4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
15 #include <linux/module.h>
16 #include <linux/gfp.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/swap.h>
19 #include <linux/pagemap.h>
20 #include <linux/init.h>
21 #include <linux/highmem.h>
22 #include <linux/vmstat.h>
23 #include <linux/file.h>
24 #include <linux/writeback.h>
25 #include <linux/blkdev.h>
26 #include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28 #include <linux/mm_inline.h>
29 #include <linux/pagevec.h>
30 #include <linux/backing-dev.h>
31 #include <linux/rmap.h>
32 #include <linux/topology.h>
33 #include <linux/cpu.h>
34 #include <linux/cpuset.h>
35 #include <linux/compaction.h>
36 #include <linux/notifier.h>
37 #include <linux/rwsem.h>
38 #include <linux/delay.h>
39 #include <linux/kthread.h>
40 #include <linux/freezer.h>
41 #include <linux/memcontrol.h>
42 #include <linux/delayacct.h>
43 #include <linux/sysctl.h>
44 #include <linux/oom.h>
45 #include <linux/prefetch.h>
47 #include <asm/tlbflush.h>
48 #include <asm/div64.h>
50 #include <linux/swapops.h>
54 #define CREATE_TRACE_POINTS
55 #include <trace/events/vmscan.h>
58 * reclaim_mode determines how the inactive list is shrunk
59 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
60 * RECLAIM_MODE_ASYNC: Do not block
61 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback
62 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
63 * page from the LRU and reclaim all pages within a
64 * naturally aligned range
65 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
66 * order-0 pages and then compact the zone
68 typedef unsigned __bitwise__ reclaim_mode_t
;
69 #define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u)
70 #define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u)
71 #define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u)
72 #define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u)
73 #define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u)
76 /* Incremented by the number of inactive pages that were scanned */
77 unsigned long nr_scanned
;
79 /* Number of pages freed so far during a call to shrink_zones() */
80 unsigned long nr_reclaimed
;
82 /* How many pages shrink_list() should reclaim */
83 unsigned long nr_to_reclaim
;
85 unsigned long hibernation_mode
;
87 /* This context's GFP mask */
92 /* Can mapped pages be reclaimed? */
95 /* Can pages be swapped as part of reclaim? */
103 * Intend to reclaim enough continuous memory rather than reclaim
104 * enough amount of memory. i.e, mode for high order allocation.
106 reclaim_mode_t reclaim_mode
;
108 /* Which cgroup do we reclaim from */
109 struct mem_cgroup
*mem_cgroup
;
112 * Nodemask of nodes allowed by the caller. If NULL, all nodes
115 nodemask_t
*nodemask
;
118 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
120 #ifdef ARCH_HAS_PREFETCH
121 #define prefetch_prev_lru_page(_page, _base, _field) \
123 if ((_page)->lru.prev != _base) { \
126 prev = lru_to_page(&(_page->lru)); \
127 prefetch(&prev->_field); \
131 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
134 #ifdef ARCH_HAS_PREFETCHW
135 #define prefetchw_prev_lru_page(_page, _base, _field) \
137 if ((_page)->lru.prev != _base) { \
140 prev = lru_to_page(&(_page->lru)); \
141 prefetchw(&prev->_field); \
145 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
149 * From 0 .. 100. Higher means more swappy.
151 int vm_swappiness
= 60;
152 long vm_total_pages
; /* The total number of pages which the VM controls */
154 static LIST_HEAD(shrinker_list
);
155 static DECLARE_RWSEM(shrinker_rwsem
);
157 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
158 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
160 #define scanning_global_lru(sc) (1)
163 static struct zone_reclaim_stat
*get_reclaim_stat(struct zone
*zone
,
164 struct scan_control
*sc
)
166 if (!scanning_global_lru(sc
))
167 return mem_cgroup_get_reclaim_stat(sc
->mem_cgroup
, zone
);
169 return &zone
->reclaim_stat
;
172 static unsigned long zone_nr_lru_pages(struct zone
*zone
,
173 struct scan_control
*sc
, enum lru_list lru
)
175 if (!scanning_global_lru(sc
))
176 return mem_cgroup_zone_nr_pages(sc
->mem_cgroup
, zone
, lru
);
178 return zone_page_state(zone
, NR_LRU_BASE
+ lru
);
183 * Add a shrinker callback to be called from the vm
185 void register_shrinker(struct shrinker
*shrinker
)
188 down_write(&shrinker_rwsem
);
189 list_add_tail(&shrinker
->list
, &shrinker_list
);
190 up_write(&shrinker_rwsem
);
192 EXPORT_SYMBOL(register_shrinker
);
197 void unregister_shrinker(struct shrinker
*shrinker
)
199 down_write(&shrinker_rwsem
);
200 list_del(&shrinker
->list
);
201 up_write(&shrinker_rwsem
);
203 EXPORT_SYMBOL(unregister_shrinker
);
205 #define SHRINK_BATCH 128
207 * Call the shrink functions to age shrinkable caches
209 * Here we assume it costs one seek to replace a lru page and that it also
210 * takes a seek to recreate a cache object. With this in mind we age equal
211 * percentages of the lru and ageable caches. This should balance the seeks
212 * generated by these structures.
214 * If the vm encountered mapped pages on the LRU it increase the pressure on
215 * slab to avoid swapping.
217 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
219 * `lru_pages' represents the number of on-LRU pages in all the zones which
220 * are eligible for the caller's allocation attempt. It is used for balancing
221 * slab reclaim versus page reclaim.
223 * Returns the number of slab objects which we shrunk.
225 unsigned long shrink_slab(unsigned long scanned
, gfp_t gfp_mask
,
226 unsigned long lru_pages
)
228 struct shrinker
*shrinker
;
229 unsigned long ret
= 0;
232 scanned
= SWAP_CLUSTER_MAX
;
234 if (!down_read_trylock(&shrinker_rwsem
)) {
235 /* Assume we'll be able to shrink next time */
240 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
241 unsigned long long delta
;
242 unsigned long total_scan
;
243 unsigned long max_pass
;
245 max_pass
= (*shrinker
->shrink
)(shrinker
, 0, gfp_mask
);
246 delta
= (4 * scanned
) / shrinker
->seeks
;
248 do_div(delta
, lru_pages
+ 1);
249 shrinker
->nr
+= delta
;
250 if (shrinker
->nr
< 0) {
251 printk(KERN_ERR
"shrink_slab: %pF negative objects to "
253 shrinker
->shrink
, shrinker
->nr
);
254 shrinker
->nr
= max_pass
;
258 * Avoid risking looping forever due to too large nr value:
259 * never try to free more than twice the estimate number of
262 if (shrinker
->nr
> max_pass
* 2)
263 shrinker
->nr
= max_pass
* 2;
265 total_scan
= shrinker
->nr
;
268 while (total_scan
>= SHRINK_BATCH
) {
269 long this_scan
= SHRINK_BATCH
;
273 nr_before
= (*shrinker
->shrink
)(shrinker
, 0, gfp_mask
);
274 shrink_ret
= (*shrinker
->shrink
)(shrinker
, this_scan
,
276 if (shrink_ret
== -1)
278 if (shrink_ret
< nr_before
)
279 ret
+= nr_before
- shrink_ret
;
280 count_vm_events(SLABS_SCANNED
, this_scan
);
281 total_scan
-= this_scan
;
286 shrinker
->nr
+= total_scan
;
288 up_read(&shrinker_rwsem
);
294 static void set_reclaim_mode(int priority
, struct scan_control
*sc
,
297 reclaim_mode_t syncmode
= sync
? RECLAIM_MODE_SYNC
: RECLAIM_MODE_ASYNC
;
300 * Initially assume we are entering either lumpy reclaim or
301 * reclaim/compaction.Depending on the order, we will either set the
302 * sync mode or just reclaim order-0 pages later.
304 if (COMPACTION_BUILD
)
305 sc
->reclaim_mode
= RECLAIM_MODE_COMPACTION
;
307 sc
->reclaim_mode
= RECLAIM_MODE_LUMPYRECLAIM
;
310 * Avoid using lumpy reclaim or reclaim/compaction if possible by
311 * restricting when its set to either costly allocations or when
312 * under memory pressure
314 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
315 sc
->reclaim_mode
|= syncmode
;
316 else if (sc
->order
&& priority
< DEF_PRIORITY
- 2)
317 sc
->reclaim_mode
|= syncmode
;
319 sc
->reclaim_mode
= RECLAIM_MODE_SINGLE
| RECLAIM_MODE_ASYNC
;
322 static void reset_reclaim_mode(struct scan_control
*sc
)
324 sc
->reclaim_mode
= RECLAIM_MODE_SINGLE
| RECLAIM_MODE_ASYNC
;
327 static inline int is_page_cache_freeable(struct page
*page
)
330 * A freeable page cache page is referenced only by the caller
331 * that isolated the page, the page cache radix tree and
332 * optional buffer heads at page->private.
334 return page_count(page
) - page_has_private(page
) == 2;
337 static int may_write_to_queue(struct backing_dev_info
*bdi
,
338 struct scan_control
*sc
)
340 if (current
->flags
& PF_SWAPWRITE
)
342 if (!bdi_write_congested(bdi
))
344 if (bdi
== current
->backing_dev_info
)
347 /* lumpy reclaim for hugepage often need a lot of write */
348 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
354 * We detected a synchronous write error writing a page out. Probably
355 * -ENOSPC. We need to propagate that into the address_space for a subsequent
356 * fsync(), msync() or close().
358 * The tricky part is that after writepage we cannot touch the mapping: nothing
359 * prevents it from being freed up. But we have a ref on the page and once
360 * that page is locked, the mapping is pinned.
362 * We're allowed to run sleeping lock_page() here because we know the caller has
365 static void handle_write_error(struct address_space
*mapping
,
366 struct page
*page
, int error
)
369 if (page_mapping(page
) == mapping
)
370 mapping_set_error(mapping
, error
);
374 /* possible outcome of pageout() */
376 /* failed to write page out, page is locked */
378 /* move page to the active list, page is locked */
380 /* page has been sent to the disk successfully, page is unlocked */
382 /* page is clean and locked */
387 * pageout is called by shrink_page_list() for each dirty page.
388 * Calls ->writepage().
390 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
391 struct scan_control
*sc
)
394 * If the page is dirty, only perform writeback if that write
395 * will be non-blocking. To prevent this allocation from being
396 * stalled by pagecache activity. But note that there may be
397 * stalls if we need to run get_block(). We could test
398 * PagePrivate for that.
400 * If this process is currently in __generic_file_aio_write() against
401 * this page's queue, we can perform writeback even if that
404 * If the page is swapcache, write it back even if that would
405 * block, for some throttling. This happens by accident, because
406 * swap_backing_dev_info is bust: it doesn't reflect the
407 * congestion state of the swapdevs. Easy to fix, if needed.
409 if (!is_page_cache_freeable(page
))
413 * Some data journaling orphaned pages can have
414 * page->mapping == NULL while being dirty with clean buffers.
416 if (page_has_private(page
)) {
417 if (try_to_free_buffers(page
)) {
418 ClearPageDirty(page
);
419 printk("%s: orphaned page\n", __func__
);
425 if (mapping
->a_ops
->writepage
== NULL
)
426 return PAGE_ACTIVATE
;
427 if (!may_write_to_queue(mapping
->backing_dev_info
, sc
))
430 if (clear_page_dirty_for_io(page
)) {
432 struct writeback_control wbc
= {
433 .sync_mode
= WB_SYNC_NONE
,
434 .nr_to_write
= SWAP_CLUSTER_MAX
,
436 .range_end
= LLONG_MAX
,
440 SetPageReclaim(page
);
441 res
= mapping
->a_ops
->writepage(page
, &wbc
);
443 handle_write_error(mapping
, page
, res
);
444 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
445 ClearPageReclaim(page
);
446 return PAGE_ACTIVATE
;
450 * Wait on writeback if requested to. This happens when
451 * direct reclaiming a large contiguous area and the
452 * first attempt to free a range of pages fails.
454 if (PageWriteback(page
) &&
455 (sc
->reclaim_mode
& RECLAIM_MODE_SYNC
))
456 wait_on_page_writeback(page
);
458 if (!PageWriteback(page
)) {
459 /* synchronous write or broken a_ops? */
460 ClearPageReclaim(page
);
462 trace_mm_vmscan_writepage(page
,
463 trace_reclaim_flags(page
, sc
->reclaim_mode
));
464 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
472 * Same as remove_mapping, but if the page is removed from the mapping, it
473 * gets returned with a refcount of 0.
475 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
)
477 BUG_ON(!PageLocked(page
));
478 BUG_ON(mapping
!= page_mapping(page
));
480 spin_lock_irq(&mapping
->tree_lock
);
482 * The non racy check for a busy page.
484 * Must be careful with the order of the tests. When someone has
485 * a ref to the page, it may be possible that they dirty it then
486 * drop the reference. So if PageDirty is tested before page_count
487 * here, then the following race may occur:
489 * get_user_pages(&page);
490 * [user mapping goes away]
492 * !PageDirty(page) [good]
493 * SetPageDirty(page);
495 * !page_count(page) [good, discard it]
497 * [oops, our write_to data is lost]
499 * Reversing the order of the tests ensures such a situation cannot
500 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
501 * load is not satisfied before that of page->_count.
503 * Note that if SetPageDirty is always performed via set_page_dirty,
504 * and thus under tree_lock, then this ordering is not required.
506 if (!page_freeze_refs(page
, 2))
508 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
509 if (unlikely(PageDirty(page
))) {
510 page_unfreeze_refs(page
, 2);
514 if (PageSwapCache(page
)) {
515 swp_entry_t swap
= { .val
= page_private(page
) };
516 __delete_from_swap_cache(page
);
517 spin_unlock_irq(&mapping
->tree_lock
);
518 swapcache_free(swap
, page
);
520 void (*freepage
)(struct page
*);
522 freepage
= mapping
->a_ops
->freepage
;
524 __delete_from_page_cache(page
);
525 spin_unlock_irq(&mapping
->tree_lock
);
526 mem_cgroup_uncharge_cache_page(page
);
528 if (freepage
!= NULL
)
535 spin_unlock_irq(&mapping
->tree_lock
);
540 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
541 * someone else has a ref on the page, abort and return 0. If it was
542 * successfully detached, return 1. Assumes the caller has a single ref on
545 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
547 if (__remove_mapping(mapping
, page
)) {
549 * Unfreezing the refcount with 1 rather than 2 effectively
550 * drops the pagecache ref for us without requiring another
553 page_unfreeze_refs(page
, 1);
560 * putback_lru_page - put previously isolated page onto appropriate LRU list
561 * @page: page to be put back to appropriate lru list
563 * Add previously isolated @page to appropriate LRU list.
564 * Page may still be unevictable for other reasons.
566 * lru_lock must not be held, interrupts must be enabled.
568 void putback_lru_page(struct page
*page
)
571 int active
= !!TestClearPageActive(page
);
572 int was_unevictable
= PageUnevictable(page
);
574 VM_BUG_ON(PageLRU(page
));
577 ClearPageUnevictable(page
);
579 if (page_evictable(page
, NULL
)) {
581 * For evictable pages, we can use the cache.
582 * In event of a race, worst case is we end up with an
583 * unevictable page on [in]active list.
584 * We know how to handle that.
586 lru
= active
+ page_lru_base_type(page
);
587 lru_cache_add_lru(page
, lru
);
590 * Put unevictable pages directly on zone's unevictable
593 lru
= LRU_UNEVICTABLE
;
594 add_page_to_unevictable_list(page
);
596 * When racing with an mlock clearing (page is
597 * unlocked), make sure that if the other thread does
598 * not observe our setting of PG_lru and fails
599 * isolation, we see PG_mlocked cleared below and move
600 * the page back to the evictable list.
602 * The other side is TestClearPageMlocked().
608 * page's status can change while we move it among lru. If an evictable
609 * page is on unevictable list, it never be freed. To avoid that,
610 * check after we added it to the list, again.
612 if (lru
== LRU_UNEVICTABLE
&& page_evictable(page
, NULL
)) {
613 if (!isolate_lru_page(page
)) {
617 /* This means someone else dropped this page from LRU
618 * So, it will be freed or putback to LRU again. There is
619 * nothing to do here.
623 if (was_unevictable
&& lru
!= LRU_UNEVICTABLE
)
624 count_vm_event(UNEVICTABLE_PGRESCUED
);
625 else if (!was_unevictable
&& lru
== LRU_UNEVICTABLE
)
626 count_vm_event(UNEVICTABLE_PGCULLED
);
628 put_page(page
); /* drop ref from isolate */
631 enum page_references
{
633 PAGEREF_RECLAIM_CLEAN
,
638 static enum page_references
page_check_references(struct page
*page
,
639 struct scan_control
*sc
)
641 int referenced_ptes
, referenced_page
;
642 unsigned long vm_flags
;
644 referenced_ptes
= page_referenced(page
, 1, sc
->mem_cgroup
, &vm_flags
);
645 referenced_page
= TestClearPageReferenced(page
);
647 /* Lumpy reclaim - ignore references */
648 if (sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
)
649 return PAGEREF_RECLAIM
;
652 * Mlock lost the isolation race with us. Let try_to_unmap()
653 * move the page to the unevictable list.
655 if (vm_flags
& VM_LOCKED
)
656 return PAGEREF_RECLAIM
;
658 if (referenced_ptes
) {
660 return PAGEREF_ACTIVATE
;
662 * All mapped pages start out with page table
663 * references from the instantiating fault, so we need
664 * to look twice if a mapped file page is used more
667 * Mark it and spare it for another trip around the
668 * inactive list. Another page table reference will
669 * lead to its activation.
671 * Note: the mark is set for activated pages as well
672 * so that recently deactivated but used pages are
675 SetPageReferenced(page
);
678 return PAGEREF_ACTIVATE
;
683 /* Reclaim if clean, defer dirty pages to writeback */
684 if (referenced_page
&& !PageSwapBacked(page
))
685 return PAGEREF_RECLAIM_CLEAN
;
687 return PAGEREF_RECLAIM
;
690 static noinline_for_stack
void free_page_list(struct list_head
*free_pages
)
692 struct pagevec freed_pvec
;
693 struct page
*page
, *tmp
;
695 pagevec_init(&freed_pvec
, 1);
697 list_for_each_entry_safe(page
, tmp
, free_pages
, lru
) {
698 list_del(&page
->lru
);
699 if (!pagevec_add(&freed_pvec
, page
)) {
700 __pagevec_free(&freed_pvec
);
701 pagevec_reinit(&freed_pvec
);
705 pagevec_free(&freed_pvec
);
709 * shrink_page_list() returns the number of reclaimed pages
711 static unsigned long shrink_page_list(struct list_head
*page_list
,
713 struct scan_control
*sc
)
715 LIST_HEAD(ret_pages
);
716 LIST_HEAD(free_pages
);
718 unsigned long nr_dirty
= 0;
719 unsigned long nr_congested
= 0;
720 unsigned long nr_reclaimed
= 0;
724 while (!list_empty(page_list
)) {
725 enum page_references references
;
726 struct address_space
*mapping
;
732 page
= lru_to_page(page_list
);
733 list_del(&page
->lru
);
735 if (!trylock_page(page
))
738 VM_BUG_ON(PageActive(page
));
739 VM_BUG_ON(page_zone(page
) != zone
);
743 if (unlikely(!page_evictable(page
, NULL
)))
746 if (!sc
->may_unmap
&& page_mapped(page
))
749 /* Double the slab pressure for mapped and swapcache pages */
750 if (page_mapped(page
) || PageSwapCache(page
))
753 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
754 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
756 if (PageWriteback(page
)) {
758 * Synchronous reclaim is performed in two passes,
759 * first an asynchronous pass over the list to
760 * start parallel writeback, and a second synchronous
761 * pass to wait for the IO to complete. Wait here
762 * for any page for which writeback has already
765 if ((sc
->reclaim_mode
& RECLAIM_MODE_SYNC
) &&
767 wait_on_page_writeback(page
);
774 references
= page_check_references(page
, sc
);
775 switch (references
) {
776 case PAGEREF_ACTIVATE
:
777 goto activate_locked
;
780 case PAGEREF_RECLAIM
:
781 case PAGEREF_RECLAIM_CLEAN
:
782 ; /* try to reclaim the page below */
786 * Anonymous process memory has backing store?
787 * Try to allocate it some swap space here.
789 if (PageAnon(page
) && !PageSwapCache(page
)) {
790 if (!(sc
->gfp_mask
& __GFP_IO
))
792 if (!add_to_swap(page
))
793 goto activate_locked
;
797 mapping
= page_mapping(page
);
800 * The page is mapped into the page tables of one or more
801 * processes. Try to unmap it here.
803 if (page_mapped(page
) && mapping
) {
804 switch (try_to_unmap(page
, TTU_UNMAP
)) {
806 goto activate_locked
;
812 ; /* try to free the page below */
816 if (PageDirty(page
)) {
819 if (references
== PAGEREF_RECLAIM_CLEAN
)
823 if (!sc
->may_writepage
)
826 /* Page is dirty, try to write it out here */
827 switch (pageout(page
, mapping
, sc
)) {
832 goto activate_locked
;
834 if (PageWriteback(page
))
840 * A synchronous write - probably a ramdisk. Go
841 * ahead and try to reclaim the page.
843 if (!trylock_page(page
))
845 if (PageDirty(page
) || PageWriteback(page
))
847 mapping
= page_mapping(page
);
849 ; /* try to free the page below */
854 * If the page has buffers, try to free the buffer mappings
855 * associated with this page. If we succeed we try to free
858 * We do this even if the page is PageDirty().
859 * try_to_release_page() does not perform I/O, but it is
860 * possible for a page to have PageDirty set, but it is actually
861 * clean (all its buffers are clean). This happens if the
862 * buffers were written out directly, with submit_bh(). ext3
863 * will do this, as well as the blockdev mapping.
864 * try_to_release_page() will discover that cleanness and will
865 * drop the buffers and mark the page clean - it can be freed.
867 * Rarely, pages can have buffers and no ->mapping. These are
868 * the pages which were not successfully invalidated in
869 * truncate_complete_page(). We try to drop those buffers here
870 * and if that worked, and the page is no longer mapped into
871 * process address space (page_count == 1) it can be freed.
872 * Otherwise, leave the page on the LRU so it is swappable.
874 if (page_has_private(page
)) {
875 if (!try_to_release_page(page
, sc
->gfp_mask
))
876 goto activate_locked
;
877 if (!mapping
&& page_count(page
) == 1) {
879 if (put_page_testzero(page
))
883 * rare race with speculative reference.
884 * the speculative reference will free
885 * this page shortly, so we may
886 * increment nr_reclaimed here (and
887 * leave it off the LRU).
895 if (!mapping
|| !__remove_mapping(mapping
, page
))
899 * At this point, we have no other references and there is
900 * no way to pick any more up (removed from LRU, removed
901 * from pagecache). Can use non-atomic bitops now (and
902 * we obviously don't have to worry about waking up a process
903 * waiting on the page lock, because there are no references.
905 __clear_page_locked(page
);
910 * Is there need to periodically free_page_list? It would
911 * appear not as the counts should be low
913 list_add(&page
->lru
, &free_pages
);
917 if (PageSwapCache(page
))
918 try_to_free_swap(page
);
920 putback_lru_page(page
);
921 reset_reclaim_mode(sc
);
925 /* Not a candidate for swapping, so reclaim swap space. */
926 if (PageSwapCache(page
) && vm_swap_full())
927 try_to_free_swap(page
);
928 VM_BUG_ON(PageActive(page
));
934 reset_reclaim_mode(sc
);
936 list_add(&page
->lru
, &ret_pages
);
937 VM_BUG_ON(PageLRU(page
) || PageUnevictable(page
));
941 * Tag a zone as congested if all the dirty pages encountered were
942 * backed by a congested BDI. In this case, reclaimers should just
943 * back off and wait for congestion to clear because further reclaim
944 * will encounter the same problem
946 if (nr_dirty
&& nr_dirty
== nr_congested
&& scanning_global_lru(sc
))
947 zone_set_flag(zone
, ZONE_CONGESTED
);
949 free_page_list(&free_pages
);
951 list_splice(&ret_pages
, page_list
);
952 count_vm_events(PGACTIVATE
, pgactivate
);
957 * Attempt to remove the specified page from its LRU. Only take this page
958 * if it is of the appropriate PageActive status. Pages which are being
959 * freed elsewhere are also ignored.
961 * page: page to consider
962 * mode: one of the LRU isolation modes defined above
964 * returns 0 on success, -ve errno on failure.
966 int __isolate_lru_page(struct page
*page
, int mode
, int file
)
970 /* Only take pages on the LRU. */
975 * When checking the active state, we need to be sure we are
976 * dealing with comparible boolean values. Take the logical not
979 if (mode
!= ISOLATE_BOTH
&& (!PageActive(page
) != !mode
))
982 if (mode
!= ISOLATE_BOTH
&& page_is_file_cache(page
) != file
)
986 * When this function is being called for lumpy reclaim, we
987 * initially look into all LRU pages, active, inactive and
988 * unevictable; only give shrink_page_list evictable pages.
990 if (PageUnevictable(page
))
995 if (likely(get_page_unless_zero(page
))) {
997 * Be careful not to clear PageLRU until after we're
998 * sure the page is not being freed elsewhere -- the
999 * page release code relies on it.
1009 * zone->lru_lock is heavily contended. Some of the functions that
1010 * shrink the lists perform better by taking out a batch of pages
1011 * and working on them outside the LRU lock.
1013 * For pagecache intensive workloads, this function is the hottest
1014 * spot in the kernel (apart from copy_*_user functions).
1016 * Appropriate locks must be held before calling this function.
1018 * @nr_to_scan: The number of pages to look through on the list.
1019 * @src: The LRU list to pull pages off.
1020 * @dst: The temp list to put pages on to.
1021 * @scanned: The number of pages that were scanned.
1022 * @order: The caller's attempted allocation order
1023 * @mode: One of the LRU isolation modes
1024 * @file: True [1] if isolating file [!anon] pages
1026 * returns how many pages were moved onto *@dst.
1028 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1029 struct list_head
*src
, struct list_head
*dst
,
1030 unsigned long *scanned
, int order
, int mode
, int file
)
1032 unsigned long nr_taken
= 0;
1033 unsigned long nr_lumpy_taken
= 0;
1034 unsigned long nr_lumpy_dirty
= 0;
1035 unsigned long nr_lumpy_failed
= 0;
1038 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
1041 unsigned long end_pfn
;
1042 unsigned long page_pfn
;
1045 page
= lru_to_page(src
);
1046 prefetchw_prev_lru_page(page
, src
, flags
);
1048 VM_BUG_ON(!PageLRU(page
));
1050 switch (__isolate_lru_page(page
, mode
, file
)) {
1052 list_move(&page
->lru
, dst
);
1053 mem_cgroup_del_lru(page
);
1054 nr_taken
+= hpage_nr_pages(page
);
1058 /* else it is being freed elsewhere */
1059 list_move(&page
->lru
, src
);
1060 mem_cgroup_rotate_lru_list(page
, page_lru(page
));
1071 * Attempt to take all pages in the order aligned region
1072 * surrounding the tag page. Only take those pages of
1073 * the same active state as that tag page. We may safely
1074 * round the target page pfn down to the requested order
1075 * as the mem_map is guaranteed valid out to MAX_ORDER,
1076 * where that page is in a different zone we will detect
1077 * it from its zone id and abort this block scan.
1079 zone_id
= page_zone_id(page
);
1080 page_pfn
= page_to_pfn(page
);
1081 pfn
= page_pfn
& ~((1 << order
) - 1);
1082 end_pfn
= pfn
+ (1 << order
);
1083 for (; pfn
< end_pfn
; pfn
++) {
1084 struct page
*cursor_page
;
1086 /* The target page is in the block, ignore it. */
1087 if (unlikely(pfn
== page_pfn
))
1090 /* Avoid holes within the zone. */
1091 if (unlikely(!pfn_valid_within(pfn
)))
1094 cursor_page
= pfn_to_page(pfn
);
1096 /* Check that we have not crossed a zone boundary. */
1097 if (unlikely(page_zone_id(cursor_page
) != zone_id
))
1101 * If we don't have enough swap space, reclaiming of
1102 * anon page which don't already have a swap slot is
1105 if (nr_swap_pages
<= 0 && PageAnon(cursor_page
) &&
1106 !PageSwapCache(cursor_page
))
1109 if (__isolate_lru_page(cursor_page
, mode
, file
) == 0) {
1110 list_move(&cursor_page
->lru
, dst
);
1111 mem_cgroup_del_lru(cursor_page
);
1112 nr_taken
+= hpage_nr_pages(page
);
1114 if (PageDirty(cursor_page
))
1118 /* the page is freed already. */
1119 if (!page_count(cursor_page
))
1125 /* If we break out of the loop above, lumpy reclaim failed */
1132 trace_mm_vmscan_lru_isolate(order
,
1135 nr_lumpy_taken
, nr_lumpy_dirty
, nr_lumpy_failed
,
1140 static unsigned long isolate_pages_global(unsigned long nr
,
1141 struct list_head
*dst
,
1142 unsigned long *scanned
, int order
,
1143 int mode
, struct zone
*z
,
1144 int active
, int file
)
1151 return isolate_lru_pages(nr
, &z
->lru
[lru
].list
, dst
, scanned
, order
,
1156 * clear_active_flags() is a helper for shrink_active_list(), clearing
1157 * any active bits from the pages in the list.
1159 static unsigned long clear_active_flags(struct list_head
*page_list
,
1160 unsigned int *count
)
1166 list_for_each_entry(page
, page_list
, lru
) {
1167 int numpages
= hpage_nr_pages(page
);
1168 lru
= page_lru_base_type(page
);
1169 if (PageActive(page
)) {
1171 ClearPageActive(page
);
1172 nr_active
+= numpages
;
1175 count
[lru
] += numpages
;
1182 * isolate_lru_page - tries to isolate a page from its LRU list
1183 * @page: page to isolate from its LRU list
1185 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1186 * vmstat statistic corresponding to whatever LRU list the page was on.
1188 * Returns 0 if the page was removed from an LRU list.
1189 * Returns -EBUSY if the page was not on an LRU list.
1191 * The returned page will have PageLRU() cleared. If it was found on
1192 * the active list, it will have PageActive set. If it was found on
1193 * the unevictable list, it will have the PageUnevictable bit set. That flag
1194 * may need to be cleared by the caller before letting the page go.
1196 * The vmstat statistic corresponding to the list on which the page was
1197 * found will be decremented.
1200 * (1) Must be called with an elevated refcount on the page. This is a
1201 * fundamentnal difference from isolate_lru_pages (which is called
1202 * without a stable reference).
1203 * (2) the lru_lock must not be held.
1204 * (3) interrupts must be enabled.
1206 int isolate_lru_page(struct page
*page
)
1210 VM_BUG_ON(!page_count(page
));
1212 if (PageLRU(page
)) {
1213 struct zone
*zone
= page_zone(page
);
1215 spin_lock_irq(&zone
->lru_lock
);
1216 if (PageLRU(page
)) {
1217 int lru
= page_lru(page
);
1222 del_page_from_lru_list(zone
, page
, lru
);
1224 spin_unlock_irq(&zone
->lru_lock
);
1230 * Are there way too many processes in the direct reclaim path already?
1232 static int too_many_isolated(struct zone
*zone
, int file
,
1233 struct scan_control
*sc
)
1235 unsigned long inactive
, isolated
;
1237 if (current_is_kswapd())
1240 if (!scanning_global_lru(sc
))
1244 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1245 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1247 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1248 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1251 return isolated
> inactive
;
1255 * TODO: Try merging with migrations version of putback_lru_pages
1257 static noinline_for_stack
void
1258 putback_lru_pages(struct zone
*zone
, struct scan_control
*sc
,
1259 unsigned long nr_anon
, unsigned long nr_file
,
1260 struct list_head
*page_list
)
1263 struct pagevec pvec
;
1264 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1266 pagevec_init(&pvec
, 1);
1269 * Put back any unfreeable pages.
1271 spin_lock(&zone
->lru_lock
);
1272 while (!list_empty(page_list
)) {
1274 page
= lru_to_page(page_list
);
1275 VM_BUG_ON(PageLRU(page
));
1276 list_del(&page
->lru
);
1277 if (unlikely(!page_evictable(page
, NULL
))) {
1278 spin_unlock_irq(&zone
->lru_lock
);
1279 putback_lru_page(page
);
1280 spin_lock_irq(&zone
->lru_lock
);
1284 lru
= page_lru(page
);
1285 add_page_to_lru_list(zone
, page
, lru
);
1286 if (is_active_lru(lru
)) {
1287 int file
= is_file_lru(lru
);
1288 int numpages
= hpage_nr_pages(page
);
1289 reclaim_stat
->recent_rotated
[file
] += numpages
;
1291 if (!pagevec_add(&pvec
, page
)) {
1292 spin_unlock_irq(&zone
->lru_lock
);
1293 __pagevec_release(&pvec
);
1294 spin_lock_irq(&zone
->lru_lock
);
1297 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, -nr_anon
);
1298 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -nr_file
);
1300 spin_unlock_irq(&zone
->lru_lock
);
1301 pagevec_release(&pvec
);
1304 static noinline_for_stack
void update_isolated_counts(struct zone
*zone
,
1305 struct scan_control
*sc
,
1306 unsigned long *nr_anon
,
1307 unsigned long *nr_file
,
1308 struct list_head
*isolated_list
)
1310 unsigned long nr_active
;
1311 unsigned int count
[NR_LRU_LISTS
] = { 0, };
1312 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1314 nr_active
= clear_active_flags(isolated_list
, count
);
1315 __count_vm_events(PGDEACTIVATE
, nr_active
);
1317 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
1318 -count
[LRU_ACTIVE_FILE
]);
1319 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
1320 -count
[LRU_INACTIVE_FILE
]);
1321 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
1322 -count
[LRU_ACTIVE_ANON
]);
1323 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
1324 -count
[LRU_INACTIVE_ANON
]);
1326 *nr_anon
= count
[LRU_ACTIVE_ANON
] + count
[LRU_INACTIVE_ANON
];
1327 *nr_file
= count
[LRU_ACTIVE_FILE
] + count
[LRU_INACTIVE_FILE
];
1328 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, *nr_anon
);
1329 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, *nr_file
);
1331 reclaim_stat
->recent_scanned
[0] += *nr_anon
;
1332 reclaim_stat
->recent_scanned
[1] += *nr_file
;
1336 * Returns true if the caller should wait to clean dirty/writeback pages.
1338 * If we are direct reclaiming for contiguous pages and we do not reclaim
1339 * everything in the list, try again and wait for writeback IO to complete.
1340 * This will stall high-order allocations noticeably. Only do that when really
1341 * need to free the pages under high memory pressure.
1343 static inline bool should_reclaim_stall(unsigned long nr_taken
,
1344 unsigned long nr_freed
,
1346 struct scan_control
*sc
)
1348 int lumpy_stall_priority
;
1350 /* kswapd should not stall on sync IO */
1351 if (current_is_kswapd())
1354 /* Only stall on lumpy reclaim */
1355 if (sc
->reclaim_mode
& RECLAIM_MODE_SINGLE
)
1358 /* If we have relaimed everything on the isolated list, no stall */
1359 if (nr_freed
== nr_taken
)
1363 * For high-order allocations, there are two stall thresholds.
1364 * High-cost allocations stall immediately where as lower
1365 * order allocations such as stacks require the scanning
1366 * priority to be much higher before stalling.
1368 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
1369 lumpy_stall_priority
= DEF_PRIORITY
;
1371 lumpy_stall_priority
= DEF_PRIORITY
/ 3;
1373 return priority
<= lumpy_stall_priority
;
1377 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1378 * of reclaimed pages
1380 static noinline_for_stack
unsigned long
1381 shrink_inactive_list(unsigned long nr_to_scan
, struct zone
*zone
,
1382 struct scan_control
*sc
, int priority
, int file
)
1384 LIST_HEAD(page_list
);
1385 unsigned long nr_scanned
;
1386 unsigned long nr_reclaimed
= 0;
1387 unsigned long nr_taken
;
1388 unsigned long nr_anon
;
1389 unsigned long nr_file
;
1391 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1392 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1394 /* We are about to die and free our memory. Return now. */
1395 if (fatal_signal_pending(current
))
1396 return SWAP_CLUSTER_MAX
;
1399 set_reclaim_mode(priority
, sc
, false);
1401 spin_lock_irq(&zone
->lru_lock
);
1403 if (scanning_global_lru(sc
)) {
1404 nr_taken
= isolate_pages_global(nr_to_scan
,
1405 &page_list
, &nr_scanned
, sc
->order
,
1406 sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
?
1407 ISOLATE_BOTH
: ISOLATE_INACTIVE
,
1409 zone
->pages_scanned
+= nr_scanned
;
1410 if (current_is_kswapd())
1411 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
,
1414 __count_zone_vm_events(PGSCAN_DIRECT
, zone
,
1417 nr_taken
= mem_cgroup_isolate_pages(nr_to_scan
,
1418 &page_list
, &nr_scanned
, sc
->order
,
1419 sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
?
1420 ISOLATE_BOTH
: ISOLATE_INACTIVE
,
1421 zone
, sc
->mem_cgroup
,
1424 * mem_cgroup_isolate_pages() keeps track of
1425 * scanned pages on its own.
1429 if (nr_taken
== 0) {
1430 spin_unlock_irq(&zone
->lru_lock
);
1434 update_isolated_counts(zone
, sc
, &nr_anon
, &nr_file
, &page_list
);
1436 spin_unlock_irq(&zone
->lru_lock
);
1438 nr_reclaimed
= shrink_page_list(&page_list
, zone
, sc
);
1440 /* Check if we should syncronously wait for writeback */
1441 if (should_reclaim_stall(nr_taken
, nr_reclaimed
, priority
, sc
)) {
1442 set_reclaim_mode(priority
, sc
, true);
1443 nr_reclaimed
+= shrink_page_list(&page_list
, zone
, sc
);
1446 local_irq_disable();
1447 if (current_is_kswapd())
1448 __count_vm_events(KSWAPD_STEAL
, nr_reclaimed
);
1449 __count_zone_vm_events(PGSTEAL
, zone
, nr_reclaimed
);
1451 putback_lru_pages(zone
, sc
, nr_anon
, nr_file
, &page_list
);
1453 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1455 nr_scanned
, nr_reclaimed
,
1457 trace_shrink_flags(file
, sc
->reclaim_mode
));
1458 return nr_reclaimed
;
1462 * This moves pages from the active list to the inactive list.
1464 * We move them the other way if the page is referenced by one or more
1465 * processes, from rmap.
1467 * If the pages are mostly unmapped, the processing is fast and it is
1468 * appropriate to hold zone->lru_lock across the whole operation. But if
1469 * the pages are mapped, the processing is slow (page_referenced()) so we
1470 * should drop zone->lru_lock around each page. It's impossible to balance
1471 * this, so instead we remove the pages from the LRU while processing them.
1472 * It is safe to rely on PG_active against the non-LRU pages in here because
1473 * nobody will play with that bit on a non-LRU page.
1475 * The downside is that we have to touch page->_count against each page.
1476 * But we had to alter page->flags anyway.
1479 static void move_active_pages_to_lru(struct zone
*zone
,
1480 struct list_head
*list
,
1483 unsigned long pgmoved
= 0;
1484 struct pagevec pvec
;
1487 pagevec_init(&pvec
, 1);
1489 while (!list_empty(list
)) {
1490 page
= lru_to_page(list
);
1492 VM_BUG_ON(PageLRU(page
));
1495 list_move(&page
->lru
, &zone
->lru
[lru
].list
);
1496 mem_cgroup_add_lru_list(page
, lru
);
1497 pgmoved
+= hpage_nr_pages(page
);
1499 if (!pagevec_add(&pvec
, page
) || list_empty(list
)) {
1500 spin_unlock_irq(&zone
->lru_lock
);
1501 if (buffer_heads_over_limit
)
1502 pagevec_strip(&pvec
);
1503 __pagevec_release(&pvec
);
1504 spin_lock_irq(&zone
->lru_lock
);
1507 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1508 if (!is_active_lru(lru
))
1509 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1512 static void shrink_active_list(unsigned long nr_pages
, struct zone
*zone
,
1513 struct scan_control
*sc
, int priority
, int file
)
1515 unsigned long nr_taken
;
1516 unsigned long pgscanned
;
1517 unsigned long vm_flags
;
1518 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1519 LIST_HEAD(l_active
);
1520 LIST_HEAD(l_inactive
);
1522 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1523 unsigned long nr_rotated
= 0;
1526 spin_lock_irq(&zone
->lru_lock
);
1527 if (scanning_global_lru(sc
)) {
1528 nr_taken
= isolate_pages_global(nr_pages
, &l_hold
,
1529 &pgscanned
, sc
->order
,
1530 ISOLATE_ACTIVE
, zone
,
1532 zone
->pages_scanned
+= pgscanned
;
1534 nr_taken
= mem_cgroup_isolate_pages(nr_pages
, &l_hold
,
1535 &pgscanned
, sc
->order
,
1536 ISOLATE_ACTIVE
, zone
,
1537 sc
->mem_cgroup
, 1, file
);
1539 * mem_cgroup_isolate_pages() keeps track of
1540 * scanned pages on its own.
1544 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1546 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1548 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -nr_taken
);
1550 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -nr_taken
);
1551 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1552 spin_unlock_irq(&zone
->lru_lock
);
1554 while (!list_empty(&l_hold
)) {
1556 page
= lru_to_page(&l_hold
);
1557 list_del(&page
->lru
);
1559 if (unlikely(!page_evictable(page
, NULL
))) {
1560 putback_lru_page(page
);
1564 if (page_referenced(page
, 0, sc
->mem_cgroup
, &vm_flags
)) {
1565 nr_rotated
+= hpage_nr_pages(page
);
1567 * Identify referenced, file-backed active pages and
1568 * give them one more trip around the active list. So
1569 * that executable code get better chances to stay in
1570 * memory under moderate memory pressure. Anon pages
1571 * are not likely to be evicted by use-once streaming
1572 * IO, plus JVM can create lots of anon VM_EXEC pages,
1573 * so we ignore them here.
1575 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1576 list_add(&page
->lru
, &l_active
);
1581 ClearPageActive(page
); /* we are de-activating */
1582 list_add(&page
->lru
, &l_inactive
);
1586 * Move pages back to the lru list.
1588 spin_lock_irq(&zone
->lru_lock
);
1590 * Count referenced pages from currently used mappings as rotated,
1591 * even though only some of them are actually re-activated. This
1592 * helps balance scan pressure between file and anonymous pages in
1595 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1597 move_active_pages_to_lru(zone
, &l_active
,
1598 LRU_ACTIVE
+ file
* LRU_FILE
);
1599 move_active_pages_to_lru(zone
, &l_inactive
,
1600 LRU_BASE
+ file
* LRU_FILE
);
1601 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1602 spin_unlock_irq(&zone
->lru_lock
);
1606 static int inactive_anon_is_low_global(struct zone
*zone
)
1608 unsigned long active
, inactive
;
1610 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1611 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1613 if (inactive
* zone
->inactive_ratio
< active
)
1620 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1621 * @zone: zone to check
1622 * @sc: scan control of this context
1624 * Returns true if the zone does not have enough inactive anon pages,
1625 * meaning some active anon pages need to be deactivated.
1627 static int inactive_anon_is_low(struct zone
*zone
, struct scan_control
*sc
)
1632 * If we don't have swap space, anonymous page deactivation
1635 if (!total_swap_pages
)
1638 if (scanning_global_lru(sc
))
1639 low
= inactive_anon_is_low_global(zone
);
1641 low
= mem_cgroup_inactive_anon_is_low(sc
->mem_cgroup
);
1645 static inline int inactive_anon_is_low(struct zone
*zone
,
1646 struct scan_control
*sc
)
1652 static int inactive_file_is_low_global(struct zone
*zone
)
1654 unsigned long active
, inactive
;
1656 active
= zone_page_state(zone
, NR_ACTIVE_FILE
);
1657 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1659 return (active
> inactive
);
1663 * inactive_file_is_low - check if file pages need to be deactivated
1664 * @zone: zone to check
1665 * @sc: scan control of this context
1667 * When the system is doing streaming IO, memory pressure here
1668 * ensures that active file pages get deactivated, until more
1669 * than half of the file pages are on the inactive list.
1671 * Once we get to that situation, protect the system's working
1672 * set from being evicted by disabling active file page aging.
1674 * This uses a different ratio than the anonymous pages, because
1675 * the page cache uses a use-once replacement algorithm.
1677 static int inactive_file_is_low(struct zone
*zone
, struct scan_control
*sc
)
1681 if (scanning_global_lru(sc
))
1682 low
= inactive_file_is_low_global(zone
);
1684 low
= mem_cgroup_inactive_file_is_low(sc
->mem_cgroup
);
1688 static int inactive_list_is_low(struct zone
*zone
, struct scan_control
*sc
,
1692 return inactive_file_is_low(zone
, sc
);
1694 return inactive_anon_is_low(zone
, sc
);
1697 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1698 struct zone
*zone
, struct scan_control
*sc
, int priority
)
1700 int file
= is_file_lru(lru
);
1702 if (is_active_lru(lru
)) {
1703 if (inactive_list_is_low(zone
, sc
, file
))
1704 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1708 return shrink_inactive_list(nr_to_scan
, zone
, sc
, priority
, file
);
1712 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1713 * until we collected @swap_cluster_max pages to scan.
1715 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan
,
1716 unsigned long *nr_saved_scan
)
1720 *nr_saved_scan
+= nr_to_scan
;
1721 nr
= *nr_saved_scan
;
1723 if (nr
>= SWAP_CLUSTER_MAX
)
1732 * Determine how aggressively the anon and file LRU lists should be
1733 * scanned. The relative value of each set of LRU lists is determined
1734 * by looking at the fraction of the pages scanned we did rotate back
1735 * onto the active list instead of evict.
1737 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1739 static void get_scan_count(struct zone
*zone
, struct scan_control
*sc
,
1740 unsigned long *nr
, int priority
)
1742 unsigned long anon
, file
, free
;
1743 unsigned long anon_prio
, file_prio
;
1744 unsigned long ap
, fp
;
1745 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1746 u64 fraction
[2], denominator
;
1750 /* If we have no swap space, do not bother scanning anon pages. */
1751 if (!sc
->may_swap
|| (nr_swap_pages
<= 0)) {
1759 anon
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_ANON
) +
1760 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
);
1761 file
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_FILE
) +
1762 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
1764 if (scanning_global_lru(sc
)) {
1765 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1766 /* If we have very few page cache pages,
1767 force-scan anon pages. */
1768 if (unlikely(file
+ free
<= high_wmark_pages(zone
))) {
1777 * With swappiness at 100, anonymous and file have the same priority.
1778 * This scanning priority is essentially the inverse of IO cost.
1780 anon_prio
= sc
->swappiness
;
1781 file_prio
= 200 - sc
->swappiness
;
1784 * OK, so we have swap space and a fair amount of page cache
1785 * pages. We use the recently rotated / recently scanned
1786 * ratios to determine how valuable each cache is.
1788 * Because workloads change over time (and to avoid overflow)
1789 * we keep these statistics as a floating average, which ends
1790 * up weighing recent references more than old ones.
1792 * anon in [0], file in [1]
1794 spin_lock_irq(&zone
->lru_lock
);
1795 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1796 reclaim_stat
->recent_scanned
[0] /= 2;
1797 reclaim_stat
->recent_rotated
[0] /= 2;
1800 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1801 reclaim_stat
->recent_scanned
[1] /= 2;
1802 reclaim_stat
->recent_rotated
[1] /= 2;
1806 * The amount of pressure on anon vs file pages is inversely
1807 * proportional to the fraction of recently scanned pages on
1808 * each list that were recently referenced and in active use.
1810 ap
= (anon_prio
+ 1) * (reclaim_stat
->recent_scanned
[0] + 1);
1811 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1813 fp
= (file_prio
+ 1) * (reclaim_stat
->recent_scanned
[1] + 1);
1814 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1815 spin_unlock_irq(&zone
->lru_lock
);
1819 denominator
= ap
+ fp
+ 1;
1821 for_each_evictable_lru(l
) {
1822 int file
= is_file_lru(l
);
1825 scan
= zone_nr_lru_pages(zone
, sc
, l
);
1826 if (priority
|| noswap
) {
1828 scan
= div64_u64(scan
* fraction
[file
], denominator
);
1830 nr
[l
] = nr_scan_try_batch(scan
,
1831 &reclaim_stat
->nr_saved_scan
[l
]);
1836 * Reclaim/compaction depends on a number of pages being freed. To avoid
1837 * disruption to the system, a small number of order-0 pages continue to be
1838 * rotated and reclaimed in the normal fashion. However, by the time we get
1839 * back to the allocator and call try_to_compact_zone(), we ensure that
1840 * there are enough free pages for it to be likely successful
1842 static inline bool should_continue_reclaim(struct zone
*zone
,
1843 unsigned long nr_reclaimed
,
1844 unsigned long nr_scanned
,
1845 struct scan_control
*sc
)
1847 unsigned long pages_for_compaction
;
1848 unsigned long inactive_lru_pages
;
1850 /* If not in reclaim/compaction mode, stop */
1851 if (!(sc
->reclaim_mode
& RECLAIM_MODE_COMPACTION
))
1854 /* Consider stopping depending on scan and reclaim activity */
1855 if (sc
->gfp_mask
& __GFP_REPEAT
) {
1857 * For __GFP_REPEAT allocations, stop reclaiming if the
1858 * full LRU list has been scanned and we are still failing
1859 * to reclaim pages. This full LRU scan is potentially
1860 * expensive but a __GFP_REPEAT caller really wants to succeed
1862 if (!nr_reclaimed
&& !nr_scanned
)
1866 * For non-__GFP_REPEAT allocations which can presumably
1867 * fail without consequence, stop if we failed to reclaim
1868 * any pages from the last SWAP_CLUSTER_MAX number of
1869 * pages that were scanned. This will return to the
1870 * caller faster at the risk reclaim/compaction and
1871 * the resulting allocation attempt fails
1878 * If we have not reclaimed enough pages for compaction and the
1879 * inactive lists are large enough, continue reclaiming
1881 pages_for_compaction
= (2UL << sc
->order
);
1882 inactive_lru_pages
= zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
) +
1883 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
1884 if (sc
->nr_reclaimed
< pages_for_compaction
&&
1885 inactive_lru_pages
> pages_for_compaction
)
1888 /* If compaction would go ahead or the allocation would succeed, stop */
1889 switch (compaction_suitable(zone
, sc
->order
)) {
1890 case COMPACT_PARTIAL
:
1891 case COMPACT_CONTINUE
:
1899 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1901 static void shrink_zone(int priority
, struct zone
*zone
,
1902 struct scan_control
*sc
)
1904 unsigned long nr
[NR_LRU_LISTS
];
1905 unsigned long nr_to_scan
;
1907 unsigned long nr_reclaimed
, nr_scanned
;
1908 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
1912 nr_scanned
= sc
->nr_scanned
;
1913 get_scan_count(zone
, sc
, nr
, priority
);
1915 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
1916 nr
[LRU_INACTIVE_FILE
]) {
1917 for_each_evictable_lru(l
) {
1919 nr_to_scan
= min_t(unsigned long,
1920 nr
[l
], SWAP_CLUSTER_MAX
);
1921 nr
[l
] -= nr_to_scan
;
1923 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
1924 zone
, sc
, priority
);
1928 * On large memory systems, scan >> priority can become
1929 * really large. This is fine for the starting priority;
1930 * we want to put equal scanning pressure on each zone.
1931 * However, if the VM has a harder time of freeing pages,
1932 * with multiple processes reclaiming pages, the total
1933 * freeing target can get unreasonably large.
1935 if (nr_reclaimed
>= nr_to_reclaim
&& priority
< DEF_PRIORITY
)
1938 sc
->nr_reclaimed
+= nr_reclaimed
;
1941 * Even if we did not try to evict anon pages at all, we want to
1942 * rebalance the anon lru active/inactive ratio.
1944 if (inactive_anon_is_low(zone
, sc
))
1945 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
1947 /* reclaim/compaction might need reclaim to continue */
1948 if (should_continue_reclaim(zone
, nr_reclaimed
,
1949 sc
->nr_scanned
- nr_scanned
, sc
))
1952 throttle_vm_writeout(sc
->gfp_mask
);
1956 * This is the direct reclaim path, for page-allocating processes. We only
1957 * try to reclaim pages from zones which will satisfy the caller's allocation
1960 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1962 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1964 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1965 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1966 * zone defense algorithm.
1968 * If a zone is deemed to be full of pinned pages then just give it a light
1969 * scan then give up on it.
1971 static void shrink_zones(int priority
, struct zonelist
*zonelist
,
1972 struct scan_control
*sc
)
1977 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
1978 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
1979 if (!populated_zone(zone
))
1982 * Take care memory controller reclaiming has small influence
1985 if (scanning_global_lru(sc
)) {
1986 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1988 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
1989 continue; /* Let kswapd poll it */
1992 shrink_zone(priority
, zone
, sc
);
1996 static bool zone_reclaimable(struct zone
*zone
)
1998 return zone
->pages_scanned
< zone_reclaimable_pages(zone
) * 6;
2001 /* All zones in zonelist are unreclaimable? */
2002 static bool all_unreclaimable(struct zonelist
*zonelist
,
2003 struct scan_control
*sc
)
2008 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2009 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2010 if (!populated_zone(zone
))
2012 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2014 if (!zone
->all_unreclaimable
)
2022 * This is the main entry point to direct page reclaim.
2024 * If a full scan of the inactive list fails to free enough memory then we
2025 * are "out of memory" and something needs to be killed.
2027 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2028 * high - the zone may be full of dirty or under-writeback pages, which this
2029 * caller can't do much about. We kick the writeback threads and take explicit
2030 * naps in the hope that some of these pages can be written. But if the
2031 * allocating task holds filesystem locks which prevent writeout this might not
2032 * work, and the allocation attempt will fail.
2034 * returns: 0, if no pages reclaimed
2035 * else, the number of pages reclaimed
2037 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2038 struct scan_control
*sc
)
2041 unsigned long total_scanned
= 0;
2042 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2045 unsigned long writeback_threshold
;
2048 delayacct_freepages_start();
2050 if (scanning_global_lru(sc
))
2051 count_vm_event(ALLOCSTALL
);
2053 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2056 disable_swap_token();
2057 shrink_zones(priority
, zonelist
, sc
);
2059 * Don't shrink slabs when reclaiming memory from
2060 * over limit cgroups
2062 if (scanning_global_lru(sc
)) {
2063 unsigned long lru_pages
= 0;
2064 for_each_zone_zonelist(zone
, z
, zonelist
,
2065 gfp_zone(sc
->gfp_mask
)) {
2066 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2069 lru_pages
+= zone_reclaimable_pages(zone
);
2072 shrink_slab(sc
->nr_scanned
, sc
->gfp_mask
, lru_pages
);
2073 if (reclaim_state
) {
2074 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2075 reclaim_state
->reclaimed_slab
= 0;
2078 total_scanned
+= sc
->nr_scanned
;
2079 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2083 * Try to write back as many pages as we just scanned. This
2084 * tends to cause slow streaming writers to write data to the
2085 * disk smoothly, at the dirtying rate, which is nice. But
2086 * that's undesirable in laptop mode, where we *want* lumpy
2087 * writeout. So in laptop mode, write out the whole world.
2089 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2090 if (total_scanned
> writeback_threshold
) {
2091 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
);
2092 sc
->may_writepage
= 1;
2095 /* Take a nap, wait for some writeback to complete */
2096 if (!sc
->hibernation_mode
&& sc
->nr_scanned
&&
2097 priority
< DEF_PRIORITY
- 2) {
2098 struct zone
*preferred_zone
;
2100 first_zones_zonelist(zonelist
, gfp_zone(sc
->gfp_mask
),
2101 &cpuset_current_mems_allowed
,
2103 wait_iff_congested(preferred_zone
, BLK_RW_ASYNC
, HZ
/10);
2108 delayacct_freepages_end();
2111 if (sc
->nr_reclaimed
)
2112 return sc
->nr_reclaimed
;
2115 * As hibernation is going on, kswapd is freezed so that it can't mark
2116 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2119 if (oom_killer_disabled
)
2122 /* top priority shrink_zones still had more to do? don't OOM, then */
2123 if (scanning_global_lru(sc
) && !all_unreclaimable(zonelist
, sc
))
2129 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2130 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2132 unsigned long nr_reclaimed
;
2133 struct scan_control sc
= {
2134 .gfp_mask
= gfp_mask
,
2135 .may_writepage
= !laptop_mode
,
2136 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2139 .swappiness
= vm_swappiness
,
2142 .nodemask
= nodemask
,
2145 trace_mm_vmscan_direct_reclaim_begin(order
,
2149 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2151 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2153 return nr_reclaimed
;
2156 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2158 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*mem
,
2159 gfp_t gfp_mask
, bool noswap
,
2160 unsigned int swappiness
,
2163 struct scan_control sc
= {
2164 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2165 .may_writepage
= !laptop_mode
,
2167 .may_swap
= !noswap
,
2168 .swappiness
= swappiness
,
2172 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2173 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2175 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2180 * NOTE: Although we can get the priority field, using it
2181 * here is not a good idea, since it limits the pages we can scan.
2182 * if we don't reclaim here, the shrink_zone from balance_pgdat
2183 * will pick up pages from other mem cgroup's as well. We hack
2184 * the priority and make it zero.
2186 shrink_zone(0, zone
, &sc
);
2188 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2190 return sc
.nr_reclaimed
;
2193 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*mem_cont
,
2196 unsigned int swappiness
)
2198 struct zonelist
*zonelist
;
2199 unsigned long nr_reclaimed
;
2200 struct scan_control sc
= {
2201 .may_writepage
= !laptop_mode
,
2203 .may_swap
= !noswap
,
2204 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2205 .swappiness
= swappiness
,
2207 .mem_cgroup
= mem_cont
,
2208 .nodemask
= NULL
, /* we don't care the placement */
2211 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2212 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2213 zonelist
= NODE_DATA(numa_node_id())->node_zonelists
;
2215 trace_mm_vmscan_memcg_reclaim_begin(0,
2219 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2221 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2223 return nr_reclaimed
;
2228 * pgdat_balanced is used when checking if a node is balanced for high-order
2229 * allocations. Only zones that meet watermarks and are in a zone allowed
2230 * by the callers classzone_idx are added to balanced_pages. The total of
2231 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2232 * for the node to be considered balanced. Forcing all zones to be balanced
2233 * for high orders can cause excessive reclaim when there are imbalanced zones.
2234 * The choice of 25% is due to
2235 * o a 16M DMA zone that is balanced will not balance a zone on any
2236 * reasonable sized machine
2237 * o On all other machines, the top zone must be at least a reasonable
2238 * percentage of the middle zones. For example, on 32-bit x86, highmem
2239 * would need to be at least 256M for it to be balance a whole node.
2240 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2241 * to balance a node on its own. These seemed like reasonable ratios.
2243 static bool pgdat_balanced(pg_data_t
*pgdat
, unsigned long balanced_pages
,
2246 unsigned long present_pages
= 0;
2249 for (i
= 0; i
<= classzone_idx
; i
++)
2250 present_pages
+= pgdat
->node_zones
[i
].present_pages
;
2252 return balanced_pages
> (present_pages
>> 2);
2255 /* is kswapd sleeping prematurely? */
2256 static bool sleeping_prematurely(pg_data_t
*pgdat
, int order
, long remaining
,
2260 unsigned long balanced
= 0;
2261 bool all_zones_ok
= true;
2263 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2267 /* Check the watermark levels */
2268 for (i
= 0; i
< pgdat
->nr_zones
; i
++) {
2269 struct zone
*zone
= pgdat
->node_zones
+ i
;
2271 if (!populated_zone(zone
))
2275 * balance_pgdat() skips over all_unreclaimable after
2276 * DEF_PRIORITY. Effectively, it considers them balanced so
2277 * they must be considered balanced here as well if kswapd
2280 if (zone
->all_unreclaimable
) {
2281 balanced
+= zone
->present_pages
;
2285 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
),
2287 all_zones_ok
= false;
2289 balanced
+= zone
->present_pages
;
2293 * For high-order requests, the balanced zones must contain at least
2294 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2298 return !pgdat_balanced(pgdat
, balanced
, classzone_idx
);
2300 return !all_zones_ok
;
2304 * For kswapd, balance_pgdat() will work across all this node's zones until
2305 * they are all at high_wmark_pages(zone).
2307 * Returns the final order kswapd was reclaiming at
2309 * There is special handling here for zones which are full of pinned pages.
2310 * This can happen if the pages are all mlocked, or if they are all used by
2311 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2312 * What we do is to detect the case where all pages in the zone have been
2313 * scanned twice and there has been zero successful reclaim. Mark the zone as
2314 * dead and from now on, only perform a short scan. Basically we're polling
2315 * the zone for when the problem goes away.
2317 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2318 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2319 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2320 * lower zones regardless of the number of free pages in the lower zones. This
2321 * interoperates with the page allocator fallback scheme to ensure that aging
2322 * of pages is balanced across the zones.
2324 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
2328 unsigned long balanced
;
2331 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
2332 unsigned long total_scanned
;
2333 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2334 struct scan_control sc
= {
2335 .gfp_mask
= GFP_KERNEL
,
2339 * kswapd doesn't want to be bailed out while reclaim. because
2340 * we want to put equal scanning pressure on each zone.
2342 .nr_to_reclaim
= ULONG_MAX
,
2343 .swappiness
= vm_swappiness
,
2349 sc
.nr_reclaimed
= 0;
2350 sc
.may_writepage
= !laptop_mode
;
2351 count_vm_event(PAGEOUTRUN
);
2353 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2354 unsigned long lru_pages
= 0;
2355 int has_under_min_watermark_zone
= 0;
2357 /* The swap token gets in the way of swapout... */
2359 disable_swap_token();
2365 * Scan in the highmem->dma direction for the highest
2366 * zone which needs scanning
2368 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
2369 struct zone
*zone
= pgdat
->node_zones
+ i
;
2371 if (!populated_zone(zone
))
2374 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2378 * Do some background aging of the anon list, to give
2379 * pages a chance to be referenced before reclaiming.
2381 if (inactive_anon_is_low(zone
, &sc
))
2382 shrink_active_list(SWAP_CLUSTER_MAX
, zone
,
2385 if (!zone_watermark_ok_safe(zone
, order
,
2386 high_wmark_pages(zone
), 0, 0)) {
2395 for (i
= 0; i
<= end_zone
; i
++) {
2396 struct zone
*zone
= pgdat
->node_zones
+ i
;
2398 lru_pages
+= zone_reclaimable_pages(zone
);
2402 * Now scan the zone in the dma->highmem direction, stopping
2403 * at the last zone which needs scanning.
2405 * We do this because the page allocator works in the opposite
2406 * direction. This prevents the page allocator from allocating
2407 * pages behind kswapd's direction of progress, which would
2408 * cause too much scanning of the lower zones.
2410 for (i
= 0; i
<= end_zone
; i
++) {
2411 struct zone
*zone
= pgdat
->node_zones
+ i
;
2413 unsigned long balance_gap
;
2415 if (!populated_zone(zone
))
2418 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2424 * Call soft limit reclaim before calling shrink_zone.
2425 * For now we ignore the return value
2427 mem_cgroup_soft_limit_reclaim(zone
, order
, sc
.gfp_mask
);
2430 * We put equal pressure on every zone, unless
2431 * one zone has way too many pages free
2432 * already. The "too many pages" is defined
2433 * as the high wmark plus a "gap" where the
2434 * gap is either the low watermark or 1%
2435 * of the zone, whichever is smaller.
2437 balance_gap
= min(low_wmark_pages(zone
),
2438 (zone
->present_pages
+
2439 KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2440 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2441 if (!zone_watermark_ok_safe(zone
, order
,
2442 high_wmark_pages(zone
) + balance_gap
,
2444 shrink_zone(priority
, zone
, &sc
);
2445 reclaim_state
->reclaimed_slab
= 0;
2446 nr_slab
= shrink_slab(sc
.nr_scanned
, GFP_KERNEL
,
2448 sc
.nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2449 total_scanned
+= sc
.nr_scanned
;
2451 if (zone
->all_unreclaimable
)
2454 !zone_reclaimable(zone
))
2455 zone
->all_unreclaimable
= 1;
2457 * If we've done a decent amount of scanning and
2458 * the reclaim ratio is low, start doing writepage
2459 * even in laptop mode
2461 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
2462 total_scanned
> sc
.nr_reclaimed
+ sc
.nr_reclaimed
/ 2)
2463 sc
.may_writepage
= 1;
2465 if (!zone_watermark_ok_safe(zone
, order
,
2466 high_wmark_pages(zone
), end_zone
, 0)) {
2469 * We are still under min water mark. This
2470 * means that we have a GFP_ATOMIC allocation
2471 * failure risk. Hurry up!
2473 if (!zone_watermark_ok_safe(zone
, order
,
2474 min_wmark_pages(zone
), end_zone
, 0))
2475 has_under_min_watermark_zone
= 1;
2478 * If a zone reaches its high watermark,
2479 * consider it to be no longer congested. It's
2480 * possible there are dirty pages backed by
2481 * congested BDIs but as pressure is relieved,
2482 * spectulatively avoid congestion waits
2484 zone_clear_flag(zone
, ZONE_CONGESTED
);
2485 if (i
<= *classzone_idx
)
2486 balanced
+= zone
->present_pages
;
2490 if (all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))
2491 break; /* kswapd: all done */
2493 * OK, kswapd is getting into trouble. Take a nap, then take
2494 * another pass across the zones.
2496 if (total_scanned
&& (priority
< DEF_PRIORITY
- 2)) {
2497 if (has_under_min_watermark_zone
)
2498 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT
);
2500 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
2504 * We do this so kswapd doesn't build up large priorities for
2505 * example when it is freeing in parallel with allocators. It
2506 * matches the direct reclaim path behaviour in terms of impact
2507 * on zone->*_priority.
2509 if (sc
.nr_reclaimed
>= SWAP_CLUSTER_MAX
)
2515 * order-0: All zones must meet high watermark for a balanced node
2516 * high-order: Balanced zones must make up at least 25% of the node
2517 * for the node to be balanced
2519 if (!(all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))) {
2525 * Fragmentation may mean that the system cannot be
2526 * rebalanced for high-order allocations in all zones.
2527 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2528 * it means the zones have been fully scanned and are still
2529 * not balanced. For high-order allocations, there is
2530 * little point trying all over again as kswapd may
2533 * Instead, recheck all watermarks at order-0 as they
2534 * are the most important. If watermarks are ok, kswapd will go
2535 * back to sleep. High-order users can still perform direct
2536 * reclaim if they wish.
2538 if (sc
.nr_reclaimed
< SWAP_CLUSTER_MAX
)
2539 order
= sc
.order
= 0;
2545 * If kswapd was reclaiming at a higher order, it has the option of
2546 * sleeping without all zones being balanced. Before it does, it must
2547 * ensure that the watermarks for order-0 on *all* zones are met and
2548 * that the congestion flags are cleared. The congestion flag must
2549 * be cleared as kswapd is the only mechanism that clears the flag
2550 * and it is potentially going to sleep here.
2553 for (i
= 0; i
<= end_zone
; i
++) {
2554 struct zone
*zone
= pgdat
->node_zones
+ i
;
2556 if (!populated_zone(zone
))
2559 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2562 /* Confirm the zone is balanced for order-0 */
2563 if (!zone_watermark_ok(zone
, 0,
2564 high_wmark_pages(zone
), 0, 0)) {
2565 order
= sc
.order
= 0;
2569 /* If balanced, clear the congested flag */
2570 zone_clear_flag(zone
, ZONE_CONGESTED
);
2575 * Return the order we were reclaiming at so sleeping_prematurely()
2576 * makes a decision on the order we were last reclaiming at. However,
2577 * if another caller entered the allocator slow path while kswapd
2578 * was awake, order will remain at the higher level
2580 *classzone_idx
= end_zone
;
2584 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2589 if (freezing(current
) || kthread_should_stop())
2592 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2594 /* Try to sleep for a short interval */
2595 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2596 remaining
= schedule_timeout(HZ
/10);
2597 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2598 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2602 * After a short sleep, check if it was a premature sleep. If not, then
2603 * go fully to sleep until explicitly woken up.
2605 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2606 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
2609 * vmstat counters are not perfectly accurate and the estimated
2610 * value for counters such as NR_FREE_PAGES can deviate from the
2611 * true value by nr_online_cpus * threshold. To avoid the zone
2612 * watermarks being breached while under pressure, we reduce the
2613 * per-cpu vmstat threshold while kswapd is awake and restore
2614 * them before going back to sleep.
2616 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
2618 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
2621 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
2623 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
2625 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2629 * The background pageout daemon, started as a kernel thread
2630 * from the init process.
2632 * This basically trickles out pages so that we have _some_
2633 * free memory available even if there is no other activity
2634 * that frees anything up. This is needed for things like routing
2635 * etc, where we otherwise might have all activity going on in
2636 * asynchronous contexts that cannot page things out.
2638 * If there are applications that are active memory-allocators
2639 * (most normal use), this basically shouldn't matter.
2641 static int kswapd(void *p
)
2643 unsigned long order
;
2645 pg_data_t
*pgdat
= (pg_data_t
*)p
;
2646 struct task_struct
*tsk
= current
;
2648 struct reclaim_state reclaim_state
= {
2649 .reclaimed_slab
= 0,
2651 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
2653 lockdep_set_current_reclaim_state(GFP_KERNEL
);
2655 if (!cpumask_empty(cpumask
))
2656 set_cpus_allowed_ptr(tsk
, cpumask
);
2657 current
->reclaim_state
= &reclaim_state
;
2660 * Tell the memory management that we're a "memory allocator",
2661 * and that if we need more memory we should get access to it
2662 * regardless (see "__alloc_pages()"). "kswapd" should
2663 * never get caught in the normal page freeing logic.
2665 * (Kswapd normally doesn't need memory anyway, but sometimes
2666 * you need a small amount of memory in order to be able to
2667 * page out something else, and this flag essentially protects
2668 * us from recursively trying to free more memory as we're
2669 * trying to free the first piece of memory in the first place).
2671 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
2675 classzone_idx
= MAX_NR_ZONES
- 1;
2677 unsigned long new_order
;
2678 int new_classzone_idx
;
2681 new_order
= pgdat
->kswapd_max_order
;
2682 new_classzone_idx
= pgdat
->classzone_idx
;
2683 pgdat
->kswapd_max_order
= 0;
2684 pgdat
->classzone_idx
= MAX_NR_ZONES
- 1;
2685 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
2687 * Don't sleep if someone wants a larger 'order'
2688 * allocation or has tigher zone constraints
2691 classzone_idx
= new_classzone_idx
;
2693 kswapd_try_to_sleep(pgdat
, order
, classzone_idx
);
2694 order
= pgdat
->kswapd_max_order
;
2695 classzone_idx
= pgdat
->classzone_idx
;
2696 pgdat
->kswapd_max_order
= 0;
2697 pgdat
->classzone_idx
= MAX_NR_ZONES
- 1;
2700 ret
= try_to_freeze();
2701 if (kthread_should_stop())
2705 * We can speed up thawing tasks if we don't call balance_pgdat
2706 * after returning from the refrigerator
2709 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
2710 order
= balance_pgdat(pgdat
, order
, &classzone_idx
);
2717 * A zone is low on free memory, so wake its kswapd task to service it.
2719 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
2723 if (!populated_zone(zone
))
2726 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2728 pgdat
= zone
->zone_pgdat
;
2729 if (pgdat
->kswapd_max_order
< order
) {
2730 pgdat
->kswapd_max_order
= order
;
2731 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
2733 if (!waitqueue_active(&pgdat
->kswapd_wait
))
2735 if (zone_watermark_ok_safe(zone
, order
, low_wmark_pages(zone
), 0, 0))
2738 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
2739 wake_up_interruptible(&pgdat
->kswapd_wait
);
2743 * The reclaimable count would be mostly accurate.
2744 * The less reclaimable pages may be
2745 * - mlocked pages, which will be moved to unevictable list when encountered
2746 * - mapped pages, which may require several travels to be reclaimed
2747 * - dirty pages, which is not "instantly" reclaimable
2749 unsigned long global_reclaimable_pages(void)
2753 nr
= global_page_state(NR_ACTIVE_FILE
) +
2754 global_page_state(NR_INACTIVE_FILE
);
2756 if (nr_swap_pages
> 0)
2757 nr
+= global_page_state(NR_ACTIVE_ANON
) +
2758 global_page_state(NR_INACTIVE_ANON
);
2763 unsigned long zone_reclaimable_pages(struct zone
*zone
)
2767 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
2768 zone_page_state(zone
, NR_INACTIVE_FILE
);
2770 if (nr_swap_pages
> 0)
2771 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
2772 zone_page_state(zone
, NR_INACTIVE_ANON
);
2777 #ifdef CONFIG_HIBERNATION
2779 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2782 * Rather than trying to age LRUs the aim is to preserve the overall
2783 * LRU order by reclaiming preferentially
2784 * inactive > active > active referenced > active mapped
2786 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
2788 struct reclaim_state reclaim_state
;
2789 struct scan_control sc
= {
2790 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
2794 .nr_to_reclaim
= nr_to_reclaim
,
2795 .hibernation_mode
= 1,
2796 .swappiness
= vm_swappiness
,
2799 struct zonelist
* zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
2800 struct task_struct
*p
= current
;
2801 unsigned long nr_reclaimed
;
2803 p
->flags
|= PF_MEMALLOC
;
2804 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
2805 reclaim_state
.reclaimed_slab
= 0;
2806 p
->reclaim_state
= &reclaim_state
;
2808 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2810 p
->reclaim_state
= NULL
;
2811 lockdep_clear_current_reclaim_state();
2812 p
->flags
&= ~PF_MEMALLOC
;
2814 return nr_reclaimed
;
2816 #endif /* CONFIG_HIBERNATION */
2818 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2819 not required for correctness. So if the last cpu in a node goes
2820 away, we get changed to run anywhere: as the first one comes back,
2821 restore their cpu bindings. */
2822 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
2823 unsigned long action
, void *hcpu
)
2827 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
2828 for_each_node_state(nid
, N_HIGH_MEMORY
) {
2829 pg_data_t
*pgdat
= NODE_DATA(nid
);
2830 const struct cpumask
*mask
;
2832 mask
= cpumask_of_node(pgdat
->node_id
);
2834 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
2835 /* One of our CPUs online: restore mask */
2836 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
2843 * This kswapd start function will be called by init and node-hot-add.
2844 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2846 int kswapd_run(int nid
)
2848 pg_data_t
*pgdat
= NODE_DATA(nid
);
2854 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
2855 if (IS_ERR(pgdat
->kswapd
)) {
2856 /* failure at boot is fatal */
2857 BUG_ON(system_state
== SYSTEM_BOOTING
);
2858 printk("Failed to start kswapd on node %d\n",nid
);
2865 * Called by memory hotplug when all memory in a node is offlined.
2867 void kswapd_stop(int nid
)
2869 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
2872 kthread_stop(kswapd
);
2875 static int __init
kswapd_init(void)
2880 for_each_node_state(nid
, N_HIGH_MEMORY
)
2882 hotcpu_notifier(cpu_callback
, 0);
2886 module_init(kswapd_init
)
2892 * If non-zero call zone_reclaim when the number of free pages falls below
2895 int zone_reclaim_mode __read_mostly
;
2897 #define RECLAIM_OFF 0
2898 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2899 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2900 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2903 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2904 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2907 #define ZONE_RECLAIM_PRIORITY 4
2910 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2913 int sysctl_min_unmapped_ratio
= 1;
2916 * If the number of slab pages in a zone grows beyond this percentage then
2917 * slab reclaim needs to occur.
2919 int sysctl_min_slab_ratio
= 5;
2921 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
2923 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
2924 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
2925 zone_page_state(zone
, NR_ACTIVE_FILE
);
2928 * It's possible for there to be more file mapped pages than
2929 * accounted for by the pages on the file LRU lists because
2930 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2932 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
2935 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2936 static long zone_pagecache_reclaimable(struct zone
*zone
)
2938 long nr_pagecache_reclaimable
;
2942 * If RECLAIM_SWAP is set, then all file pages are considered
2943 * potentially reclaimable. Otherwise, we have to worry about
2944 * pages like swapcache and zone_unmapped_file_pages() provides
2947 if (zone_reclaim_mode
& RECLAIM_SWAP
)
2948 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
2950 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
2952 /* If we can't clean pages, remove dirty pages from consideration */
2953 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
2954 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
2956 /* Watch for any possible underflows due to delta */
2957 if (unlikely(delta
> nr_pagecache_reclaimable
))
2958 delta
= nr_pagecache_reclaimable
;
2960 return nr_pagecache_reclaimable
- delta
;
2964 * Try to free up some pages from this zone through reclaim.
2966 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2968 /* Minimum pages needed in order to stay on node */
2969 const unsigned long nr_pages
= 1 << order
;
2970 struct task_struct
*p
= current
;
2971 struct reclaim_state reclaim_state
;
2973 struct scan_control sc
= {
2974 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
2975 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
2977 .nr_to_reclaim
= max_t(unsigned long, nr_pages
,
2979 .gfp_mask
= gfp_mask
,
2980 .swappiness
= vm_swappiness
,
2983 unsigned long nr_slab_pages0
, nr_slab_pages1
;
2987 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2988 * and we also need to be able to write out pages for RECLAIM_WRITE
2991 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
2992 lockdep_set_current_reclaim_state(gfp_mask
);
2993 reclaim_state
.reclaimed_slab
= 0;
2994 p
->reclaim_state
= &reclaim_state
;
2996 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
2998 * Free memory by calling shrink zone with increasing
2999 * priorities until we have enough memory freed.
3001 priority
= ZONE_RECLAIM_PRIORITY
;
3003 shrink_zone(priority
, zone
, &sc
);
3005 } while (priority
>= 0 && sc
.nr_reclaimed
< nr_pages
);
3008 nr_slab_pages0
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3009 if (nr_slab_pages0
> zone
->min_slab_pages
) {
3011 * shrink_slab() does not currently allow us to determine how
3012 * many pages were freed in this zone. So we take the current
3013 * number of slab pages and shake the slab until it is reduced
3014 * by the same nr_pages that we used for reclaiming unmapped
3017 * Note that shrink_slab will free memory on all zones and may
3021 unsigned long lru_pages
= zone_reclaimable_pages(zone
);
3023 /* No reclaimable slab or very low memory pressure */
3024 if (!shrink_slab(sc
.nr_scanned
, gfp_mask
, lru_pages
))
3027 /* Freed enough memory */
3028 nr_slab_pages1
= zone_page_state(zone
,
3029 NR_SLAB_RECLAIMABLE
);
3030 if (nr_slab_pages1
+ nr_pages
<= nr_slab_pages0
)
3035 * Update nr_reclaimed by the number of slab pages we
3036 * reclaimed from this zone.
3038 nr_slab_pages1
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3039 if (nr_slab_pages1
< nr_slab_pages0
)
3040 sc
.nr_reclaimed
+= nr_slab_pages0
- nr_slab_pages1
;
3043 p
->reclaim_state
= NULL
;
3044 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3045 lockdep_clear_current_reclaim_state();
3046 return sc
.nr_reclaimed
>= nr_pages
;
3049 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3055 * Zone reclaim reclaims unmapped file backed pages and
3056 * slab pages if we are over the defined limits.
3058 * A small portion of unmapped file backed pages is needed for
3059 * file I/O otherwise pages read by file I/O will be immediately
3060 * thrown out if the zone is overallocated. So we do not reclaim
3061 * if less than a specified percentage of the zone is used by
3062 * unmapped file backed pages.
3064 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3065 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3066 return ZONE_RECLAIM_FULL
;
3068 if (zone
->all_unreclaimable
)
3069 return ZONE_RECLAIM_FULL
;
3072 * Do not scan if the allocation should not be delayed.
3074 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3075 return ZONE_RECLAIM_NOSCAN
;
3078 * Only run zone reclaim on the local zone or on zones that do not
3079 * have associated processors. This will favor the local processor
3080 * over remote processors and spread off node memory allocations
3081 * as wide as possible.
3083 node_id
= zone_to_nid(zone
);
3084 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3085 return ZONE_RECLAIM_NOSCAN
;
3087 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
3088 return ZONE_RECLAIM_NOSCAN
;
3090 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3091 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
3094 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3101 * page_evictable - test whether a page is evictable
3102 * @page: the page to test
3103 * @vma: the VMA in which the page is or will be mapped, may be NULL
3105 * Test whether page is evictable--i.e., should be placed on active/inactive
3106 * lists vs unevictable list. The vma argument is !NULL when called from the
3107 * fault path to determine how to instantate a new page.
3109 * Reasons page might not be evictable:
3110 * (1) page's mapping marked unevictable
3111 * (2) page is part of an mlocked VMA
3114 int page_evictable(struct page
*page
, struct vm_area_struct
*vma
)
3117 if (mapping_unevictable(page_mapping(page
)))
3120 if (PageMlocked(page
) || (vma
&& is_mlocked_vma(vma
, page
)))
3127 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3128 * @page: page to check evictability and move to appropriate lru list
3129 * @zone: zone page is in
3131 * Checks a page for evictability and moves the page to the appropriate
3134 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3135 * have PageUnevictable set.
3137 static void check_move_unevictable_page(struct page
*page
, struct zone
*zone
)
3139 VM_BUG_ON(PageActive(page
));
3142 ClearPageUnevictable(page
);
3143 if (page_evictable(page
, NULL
)) {
3144 enum lru_list l
= page_lru_base_type(page
);
3146 __dec_zone_state(zone
, NR_UNEVICTABLE
);
3147 list_move(&page
->lru
, &zone
->lru
[l
].list
);
3148 mem_cgroup_move_lists(page
, LRU_UNEVICTABLE
, l
);
3149 __inc_zone_state(zone
, NR_INACTIVE_ANON
+ l
);
3150 __count_vm_event(UNEVICTABLE_PGRESCUED
);
3153 * rotate unevictable list
3155 SetPageUnevictable(page
);
3156 list_move(&page
->lru
, &zone
->lru
[LRU_UNEVICTABLE
].list
);
3157 mem_cgroup_rotate_lru_list(page
, LRU_UNEVICTABLE
);
3158 if (page_evictable(page
, NULL
))
3164 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3165 * @mapping: struct address_space to scan for evictable pages
3167 * Scan all pages in mapping. Check unevictable pages for
3168 * evictability and move them to the appropriate zone lru list.
3170 void scan_mapping_unevictable_pages(struct address_space
*mapping
)
3173 pgoff_t end
= (i_size_read(mapping
->host
) + PAGE_CACHE_SIZE
- 1) >>
3176 struct pagevec pvec
;
3178 if (mapping
->nrpages
== 0)
3181 pagevec_init(&pvec
, 0);
3182 while (next
< end
&&
3183 pagevec_lookup(&pvec
, mapping
, next
, PAGEVEC_SIZE
)) {
3189 for (i
= 0; i
< pagevec_count(&pvec
); i
++) {
3190 struct page
*page
= pvec
.pages
[i
];
3191 pgoff_t page_index
= page
->index
;
3192 struct zone
*pagezone
= page_zone(page
);
3195 if (page_index
> next
)
3199 if (pagezone
!= zone
) {
3201 spin_unlock_irq(&zone
->lru_lock
);
3203 spin_lock_irq(&zone
->lru_lock
);
3206 if (PageLRU(page
) && PageUnevictable(page
))
3207 check_move_unevictable_page(page
, zone
);
3210 spin_unlock_irq(&zone
->lru_lock
);
3211 pagevec_release(&pvec
);
3213 count_vm_events(UNEVICTABLE_PGSCANNED
, pg_scanned
);
3219 * scan_zone_unevictable_pages - check unevictable list for evictable pages
3220 * @zone - zone of which to scan the unevictable list
3222 * Scan @zone's unevictable LRU lists to check for pages that have become
3223 * evictable. Move those that have to @zone's inactive list where they
3224 * become candidates for reclaim, unless shrink_inactive_zone() decides
3225 * to reactivate them. Pages that are still unevictable are rotated
3226 * back onto @zone's unevictable list.
3228 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
3229 static void scan_zone_unevictable_pages(struct zone
*zone
)
3231 struct list_head
*l_unevictable
= &zone
->lru
[LRU_UNEVICTABLE
].list
;
3233 unsigned long nr_to_scan
= zone_page_state(zone
, NR_UNEVICTABLE
);
3235 while (nr_to_scan
> 0) {
3236 unsigned long batch_size
= min(nr_to_scan
,
3237 SCAN_UNEVICTABLE_BATCH_SIZE
);
3239 spin_lock_irq(&zone
->lru_lock
);
3240 for (scan
= 0; scan
< batch_size
; scan
++) {
3241 struct page
*page
= lru_to_page(l_unevictable
);
3243 if (!trylock_page(page
))
3246 prefetchw_prev_lru_page(page
, l_unevictable
, flags
);
3248 if (likely(PageLRU(page
) && PageUnevictable(page
)))
3249 check_move_unevictable_page(page
, zone
);
3253 spin_unlock_irq(&zone
->lru_lock
);
3255 nr_to_scan
-= batch_size
;
3261 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
3263 * A really big hammer: scan all zones' unevictable LRU lists to check for
3264 * pages that have become evictable. Move those back to the zones'
3265 * inactive list where they become candidates for reclaim.
3266 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
3267 * and we add swap to the system. As such, it runs in the context of a task
3268 * that has possibly/probably made some previously unevictable pages
3271 static void scan_all_zones_unevictable_pages(void)
3275 for_each_zone(zone
) {
3276 scan_zone_unevictable_pages(zone
);
3281 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3282 * all nodes' unevictable lists for evictable pages
3284 unsigned long scan_unevictable_pages
;
3286 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
3287 void __user
*buffer
,
3288 size_t *length
, loff_t
*ppos
)
3290 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
3292 if (write
&& *(unsigned long *)table
->data
)
3293 scan_all_zones_unevictable_pages();
3295 scan_unevictable_pages
= 0;
3301 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3302 * a specified node's per zone unevictable lists for evictable pages.
3305 static ssize_t
read_scan_unevictable_node(struct sys_device
*dev
,
3306 struct sysdev_attribute
*attr
,
3309 return sprintf(buf
, "0\n"); /* always zero; should fit... */
3312 static ssize_t
write_scan_unevictable_node(struct sys_device
*dev
,
3313 struct sysdev_attribute
*attr
,
3314 const char *buf
, size_t count
)
3316 struct zone
*node_zones
= NODE_DATA(dev
->id
)->node_zones
;
3319 unsigned long req
= strict_strtoul(buf
, 10, &res
);
3322 return 1; /* zero is no-op */
3324 for (zone
= node_zones
; zone
- node_zones
< MAX_NR_ZONES
; ++zone
) {
3325 if (!populated_zone(zone
))
3327 scan_zone_unevictable_pages(zone
);
3333 static SYSDEV_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
3334 read_scan_unevictable_node
,
3335 write_scan_unevictable_node
);
3337 int scan_unevictable_register_node(struct node
*node
)
3339 return sysdev_create_file(&node
->sysdev
, &attr_scan_unevictable_pages
);
3342 void scan_unevictable_unregister_node(struct node
*node
)
3344 sysdev_remove_file(&node
->sysdev
, &attr_scan_unevictable_pages
);