on LRU or wrong list */
948 static unsigned long isolate_pages_global(unsigned long nr
,
949 struct list_head
*dst
,
950 unsigned long *scanned
, int order
,
951 int mode
, struct zone
*z
,
952 struct mem_cgroup
*mem_cont
,
953 int active
, int file
)
960 return isolate_lru_pages(nr
, &z
->lru
[lru
].list
, dst
, scanned
, order
,
965 * clear_active_flags() is a helper for shrink_active_list(), clearing
966 * any active bits from the pages in the list.
968 static unsigned long clear_active_flags(struct list_head
*page_list
,
975 list_for_each_entry(page
, page_list
, lru
) {
976 lru
= page_is_file_cache(page
);
977 if (PageActive(page
)) {
979 ClearPageActive(page
);
989 * isolate_lru_page - tries to isolate a page from its LRU list
990 * @page: page to isolate from its LRU list
992 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
993 * vmstat statistic corresponding to whatever LRU list the page was on.
995 * Returns 0 if the page was removed from an LRU list.
996 * Returns -EBUSY if the page was not on an LRU list.
998 * The returned page will have PageLRU() cleared. If it was found on
999 * the active list, it will have PageActive set. If it was found on
1000 * the unevictable list, it will have the PageUnevictable bit set. That flag
1001 * may need to be cleared by the caller before letting the page go.
1003 * The vmstat statistic corresponding to the list on which the page was
1004 * found will be decremented.
1007 * (1) Must be called with an elevated refcount on the page. This is a
1008 * fundamentnal difference from isolate_lru_pages (which is called
1009 * without a stable reference).
1010 * (2) the lru_lock must not be held.
1011 * (3) interrupts must be enabled.
1013 int isolate_lru_page(struct page
*page
)
1017 if (PageLRU(page
)) {
1018 struct zone
*zone
= page_zone(page
);
1020 spin_lock_irq(&zone
->lru_lock
);
1021 if (PageLRU(page
) && get_page_unless_zero(page
)) {
1022 int lru
= page_lru(page
);
1026 del_page_from_lru_list(zone
, page
, lru
);
1028 spin_unlock_irq(&zone
->lru_lock
);
1034 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1035 * of reclaimed pages
1037 static unsigned long shrink_inactive_list(unsigned long max_scan
,
1038 struct zone
*zone
, struct scan_control
*sc
,
1039 int priority
, int file
)
1041 LIST_HEAD(page_list
);
1042 struct pagevec pvec
;
1043 unsigned long nr_scanned
= 0;
1044 unsigned long nr_reclaimed
= 0;
1045 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1047 pagevec_init(&pvec
, 1);
1050 spin_lock_irq(&zone
->lru_lock
);
1053 unsigned long nr_taken
;
1054 unsigned long nr_scan
;
1055 unsigned long nr_freed
;
1056 unsigned long nr_active
;
1057 unsigned int count
[NR_LRU_LISTS
] = { 0, };
1058 int mode
= ISOLATE_INACTIVE
;
1061 * If we need a large contiguous chunk of memory, or have
1062 * trouble getting a small set of contiguous pages, we
1063 * will reclaim both active and inactive pages.
1065 * We use the same threshold as pageout congestion_wait below.
1067 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
1068 mode
= ISOLATE_BOTH
;
1069 else if (sc
->order
&& priority
< DEF_PRIORITY
- 2)
1070 mode
= ISOLATE_BOTH
;
1072 nr_taken
= sc
->isolate_pages(sc
->swap_cluster_max
,
1073 &page_list
, &nr_scan
, sc
->order
, mode
,
1074 zone
, sc
->mem_cgroup
, 0, file
);
1075 nr_active
= clear_active_flags(&page_list
, count
);
1076 __count_vm_events(PGDEACTIVATE
, nr_active
);
1078 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
1079 -count
[LRU_ACTIVE_FILE
]);
1080 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
1081 -count
[LRU_INACTIVE_FILE
]);
1082 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
1083 -count
[LRU_ACTIVE_ANON
]);
1084 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
1085 -count
[LRU_INACTIVE_ANON
]);
1087 if (scan_global_lru(sc
)) {
1088 zone
->pages_scanned
+= nr_scan
;
1089 reclaim_stat
->recent_scanned
[0] +=
1090 count
[LRU_INACTIVE_ANON
];
1091 reclaim_stat
->recent_scanned
[0] +=
1092 count
[LRU_ACTIVE_ANON
];
1093 reclaim_stat
->recent_scanned
[1] +=
1094 count
[LRU_INACTIVE_FILE
];
1095 reclaim_stat
->recent_scanned
[1] +=
1096 count
[LRU_ACTIVE_FILE
];
1098 spin_unlock_irq(&zone
->lru_lock
);
1100 nr_scanned
+= nr_scan
;
1101 nr_freed
= shrink_page_list(&page_list
, sc
, PAGEOUT_IO_ASYNC
);
1104 * If we are direct reclaiming for contiguous pages and we do
1105 * not reclaim everything in the list, try again and wait
1106 * for IO to complete. This will stall high-order allocations
1107 * but that should be acceptable to the caller
1109 if (nr_freed
< nr_taken
&& !current_is_kswapd() &&
1110 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
) {
1111 congestion_wait(WRITE
, HZ
/10);
1114 * The attempt at page out may have made some
1115 * of the pages active, mark them inactive again.
1117 nr_active
= clear_active_flags(&page_list
, count
);
1118 count_vm_events(PGDEACTIVATE
, nr_active
);
1120 nr_freed
+= shrink_page_list(&page_list
, sc
,
1124 nr_reclaimed
+= nr_freed
;
1125 local_irq_disable();
1126 if (current_is_kswapd()) {
1127 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
, nr_scan
);
1128 __count_vm_events(KSWAPD_STEAL
, nr_freed
);
1129 } else if (scan_global_lru(sc
))
1130 __count_zone_vm_events(PGSCAN_DIRECT
, zone
, nr_scan
);
1132 __count_zone_vm_events(PGSTEAL
, zone
, nr_freed
);
1137 spin_lock(&zone
->lru_lock
);
1139 * Put back any unfreeable pages.
1141 while (!list_empty(&page_list
)) {
1143 page
= lru_to_page(&page_list
);
1144 VM_BUG_ON(PageLRU(page
));
1145 list_del(&page
->lru
);
1146 if (unlikely(!page_evictable(page
, NULL
))) {
1147 spin_unlock_irq(&zone
->lru_lock
);
1148 putback_lru_page(page
);
1149 spin_lock_irq(&zone
->lru_lock
);
1153 lru
= page_lru(page
);
1154 add_page_to_lru_list(zone
, page
, lru
);
1155 if (PageActive(page
) && scan_global_lru(sc
)) {
1156 int file
= !!page_is_file_cache(page
);
1157 reclaim_stat
->recent_rotated
[file
]++;
1159 if (!pagevec_add(&pvec
, page
)) {
1160 spin_unlock_irq(&zone
->lru_lock
);
1161 __pagevec_release(&pvec
);
1162 spin_lock_irq(&zone
->lru_lock
);
1165 } while (nr_scanned
< max_scan
);
1166 spin_unlock(&zone
->lru_lock
);
1169 pagevec_release(&pvec
);
1170 return nr_reclaimed
;
1174 * We are about to scan this zone at a certain priority level. If that priority
1175 * level is smaller (ie: more urgent) than the previous priority, then note
1176 * that priority level within the zone. This is done so that when the next
1177 * process comes in to scan this zone, it will immediately start out at this
1178 * priority level rather than having to build up its own scanning priority.
1179 * Here, this priority affects only the reclaim-mapped threshold.
1181 static inline void note_zone_scanning_priority(struct zone
*zone
, int priority
)
1183 if (priority
< zone
->prev_priority
)
1184 zone
->prev_priority
= priority
;
1188 * This moves pages from the active list to the inactive list.
1190 * We move them the other way if the page is referenced by one or more
1191 * processes, from rmap.
1193 * If the pages are mostly unmapped, the processing is fast and it is
1194 * appropriate to hold zone->lru_lock across the whole operation. But if
1195 * the pages are mapped, the processing is slow (page_referenced()) so we
1196 * should drop zone->lru_lock around each page. It's impossible to balance
1197 * this, so instead we remove the pages from the LRU while processing them.
1198 * It is safe to rely on PG_active against the non-LRU pages in here because
1199 * nobody will play with that bit on a non-LRU page.
1201 * The downside is that we have to touch page->_count against each page.
1202 * But we had to alter page->flags anyway.
1206 static void shrink_active_list(unsigned long nr_pages
, struct zone
*zone
,
1207 struct scan_control
*sc
, int priority
, int file
)
1209 unsigned long pgmoved
;
1210 int pgdeactivate
= 0;
1211 unsigned long pgscanned
;
1212 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1213 LIST_HEAD(l_inactive
);
1215 struct pagevec pvec
;
1217 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1220 spin_lock_irq(&zone
->lru_lock
);
1221 pgmoved
= sc
->isolate_pages(nr_pages
, &l_hold
, &pgscanned
, sc
->order
,
1222 ISOLATE_ACTIVE
, zone
,
1223 sc
->mem_cgroup
, 1, file
);
1225 * zone->pages_scanned is used for detect zone's oom
1226 * mem_cgroup remembers nr_scan by itself.
1228 if (scan_global_lru(sc
)) {
1229 zone
->pages_scanned
+= pgscanned
;
1230 reclaim_stat
->recent_scanned
[!!file
] += pgmoved
;
1234 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -pgmoved
);
1236 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -pgmoved
);
1237 spin_unlock_irq(&zone
->lru_lock
);
1240 while (!list_empty(&l_hold
)) {
1242 page
= lru_to_page(&l_hold
);
1243 list_del(&page
->lru
);
1245 if (unlikely(!page_evictable(page
, NULL
))) {
1246 putback_lru_page(page
);
1250 /* page_referenced clears PageReferenced */
1251 if (page_mapping_inuse(page
) &&
1252 page_referenced(page
, 0, sc
->mem_cgroup
))
1255 list_add(&page
->lru
, &l_inactive
);
1259 * Move the pages to the [file or anon] inactive list.
1261 pagevec_init(&pvec
, 1);
1263 lru
= LRU_BASE
+ file
* LRU_FILE
;
1265 spin_lock_irq(&zone
->lru_lock
);
1267 * Count referenced pages from currently used mappings as
1268 * rotated, even though they are moved to the inactive list.
1269 * This helps balance scan pressure between file and anonymous
1270 * pages in get_scan_ratio.
1272 if (scan_global_lru(sc
))
1273 reclaim_stat
->recent_rotated
[!!file
] += pgmoved
;
1275 while (!list_empty(&l_inactive
)) {
1276 page
= lru_to_page(&l_inactive
);
1277 prefetchw_prev_lru_page(page
, &l_inactive
, flags
);
1278 VM_BUG_ON(PageLRU(page
));
1280 VM_BUG_ON(!PageActive(page
));
1281 ClearPageActive(page
);
1283 list_move(&page
->lru
, &zone
->lru
[lru
].list
);
1284 mem_cgroup_add_lru_list(page
, lru
);
1286 if (!pagevec_add(&pvec
, page
)) {
1287 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1288 spin_unlock_irq(&zone
->lru_lock
);
1289 pgdeactivate
+= pgmoved
;
1291 if (buffer_heads_over_limit
)
1292 pagevec_strip(&pvec
);
1293 __pagevec_release(&pvec
);
1294 spin_lock_irq(&zone
->lru_lock
);
1297 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1298 pgdeactivate
+= pgmoved
;
1299 if (buffer_heads_over_limit
) {
1300 spin_unlock_irq(&zone
->lru_lock
);
1301 pagevec_strip(&pvec
);
1302 spin_lock_irq(&zone
->lru_lock
);
1304 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1305 __count_vm_events(PGDEACTIVATE
, pgdeactivate
);
1306 spin_unlock_irq(&zone
->lru_lock
);
1308 pagevec_swap_free(&pvec
);
1310 pagevec_release(&pvec
);
1314 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1315 * @zone: zone to check
1317 * Returns true if the zone does not have enough inactive anon pages,
1318 * meaning some active anon pages need to be deactivated.
1320 static int inactive_anon_is_low(struct zone
*zone
)
1322 unsigned long active
, inactive
;
1324 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1325 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1327 if (inactive
* zone
->inactive_ratio
< active
)
1333 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1334 struct zone
*zone
, struct scan_control
*sc
, int priority
)
1336 int file
= is_file_lru(lru
);
1338 if (lru
== LRU_ACTIVE_FILE
) {
1339 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1343 if (lru
== LRU_ACTIVE_ANON
&&
1344 (!scan_global_lru(sc
) || inactive_anon_is_low(zone
))) {
1345 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1348 return shrink_inactive_list(nr_to_scan
, zone
, sc
, priority
, file
);
1352 * Determine how aggressively the anon and file LRU lists should be
1353 * scanned. The relative value of each set of LRU lists is determined
1354 * by looking at the fraction of the pages scanned we did rotate back
1355 * onto the active list instead of evict.
1357 * percent[0] specifies how much pressure to put on ram/swap backed
1358 * memory, while percent[1] determines pressure on the file LRUs.
1360 static void get_scan_ratio(struct zone
*zone
, struct scan_control
*sc
,
1361 unsigned long *percent
)
1363 unsigned long anon
, file
, free
;
1364 unsigned long anon_prio
, file_prio
;
1365 unsigned long ap
, fp
;
1366 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1368 /* If we have no swap space, do not bother scanning anon pages. */
1369 if (nr_swap_pages
<= 0) {
1375 anon
= zone_nr_pages(zone
, sc
, LRU_ACTIVE_ANON
) +
1376 zone_nr_pages(zone
, sc
, LRU_INACTIVE_ANON
);
1377 file
= zone_nr_pages(zone
, sc
, LRU_ACTIVE_FILE
) +
1378 zone_nr_pages(zone
, sc
, LRU_INACTIVE_FILE
);
1380 if (scan_global_lru(sc
)) {
1381 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1382 /* If we have very few page cache pages,
1383 force-scan anon pages. */
1384 if (unlikely(file
+ free
<= zone
->pages_high
)) {
1392 * OK, so we have swap space and a fair amount of page cache
1393 * pages. We use the recently rotated / recently scanned
1394 * ratios to determine how valuable each cache is.
1396 * Because workloads change over time (and to avoid overflow)
1397 * we keep these statistics as a floating average, which ends
1398 * up weighing recent references more than old ones.
1400 * anon in [0], file in [1]
1402 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1403 spin_lock_irq(&zone
->lru_lock
);
1404 reclaim_stat
->recent_scanned
[0] /= 2;
1405 reclaim_stat
->recent_rotated
[0] /= 2;
1406 spin_unlock_irq(&zone
->lru_lock
);
1409 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1410 spin_lock_irq(&zone
->lru_lock
);
1411 reclaim_stat
->recent_scanned
[1] /= 2;
1412 reclaim_stat
->recent_rotated
[1] /= 2;
1413 spin_unlock_irq(&zone
->lru_lock
);
1417 * With swappiness at 100, anonymous and file have the same priority.
1418 * This scanning priority is essentially the inverse of IO cost.
1420 anon_prio
= sc
->swappiness
;
1421 file_prio
= 200 - sc
->swappiness
;
1424 * The amount of pressure on anon vs file pages is inversely
1425 * proportional to the fraction of recently scanned pages on
1426 * each list that were recently referenced and in active use.
1428 ap
= (anon_prio
+ 1) * (reclaim_stat
->recent_scanned
[0] + 1);
1429 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1431 fp
= (file_prio
+ 1) * (reclaim_stat
->recent_scanned
[1] + 1);
1432 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1434 /* Normalize to percentages */
1435 percent
[0] = 100 * ap
/ (ap
+ fp
+ 1);
1436 percent
[1] = 100 - percent
[0];
1441 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1443 static void shrink_zone(int priority
, struct zone
*zone
,
1444 struct scan_control
*sc
)
1446 unsigned long nr
[NR_LRU_LISTS
];
1447 unsigned long nr_to_scan
;
1448 unsigned long percent
[2]; /* anon @ 0; file @ 1 */
1450 unsigned long nr_reclaimed
= sc
->nr_reclaimed
;
1451 unsigned long swap_cluster_max
= sc
->swap_cluster_max
;
1453 get_scan_ratio(zone
, sc
, percent
);
1455 for_each_evictable_lru(l
) {
1456 if (scan_global_lru(sc
)) {
1457 int file
= is_file_lru(l
);
1460 scan
= zone_page_state(zone
, NR_LRU_BASE
+ l
);
1463 scan
= (scan
* percent
[file
]) / 100;
1465 zone
->lru
[l
].nr_scan
+= scan
;
1466 nr
[l
] = zone
->lru
[l
].nr_scan
;
1467 if (nr
[l
] >= swap_cluster_max
)
1468 zone
->lru
[l
].nr_scan
= 0;
1473 * This reclaim occurs not because zone memory shortage
1474 * but because memory controller hits its limit.
1475 * Don't modify zone reclaim related data.
1477 nr
[l
] = mem_cgroup_calc_reclaim(sc
->mem_cgroup
, zone
,
1482 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
1483 nr
[LRU_INACTIVE_FILE
]) {
1484 for_each_evictable_lru(l
) {
1486 nr_to_scan
= min(nr
[l
], swap_cluster_max
);
1487 nr
[l
] -= nr_to_scan
;
1489 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
1490 zone
, sc
, priority
);
1494 * On large memory systems, scan >> priority can become
1495 * really large. This is fine for the starting priority;
1496 * we want to put equal scanning pressure on each zone.
1497 * However, if the VM has a harder time of freeing pages,
1498 * with multiple processes reclaiming pages, the total
1499 * freeing target can get unreasonably large.
1501 if (nr_reclaimed
> swap_cluster_max
&&
1502 priority
< DEF_PRIORITY
&& !current_is_kswapd())
1506 sc
->nr_reclaimed
= nr_reclaimed
;
1509 * Even if we did not try to evict anon pages at all, we want to
1510 * rebalance the anon lru active/inactive ratio.
1512 if (!scan_global_lru(sc
) || inactive_anon_is_low(zone
))
1513 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
1514 else if (!scan_global_lru(sc
))
1515 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
1517 throttle_vm_writeout(sc
->gfp_mask
);
1521 * This is the direct reclaim path, for page-allocating processes. We only
1522 * try to reclaim pages from zones which will satisfy the caller's allocation
1525 * We reclaim from a zone even if that zone is over pages_high. Because:
1526 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1528 * b) The zones may be over pages_high but they must go *over* pages_high to
1529 * satisfy the `incremental min' zone defense algorithm.
1531 * If a zone is deemed to be full of pinned pages then just give it a light
1532 * scan then give up on it.
1534 static void shrink_zones(int priority
, struct zonelist
*zonelist
,
1535 struct scan_control
*sc
)
1537 enum zone_type high_zoneidx
= gfp_zone(sc
->gfp_mask
);
1541 sc
->all_unreclaimable
= 1;
1542 for_each_zone_zonelist(zone
, z
, zonelist
, high_zoneidx
) {
1543 if (!populated_zone(zone
))
1546 * Take care memory controller reclaiming has small influence
1549 if (scan_global_lru(sc
)) {
1550 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1552 note_zone_scanning_priority(zone
, priority
);
1554 if (zone_is_all_unreclaimable(zone
) &&
1555 priority
!= DEF_PRIORITY
)
1556 continue; /* Let kswapd poll it */
1557 sc
->all_unreclaimable
= 0;
1560 * Ignore cpuset limitation here. We just want to reduce
1561 * # of used pages by us regardless of memory shortage.
1563 sc
->all_unreclaimable
= 0;
1564 mem_cgroup_note_reclaim_priority(sc
->mem_cgroup
,
1568 shrink_zone(priority
, zone
, sc
);
1573 * This is the main entry point to direct page reclaim.
1575 * If a full scan of the inactive list fails to free enough memory then we
1576 * are "out of memory" and something needs to be killed.
1578 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1579 * high - the zone may be full of dirty or under-writeback pages, which this
1580 * caller can't do much about. We kick pdflush and take explicit naps in the
1581 * hope that some of these pages can be written. But if the allocating task
1582 * holds filesystem locks which prevent writeout this might not work, and the
1583 * allocation attempt will fail.
1585 * returns: 0, if no pages reclaimed
1586 * else, the number of pages reclaimed
1588 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
1589 struct scan_control
*sc
)
1592 unsigned long ret
= 0;
1593 unsigned long total_scanned
= 0;
1594 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
1595 unsigned long lru_pages
= 0;
1598 enum zone_type high_zoneidx
= gfp_zone(sc
->gfp_mask
);
1600 delayacct_freepages_start();
1602 if (scan_global_lru(sc
))
1603 count_vm_event(ALLOCSTALL
);
1605 * mem_cgroup will not do shrink_slab.
1607 if (scan_global_lru(sc
)) {
1608 for_each_zone_zonelist(zone
, z
, zonelist
, high_zoneidx
) {
1610 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1613 lru_pages
+= zone_lru_pages(zone
);
1617 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
1620 disable_swap_token();
1621 shrink_zones(priority
, zonelist
, sc
);
1623 * Don't shrink slabs when reclaiming memory from
1624 * over limit cgroups
1626 if (scan_global_lru(sc
)) {
1627 shrink_slab(sc
->nr_scanned
, sc
->gfp_mask
, lru_pages
);
1628 if (reclaim_state
) {
1629 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
1630 reclaim_state
->reclaimed_slab
= 0;
1633 total_scanned
+= sc
->nr_scanned
;
1634 if (sc
->nr_reclaimed
>= sc
->swap_cluster_max
) {
1635 ret
= sc
->nr_reclaimed
;
1640 * Try to write back as many pages as we just scanned. This
1641 * tends to cause slow streaming writers to write data to the
1642 * disk smoothly, at the dirtying rate, which is nice. But
1643 * that's undesirable in laptop mode, where we *want* lumpy
1644 * writeout. So in laptop mode, write out the whole world.
1646 if (total_scanned
> sc
->swap_cluster_max
+
1647 sc
->swap_cluster_max
/ 2) {
1648 wakeup_pdflush(laptop_mode
? 0 : total_scanned
);
1649 sc
->may_writepage
= 1;
1652 /* Take a nap, wait for some writeback to complete */
1653 if (sc
->nr_scanned
&& priority
< DEF_PRIORITY
- 2)
1654 congestion_wait(WRITE
, HZ
/10);
1656 /* top priority shrink_zones still had more to do? don't OOM, then */
1657 if (!sc
->all_unreclaimable
&& scan_global_lru(sc
))
1658 ret
= sc
->nr_reclaimed
;
1661 * Now that we've scanned all the zones at this priority level, note
1662 * that level within the zone so that the next thread which performs
1663 * scanning of this zone will immediately start out at this priority
1664 * level. This affects only the decision whether or not to bring
1665 * mapped pages onto the inactive list.
1670 if (scan_global_lru(sc
)) {
1671 for_each_zone_zonelist(zone
, z
, zonelist
, high_zoneidx
) {
1673 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1676 zone
->prev_priority
= priority
;
1679 mem_cgroup_record_reclaim_priority(sc
->mem_cgroup
, priority
);
1681 delayacct_freepages_end();
1686 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
1689 struct scan_control sc
= {
1690 .gfp_mask
= gfp_mask
,
1691 .may_writepage
= !laptop_mode
,
1692 .swap_cluster_max
= SWAP_CLUSTER_MAX
,
1694 .swappiness
= vm_swappiness
,
1697 .isolate_pages
= isolate_pages_global
,
1700 return do_try_to_free_pages(zonelist
, &sc
);
1703 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1705 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*mem_cont
,
1709 struct scan_control sc
= {
1710 .may_writepage
= !laptop_mode
,
1712 .swap_cluster_max
= SWAP_CLUSTER_MAX
,
1713 .swappiness
= vm_swappiness
,
1715 .mem_cgroup
= mem_cont
,
1716 .isolate_pages
= mem_cgroup_isolate_pages
,
1718 struct zonelist
*zonelist
;
1723 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
1724 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
1725 zonelist
= NODE_DATA(numa_node_id())->node_zonelists
;
1726 return do_try_to_free_pages(zonelist
, &sc
);
1731 * For kswapd, balance_pgdat() will work across all this node's zones until
1732 * they are all at pages_high.
1734 * Returns the number of pages which were actually freed.
1736 * There is special handling here for zones which are full of pinned pages.
1737 * This can happen if the pages are all mlocked, or if they are all used by
1738 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1739 * What we do is to detect the case where all pages in the zone have been
1740 * scanned twice and there has been zero successful reclaim. Mark the zone as
1741 * dead and from now on, only perform a short scan. Basically we're polling
1742 * the zone for when the problem goes away.
1744 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1745 * zones which have free_pages > pages_high, but once a zone is found to have
1746 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1747 * of the number of free pages in the lower zones. This interoperates with
1748 * the page allocator fallback scheme to ensure that aging of pages is balanced
1751 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
)
1756 unsigned long total_scanned
;
1757 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
1758 struct scan_control sc
= {
1759 .gfp_mask
= GFP_KERNEL
,
1761 .swap_cluster_max
= SWAP_CLUSTER_MAX
,
1762 .swappiness
= vm_swappiness
,
1765 .isolate_pages
= isolate_pages_global
,
1768 * temp_priority is used to remember the scanning priority at which
1769 * this zone was successfully refilled to free_pages == pages_high.
1771 int temp_priority
[MAX_NR_ZONES
];
1775 sc
.nr_reclaimed
= 0;
1776 sc
.may_writepage
= !laptop_mode
;
1777 count_vm_event(PAGEOUTRUN
);
1779 for (i
= 0; i
< pgdat
->nr_zones
; i
++)
1780 temp_priority
[i
] = DEF_PRIORITY
;
1782 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
1783 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
1784 unsigned long lru_pages
= 0;
1786 /* The swap token gets in the way of swapout... */
1788 disable_swap_token();
1793 * Scan in the highmem->dma direction for the highest
1794 * zone which needs scanning
1796 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
1797 struct zone
*zone
= pgdat
->node_zones
+ i
;
1799 if (!populated_zone(zone
))
1802 if (zone_is_all_unreclaimable(zone
) &&
1803 priority
!= DEF_PRIORITY
)
1807 * Do some background aging of the anon list, to give
1808 * pages a chance to be referenced before reclaiming.
1810 if (inactive_anon_is_low(zone
))
1811 shrink_active_list(SWAP_CLUSTER_MAX
, zone
,
1814 if (!zone_watermark_ok(zone
, order
, zone
->pages_high
,
1823 for (i
= 0; i
<= end_zone
; i
++) {
1824 struct zone
*zone
= pgdat
->node_zones
+ i
;
1826 lru_pages
+= zone_lru_pages(zone
);
1830 * Now scan the zone in the dma->highmem direction, stopping
1831 * at the last zone which needs scanning.
1833 * We do this because the page allocator works in the opposite
1834 * direction. This prevents the page allocator from allocating
1835 * pages behind kswapd's direction of progress, which would
1836 * cause too much scanning of the lower zones.
1838 for (i
= 0; i
<= end_zone
; i
++) {
1839 struct zone
*zone
= pgdat
->node_zones
+ i
;
1842 if (!populated_zone(zone
))
1845 if (zone_is_all_unreclaimable(zone
) &&
1846 priority
!= DEF_PRIORITY
)
1849 if (!zone_watermark_ok(zone
, order
, zone
->pages_high
,
1852 temp_priority
[i
] = priority
;
1854 note_zone_scanning_priority(zone
, priority
);
1856 * We put equal pressure on every zone, unless one
1857 * zone has way too many pages free already.
1859 if (!zone_watermark_ok(zone
, order
, 8*zone
->pages_high
,
1861 shrink_zone(priority
, zone
, &sc
);
1862 reclaim_state
->reclaimed_slab
= 0;
1863 nr_slab
= shrink_slab(sc
.nr_scanned
, GFP_KERNEL
,
1865 sc
.nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
1866 total_scanned
+= sc
.nr_scanned
;
1867 if (zone_is_all_unreclaimable(zone
))
1869 if (nr_slab
== 0 && zone
->pages_scanned
>=
1870 (zone_lru_pages(zone
) * 6))
1872 ZONE_ALL_UNRECLAIMABLE
);
1874 * If we've done a decent amount of scanning and
1875 * the reclaim ratio is low, start doing writepage
1876 * even in laptop mode
1878 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
1879 total_scanned
> sc
.nr_reclaimed
+ sc
.nr_reclaimed
/ 2)
1880 sc
.may_writepage
= 1;
1883 break; /* kswapd: all done */
1885 * OK, kswapd is getting into trouble. Take a nap, then take
1886 * another pass across the zones.
1888 if (total_scanned
&& priority
< DEF_PRIORITY
- 2)
1889 congestion_wait(WRITE
, HZ
/10);
1892 * We do this so kswapd doesn't build up large priorities for
1893 * example when it is freeing in parallel with allocators. It
1894 * matches the direct reclaim path behaviour in terms of impact
1895 * on zone->*_priority.
1897 if (sc
.nr_reclaimed
>= SWAP_CLUSTER_MAX
)
1902 * Note within each zone the priority level at which this zone was
1903 * brought into a happy state. So that the next thread which scans this
1904 * zone will start out at that priority level.
1906 for (i
= 0; i
< pgdat
->nr_zones
; i
++) {
1907 struct zone
*zone
= pgdat
->node_zones
+ i
;
1909 zone
->prev_priority
= temp_priority
[i
];
1911 if (!all_zones_ok
) {
1917 * Fragmentation may mean that the system cannot be
1918 * rebalanced for high-order allocations in all zones.
1919 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
1920 * it means the zones have been fully scanned and are still
1921 * not balanced. For high-order allocations, there is
1922 * little point trying all over again as kswapd may
1925 * Instead, recheck all watermarks at order-0 as they
1926 * are the most important. If watermarks are ok, kswapd will go
1927 * back to sleep. High-order users can still perform direct
1928 * reclaim if they wish.
1930 if (sc
.nr_reclaimed
< SWAP_CLUSTER_MAX
)
1931 order
= sc
.order
= 0;
1936 return sc
.nr_reclaimed
;
1940 * The background pageout daemon, started as a kernel thread
1941 * from the init process.
1943 * This basically trickles out pages so that we have _some_
1944 * free memory available even if there is no other activity
1945 * that frees anything up. This is needed for things like routing
1946 * etc, where we otherwise might have all activity going on in
1947 * asynchronous contexts that cannot page things out.
1949 * If there are applications that are active memory-allocators
1950 * (most normal use), this basically shouldn't matter.
1952 static int kswapd(void *p
)
1954 unsigned long order
;
1955 pg_data_t
*pgdat
= (pg_data_t
*)p
;
1956 struct task_struct
*tsk
= current
;
1958 struct reclaim_state reclaim_state
= {
1959 .reclaimed_slab
= 0,
1961 node_to_cpumask_ptr(cpumask
, pgdat
->node_id
);
1963 if (!cpumask_empty(cpumask
))
1964 set_cpus_allowed_ptr(tsk
, cpumask
);
1965 current
->reclaim_state
= &reclaim_state
;
1968 * Tell the memory management that we're a "memory allocator",
1969 * and that if we need more memory we should get access to it
1970 * regardless (see "__alloc_pages()"). "kswapd" should
1971 * never get caught in the normal page freeing logic.
1973 * (Kswapd normally doesn't need memory anyway, but sometimes
1974 * you need a small amount of memory in order to be able to
1975 * page out something else, and this flag essentially protects
1976 * us from recursively trying to free more memory as we're
1977 * trying to free the first piece of memory in the first place).
1979 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
1984 unsigned long new_order
;
1986 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
1987 new_order
= pgdat
->kswapd_max_order
;
1988 pgdat
->kswapd_max_order
= 0;
1989 if (order
< new_order
) {
1991 * Don't sleep if someone wants a larger 'order'
1996 if (!freezing(current
))
1999 order
= pgdat
->kswapd_max_order
;
2001 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2003 if (!try_to_freeze()) {
2004 /* We can speed up thawing tasks if we don't call
2005 * balance_pgdat after returning from the refrigerator
2007 balance_pgdat(pgdat
, order
);
2014 * A zone is low on free memory, so wake its kswapd task to service it.
2016 void wakeup_kswapd(struct zone
*zone
, int order
)
2020 if (!populated_zone(zone
))
2023 pgdat
= zone
->zone_pgdat
;
2024 if (zone_watermark_ok(zone
, order
, zone
->pages_low
, 0, 0))
2026 if (pgdat
->kswapd_max_order
< order
)
2027 pgdat
->kswapd_max_order
= order
;
2028 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2030 if (!waitqueue_active(&pgdat
->kswapd_wait
))
2032 wake_up_interruptible(&pgdat
->kswapd_wait
);
2035 unsigned long global_lru_pages(void)
2037 return global_page_state(NR_ACTIVE_ANON
)
2038 + global_page_state(NR_ACTIVE_FILE
)
2039 + global_page_state(NR_INACTIVE_ANON
)
2040 + global_page_state(NR_INACTIVE_FILE
);
2045 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
2046 * from LRU lists system-wide, for given pass and priority, and returns the
2047 * number of reclaimed pages
2049 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
2051 static unsigned long shrink_all_zones(unsigned long nr_pages
, int prio
,
2052 int pass
, struct scan_control
*sc
)
2055 unsigned long nr_to_scan
, ret
= 0;
2058 for_each_zone(zone
) {
2060 if (!populated_zone(zone
))
2063 if (zone_is_all_unreclaimable(zone
) && prio
!= DEF_PRIORITY
)
2066 for_each_evictable_lru(l
) {
2067 /* For pass = 0, we don't shrink the active list */
2069 (l
== LRU_ACTIVE
|| l
== LRU_ACTIVE_FILE
))
2072 zone
->lru
[l
].nr_scan
+=
2073 (zone_page_state(zone
, NR_LRU_BASE
+ l
)
2075 if (zone
->lru
[l
].nr_scan
>= nr_pages
|| pass
> 3) {
2076 zone
->lru
[l
].nr_scan
= 0;
2077 nr_to_scan
= min(nr_pages
,
2078 zone_page_state(zone
,
2080 ret
+= shrink_list(l
, nr_to_scan
, zone
,
2082 if (ret
>= nr_pages
)
2092 * Try to free `nr_pages' of memory, system-wide, and return the number of
2095 * Rather than trying to age LRUs the aim is to preserve the overall
2096 * LRU order by reclaiming preferentially
2097 * inactive > active > active referenced > active mapped
2099 unsigned long shrink_all_memory(unsigned long nr_pages
)
2101 unsigned long lru_pages
, nr_slab
;
2102 unsigned long ret
= 0;
2104 struct reclaim_state reclaim_state
;
2105 struct scan_control sc
= {
2106 .gfp_mask
= GFP_KERNEL
,
2108 .swap_cluster_max
= nr_pages
,
2110 .swappiness
= vm_swappiness
,
2111 .isolate_pages
= isolate_pages_global
,
2114 current
->reclaim_state
= &reclaim_state
;
2116 lru_pages
= global_lru_pages();
2117 nr_slab
= global_page_state(NR_SLAB_RECLAIMABLE
);
2118 /* If slab caches are huge, it's better to hit them first */
2119 while (nr_slab
>= lru_pages
) {
2120 reclaim_state
.reclaimed_slab
= 0;
2121 shrink_slab(nr_pages
, sc
.gfp_mask
, lru_pages
);
2122 if (!reclaim_state
.reclaimed_slab
)
2125 ret
+= reclaim_state
.reclaimed_slab
;
2126 if (ret
>= nr_pages
)
2129 nr_slab
-= reclaim_state
.reclaimed_slab
;
2133 * We try to shrink LRUs in 5 passes:
2134 * 0 = Reclaim from inactive_list only
2135 * 1 = Reclaim from active list but don't reclaim mapped
2136 * 2 = 2nd pass of type 1
2137 * 3 = Reclaim mapped (normal reclaim)
2138 * 4 = 2nd pass of type 3
2140 for (pass
= 0; pass
< 5; pass
++) {
2143 /* Force reclaiming mapped pages in the passes #3 and #4 */
2146 sc
.swappiness
= 100;
2149 for (prio
= DEF_PRIORITY
; prio
>= 0; prio
--) {
2150 unsigned long nr_to_scan
= nr_pages
- ret
;
2153 ret
+= shrink_all_zones(nr_to_scan
, prio
, pass
, &sc
);
2154 if (ret
>= nr_pages
)
2157 reclaim_state
.reclaimed_slab
= 0;
2158 shrink_slab(sc
.nr_scanned
, sc
.gfp_mask
,
2159 global_lru_pages());
2160 ret
+= reclaim_state
.reclaimed_slab
;
2161 if (ret
>= nr_pages
)
2164 if (sc
.nr_scanned
&& prio
< DEF_PRIORITY
- 2)
2165 congestion_wait(WRITE
, HZ
/ 10);
2170 * If ret = 0, we could not shrink LRUs, but there may be something
2175 reclaim_state
.reclaimed_slab
= 0;
2176 shrink_slab(nr_pages
, sc
.gfp_mask
, global_lru_pages());
2177 ret
+= reclaim_state
.reclaimed_slab
;
2178 } while (ret
< nr_pages
&& reclaim_state
.reclaimed_slab
> 0);
2182 current
->reclaim_state
= NULL
;
2188 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2189 not required for correctness. So if the last cpu in a node goes
2190 away, we get changed to run anywhere: as the first one comes back,
2191 restore their cpu bindings. */
2192 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
2193 unsigned long action
, void *hcpu
)
2197 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
2198 for_each_node_state(nid
, N_HIGH_MEMORY
) {
2199 pg_data_t
*pgdat
= NODE_DATA(nid
);
2200 node_to_cpumask_ptr(mask
, pgdat
->node_id
);
2202 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
2203 /* One of our CPUs online: restore mask */
2204 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
2211 * This kswapd start function will be called by init and node-hot-add.
2212 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2214 int kswapd_run(int nid
)
2216 pg_data_t
*pgdat
= NODE_DATA(nid
);
2222 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
2223 if (IS_ERR(pgdat
->kswapd
)) {
2224 /* failure at boot is fatal */
2225 BUG_ON(system_state
== SYSTEM_BOOTING
);
2226 printk("Failed to start kswapd on node %d\n",nid
);
2232 static int __init
kswapd_init(void)
2237 for_each_node_state(nid
, N_HIGH_MEMORY
)
2239 hotcpu_notifier(cpu_callback
, 0);
2243 module_init(kswapd_init
)
2249 * If non-zero call zone_reclaim when the number of free pages falls below
2252 int zone_reclaim_mode __read_mostly
;
2254 #define RECLAIM_OFF 0
2255 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2256 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2257 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2260 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2261 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2264 #define ZONE_RECLAIM_PRIORITY 4
2267 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2270 int sysctl_min_unmapped_ratio
= 1;
2273 * If the number of slab pages in a zone grows beyond this percentage then
2274 * slab reclaim needs to occur.
2276 int sysctl_min_slab_ratio
= 5;
2279 * Try to free up some pages from this zone through reclaim.
2281 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2283 /* Minimum pages needed in order to stay on node */
2284 const unsigned long nr_pages
= 1 << order
;
2285 struct task_struct
*p
= current
;
2286 struct reclaim_state reclaim_state
;
2288 struct scan_control sc
= {
2289 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
2290 .may_swap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
2291 .swap_cluster_max
= max_t(unsigned long, nr_pages
,
2293 .gfp_mask
= gfp_mask
,
2294 .swappiness
= vm_swappiness
,
2295 .isolate_pages
= isolate_pages_global
,
2297 unsigned long slab_reclaimable
;
2299 disable_swap_token();
2302 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2303 * and we also need to be able to write out pages for RECLAIM_WRITE
2306 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
2307 reclaim_state
.reclaimed_slab
= 0;
2308 p
->reclaim_state
= &reclaim_state
;
2310 if (zone_page_state(zone
, NR_FILE_PAGES
) -
2311 zone_page_state(zone
, NR_FILE_MAPPED
) >
2312 zone
->min_unmapped_pages
) {
2314 * Free memory by calling shrink zone with increasing
2315 * priorities until we have enough memory freed.
2317 priority
= ZONE_RECLAIM_PRIORITY
;
2319 note_zone_scanning_priority(zone
, priority
);
2320 shrink_zone(priority
, zone
, &sc
);
2322 } while (priority
>= 0 && sc
.nr_reclaimed
< nr_pages
);
2325 slab_reclaimable
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
2326 if (slab_reclaimable
> zone
->min_slab_pages
) {
2328 * shrink_slab() does not currently allow us to determine how
2329 * many pages were freed in this zone. So we take the current
2330 * number of slab pages and shake the slab until it is reduced
2331 * by the same nr_pages that we used for reclaiming unmapped
2334 * Note that shrink_slab will free memory on all zones and may
2337 while (shrink_slab(sc
.nr_scanned
, gfp_mask
, order
) &&
2338 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) >
2339 slab_reclaimable
- nr_pages
)
2343 * Update nr_reclaimed by the number of slab pages we
2344 * reclaimed from this zone.
2346 sc
.nr_reclaimed
+= slab_reclaimable
-
2347 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
2350 p
->reclaim_state
= NULL
;
2351 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
2352 return sc
.nr_reclaimed
>= nr_pages
;
2355 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2361 * Zone reclaim reclaims unmapped file backed pages and
2362 * slab pages if we are over the defined limits.
2364 * A small portion of unmapped file backed pages is needed for
2365 * file I/O otherwise pages read by file I/O will be immediately
2366 * thrown out if the zone is overallocated. So we do not reclaim
2367 * if less than a specified percentage of the zone is used by
2368 * unmapped file backed pages.
2370 if (zone_page_state(zone
, NR_FILE_PAGES
) -
2371 zone_page_state(zone
, NR_FILE_MAPPED
) <= zone
->min_unmapped_pages
2372 && zone_page_state(zone
, NR_SLAB_RECLAIMABLE
)
2373 <= zone
->min_slab_pages
)
2376 if (zone_is_all_unreclaimable(zone
))
2380 * Do not scan if the allocation should not be delayed.
2382 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
2386 * Only run zone reclaim on the local zone or on zones that do not
2387 * have associated processors. This will favor the local processor
2388 * over remote processors and spread off node memory allocations
2389 * as wide as possible.
2391 node_id
= zone_to_nid(zone
);
2392 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
2395 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
2397 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
2398 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
2404 #ifdef CONFIG_UNEVICTABLE_LRU
2406 * page_evictable - test whether a page is evictable
2407 * @page: the page to test
2408 * @vma: the VMA in which the page is or will be mapped, may be NULL
2410 * Test whether page is evictable--i.e., should be placed on active/inactive
2411 * lists vs unevictable list. The vma argument is !NULL when called from the
2412 * fault path to determine how to instantate a new page.
2414 * Reasons page might not be evictable:
2415 * (1) page's mapping marked unevictable
2416 * (2) page is part of an mlocked VMA
2419 int page_evictable(struct page
*page
, struct vm_area_struct
*vma
)
2422 if (mapping_unevictable(page_mapping(page
)))
2425 if (PageMlocked(page
) || (vma
&& is_mlocked_vma(vma
, page
)))
2432 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2433 * @page: page to check evictability and move to appropriate lru list
2434 * @zone: zone page is in
2436 * Checks a page for evictability and moves the page to the appropriate
2439 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2440 * have PageUnevictable set.
2442 static void check_move_unevictable_page(struct page
*page
, struct zone
*zone
)
2444 VM_BUG_ON(PageActive(page
));
2447 ClearPageUnevictable(page
);
2448 if (page_evictable(page
, NULL
)) {
2449 enum lru_list l
= LRU_INACTIVE_ANON
+ page_is_file_cache(page
);
2451 __dec_zone_state(zone
, NR_UNEVICTABLE
);
2452 list_move(&page
->lru
, &zone
->lru
[l
].list
);
2453 mem_cgroup_move_lists(page
, LRU_UNEVICTABLE
, l
);
2454 __inc_zone_state(zone
, NR_INACTIVE_ANON
+ l
);
2455 __count_vm_event(UNEVICTABLE_PGRESCUED
);
2458 * rotate unevictable list
2460 SetPageUnevictable(page
);
2461 list_move(&page
->lru
, &zone
->lru
[LRU_UNEVICTABLE
].list
);
2462 mem_cgroup_rotate_lru_list(page
, LRU_UNEVICTABLE
);
2463 if (page_evictable(page
, NULL
))
2469 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2470 * @mapping: struct address_space to scan for evictable pages
2472 * Scan all pages in mapping. Check unevictable pages for
2473 * evictability and move them to the appropriate zone lru list.
2475 void scan_mapping_unevictable_pages(struct address_space
*mapping
)
2478 pgoff_t end
= (i_size_read(mapping
->host
) + PAGE_CACHE_SIZE
- 1) >>
2481 struct pagevec pvec
;
2483 if (mapping
->nrpages
== 0)
2486 pagevec_init(&pvec
, 0);
2487 while (next
< end
&&
2488 pagevec_lookup(&pvec
, mapping
, next
, PAGEVEC_SIZE
)) {
2494 for (i
= 0; i
< pagevec_count(&pvec
); i
++) {
2495 struct page
*page
= pvec
.pages
[i
];
2496 pgoff_t page_index
= page
->index
;
2497 struct zone
*pagezone
= page_zone(page
);
2500 if (page_index
> next
)
2504 if (pagezone
!= zone
) {
2506 spin_unlock_irq(&zone
->lru_lock
);
2508 spin_lock_irq(&zone
->lru_lock
);
2511 if (PageLRU(page
) && PageUnevictable(page
))
2512 check_move_unevictable_page(page
, zone
);
2515 spin_unlock_irq(&zone
->lru_lock
);
2516 pagevec_release(&pvec
);
2518 count_vm_events(UNEVICTABLE_PGSCANNED
, pg_scanned
);
2524 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2525 * @zone - zone of which to scan the unevictable list
2527 * Scan @zone's unevictable LRU lists to check for pages that have become
2528 * evictable. Move those that have to @zone's inactive list where they
2529 * become candidates for reclaim, unless shrink_inactive_zone() decides
2530 * to reactivate them. Pages that are still unevictable are rotated
2531 * back onto @zone's unevictable list.
2533 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2534 static void scan_zone_unevictable_pages(struct zone
*zone
)
2536 struct list_head
*l_unevictable
= &zone
->lru
[LRU_UNEVICTABLE
].list
;
2538 unsigned long nr_to_scan
= zone_page_state(zone
, NR_UNEVICTABLE
);
2540 while (nr_to_scan
> 0) {
2541 unsigned long batch_size
= min(nr_to_scan
,
2542 SCAN_UNEVICTABLE_BATCH_SIZE
);
2544 spin_lock_irq(&zone
->lru_lock
);
2545 for (scan
= 0; scan
< batch_size
; scan
++) {
2546 struct page
*page
= lru_to_page(l_unevictable
);
2548 if (!trylock_page(page
))
2551 prefetchw_prev_lru_page(page
, l_unevictable
, flags
);
2553 if (likely(PageLRU(page
) && PageUnevictable(page
)))
2554 check_move_unevictable_page(page
, zone
);
2558 spin_unlock_irq(&zone
->lru_lock
);
2560 nr_to_scan
-= batch_size
;
2566 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2568 * A really big hammer: scan all zones' unevictable LRU lists to check for
2569 * pages that have become evictable. Move those back to the zones'
2570 * inactive list where they become candidates for reclaim.
2571 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2572 * and we add swap to the system. As such, it runs in the context of a task
2573 * that has possibly/probably made some previously unevictable pages
2576 static void scan_all_zones_unevictable_pages(void)
2580 for_each_zone(zone
) {
2581 scan_zone_unevictable_pages(zone
);
2586 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2587 * all nodes' unevictable lists for evictable pages
2589 unsigned long scan_unevictable_pages
;
2591 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
2592 struct file
*file
, void __user
*buffer
,
2593 size_t *length
, loff_t
*ppos
)
2595 proc_doulongvec_minmax(table
, write
, file
, buffer
, length
, ppos
);
2597 if (write
&& *(unsigned long *)table
->data
)
2598 scan_all_zones_unevictable_pages();
2600 scan_unevictable_pages
= 0;
2605 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2606 * a specified node's per zone unevictable lists for evictable pages.
2609 static ssize_t
read_scan_unevictable_node(struct sys_device
*dev
,
2610 struct sysdev_attribute
*attr
,
2613 return sprintf(buf
, "0\n"); /* always zero; should fit... */
2616 static ssize_t
write_scan_unevictable_node(struct sys_device
*dev
,
2617 struct sysdev_attribute
*attr
,
2618 const char *buf
, size_t count
)
2620 struct zone
*node_zones
= NODE_DATA(dev
->id
)->node_zones
;
2623 unsigned long req
= strict_strtoul(buf
, 10, &res
);
2626 return 1; /* zero is no-op */
2628 for (zone
= node_zones
; zone
- node_zones
< MAX_NR_ZONES
; ++zone
) {
2629 if (!populated_zone(zone
))
2631 scan_zone_unevictable_pages(zone
);
2637 static SYSDEV_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
2638 read_scan_unevictable_node
,
2639 write_scan_unevictable_node
);
2641 int scan_unevictable_register_node(struct node
*node
)
2643 return sysdev_create_file(&node
->sysdev
, &attr_scan_unevictable_pages
);
2646 void scan_unevictable_unregister_node(struct node
*node
)
2648 sysdev_remove_file(&node
->sysdev
, &attr_scan_unevictable_pages
);