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? */
101 * Intend to reclaim enough continuous memory rather than reclaim
102 * enough amount of memory. i.e, mode for high order allocation.
104 reclaim_mode_t reclaim_mode
;
107 * The memory cgroup that hit its limit and as a result is the
108 * primary target of this reclaim invocation.
110 struct mem_cgroup
*target_mem_cgroup
;
113 * Nodemask of nodes allowed by the caller. If NULL, all nodes
116 nodemask_t
*nodemask
;
119 struct mem_cgroup_zone
{
120 struct mem_cgroup
*mem_cgroup
;
124 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
126 #ifdef ARCH_HAS_PREFETCH
127 #define prefetch_prev_lru_page(_page, _base, _field) \
129 if ((_page)->lru.prev != _base) { \
132 prev = lru_to_page(&(_page->lru)); \
133 prefetch(&prev->_field); \
137 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
140 #ifdef ARCH_HAS_PREFETCHW
141 #define prefetchw_prev_lru_page(_page, _base, _field) \
143 if ((_page)->lru.prev != _base) { \
146 prev = lru_to_page(&(_page->lru)); \
147 prefetchw(&prev->_field); \
151 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
155 * From 0 .. 100. Higher means more swappy.
157 int vm_swappiness
= 60;
158 long vm_total_pages
; /* The total number of pages which the VM controls */
160 static LIST_HEAD(shrinker_list
);
161 static DECLARE_RWSEM(shrinker_rwsem
);
163 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
164 static bool global_reclaim(struct scan_control
*sc
)
166 return !sc
->target_mem_cgroup
;
169 static bool scanning_global_lru(struct mem_cgroup_zone
*mz
)
171 return !mz
->mem_cgroup
;
174 static bool global_reclaim(struct scan_control
*sc
)
179 static bool scanning_global_lru(struct mem_cgroup_zone
*mz
)
185 static struct zone_reclaim_stat
*get_reclaim_stat(struct mem_cgroup_zone
*mz
)
187 if (!scanning_global_lru(mz
))
188 return mem_cgroup_get_reclaim_stat(mz
->mem_cgroup
, mz
->zone
);
190 return &mz
->zone
->reclaim_stat
;
193 static unsigned long zone_nr_lru_pages(struct mem_cgroup_zone
*mz
,
196 if (!scanning_global_lru(mz
))
197 return mem_cgroup_zone_nr_lru_pages(mz
->mem_cgroup
,
198 zone_to_nid(mz
->zone
),
202 return zone_page_state(mz
->zone
, NR_LRU_BASE
+ lru
);
207 * Add a shrinker callback to be called from the vm
209 void register_shrinker(struct shrinker
*shrinker
)
211 atomic_long_set(&shrinker
->nr_in_batch
, 0);
212 down_write(&shrinker_rwsem
);
213 list_add_tail(&shrinker
->list
, &shrinker_list
);
214 up_write(&shrinker_rwsem
);
216 EXPORT_SYMBOL(register_shrinker
);
221 void unregister_shrinker(struct shrinker
*shrinker
)
223 down_write(&shrinker_rwsem
);
224 list_del(&shrinker
->list
);
225 up_write(&shrinker_rwsem
);
227 EXPORT_SYMBOL(unregister_shrinker
);
229 static inline int do_shrinker_shrink(struct shrinker
*shrinker
,
230 struct shrink_control
*sc
,
231 unsigned long nr_to_scan
)
233 sc
->nr_to_scan
= nr_to_scan
;
234 return (*shrinker
->shrink
)(shrinker
, sc
);
237 #define SHRINK_BATCH 128
239 * Call the shrink functions to age shrinkable caches
241 * Here we assume it costs one seek to replace a lru page and that it also
242 * takes a seek to recreate a cache object. With this in mind we age equal
243 * percentages of the lru and ageable caches. This should balance the seeks
244 * generated by these structures.
246 * If the vm encountered mapped pages on the LRU it increase the pressure on
247 * slab to avoid swapping.
249 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
251 * `lru_pages' represents the number of on-LRU pages in all the zones which
252 * are eligible for the caller's allocation attempt. It is used for balancing
253 * slab reclaim versus page reclaim.
255 * Returns the number of slab objects which we shrunk.
257 unsigned long shrink_slab(struct shrink_control
*shrink
,
258 unsigned long nr_pages_scanned
,
259 unsigned long lru_pages
)
261 struct shrinker
*shrinker
;
262 unsigned long ret
= 0;
264 if (nr_pages_scanned
== 0)
265 nr_pages_scanned
= SWAP_CLUSTER_MAX
;
267 if (!down_read_trylock(&shrinker_rwsem
)) {
268 /* Assume we'll be able to shrink next time */
273 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
274 unsigned long long delta
;
280 long batch_size
= shrinker
->batch
? shrinker
->batch
283 max_pass
= do_shrinker_shrink(shrinker
, shrink
, 0);
288 * copy the current shrinker scan count into a local variable
289 * and zero it so that other concurrent shrinker invocations
290 * don't also do this scanning work.
292 nr
= atomic_long_xchg(&shrinker
->nr_in_batch
, 0);
295 delta
= (4 * nr_pages_scanned
) / shrinker
->seeks
;
297 do_div(delta
, lru_pages
+ 1);
299 if (total_scan
< 0) {
300 printk(KERN_ERR
"shrink_slab: %pF negative objects to "
302 shrinker
->shrink
, total_scan
);
303 total_scan
= max_pass
;
307 * We need to avoid excessive windup on filesystem shrinkers
308 * due to large numbers of GFP_NOFS allocations causing the
309 * shrinkers to return -1 all the time. This results in a large
310 * nr being built up so when a shrink that can do some work
311 * comes along it empties the entire cache due to nr >>>
312 * max_pass. This is bad for sustaining a working set in
315 * Hence only allow the shrinker to scan the entire cache when
316 * a large delta change is calculated directly.
318 if (delta
< max_pass
/ 4)
319 total_scan
= min(total_scan
, max_pass
/ 2);
322 * Avoid risking looping forever due to too large nr value:
323 * never try to free more than twice the estimate number of
326 if (total_scan
> max_pass
* 2)
327 total_scan
= max_pass
* 2;
329 trace_mm_shrink_slab_start(shrinker
, shrink
, nr
,
330 nr_pages_scanned
, lru_pages
,
331 max_pass
, delta
, total_scan
);
333 while (total_scan
>= batch_size
) {
336 nr_before
= do_shrinker_shrink(shrinker
, shrink
, 0);
337 shrink_ret
= do_shrinker_shrink(shrinker
, shrink
,
339 if (shrink_ret
== -1)
341 if (shrink_ret
< nr_before
)
342 ret
+= nr_before
- shrink_ret
;
343 count_vm_events(SLABS_SCANNED
, batch_size
);
344 total_scan
-= batch_size
;
350 * move the unused scan count back into the shrinker in a
351 * manner that handles concurrent updates. If we exhausted the
352 * scan, there is no need to do an update.
355 new_nr
= atomic_long_add_return(total_scan
,
356 &shrinker
->nr_in_batch
);
358 new_nr
= atomic_long_read(&shrinker
->nr_in_batch
);
360 trace_mm_shrink_slab_end(shrinker
, shrink_ret
, nr
, new_nr
);
362 up_read(&shrinker_rwsem
);
368 static void set_reclaim_mode(int priority
, struct scan_control
*sc
,
371 reclaim_mode_t syncmode
= sync
? RECLAIM_MODE_SYNC
: RECLAIM_MODE_ASYNC
;
374 * Initially assume we are entering either lumpy reclaim or
375 * reclaim/compaction.Depending on the order, we will either set the
376 * sync mode or just reclaim order-0 pages later.
378 if (COMPACTION_BUILD
)
379 sc
->reclaim_mode
= RECLAIM_MODE_COMPACTION
;
381 sc
->reclaim_mode
= RECLAIM_MODE_LUMPYRECLAIM
;
384 * Avoid using lumpy reclaim or reclaim/compaction if possible by
385 * restricting when its set to either costly allocations or when
386 * under memory pressure
388 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
389 sc
->reclaim_mode
|= syncmode
;
390 else if (sc
->order
&& priority
< DEF_PRIORITY
- 2)
391 sc
->reclaim_mode
|= syncmode
;
393 sc
->reclaim_mode
= RECLAIM_MODE_SINGLE
| RECLAIM_MODE_ASYNC
;
396 static void reset_reclaim_mode(struct scan_control
*sc
)
398 sc
->reclaim_mode
= RECLAIM_MODE_SINGLE
| RECLAIM_MODE_ASYNC
;
401 static inline int is_page_cache_freeable(struct page
*page
)
404 * A freeable page cache page is referenced only by the caller
405 * that isolated the page, the page cache radix tree and
406 * optional buffer heads at page->private.
408 return page_count(page
) - page_has_private(page
) == 2;
411 static int may_write_to_queue(struct backing_dev_info
*bdi
,
412 struct scan_control
*sc
)
414 if (current
->flags
& PF_SWAPWRITE
)
416 if (!bdi_write_congested(bdi
))
418 if (bdi
== current
->backing_dev_info
)
421 /* lumpy reclaim for hugepage often need a lot of write */
422 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
428 * We detected a synchronous write error writing a page out. Probably
429 * -ENOSPC. We need to propagate that into the address_space for a subsequent
430 * fsync(), msync() or close().
432 * The tricky part is that after writepage we cannot touch the mapping: nothing
433 * prevents it from being freed up. But we have a ref on the page and once
434 * that page is locked, the mapping is pinned.
436 * We're allowed to run sleeping lock_page() here because we know the caller has
439 static void handle_write_error(struct address_space
*mapping
,
440 struct page
*page
, int error
)
443 if (page_mapping(page
) == mapping
)
444 mapping_set_error(mapping
, error
);
448 /* possible outcome of pageout() */
450 /* failed to write page out, page is locked */
452 /* move page to the active list, page is locked */
454 /* page has been sent to the disk successfully, page is unlocked */
456 /* page is clean and locked */
461 * pageout is called by shrink_page_list() for each dirty page.
462 * Calls ->writepage().
464 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
465 struct scan_control
*sc
)
468 * If the page is dirty, only perform writeback if that write
469 * will be non-blocking. To prevent this allocation from being
470 * stalled by pagecache activity. But note that there may be
471 * stalls if we need to run get_block(). We could test
472 * PagePrivate for that.
474 * If this process is currently in __generic_file_aio_write() against
475 * this page's queue, we can perform writeback even if that
478 * If the page is swapcache, write it back even if that would
479 * block, for some throttling. This happens by accident, because
480 * swap_backing_dev_info is bust: it doesn't reflect the
481 * congestion state of the swapdevs. Easy to fix, if needed.
483 if (!is_page_cache_freeable(page
))
487 * Some data journaling orphaned pages can have
488 * page->mapping == NULL while being dirty with clean buffers.
490 if (page_has_private(page
)) {
491 if (try_to_free_buffers(page
)) {
492 ClearPageDirty(page
);
493 printk("%s: orphaned page\n", __func__
);
499 if (mapping
->a_ops
->writepage
== NULL
)
500 return PAGE_ACTIVATE
;
501 if (!may_write_to_queue(mapping
->backing_dev_info
, sc
))
504 if (clear_page_dirty_for_io(page
)) {
506 struct writeback_control wbc
= {
507 .sync_mode
= WB_SYNC_NONE
,
508 .nr_to_write
= SWAP_CLUSTER_MAX
,
510 .range_end
= LLONG_MAX
,
514 SetPageReclaim(page
);
515 res
= mapping
->a_ops
->writepage(page
, &wbc
);
517 handle_write_error(mapping
, page
, res
);
518 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
519 ClearPageReclaim(page
);
520 return PAGE_ACTIVATE
;
523 if (!PageWriteback(page
)) {
524 /* synchronous write or broken a_ops? */
525 ClearPageReclaim(page
);
527 trace_mm_vmscan_writepage(page
,
528 trace_reclaim_flags(page
, sc
->reclaim_mode
));
529 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
537 * Same as remove_mapping, but if the page is removed from the mapping, it
538 * gets returned with a refcount of 0.
540 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
)
542 BUG_ON(!PageLocked(page
));
543 BUG_ON(mapping
!= page_mapping(page
));
545 spin_lock_irq(&mapping
->tree_lock
);
547 * The non racy check for a busy page.
549 * Must be careful with the order of the tests. When someone has
550 * a ref to the page, it may be possible that they dirty it then
551 * drop the reference. So if PageDirty is tested before page_count
552 * here, then the following race may occur:
554 * get_user_pages(&page);
555 * [user mapping goes away]
557 * !PageDirty(page) [good]
558 * SetPageDirty(page);
560 * !page_count(page) [good, discard it]
562 * [oops, our write_to data is lost]
564 * Reversing the order of the tests ensures such a situation cannot
565 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
566 * load is not satisfied before that of page->_count.
568 * Note that if SetPageDirty is always performed via set_page_dirty,
569 * and thus under tree_lock, then this ordering is not required.
571 if (!page_freeze_refs(page
, 2))
573 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
574 if (unlikely(PageDirty(page
))) {
575 page_unfreeze_refs(page
, 2);
579 if (PageSwapCache(page
)) {
580 swp_entry_t swap
= { .val
= page_private(page
) };
581 __delete_from_swap_cache(page
);
582 spin_unlock_irq(&mapping
->tree_lock
);
583 swapcache_free(swap
, page
);
585 void (*freepage
)(struct page
*);
587 freepage
= mapping
->a_ops
->freepage
;
589 __delete_from_page_cache(page
);
590 spin_unlock_irq(&mapping
->tree_lock
);
591 mem_cgroup_uncharge_cache_page(page
);
593 if (freepage
!= NULL
)
600 spin_unlock_irq(&mapping
->tree_lock
);
605 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
606 * someone else has a ref on the page, abort and return 0. If it was
607 * successfully detached, return 1. Assumes the caller has a single ref on
610 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
612 if (__remove_mapping(mapping
, page
)) {
614 * Unfreezing the refcount with 1 rather than 2 effectively
615 * drops the pagecache ref for us without requiring another
618 page_unfreeze_refs(page
, 1);
625 * putback_lru_page - put previously isolated page onto appropriate LRU list
626 * @page: page to be put back to appropriate lru list
628 * Add previously isolated @page to appropriate LRU list.
629 * Page may still be unevictable for other reasons.
631 * lru_lock must not be held, interrupts must be enabled.
633 void putback_lru_page(struct page
*page
)
636 int active
= !!TestClearPageActive(page
);
637 int was_unevictable
= PageUnevictable(page
);
639 VM_BUG_ON(PageLRU(page
));
642 ClearPageUnevictable(page
);
644 if (page_evictable(page
, NULL
)) {
646 * For evictable pages, we can use the cache.
647 * In event of a race, worst case is we end up with an
648 * unevictable page on [in]active list.
649 * We know how to handle that.
651 lru
= active
+ page_lru_base_type(page
);
652 lru_cache_add_lru(page
, lru
);
655 * Put unevictable pages directly on zone's unevictable
658 lru
= LRU_UNEVICTABLE
;
659 add_page_to_unevictable_list(page
);
661 * When racing with an mlock or AS_UNEVICTABLE clearing
662 * (page is unlocked) make sure that if the other thread
663 * does not observe our setting of PG_lru and fails
664 * isolation/check_move_unevictable_page,
665 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
666 * the page back to the evictable list.
668 * The other side is TestClearPageMlocked() or shmem_lock().
674 * page's status can change while we move it among lru. If an evictable
675 * page is on unevictable list, it never be freed. To avoid that,
676 * check after we added it to the list, again.
678 if (lru
== LRU_UNEVICTABLE
&& page_evictable(page
, NULL
)) {
679 if (!isolate_lru_page(page
)) {
683 /* This means someone else dropped this page from LRU
684 * So, it will be freed or putback to LRU again. There is
685 * nothing to do here.
689 if (was_unevictable
&& lru
!= LRU_UNEVICTABLE
)
690 count_vm_event(UNEVICTABLE_PGRESCUED
);
691 else if (!was_unevictable
&& lru
== LRU_UNEVICTABLE
)
692 count_vm_event(UNEVICTABLE_PGCULLED
);
694 put_page(page
); /* drop ref from isolate */
697 enum page_references
{
699 PAGEREF_RECLAIM_CLEAN
,
704 static enum page_references
page_check_references(struct page
*page
,
705 struct mem_cgroup_zone
*mz
,
706 struct scan_control
*sc
)
708 int referenced_ptes
, referenced_page
;
709 unsigned long vm_flags
;
711 referenced_ptes
= page_referenced(page
, 1, mz
->mem_cgroup
, &vm_flags
);
712 referenced_page
= TestClearPageReferenced(page
);
714 /* Lumpy reclaim - ignore references */
715 if (sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
)
716 return PAGEREF_RECLAIM
;
719 * Mlock lost the isolation race with us. Let try_to_unmap()
720 * move the page to the unevictable list.
722 if (vm_flags
& VM_LOCKED
)
723 return PAGEREF_RECLAIM
;
725 if (referenced_ptes
) {
727 return PAGEREF_ACTIVATE
;
729 * All mapped pages start out with page table
730 * references from the instantiating fault, so we need
731 * to look twice if a mapped file page is used more
734 * Mark it and spare it for another trip around the
735 * inactive list. Another page table reference will
736 * lead to its activation.
738 * Note: the mark is set for activated pages as well
739 * so that recently deactivated but used pages are
742 SetPageReferenced(page
);
744 if (referenced_page
|| referenced_ptes
> 1)
745 return PAGEREF_ACTIVATE
;
748 * Activate file-backed executable pages after first usage.
750 if (vm_flags
& VM_EXEC
)
751 return PAGEREF_ACTIVATE
;
756 /* Reclaim if clean, defer dirty pages to writeback */
757 if (referenced_page
&& !PageSwapBacked(page
))
758 return PAGEREF_RECLAIM_CLEAN
;
760 return PAGEREF_RECLAIM
;
764 * shrink_page_list() returns the number of reclaimed pages
766 static unsigned long shrink_page_list(struct list_head
*page_list
,
767 struct mem_cgroup_zone
*mz
,
768 struct scan_control
*sc
,
770 unsigned long *ret_nr_dirty
,
771 unsigned long *ret_nr_writeback
)
773 LIST_HEAD(ret_pages
);
774 LIST_HEAD(free_pages
);
776 unsigned long nr_dirty
= 0;
777 unsigned long nr_congested
= 0;
778 unsigned long nr_reclaimed
= 0;
779 unsigned long nr_writeback
= 0;
783 while (!list_empty(page_list
)) {
784 enum page_references references
;
785 struct address_space
*mapping
;
791 page
= lru_to_page(page_list
);
792 list_del(&page
->lru
);
794 if (!trylock_page(page
))
797 VM_BUG_ON(PageActive(page
));
798 VM_BUG_ON(page_zone(page
) != mz
->zone
);
802 if (unlikely(!page_evictable(page
, NULL
)))
805 if (!sc
->may_unmap
&& page_mapped(page
))
808 /* Double the slab pressure for mapped and swapcache pages */
809 if (page_mapped(page
) || PageSwapCache(page
))
812 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
813 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
815 if (PageWriteback(page
)) {
818 * Synchronous reclaim cannot queue pages for
819 * writeback due to the possibility of stack overflow
820 * but if it encounters a page under writeback, wait
821 * for the IO to complete.
823 if ((sc
->reclaim_mode
& RECLAIM_MODE_SYNC
) &&
825 wait_on_page_writeback(page
);
832 references
= page_check_references(page
, mz
, sc
);
833 switch (references
) {
834 case PAGEREF_ACTIVATE
:
835 goto activate_locked
;
838 case PAGEREF_RECLAIM
:
839 case PAGEREF_RECLAIM_CLEAN
:
840 ; /* try to reclaim the page below */
844 * Anonymous process memory has backing store?
845 * Try to allocate it some swap space here.
847 if (PageAnon(page
) && !PageSwapCache(page
)) {
848 if (!(sc
->gfp_mask
& __GFP_IO
))
850 if (!add_to_swap(page
))
851 goto activate_locked
;
855 mapping
= page_mapping(page
);
858 * The page is mapped into the page tables of one or more
859 * processes. Try to unmap it here.
861 if (page_mapped(page
) && mapping
) {
862 switch (try_to_unmap(page
, TTU_UNMAP
)) {
864 goto activate_locked
;
870 ; /* try to free the page below */
874 if (PageDirty(page
)) {
878 * Only kswapd can writeback filesystem pages to
879 * avoid risk of stack overflow but do not writeback
880 * unless under significant pressure.
882 if (page_is_file_cache(page
) &&
883 (!current_is_kswapd() || priority
>= DEF_PRIORITY
- 2)) {
885 * Immediately reclaim when written back.
886 * Similar in principal to deactivate_page()
887 * except we already have the page isolated
888 * and know it's dirty
890 inc_zone_page_state(page
, NR_VMSCAN_IMMEDIATE
);
891 SetPageReclaim(page
);
896 if (references
== PAGEREF_RECLAIM_CLEAN
)
900 if (!sc
->may_writepage
)
903 /* Page is dirty, try to write it out here */
904 switch (pageout(page
, mapping
, sc
)) {
909 goto activate_locked
;
911 if (PageWriteback(page
))
917 * A synchronous write - probably a ramdisk. Go
918 * ahead and try to reclaim the page.
920 if (!trylock_page(page
))
922 if (PageDirty(page
) || PageWriteback(page
))
924 mapping
= page_mapping(page
);
926 ; /* try to free the page below */
931 * If the page has buffers, try to free the buffer mappings
932 * associated with this page. If we succeed we try to free
935 * We do this even if the page is PageDirty().
936 * try_to_release_page() does not perform I/O, but it is
937 * possible for a page to have PageDirty set, but it is actually
938 * clean (all its buffers are clean). This happens if the
939 * buffers were written out directly, with submit_bh(). ext3
940 * will do this, as well as the blockdev mapping.
941 * try_to_release_page() will discover that cleanness and will
942 * drop the buffers and mark the page clean - it can be freed.
944 * Rarely, pages can have buffers and no ->mapping. These are
945 * the pages which were not successfully invalidated in
946 * truncate_complete_page(). We try to drop those buffers here
947 * and if that worked, and the page is no longer mapped into
948 * process address space (page_count == 1) it can be freed.
949 * Otherwise, leave the page on the LRU so it is swappable.
951 if (page_has_private(page
)) {
952 if (!try_to_release_page(page
, sc
->gfp_mask
))
953 goto activate_locked
;
954 if (!mapping
&& page_count(page
) == 1) {
956 if (put_page_testzero(page
))
960 * rare race with speculative reference.
961 * the speculative reference will free
962 * this page shortly, so we may
963 * increment nr_reclaimed here (and
964 * leave it off the LRU).
972 if (!mapping
|| !__remove_mapping(mapping
, page
))
976 * At this point, we have no other references and there is
977 * no way to pick any more up (removed from LRU, removed
978 * from pagecache). Can use non-atomic bitops now (and
979 * we obviously don't have to worry about waking up a process
980 * waiting on the page lock, because there are no references.
982 __clear_page_locked(page
);
987 * Is there need to periodically free_page_list? It would
988 * appear not as the counts should be low
990 list_add(&page
->lru
, &free_pages
);
994 if (PageSwapCache(page
))
995 try_to_free_swap(page
);
997 putback_lru_page(page
);
998 reset_reclaim_mode(sc
);
1002 /* Not a candidate for swapping, so reclaim swap space. */
1003 if (PageSwapCache(page
) && vm_swap_full())
1004 try_to_free_swap(page
);
1005 VM_BUG_ON(PageActive(page
));
1006 SetPageActive(page
);
1011 reset_reclaim_mode(sc
);
1013 list_add(&page
->lru
, &ret_pages
);
1014 VM_BUG_ON(PageLRU(page
) || PageUnevictable(page
));
1018 * Tag a zone as congested if all the dirty pages encountered were
1019 * backed by a congested BDI. In this case, reclaimers should just
1020 * back off and wait for congestion to clear because further reclaim
1021 * will encounter the same problem
1023 if (nr_dirty
&& nr_dirty
== nr_congested
&& global_reclaim(sc
))
1024 zone_set_flag(mz
->zone
, ZONE_CONGESTED
);
1026 free_hot_cold_page_list(&free_pages
, 1);
1028 list_splice(&ret_pages
, page_list
);
1029 count_vm_events(PGACTIVATE
, pgactivate
);
1030 *ret_nr_dirty
+= nr_dirty
;
1031 *ret_nr_writeback
+= nr_writeback
;
1032 return nr_reclaimed
;
1036 * Attempt to remove the specified page from its LRU. Only take this page
1037 * if it is of the appropriate PageActive status. Pages which are being
1038 * freed elsewhere are also ignored.
1040 * page: page to consider
1041 * mode: one of the LRU isolation modes defined above
1043 * returns 0 on success, -ve errno on failure.
1045 int __isolate_lru_page(struct page
*page
, isolate_mode_t mode
, int file
)
1050 /* Only take pages on the LRU. */
1054 all_lru_mode
= (mode
& (ISOLATE_ACTIVE
|ISOLATE_INACTIVE
)) ==
1055 (ISOLATE_ACTIVE
|ISOLATE_INACTIVE
);
1058 * When checking the active state, we need to be sure we are
1059 * dealing with comparible boolean values. Take the logical not
1062 if (!all_lru_mode
&& !PageActive(page
) != !(mode
& ISOLATE_ACTIVE
))
1065 if (!all_lru_mode
&& !!page_is_file_cache(page
) != file
)
1069 * When this function is being called for lumpy reclaim, we
1070 * initially look into all LRU pages, active, inactive and
1071 * unevictable; only give shrink_page_list evictable pages.
1073 if (PageUnevictable(page
))
1079 * To minimise LRU disruption, the caller can indicate that it only
1080 * wants to isolate pages it will be able to operate on without
1081 * blocking - clean pages for the most part.
1083 * ISOLATE_CLEAN means that only clean pages should be isolated. This
1084 * is used by reclaim when it is cannot write to backing storage
1086 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1087 * that it is possible to migrate without blocking
1089 if (mode
& (ISOLATE_CLEAN
|ISOLATE_ASYNC_MIGRATE
)) {
1090 /* All the caller can do on PageWriteback is block */
1091 if (PageWriteback(page
))
1094 if (PageDirty(page
)) {
1095 struct address_space
*mapping
;
1097 /* ISOLATE_CLEAN means only clean pages */
1098 if (mode
& ISOLATE_CLEAN
)
1102 * Only pages without mappings or that have a
1103 * ->migratepage callback are possible to migrate
1106 mapping
= page_mapping(page
);
1107 if (mapping
&& !mapping
->a_ops
->migratepage
)
1112 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1115 if (likely(get_page_unless_zero(page
))) {
1117 * Be careful not to clear PageLRU until after we're
1118 * sure the page is not being freed elsewhere -- the
1119 * page release code relies on it.
1129 * zone->lru_lock is heavily contended. Some of the functions that
1130 * shrink the lists perform better by taking out a batch of pages
1131 * and working on them outside the LRU lock.
1133 * For pagecache intensive workloads, this function is the hottest
1134 * spot in the kernel (apart from copy_*_user functions).
1136 * Appropriate locks must be held before calling this function.
1138 * @nr_to_scan: The number of pages to look through on the list.
1139 * @src: The LRU list to pull pages off.
1140 * @dst: The temp list to put pages on to.
1141 * @scanned: The number of pages that were scanned.
1142 * @order: The caller's attempted allocation order
1143 * @mode: One of the LRU isolation modes
1144 * @file: True [1] if isolating file [!anon] pages
1146 * returns how many pages were moved onto *@dst.
1148 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1149 struct list_head
*src
, struct list_head
*dst
,
1150 unsigned long *scanned
, int order
, isolate_mode_t mode
,
1153 unsigned long nr_taken
= 0;
1154 unsigned long nr_lumpy_taken
= 0;
1155 unsigned long nr_lumpy_dirty
= 0;
1156 unsigned long nr_lumpy_failed
= 0;
1159 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
1162 unsigned long end_pfn
;
1163 unsigned long page_pfn
;
1166 page
= lru_to_page(src
);
1167 prefetchw_prev_lru_page(page
, src
, flags
);
1169 VM_BUG_ON(!PageLRU(page
));
1171 switch (__isolate_lru_page(page
, mode
, file
)) {
1173 mem_cgroup_lru_del(page
);
1174 list_move(&page
->lru
, dst
);
1175 nr_taken
+= hpage_nr_pages(page
);
1179 /* else it is being freed elsewhere */
1180 list_move(&page
->lru
, src
);
1191 * Attempt to take all pages in the order aligned region
1192 * surrounding the tag page. Only take those pages of
1193 * the same active state as that tag page. We may safely
1194 * round the target page pfn down to the requested order
1195 * as the mem_map is guaranteed valid out to MAX_ORDER,
1196 * where that page is in a different zone we will detect
1197 * it from its zone id and abort this block scan.
1199 zone_id
= page_zone_id(page
);
1200 page_pfn
= page_to_pfn(page
);
1201 pfn
= page_pfn
& ~((1 << order
) - 1);
1202 end_pfn
= pfn
+ (1 << order
);
1203 for (; pfn
< end_pfn
; pfn
++) {
1204 struct page
*cursor_page
;
1206 /* The target page is in the block, ignore it. */
1207 if (unlikely(pfn
== page_pfn
))
1210 /* Avoid holes within the zone. */
1211 if (unlikely(!pfn_valid_within(pfn
)))
1214 cursor_page
= pfn_to_page(pfn
);
1216 /* Check that we have not crossed a zone boundary. */
1217 if (unlikely(page_zone_id(cursor_page
) != zone_id
))
1221 * If we don't have enough swap space, reclaiming of
1222 * anon page which don't already have a swap slot is
1225 if (nr_swap_pages
<= 0 && PageSwapBacked(cursor_page
) &&
1226 !PageSwapCache(cursor_page
))
1229 if (__isolate_lru_page(cursor_page
, mode
, file
) == 0) {
1230 unsigned int isolated_pages
;
1232 mem_cgroup_lru_del(cursor_page
);
1233 list_move(&cursor_page
->lru
, dst
);
1234 isolated_pages
= hpage_nr_pages(cursor_page
);
1235 nr_taken
+= isolated_pages
;
1236 nr_lumpy_taken
+= isolated_pages
;
1237 if (PageDirty(cursor_page
))
1238 nr_lumpy_dirty
+= isolated_pages
;
1240 pfn
+= isolated_pages
- 1;
1243 * Check if the page is freed already.
1245 * We can't use page_count() as that
1246 * requires compound_head and we don't
1247 * have a pin on the page here. If a
1248 * page is tail, we may or may not
1249 * have isolated the head, so assume
1250 * it's not free, it'd be tricky to
1251 * track the head status without a
1254 if (!PageTail(cursor_page
) &&
1255 !atomic_read(&cursor_page
->_count
))
1261 /* If we break out of the loop above, lumpy reclaim failed */
1268 trace_mm_vmscan_lru_isolate(order
,
1271 nr_lumpy_taken
, nr_lumpy_dirty
, nr_lumpy_failed
,
1276 static unsigned long isolate_pages(unsigned long nr
, struct mem_cgroup_zone
*mz
,
1277 struct list_head
*dst
,
1278 unsigned long *scanned
, int order
,
1279 isolate_mode_t mode
, int active
, int file
)
1281 struct lruvec
*lruvec
;
1284 lruvec
= mem_cgroup_zone_lruvec(mz
->zone
, mz
->mem_cgroup
);
1289 return isolate_lru_pages(nr
, &lruvec
->lists
[lru
], dst
,
1290 scanned
, order
, mode
, file
);
1294 * clear_active_flags() is a helper for shrink_active_list(), clearing
1295 * any active bits from the pages in the list.
1297 static unsigned long clear_active_flags(struct list_head
*page_list
,
1298 unsigned int *count
)
1304 list_for_each_entry(page
, page_list
, lru
) {
1305 int numpages
= hpage_nr_pages(page
);
1306 lru
= page_lru_base_type(page
);
1307 if (PageActive(page
)) {
1309 ClearPageActive(page
);
1310 nr_active
+= numpages
;
1313 count
[lru
] += numpages
;
1320 * isolate_lru_page - tries to isolate a page from its LRU list
1321 * @page: page to isolate from its LRU list
1323 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1324 * vmstat statistic corresponding to whatever LRU list the page was on.
1326 * Returns 0 if the page was removed from an LRU list.
1327 * Returns -EBUSY if the page was not on an LRU list.
1329 * The returned page will have PageLRU() cleared. If it was found on
1330 * the active list, it will have PageActive set. If it was found on
1331 * the unevictable list, it will have the PageUnevictable bit set. That flag
1332 * may need to be cleared by the caller before letting the page go.
1334 * The vmstat statistic corresponding to the list on which the page was
1335 * found will be decremented.
1338 * (1) Must be called with an elevated refcount on the page. This is a
1339 * fundamentnal difference from isolate_lru_pages (which is called
1340 * without a stable reference).
1341 * (2) the lru_lock must not be held.
1342 * (3) interrupts must be enabled.
1344 int isolate_lru_page(struct page
*page
)
1348 VM_BUG_ON(!page_count(page
));
1350 if (PageLRU(page
)) {
1351 struct zone
*zone
= page_zone(page
);
1353 spin_lock_irq(&zone
->lru_lock
);
1354 if (PageLRU(page
)) {
1355 int lru
= page_lru(page
);
1360 del_page_from_lru_list(zone
, page
, lru
);
1362 spin_unlock_irq(&zone
->lru_lock
);
1368 * Are there way too many processes in the direct reclaim path already?
1370 static int too_many_isolated(struct zone
*zone
, int file
,
1371 struct scan_control
*sc
)
1373 unsigned long inactive
, isolated
;
1375 if (current_is_kswapd())
1378 if (!global_reclaim(sc
))
1382 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1383 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1385 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1386 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1389 return isolated
> inactive
;
1393 * TODO: Try merging with migrations version of putback_lru_pages
1395 static noinline_for_stack
void
1396 putback_lru_pages(struct mem_cgroup_zone
*mz
, struct scan_control
*sc
,
1397 unsigned long nr_anon
, unsigned long nr_file
,
1398 struct list_head
*page_list
)
1401 struct pagevec pvec
;
1402 struct zone
*zone
= mz
->zone
;
1403 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(mz
);
1405 pagevec_init(&pvec
, 1);
1408 * Put back any unfreeable pages.
1410 spin_lock(&zone
->lru_lock
);
1411 while (!list_empty(page_list
)) {
1413 page
= lru_to_page(page_list
);
1414 VM_BUG_ON(PageLRU(page
));
1415 list_del(&page
->lru
);
1416 if (unlikely(!page_evictable(page
, NULL
))) {
1417 spin_unlock_irq(&zone
->lru_lock
);
1418 putback_lru_page(page
);
1419 spin_lock_irq(&zone
->lru_lock
);
1423 lru
= page_lru(page
);
1424 add_page_to_lru_list(zone
, page
, lru
);
1425 if (is_active_lru(lru
)) {
1426 int file
= is_file_lru(lru
);
1427 int numpages
= hpage_nr_pages(page
);
1428 reclaim_stat
->recent_rotated
[file
] += numpages
;
1430 if (!pagevec_add(&pvec
, page
)) {
1431 spin_unlock_irq(&zone
->lru_lock
);
1432 __pagevec_release(&pvec
);
1433 spin_lock_irq(&zone
->lru_lock
);
1436 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, -nr_anon
);
1437 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -nr_file
);
1439 spin_unlock_irq(&zone
->lru_lock
);
1440 pagevec_release(&pvec
);
1443 static noinline_for_stack
void
1444 update_isolated_counts(struct mem_cgroup_zone
*mz
,
1445 struct scan_control
*sc
,
1446 unsigned long *nr_anon
,
1447 unsigned long *nr_file
,
1448 struct list_head
*isolated_list
)
1450 unsigned long nr_active
;
1451 struct zone
*zone
= mz
->zone
;
1452 unsigned int count
[NR_LRU_LISTS
] = { 0, };
1453 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(mz
);
1455 nr_active
= clear_active_flags(isolated_list
, count
);
1456 __count_vm_events(PGDEACTIVATE
, nr_active
);
1458 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
1459 -count
[LRU_ACTIVE_FILE
]);
1460 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
1461 -count
[LRU_INACTIVE_FILE
]);
1462 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
1463 -count
[LRU_ACTIVE_ANON
]);
1464 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
1465 -count
[LRU_INACTIVE_ANON
]);
1467 *nr_anon
= count
[LRU_ACTIVE_ANON
] + count
[LRU_INACTIVE_ANON
];
1468 *nr_file
= count
[LRU_ACTIVE_FILE
] + count
[LRU_INACTIVE_FILE
];
1469 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, *nr_anon
);
1470 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, *nr_file
);
1472 reclaim_stat
->recent_scanned
[0] += *nr_anon
;
1473 reclaim_stat
->recent_scanned
[1] += *nr_file
;
1477 * Returns true if a direct reclaim should wait on pages under writeback.
1479 * If we are direct reclaiming for contiguous pages and we do not reclaim
1480 * everything in the list, try again and wait for writeback IO to complete.
1481 * This will stall high-order allocations noticeably. Only do that when really
1482 * need to free the pages under high memory pressure.
1484 static inline bool should_reclaim_stall(unsigned long nr_taken
,
1485 unsigned long nr_freed
,
1487 struct scan_control
*sc
)
1489 int lumpy_stall_priority
;
1491 /* kswapd should not stall on sync IO */
1492 if (current_is_kswapd())
1495 /* Only stall on lumpy reclaim */
1496 if (sc
->reclaim_mode
& RECLAIM_MODE_SINGLE
)
1499 /* If we have reclaimed everything on the isolated list, no stall */
1500 if (nr_freed
== nr_taken
)
1504 * For high-order allocations, there are two stall thresholds.
1505 * High-cost allocations stall immediately where as lower
1506 * order allocations such as stacks require the scanning
1507 * priority to be much higher before stalling.
1509 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
1510 lumpy_stall_priority
= DEF_PRIORITY
;
1512 lumpy_stall_priority
= DEF_PRIORITY
/ 3;
1514 return priority
<= lumpy_stall_priority
;
1518 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1519 * of reclaimed pages
1521 static noinline_for_stack
unsigned long
1522 shrink_inactive_list(unsigned long nr_to_scan
, struct mem_cgroup_zone
*mz
,
1523 struct scan_control
*sc
, int priority
, int file
)
1525 LIST_HEAD(page_list
);
1526 unsigned long nr_scanned
;
1527 unsigned long nr_reclaimed
= 0;
1528 unsigned long nr_taken
;
1529 unsigned long nr_anon
;
1530 unsigned long nr_file
;
1531 unsigned long nr_dirty
= 0;
1532 unsigned long nr_writeback
= 0;
1533 isolate_mode_t reclaim_mode
= ISOLATE_INACTIVE
;
1534 struct zone
*zone
= mz
->zone
;
1536 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1537 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1539 /* We are about to die and free our memory. Return now. */
1540 if (fatal_signal_pending(current
))
1541 return SWAP_CLUSTER_MAX
;
1544 set_reclaim_mode(priority
, sc
, false);
1545 if (sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
)
1546 reclaim_mode
|= ISOLATE_ACTIVE
;
1551 reclaim_mode
|= ISOLATE_UNMAPPED
;
1552 if (!sc
->may_writepage
)
1553 reclaim_mode
|= ISOLATE_CLEAN
;
1555 spin_lock_irq(&zone
->lru_lock
);
1557 nr_taken
= isolate_pages(nr_to_scan
, mz
, &page_list
,
1558 &nr_scanned
, sc
->order
,
1559 reclaim_mode
, 0, file
);
1560 if (global_reclaim(sc
)) {
1561 zone
->pages_scanned
+= nr_scanned
;
1562 if (current_is_kswapd())
1563 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
,
1566 __count_zone_vm_events(PGSCAN_DIRECT
, zone
,
1570 if (nr_taken
== 0) {
1571 spin_unlock_irq(&zone
->lru_lock
);
1575 update_isolated_counts(mz
, sc
, &nr_anon
, &nr_file
, &page_list
);
1577 spin_unlock_irq(&zone
->lru_lock
);
1579 nr_reclaimed
= shrink_page_list(&page_list
, mz
, sc
, priority
,
1580 &nr_dirty
, &nr_writeback
);
1582 /* Check if we should syncronously wait for writeback */
1583 if (should_reclaim_stall(nr_taken
, nr_reclaimed
, priority
, sc
)) {
1584 set_reclaim_mode(priority
, sc
, true);
1585 nr_reclaimed
+= shrink_page_list(&page_list
, mz
, sc
,
1586 priority
, &nr_dirty
, &nr_writeback
);
1589 local_irq_disable();
1590 if (current_is_kswapd())
1591 __count_vm_events(KSWAPD_STEAL
, nr_reclaimed
);
1592 __count_zone_vm_events(PGSTEAL
, zone
, nr_reclaimed
);
1594 putback_lru_pages(mz
, sc
, nr_anon
, nr_file
, &page_list
);
1597 * If reclaim is isolating dirty pages under writeback, it implies
1598 * that the long-lived page allocation rate is exceeding the page
1599 * laundering rate. Either the global limits are not being effective
1600 * at throttling processes due to the page distribution throughout
1601 * zones or there is heavy usage of a slow backing device. The
1602 * only option is to throttle from reclaim context which is not ideal
1603 * as there is no guarantee the dirtying process is throttled in the
1604 * same way balance_dirty_pages() manages.
1606 * This scales the number of dirty pages that must be under writeback
1607 * before throttling depending on priority. It is a simple backoff
1608 * function that has the most effect in the range DEF_PRIORITY to
1609 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1610 * in trouble and reclaim is considered to be in trouble.
1612 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1613 * DEF_PRIORITY-1 50% must be PageWriteback
1614 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1616 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1617 * isolated page is PageWriteback
1619 if (nr_writeback
&& nr_writeback
>= (nr_taken
>> (DEF_PRIORITY
-priority
)))
1620 wait_iff_congested(zone
, BLK_RW_ASYNC
, HZ
/10);
1622 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1624 nr_scanned
, nr_reclaimed
,
1626 trace_shrink_flags(file
, sc
->reclaim_mode
));
1627 return nr_reclaimed
;
1631 * This moves pages from the active list to the inactive list.
1633 * We move them the other way if the page is referenced by one or more
1634 * processes, from rmap.
1636 * If the pages are mostly unmapped, the processing is fast and it is
1637 * appropriate to hold zone->lru_lock across the whole operation. But if
1638 * the pages are mapped, the processing is slow (page_referenced()) so we
1639 * should drop zone->lru_lock around each page. It's impossible to balance
1640 * this, so instead we remove the pages from the LRU while processing them.
1641 * It is safe to rely on PG_active against the non-LRU pages in here because
1642 * nobody will play with that bit on a non-LRU page.
1644 * The downside is that we have to touch page->_count against each page.
1645 * But we had to alter page->flags anyway.
1648 static void move_active_pages_to_lru(struct zone
*zone
,
1649 struct list_head
*list
,
1652 unsigned long pgmoved
= 0;
1653 struct pagevec pvec
;
1656 pagevec_init(&pvec
, 1);
1658 while (!list_empty(list
)) {
1659 struct lruvec
*lruvec
;
1661 page
= lru_to_page(list
);
1663 VM_BUG_ON(PageLRU(page
));
1666 lruvec
= mem_cgroup_lru_add_list(zone
, page
, lru
);
1667 list_move(&page
->lru
, &lruvec
->lists
[lru
]);
1668 pgmoved
+= hpage_nr_pages(page
);
1670 if (!pagevec_add(&pvec
, page
) || list_empty(list
)) {
1671 spin_unlock_irq(&zone
->lru_lock
);
1672 if (buffer_heads_over_limit
)
1673 pagevec_strip(&pvec
);
1674 __pagevec_release(&pvec
);
1675 spin_lock_irq(&zone
->lru_lock
);
1678 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1679 if (!is_active_lru(lru
))
1680 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1683 static void shrink_active_list(unsigned long nr_pages
,
1684 struct mem_cgroup_zone
*mz
,
1685 struct scan_control
*sc
,
1686 int priority
, int file
)
1688 unsigned long nr_taken
;
1689 unsigned long pgscanned
;
1690 unsigned long vm_flags
;
1691 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1692 LIST_HEAD(l_active
);
1693 LIST_HEAD(l_inactive
);
1695 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(mz
);
1696 unsigned long nr_rotated
= 0;
1697 isolate_mode_t reclaim_mode
= ISOLATE_ACTIVE
;
1698 struct zone
*zone
= mz
->zone
;
1703 reclaim_mode
|= ISOLATE_UNMAPPED
;
1704 if (!sc
->may_writepage
)
1705 reclaim_mode
|= ISOLATE_CLEAN
;
1707 spin_lock_irq(&zone
->lru_lock
);
1709 nr_taken
= isolate_pages(nr_pages
, mz
, &l_hold
,
1710 &pgscanned
, sc
->order
,
1711 reclaim_mode
, 1, file
);
1713 if (global_reclaim(sc
))
1714 zone
->pages_scanned
+= pgscanned
;
1716 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1718 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1720 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -nr_taken
);
1722 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -nr_taken
);
1723 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1724 spin_unlock_irq(&zone
->lru_lock
);
1726 while (!list_empty(&l_hold
)) {
1728 page
= lru_to_page(&l_hold
);
1729 list_del(&page
->lru
);
1731 if (unlikely(!page_evictable(page
, NULL
))) {
1732 putback_lru_page(page
);
1736 if (page_referenced(page
, 0, mz
->mem_cgroup
, &vm_flags
)) {
1737 nr_rotated
+= hpage_nr_pages(page
);
1739 * Identify referenced, file-backed active pages and
1740 * give them one more trip around the active list. So
1741 * that executable code get better chances to stay in
1742 * memory under moderate memory pressure. Anon pages
1743 * are not likely to be evicted by use-once streaming
1744 * IO, plus JVM can create lots of anon VM_EXEC pages,
1745 * so we ignore them here.
1747 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1748 list_add(&page
->lru
, &l_active
);
1753 ClearPageActive(page
); /* we are de-activating */
1754 list_add(&page
->lru
, &l_inactive
);
1758 * Move pages back to the lru list.
1760 spin_lock_irq(&zone
->lru_lock
);
1762 * Count referenced pages from currently used mappings as rotated,
1763 * even though only some of them are actually re-activated. This
1764 * helps balance scan pressure between file and anonymous pages in
1767 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1769 move_active_pages_to_lru(zone
, &l_active
,
1770 LRU_ACTIVE
+ file
* LRU_FILE
);
1771 move_active_pages_to_lru(zone
, &l_inactive
,
1772 LRU_BASE
+ file
* LRU_FILE
);
1773 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1774 spin_unlock_irq(&zone
->lru_lock
);
1778 static int inactive_anon_is_low_global(struct zone
*zone
)
1780 unsigned long active
, inactive
;
1782 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1783 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1785 if (inactive
* zone
->inactive_ratio
< active
)
1792 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1793 * @zone: zone to check
1794 * @sc: scan control of this context
1796 * Returns true if the zone does not have enough inactive anon pages,
1797 * meaning some active anon pages need to be deactivated.
1799 static int inactive_anon_is_low(struct mem_cgroup_zone
*mz
)
1802 * If we don't have swap space, anonymous page deactivation
1805 if (!total_swap_pages
)
1808 if (!scanning_global_lru(mz
))
1809 return mem_cgroup_inactive_anon_is_low(mz
->mem_cgroup
,
1812 return inactive_anon_is_low_global(mz
->zone
);
1815 static inline int inactive_anon_is_low(struct mem_cgroup_zone
*mz
)
1821 static int inactive_file_is_low_global(struct zone
*zone
)
1823 unsigned long active
, inactive
;
1825 active
= zone_page_state(zone
, NR_ACTIVE_FILE
);
1826 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1828 return (active
> inactive
);
1832 * inactive_file_is_low - check if file pages need to be deactivated
1833 * @mz: memory cgroup and zone to check
1835 * When the system is doing streaming IO, memory pressure here
1836 * ensures that active file pages get deactivated, until more
1837 * than half of the file pages are on the inactive list.
1839 * Once we get to that situation, protect the system's working
1840 * set from being evicted by disabling active file page aging.
1842 * This uses a different ratio than the anonymous pages, because
1843 * the page cache uses a use-once replacement algorithm.
1845 static int inactive_file_is_low(struct mem_cgroup_zone
*mz
)
1847 if (!scanning_global_lru(mz
))
1848 return mem_cgroup_inactive_file_is_low(mz
->mem_cgroup
,
1851 return inactive_file_is_low_global(mz
->zone
);
1854 static int inactive_list_is_low(struct mem_cgroup_zone
*mz
, int file
)
1857 return inactive_file_is_low(mz
);
1859 return inactive_anon_is_low(mz
);
1862 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1863 struct mem_cgroup_zone
*mz
,
1864 struct scan_control
*sc
, int priority
)
1866 int file
= is_file_lru(lru
);
1868 if (is_active_lru(lru
)) {
1869 if (inactive_list_is_low(mz
, file
))
1870 shrink_active_list(nr_to_scan
, mz
, sc
, priority
, file
);
1874 return shrink_inactive_list(nr_to_scan
, mz
, sc
, priority
, file
);
1877 static int vmscan_swappiness(struct mem_cgroup_zone
*mz
,
1878 struct scan_control
*sc
)
1880 if (global_reclaim(sc
))
1881 return vm_swappiness
;
1882 return mem_cgroup_swappiness(mz
->mem_cgroup
);
1886 * Determine how aggressively the anon and file LRU lists should be
1887 * scanned. The relative value of each set of LRU lists is determined
1888 * by looking at the fraction of the pages scanned we did rotate back
1889 * onto the active list instead of evict.
1891 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1893 static void get_scan_count(struct mem_cgroup_zone
*mz
, struct scan_control
*sc
,
1894 unsigned long *nr
, int priority
)
1896 unsigned long anon
, file
, free
;
1897 unsigned long anon_prio
, file_prio
;
1898 unsigned long ap
, fp
;
1899 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(mz
);
1900 u64 fraction
[2], denominator
;
1903 bool force_scan
= false;
1906 * If the zone or memcg is small, nr[l] can be 0. This
1907 * results in no scanning on this priority and a potential
1908 * priority drop. Global direct reclaim can go to the next
1909 * zone and tends to have no problems. Global kswapd is for
1910 * zone balancing and it needs to scan a minimum amount. When
1911 * reclaiming for a memcg, a priority drop can cause high
1912 * latencies, so it's better to scan a minimum amount there as
1915 if (current_is_kswapd() && mz
->zone
->all_unreclaimable
)
1917 if (!global_reclaim(sc
))
1920 /* If we have no swap space, do not bother scanning anon pages. */
1921 if (!sc
->may_swap
|| (nr_swap_pages
<= 0)) {
1929 anon
= zone_nr_lru_pages(mz
, LRU_ACTIVE_ANON
) +
1930 zone_nr_lru_pages(mz
, LRU_INACTIVE_ANON
);
1931 file
= zone_nr_lru_pages(mz
, LRU_ACTIVE_FILE
) +
1932 zone_nr_lru_pages(mz
, LRU_INACTIVE_FILE
);
1934 if (global_reclaim(sc
)) {
1935 free
= zone_page_state(mz
->zone
, NR_FREE_PAGES
);
1936 /* If we have very few page cache pages,
1937 force-scan anon pages. */
1938 if (unlikely(file
+ free
<= high_wmark_pages(mz
->zone
))) {
1947 * With swappiness at 100, anonymous and file have the same priority.
1948 * This scanning priority is essentially the inverse of IO cost.
1950 anon_prio
= vmscan_swappiness(mz
, sc
);
1951 file_prio
= 200 - vmscan_swappiness(mz
, sc
);
1954 * OK, so we have swap space and a fair amount of page cache
1955 * pages. We use the recently rotated / recently scanned
1956 * ratios to determine how valuable each cache is.
1958 * Because workloads change over time (and to avoid overflow)
1959 * we keep these statistics as a floating average, which ends
1960 * up weighing recent references more than old ones.
1962 * anon in [0], file in [1]
1964 spin_lock_irq(&mz
->zone
->lru_lock
);
1965 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1966 reclaim_stat
->recent_scanned
[0] /= 2;
1967 reclaim_stat
->recent_rotated
[0] /= 2;
1970 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1971 reclaim_stat
->recent_scanned
[1] /= 2;
1972 reclaim_stat
->recent_rotated
[1] /= 2;
1976 * The amount of pressure on anon vs file pages is inversely
1977 * proportional to the fraction of recently scanned pages on
1978 * each list that were recently referenced and in active use.
1980 ap
= (anon_prio
+ 1) * (reclaim_stat
->recent_scanned
[0] + 1);
1981 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1983 fp
= (file_prio
+ 1) * (reclaim_stat
->recent_scanned
[1] + 1);
1984 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1985 spin_unlock_irq(&mz
->zone
->lru_lock
);
1989 denominator
= ap
+ fp
+ 1;
1991 for_each_evictable_lru(l
) {
1992 int file
= is_file_lru(l
);
1995 scan
= zone_nr_lru_pages(mz
, l
);
1996 if (priority
|| noswap
) {
1998 if (!scan
&& force_scan
)
1999 scan
= SWAP_CLUSTER_MAX
;
2000 scan
= div64_u64(scan
* fraction
[file
], denominator
);
2007 * Reclaim/compaction depends on a number of pages being freed. To avoid
2008 * disruption to the system, a small number of order-0 pages continue to be
2009 * rotated and reclaimed in the normal fashion. However, by the time we get
2010 * back to the allocator and call try_to_compact_zone(), we ensure that
2011 * there are enough free pages for it to be likely successful
2013 static inline bool should_continue_reclaim(struct mem_cgroup_zone
*mz
,
2014 unsigned long nr_reclaimed
,
2015 unsigned long nr_scanned
,
2016 struct scan_control
*sc
)
2018 unsigned long pages_for_compaction
;
2019 unsigned long inactive_lru_pages
;
2021 /* If not in reclaim/compaction mode, stop */
2022 if (!(sc
->reclaim_mode
& RECLAIM_MODE_COMPACTION
))
2025 /* Consider stopping depending on scan and reclaim activity */
2026 if (sc
->gfp_mask
& __GFP_REPEAT
) {
2028 * For __GFP_REPEAT allocations, stop reclaiming if the
2029 * full LRU list has been scanned and we are still failing
2030 * to reclaim pages. This full LRU scan is potentially
2031 * expensive but a __GFP_REPEAT caller really wants to succeed
2033 if (!nr_reclaimed
&& !nr_scanned
)
2037 * For non-__GFP_REPEAT allocations which can presumably
2038 * fail without consequence, stop if we failed to reclaim
2039 * any pages from the last SWAP_CLUSTER_MAX number of
2040 * pages that were scanned. This will return to the
2041 * caller faster at the risk reclaim/compaction and
2042 * the resulting allocation attempt fails
2049 * If we have not reclaimed enough pages for compaction and the
2050 * inactive lists are large enough, continue reclaiming
2052 pages_for_compaction
= (2UL << sc
->order
);
2053 inactive_lru_pages
= zone_nr_lru_pages(mz
, LRU_INACTIVE_FILE
);
2054 if (nr_swap_pages
> 0)
2055 inactive_lru_pages
+= zone_nr_lru_pages(mz
, LRU_INACTIVE_ANON
);
2056 if (sc
->nr_reclaimed
< pages_for_compaction
&&
2057 inactive_lru_pages
> pages_for_compaction
)
2060 /* If compaction would go ahead or the allocation would succeed, stop */
2061 switch (compaction_suitable(mz
->zone
, sc
->order
)) {
2062 case COMPACT_PARTIAL
:
2063 case COMPACT_CONTINUE
:
2071 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2073 static void shrink_mem_cgroup_zone(int priority
, struct mem_cgroup_zone
*mz
,
2074 struct scan_control
*sc
)
2076 unsigned long nr
[NR_LRU_LISTS
];
2077 unsigned long nr_to_scan
;
2079 unsigned long nr_reclaimed
, nr_scanned
;
2080 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2081 struct blk_plug plug
;
2085 nr_scanned
= sc
->nr_scanned
;
2086 get_scan_count(mz
, sc
, nr
, priority
);
2088 blk_start_plug(&plug
);
2089 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2090 nr
[LRU_INACTIVE_FILE
]) {
2091 for_each_evictable_lru(l
) {
2093 nr_to_scan
= min_t(unsigned long,
2094 nr
[l
], SWAP_CLUSTER_MAX
);
2095 nr
[l
] -= nr_to_scan
;
2097 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
2102 * On large memory systems, scan >> priority can become
2103 * really large. This is fine for the starting priority;
2104 * we want to put equal scanning pressure on each zone.
2105 * However, if the VM has a harder time of freeing pages,
2106 * with multiple processes reclaiming pages, the total
2107 * freeing target can get unreasonably large.
2109 if (nr_reclaimed
>= nr_to_reclaim
&& priority
< DEF_PRIORITY
)
2112 blk_finish_plug(&plug
);
2113 sc
->nr_reclaimed
+= nr_reclaimed
;
2116 * Even if we did not try to evict anon pages at all, we want to
2117 * rebalance the anon lru active/inactive ratio.
2119 if (inactive_anon_is_low(mz
))
2120 shrink_active_list(SWAP_CLUSTER_MAX
, mz
, sc
, priority
, 0);
2122 /* reclaim/compaction might need reclaim to continue */
2123 if (should_continue_reclaim(mz
, nr_reclaimed
,
2124 sc
->nr_scanned
- nr_scanned
, sc
))
2127 throttle_vm_writeout(sc
->gfp_mask
);
2130 static void shrink_zone(int priority
, struct zone
*zone
,
2131 struct scan_control
*sc
)
2133 struct mem_cgroup
*root
= sc
->target_mem_cgroup
;
2134 struct mem_cgroup_reclaim_cookie reclaim
= {
2136 .priority
= priority
,
2138 struct mem_cgroup
*memcg
;
2140 memcg
= mem_cgroup_iter(root
, NULL
, &reclaim
);
2142 struct mem_cgroup_zone mz
= {
2143 .mem_cgroup
= memcg
,
2147 shrink_mem_cgroup_zone(priority
, &mz
, sc
);
2149 * Limit reclaim has historically picked one memcg and
2150 * scanned it with decreasing priority levels until
2151 * nr_to_reclaim had been reclaimed. This priority
2152 * cycle is thus over after a single memcg.
2154 * Direct reclaim and kswapd, on the other hand, have
2155 * to scan all memory cgroups to fulfill the overall
2156 * scan target for the zone.
2158 if (!global_reclaim(sc
)) {
2159 mem_cgroup_iter_break(root
, memcg
);
2162 memcg
= mem_cgroup_iter(root
, memcg
, &reclaim
);
2166 /* Returns true if compaction should go ahead for a high-order request */
2167 static inline bool compaction_ready(struct zone
*zone
, struct scan_control
*sc
)
2169 unsigned long balance_gap
, watermark
;
2172 /* Do not consider compaction for orders reclaim is meant to satisfy */
2173 if (sc
->order
<= PAGE_ALLOC_COSTLY_ORDER
)
2177 * Compaction takes time to run and there are potentially other
2178 * callers using the pages just freed. Continue reclaiming until
2179 * there is a buffer of free pages available to give compaction
2180 * a reasonable chance of completing and allocating the page
2182 balance_gap
= min(low_wmark_pages(zone
),
2183 (zone
->present_pages
+ KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2184 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2185 watermark
= high_wmark_pages(zone
) + balance_gap
+ (2UL << sc
->order
);
2186 watermark_ok
= zone_watermark_ok_safe(zone
, 0, watermark
, 0, 0);
2189 * If compaction is deferred, reclaim up to a point where
2190 * compaction will have a chance of success when re-enabled
2192 if (compaction_deferred(zone
))
2193 return watermark_ok
;
2195 /* If compaction is not ready to start, keep reclaiming */
2196 if (!compaction_suitable(zone
, sc
->order
))
2199 return watermark_ok
;
2203 * This is the direct reclaim path, for page-allocating processes. We only
2204 * try to reclaim pages from zones which will satisfy the caller's allocation
2207 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2209 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2211 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2212 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2213 * zone defense algorithm.
2215 * If a zone is deemed to be full of pinned pages then just give it a light
2216 * scan then give up on it.
2218 * This function returns true if a zone is being reclaimed for a costly
2219 * high-order allocation and compaction is ready to begin. This indicates to
2220 * the caller that it should retry the allocation or fail.
2222 static bool shrink_zones(int priority
, struct zonelist
*zonelist
,
2223 struct scan_control
*sc
)
2227 unsigned long nr_soft_reclaimed
;
2228 unsigned long nr_soft_scanned
;
2229 bool should_abort_reclaim
= false;
2231 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2232 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2233 if (!populated_zone(zone
))
2236 * Take care memory controller reclaiming has small influence
2239 if (global_reclaim(sc
)) {
2240 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2242 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2243 continue; /* Let kswapd poll it */
2244 if (COMPACTION_BUILD
) {
2246 * If we already have plenty of memory free for
2247 * compaction in this zone, don't free any more.
2248 * Even though compaction is invoked for any
2249 * non-zero order, only frequent costly order
2250 * reclamation is disruptive enough to become a
2251 * noticable problem, like transparent huge page
2254 if (compaction_ready(zone
, sc
)) {
2255 should_abort_reclaim
= true;
2260 * This steals pages from memory cgroups over softlimit
2261 * and returns the number of reclaimed pages and
2262 * scanned pages. This works for global memory pressure
2263 * and balancing, not for a memcg's limit.
2265 nr_soft_scanned
= 0;
2266 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2267 sc
->order
, sc
->gfp_mask
,
2269 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2270 sc
->nr_scanned
+= nr_soft_scanned
;
2271 /* need some check for avoid more shrink_zone() */
2274 shrink_zone(priority
, zone
, sc
);
2277 return should_abort_reclaim
;
2280 static bool zone_reclaimable(struct zone
*zone
)
2282 return zone
->pages_scanned
< zone_reclaimable_pages(zone
) * 6;
2285 /* All zones in zonelist are unreclaimable? */
2286 static bool all_unreclaimable(struct zonelist
*zonelist
,
2287 struct scan_control
*sc
)
2292 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2293 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2294 if (!populated_zone(zone
))
2296 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2298 if (!zone
->all_unreclaimable
)
2306 * This is the main entry point to direct page reclaim.
2308 * If a full scan of the inactive list fails to free enough memory then we
2309 * are "out of memory" and something needs to be killed.
2311 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2312 * high - the zone may be full of dirty or under-writeback pages, which this
2313 * caller can't do much about. We kick the writeback threads and take explicit
2314 * naps in the hope that some of these pages can be written. But if the
2315 * allocating task holds filesystem locks which prevent writeout this might not
2316 * work, and the allocation attempt will fail.
2318 * returns: 0, if no pages reclaimed
2319 * else, the number of pages reclaimed
2321 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2322 struct scan_control
*sc
,
2323 struct shrink_control
*shrink
)
2326 unsigned long total_scanned
= 0;
2327 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2330 unsigned long writeback_threshold
;
2331 bool should_abort_reclaim
;
2334 delayacct_freepages_start();
2336 if (global_reclaim(sc
))
2337 count_vm_event(ALLOCSTALL
);
2339 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2342 disable_swap_token(sc
->target_mem_cgroup
);
2343 should_abort_reclaim
= shrink_zones(priority
, zonelist
, sc
);
2344 if (should_abort_reclaim
)
2348 * Don't shrink slabs when reclaiming memory from
2349 * over limit cgroups
2351 if (global_reclaim(sc
)) {
2352 unsigned long lru_pages
= 0;
2353 for_each_zone_zonelist(zone
, z
, zonelist
,
2354 gfp_zone(sc
->gfp_mask
)) {
2355 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2358 lru_pages
+= zone_reclaimable_pages(zone
);
2361 shrink_slab(shrink
, sc
->nr_scanned
, lru_pages
);
2362 if (reclaim_state
) {
2363 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2364 reclaim_state
->reclaimed_slab
= 0;
2367 total_scanned
+= sc
->nr_scanned
;
2368 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2372 * Try to write back as many pages as we just scanned. This
2373 * tends to cause slow streaming writers to write data to the
2374 * disk smoothly, at the dirtying rate, which is nice. But
2375 * that's undesirable in laptop mode, where we *want* lumpy
2376 * writeout. So in laptop mode, write out the whole world.
2378 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2379 if (total_scanned
> writeback_threshold
) {
2380 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
,
2381 WB_REASON_TRY_TO_FREE_PAGES
);
2382 sc
->may_writepage
= 1;
2385 /* Take a nap, wait for some writeback to complete */
2386 if (!sc
->hibernation_mode
&& sc
->nr_scanned
&&
2387 priority
< DEF_PRIORITY
- 2) {
2388 struct zone
*preferred_zone
;
2390 first_zones_zonelist(zonelist
, gfp_zone(sc
->gfp_mask
),
2391 &cpuset_current_mems_allowed
,
2393 wait_iff_congested(preferred_zone
, BLK_RW_ASYNC
, HZ
/10);
2398 delayacct_freepages_end();
2401 if (sc
->nr_reclaimed
)
2402 return sc
->nr_reclaimed
;
2405 * As hibernation is going on, kswapd is freezed so that it can't mark
2406 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2409 if (oom_killer_disabled
)
2412 /* Aborting reclaim to try compaction? don't OOM, then */
2413 if (should_abort_reclaim
)
2416 /* top priority shrink_zones still had more to do? don't OOM, then */
2417 if (global_reclaim(sc
) && !all_unreclaimable(zonelist
, sc
))
2423 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2424 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2426 unsigned long nr_reclaimed
;
2427 struct scan_control sc
= {
2428 .gfp_mask
= gfp_mask
,
2429 .may_writepage
= !laptop_mode
,
2430 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2434 .target_mem_cgroup
= NULL
,
2435 .nodemask
= nodemask
,
2437 struct shrink_control shrink
= {
2438 .gfp_mask
= sc
.gfp_mask
,
2441 trace_mm_vmscan_direct_reclaim_begin(order
,
2445 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2447 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2449 return nr_reclaimed
;
2452 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2454 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*memcg
,
2455 gfp_t gfp_mask
, bool noswap
,
2457 unsigned long *nr_scanned
)
2459 struct scan_control sc
= {
2461 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2462 .may_writepage
= !laptop_mode
,
2464 .may_swap
= !noswap
,
2466 .target_mem_cgroup
= memcg
,
2468 struct mem_cgroup_zone mz
= {
2469 .mem_cgroup
= memcg
,
2473 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2474 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2476 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2481 * NOTE: Although we can get the priority field, using it
2482 * here is not a good idea, since it limits the pages we can scan.
2483 * if we don't reclaim here, the shrink_zone from balance_pgdat
2484 * will pick up pages from other mem cgroup's as well. We hack
2485 * the priority and make it zero.
2487 shrink_mem_cgroup_zone(0, &mz
, &sc
);
2489 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2491 *nr_scanned
= sc
.nr_scanned
;
2492 return sc
.nr_reclaimed
;
2495 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
2499 struct zonelist
*zonelist
;
2500 unsigned long nr_reclaimed
;
2502 struct scan_control sc
= {
2503 .may_writepage
= !laptop_mode
,
2505 .may_swap
= !noswap
,
2506 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2508 .target_mem_cgroup
= memcg
,
2509 .nodemask
= NULL
, /* we don't care the placement */
2510 .gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2511 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
2513 struct shrink_control shrink
= {
2514 .gfp_mask
= sc
.gfp_mask
,
2518 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2519 * take care of from where we get pages. So the node where we start the
2520 * scan does not need to be the current node.
2522 nid
= mem_cgroup_select_victim_node(memcg
);
2524 zonelist
= NODE_DATA(nid
)->node_zonelists
;
2526 trace_mm_vmscan_memcg_reclaim_begin(0,
2530 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2532 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2534 return nr_reclaimed
;
2538 static void age_active_anon(struct zone
*zone
, struct scan_control
*sc
,
2541 struct mem_cgroup
*memcg
;
2543 if (!total_swap_pages
)
2546 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
2548 struct mem_cgroup_zone mz
= {
2549 .mem_cgroup
= memcg
,
2553 if (inactive_anon_is_low(&mz
))
2554 shrink_active_list(SWAP_CLUSTER_MAX
, &mz
,
2557 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
2562 * pgdat_balanced is used when checking if a node is balanced for high-order
2563 * allocations. Only zones that meet watermarks and are in a zone allowed
2564 * by the callers classzone_idx are added to balanced_pages. The total of
2565 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2566 * for the node to be considered balanced. Forcing all zones to be balanced
2567 * for high orders can cause excessive reclaim when there are imbalanced zones.
2568 * The choice of 25% is due to
2569 * o a 16M DMA zone that is balanced will not balance a zone on any
2570 * reasonable sized machine
2571 * o On all other machines, the top zone must be at least a reasonable
2572 * percentage of the middle zones. For example, on 32-bit x86, highmem
2573 * would need to be at least 256M for it to be balance a whole node.
2574 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2575 * to balance a node on its own. These seemed like reasonable ratios.
2577 static bool pgdat_balanced(pg_data_t
*pgdat
, unsigned long balanced_pages
,
2580 unsigned long present_pages
= 0;
2583 for (i
= 0; i
<= classzone_idx
; i
++)
2584 present_pages
+= pgdat
->node_zones
[i
].present_pages
;
2586 /* A special case here: if zone has no page, we think it's balanced */
2587 return balanced_pages
>= (present_pages
>> 2);
2590 /* is kswapd sleeping prematurely? */
2591 static bool sleeping_prematurely(pg_data_t
*pgdat
, int order
, long remaining
,
2595 unsigned long balanced
= 0;
2596 bool all_zones_ok
= true;
2598 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2602 /* Check the watermark levels */
2603 for (i
= 0; i
<= classzone_idx
; i
++) {
2604 struct zone
*zone
= pgdat
->node_zones
+ i
;
2606 if (!populated_zone(zone
))
2610 * balance_pgdat() skips over all_unreclaimable after
2611 * DEF_PRIORITY. Effectively, it considers them balanced so
2612 * they must be considered balanced here as well if kswapd
2615 if (zone
->all_unreclaimable
) {
2616 balanced
+= zone
->present_pages
;
2620 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
),
2622 all_zones_ok
= false;
2624 balanced
+= zone
->present_pages
;
2628 * For high-order requests, the balanced zones must contain at least
2629 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2633 return !pgdat_balanced(pgdat
, balanced
, classzone_idx
);
2635 return !all_zones_ok
;
2639 * For kswapd, balance_pgdat() will work across all this node's zones until
2640 * they are all at high_wmark_pages(zone).
2642 * Returns the final order kswapd was reclaiming at
2644 * There is special handling here for zones which are full of pinned pages.
2645 * This can happen if the pages are all mlocked, or if they are all used by
2646 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2647 * What we do is to detect the case where all pages in the zone have been
2648 * scanned twice and there has been zero successful reclaim. Mark the zone as
2649 * dead and from now on, only perform a short scan. Basically we're polling
2650 * the zone for when the problem goes away.
2652 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2653 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2654 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2655 * lower zones regardless of the number of free pages in the lower zones. This
2656 * interoperates with the page allocator fallback scheme to ensure that aging
2657 * of pages is balanced across the zones.
2659 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
2663 unsigned long balanced
;
2666 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
2667 unsigned long total_scanned
;
2668 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2669 unsigned long nr_soft_reclaimed
;
2670 unsigned long nr_soft_scanned
;
2671 struct scan_control sc
= {
2672 .gfp_mask
= GFP_KERNEL
,
2676 * kswapd doesn't want to be bailed out while reclaim. because
2677 * we want to put equal scanning pressure on each zone.
2679 .nr_to_reclaim
= ULONG_MAX
,
2681 .target_mem_cgroup
= NULL
,
2683 struct shrink_control shrink
= {
2684 .gfp_mask
= sc
.gfp_mask
,
2688 sc
.nr_reclaimed
= 0;
2689 sc
.may_writepage
= !laptop_mode
;
2690 count_vm_event(PAGEOUTRUN
);
2692 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2693 unsigned long lru_pages
= 0;
2694 int has_under_min_watermark_zone
= 0;
2696 /* The swap token gets in the way of swapout... */
2698 disable_swap_token(NULL
);
2704 * Scan in the highmem->dma direction for the highest
2705 * zone which needs scanning
2707 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
2708 struct zone
*zone
= pgdat
->node_zones
+ i
;
2710 if (!populated_zone(zone
))
2713 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2717 * Do some background aging of the anon list, to give
2718 * pages a chance to be referenced before reclaiming.
2720 age_active_anon(zone
, &sc
, priority
);
2722 if (!zone_watermark_ok_safe(zone
, order
,
2723 high_wmark_pages(zone
), 0, 0)) {
2727 /* If balanced, clear the congested flag */
2728 zone_clear_flag(zone
, ZONE_CONGESTED
);
2734 for (i
= 0; i
<= end_zone
; i
++) {
2735 struct zone
*zone
= pgdat
->node_zones
+ i
;
2737 lru_pages
+= zone_reclaimable_pages(zone
);
2741 * Now scan the zone in the dma->highmem direction, stopping
2742 * at the last zone which needs scanning.
2744 * We do this because the page allocator works in the opposite
2745 * direction. This prevents the page allocator from allocating
2746 * pages behind kswapd's direction of progress, which would
2747 * cause too much scanning of the lower zones.
2749 for (i
= 0; i
<= end_zone
; i
++) {
2750 struct zone
*zone
= pgdat
->node_zones
+ i
;
2752 unsigned long balance_gap
;
2754 if (!populated_zone(zone
))
2757 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2762 nr_soft_scanned
= 0;
2764 * Call soft limit reclaim before calling shrink_zone.
2766 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2769 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
2770 total_scanned
+= nr_soft_scanned
;
2773 * We put equal pressure on every zone, unless
2774 * one zone has way too many pages free
2775 * already. The "too many pages" is defined
2776 * as the high wmark plus a "gap" where the
2777 * gap is either the low watermark or 1%
2778 * of the zone, whichever is smaller.
2780 balance_gap
= min(low_wmark_pages(zone
),
2781 (zone
->present_pages
+
2782 KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2783 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2784 if (!zone_watermark_ok_safe(zone
, order
,
2785 high_wmark_pages(zone
) + balance_gap
,
2787 shrink_zone(priority
, zone
, &sc
);
2789 reclaim_state
->reclaimed_slab
= 0;
2790 nr_slab
= shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
);
2791 sc
.nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2792 total_scanned
+= sc
.nr_scanned
;
2794 if (nr_slab
== 0 && !zone_reclaimable(zone
))
2795 zone
->all_unreclaimable
= 1;
2799 * If we've done a decent amount of scanning and
2800 * the reclaim ratio is low, start doing writepage
2801 * even in laptop mode
2803 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
2804 total_scanned
> sc
.nr_reclaimed
+ sc
.nr_reclaimed
/ 2)
2805 sc
.may_writepage
= 1;
2807 if (zone
->all_unreclaimable
) {
2808 if (end_zone
&& end_zone
== i
)
2813 if (!zone_watermark_ok_safe(zone
, order
,
2814 high_wmark_pages(zone
), end_zone
, 0)) {
2817 * We are still under min water mark. This
2818 * means that we have a GFP_ATOMIC allocation
2819 * failure risk. Hurry up!
2821 if (!zone_watermark_ok_safe(zone
, order
,
2822 min_wmark_pages(zone
), end_zone
, 0))
2823 has_under_min_watermark_zone
= 1;
2826 * If a zone reaches its high watermark,
2827 * consider it to be no longer congested. It's
2828 * possible there are dirty pages backed by
2829 * congested BDIs but as pressure is relieved,
2830 * spectulatively avoid congestion waits
2832 zone_clear_flag(zone
, ZONE_CONGESTED
);
2833 if (i
<= *classzone_idx
)
2834 balanced
+= zone
->present_pages
;
2838 if (all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))
2839 break; /* kswapd: all done */
2841 * OK, kswapd is getting into trouble. Take a nap, then take
2842 * another pass across the zones.
2844 if (total_scanned
&& (priority
< DEF_PRIORITY
- 2)) {
2845 if (has_under_min_watermark_zone
)
2846 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT
);
2848 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
2852 * We do this so kswapd doesn't build up large priorities for
2853 * example when it is freeing in parallel with allocators. It
2854 * matches the direct reclaim path behaviour in terms of impact
2855 * on zone->*_priority.
2857 if (sc
.nr_reclaimed
>= SWAP_CLUSTER_MAX
)
2863 * order-0: All zones must meet high watermark for a balanced node
2864 * high-order: Balanced zones must make up at least 25% of the node
2865 * for the node to be balanced
2867 if (!(all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))) {
2873 * Fragmentation may mean that the system cannot be
2874 * rebalanced for high-order allocations in all zones.
2875 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2876 * it means the zones have been fully scanned and are still
2877 * not balanced. For high-order allocations, there is
2878 * little point trying all over again as kswapd may
2881 * Instead, recheck all watermarks at order-0 as they
2882 * are the most important. If watermarks are ok, kswapd will go
2883 * back to sleep. High-order users can still perform direct
2884 * reclaim if they wish.
2886 if (sc
.nr_reclaimed
< SWAP_CLUSTER_MAX
)
2887 order
= sc
.order
= 0;
2893 * If kswapd was reclaiming at a higher order, it has the option of
2894 * sleeping without all zones being balanced. Before it does, it must
2895 * ensure that the watermarks for order-0 on *all* zones are met and
2896 * that the congestion flags are cleared. The congestion flag must
2897 * be cleared as kswapd is the only mechanism that clears the flag
2898 * and it is potentially going to sleep here.
2901 for (i
= 0; i
<= end_zone
; i
++) {
2902 struct zone
*zone
= pgdat
->node_zones
+ i
;
2904 if (!populated_zone(zone
))
2907 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2910 /* Confirm the zone is balanced for order-0 */
2911 if (!zone_watermark_ok(zone
, 0,
2912 high_wmark_pages(zone
), 0, 0)) {
2913 order
= sc
.order
= 0;
2917 /* If balanced, clear the congested flag */
2918 zone_clear_flag(zone
, ZONE_CONGESTED
);
2919 if (i
<= *classzone_idx
)
2920 balanced
+= zone
->present_pages
;
2925 * Return the order we were reclaiming at so sleeping_prematurely()
2926 * makes a decision on the order we were last reclaiming at. However,
2927 * if another caller entered the allocator slow path while kswapd
2928 * was awake, order will remain at the higher level
2930 *classzone_idx
= end_zone
;
2934 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2939 if (freezing(current
) || kthread_should_stop())
2942 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2944 /* Try to sleep for a short interval */
2945 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2946 remaining
= schedule_timeout(HZ
/10);
2947 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2948 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2952 * After a short sleep, check if it was a premature sleep. If not, then
2953 * go fully to sleep until explicitly woken up.
2955 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2956 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
2959 * vmstat counters are not perfectly accurate and the estimated
2960 * value for counters such as NR_FREE_PAGES can deviate from the
2961 * true value by nr_online_cpus * threshold. To avoid the zone
2962 * watermarks being breached while under pressure, we reduce the
2963 * per-cpu vmstat threshold while kswapd is awake and restore
2964 * them before going back to sleep.
2966 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
2968 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
2971 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
2973 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
2975 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2979 * The background pageout daemon, started as a kernel thread
2980 * from the init process.
2982 * This basically trickles out pages so that we have _some_
2983 * free memory available even if there is no other activity
2984 * that frees anything up. This is needed for things like routing
2985 * etc, where we otherwise might have all activity going on in
2986 * asynchronous contexts that cannot page things out.
2988 * If there are applications that are active memory-allocators
2989 * (most normal use), this basically shouldn't matter.
2991 static int kswapd(void *p
)
2993 unsigned long order
, new_order
;
2994 unsigned balanced_order
;
2995 int classzone_idx
, new_classzone_idx
;
2996 int balanced_classzone_idx
;
2997 pg_data_t
*pgdat
= (pg_data_t
*)p
;
2998 struct task_struct
*tsk
= current
;
3000 struct reclaim_state reclaim_state
= {
3001 .reclaimed_slab
= 0,
3003 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
3005 lockdep_set_current_reclaim_state(GFP_KERNEL
);
3007 if (!cpumask_empty(cpumask
))
3008 set_cpus_allowed_ptr(tsk
, cpumask
);
3009 current
->reclaim_state
= &reclaim_state
;
3012 * Tell the memory management that we're a "memory allocator",
3013 * and that if we need more memory we should get access to it
3014 * regardless (see "__alloc_pages()"). "kswapd" should
3015 * never get caught in the normal page freeing logic.
3017 * (Kswapd normally doesn't need memory anyway, but sometimes
3018 * you need a small amount of memory in order to be able to
3019 * page out something else, and this flag essentially protects
3020 * us from recursively trying to free more memory as we're
3021 * trying to free the first piece of memory in the first place).
3023 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
3026 order
= new_order
= 0;
3028 classzone_idx
= new_classzone_idx
= pgdat
->nr_zones
- 1;
3029 balanced_classzone_idx
= classzone_idx
;
3034 * If the last balance_pgdat was unsuccessful it's unlikely a
3035 * new request of a similar or harder type will succeed soon
3036 * so consider going to sleep on the basis we reclaimed at
3038 if (balanced_classzone_idx
>= new_classzone_idx
&&
3039 balanced_order
== new_order
) {
3040 new_order
= pgdat
->kswapd_max_order
;
3041 new_classzone_idx
= pgdat
->classzone_idx
;
3042 pgdat
->kswapd_max_order
= 0;
3043 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3046 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
3048 * Don't sleep if someone wants a larger 'order'
3049 * allocation or has tigher zone constraints
3052 classzone_idx
= new_classzone_idx
;
3054 kswapd_try_to_sleep(pgdat
, balanced_order
,
3055 balanced_classzone_idx
);
3056 order
= pgdat
->kswapd_max_order
;
3057 classzone_idx
= pgdat
->classzone_idx
;
3059 new_classzone_idx
= classzone_idx
;
3060 pgdat
->kswapd_max_order
= 0;
3061 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3064 ret
= try_to_freeze();
3065 if (kthread_should_stop())
3069 * We can speed up thawing tasks if we don't call balance_pgdat
3070 * after returning from the refrigerator
3073 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
3074 balanced_classzone_idx
= classzone_idx
;
3075 balanced_order
= balance_pgdat(pgdat
, order
,
3076 &balanced_classzone_idx
);
3083 * A zone is low on free memory, so wake its kswapd task to service it.
3085 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
3089 if (!populated_zone(zone
))
3092 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
3094 pgdat
= zone
->zone_pgdat
;
3095 if (pgdat
->kswapd_max_order
< order
) {
3096 pgdat
->kswapd_max_order
= order
;
3097 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
3099 if (!waitqueue_active(&pgdat
->kswapd_wait
))
3101 if (zone_watermark_ok_safe(zone
, order
, low_wmark_pages(zone
), 0, 0))
3104 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
3105 wake_up_interruptible(&pgdat
->kswapd_wait
);
3109 * The reclaimable count would be mostly accurate.
3110 * The less reclaimable pages may be
3111 * - mlocked pages, which will be moved to unevictable list when encountered
3112 * - mapped pages, which may require several travels to be reclaimed
3113 * - dirty pages, which is not "instantly" reclaimable
3115 unsigned long global_reclaimable_pages(void)
3119 nr
= global_page_state(NR_ACTIVE_FILE
) +
3120 global_page_state(NR_INACTIVE_FILE
);
3122 if (nr_swap_pages
> 0)
3123 nr
+= global_page_state(NR_ACTIVE_ANON
) +
3124 global_page_state(NR_INACTIVE_ANON
);
3129 unsigned long zone_reclaimable_pages(struct zone
*zone
)
3133 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
3134 zone_page_state(zone
, NR_INACTIVE_FILE
);
3136 if (nr_swap_pages
> 0)
3137 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
3138 zone_page_state(zone
, NR_INACTIVE_ANON
);
3143 #ifdef CONFIG_HIBERNATION
3145 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3148 * Rather than trying to age LRUs the aim is to preserve the overall
3149 * LRU order by reclaiming preferentially
3150 * inactive > active > active referenced > active mapped
3152 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
3154 struct reclaim_state reclaim_state
;
3155 struct scan_control sc
= {
3156 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
3160 .nr_to_reclaim
= nr_to_reclaim
,
3161 .hibernation_mode
= 1,
3164 struct shrink_control shrink
= {
3165 .gfp_mask
= sc
.gfp_mask
,
3167 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3168 struct task_struct
*p
= current
;
3169 unsigned long nr_reclaimed
;
3171 p
->flags
|= PF_MEMALLOC
;
3172 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
3173 reclaim_state
.reclaimed_slab
= 0;
3174 p
->reclaim_state
= &reclaim_state
;
3176 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
3178 p
->reclaim_state
= NULL
;
3179 lockdep_clear_current_reclaim_state();
3180 p
->flags
&= ~PF_MEMALLOC
;
3182 return nr_reclaimed
;
3184 #endif /* CONFIG_HIBERNATION */
3186 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3187 not required for correctness. So if the last cpu in a node goes
3188 away, we get changed to run anywhere: as the first one comes back,
3189 restore their cpu bindings. */
3190 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
3191 unsigned long action
, void *hcpu
)
3195 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
3196 for_each_node_state(nid
, N_HIGH_MEMORY
) {
3197 pg_data_t
*pgdat
= NODE_DATA(nid
);
3198 const struct cpumask
*mask
;
3200 mask
= cpumask_of_node(pgdat
->node_id
);
3202 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3203 /* One of our CPUs online: restore mask */
3204 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
3211 * This kswapd start function will be called by init and node-hot-add.
3212 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3214 int kswapd_run(int nid
)
3216 pg_data_t
*pgdat
= NODE_DATA(nid
);
3222 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
3223 if (IS_ERR(pgdat
->kswapd
)) {
3224 /* failure at boot is fatal */
3225 BUG_ON(system_state
== SYSTEM_BOOTING
);
3226 printk("Failed to start kswapd on node %d\n",nid
);
3233 * Called by memory hotplug when all memory in a node is offlined.
3235 void kswapd_stop(int nid
)
3237 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
3240 kthread_stop(kswapd
);
3243 static int __init
kswapd_init(void)
3248 for_each_node_state(nid
, N_HIGH_MEMORY
)
3250 hotcpu_notifier(cpu_callback
, 0);
3254 module_init(kswapd_init
)
3260 * If non-zero call zone_reclaim when the number of free pages falls below
3263 int zone_reclaim_mode __read_mostly
;
3265 #define RECLAIM_OFF 0
3266 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3267 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3268 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3271 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3272 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3275 #define ZONE_RECLAIM_PRIORITY 4
3278 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3281 int sysctl_min_unmapped_ratio
= 1;
3284 * If the number of slab pages in a zone grows beyond this percentage then
3285 * slab reclaim needs to occur.
3287 int sysctl_min_slab_ratio
= 5;
3289 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
3291 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
3292 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
3293 zone_page_state(zone
, NR_ACTIVE_FILE
);
3296 * It's possible for there to be more file mapped pages than
3297 * accounted for by the pages on the file LRU lists because
3298 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3300 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
3303 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3304 static long zone_pagecache_reclaimable(struct zone
*zone
)
3306 long nr_pagecache_reclaimable
;
3310 * If RECLAIM_SWAP is set, then all file pages are considered
3311 * potentially reclaimable. Otherwise, we have to worry about
3312 * pages like swapcache and zone_unmapped_file_pages() provides
3315 if (zone_reclaim_mode
& RECLAIM_SWAP
)
3316 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
3318 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
3320 /* If we can't clean pages, remove dirty pages from consideration */
3321 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
3322 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
3324 /* Watch for any possible underflows due to delta */
3325 if (unlikely(delta
> nr_pagecache_reclaimable
))
3326 delta
= nr_pagecache_reclaimable
;
3328 return nr_pagecache_reclaimable
- delta
;
3332 * Try to free up some pages from this zone through reclaim.
3334 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3336 /* Minimum pages needed in order to stay on node */
3337 const unsigned long nr_pages
= 1 << order
;
3338 struct task_struct
*p
= current
;
3339 struct reclaim_state reclaim_state
;
3341 struct scan_control sc
= {
3342 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
3343 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
3345 .nr_to_reclaim
= max_t(unsigned long, nr_pages
,
3347 .gfp_mask
= gfp_mask
,
3350 struct shrink_control shrink
= {
3351 .gfp_mask
= sc
.gfp_mask
,
3353 unsigned long nr_slab_pages0
, nr_slab_pages1
;
3357 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3358 * and we also need to be able to write out pages for RECLAIM_WRITE
3361 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
3362 lockdep_set_current_reclaim_state(gfp_mask
);
3363 reclaim_state
.reclaimed_slab
= 0;
3364 p
->reclaim_state
= &reclaim_state
;
3366 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
3368 * Free memory by calling shrink zone with increasing
3369 * priorities until we have enough memory freed.
3371 priority
= ZONE_RECLAIM_PRIORITY
;
3373 shrink_zone(priority
, zone
, &sc
);
3375 } while (priority
>= 0 && sc
.nr_reclaimed
< nr_pages
);
3378 nr_slab_pages0
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3379 if (nr_slab_pages0
> zone
->min_slab_pages
) {
3381 * shrink_slab() does not currently allow us to determine how
3382 * many pages were freed in this zone. So we take the current
3383 * number of slab pages and shake the slab until it is reduced
3384 * by the same nr_pages that we used for reclaiming unmapped
3387 * Note that shrink_slab will free memory on all zones and may
3391 unsigned long lru_pages
= zone_reclaimable_pages(zone
);
3393 /* No reclaimable slab or very low memory pressure */
3394 if (!shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
))
3397 /* Freed enough memory */
3398 nr_slab_pages1
= zone_page_state(zone
,
3399 NR_SLAB_RECLAIMABLE
);
3400 if (nr_slab_pages1
+ nr_pages
<= nr_slab_pages0
)
3405 * Update nr_reclaimed by the number of slab pages we
3406 * reclaimed from this zone.
3408 nr_slab_pages1
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3409 if (nr_slab_pages1
< nr_slab_pages0
)
3410 sc
.nr_reclaimed
+= nr_slab_pages0
- nr_slab_pages1
;
3413 p
->reclaim_state
= NULL
;
3414 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3415 lockdep_clear_current_reclaim_state();
3416 return sc
.nr_reclaimed
>= nr_pages
;
3419 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3425 * Zone reclaim reclaims unmapped file backed pages and
3426 * slab pages if we are over the defined limits.
3428 * A small portion of unmapped file backed pages is needed for
3429 * file I/O otherwise pages read by file I/O will be immediately
3430 * thrown out if the zone is overallocated. So we do not reclaim
3431 * if less than a specified percentage of the zone is used by
3432 * unmapped file backed pages.
3434 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3435 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3436 return ZONE_RECLAIM_FULL
;
3438 if (zone
->all_unreclaimable
)
3439 return ZONE_RECLAIM_FULL
;
3442 * Do not scan if the allocation should not be delayed.
3444 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3445 return ZONE_RECLAIM_NOSCAN
;
3448 * Only run zone reclaim on the local zone or on zones that do not
3449 * have associated processors. This will favor the local processor
3450 * over remote processors and spread off node memory allocations
3451 * as wide as possible.
3453 node_id
= zone_to_nid(zone
);
3454 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3455 return ZONE_RECLAIM_NOSCAN
;
3457 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
3458 return ZONE_RECLAIM_NOSCAN
;
3460 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3461 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
3464 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3471 * page_evictable - test whether a page is evictable
3472 * @page: the page to test
3473 * @vma: the VMA in which the page is or will be mapped, may be NULL
3475 * Test whether page is evictable--i.e., should be placed on active/inactive
3476 * lists vs unevictable list. The vma argument is !NULL when called from the
3477 * fault path to determine how to instantate a new page.
3479 * Reasons page might not be evictable:
3480 * (1) page's mapping marked unevictable
3481 * (2) page is part of an mlocked VMA
3484 int page_evictable(struct page
*page
, struct vm_area_struct
*vma
)
3487 if (mapping_unevictable(page_mapping(page
)))
3490 if (PageMlocked(page
) || (vma
&& is_mlocked_vma(vma
, page
)))
3497 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3498 * @page: page to check evictability and move to appropriate lru list
3499 * @zone: zone page is in
3501 * Checks a page for evictability and moves the page to the appropriate
3504 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3505 * have PageUnevictable set.
3507 static void check_move_unevictable_page(struct page
*page
, struct zone
*zone
)
3509 struct lruvec
*lruvec
;
3511 VM_BUG_ON(PageActive(page
));
3513 ClearPageUnevictable(page
);
3514 if (page_evictable(page
, NULL
)) {
3515 enum lru_list l
= page_lru_base_type(page
);
3517 __dec_zone_state(zone
, NR_UNEVICTABLE
);
3518 lruvec
= mem_cgroup_lru_move_lists(zone
, page
,
3519 LRU_UNEVICTABLE
, l
);
3520 list_move(&page
->lru
, &lruvec
->lists
[l
]);
3521 __inc_zone_state(zone
, NR_INACTIVE_ANON
+ l
);
3522 __count_vm_event(UNEVICTABLE_PGRESCUED
);
3525 * rotate unevictable list
3527 SetPageUnevictable(page
);
3528 lruvec
= mem_cgroup_lru_move_lists(zone
, page
, LRU_UNEVICTABLE
,
3530 list_move(&page
->lru
, &lruvec
->lists
[LRU_UNEVICTABLE
]);
3531 if (page_evictable(page
, NULL
))
3537 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3538 * @mapping: struct address_space to scan for evictable pages
3540 * Scan all pages in mapping. Check unevictable pages for
3541 * evictability and move them to the appropriate zone lru list.
3543 void scan_mapping_unevictable_pages(struct address_space
*mapping
)
3546 pgoff_t end
= (i_size_read(mapping
->host
) + PAGE_CACHE_SIZE
- 1) >>
3549 struct pagevec pvec
;
3551 if (mapping
->nrpages
== 0)
3554 pagevec_init(&pvec
, 0);
3555 while (next
< end
&&
3556 pagevec_lookup(&pvec
, mapping
, next
, PAGEVEC_SIZE
)) {
3562 for (i
= 0; i
< pagevec_count(&pvec
); i
++) {
3563 struct page
*page
= pvec
.pages
[i
];
3564 pgoff_t page_index
= page
->index
;
3565 struct zone
*pagezone
= page_zone(page
);
3568 if (page_index
> next
)
3572 if (pagezone
!= zone
) {
3574 spin_unlock_irq(&zone
->lru_lock
);
3576 spin_lock_irq(&zone
->lru_lock
);
3579 if (PageLRU(page
) && PageUnevictable(page
))
3580 check_move_unevictable_page(page
, zone
);
3583 spin_unlock_irq(&zone
->lru_lock
);
3584 pagevec_release(&pvec
);
3586 count_vm_events(UNEVICTABLE_PGSCANNED
, pg_scanned
);
3591 static void warn_scan_unevictable_pages(void)
3593 printk_once(KERN_WARNING
3594 "%s: The scan_unevictable_pages sysctl/node-interface has been "
3595 "disabled for lack of a legitimate use case. If you have "
3596 "one, please send an email to linux-mm@kvack.org.\n",
3601 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3602 * all nodes' unevictable lists for evictable pages
3604 unsigned long scan_unevictable_pages
;
3606 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
3607 void __user
*buffer
,
3608 size_t *length
, loff_t
*ppos
)
3610 warn_scan_unevictable_pages();
3611 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
3612 scan_unevictable_pages
= 0;
3618 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3619 * a specified node's per zone unevictable lists for evictable pages.
3622 static ssize_t
read_scan_unevictable_node(struct device
*dev
,
3623 struct device_attribute
*attr
,
3626 warn_scan_unevictable_pages();
3627 return sprintf(buf
, "0\n"); /* always zero; should fit... */
3630 static ssize_t
write_scan_unevictable_node(struct device
*dev
,
3631 struct device_attribute
*attr
,
3632 const char *buf
, size_t count
)
3634 warn_scan_unevictable_pages();
3639 static DEVICE_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
3640 read_scan_unevictable_node
,
3641 write_scan_unevictable_node
);
3643 int scan_unevictable_register_node(struct node
*node
)
3645 return device_create_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);
3648 void scan_unevictable_unregister_node(struct node
*node
)
3650 device_remove_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);