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 if (PageLRU(page
)) {
1211 struct zone
*zone
= page_zone(page
);
1213 spin_lock_irq(&zone
->lru_lock
);
1214 if (PageLRU(page
) && get_page_unless_zero(page
)) {
1215 int lru
= page_lru(page
);
1219 del_page_from_lru_list(zone
, page
, lru
);
1221 spin_unlock_irq(&zone
->lru_lock
);
1227 * Are there way too many processes in the direct reclaim path already?
1229 static int too_many_isolated(struct zone
*zone
, int file
,
1230 struct scan_control
*sc
)
1232 unsigned long inactive
, isolated
;
1234 if (current_is_kswapd())
1237 if (!scanning_global_lru(sc
))
1241 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1242 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1244 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1245 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1248 return isolated
> inactive
;
1252 * TODO: Try merging with migrations version of putback_lru_pages
1254 static noinline_for_stack
void
1255 putback_lru_pages(struct zone
*zone
, struct scan_control
*sc
,
1256 unsigned long nr_anon
, unsigned long nr_file
,
1257 struct list_head
*page_list
)
1260 struct pagevec pvec
;
1261 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1263 pagevec_init(&pvec
, 1);
1266 * Put back any unfreeable pages.
1268 spin_lock(&zone
->lru_lock
);
1269 while (!list_empty(page_list
)) {
1271 page
= lru_to_page(page_list
);
1272 VM_BUG_ON(PageLRU(page
));
1273 list_del(&page
->lru
);
1274 if (unlikely(!page_evictable(page
, NULL
))) {
1275 spin_unlock_irq(&zone
->lru_lock
);
1276 putback_lru_page(page
);
1277 spin_lock_irq(&zone
->lru_lock
);
1281 lru
= page_lru(page
);
1282 add_page_to_lru_list(zone
, page
, lru
);
1283 if (is_active_lru(lru
)) {
1284 int file
= is_file_lru(lru
);
1285 int numpages
= hpage_nr_pages(page
);
1286 reclaim_stat
->recent_rotated
[file
] += numpages
;
1288 if (!pagevec_add(&pvec
, page
)) {
1289 spin_unlock_irq(&zone
->lru_lock
);
1290 __pagevec_release(&pvec
);
1291 spin_lock_irq(&zone
->lru_lock
);
1294 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, -nr_anon
);
1295 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -nr_file
);
1297 spin_unlock_irq(&zone
->lru_lock
);
1298 pagevec_release(&pvec
);
1301 static noinline_for_stack
void update_isolated_counts(struct zone
*zone
,
1302 struct scan_control
*sc
,
1303 unsigned long *nr_anon
,
1304 unsigned long *nr_file
,
1305 struct list_head
*isolated_list
)
1307 unsigned long nr_active
;
1308 unsigned int count
[NR_LRU_LISTS
] = { 0, };
1309 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1311 nr_active
= clear_active_flags(isolated_list
, count
);
1312 __count_vm_events(PGDEACTIVATE
, nr_active
);
1314 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
1315 -count
[LRU_ACTIVE_FILE
]);
1316 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
1317 -count
[LRU_INACTIVE_FILE
]);
1318 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
1319 -count
[LRU_ACTIVE_ANON
]);
1320 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
1321 -count
[LRU_INACTIVE_ANON
]);
1323 *nr_anon
= count
[LRU_ACTIVE_ANON
] + count
[LRU_INACTIVE_ANON
];
1324 *nr_file
= count
[LRU_ACTIVE_FILE
] + count
[LRU_INACTIVE_FILE
];
1325 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, *nr_anon
);
1326 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, *nr_file
);
1328 reclaim_stat
->recent_scanned
[0] += *nr_anon
;
1329 reclaim_stat
->recent_scanned
[1] += *nr_file
;
1333 * Returns true if the caller should wait to clean dirty/writeback pages.
1335 * If we are direct reclaiming for contiguous pages and we do not reclaim
1336 * everything in the list, try again and wait for writeback IO to complete.
1337 * This will stall high-order allocations noticeably. Only do that when really
1338 * need to free the pages under high memory pressure.
1340 static inline bool should_reclaim_stall(unsigned long nr_taken
,
1341 unsigned long nr_freed
,
1343 struct scan_control
*sc
)
1345 int lumpy_stall_priority
;
1347 /* kswapd should not stall on sync IO */
1348 if (current_is_kswapd())
1351 /* Only stall on lumpy reclaim */
1352 if (sc
->reclaim_mode
& RECLAIM_MODE_SINGLE
)
1355 /* If we have relaimed everything on the isolated list, no stall */
1356 if (nr_freed
== nr_taken
)
1360 * For high-order allocations, there are two stall thresholds.
1361 * High-cost allocations stall immediately where as lower
1362 * order allocations such as stacks require the scanning
1363 * priority to be much higher before stalling.
1365 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
1366 lumpy_stall_priority
= DEF_PRIORITY
;
1368 lumpy_stall_priority
= DEF_PRIORITY
/ 3;
1370 return priority
<= lumpy_stall_priority
;
1374 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1375 * of reclaimed pages
1377 static noinline_for_stack
unsigned long
1378 shrink_inactive_list(unsigned long nr_to_scan
, struct zone
*zone
,
1379 struct scan_control
*sc
, int priority
, int file
)
1381 LIST_HEAD(page_list
);
1382 unsigned long nr_scanned
;
1383 unsigned long nr_reclaimed
= 0;
1384 unsigned long nr_taken
;
1385 unsigned long nr_anon
;
1386 unsigned long nr_file
;
1388 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1389 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1391 /* We are about to die and free our memory. Return now. */
1392 if (fatal_signal_pending(current
))
1393 return SWAP_CLUSTER_MAX
;
1396 set_reclaim_mode(priority
, sc
, false);
1398 spin_lock_irq(&zone
->lru_lock
);
1400 if (scanning_global_lru(sc
)) {
1401 nr_taken
= isolate_pages_global(nr_to_scan
,
1402 &page_list
, &nr_scanned
, sc
->order
,
1403 sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
?
1404 ISOLATE_BOTH
: ISOLATE_INACTIVE
,
1406 zone
->pages_scanned
+= nr_scanned
;
1407 if (current_is_kswapd())
1408 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
,
1411 __count_zone_vm_events(PGSCAN_DIRECT
, zone
,
1414 nr_taken
= mem_cgroup_isolate_pages(nr_to_scan
,
1415 &page_list
, &nr_scanned
, sc
->order
,
1416 sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
?
1417 ISOLATE_BOTH
: ISOLATE_INACTIVE
,
1418 zone
, sc
->mem_cgroup
,
1421 * mem_cgroup_isolate_pages() keeps track of
1422 * scanned pages on its own.
1426 if (nr_taken
== 0) {
1427 spin_unlock_irq(&zone
->lru_lock
);
1431 update_isolated_counts(zone
, sc
, &nr_anon
, &nr_file
, &page_list
);
1433 spin_unlock_irq(&zone
->lru_lock
);
1435 nr_reclaimed
= shrink_page_list(&page_list
, zone
, sc
);
1437 /* Check if we should syncronously wait for writeback */
1438 if (should_reclaim_stall(nr_taken
, nr_reclaimed
, priority
, sc
)) {
1439 set_reclaim_mode(priority
, sc
, true);
1440 nr_reclaimed
+= shrink_page_list(&page_list
, zone
, sc
);
1443 local_irq_disable();
1444 if (current_is_kswapd())
1445 __count_vm_events(KSWAPD_STEAL
, nr_reclaimed
);
1446 __count_zone_vm_events(PGSTEAL
, zone
, nr_reclaimed
);
1448 putback_lru_pages(zone
, sc
, nr_anon
, nr_file
, &page_list
);
1450 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1452 nr_scanned
, nr_reclaimed
,
1454 trace_shrink_flags(file
, sc
->reclaim_mode
));
1455 return nr_reclaimed
;
1459 * This moves pages from the active list to the inactive list.
1461 * We move them the other way if the page is referenced by one or more
1462 * processes, from rmap.
1464 * If the pages are mostly unmapped, the processing is fast and it is
1465 * appropriate to hold zone->lru_lock across the whole operation. But if
1466 * the pages are mapped, the processing is slow (page_referenced()) so we
1467 * should drop zone->lru_lock around each page. It's impossible to balance
1468 * this, so instead we remove the pages from the LRU while processing them.
1469 * It is safe to rely on PG_active against the non-LRU pages in here because
1470 * nobody will play with that bit on a non-LRU page.
1472 * The downside is that we have to touch page->_count against each page.
1473 * But we had to alter page->flags anyway.
1476 static void move_active_pages_to_lru(struct zone
*zone
,
1477 struct list_head
*list
,
1480 unsigned long pgmoved
= 0;
1481 struct pagevec pvec
;
1484 pagevec_init(&pvec
, 1);
1486 while (!list_empty(list
)) {
1487 page
= lru_to_page(list
);
1489 VM_BUG_ON(PageLRU(page
));
1492 list_move(&page
->lru
, &zone
->lru
[lru
].list
);
1493 mem_cgroup_add_lru_list(page
, lru
);
1494 pgmoved
+= hpage_nr_pages(page
);
1496 if (!pagevec_add(&pvec
, page
) || list_empty(list
)) {
1497 spin_unlock_irq(&zone
->lru_lock
);
1498 if (buffer_heads_over_limit
)
1499 pagevec_strip(&pvec
);
1500 __pagevec_release(&pvec
);
1501 spin_lock_irq(&zone
->lru_lock
);
1504 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1505 if (!is_active_lru(lru
))
1506 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1509 static void shrink_active_list(unsigned long nr_pages
, struct zone
*zone
,
1510 struct scan_control
*sc
, int priority
, int file
)
1512 unsigned long nr_taken
;
1513 unsigned long pgscanned
;
1514 unsigned long vm_flags
;
1515 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1516 LIST_HEAD(l_active
);
1517 LIST_HEAD(l_inactive
);
1519 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1520 unsigned long nr_rotated
= 0;
1523 spin_lock_irq(&zone
->lru_lock
);
1524 if (scanning_global_lru(sc
)) {
1525 nr_taken
= isolate_pages_global(nr_pages
, &l_hold
,
1526 &pgscanned
, sc
->order
,
1527 ISOLATE_ACTIVE
, zone
,
1529 zone
->pages_scanned
+= pgscanned
;
1531 nr_taken
= mem_cgroup_isolate_pages(nr_pages
, &l_hold
,
1532 &pgscanned
, sc
->order
,
1533 ISOLATE_ACTIVE
, zone
,
1534 sc
->mem_cgroup
, 1, file
);
1536 * mem_cgroup_isolate_pages() keeps track of
1537 * scanned pages on its own.
1541 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1543 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1545 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -nr_taken
);
1547 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -nr_taken
);
1548 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1549 spin_unlock_irq(&zone
->lru_lock
);
1551 while (!list_empty(&l_hold
)) {
1553 page
= lru_to_page(&l_hold
);
1554 list_del(&page
->lru
);
1556 if (unlikely(!page_evictable(page
, NULL
))) {
1557 putback_lru_page(page
);
1561 if (page_referenced(page
, 0, sc
->mem_cgroup
, &vm_flags
)) {
1562 nr_rotated
+= hpage_nr_pages(page
);
1564 * Identify referenced, file-backed active pages and
1565 * give them one more trip around the active list. So
1566 * that executable code get better chances to stay in
1567 * memory under moderate memory pressure. Anon pages
1568 * are not likely to be evicted by use-once streaming
1569 * IO, plus JVM can create lots of anon VM_EXEC pages,
1570 * so we ignore them here.
1572 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1573 list_add(&page
->lru
, &l_active
);
1578 ClearPageActive(page
); /* we are de-activating */
1579 list_add(&page
->lru
, &l_inactive
);
1583 * Move pages back to the lru list.
1585 spin_lock_irq(&zone
->lru_lock
);
1587 * Count referenced pages from currently used mappings as rotated,
1588 * even though only some of them are actually re-activated. This
1589 * helps balance scan pressure between file and anonymous pages in
1592 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1594 move_active_pages_to_lru(zone
, &l_active
,
1595 LRU_ACTIVE
+ file
* LRU_FILE
);
1596 move_active_pages_to_lru(zone
, &l_inactive
,
1597 LRU_BASE
+ file
* LRU_FILE
);
1598 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1599 spin_unlock_irq(&zone
->lru_lock
);
1603 static int inactive_anon_is_low_global(struct zone
*zone
)
1605 unsigned long active
, inactive
;
1607 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1608 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1610 if (inactive
* zone
->inactive_ratio
< active
)
1617 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1618 * @zone: zone to check
1619 * @sc: scan control of this context
1621 * Returns true if the zone does not have enough inactive anon pages,
1622 * meaning some active anon pages need to be deactivated.
1624 static int inactive_anon_is_low(struct zone
*zone
, struct scan_control
*sc
)
1629 * If we don't have swap space, anonymous page deactivation
1632 if (!total_swap_pages
)
1635 if (scanning_global_lru(sc
))
1636 low
= inactive_anon_is_low_global(zone
);
1638 low
= mem_cgroup_inactive_anon_is_low(sc
->mem_cgroup
);
1642 static inline int inactive_anon_is_low(struct zone
*zone
,
1643 struct scan_control
*sc
)
1649 static int inactive_file_is_low_global(struct zone
*zone
)
1651 unsigned long active
, inactive
;
1653 active
= zone_page_state(zone
, NR_ACTIVE_FILE
);
1654 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1656 return (active
> inactive
);
1660 * inactive_file_is_low - check if file pages need to be deactivated
1661 * @zone: zone to check
1662 * @sc: scan control of this context
1664 * When the system is doing streaming IO, memory pressure here
1665 * ensures that active file pages get deactivated, until more
1666 * than half of the file pages are on the inactive list.
1668 * Once we get to that situation, protect the system's working
1669 * set from being evicted by disabling active file page aging.
1671 * This uses a different ratio than the anonymous pages, because
1672 * the page cache uses a use-once replacement algorithm.
1674 static int inactive_file_is_low(struct zone
*zone
, struct scan_control
*sc
)
1678 if (scanning_global_lru(sc
))
1679 low
= inactive_file_is_low_global(zone
);
1681 low
= mem_cgroup_inactive_file_is_low(sc
->mem_cgroup
);
1685 static int inactive_list_is_low(struct zone
*zone
, struct scan_control
*sc
,
1689 return inactive_file_is_low(zone
, sc
);
1691 return inactive_anon_is_low(zone
, sc
);
1694 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1695 struct zone
*zone
, struct scan_control
*sc
, int priority
)
1697 int file
= is_file_lru(lru
);
1699 if (is_active_lru(lru
)) {
1700 if (inactive_list_is_low(zone
, sc
, file
))
1701 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1705 return shrink_inactive_list(nr_to_scan
, zone
, sc
, priority
, file
);
1709 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1710 * until we collected @swap_cluster_max pages to scan.
1712 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan
,
1713 unsigned long *nr_saved_scan
)
1717 *nr_saved_scan
+= nr_to_scan
;
1718 nr
= *nr_saved_scan
;
1720 if (nr
>= SWAP_CLUSTER_MAX
)
1729 * Determine how aggressively the anon and file LRU lists should be
1730 * scanned. The relative value of each set of LRU lists is determined
1731 * by looking at the fraction of the pages scanned we did rotate back
1732 * onto the active list instead of evict.
1734 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1736 static void get_scan_count(struct zone
*zone
, struct scan_control
*sc
,
1737 unsigned long *nr
, int priority
)
1739 unsigned long anon
, file
, free
;
1740 unsigned long anon_prio
, file_prio
;
1741 unsigned long ap
, fp
;
1742 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1743 u64 fraction
[2], denominator
;
1747 /* If we have no swap space, do not bother scanning anon pages. */
1748 if (!sc
->may_swap
|| (nr_swap_pages
<= 0)) {
1756 anon
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_ANON
) +
1757 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
);
1758 file
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_FILE
) +
1759 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
1761 if (scanning_global_lru(sc
)) {
1762 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1763 /* If we have very few page cache pages,
1764 force-scan anon pages. */
1765 if (unlikely(file
+ free
<= high_wmark_pages(zone
))) {
1774 * With swappiness at 100, anonymous and file have the same priority.
1775 * This scanning priority is essentially the inverse of IO cost.
1777 anon_prio
= sc
->swappiness
;
1778 file_prio
= 200 - sc
->swappiness
;
1781 * OK, so we have swap space and a fair amount of page cache
1782 * pages. We use the recently rotated / recently scanned
1783 * ratios to determine how valuable each cache is.
1785 * Because workloads change over time (and to avoid overflow)
1786 * we keep these statistics as a floating average, which ends
1787 * up weighing recent references more than old ones.
1789 * anon in [0], file in [1]
1791 spin_lock_irq(&zone
->lru_lock
);
1792 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1793 reclaim_stat
->recent_scanned
[0] /= 2;
1794 reclaim_stat
->recent_rotated
[0] /= 2;
1797 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1798 reclaim_stat
->recent_scanned
[1] /= 2;
1799 reclaim_stat
->recent_rotated
[1] /= 2;
1803 * The amount of pressure on anon vs file pages is inversely
1804 * proportional to the fraction of recently scanned pages on
1805 * each list that were recently referenced and in active use.
1807 ap
= (anon_prio
+ 1) * (reclaim_stat
->recent_scanned
[0] + 1);
1808 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1810 fp
= (file_prio
+ 1) * (reclaim_stat
->recent_scanned
[1] + 1);
1811 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1812 spin_unlock_irq(&zone
->lru_lock
);
1816 denominator
= ap
+ fp
+ 1;
1818 for_each_evictable_lru(l
) {
1819 int file
= is_file_lru(l
);
1822 scan
= zone_nr_lru_pages(zone
, sc
, l
);
1823 if (priority
|| noswap
) {
1825 scan
= div64_u64(scan
* fraction
[file
], denominator
);
1827 nr
[l
] = nr_scan_try_batch(scan
,
1828 &reclaim_stat
->nr_saved_scan
[l
]);
1833 * Reclaim/compaction depends on a number of pages being freed. To avoid
1834 * disruption to the system, a small number of order-0 pages continue to be
1835 * rotated and reclaimed in the normal fashion. However, by the time we get
1836 * back to the allocator and call try_to_compact_zone(), we ensure that
1837 * there are enough free pages for it to be likely successful
1839 static inline bool should_continue_reclaim(struct zone
*zone
,
1840 unsigned long nr_reclaimed
,
1841 unsigned long nr_scanned
,
1842 struct scan_control
*sc
)
1844 unsigned long pages_for_compaction
;
1845 unsigned long inactive_lru_pages
;
1847 /* If not in reclaim/compaction mode, stop */
1848 if (!(sc
->reclaim_mode
& RECLAIM_MODE_COMPACTION
))
1851 /* Consider stopping depending on scan and reclaim activity */
1852 if (sc
->gfp_mask
& __GFP_REPEAT
) {
1854 * For __GFP_REPEAT allocations, stop reclaiming if the
1855 * full LRU list has been scanned and we are still failing
1856 * to reclaim pages. This full LRU scan is potentially
1857 * expensive but a __GFP_REPEAT caller really wants to succeed
1859 if (!nr_reclaimed
&& !nr_scanned
)
1863 * For non-__GFP_REPEAT allocations which can presumably
1864 * fail without consequence, stop if we failed to reclaim
1865 * any pages from the last SWAP_CLUSTER_MAX number of
1866 * pages that were scanned. This will return to the
1867 * caller faster at the risk reclaim/compaction and
1868 * the resulting allocation attempt fails
1875 * If we have not reclaimed enough pages for compaction and the
1876 * inactive lists are large enough, continue reclaiming
1878 pages_for_compaction
= (2UL << sc
->order
);
1879 inactive_lru_pages
= zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
) +
1880 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
1881 if (sc
->nr_reclaimed
< pages_for_compaction
&&
1882 inactive_lru_pages
> pages_for_compaction
)
1885 /* If compaction would go ahead or the allocation would succeed, stop */
1886 switch (compaction_suitable(zone
, sc
->order
)) {
1887 case COMPACT_PARTIAL
:
1888 case COMPACT_CONTINUE
:
1896 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1898 static void shrink_zone(int priority
, struct zone
*zone
,
1899 struct scan_control
*sc
)
1901 unsigned long nr
[NR_LRU_LISTS
];
1902 unsigned long nr_to_scan
;
1904 unsigned long nr_reclaimed
, nr_scanned
;
1905 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
1909 nr_scanned
= sc
->nr_scanned
;
1910 get_scan_count(zone
, sc
, nr
, priority
);
1912 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
1913 nr
[LRU_INACTIVE_FILE
]) {
1914 for_each_evictable_lru(l
) {
1916 nr_to_scan
= min_t(unsigned long,
1917 nr
[l
], SWAP_CLUSTER_MAX
);
1918 nr
[l
] -= nr_to_scan
;
1920 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
1921 zone
, sc
, priority
);
1925 * On large memory systems, scan >> priority can become
1926 * really large. This is fine for the starting priority;
1927 * we want to put equal scanning pressure on each zone.
1928 * However, if the VM has a harder time of freeing pages,
1929 * with multiple processes reclaiming pages, the total
1930 * freeing target can get unreasonably large.
1932 if (nr_reclaimed
>= nr_to_reclaim
&& priority
< DEF_PRIORITY
)
1935 sc
->nr_reclaimed
+= nr_reclaimed
;
1938 * Even if we did not try to evict anon pages at all, we want to
1939 * rebalance the anon lru active/inactive ratio.
1941 if (inactive_anon_is_low(zone
, sc
))
1942 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
1944 /* reclaim/compaction might need reclaim to continue */
1945 if (should_continue_reclaim(zone
, nr_reclaimed
,
1946 sc
->nr_scanned
- nr_scanned
, sc
))
1949 throttle_vm_writeout(sc
->gfp_mask
);
1953 * This is the direct reclaim path, for page-allocating processes. We only
1954 * try to reclaim pages from zones which will satisfy the caller's allocation
1957 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1959 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1961 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1962 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1963 * zone defense algorithm.
1965 * If a zone is deemed to be full of pinned pages then just give it a light
1966 * scan then give up on it.
1968 static void shrink_zones(int priority
, struct zonelist
*zonelist
,
1969 struct scan_control
*sc
)
1974 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
1975 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
1976 if (!populated_zone(zone
))
1979 * Take care memory controller reclaiming has small influence
1982 if (scanning_global_lru(sc
)) {
1983 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1985 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
1986 continue; /* Let kswapd poll it */
1989 shrink_zone(priority
, zone
, sc
);
1993 static bool zone_reclaimable(struct zone
*zone
)
1995 return zone
->pages_scanned
< zone_reclaimable_pages(zone
) * 6;
1998 /* All zones in zonelist are unreclaimable? */
1999 static bool all_unreclaimable(struct zonelist
*zonelist
,
2000 struct scan_control
*sc
)
2005 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2006 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2007 if (!populated_zone(zone
))
2009 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2011 if (!zone
->all_unreclaimable
)
2019 * This is the main entry point to direct page reclaim.
2021 * If a full scan of the inactive list fails to free enough memory then we
2022 * are "out of memory" and something needs to be killed.
2024 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2025 * high - the zone may be full of dirty or under-writeback pages, which this
2026 * caller can't do much about. We kick the writeback threads and take explicit
2027 * naps in the hope that some of these pages can be written. But if the
2028 * allocating task holds filesystem locks which prevent writeout this might not
2029 * work, and the allocation attempt will fail.
2031 * returns: 0, if no pages reclaimed
2032 * else, the number of pages reclaimed
2034 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2035 struct scan_control
*sc
)
2038 unsigned long total_scanned
= 0;
2039 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2042 unsigned long writeback_threshold
;
2045 delayacct_freepages_start();
2047 if (scanning_global_lru(sc
))
2048 count_vm_event(ALLOCSTALL
);
2050 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2053 disable_swap_token();
2054 shrink_zones(priority
, zonelist
, sc
);
2056 * Don't shrink slabs when reclaiming memory from
2057 * over limit cgroups
2059 if (scanning_global_lru(sc
)) {
2060 unsigned long lru_pages
= 0;
2061 for_each_zone_zonelist(zone
, z
, zonelist
,
2062 gfp_zone(sc
->gfp_mask
)) {
2063 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2066 lru_pages
+= zone_reclaimable_pages(zone
);
2069 shrink_slab(sc
->nr_scanned
, sc
->gfp_mask
, lru_pages
);
2070 if (reclaim_state
) {
2071 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2072 reclaim_state
->reclaimed_slab
= 0;
2075 total_scanned
+= sc
->nr_scanned
;
2076 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2080 * Try to write back as many pages as we just scanned. This
2081 * tends to cause slow streaming writers to write data to the
2082 * disk smoothly, at the dirtying rate, which is nice. But
2083 * that's undesirable in laptop mode, where we *want* lumpy
2084 * writeout. So in laptop mode, write out the whole world.
2086 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2087 if (total_scanned
> writeback_threshold
) {
2088 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
);
2089 sc
->may_writepage
= 1;
2092 /* Take a nap, wait for some writeback to complete */
2093 if (!sc
->hibernation_mode
&& sc
->nr_scanned
&&
2094 priority
< DEF_PRIORITY
- 2) {
2095 struct zone
*preferred_zone
;
2097 first_zones_zonelist(zonelist
, gfp_zone(sc
->gfp_mask
),
2098 &cpuset_current_mems_allowed
,
2100 wait_iff_congested(preferred_zone
, BLK_RW_ASYNC
, HZ
/10);
2105 delayacct_freepages_end();
2108 if (sc
->nr_reclaimed
)
2109 return sc
->nr_reclaimed
;
2112 * As hibernation is going on, kswapd is freezed so that it can't mark
2113 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2116 if (oom_killer_disabled
)
2119 /* top priority shrink_zones still had more to do? don't OOM, then */
2120 if (scanning_global_lru(sc
) && !all_unreclaimable(zonelist
, sc
))
2126 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2127 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2129 unsigned long nr_reclaimed
;
2130 struct scan_control sc
= {
2131 .gfp_mask
= gfp_mask
,
2132 .may_writepage
= !laptop_mode
,
2133 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2136 .swappiness
= vm_swappiness
,
2139 .nodemask
= nodemask
,
2142 trace_mm_vmscan_direct_reclaim_begin(order
,
2146 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2148 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2150 return nr_reclaimed
;
2153 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2155 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*mem
,
2156 gfp_t gfp_mask
, bool noswap
,
2157 unsigned int swappiness
,
2160 struct scan_control sc
= {
2161 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2162 .may_writepage
= !laptop_mode
,
2164 .may_swap
= !noswap
,
2165 .swappiness
= swappiness
,
2169 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2170 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2172 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2177 * NOTE: Although we can get the priority field, using it
2178 * here is not a good idea, since it limits the pages we can scan.
2179 * if we don't reclaim here, the shrink_zone from balance_pgdat
2180 * will pick up pages from other mem cgroup's as well. We hack
2181 * the priority and make it zero.
2183 shrink_zone(0, zone
, &sc
);
2185 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2187 return sc
.nr_reclaimed
;
2190 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*mem_cont
,
2193 unsigned int swappiness
)
2195 struct zonelist
*zonelist
;
2196 unsigned long nr_reclaimed
;
2197 struct scan_control sc
= {
2198 .may_writepage
= !laptop_mode
,
2200 .may_swap
= !noswap
,
2201 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2202 .swappiness
= swappiness
,
2204 .mem_cgroup
= mem_cont
,
2205 .nodemask
= NULL
, /* we don't care the placement */
2208 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2209 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2210 zonelist
= NODE_DATA(numa_node_id())->node_zonelists
;
2212 trace_mm_vmscan_memcg_reclaim_begin(0,
2216 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2218 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2220 return nr_reclaimed
;
2225 * pgdat_balanced is used when checking if a node is balanced for high-order
2226 * allocations. Only zones that meet watermarks and are in a zone allowed
2227 * by the callers classzone_idx are added to balanced_pages. The total of
2228 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2229 * for the node to be considered balanced. Forcing all zones to be balanced
2230 * for high orders can cause excessive reclaim when there are imbalanced zones.
2231 * The choice of 25% is due to
2232 * o a 16M DMA zone that is balanced will not balance a zone on any
2233 * reasonable sized machine
2234 * o On all other machines, the top zone must be at least a reasonable
2235 * percentage of the middle zones. For example, on 32-bit x86, highmem
2236 * would need to be at least 256M for it to be balance a whole node.
2237 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2238 * to balance a node on its own. These seemed like reasonable ratios.
2240 static bool pgdat_balanced(pg_data_t
*pgdat
, unsigned long balanced_pages
,
2243 unsigned long present_pages
= 0;
2246 for (i
= 0; i
<= classzone_idx
; i
++)
2247 present_pages
+= pgdat
->node_zones
[i
].present_pages
;
2249 return balanced_pages
> (present_pages
>> 2);
2252 /* is kswapd sleeping prematurely? */
2253 static bool sleeping_prematurely(pg_data_t
*pgdat
, int order
, long remaining
,
2257 unsigned long balanced
= 0;
2258 bool all_zones_ok
= true;
2260 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2264 /* Check the watermark levels */
2265 for (i
= 0; i
< pgdat
->nr_zones
; i
++) {
2266 struct zone
*zone
= pgdat
->node_zones
+ i
;
2268 if (!populated_zone(zone
))
2272 * balance_pgdat() skips over all_unreclaimable after
2273 * DEF_PRIORITY. Effectively, it considers them balanced so
2274 * they must be considered balanced here as well if kswapd
2277 if (zone
->all_unreclaimable
) {
2278 balanced
+= zone
->present_pages
;
2282 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
),
2284 all_zones_ok
= false;
2286 balanced
+= zone
->present_pages
;
2290 * For high-order requests, the balanced zones must contain at least
2291 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2295 return !pgdat_balanced(pgdat
, balanced
, classzone_idx
);
2297 return !all_zones_ok
;
2301 * For kswapd, balance_pgdat() will work across all this node's zones until
2302 * they are all at high_wmark_pages(zone).
2304 * Returns the final order kswapd was reclaiming at
2306 * There is special handling here for zones which are full of pinned pages.
2307 * This can happen if the pages are all mlocked, or if they are all used by
2308 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2309 * What we do is to detect the case where all pages in the zone have been
2310 * scanned twice and there has been zero successful reclaim. Mark the zone as
2311 * dead and from now on, only perform a short scan. Basically we're polling
2312 * the zone for when the problem goes away.
2314 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2315 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2316 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2317 * lower zones regardless of the number of free pages in the lower zones. This
2318 * interoperates with the page allocator fallback scheme to ensure that aging
2319 * of pages is balanced across the zones.
2321 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
2325 unsigned long balanced
;
2328 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
2329 unsigned long total_scanned
;
2330 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2331 struct scan_control sc
= {
2332 .gfp_mask
= GFP_KERNEL
,
2336 * kswapd doesn't want to be bailed out while reclaim. because
2337 * we want to put equal scanning pressure on each zone.
2339 .nr_to_reclaim
= ULONG_MAX
,
2340 .swappiness
= vm_swappiness
,
2346 sc
.nr_reclaimed
= 0;
2347 sc
.may_writepage
= !laptop_mode
;
2348 count_vm_event(PAGEOUTRUN
);
2350 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2351 unsigned long lru_pages
= 0;
2352 int has_under_min_watermark_zone
= 0;
2354 /* The swap token gets in the way of swapout... */
2356 disable_swap_token();
2362 * Scan in the highmem->dma direction for the highest
2363 * zone which needs scanning
2365 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
2366 struct zone
*zone
= pgdat
->node_zones
+ i
;
2368 if (!populated_zone(zone
))
2371 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2375 * Do some background aging of the anon list, to give
2376 * pages a chance to be referenced before reclaiming.
2378 if (inactive_anon_is_low(zone
, &sc
))
2379 shrink_active_list(SWAP_CLUSTER_MAX
, zone
,
2382 if (!zone_watermark_ok_safe(zone
, order
,
2383 high_wmark_pages(zone
), 0, 0)) {
2392 for (i
= 0; i
<= end_zone
; i
++) {
2393 struct zone
*zone
= pgdat
->node_zones
+ i
;
2395 lru_pages
+= zone_reclaimable_pages(zone
);
2399 * Now scan the zone in the dma->highmem direction, stopping
2400 * at the last zone which needs scanning.
2402 * We do this because the page allocator works in the opposite
2403 * direction. This prevents the page allocator from allocating
2404 * pages behind kswapd's direction of progress, which would
2405 * cause too much scanning of the lower zones.
2407 for (i
= 0; i
<= end_zone
; i
++) {
2408 struct zone
*zone
= pgdat
->node_zones
+ i
;
2410 unsigned long balance_gap
;
2412 if (!populated_zone(zone
))
2415 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2421 * Call soft limit reclaim before calling shrink_zone.
2422 * For now we ignore the return value
2424 mem_cgroup_soft_limit_reclaim(zone
, order
, sc
.gfp_mask
);
2427 * We put equal pressure on every zone, unless
2428 * one zone has way too many pages free
2429 * already. The "too many pages" is defined
2430 * as the high wmark plus a "gap" where the
2431 * gap is either the low watermark or 1%
2432 * of the zone, whichever is smaller.
2434 balance_gap
= min(low_wmark_pages(zone
),
2435 (zone
->present_pages
+
2436 KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2437 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2438 if (!zone_watermark_ok_safe(zone
, order
,
2439 high_wmark_pages(zone
) + balance_gap
,
2441 shrink_zone(priority
, zone
, &sc
);
2442 reclaim_state
->reclaimed_slab
= 0;
2443 nr_slab
= shrink_slab(sc
.nr_scanned
, GFP_KERNEL
,
2445 sc
.nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2446 total_scanned
+= sc
.nr_scanned
;
2448 if (zone
->all_unreclaimable
)
2451 !zone_reclaimable(zone
))
2452 zone
->all_unreclaimable
= 1;
2454 * If we've done a decent amount of scanning and
2455 * the reclaim ratio is low, start doing writepage
2456 * even in laptop mode
2458 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
2459 total_scanned
> sc
.nr_reclaimed
+ sc
.nr_reclaimed
/ 2)
2460 sc
.may_writepage
= 1;
2462 if (!zone_watermark_ok_safe(zone
, order
,
2463 high_wmark_pages(zone
), end_zone
, 0)) {
2466 * We are still under min water mark. This
2467 * means that we have a GFP_ATOMIC allocation
2468 * failure risk. Hurry up!
2470 if (!zone_watermark_ok_safe(zone
, order
,
2471 min_wmark_pages(zone
), end_zone
, 0))
2472 has_under_min_watermark_zone
= 1;
2475 * If a zone reaches its high watermark,
2476 * consider it to be no longer congested. It's
2477 * possible there are dirty pages backed by
2478 * congested BDIs but as pressure is relieved,
2479 * spectulatively avoid congestion waits
2481 zone_clear_flag(zone
, ZONE_CONGESTED
);
2482 if (i
<= *classzone_idx
)
2483 balanced
+= zone
->present_pages
;
2487 if (all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))
2488 break; /* kswapd: all done */
2490 * OK, kswapd is getting into trouble. Take a nap, then take
2491 * another pass across the zones.
2493 if (total_scanned
&& (priority
< DEF_PRIORITY
- 2)) {
2494 if (has_under_min_watermark_zone
)
2495 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT
);
2497 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
2501 * We do this so kswapd doesn't build up large priorities for
2502 * example when it is freeing in parallel with allocators. It
2503 * matches the direct reclaim path behaviour in terms of impact
2504 * on zone->*_priority.
2506 if (sc
.nr_reclaimed
>= SWAP_CLUSTER_MAX
)
2512 * order-0: All zones must meet high watermark for a balanced node
2513 * high-order: Balanced zones must make up at least 25% of the node
2514 * for the node to be balanced
2516 if (!(all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))) {
2522 * Fragmentation may mean that the system cannot be
2523 * rebalanced for high-order allocations in all zones.
2524 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2525 * it means the zones have been fully scanned and are still
2526 * not balanced. For high-order allocations, there is
2527 * little point trying all over again as kswapd may
2530 * Instead, recheck all watermarks at order-0 as they
2531 * are the most important. If watermarks are ok, kswapd will go
2532 * back to sleep. High-order users can still perform direct
2533 * reclaim if they wish.
2535 if (sc
.nr_reclaimed
< SWAP_CLUSTER_MAX
)
2536 order
= sc
.order
= 0;
2542 * If kswapd was reclaiming at a higher order, it has the option of
2543 * sleeping without all zones being balanced. Before it does, it must
2544 * ensure that the watermarks for order-0 on *all* zones are met and
2545 * that the congestion flags are cleared. The congestion flag must
2546 * be cleared as kswapd is the only mechanism that clears the flag
2547 * and it is potentially going to sleep here.
2550 for (i
= 0; i
<= end_zone
; i
++) {
2551 struct zone
*zone
= pgdat
->node_zones
+ i
;
2553 if (!populated_zone(zone
))
2556 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2559 /* Confirm the zone is balanced for order-0 */
2560 if (!zone_watermark_ok(zone
, 0,
2561 high_wmark_pages(zone
), 0, 0)) {
2562 order
= sc
.order
= 0;
2566 /* If balanced, clear the congested flag */
2567 zone_clear_flag(zone
, ZONE_CONGESTED
);
2572 * Return the order we were reclaiming at so sleeping_prematurely()
2573 * makes a decision on the order we were last reclaiming at. However,
2574 * if another caller entered the allocator slow path while kswapd
2575 * was awake, order will remain at the higher level
2577 *classzone_idx
= end_zone
;
2581 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2586 if (freezing(current
) || kthread_should_stop())
2589 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2591 /* Try to sleep for a short interval */
2592 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2593 remaining
= schedule_timeout(HZ
/10);
2594 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2595 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2599 * After a short sleep, check if it was a premature sleep. If not, then
2600 * go fully to sleep until explicitly woken up.
2602 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2603 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
2606 * vmstat counters are not perfectly accurate and the estimated
2607 * value for counters such as NR_FREE_PAGES can deviate from the
2608 * true value by nr_online_cpus * threshold. To avoid the zone
2609 * watermarks being breached while under pressure, we reduce the
2610 * per-cpu vmstat threshold while kswapd is awake and restore
2611 * them before going back to sleep.
2613 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
2615 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
2618 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
2620 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
2622 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2626 * The background pageout daemon, started as a kernel thread
2627 * from the init process.
2629 * This basically trickles out pages so that we have _some_
2630 * free memory available even if there is no other activity
2631 * that frees anything up. This is needed for things like routing
2632 * etc, where we otherwise might have all activity going on in
2633 * asynchronous contexts that cannot page things out.
2635 * If there are applications that are active memory-allocators
2636 * (most normal use), this basically shouldn't matter.
2638 static int kswapd(void *p
)
2640 unsigned long order
;
2642 pg_data_t
*pgdat
= (pg_data_t
*)p
;
2643 struct task_struct
*tsk
= current
;
2645 struct reclaim_state reclaim_state
= {
2646 .reclaimed_slab
= 0,
2648 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
2650 lockdep_set_current_reclaim_state(GFP_KERNEL
);
2652 if (!cpumask_empty(cpumask
))
2653 set_cpus_allowed_ptr(tsk
, cpumask
);
2654 current
->reclaim_state
= &reclaim_state
;
2657 * Tell the memory management that we're a "memory allocator",
2658 * and that if we need more memory we should get access to it
2659 * regardless (see "__alloc_pages()"). "kswapd" should
2660 * never get caught in the normal page freeing logic.
2662 * (Kswapd normally doesn't need memory anyway, but sometimes
2663 * you need a small amount of memory in order to be able to
2664 * page out something else, and this flag essentially protects
2665 * us from recursively trying to free more memory as we're
2666 * trying to free the first piece of memory in the first place).
2668 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
2672 classzone_idx
= MAX_NR_ZONES
- 1;
2674 unsigned long new_order
;
2675 int new_classzone_idx
;
2678 new_order
= pgdat
->kswapd_max_order
;
2679 new_classzone_idx
= pgdat
->classzone_idx
;
2680 pgdat
->kswapd_max_order
= 0;
2681 pgdat
->classzone_idx
= MAX_NR_ZONES
- 1;
2682 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
2684 * Don't sleep if someone wants a larger 'order'
2685 * allocation or has tigher zone constraints
2688 classzone_idx
= new_classzone_idx
;
2690 kswapd_try_to_sleep(pgdat
, order
, classzone_idx
);
2691 order
= pgdat
->kswapd_max_order
;
2692 classzone_idx
= pgdat
->classzone_idx
;
2693 pgdat
->kswapd_max_order
= 0;
2694 pgdat
->classzone_idx
= MAX_NR_ZONES
- 1;
2697 ret
= try_to_freeze();
2698 if (kthread_should_stop())
2702 * We can speed up thawing tasks if we don't call balance_pgdat
2703 * after returning from the refrigerator
2706 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
2707 order
= balance_pgdat(pgdat
, order
, &classzone_idx
);
2714 * A zone is low on free memory, so wake its kswapd task to service it.
2716 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
2720 if (!populated_zone(zone
))
2723 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2725 pgdat
= zone
->zone_pgdat
;
2726 if (pgdat
->kswapd_max_order
< order
) {
2727 pgdat
->kswapd_max_order
= order
;
2728 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
2730 if (!waitqueue_active(&pgdat
->kswapd_wait
))
2732 if (zone_watermark_ok_safe(zone
, order
, low_wmark_pages(zone
), 0, 0))
2735 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
2736 wake_up_interruptible(&pgdat
->kswapd_wait
);
2740 * The reclaimable count would be mostly accurate.
2741 * The less reclaimable pages may be
2742 * - mlocked pages, which will be moved to unevictable list when encountered
2743 * - mapped pages, which may require several travels to be reclaimed
2744 * - dirty pages, which is not "instantly" reclaimable
2746 unsigned long global_reclaimable_pages(void)
2750 nr
= global_page_state(NR_ACTIVE_FILE
) +
2751 global_page_state(NR_INACTIVE_FILE
);
2753 if (nr_swap_pages
> 0)
2754 nr
+= global_page_state(NR_ACTIVE_ANON
) +
2755 global_page_state(NR_INACTIVE_ANON
);
2760 unsigned long zone_reclaimable_pages(struct zone
*zone
)
2764 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
2765 zone_page_state(zone
, NR_INACTIVE_FILE
);
2767 if (nr_swap_pages
> 0)
2768 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
2769 zone_page_state(zone
, NR_INACTIVE_ANON
);
2774 #ifdef CONFIG_HIBERNATION
2776 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2779 * Rather than trying to age LRUs the aim is to preserve the overall
2780 * LRU order by reclaiming preferentially
2781 * inactive > active > active referenced > active mapped
2783 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
2785 struct reclaim_state reclaim_state
;
2786 struct scan_control sc
= {
2787 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
2791 .nr_to_reclaim
= nr_to_reclaim
,
2792 .hibernation_mode
= 1,
2793 .swappiness
= vm_swappiness
,
2796 struct zonelist
* zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
2797 struct task_struct
*p
= current
;
2798 unsigned long nr_reclaimed
;
2800 p
->flags
|= PF_MEMALLOC
;
2801 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
2802 reclaim_state
.reclaimed_slab
= 0;
2803 p
->reclaim_state
= &reclaim_state
;
2805 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2807 p
->reclaim_state
= NULL
;
2808 lockdep_clear_current_reclaim_state();
2809 p
->flags
&= ~PF_MEMALLOC
;
2811 return nr_reclaimed
;
2813 #endif /* CONFIG_HIBERNATION */
2815 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2816 not required for correctness. So if the last cpu in a node goes
2817 away, we get changed to run anywhere: as the first one comes back,
2818 restore their cpu bindings. */
2819 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
2820 unsigned long action
, void *hcpu
)
2824 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
2825 for_each_node_state(nid
, N_HIGH_MEMORY
) {
2826 pg_data_t
*pgdat
= NODE_DATA(nid
);
2827 const struct cpumask
*mask
;
2829 mask
= cpumask_of_node(pgdat
->node_id
);
2831 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
2832 /* One of our CPUs online: restore mask */
2833 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
2840 * This kswapd start function will be called by init and node-hot-add.
2841 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2843 int kswapd_run(int nid
)
2845 pg_data_t
*pgdat
= NODE_DATA(nid
);
2851 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
2852 if (IS_ERR(pgdat
->kswapd
)) {
2853 /* failure at boot is fatal */
2854 BUG_ON(system_state
== SYSTEM_BOOTING
);
2855 printk("Failed to start kswapd on node %d\n",nid
);
2862 * Called by memory hotplug when all memory in a node is offlined.
2864 void kswapd_stop(int nid
)
2866 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
2869 kthread_stop(kswapd
);
2872 static int __init
kswapd_init(void)
2877 for_each_node_state(nid
, N_HIGH_MEMORY
)
2879 hotcpu_notifier(cpu_callback
, 0);
2883 module_init(kswapd_init
)
2889 * If non-zero call zone_reclaim when the number of free pages falls below
2892 int zone_reclaim_mode __read_mostly
;
2894 #define RECLAIM_OFF 0
2895 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2896 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2897 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2900 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2901 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2904 #define ZONE_RECLAIM_PRIORITY 4
2907 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2910 int sysctl_min_unmapped_ratio
= 1;
2913 * If the number of slab pages in a zone grows beyond this percentage then
2914 * slab reclaim needs to occur.
2916 int sysctl_min_slab_ratio
= 5;
2918 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
2920 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
2921 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
2922 zone_page_state(zone
, NR_ACTIVE_FILE
);
2925 * It's possible for there to be more file mapped pages than
2926 * accounted for by the pages on the file LRU lists because
2927 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2929 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
2932 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2933 static long zone_pagecache_reclaimable(struct zone
*zone
)
2935 long nr_pagecache_reclaimable
;
2939 * If RECLAIM_SWAP is set, then all file pages are considered
2940 * potentially reclaimable. Otherwise, we have to worry about
2941 * pages like swapcache and zone_unmapped_file_pages() provides
2944 if (zone_reclaim_mode
& RECLAIM_SWAP
)
2945 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
2947 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
2949 /* If we can't clean pages, remove dirty pages from consideration */
2950 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
2951 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
2953 /* Watch for any possible underflows due to delta */
2954 if (unlikely(delta
> nr_pagecache_reclaimable
))
2955 delta
= nr_pagecache_reclaimable
;
2957 return nr_pagecache_reclaimable
- delta
;
2961 * Try to free up some pages from this zone through reclaim.
2963 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2965 /* Minimum pages needed in order to stay on node */
2966 const unsigned long nr_pages
= 1 << order
;
2967 struct task_struct
*p
= current
;
2968 struct reclaim_state reclaim_state
;
2970 struct scan_control sc
= {
2971 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
2972 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
2974 .nr_to_reclaim
= max_t(unsigned long, nr_pages
,
2976 .gfp_mask
= gfp_mask
,
2977 .swappiness
= vm_swappiness
,
2980 unsigned long nr_slab_pages0
, nr_slab_pages1
;
2984 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2985 * and we also need to be able to write out pages for RECLAIM_WRITE
2988 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
2989 lockdep_set_current_reclaim_state(gfp_mask
);
2990 reclaim_state
.reclaimed_slab
= 0;
2991 p
->reclaim_state
= &reclaim_state
;
2993 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
2995 * Free memory by calling shrink zone with increasing
2996 * priorities until we have enough memory freed.
2998 priority
= ZONE_RECLAIM_PRIORITY
;
3000 shrink_zone(priority
, zone
, &sc
);
3002 } while (priority
>= 0 && sc
.nr_reclaimed
< nr_pages
);
3005 nr_slab_pages0
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3006 if (nr_slab_pages0
> zone
->min_slab_pages
) {
3008 * shrink_slab() does not currently allow us to determine how
3009 * many pages were freed in this zone. So we take the current
3010 * number of slab pages and shake the slab until it is reduced
3011 * by the same nr_pages that we used for reclaiming unmapped
3014 * Note that shrink_slab will free memory on all zones and may
3018 unsigned long lru_pages
= zone_reclaimable_pages(zone
);
3020 /* No reclaimable slab or very low memory pressure */
3021 if (!shrink_slab(sc
.nr_scanned
, gfp_mask
, lru_pages
))
3024 /* Freed enough memory */
3025 nr_slab_pages1
= zone_page_state(zone
,
3026 NR_SLAB_RECLAIMABLE
);
3027 if (nr_slab_pages1
+ nr_pages
<= nr_slab_pages0
)
3032 * Update nr_reclaimed by the number of slab pages we
3033 * reclaimed from this zone.
3035 nr_slab_pages1
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3036 if (nr_slab_pages1
< nr_slab_pages0
)
3037 sc
.nr_reclaimed
+= nr_slab_pages0
- nr_slab_pages1
;
3040 p
->reclaim_state
= NULL
;
3041 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3042 lockdep_clear_current_reclaim_state();
3043 return sc
.nr_reclaimed
>= nr_pages
;
3046 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3052 * Zone reclaim reclaims unmapped file backed pages and
3053 * slab pages if we are over the defined limits.
3055 * A small portion of unmapped file backed pages is needed for
3056 * file I/O otherwise pages read by file I/O will be immediately
3057 * thrown out if the zone is overallocated. So we do not reclaim
3058 * if less than a specified percentage of the zone is used by
3059 * unmapped file backed pages.
3061 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3062 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3063 return ZONE_RECLAIM_FULL
;
3065 if (zone
->all_unreclaimable
)
3066 return ZONE_RECLAIM_FULL
;
3069 * Do not scan if the allocation should not be delayed.
3071 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3072 return ZONE_RECLAIM_NOSCAN
;
3075 * Only run zone reclaim on the local zone or on zones that do not
3076 * have associated processors. This will favor the local processor
3077 * over remote processors and spread off node memory allocations
3078 * as wide as possible.
3080 node_id
= zone_to_nid(zone
);
3081 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3082 return ZONE_RECLAIM_NOSCAN
;
3084 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
3085 return ZONE_RECLAIM_NOSCAN
;
3087 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3088 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
3091 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3098 * page_evictable - test whether a page is evictable
3099 * @page: the page to test
3100 * @vma: the VMA in which the page is or will be mapped, may be NULL
3102 * Test whether page is evictable--i.e., should be placed on active/inactive
3103 * lists vs unevictable list. The vma argument is !NULL when called from the
3104 * fault path to determine how to instantate a new page.
3106 * Reasons page might not be evictable:
3107 * (1) page's mapping marked unevictable
3108 * (2) page is part of an mlocked VMA
3111 int page_evictable(struct page
*page
, struct vm_area_struct
*vma
)
3114 if (mapping_unevictable(page_mapping(page
)))
3117 if (PageMlocked(page
) || (vma
&& is_mlocked_vma(vma
, page
)))
3124 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3125 * @page: page to check evictability and move to appropriate lru list
3126 * @zone: zone page is in
3128 * Checks a page for evictability and moves the page to the appropriate
3131 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3132 * have PageUnevictable set.
3134 static void check_move_unevictable_page(struct page
*page
, struct zone
*zone
)
3136 VM_BUG_ON(PageActive(page
));
3139 ClearPageUnevictable(page
);
3140 if (page_evictable(page
, NULL
)) {
3141 enum lru_list l
= page_lru_base_type(page
);
3143 __dec_zone_state(zone
, NR_UNEVICTABLE
);
3144 list_move(&page
->lru
, &zone
->lru
[l
].list
);
3145 mem_cgroup_move_lists(page
, LRU_UNEVICTABLE
, l
);
3146 __inc_zone_state(zone
, NR_INACTIVE_ANON
+ l
);
3147 __count_vm_event(UNEVICTABLE_PGRESCUED
);
3150 * rotate unevictable list
3152 SetPageUnevictable(page
);
3153 list_move(&page
->lru
, &zone
->lru
[LRU_UNEVICTABLE
].list
);
3154 mem_cgroup_rotate_lru_list(page
, LRU_UNEVICTABLE
);
3155 if (page_evictable(page
, NULL
))
3161 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3162 * @mapping: struct address_space to scan for evictable pages
3164 * Scan all pages in mapping. Check unevictable pages for
3165 * evictability and move them to the appropriate zone lru list.
3167 void scan_mapping_unevictable_pages(struct address_space
*mapping
)
3170 pgoff_t end
= (i_size_read(mapping
->host
) + PAGE_CACHE_SIZE
- 1) >>
3173 struct pagevec pvec
;
3175 if (mapping
->nrpages
== 0)
3178 pagevec_init(&pvec
, 0);
3179 while (next
< end
&&
3180 pagevec_lookup(&pvec
, mapping
, next
, PAGEVEC_SIZE
)) {
3186 for (i
= 0; i
< pagevec_count(&pvec
); i
++) {
3187 struct page
*page
= pvec
.pages
[i
];
3188 pgoff_t page_index
= page
->index
;
3189 struct zone
*pagezone
= page_zone(page
);
3192 if (page_index
> next
)
3196 if (pagezone
!= zone
) {
3198 spin_unlock_irq(&zone
->lru_lock
);
3200 spin_lock_irq(&zone
->lru_lock
);
3203 if (PageLRU(page
) && PageUnevictable(page
))
3204 check_move_unevictable_page(page
, zone
);
3207 spin_unlock_irq(&zone
->lru_lock
);
3208 pagevec_release(&pvec
);
3210 count_vm_events(UNEVICTABLE_PGSCANNED
, pg_scanned
);
3216 * scan_zone_unevictable_pages - check unevictable list for evictable pages
3217 * @zone - zone of which to scan the unevictable list
3219 * Scan @zone's unevictable LRU lists to check for pages that have become
3220 * evictable. Move those that have to @zone's inactive list where they
3221 * become candidates for reclaim, unless shrink_inactive_zone() decides
3222 * to reactivate them. Pages that are still unevictable are rotated
3223 * back onto @zone's unevictable list.
3225 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
3226 static void scan_zone_unevictable_pages(struct zone
*zone
)
3228 struct list_head
*l_unevictable
= &zone
->lru
[LRU_UNEVICTABLE
].list
;
3230 unsigned long nr_to_scan
= zone_page_state(zone
, NR_UNEVICTABLE
);
3232 while (nr_to_scan
> 0) {
3233 unsigned long batch_size
= min(nr_to_scan
,
3234 SCAN_UNEVICTABLE_BATCH_SIZE
);
3236 spin_lock_irq(&zone
->lru_lock
);
3237 for (scan
= 0; scan
< batch_size
; scan
++) {
3238 struct page
*page
= lru_to_page(l_unevictable
);
3240 if (!trylock_page(page
))
3243 prefetchw_prev_lru_page(page
, l_unevictable
, flags
);
3245 if (likely(PageLRU(page
) && PageUnevictable(page
)))
3246 check_move_unevictable_page(page
, zone
);
3250 spin_unlock_irq(&zone
->lru_lock
);
3252 nr_to_scan
-= batch_size
;
3258 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
3260 * A really big hammer: scan all zones' unevictable LRU lists to check for
3261 * pages that have become evictable. Move those back to the zones'
3262 * inactive list where they become candidates for reclaim.
3263 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
3264 * and we add swap to the system. As such, it runs in the context of a task
3265 * that has possibly/probably made some previously unevictable pages
3268 static void scan_all_zones_unevictable_pages(void)
3272 for_each_zone(zone
) {
3273 scan_zone_unevictable_pages(zone
);
3278 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3279 * all nodes' unevictable lists for evictable pages
3281 unsigned long scan_unevictable_pages
;
3283 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
3284 void __user
*buffer
,
3285 size_t *length
, loff_t
*ppos
)
3287 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
3289 if (write
&& *(unsigned long *)table
->data
)
3290 scan_all_zones_unevictable_pages();
3292 scan_unevictable_pages
= 0;
3298 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3299 * a specified node's per zone unevictable lists for evictable pages.
3302 static ssize_t
read_scan_unevictable_node(struct sys_device
*dev
,
3303 struct sysdev_attribute
*attr
,
3306 return sprintf(buf
, "0\n"); /* always zero; should fit... */
3309 static ssize_t
write_scan_unevictable_node(struct sys_device
*dev
,
3310 struct sysdev_attribute
*attr
,
3311 const char *buf
, size_t count
)
3313 struct zone
*node_zones
= NODE_DATA(dev
->id
)->node_zones
;
3316 unsigned long req
= strict_strtoul(buf
, 10, &res
);
3319 return 1; /* zero is no-op */
3321 for (zone
= node_zones
; zone
- node_zones
< MAX_NR_ZONES
; ++zone
) {
3322 if (!populated_zone(zone
))
3324 scan_zone_unevictable_pages(zone
);
3330 static SYSDEV_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
3331 read_scan_unevictable_node
,
3332 write_scan_unevictable_node
);
3334 int scan_unevictable_register_node(struct node
*node
)
3336 return sysdev_create_file(&node
->sysdev
, &attr_scan_unevictable_pages
);
3339 void scan_unevictable_unregister_node(struct node
*node
)
3341 sysdev_remove_file(&node
->sysdev
, &attr_scan_unevictable_pages
);