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
))
1078 if ((mode
& ISOLATE_CLEAN
) && (PageDirty(page
) || PageWriteback(page
)))
1081 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1084 if (likely(get_page_unless_zero(page
))) {
1086 * Be careful not to clear PageLRU until after we're
1087 * sure the page is not being freed elsewhere -- the
1088 * page release code relies on it.
1098 * zone->lru_lock is heavily contended. Some of the functions that
1099 * shrink the lists perform better by taking out a batch of pages
1100 * and working on them outside the LRU lock.
1102 * For pagecache intensive workloads, this function is the hottest
1103 * spot in the kernel (apart from copy_*_user functions).
1105 * Appropriate locks must be held before calling this function.
1107 * @nr_to_scan: The number of pages to look through on the list.
1108 * @src: The LRU list to pull pages off.
1109 * @dst: The temp list to put pages on to.
1110 * @scanned: The number of pages that were scanned.
1111 * @order: The caller's attempted allocation order
1112 * @mode: One of the LRU isolation modes
1113 * @file: True [1] if isolating file [!anon] pages
1115 * returns how many pages were moved onto *@dst.
1117 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1118 struct list_head
*src
, struct list_head
*dst
,
1119 unsigned long *scanned
, int order
, isolate_mode_t mode
,
1122 unsigned long nr_taken
= 0;
1123 unsigned long nr_lumpy_taken
= 0;
1124 unsigned long nr_lumpy_dirty
= 0;
1125 unsigned long nr_lumpy_failed
= 0;
1128 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
1131 unsigned long end_pfn
;
1132 unsigned long page_pfn
;
1135 page
= lru_to_page(src
);
1136 prefetchw_prev_lru_page(page
, src
, flags
);
1138 VM_BUG_ON(!PageLRU(page
));
1140 switch (__isolate_lru_page(page
, mode
, file
)) {
1142 mem_cgroup_lru_del(page
);
1143 list_move(&page
->lru
, dst
);
1144 nr_taken
+= hpage_nr_pages(page
);
1148 /* else it is being freed elsewhere */
1149 list_move(&page
->lru
, src
);
1160 * Attempt to take all pages in the order aligned region
1161 * surrounding the tag page. Only take those pages of
1162 * the same active state as that tag page. We may safely
1163 * round the target page pfn down to the requested order
1164 * as the mem_map is guaranteed valid out to MAX_ORDER,
1165 * where that page is in a different zone we will detect
1166 * it from its zone id and abort this block scan.
1168 zone_id
= page_zone_id(page
);
1169 page_pfn
= page_to_pfn(page
);
1170 pfn
= page_pfn
& ~((1 << order
) - 1);
1171 end_pfn
= pfn
+ (1 << order
);
1172 for (; pfn
< end_pfn
; pfn
++) {
1173 struct page
*cursor_page
;
1175 /* The target page is in the block, ignore it. */
1176 if (unlikely(pfn
== page_pfn
))
1179 /* Avoid holes within the zone. */
1180 if (unlikely(!pfn_valid_within(pfn
)))
1183 cursor_page
= pfn_to_page(pfn
);
1185 /* Check that we have not crossed a zone boundary. */
1186 if (unlikely(page_zone_id(cursor_page
) != zone_id
))
1190 * If we don't have enough swap space, reclaiming of
1191 * anon page which don't already have a swap slot is
1194 if (nr_swap_pages
<= 0 && PageSwapBacked(cursor_page
) &&
1195 !PageSwapCache(cursor_page
))
1198 if (__isolate_lru_page(cursor_page
, mode
, file
) == 0) {
1199 mem_cgroup_lru_del(cursor_page
);
1200 list_move(&cursor_page
->lru
, dst
);
1201 nr_taken
+= hpage_nr_pages(cursor_page
);
1203 if (PageDirty(cursor_page
))
1208 * Check if the page is freed already.
1210 * We can't use page_count() as that
1211 * requires compound_head and we don't
1212 * have a pin on the page here. If a
1213 * page is tail, we may or may not
1214 * have isolated the head, so assume
1215 * it's not free, it'd be tricky to
1216 * track the head status without a
1219 if (!PageTail(cursor_page
) &&
1220 !atomic_read(&cursor_page
->_count
))
1226 /* If we break out of the loop above, lumpy reclaim failed */
1233 trace_mm_vmscan_lru_isolate(order
,
1236 nr_lumpy_taken
, nr_lumpy_dirty
, nr_lumpy_failed
,
1241 static unsigned long isolate_pages(unsigned long nr
, struct mem_cgroup_zone
*mz
,
1242 struct list_head
*dst
,
1243 unsigned long *scanned
, int order
,
1244 isolate_mode_t mode
, int active
, int file
)
1246 struct lruvec
*lruvec
;
1249 lruvec
= mem_cgroup_zone_lruvec(mz
->zone
, mz
->mem_cgroup
);
1254 return isolate_lru_pages(nr
, &lruvec
->lists
[lru
], dst
,
1255 scanned
, order
, mode
, file
);
1259 * clear_active_flags() is a helper for shrink_active_list(), clearing
1260 * any active bits from the pages in the list.
1262 static unsigned long clear_active_flags(struct list_head
*page_list
,
1263 unsigned int *count
)
1269 list_for_each_entry(page
, page_list
, lru
) {
1270 int numpages
= hpage_nr_pages(page
);
1271 lru
= page_lru_base_type(page
);
1272 if (PageActive(page
)) {
1274 ClearPageActive(page
);
1275 nr_active
+= numpages
;
1278 count
[lru
] += numpages
;
1285 * isolate_lru_page - tries to isolate a page from its LRU list
1286 * @page: page to isolate from its LRU list
1288 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1289 * vmstat statistic corresponding to whatever LRU list the page was on.
1291 * Returns 0 if the page was removed from an LRU list.
1292 * Returns -EBUSY if the page was not on an LRU list.
1294 * The returned page will have PageLRU() cleared. If it was found on
1295 * the active list, it will have PageActive set. If it was found on
1296 * the unevictable list, it will have the PageUnevictable bit set. That flag
1297 * may need to be cleared by the caller before letting the page go.
1299 * The vmstat statistic corresponding to the list on which the page was
1300 * found will be decremented.
1303 * (1) Must be called with an elevated refcount on the page. This is a
1304 * fundamentnal difference from isolate_lru_pages (which is called
1305 * without a stable reference).
1306 * (2) the lru_lock must not be held.
1307 * (3) interrupts must be enabled.
1309 int isolate_lru_page(struct page
*page
)
1313 VM_BUG_ON(!page_count(page
));
1315 if (PageLRU(page
)) {
1316 struct zone
*zone
= page_zone(page
);
1318 spin_lock_irq(&zone
->lru_lock
);
1319 if (PageLRU(page
)) {
1320 int lru
= page_lru(page
);
1325 del_page_from_lru_list(zone
, page
, lru
);
1327 spin_unlock_irq(&zone
->lru_lock
);
1333 * Are there way too many processes in the direct reclaim path already?
1335 static int too_many_isolated(struct zone
*zone
, int file
,
1336 struct scan_control
*sc
)
1338 unsigned long inactive
, isolated
;
1340 if (current_is_kswapd())
1343 if (!global_reclaim(sc
))
1347 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1348 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1350 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1351 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1354 return isolated
> inactive
;
1358 * TODO: Try merging with migrations version of putback_lru_pages
1360 static noinline_for_stack
void
1361 putback_lru_pages(struct mem_cgroup_zone
*mz
, struct scan_control
*sc
,
1362 unsigned long nr_anon
, unsigned long nr_file
,
1363 struct list_head
*page_list
)
1366 struct pagevec pvec
;
1367 struct zone
*zone
= mz
->zone
;
1368 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(mz
);
1370 pagevec_init(&pvec
, 1);
1373 * Put back any unfreeable pages.
1375 spin_lock(&zone
->lru_lock
);
1376 while (!list_empty(page_list
)) {
1378 page
= lru_to_page(page_list
);
1379 VM_BUG_ON(PageLRU(page
));
1380 list_del(&page
->lru
);
1381 if (unlikely(!page_evictable(page
, NULL
))) {
1382 spin_unlock_irq(&zone
->lru_lock
);
1383 putback_lru_page(page
);
1384 spin_lock_irq(&zone
->lru_lock
);
1388 lru
= page_lru(page
);
1389 add_page_to_lru_list(zone
, page
, lru
);
1390 if (is_active_lru(lru
)) {
1391 int file
= is_file_lru(lru
);
1392 int numpages
= hpage_nr_pages(page
);
1393 reclaim_stat
->recent_rotated
[file
] += numpages
;
1395 if (!pagevec_add(&pvec
, page
)) {
1396 spin_unlock_irq(&zone
->lru_lock
);
1397 __pagevec_release(&pvec
);
1398 spin_lock_irq(&zone
->lru_lock
);
1401 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, -nr_anon
);
1402 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -nr_file
);
1404 spin_unlock_irq(&zone
->lru_lock
);
1405 pagevec_release(&pvec
);
1408 static noinline_for_stack
void
1409 update_isolated_counts(struct mem_cgroup_zone
*mz
,
1410 struct scan_control
*sc
,
1411 unsigned long *nr_anon
,
1412 unsigned long *nr_file
,
1413 struct list_head
*isolated_list
)
1415 unsigned long nr_active
;
1416 struct zone
*zone
= mz
->zone
;
1417 unsigned int count
[NR_LRU_LISTS
] = { 0, };
1418 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(mz
);
1420 nr_active
= clear_active_flags(isolated_list
, count
);
1421 __count_vm_events(PGDEACTIVATE
, nr_active
);
1423 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
1424 -count
[LRU_ACTIVE_FILE
]);
1425 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
1426 -count
[LRU_INACTIVE_FILE
]);
1427 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
1428 -count
[LRU_ACTIVE_ANON
]);
1429 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
1430 -count
[LRU_INACTIVE_ANON
]);
1432 *nr_anon
= count
[LRU_ACTIVE_ANON
] + count
[LRU_INACTIVE_ANON
];
1433 *nr_file
= count
[LRU_ACTIVE_FILE
] + count
[LRU_INACTIVE_FILE
];
1434 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, *nr_anon
);
1435 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, *nr_file
);
1437 reclaim_stat
->recent_scanned
[0] += *nr_anon
;
1438 reclaim_stat
->recent_scanned
[1] += *nr_file
;
1442 * Returns true if a direct reclaim should wait on pages under writeback.
1444 * If we are direct reclaiming for contiguous pages and we do not reclaim
1445 * everything in the list, try again and wait for writeback IO to complete.
1446 * This will stall high-order allocations noticeably. Only do that when really
1447 * need to free the pages under high memory pressure.
1449 static inline bool should_reclaim_stall(unsigned long nr_taken
,
1450 unsigned long nr_freed
,
1452 struct scan_control
*sc
)
1454 int lumpy_stall_priority
;
1456 /* kswapd should not stall on sync IO */
1457 if (current_is_kswapd())
1460 /* Only stall on lumpy reclaim */
1461 if (sc
->reclaim_mode
& RECLAIM_MODE_SINGLE
)
1464 /* If we have reclaimed everything on the isolated list, no stall */
1465 if (nr_freed
== nr_taken
)
1469 * For high-order allocations, there are two stall thresholds.
1470 * High-cost allocations stall immediately where as lower
1471 * order allocations such as stacks require the scanning
1472 * priority to be much higher before stalling.
1474 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
1475 lumpy_stall_priority
= DEF_PRIORITY
;
1477 lumpy_stall_priority
= DEF_PRIORITY
/ 3;
1479 return priority
<= lumpy_stall_priority
;
1483 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1484 * of reclaimed pages
1486 static noinline_for_stack
unsigned long
1487 shrink_inactive_list(unsigned long nr_to_scan
, struct mem_cgroup_zone
*mz
,
1488 struct scan_control
*sc
, int priority
, int file
)
1490 LIST_HEAD(page_list
);
1491 unsigned long nr_scanned
;
1492 unsigned long nr_reclaimed
= 0;
1493 unsigned long nr_taken
;
1494 unsigned long nr_anon
;
1495 unsigned long nr_file
;
1496 unsigned long nr_dirty
= 0;
1497 unsigned long nr_writeback
= 0;
1498 isolate_mode_t reclaim_mode
= ISOLATE_INACTIVE
;
1499 struct zone
*zone
= mz
->zone
;
1501 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1502 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1504 /* We are about to die and free our memory. Return now. */
1505 if (fatal_signal_pending(current
))
1506 return SWAP_CLUSTER_MAX
;
1509 set_reclaim_mode(priority
, sc
, false);
1510 if (sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
)
1511 reclaim_mode
|= ISOLATE_ACTIVE
;
1516 reclaim_mode
|= ISOLATE_UNMAPPED
;
1517 if (!sc
->may_writepage
)
1518 reclaim_mode
|= ISOLATE_CLEAN
;
1520 spin_lock_irq(&zone
->lru_lock
);
1522 nr_taken
= isolate_pages(nr_to_scan
, mz
, &page_list
,
1523 &nr_scanned
, sc
->order
,
1524 reclaim_mode
, 0, file
);
1525 if (global_reclaim(sc
)) {
1526 zone
->pages_scanned
+= nr_scanned
;
1527 if (current_is_kswapd())
1528 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
,
1531 __count_zone_vm_events(PGSCAN_DIRECT
, zone
,
1535 if (nr_taken
== 0) {
1536 spin_unlock_irq(&zone
->lru_lock
);
1540 update_isolated_counts(mz
, sc
, &nr_anon
, &nr_file
, &page_list
);
1542 spin_unlock_irq(&zone
->lru_lock
);
1544 nr_reclaimed
= shrink_page_list(&page_list
, mz
, sc
, priority
,
1545 &nr_dirty
, &nr_writeback
);
1547 /* Check if we should syncronously wait for writeback */
1548 if (should_reclaim_stall(nr_taken
, nr_reclaimed
, priority
, sc
)) {
1549 set_reclaim_mode(priority
, sc
, true);
1550 nr_reclaimed
+= shrink_page_list(&page_list
, mz
, sc
,
1551 priority
, &nr_dirty
, &nr_writeback
);
1554 local_irq_disable();
1555 if (current_is_kswapd())
1556 __count_vm_events(KSWAPD_STEAL
, nr_reclaimed
);
1557 __count_zone_vm_events(PGSTEAL
, zone
, nr_reclaimed
);
1559 putback_lru_pages(mz
, sc
, nr_anon
, nr_file
, &page_list
);
1562 * If reclaim is isolating dirty pages under writeback, it implies
1563 * that the long-lived page allocation rate is exceeding the page
1564 * laundering rate. Either the global limits are not being effective
1565 * at throttling processes due to the page distribution throughout
1566 * zones or there is heavy usage of a slow backing device. The
1567 * only option is to throttle from reclaim context which is not ideal
1568 * as there is no guarantee the dirtying process is throttled in the
1569 * same way balance_dirty_pages() manages.
1571 * This scales the number of dirty pages that must be under writeback
1572 * before throttling depending on priority. It is a simple backoff
1573 * function that has the most effect in the range DEF_PRIORITY to
1574 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1575 * in trouble and reclaim is considered to be in trouble.
1577 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1578 * DEF_PRIORITY-1 50% must be PageWriteback
1579 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1581 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1582 * isolated page is PageWriteback
1584 if (nr_writeback
&& nr_writeback
>= (nr_taken
>> (DEF_PRIORITY
-priority
)))
1585 wait_iff_congested(zone
, BLK_RW_ASYNC
, HZ
/10);
1587 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1589 nr_scanned
, nr_reclaimed
,
1591 trace_shrink_flags(file
, sc
->reclaim_mode
));
1592 return nr_reclaimed
;
1596 * This moves pages from the active list to the inactive list.
1598 * We move them the other way if the page is referenced by one or more
1599 * processes, from rmap.
1601 * If the pages are mostly unmapped, the processing is fast and it is
1602 * appropriate to hold zone->lru_lock across the whole operation. But if
1603 * the pages are mapped, the processing is slow (page_referenced()) so we
1604 * should drop zone->lru_lock around each page. It's impossible to balance
1605 * this, so instead we remove the pages from the LRU while processing them.
1606 * It is safe to rely on PG_active against the non-LRU pages in here because
1607 * nobody will play with that bit on a non-LRU page.
1609 * The downside is that we have to touch page->_count against each page.
1610 * But we had to alter page->flags anyway.
1613 static void move_active_pages_to_lru(struct zone
*zone
,
1614 struct list_head
*list
,
1617 unsigned long pgmoved
= 0;
1618 struct pagevec pvec
;
1621 pagevec_init(&pvec
, 1);
1623 while (!list_empty(list
)) {
1624 struct lruvec
*lruvec
;
1626 page
= lru_to_page(list
);
1628 VM_BUG_ON(PageLRU(page
));
1631 lruvec
= mem_cgroup_lru_add_list(zone
, page
, lru
);
1632 list_move(&page
->lru
, &lruvec
->lists
[lru
]);
1633 pgmoved
+= hpage_nr_pages(page
);
1635 if (!pagevec_add(&pvec
, page
) || list_empty(list
)) {
1636 spin_unlock_irq(&zone
->lru_lock
);
1637 if (buffer_heads_over_limit
)
1638 pagevec_strip(&pvec
);
1639 __pagevec_release(&pvec
);
1640 spin_lock_irq(&zone
->lru_lock
);
1643 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1644 if (!is_active_lru(lru
))
1645 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1648 static void shrink_active_list(unsigned long nr_pages
,
1649 struct mem_cgroup_zone
*mz
,
1650 struct scan_control
*sc
,
1651 int priority
, int file
)
1653 unsigned long nr_taken
;
1654 unsigned long pgscanned
;
1655 unsigned long vm_flags
;
1656 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1657 LIST_HEAD(l_active
);
1658 LIST_HEAD(l_inactive
);
1660 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(mz
);
1661 unsigned long nr_rotated
= 0;
1662 isolate_mode_t reclaim_mode
= ISOLATE_ACTIVE
;
1663 struct zone
*zone
= mz
->zone
;
1668 reclaim_mode
|= ISOLATE_UNMAPPED
;
1669 if (!sc
->may_writepage
)
1670 reclaim_mode
|= ISOLATE_CLEAN
;
1672 spin_lock_irq(&zone
->lru_lock
);
1674 nr_taken
= isolate_pages(nr_pages
, mz
, &l_hold
,
1675 &pgscanned
, sc
->order
,
1676 reclaim_mode
, 1, file
);
1678 if (global_reclaim(sc
))
1679 zone
->pages_scanned
+= pgscanned
;
1681 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1683 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1685 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -nr_taken
);
1687 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -nr_taken
);
1688 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1689 spin_unlock_irq(&zone
->lru_lock
);
1691 while (!list_empty(&l_hold
)) {
1693 page
= lru_to_page(&l_hold
);
1694 list_del(&page
->lru
);
1696 if (unlikely(!page_evictable(page
, NULL
))) {
1697 putback_lru_page(page
);
1701 if (page_referenced(page
, 0, mz
->mem_cgroup
, &vm_flags
)) {
1702 nr_rotated
+= hpage_nr_pages(page
);
1704 * Identify referenced, file-backed active pages and
1705 * give them one more trip around the active list. So
1706 * that executable code get better chances to stay in
1707 * memory under moderate memory pressure. Anon pages
1708 * are not likely to be evicted by use-once streaming
1709 * IO, plus JVM can create lots of anon VM_EXEC pages,
1710 * so we ignore them here.
1712 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1713 list_add(&page
->lru
, &l_active
);
1718 ClearPageActive(page
); /* we are de-activating */
1719 list_add(&page
->lru
, &l_inactive
);
1723 * Move pages back to the lru list.
1725 spin_lock_irq(&zone
->lru_lock
);
1727 * Count referenced pages from currently used mappings as rotated,
1728 * even though only some of them are actually re-activated. This
1729 * helps balance scan pressure between file and anonymous pages in
1732 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1734 move_active_pages_to_lru(zone
, &l_active
,
1735 LRU_ACTIVE
+ file
* LRU_FILE
);
1736 move_active_pages_to_lru(zone
, &l_inactive
,
1737 LRU_BASE
+ file
* LRU_FILE
);
1738 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1739 spin_unlock_irq(&zone
->lru_lock
);
1743 static int inactive_anon_is_low_global(struct zone
*zone
)
1745 unsigned long active
, inactive
;
1747 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1748 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1750 if (inactive
* zone
->inactive_ratio
< active
)
1757 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1758 * @zone: zone to check
1759 * @sc: scan control of this context
1761 * Returns true if the zone does not have enough inactive anon pages,
1762 * meaning some active anon pages need to be deactivated.
1764 static int inactive_anon_is_low(struct mem_cgroup_zone
*mz
)
1767 * If we don't have swap space, anonymous page deactivation
1770 if (!total_swap_pages
)
1773 if (!scanning_global_lru(mz
))
1774 return mem_cgroup_inactive_anon_is_low(mz
->mem_cgroup
,
1777 return inactive_anon_is_low_global(mz
->zone
);
1780 static inline int inactive_anon_is_low(struct mem_cgroup_zone
*mz
)
1786 static int inactive_file_is_low_global(struct zone
*zone
)
1788 unsigned long active
, inactive
;
1790 active
= zone_page_state(zone
, NR_ACTIVE_FILE
);
1791 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1793 return (active
> inactive
);
1797 * inactive_file_is_low - check if file pages need to be deactivated
1798 * @mz: memory cgroup and zone to check
1800 * When the system is doing streaming IO, memory pressure here
1801 * ensures that active file pages get deactivated, until more
1802 * than half of the file pages are on the inactive list.
1804 * Once we get to that situation, protect the system's working
1805 * set from being evicted by disabling active file page aging.
1807 * This uses a different ratio than the anonymous pages, because
1808 * the page cache uses a use-once replacement algorithm.
1810 static int inactive_file_is_low(struct mem_cgroup_zone
*mz
)
1812 if (!scanning_global_lru(mz
))
1813 return mem_cgroup_inactive_file_is_low(mz
->mem_cgroup
,
1816 return inactive_file_is_low_global(mz
->zone
);
1819 static int inactive_list_is_low(struct mem_cgroup_zone
*mz
, int file
)
1822 return inactive_file_is_low(mz
);
1824 return inactive_anon_is_low(mz
);
1827 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1828 struct mem_cgroup_zone
*mz
,
1829 struct scan_control
*sc
, int priority
)
1831 int file
= is_file_lru(lru
);
1833 if (is_active_lru(lru
)) {
1834 if (inactive_list_is_low(mz
, file
))
1835 shrink_active_list(nr_to_scan
, mz
, sc
, priority
, file
);
1839 return shrink_inactive_list(nr_to_scan
, mz
, sc
, priority
, file
);
1842 static int vmscan_swappiness(struct mem_cgroup_zone
*mz
,
1843 struct scan_control
*sc
)
1845 if (global_reclaim(sc
))
1846 return vm_swappiness
;
1847 return mem_cgroup_swappiness(mz
->mem_cgroup
);
1851 * Determine how aggressively the anon and file LRU lists should be
1852 * scanned. The relative value of each set of LRU lists is determined
1853 * by looking at the fraction of the pages scanned we did rotate back
1854 * onto the active list instead of evict.
1856 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1858 static void get_scan_count(struct mem_cgroup_zone
*mz
, struct scan_control
*sc
,
1859 unsigned long *nr
, int priority
)
1861 unsigned long anon
, file
, free
;
1862 unsigned long anon_prio
, file_prio
;
1863 unsigned long ap
, fp
;
1864 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(mz
);
1865 u64 fraction
[2], denominator
;
1868 bool force_scan
= false;
1871 * If the zone or memcg is small, nr[l] can be 0. This
1872 * results in no scanning on this priority and a potential
1873 * priority drop. Global direct reclaim can go to the next
1874 * zone and tends to have no problems. Global kswapd is for
1875 * zone balancing and it needs to scan a minimum amount. When
1876 * reclaiming for a memcg, a priority drop can cause high
1877 * latencies, so it's better to scan a minimum amount there as
1880 if (current_is_kswapd() && mz
->zone
->all_unreclaimable
)
1882 if (!global_reclaim(sc
))
1885 /* If we have no swap space, do not bother scanning anon pages. */
1886 if (!sc
->may_swap
|| (nr_swap_pages
<= 0)) {
1894 anon
= zone_nr_lru_pages(mz
, LRU_ACTIVE_ANON
) +
1895 zone_nr_lru_pages(mz
, LRU_INACTIVE_ANON
);
1896 file
= zone_nr_lru_pages(mz
, LRU_ACTIVE_FILE
) +
1897 zone_nr_lru_pages(mz
, LRU_INACTIVE_FILE
);
1899 if (global_reclaim(sc
)) {
1900 free
= zone_page_state(mz
->zone
, NR_FREE_PAGES
);
1901 /* If we have very few page cache pages,
1902 force-scan anon pages. */
1903 if (unlikely(file
+ free
<= high_wmark_pages(mz
->zone
))) {
1912 * With swappiness at 100, anonymous and file have the same priority.
1913 * This scanning priority is essentially the inverse of IO cost.
1915 anon_prio
= vmscan_swappiness(mz
, sc
);
1916 file_prio
= 200 - vmscan_swappiness(mz
, sc
);
1919 * OK, so we have swap space and a fair amount of page cache
1920 * pages. We use the recently rotated / recently scanned
1921 * ratios to determine how valuable each cache is.
1923 * Because workloads change over time (and to avoid overflow)
1924 * we keep these statistics as a floating average, which ends
1925 * up weighing recent references more than old ones.
1927 * anon in [0], file in [1]
1929 spin_lock_irq(&mz
->zone
->lru_lock
);
1930 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1931 reclaim_stat
->recent_scanned
[0] /= 2;
1932 reclaim_stat
->recent_rotated
[0] /= 2;
1935 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1936 reclaim_stat
->recent_scanned
[1] /= 2;
1937 reclaim_stat
->recent_rotated
[1] /= 2;
1941 * The amount of pressure on anon vs file pages is inversely
1942 * proportional to the fraction of recently scanned pages on
1943 * each list that were recently referenced and in active use.
1945 ap
= (anon_prio
+ 1) * (reclaim_stat
->recent_scanned
[0] + 1);
1946 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1948 fp
= (file_prio
+ 1) * (reclaim_stat
->recent_scanned
[1] + 1);
1949 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1950 spin_unlock_irq(&mz
->zone
->lru_lock
);
1954 denominator
= ap
+ fp
+ 1;
1956 for_each_evictable_lru(l
) {
1957 int file
= is_file_lru(l
);
1960 scan
= zone_nr_lru_pages(mz
, l
);
1961 if (priority
|| noswap
) {
1963 if (!scan
&& force_scan
)
1964 scan
= SWAP_CLUSTER_MAX
;
1965 scan
= div64_u64(scan
* fraction
[file
], denominator
);
1972 * Reclaim/compaction depends on a number of pages being freed. To avoid
1973 * disruption to the system, a small number of order-0 pages continue to be
1974 * rotated and reclaimed in the normal fashion. However, by the time we get
1975 * back to the allocator and call try_to_compact_zone(), we ensure that
1976 * there are enough free pages for it to be likely successful
1978 static inline bool should_continue_reclaim(struct mem_cgroup_zone
*mz
,
1979 unsigned long nr_reclaimed
,
1980 unsigned long nr_scanned
,
1981 struct scan_control
*sc
)
1983 unsigned long pages_for_compaction
;
1984 unsigned long inactive_lru_pages
;
1986 /* If not in reclaim/compaction mode, stop */
1987 if (!(sc
->reclaim_mode
& RECLAIM_MODE_COMPACTION
))
1990 /* Consider stopping depending on scan and reclaim activity */
1991 if (sc
->gfp_mask
& __GFP_REPEAT
) {
1993 * For __GFP_REPEAT allocations, stop reclaiming if the
1994 * full LRU list has been scanned and we are still failing
1995 * to reclaim pages. This full LRU scan is potentially
1996 * expensive but a __GFP_REPEAT caller really wants to succeed
1998 if (!nr_reclaimed
&& !nr_scanned
)
2002 * For non-__GFP_REPEAT allocations which can presumably
2003 * fail without consequence, stop if we failed to reclaim
2004 * any pages from the last SWAP_CLUSTER_MAX number of
2005 * pages that were scanned. This will return to the
2006 * caller faster at the risk reclaim/compaction and
2007 * the resulting allocation attempt fails
2014 * If we have not reclaimed enough pages for compaction and the
2015 * inactive lists are large enough, continue reclaiming
2017 pages_for_compaction
= (2UL << sc
->order
);
2018 inactive_lru_pages
= zone_nr_lru_pages(mz
, LRU_INACTIVE_FILE
);
2019 if (nr_swap_pages
> 0)
2020 inactive_lru_pages
+= zone_nr_lru_pages(mz
, LRU_INACTIVE_ANON
);
2021 if (sc
->nr_reclaimed
< pages_for_compaction
&&
2022 inactive_lru_pages
> pages_for_compaction
)
2025 /* If compaction would go ahead or the allocation would succeed, stop */
2026 switch (compaction_suitable(mz
->zone
, sc
->order
)) {
2027 case COMPACT_PARTIAL
:
2028 case COMPACT_CONTINUE
:
2036 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2038 static void shrink_mem_cgroup_zone(int priority
, struct mem_cgroup_zone
*mz
,
2039 struct scan_control
*sc
)
2041 unsigned long nr
[NR_LRU_LISTS
];
2042 unsigned long nr_to_scan
;
2044 unsigned long nr_reclaimed
, nr_scanned
;
2045 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2046 struct blk_plug plug
;
2050 nr_scanned
= sc
->nr_scanned
;
2051 get_scan_count(mz
, sc
, nr
, priority
);
2053 blk_start_plug(&plug
);
2054 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2055 nr
[LRU_INACTIVE_FILE
]) {
2056 for_each_evictable_lru(l
) {
2058 nr_to_scan
= min_t(unsigned long,
2059 nr
[l
], SWAP_CLUSTER_MAX
);
2060 nr
[l
] -= nr_to_scan
;
2062 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
2067 * On large memory systems, scan >> priority can become
2068 * really large. This is fine for the starting priority;
2069 * we want to put equal scanning pressure on each zone.
2070 * However, if the VM has a harder time of freeing pages,
2071 * with multiple processes reclaiming pages, the total
2072 * freeing target can get unreasonably large.
2074 if (nr_reclaimed
>= nr_to_reclaim
&& priority
< DEF_PRIORITY
)
2077 blk_finish_plug(&plug
);
2078 sc
->nr_reclaimed
+= nr_reclaimed
;
2081 * Even if we did not try to evict anon pages at all, we want to
2082 * rebalance the anon lru active/inactive ratio.
2084 if (inactive_anon_is_low(mz
))
2085 shrink_active_list(SWAP_CLUSTER_MAX
, mz
, sc
, priority
, 0);
2087 /* reclaim/compaction might need reclaim to continue */
2088 if (should_continue_reclaim(mz
, nr_reclaimed
,
2089 sc
->nr_scanned
- nr_scanned
, sc
))
2092 throttle_vm_writeout(sc
->gfp_mask
);
2095 static void shrink_zone(int priority
, struct zone
*zone
,
2096 struct scan_control
*sc
)
2098 struct mem_cgroup
*root
= sc
->target_mem_cgroup
;
2099 struct mem_cgroup_reclaim_cookie reclaim
= {
2101 .priority
= priority
,
2103 struct mem_cgroup
*memcg
;
2105 memcg
= mem_cgroup_iter(root
, NULL
, &reclaim
);
2107 struct mem_cgroup_zone mz
= {
2108 .mem_cgroup
= memcg
,
2112 shrink_mem_cgroup_zone(priority
, &mz
, sc
);
2114 * Limit reclaim has historically picked one memcg and
2115 * scanned it with decreasing priority levels until
2116 * nr_to_reclaim had been reclaimed. This priority
2117 * cycle is thus over after a single memcg.
2119 * Direct reclaim and kswapd, on the other hand, have
2120 * to scan all memory cgroups to fulfill the overall
2121 * scan target for the zone.
2123 if (!global_reclaim(sc
)) {
2124 mem_cgroup_iter_break(root
, memcg
);
2127 memcg
= mem_cgroup_iter(root
, memcg
, &reclaim
);
2132 * This is the direct reclaim path, for page-allocating processes. We only
2133 * try to reclaim pages from zones which will satisfy the caller's allocation
2136 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2138 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2140 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2141 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2142 * zone defense algorithm.
2144 * If a zone is deemed to be full of pinned pages then just give it a light
2145 * scan then give up on it.
2147 * This function returns true if a zone is being reclaimed for a costly
2148 * high-order allocation and compaction is either ready to begin or deferred.
2149 * This indicates to the caller that it should retry the allocation or fail.
2151 static bool shrink_zones(int priority
, struct zonelist
*zonelist
,
2152 struct scan_control
*sc
)
2156 unsigned long nr_soft_reclaimed
;
2157 unsigned long nr_soft_scanned
;
2158 bool should_abort_reclaim
= false;
2160 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2161 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2162 if (!populated_zone(zone
))
2165 * Take care memory controller reclaiming has small influence
2168 if (global_reclaim(sc
)) {
2169 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2171 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2172 continue; /* Let kswapd poll it */
2173 if (COMPACTION_BUILD
) {
2175 * If we already have plenty of memory free for
2176 * compaction in this zone, don't free any more.
2177 * Even though compaction is invoked for any
2178 * non-zero order, only frequent costly order
2179 * reclamation is disruptive enough to become a
2180 * noticable problem, like transparent huge page
2183 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
2184 (compaction_suitable(zone
, sc
->order
) ||
2185 compaction_deferred(zone
))) {
2186 should_abort_reclaim
= true;
2191 * This steals pages from memory cgroups over softlimit
2192 * and returns the number of reclaimed pages and
2193 * scanned pages. This works for global memory pressure
2194 * and balancing, not for a memcg's limit.
2196 nr_soft_scanned
= 0;
2197 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2198 sc
->order
, sc
->gfp_mask
,
2200 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2201 sc
->nr_scanned
+= nr_soft_scanned
;
2202 /* need some check for avoid more shrink_zone() */
2205 shrink_zone(priority
, zone
, sc
);
2208 return should_abort_reclaim
;
2211 static bool zone_reclaimable(struct zone
*zone
)
2213 return zone
->pages_scanned
< zone_reclaimable_pages(zone
) * 6;
2216 /* All zones in zonelist are unreclaimable? */
2217 static bool all_unreclaimable(struct zonelist
*zonelist
,
2218 struct scan_control
*sc
)
2223 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2224 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2225 if (!populated_zone(zone
))
2227 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2229 if (!zone
->all_unreclaimable
)
2237 * This is the main entry point to direct page reclaim.
2239 * If a full scan of the inactive list fails to free enough memory then we
2240 * are "out of memory" and something needs to be killed.
2242 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2243 * high - the zone may be full of dirty or under-writeback pages, which this
2244 * caller can't do much about. We kick the writeback threads and take explicit
2245 * naps in the hope that some of these pages can be written. But if the
2246 * allocating task holds filesystem locks which prevent writeout this might not
2247 * work, and the allocation attempt will fail.
2249 * returns: 0, if no pages reclaimed
2250 * else, the number of pages reclaimed
2252 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2253 struct scan_control
*sc
,
2254 struct shrink_control
*shrink
)
2257 unsigned long total_scanned
= 0;
2258 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2261 unsigned long writeback_threshold
;
2264 delayacct_freepages_start();
2266 if (global_reclaim(sc
))
2267 count_vm_event(ALLOCSTALL
);
2269 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2272 disable_swap_token(sc
->target_mem_cgroup
);
2273 if (shrink_zones(priority
, zonelist
, sc
))
2277 * Don't shrink slabs when reclaiming memory from
2278 * over limit cgroups
2280 if (global_reclaim(sc
)) {
2281 unsigned long lru_pages
= 0;
2282 for_each_zone_zonelist(zone
, z
, zonelist
,
2283 gfp_zone(sc
->gfp_mask
)) {
2284 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2287 lru_pages
+= zone_reclaimable_pages(zone
);
2290 shrink_slab(shrink
, sc
->nr_scanned
, lru_pages
);
2291 if (reclaim_state
) {
2292 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2293 reclaim_state
->reclaimed_slab
= 0;
2296 total_scanned
+= sc
->nr_scanned
;
2297 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2301 * Try to write back as many pages as we just scanned. This
2302 * tends to cause slow streaming writers to write data to the
2303 * disk smoothly, at the dirtying rate, which is nice. But
2304 * that's undesirable in laptop mode, where we *want* lumpy
2305 * writeout. So in laptop mode, write out the whole world.
2307 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2308 if (total_scanned
> writeback_threshold
) {
2309 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
,
2310 WB_REASON_TRY_TO_FREE_PAGES
);
2311 sc
->may_writepage
= 1;
2314 /* Take a nap, wait for some writeback to complete */
2315 if (!sc
->hibernation_mode
&& sc
->nr_scanned
&&
2316 priority
< DEF_PRIORITY
- 2) {
2317 struct zone
*preferred_zone
;
2319 first_zones_zonelist(zonelist
, gfp_zone(sc
->gfp_mask
),
2320 &cpuset_current_mems_allowed
,
2322 wait_iff_congested(preferred_zone
, BLK_RW_ASYNC
, HZ
/10);
2327 delayacct_freepages_end();
2330 if (sc
->nr_reclaimed
)
2331 return sc
->nr_reclaimed
;
2334 * As hibernation is going on, kswapd is freezed so that it can't mark
2335 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2338 if (oom_killer_disabled
)
2341 /* top priority shrink_zones still had more to do? don't OOM, then */
2342 if (global_reclaim(sc
) && !all_unreclaimable(zonelist
, sc
))
2348 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2349 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2351 unsigned long nr_reclaimed
;
2352 struct scan_control sc
= {
2353 .gfp_mask
= gfp_mask
,
2354 .may_writepage
= !laptop_mode
,
2355 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2359 .target_mem_cgroup
= NULL
,
2360 .nodemask
= nodemask
,
2362 struct shrink_control shrink
= {
2363 .gfp_mask
= sc
.gfp_mask
,
2366 trace_mm_vmscan_direct_reclaim_begin(order
,
2370 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2372 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2374 return nr_reclaimed
;
2377 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2379 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*memcg
,
2380 gfp_t gfp_mask
, bool noswap
,
2382 unsigned long *nr_scanned
)
2384 struct scan_control sc
= {
2386 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2387 .may_writepage
= !laptop_mode
,
2389 .may_swap
= !noswap
,
2391 .target_mem_cgroup
= memcg
,
2393 struct mem_cgroup_zone mz
= {
2394 .mem_cgroup
= memcg
,
2398 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2399 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2401 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2406 * NOTE: Although we can get the priority field, using it
2407 * here is not a good idea, since it limits the pages we can scan.
2408 * if we don't reclaim here, the shrink_zone from balance_pgdat
2409 * will pick up pages from other mem cgroup's as well. We hack
2410 * the priority and make it zero.
2412 shrink_mem_cgroup_zone(0, &mz
, &sc
);
2414 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2416 *nr_scanned
= sc
.nr_scanned
;
2417 return sc
.nr_reclaimed
;
2420 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
2424 struct zonelist
*zonelist
;
2425 unsigned long nr_reclaimed
;
2427 struct scan_control sc
= {
2428 .may_writepage
= !laptop_mode
,
2430 .may_swap
= !noswap
,
2431 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2433 .target_mem_cgroup
= memcg
,
2434 .nodemask
= NULL
, /* we don't care the placement */
2435 .gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2436 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
2438 struct shrink_control shrink
= {
2439 .gfp_mask
= sc
.gfp_mask
,
2443 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2444 * take care of from where we get pages. So the node where we start the
2445 * scan does not need to be the current node.
2447 nid
= mem_cgroup_select_victim_node(memcg
);
2449 zonelist
= NODE_DATA(nid
)->node_zonelists
;
2451 trace_mm_vmscan_memcg_reclaim_begin(0,
2455 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2457 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2459 return nr_reclaimed
;
2463 static void age_active_anon(struct zone
*zone
, struct scan_control
*sc
,
2466 struct mem_cgroup
*memcg
;
2468 if (!total_swap_pages
)
2471 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
2473 struct mem_cgroup_zone mz
= {
2474 .mem_cgroup
= memcg
,
2478 if (inactive_anon_is_low(&mz
))
2479 shrink_active_list(SWAP_CLUSTER_MAX
, &mz
,
2482 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
2487 * pgdat_balanced is used when checking if a node is balanced for high-order
2488 * allocations. Only zones that meet watermarks and are in a zone allowed
2489 * by the callers classzone_idx are added to balanced_pages. The total of
2490 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2491 * for the node to be considered balanced. Forcing all zones to be balanced
2492 * for high orders can cause excessive reclaim when there are imbalanced zones.
2493 * The choice of 25% is due to
2494 * o a 16M DMA zone that is balanced will not balance a zone on any
2495 * reasonable sized machine
2496 * o On all other machines, the top zone must be at least a reasonable
2497 * percentage of the middle zones. For example, on 32-bit x86, highmem
2498 * would need to be at least 256M for it to be balance a whole node.
2499 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2500 * to balance a node on its own. These seemed like reasonable ratios.
2502 static bool pgdat_balanced(pg_data_t
*pgdat
, unsigned long balanced_pages
,
2505 unsigned long present_pages
= 0;
2508 for (i
= 0; i
<= classzone_idx
; i
++)
2509 present_pages
+= pgdat
->node_zones
[i
].present_pages
;
2511 /* A special case here: if zone has no page, we think it's balanced */
2512 return balanced_pages
>= (present_pages
>> 2);
2515 /* is kswapd sleeping prematurely? */
2516 static bool sleeping_prematurely(pg_data_t
*pgdat
, int order
, long remaining
,
2520 unsigned long balanced
= 0;
2521 bool all_zones_ok
= true;
2523 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2527 /* Check the watermark levels */
2528 for (i
= 0; i
<= classzone_idx
; i
++) {
2529 struct zone
*zone
= pgdat
->node_zones
+ i
;
2531 if (!populated_zone(zone
))
2535 * balance_pgdat() skips over all_unreclaimable after
2536 * DEF_PRIORITY. Effectively, it considers them balanced so
2537 * they must be considered balanced here as well if kswapd
2540 if (zone
->all_unreclaimable
) {
2541 balanced
+= zone
->present_pages
;
2545 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
),
2547 all_zones_ok
= false;
2549 balanced
+= zone
->present_pages
;
2553 * For high-order requests, the balanced zones must contain at least
2554 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2558 return !pgdat_balanced(pgdat
, balanced
, classzone_idx
);
2560 return !all_zones_ok
;
2564 * For kswapd, balance_pgdat() will work across all this node's zones until
2565 * they are all at high_wmark_pages(zone).
2567 * Returns the final order kswapd was reclaiming at
2569 * There is special handling here for zones which are full of pinned pages.
2570 * This can happen if the pages are all mlocked, or if they are all used by
2571 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2572 * What we do is to detect the case where all pages in the zone have been
2573 * scanned twice and there has been zero successful reclaim. Mark the zone as
2574 * dead and from now on, only perform a short scan. Basically we're polling
2575 * the zone for when the problem goes away.
2577 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2578 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2579 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2580 * lower zones regardless of the number of free pages in the lower zones. This
2581 * interoperates with the page allocator fallback scheme to ensure that aging
2582 * of pages is balanced across the zones.
2584 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
2588 unsigned long balanced
;
2591 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
2592 unsigned long total_scanned
;
2593 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2594 unsigned long nr_soft_reclaimed
;
2595 unsigned long nr_soft_scanned
;
2596 struct scan_control sc
= {
2597 .gfp_mask
= GFP_KERNEL
,
2601 * kswapd doesn't want to be bailed out while reclaim. because
2602 * we want to put equal scanning pressure on each zone.
2604 .nr_to_reclaim
= ULONG_MAX
,
2606 .target_mem_cgroup
= NULL
,
2608 struct shrink_control shrink
= {
2609 .gfp_mask
= sc
.gfp_mask
,
2613 sc
.nr_reclaimed
= 0;
2614 sc
.may_writepage
= !laptop_mode
;
2615 count_vm_event(PAGEOUTRUN
);
2617 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2618 unsigned long lru_pages
= 0;
2619 int has_under_min_watermark_zone
= 0;
2621 /* The swap token gets in the way of swapout... */
2623 disable_swap_token(NULL
);
2629 * Scan in the highmem->dma direction for the highest
2630 * zone which needs scanning
2632 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
2633 struct zone
*zone
= pgdat
->node_zones
+ i
;
2635 if (!populated_zone(zone
))
2638 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2642 * Do some background aging of the anon list, to give
2643 * pages a chance to be referenced before reclaiming.
2645 age_active_anon(zone
, &sc
, priority
);
2647 if (!zone_watermark_ok_safe(zone
, order
,
2648 high_wmark_pages(zone
), 0, 0)) {
2652 /* If balanced, clear the congested flag */
2653 zone_clear_flag(zone
, ZONE_CONGESTED
);
2659 for (i
= 0; i
<= end_zone
; i
++) {
2660 struct zone
*zone
= pgdat
->node_zones
+ i
;
2662 lru_pages
+= zone_reclaimable_pages(zone
);
2666 * Now scan the zone in the dma->highmem direction, stopping
2667 * at the last zone which needs scanning.
2669 * We do this because the page allocator works in the opposite
2670 * direction. This prevents the page allocator from allocating
2671 * pages behind kswapd's direction of progress, which would
2672 * cause too much scanning of the lower zones.
2674 for (i
= 0; i
<= end_zone
; i
++) {
2675 struct zone
*zone
= pgdat
->node_zones
+ i
;
2677 unsigned long balance_gap
;
2679 if (!populated_zone(zone
))
2682 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2687 nr_soft_scanned
= 0;
2689 * Call soft limit reclaim before calling shrink_zone.
2691 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2694 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
2695 total_scanned
+= nr_soft_scanned
;
2698 * We put equal pressure on every zone, unless
2699 * one zone has way too many pages free
2700 * already. The "too many pages" is defined
2701 * as the high wmark plus a "gap" where the
2702 * gap is either the low watermark or 1%
2703 * of the zone, whichever is smaller.
2705 balance_gap
= min(low_wmark_pages(zone
),
2706 (zone
->present_pages
+
2707 KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2708 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2709 if (!zone_watermark_ok_safe(zone
, order
,
2710 high_wmark_pages(zone
) + balance_gap
,
2712 shrink_zone(priority
, zone
, &sc
);
2714 reclaim_state
->reclaimed_slab
= 0;
2715 nr_slab
= shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
);
2716 sc
.nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2717 total_scanned
+= sc
.nr_scanned
;
2719 if (nr_slab
== 0 && !zone_reclaimable(zone
))
2720 zone
->all_unreclaimable
= 1;
2724 * If we've done a decent amount of scanning and
2725 * the reclaim ratio is low, start doing writepage
2726 * even in laptop mode
2728 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
2729 total_scanned
> sc
.nr_reclaimed
+ sc
.nr_reclaimed
/ 2)
2730 sc
.may_writepage
= 1;
2732 if (zone
->all_unreclaimable
) {
2733 if (end_zone
&& end_zone
== i
)
2738 if (!zone_watermark_ok_safe(zone
, order
,
2739 high_wmark_pages(zone
), end_zone
, 0)) {
2742 * We are still under min water mark. This
2743 * means that we have a GFP_ATOMIC allocation
2744 * failure risk. Hurry up!
2746 if (!zone_watermark_ok_safe(zone
, order
,
2747 min_wmark_pages(zone
), end_zone
, 0))
2748 has_under_min_watermark_zone
= 1;
2751 * If a zone reaches its high watermark,
2752 * consider it to be no longer congested. It's
2753 * possible there are dirty pages backed by
2754 * congested BDIs but as pressure is relieved,
2755 * spectulatively avoid congestion waits
2757 zone_clear_flag(zone
, ZONE_CONGESTED
);
2758 if (i
<= *classzone_idx
)
2759 balanced
+= zone
->present_pages
;
2763 if (all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))
2764 break; /* kswapd: all done */
2766 * OK, kswapd is getting into trouble. Take a nap, then take
2767 * another pass across the zones.
2769 if (total_scanned
&& (priority
< DEF_PRIORITY
- 2)) {
2770 if (has_under_min_watermark_zone
)
2771 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT
);
2773 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
2777 * We do this so kswapd doesn't build up large priorities for
2778 * example when it is freeing in parallel with allocators. It
2779 * matches the direct reclaim path behaviour in terms of impact
2780 * on zone->*_priority.
2782 if (sc
.nr_reclaimed
>= SWAP_CLUSTER_MAX
)
2788 * order-0: All zones must meet high watermark for a balanced node
2789 * high-order: Balanced zones must make up at least 25% of the node
2790 * for the node to be balanced
2792 if (!(all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))) {
2798 * Fragmentation may mean that the system cannot be
2799 * rebalanced for high-order allocations in all zones.
2800 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2801 * it means the zones have been fully scanned and are still
2802 * not balanced. For high-order allocations, there is
2803 * little point trying all over again as kswapd may
2806 * Instead, recheck all watermarks at order-0 as they
2807 * are the most important. If watermarks are ok, kswapd will go
2808 * back to sleep. High-order users can still perform direct
2809 * reclaim if they wish.
2811 if (sc
.nr_reclaimed
< SWAP_CLUSTER_MAX
)
2812 order
= sc
.order
= 0;
2818 * If kswapd was reclaiming at a higher order, it has the option of
2819 * sleeping without all zones being balanced. Before it does, it must
2820 * ensure that the watermarks for order-0 on *all* zones are met and
2821 * that the congestion flags are cleared. The congestion flag must
2822 * be cleared as kswapd is the only mechanism that clears the flag
2823 * and it is potentially going to sleep here.
2826 for (i
= 0; i
<= end_zone
; i
++) {
2827 struct zone
*zone
= pgdat
->node_zones
+ i
;
2829 if (!populated_zone(zone
))
2832 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2835 /* Confirm the zone is balanced for order-0 */
2836 if (!zone_watermark_ok(zone
, 0,
2837 high_wmark_pages(zone
), 0, 0)) {
2838 order
= sc
.order
= 0;
2842 /* If balanced, clear the congested flag */
2843 zone_clear_flag(zone
, ZONE_CONGESTED
);
2844 if (i
<= *classzone_idx
)
2845 balanced
+= zone
->present_pages
;
2850 * Return the order we were reclaiming at so sleeping_prematurely()
2851 * makes a decision on the order we were last reclaiming at. However,
2852 * if another caller entered the allocator slow path while kswapd
2853 * was awake, order will remain at the higher level
2855 *classzone_idx
= end_zone
;
2859 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2864 if (freezing(current
) || kthread_should_stop())
2867 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2869 /* Try to sleep for a short interval */
2870 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2871 remaining
= schedule_timeout(HZ
/10);
2872 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2873 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2877 * After a short sleep, check if it was a premature sleep. If not, then
2878 * go fully to sleep until explicitly woken up.
2880 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2881 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
2884 * vmstat counters are not perfectly accurate and the estimated
2885 * value for counters such as NR_FREE_PAGES can deviate from the
2886 * true value by nr_online_cpus * threshold. To avoid the zone
2887 * watermarks being breached while under pressure, we reduce the
2888 * per-cpu vmstat threshold while kswapd is awake and restore
2889 * them before going back to sleep.
2891 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
2893 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
2896 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
2898 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
2900 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2904 * The background pageout daemon, started as a kernel thread
2905 * from the init process.
2907 * This basically trickles out pages so that we have _some_
2908 * free memory available even if there is no other activity
2909 * that frees anything up. This is needed for things like routing
2910 * etc, where we otherwise might have all activity going on in
2911 * asynchronous contexts that cannot page things out.
2913 * If there are applications that are active memory-allocators
2914 * (most normal use), this basically shouldn't matter.
2916 static int kswapd(void *p
)
2918 unsigned long order
, new_order
;
2919 unsigned balanced_order
;
2920 int classzone_idx
, new_classzone_idx
;
2921 int balanced_classzone_idx
;
2922 pg_data_t
*pgdat
= (pg_data_t
*)p
;
2923 struct task_struct
*tsk
= current
;
2925 struct reclaim_state reclaim_state
= {
2926 .reclaimed_slab
= 0,
2928 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
2930 lockdep_set_current_reclaim_state(GFP_KERNEL
);
2932 if (!cpumask_empty(cpumask
))
2933 set_cpus_allowed_ptr(tsk
, cpumask
);
2934 current
->reclaim_state
= &reclaim_state
;
2937 * Tell the memory management that we're a "memory allocator",
2938 * and that if we need more memory we should get access to it
2939 * regardless (see "__alloc_pages()"). "kswapd" should
2940 * never get caught in the normal page freeing logic.
2942 * (Kswapd normally doesn't need memory anyway, but sometimes
2943 * you need a small amount of memory in order to be able to
2944 * page out something else, and this flag essentially protects
2945 * us from recursively trying to free more memory as we're
2946 * trying to free the first piece of memory in the first place).
2948 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
2951 order
= new_order
= 0;
2953 classzone_idx
= new_classzone_idx
= pgdat
->nr_zones
- 1;
2954 balanced_classzone_idx
= classzone_idx
;
2959 * If the last balance_pgdat was unsuccessful it's unlikely a
2960 * new request of a similar or harder type will succeed soon
2961 * so consider going to sleep on the basis we reclaimed at
2963 if (balanced_classzone_idx
>= new_classzone_idx
&&
2964 balanced_order
== new_order
) {
2965 new_order
= pgdat
->kswapd_max_order
;
2966 new_classzone_idx
= pgdat
->classzone_idx
;
2967 pgdat
->kswapd_max_order
= 0;
2968 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
2971 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
2973 * Don't sleep if someone wants a larger 'order'
2974 * allocation or has tigher zone constraints
2977 classzone_idx
= new_classzone_idx
;
2979 kswapd_try_to_sleep(pgdat
, balanced_order
,
2980 balanced_classzone_idx
);
2981 order
= pgdat
->kswapd_max_order
;
2982 classzone_idx
= pgdat
->classzone_idx
;
2984 new_classzone_idx
= classzone_idx
;
2985 pgdat
->kswapd_max_order
= 0;
2986 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
2989 ret
= try_to_freeze();
2990 if (kthread_should_stop())
2994 * We can speed up thawing tasks if we don't call balance_pgdat
2995 * after returning from the refrigerator
2998 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
2999 balanced_classzone_idx
= classzone_idx
;
3000 balanced_order
= balance_pgdat(pgdat
, order
,
3001 &balanced_classzone_idx
);
3008 * A zone is low on free memory, so wake its kswapd task to service it.
3010 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
3014 if (!populated_zone(zone
))
3017 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
3019 pgdat
= zone
->zone_pgdat
;
3020 if (pgdat
->kswapd_max_order
< order
) {
3021 pgdat
->kswapd_max_order
= order
;
3022 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
3024 if (!waitqueue_active(&pgdat
->kswapd_wait
))
3026 if (zone_watermark_ok_safe(zone
, order
, low_wmark_pages(zone
), 0, 0))
3029 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
3030 wake_up_interruptible(&pgdat
->kswapd_wait
);
3034 * The reclaimable count would be mostly accurate.
3035 * The less reclaimable pages may be
3036 * - mlocked pages, which will be moved to unevictable list when encountered
3037 * - mapped pages, which may require several travels to be reclaimed
3038 * - dirty pages, which is not "instantly" reclaimable
3040 unsigned long global_reclaimable_pages(void)
3044 nr
= global_page_state(NR_ACTIVE_FILE
) +
3045 global_page_state(NR_INACTIVE_FILE
);
3047 if (nr_swap_pages
> 0)
3048 nr
+= global_page_state(NR_ACTIVE_ANON
) +
3049 global_page_state(NR_INACTIVE_ANON
);
3054 unsigned long zone_reclaimable_pages(struct zone
*zone
)
3058 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
3059 zone_page_state(zone
, NR_INACTIVE_FILE
);
3061 if (nr_swap_pages
> 0)
3062 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
3063 zone_page_state(zone
, NR_INACTIVE_ANON
);
3068 #ifdef CONFIG_HIBERNATION
3070 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3073 * Rather than trying to age LRUs the aim is to preserve the overall
3074 * LRU order by reclaiming preferentially
3075 * inactive > active > active referenced > active mapped
3077 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
3079 struct reclaim_state reclaim_state
;
3080 struct scan_control sc
= {
3081 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
3085 .nr_to_reclaim
= nr_to_reclaim
,
3086 .hibernation_mode
= 1,
3089 struct shrink_control shrink
= {
3090 .gfp_mask
= sc
.gfp_mask
,
3092 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3093 struct task_struct
*p
= current
;
3094 unsigned long nr_reclaimed
;
3096 p
->flags
|= PF_MEMALLOC
;
3097 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
3098 reclaim_state
.reclaimed_slab
= 0;
3099 p
->reclaim_state
= &reclaim_state
;
3101 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
3103 p
->reclaim_state
= NULL
;
3104 lockdep_clear_current_reclaim_state();
3105 p
->flags
&= ~PF_MEMALLOC
;
3107 return nr_reclaimed
;
3109 #endif /* CONFIG_HIBERNATION */
3111 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3112 not required for correctness. So if the last cpu in a node goes
3113 away, we get changed to run anywhere: as the first one comes back,
3114 restore their cpu bindings. */
3115 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
3116 unsigned long action
, void *hcpu
)
3120 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
3121 for_each_node_state(nid
, N_HIGH_MEMORY
) {
3122 pg_data_t
*pgdat
= NODE_DATA(nid
);
3123 const struct cpumask
*mask
;
3125 mask
= cpumask_of_node(pgdat
->node_id
);
3127 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3128 /* One of our CPUs online: restore mask */
3129 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
3136 * This kswapd start function will be called by init and node-hot-add.
3137 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3139 int kswapd_run(int nid
)
3141 pg_data_t
*pgdat
= NODE_DATA(nid
);
3147 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
3148 if (IS_ERR(pgdat
->kswapd
)) {
3149 /* failure at boot is fatal */
3150 BUG_ON(system_state
== SYSTEM_BOOTING
);
3151 printk("Failed to start kswapd on node %d\n",nid
);
3158 * Called by memory hotplug when all memory in a node is offlined.
3160 void kswapd_stop(int nid
)
3162 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
3165 kthread_stop(kswapd
);
3168 static int __init
kswapd_init(void)
3173 for_each_node_state(nid
, N_HIGH_MEMORY
)
3175 hotcpu_notifier(cpu_callback
, 0);
3179 module_init(kswapd_init
)
3185 * If non-zero call zone_reclaim when the number of free pages falls below
3188 int zone_reclaim_mode __read_mostly
;
3190 #define RECLAIM_OFF 0
3191 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3192 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3193 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3196 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3197 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3200 #define ZONE_RECLAIM_PRIORITY 4
3203 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3206 int sysctl_min_unmapped_ratio
= 1;
3209 * If the number of slab pages in a zone grows beyond this percentage then
3210 * slab reclaim needs to occur.
3212 int sysctl_min_slab_ratio
= 5;
3214 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
3216 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
3217 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
3218 zone_page_state(zone
, NR_ACTIVE_FILE
);
3221 * It's possible for there to be more file mapped pages than
3222 * accounted for by the pages on the file LRU lists because
3223 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3225 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
3228 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3229 static long zone_pagecache_reclaimable(struct zone
*zone
)
3231 long nr_pagecache_reclaimable
;
3235 * If RECLAIM_SWAP is set, then all file pages are considered
3236 * potentially reclaimable. Otherwise, we have to worry about
3237 * pages like swapcache and zone_unmapped_file_pages() provides
3240 if (zone_reclaim_mode
& RECLAIM_SWAP
)
3241 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
3243 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
3245 /* If we can't clean pages, remove dirty pages from consideration */
3246 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
3247 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
3249 /* Watch for any possible underflows due to delta */
3250 if (unlikely(delta
> nr_pagecache_reclaimable
))
3251 delta
= nr_pagecache_reclaimable
;
3253 return nr_pagecache_reclaimable
- delta
;
3257 * Try to free up some pages from this zone through reclaim.
3259 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3261 /* Minimum pages needed in order to stay on node */
3262 const unsigned long nr_pages
= 1 << order
;
3263 struct task_struct
*p
= current
;
3264 struct reclaim_state reclaim_state
;
3266 struct scan_control sc
= {
3267 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
3268 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
3270 .nr_to_reclaim
= max_t(unsigned long, nr_pages
,
3272 .gfp_mask
= gfp_mask
,
3275 struct shrink_control shrink
= {
3276 .gfp_mask
= sc
.gfp_mask
,
3278 unsigned long nr_slab_pages0
, nr_slab_pages1
;
3282 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3283 * and we also need to be able to write out pages for RECLAIM_WRITE
3286 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
3287 lockdep_set_current_reclaim_state(gfp_mask
);
3288 reclaim_state
.reclaimed_slab
= 0;
3289 p
->reclaim_state
= &reclaim_state
;
3291 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
3293 * Free memory by calling shrink zone with increasing
3294 * priorities until we have enough memory freed.
3296 priority
= ZONE_RECLAIM_PRIORITY
;
3298 shrink_zone(priority
, zone
, &sc
);
3300 } while (priority
>= 0 && sc
.nr_reclaimed
< nr_pages
);
3303 nr_slab_pages0
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3304 if (nr_slab_pages0
> zone
->min_slab_pages
) {
3306 * shrink_slab() does not currently allow us to determine how
3307 * many pages were freed in this zone. So we take the current
3308 * number of slab pages and shake the slab until it is reduced
3309 * by the same nr_pages that we used for reclaiming unmapped
3312 * Note that shrink_slab will free memory on all zones and may
3316 unsigned long lru_pages
= zone_reclaimable_pages(zone
);
3318 /* No reclaimable slab or very low memory pressure */
3319 if (!shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
))
3322 /* Freed enough memory */
3323 nr_slab_pages1
= zone_page_state(zone
,
3324 NR_SLAB_RECLAIMABLE
);
3325 if (nr_slab_pages1
+ nr_pages
<= nr_slab_pages0
)
3330 * Update nr_reclaimed by the number of slab pages we
3331 * reclaimed from this zone.
3333 nr_slab_pages1
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3334 if (nr_slab_pages1
< nr_slab_pages0
)
3335 sc
.nr_reclaimed
+= nr_slab_pages0
- nr_slab_pages1
;
3338 p
->reclaim_state
= NULL
;
3339 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3340 lockdep_clear_current_reclaim_state();
3341 return sc
.nr_reclaimed
>= nr_pages
;
3344 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3350 * Zone reclaim reclaims unmapped file backed pages and
3351 * slab pages if we are over the defined limits.
3353 * A small portion of unmapped file backed pages is needed for
3354 * file I/O otherwise pages read by file I/O will be immediately
3355 * thrown out if the zone is overallocated. So we do not reclaim
3356 * if less than a specified percentage of the zone is used by
3357 * unmapped file backed pages.
3359 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3360 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3361 return ZONE_RECLAIM_FULL
;
3363 if (zone
->all_unreclaimable
)
3364 return ZONE_RECLAIM_FULL
;
3367 * Do not scan if the allocation should not be delayed.
3369 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3370 return ZONE_RECLAIM_NOSCAN
;
3373 * Only run zone reclaim on the local zone or on zones that do not
3374 * have associated processors. This will favor the local processor
3375 * over remote processors and spread off node memory allocations
3376 * as wide as possible.
3378 node_id
= zone_to_nid(zone
);
3379 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3380 return ZONE_RECLAIM_NOSCAN
;
3382 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
3383 return ZONE_RECLAIM_NOSCAN
;
3385 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3386 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
3389 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3396 * page_evictable - test whether a page is evictable
3397 * @page: the page to test
3398 * @vma: the VMA in which the page is or will be mapped, may be NULL
3400 * Test whether page is evictable--i.e., should be placed on active/inactive
3401 * lists vs unevictable list. The vma argument is !NULL when called from the
3402 * fault path to determine how to instantate a new page.
3404 * Reasons page might not be evictable:
3405 * (1) page's mapping marked unevictable
3406 * (2) page is part of an mlocked VMA
3409 int page_evictable(struct page
*page
, struct vm_area_struct
*vma
)
3412 if (mapping_unevictable(page_mapping(page
)))
3415 if (PageMlocked(page
) || (vma
&& is_mlocked_vma(vma
, page
)))
3422 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3423 * @page: page to check evictability and move to appropriate lru list
3424 * @zone: zone page is in
3426 * Checks a page for evictability and moves the page to the appropriate
3429 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3430 * have PageUnevictable set.
3432 static void check_move_unevictable_page(struct page
*page
, struct zone
*zone
)
3434 struct lruvec
*lruvec
;
3436 VM_BUG_ON(PageActive(page
));
3438 ClearPageUnevictable(page
);
3439 if (page_evictable(page
, NULL
)) {
3440 enum lru_list l
= page_lru_base_type(page
);
3442 __dec_zone_state(zone
, NR_UNEVICTABLE
);
3443 lruvec
= mem_cgroup_lru_move_lists(zone
, page
,
3444 LRU_UNEVICTABLE
, l
);
3445 list_move(&page
->lru
, &lruvec
->lists
[l
]);
3446 __inc_zone_state(zone
, NR_INACTIVE_ANON
+ l
);
3447 __count_vm_event(UNEVICTABLE_PGRESCUED
);
3450 * rotate unevictable list
3452 SetPageUnevictable(page
);
3453 lruvec
= mem_cgroup_lru_move_lists(zone
, page
, LRU_UNEVICTABLE
,
3455 list_move(&page
->lru
, &lruvec
->lists
[LRU_UNEVICTABLE
]);
3456 if (page_evictable(page
, NULL
))
3462 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3463 * @mapping: struct address_space to scan for evictable pages
3465 * Scan all pages in mapping. Check unevictable pages for
3466 * evictability and move them to the appropriate zone lru list.
3468 void scan_mapping_unevictable_pages(struct address_space
*mapping
)
3471 pgoff_t end
= (i_size_read(mapping
->host
) + PAGE_CACHE_SIZE
- 1) >>
3474 struct pagevec pvec
;
3476 if (mapping
->nrpages
== 0)
3479 pagevec_init(&pvec
, 0);
3480 while (next
< end
&&
3481 pagevec_lookup(&pvec
, mapping
, next
, PAGEVEC_SIZE
)) {
3487 for (i
= 0; i
< pagevec_count(&pvec
); i
++) {
3488 struct page
*page
= pvec
.pages
[i
];
3489 pgoff_t page_index
= page
->index
;
3490 struct zone
*pagezone
= page_zone(page
);
3493 if (page_index
> next
)
3497 if (pagezone
!= zone
) {
3499 spin_unlock_irq(&zone
->lru_lock
);
3501 spin_lock_irq(&zone
->lru_lock
);
3504 if (PageLRU(page
) && PageUnevictable(page
))
3505 check_move_unevictable_page(page
, zone
);
3508 spin_unlock_irq(&zone
->lru_lock
);
3509 pagevec_release(&pvec
);
3511 count_vm_events(UNEVICTABLE_PGSCANNED
, pg_scanned
);
3516 static void warn_scan_unevictable_pages(void)
3518 printk_once(KERN_WARNING
3519 "%s: The scan_unevictable_pages sysctl/node-interface has been "
3520 "disabled for lack of a legitimate use case. If you have "
3521 "one, please send an email to linux-mm@kvack.org.\n",
3526 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3527 * all nodes' unevictable lists for evictable pages
3529 unsigned long scan_unevictable_pages
;
3531 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
3532 void __user
*buffer
,
3533 size_t *length
, loff_t
*ppos
)
3535 warn_scan_unevictable_pages();
3536 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
3537 scan_unevictable_pages
= 0;
3543 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3544 * a specified node's per zone unevictable lists for evictable pages.
3547 static ssize_t
read_scan_unevictable_node(struct device
*dev
,
3548 struct device_attribute
*attr
,
3551 warn_scan_unevictable_pages();
3552 return sprintf(buf
, "0\n"); /* always zero; should fit... */
3555 static ssize_t
write_scan_unevictable_node(struct device
*dev
,
3556 struct device_attribute
*attr
,
3557 const char *buf
, size_t count
)
3559 warn_scan_unevictable_pages();
3564 static DEVICE_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
3565 read_scan_unevictable_node
,
3566 write_scan_unevictable_node
);
3568 int scan_unevictable_register_node(struct node
*node
)
3570 return device_create_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);
3573 void scan_unevictable_unregister_node(struct node
*node
)
3575 device_remove_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);