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
;
106 /* Which cgroup do we reclaim from */
107 struct mem_cgroup
*mem_cgroup
;
110 * Nodemask of nodes allowed by the caller. If NULL, all nodes
113 nodemask_t
*nodemask
;
116 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
118 #ifdef ARCH_HAS_PREFETCH
119 #define prefetch_prev_lru_page(_page, _base, _field) \
121 if ((_page)->lru.prev != _base) { \
124 prev = lru_to_page(&(_page->lru)); \
125 prefetch(&prev->_field); \
129 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
132 #ifdef ARCH_HAS_PREFETCHW
133 #define prefetchw_prev_lru_page(_page, _base, _field) \
135 if ((_page)->lru.prev != _base) { \
138 prev = lru_to_page(&(_page->lru)); \
139 prefetchw(&prev->_field); \
143 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
147 * From 0 .. 100. Higher means more swappy.
149 int vm_swappiness
= 60;
150 long vm_total_pages
; /* The total number of pages which the VM controls */
152 static LIST_HEAD(shrinker_list
);
153 static DECLARE_RWSEM(shrinker_rwsem
);
155 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
156 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
158 #define scanning_global_lru(sc) (1)
161 static struct zone_reclaim_stat
*get_reclaim_stat(struct zone
*zone
,
162 struct scan_control
*sc
)
164 if (!scanning_global_lru(sc
))
165 return mem_cgroup_get_reclaim_stat(sc
->mem_cgroup
, zone
);
167 return &zone
->reclaim_stat
;
170 static unsigned long zone_nr_lru_pages(struct zone
*zone
,
171 struct scan_control
*sc
, enum lru_list lru
)
173 if (!scanning_global_lru(sc
))
174 return mem_cgroup_zone_nr_lru_pages(sc
->mem_cgroup
,
175 zone_to_nid(zone
), zone_idx(zone
), BIT(lru
));
177 return zone_page_state(zone
, NR_LRU_BASE
+ lru
);
182 * Add a shrinker callback to be called from the vm
184 void register_shrinker(struct shrinker
*shrinker
)
186 atomic_long_set(&shrinker
->nr_in_batch
, 0);
187 down_write(&shrinker_rwsem
);
188 list_add_tail(&shrinker
->list
, &shrinker_list
);
189 up_write(&shrinker_rwsem
);
191 EXPORT_SYMBOL(register_shrinker
);
196 void unregister_shrinker(struct shrinker
*shrinker
)
198 down_write(&shrinker_rwsem
);
199 list_del(&shrinker
->list
);
200 up_write(&shrinker_rwsem
);
202 EXPORT_SYMBOL(unregister_shrinker
);
204 static inline int do_shrinker_shrink(struct shrinker
*shrinker
,
205 struct shrink_control
*sc
,
206 unsigned long nr_to_scan
)
208 sc
->nr_to_scan
= nr_to_scan
;
209 return (*shrinker
->shrink
)(shrinker
, sc
);
212 #define SHRINK_BATCH 128
214 * Call the shrink functions to age shrinkable caches
216 * Here we assume it costs one seek to replace a lru page and that it also
217 * takes a seek to recreate a cache object. With this in mind we age equal
218 * percentages of the lru and ageable caches. This should balance the seeks
219 * generated by these structures.
221 * If the vm encountered mapped pages on the LRU it increase the pressure on
222 * slab to avoid swapping.
224 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
226 * `lru_pages' represents the number of on-LRU pages in all the zones which
227 * are eligible for the caller's allocation attempt. It is used for balancing
228 * slab reclaim versus page reclaim.
230 * Returns the number of slab objects which we shrunk.
232 unsigned long shrink_slab(struct shrink_control
*shrink
,
233 unsigned long nr_pages_scanned
,
234 unsigned long lru_pages
)
236 struct shrinker
*shrinker
;
237 unsigned long ret
= 0;
239 if (nr_pages_scanned
== 0)
240 nr_pages_scanned
= SWAP_CLUSTER_MAX
;
242 if (!down_read_trylock(&shrinker_rwsem
)) {
243 /* Assume we'll be able to shrink next time */
248 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
249 unsigned long long delta
;
255 long batch_size
= shrinker
->batch
? shrinker
->batch
258 max_pass
= do_shrinker_shrink(shrinker
, shrink
, 0);
263 * copy the current shrinker scan count into a local variable
264 * and zero it so that other concurrent shrinker invocations
265 * don't also do this scanning work.
267 nr
= atomic_long_xchg(&shrinker
->nr_in_batch
, 0);
270 delta
= (4 * nr_pages_scanned
) / shrinker
->seeks
;
272 do_div(delta
, lru_pages
+ 1);
274 if (total_scan
< 0) {
275 printk(KERN_ERR
"shrink_slab: %pF negative objects to "
277 shrinker
->shrink
, total_scan
);
278 total_scan
= max_pass
;
282 * We need to avoid excessive windup on filesystem shrinkers
283 * due to large numbers of GFP_NOFS allocations causing the
284 * shrinkers to return -1 all the time. This results in a large
285 * nr being built up so when a shrink that can do some work
286 * comes along it empties the entire cache due to nr >>>
287 * max_pass. This is bad for sustaining a working set in
290 * Hence only allow the shrinker to scan the entire cache when
291 * a large delta change is calculated directly.
293 if (delta
< max_pass
/ 4)
294 total_scan
= min(total_scan
, max_pass
/ 2);
297 * Avoid risking looping forever due to too large nr value:
298 * never try to free more than twice the estimate number of
301 if (total_scan
> max_pass
* 2)
302 total_scan
= max_pass
* 2;
304 trace_mm_shrink_slab_start(shrinker
, shrink
, nr
,
305 nr_pages_scanned
, lru_pages
,
306 max_pass
, delta
, total_scan
);
308 while (total_scan
>= batch_size
) {
311 nr_before
= do_shrinker_shrink(shrinker
, shrink
, 0);
312 shrink_ret
= do_shrinker_shrink(shrinker
, shrink
,
314 if (shrink_ret
== -1)
316 if (shrink_ret
< nr_before
)
317 ret
+= nr_before
- shrink_ret
;
318 count_vm_events(SLABS_SCANNED
, batch_size
);
319 total_scan
-= batch_size
;
325 * move the unused scan count back into the shrinker in a
326 * manner that handles concurrent updates. If we exhausted the
327 * scan, there is no need to do an update.
330 new_nr
= atomic_long_add_return(total_scan
,
331 &shrinker
->nr_in_batch
);
333 new_nr
= atomic_long_read(&shrinker
->nr_in_batch
);
335 trace_mm_shrink_slab_end(shrinker
, shrink_ret
, nr
, new_nr
);
337 up_read(&shrinker_rwsem
);
343 static void set_reclaim_mode(int priority
, struct scan_control
*sc
,
346 reclaim_mode_t syncmode
= sync
? RECLAIM_MODE_SYNC
: RECLAIM_MODE_ASYNC
;
349 * Initially assume we are entering either lumpy reclaim or
350 * reclaim/compaction.Depending on the order, we will either set the
351 * sync mode or just reclaim order-0 pages later.
353 if (COMPACTION_BUILD
)
354 sc
->reclaim_mode
= RECLAIM_MODE_COMPACTION
;
356 sc
->reclaim_mode
= RECLAIM_MODE_LUMPYRECLAIM
;
359 * Avoid using lumpy reclaim or reclaim/compaction if possible by
360 * restricting when its set to either costly allocations or when
361 * under memory pressure
363 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
364 sc
->reclaim_mode
|= syncmode
;
365 else if (sc
->order
&& priority
< DEF_PRIORITY
- 2)
366 sc
->reclaim_mode
|= syncmode
;
368 sc
->reclaim_mode
= RECLAIM_MODE_SINGLE
| RECLAIM_MODE_ASYNC
;
371 static void reset_reclaim_mode(struct scan_control
*sc
)
373 sc
->reclaim_mode
= RECLAIM_MODE_SINGLE
| RECLAIM_MODE_ASYNC
;
376 static inline int is_page_cache_freeable(struct page
*page
)
379 * A freeable page cache page is referenced only by the caller
380 * that isolated the page, the page cache radix tree and
381 * optional buffer heads at page->private.
383 return page_count(page
) - page_has_private(page
) == 2;
386 static int may_write_to_queue(struct backing_dev_info
*bdi
,
387 struct scan_control
*sc
)
389 if (current
->flags
& PF_SWAPWRITE
)
391 if (!bdi_write_congested(bdi
))
393 if (bdi
== current
->backing_dev_info
)
396 /* lumpy reclaim for hugepage often need a lot of write */
397 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
403 * We detected a synchronous write error writing a page out. Probably
404 * -ENOSPC. We need to propagate that into the address_space for a subsequent
405 * fsync(), msync() or close().
407 * The tricky part is that after writepage we cannot touch the mapping: nothing
408 * prevents it from being freed up. But we have a ref on the page and once
409 * that page is locked, the mapping is pinned.
411 * We're allowed to run sleeping lock_page() here because we know the caller has
414 static void handle_write_error(struct address_space
*mapping
,
415 struct page
*page
, int error
)
418 if (page_mapping(page
) == mapping
)
419 mapping_set_error(mapping
, error
);
423 /* possible outcome of pageout() */
425 /* failed to write page out, page is locked */
427 /* move page to the active list, page is locked */
429 /* page has been sent to the disk successfully, page is unlocked */
431 /* page is clean and locked */
436 * pageout is called by shrink_page_list() for each dirty page.
437 * Calls ->writepage().
439 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
440 struct scan_control
*sc
)
443 * If the page is dirty, only perform writeback if that write
444 * will be non-blocking. To prevent this allocation from being
445 * stalled by pagecache activity. But note that there may be
446 * stalls if we need to run get_block(). We could test
447 * PagePrivate for that.
449 * If this process is currently in __generic_file_aio_write() against
450 * this page's queue, we can perform writeback even if that
453 * If the page is swapcache, write it back even if that would
454 * block, for some throttling. This happens by accident, because
455 * swap_backing_dev_info is bust: it doesn't reflect the
456 * congestion state of the swapdevs. Easy to fix, if needed.
458 if (!is_page_cache_freeable(page
))
462 * Some data journaling orphaned pages can have
463 * page->mapping == NULL while being dirty with clean buffers.
465 if (page_has_private(page
)) {
466 if (try_to_free_buffers(page
)) {
467 ClearPageDirty(page
);
468 printk("%s: orphaned page\n", __func__
);
474 if (mapping
->a_ops
->writepage
== NULL
)
475 return PAGE_ACTIVATE
;
476 if (!may_write_to_queue(mapping
->backing_dev_info
, sc
))
479 if (clear_page_dirty_for_io(page
)) {
481 struct writeback_control wbc
= {
482 .sync_mode
= WB_SYNC_NONE
,
483 .nr_to_write
= SWAP_CLUSTER_MAX
,
485 .range_end
= LLONG_MAX
,
489 SetPageReclaim(page
);
490 res
= mapping
->a_ops
->writepage(page
, &wbc
);
492 handle_write_error(mapping
, page
, res
);
493 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
494 ClearPageReclaim(page
);
495 return PAGE_ACTIVATE
;
498 if (!PageWriteback(page
)) {
499 /* synchronous write or broken a_ops? */
500 ClearPageReclaim(page
);
502 trace_mm_vmscan_writepage(page
,
503 trace_reclaim_flags(page
, sc
->reclaim_mode
));
504 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
512 * Same as remove_mapping, but if the page is removed from the mapping, it
513 * gets returned with a refcount of 0.
515 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
)
517 BUG_ON(!PageLocked(page
));
518 BUG_ON(mapping
!= page_mapping(page
));
520 spin_lock_irq(&mapping
->tree_lock
);
522 * The non racy check for a busy page.
524 * Must be careful with the order of the tests. When someone has
525 * a ref to the page, it may be possible that they dirty it then
526 * drop the reference. So if PageDirty is tested before page_count
527 * here, then the following race may occur:
529 * get_user_pages(&page);
530 * [user mapping goes away]
532 * !PageDirty(page) [good]
533 * SetPageDirty(page);
535 * !page_count(page) [good, discard it]
537 * [oops, our write_to data is lost]
539 * Reversing the order of the tests ensures such a situation cannot
540 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
541 * load is not satisfied before that of page->_count.
543 * Note that if SetPageDirty is always performed via set_page_dirty,
544 * and thus under tree_lock, then this ordering is not required.
546 if (!page_freeze_refs(page
, 2))
548 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
549 if (unlikely(PageDirty(page
))) {
550 page_unfreeze_refs(page
, 2);
554 if (PageSwapCache(page
)) {
555 swp_entry_t swap
= { .val
= page_private(page
) };
556 __delete_from_swap_cache(page
);
557 spin_unlock_irq(&mapping
->tree_lock
);
558 swapcache_free(swap
, page
);
560 void (*freepage
)(struct page
*);
562 freepage
= mapping
->a_ops
->freepage
;
564 __delete_from_page_cache(page
);
565 spin_unlock_irq(&mapping
->tree_lock
);
566 mem_cgroup_uncharge_cache_page(page
);
568 if (freepage
!= NULL
)
575 spin_unlock_irq(&mapping
->tree_lock
);
580 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
581 * someone else has a ref on the page, abort and return 0. If it was
582 * successfully detached, return 1. Assumes the caller has a single ref on
585 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
587 if (__remove_mapping(mapping
, page
)) {
589 * Unfreezing the refcount with 1 rather than 2 effectively
590 * drops the pagecache ref for us without requiring another
593 page_unfreeze_refs(page
, 1);
600 * putback_lru_page - put previously isolated page onto appropriate LRU list
601 * @page: page to be put back to appropriate lru list
603 * Add previously isolated @page to appropriate LRU list.
604 * Page may still be unevictable for other reasons.
606 * lru_lock must not be held, interrupts must be enabled.
608 void putback_lru_page(struct page
*page
)
611 int active
= !!TestClearPageActive(page
);
612 int was_unevictable
= PageUnevictable(page
);
614 VM_BUG_ON(PageLRU(page
));
617 ClearPageUnevictable(page
);
619 if (page_evictable(page
, NULL
)) {
621 * For evictable pages, we can use the cache.
622 * In event of a race, worst case is we end up with an
623 * unevictable page on [in]active list.
624 * We know how to handle that.
626 lru
= active
+ page_lru_base_type(page
);
627 lru_cache_add_lru(page
, lru
);
630 * Put unevictable pages directly on zone's unevictable
633 lru
= LRU_UNEVICTABLE
;
634 add_page_to_unevictable_list(page
);
636 * When racing with an mlock or AS_UNEVICTABLE clearing
637 * (page is unlocked) make sure that if the other thread
638 * does not observe our setting of PG_lru and fails
639 * isolation/check_move_unevictable_page,
640 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
641 * the page back to the evictable list.
643 * The other side is TestClearPageMlocked() or shmem_lock().
649 * page's status can change while we move it among lru. If an evictable
650 * page is on unevictable list, it never be freed. To avoid that,
651 * check after we added it to the list, again.
653 if (lru
== LRU_UNEVICTABLE
&& page_evictable(page
, NULL
)) {
654 if (!isolate_lru_page(page
)) {
658 /* This means someone else dropped this page from LRU
659 * So, it will be freed or putback to LRU again. There is
660 * nothing to do here.
664 if (was_unevictable
&& lru
!= LRU_UNEVICTABLE
)
665 count_vm_event(UNEVICTABLE_PGRESCUED
);
666 else if (!was_unevictable
&& lru
== LRU_UNEVICTABLE
)
667 count_vm_event(UNEVICTABLE_PGCULLED
);
669 put_page(page
); /* drop ref from isolate */
672 enum page_references
{
674 PAGEREF_RECLAIM_CLEAN
,
679 static enum page_references
page_check_references(struct page
*page
,
680 struct scan_control
*sc
)
682 int referenced_ptes
, referenced_page
;
683 unsigned long vm_flags
;
685 referenced_ptes
= page_referenced(page
, 1, sc
->mem_cgroup
, &vm_flags
);
686 referenced_page
= TestClearPageReferenced(page
);
688 /* Lumpy reclaim - ignore references */
689 if (sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
)
690 return PAGEREF_RECLAIM
;
693 * Mlock lost the isolation race with us. Let try_to_unmap()
694 * move the page to the unevictable list.
696 if (vm_flags
& VM_LOCKED
)
697 return PAGEREF_RECLAIM
;
699 if (referenced_ptes
) {
701 return PAGEREF_ACTIVATE
;
703 * All mapped pages start out with page table
704 * references from the instantiating fault, so we need
705 * to look twice if a mapped file page is used more
708 * Mark it and spare it for another trip around the
709 * inactive list. Another page table reference will
710 * lead to its activation.
712 * Note: the mark is set for activated pages as well
713 * so that recently deactivated but used pages are
716 SetPageReferenced(page
);
718 if (referenced_page
|| referenced_ptes
> 1)
719 return PAGEREF_ACTIVATE
;
722 * Activate file-backed executable pages after first usage.
724 if (vm_flags
& VM_EXEC
)
725 return PAGEREF_ACTIVATE
;
730 /* Reclaim if clean, defer dirty pages to writeback */
731 if (referenced_page
&& !PageSwapBacked(page
))
732 return PAGEREF_RECLAIM_CLEAN
;
734 return PAGEREF_RECLAIM
;
738 * shrink_page_list() returns the number of reclaimed pages
740 static unsigned long shrink_page_list(struct list_head
*page_list
,
742 struct scan_control
*sc
,
744 unsigned long *ret_nr_dirty
,
745 unsigned long *ret_nr_writeback
)
747 LIST_HEAD(ret_pages
);
748 LIST_HEAD(free_pages
);
750 unsigned long nr_dirty
= 0;
751 unsigned long nr_congested
= 0;
752 unsigned long nr_reclaimed
= 0;
753 unsigned long nr_writeback
= 0;
757 while (!list_empty(page_list
)) {
758 enum page_references references
;
759 struct address_space
*mapping
;
765 page
= lru_to_page(page_list
);
766 list_del(&page
->lru
);
768 if (!trylock_page(page
))
771 VM_BUG_ON(PageActive(page
));
772 VM_BUG_ON(page_zone(page
) != zone
);
776 if (unlikely(!page_evictable(page
, NULL
)))
779 if (!sc
->may_unmap
&& page_mapped(page
))
782 /* Double the slab pressure for mapped and swapcache pages */
783 if (page_mapped(page
) || PageSwapCache(page
))
786 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
787 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
789 if (PageWriteback(page
)) {
792 * Synchronous reclaim cannot queue pages for
793 * writeback due to the possibility of stack overflow
794 * but if it encounters a page under writeback, wait
795 * for the IO to complete.
797 if ((sc
->reclaim_mode
& RECLAIM_MODE_SYNC
) &&
799 wait_on_page_writeback(page
);
806 references
= page_check_references(page
, sc
);
807 switch (references
) {
808 case PAGEREF_ACTIVATE
:
809 goto activate_locked
;
812 case PAGEREF_RECLAIM
:
813 case PAGEREF_RECLAIM_CLEAN
:
814 ; /* try to reclaim the page below */
818 * Anonymous process memory has backing store?
819 * Try to allocate it some swap space here.
821 if (PageAnon(page
) && !PageSwapCache(page
)) {
822 if (!(sc
->gfp_mask
& __GFP_IO
))
824 if (!add_to_swap(page
))
825 goto activate_locked
;
829 mapping
= page_mapping(page
);
832 * The page is mapped into the page tables of one or more
833 * processes. Try to unmap it here.
835 if (page_mapped(page
) && mapping
) {
836 switch (try_to_unmap(page
, TTU_UNMAP
)) {
838 goto activate_locked
;
844 ; /* try to free the page below */
848 if (PageDirty(page
)) {
852 * Only kswapd can writeback filesystem pages to
853 * avoid risk of stack overflow but do not writeback
854 * unless under significant pressure.
856 if (page_is_file_cache(page
) &&
857 (!current_is_kswapd() || priority
>= DEF_PRIORITY
- 2)) {
859 * Immediately reclaim when written back.
860 * Similar in principal to deactivate_page()
861 * except we already have the page isolated
862 * and know it's dirty
864 inc_zone_page_state(page
, NR_VMSCAN_IMMEDIATE
);
865 SetPageReclaim(page
);
870 if (references
== PAGEREF_RECLAIM_CLEAN
)
874 if (!sc
->may_writepage
)
877 /* Page is dirty, try to write it out here */
878 switch (pageout(page
, mapping
, sc
)) {
883 goto activate_locked
;
885 if (PageWriteback(page
))
891 * A synchronous write - probably a ramdisk. Go
892 * ahead and try to reclaim the page.
894 if (!trylock_page(page
))
896 if (PageDirty(page
) || PageWriteback(page
))
898 mapping
= page_mapping(page
);
900 ; /* try to free the page below */
905 * If the page has buffers, try to free the buffer mappings
906 * associated with this page. If we succeed we try to free
909 * We do this even if the page is PageDirty().
910 * try_to_release_page() does not perform I/O, but it is
911 * possible for a page to have PageDirty set, but it is actually
912 * clean (all its buffers are clean). This happens if the
913 * buffers were written out directly, with submit_bh(). ext3
914 * will do this, as well as the blockdev mapping.
915 * try_to_release_page() will discover that cleanness and will
916 * drop the buffers and mark the page clean - it can be freed.
918 * Rarely, pages can have buffers and no ->mapping. These are
919 * the pages which were not successfully invalidated in
920 * truncate_complete_page(). We try to drop those buffers here
921 * and if that worked, and the page is no longer mapped into
922 * process address space (page_count == 1) it can be freed.
923 * Otherwise, leave the page on the LRU so it is swappable.
925 if (page_has_private(page
)) {
926 if (!try_to_release_page(page
, sc
->gfp_mask
))
927 goto activate_locked
;
928 if (!mapping
&& page_count(page
) == 1) {
930 if (put_page_testzero(page
))
934 * rare race with speculative reference.
935 * the speculative reference will free
936 * this page shortly, so we may
937 * increment nr_reclaimed here (and
938 * leave it off the LRU).
946 if (!mapping
|| !__remove_mapping(mapping
, page
))
950 * At this point, we have no other references and there is
951 * no way to pick any more up (removed from LRU, removed
952 * from pagecache). Can use non-atomic bitops now (and
953 * we obviously don't have to worry about waking up a process
954 * waiting on the page lock, because there are no references.
956 __clear_page_locked(page
);
961 * Is there need to periodically free_page_list? It would
962 * appear not as the counts should be low
964 list_add(&page
->lru
, &free_pages
);
968 if (PageSwapCache(page
))
969 try_to_free_swap(page
);
971 putback_lru_page(page
);
972 reset_reclaim_mode(sc
);
976 /* Not a candidate for swapping, so reclaim swap space. */
977 if (PageSwapCache(page
) && vm_swap_full())
978 try_to_free_swap(page
);
979 VM_BUG_ON(PageActive(page
));
985 reset_reclaim_mode(sc
);
987 list_add(&page
->lru
, &ret_pages
);
988 VM_BUG_ON(PageLRU(page
) || PageUnevictable(page
));
992 * Tag a zone as congested if all the dirty pages encountered were
993 * backed by a congested BDI. In this case, reclaimers should just
994 * back off and wait for congestion to clear because further reclaim
995 * will encounter the same problem
997 if (nr_dirty
&& nr_dirty
== nr_congested
&& scanning_global_lru(sc
))
998 zone_set_flag(zone
, ZONE_CONGESTED
);
1000 free_hot_cold_page_list(&free_pages
, 1);
1002 list_splice(&ret_pages
, page_list
);
1003 count_vm_events(PGACTIVATE
, pgactivate
);
1004 *ret_nr_dirty
+= nr_dirty
;
1005 *ret_nr_writeback
+= nr_writeback
;
1006 return nr_reclaimed
;
1010 * Attempt to remove the specified page from its LRU. Only take this page
1011 * if it is of the appropriate PageActive status. Pages which are being
1012 * freed elsewhere are also ignored.
1014 * page: page to consider
1015 * mode: one of the LRU isolation modes defined above
1017 * returns 0 on success, -ve errno on failure.
1019 int __isolate_lru_page(struct page
*page
, isolate_mode_t mode
, int file
)
1024 /* Only take pages on the LRU. */
1028 all_lru_mode
= (mode
& (ISOLATE_ACTIVE
|ISOLATE_INACTIVE
)) ==
1029 (ISOLATE_ACTIVE
|ISOLATE_INACTIVE
);
1032 * When checking the active state, we need to be sure we are
1033 * dealing with comparible boolean values. Take the logical not
1036 if (!all_lru_mode
&& !PageActive(page
) != !(mode
& ISOLATE_ACTIVE
))
1039 if (!all_lru_mode
&& !!page_is_file_cache(page
) != file
)
1043 * When this function is being called for lumpy reclaim, we
1044 * initially look into all LRU pages, active, inactive and
1045 * unevictable; only give shrink_page_list evictable pages.
1047 if (PageUnevictable(page
))
1052 if ((mode
& ISOLATE_CLEAN
) && (PageDirty(page
) || PageWriteback(page
)))
1055 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1058 if (likely(get_page_unless_zero(page
))) {
1060 * Be careful not to clear PageLRU until after we're
1061 * sure the page is not being freed elsewhere -- the
1062 * page release code relies on it.
1072 * zone->lru_lock is heavily contended. Some of the functions that
1073 * shrink the lists perform better by taking out a batch of pages
1074 * and working on them outside the LRU lock.
1076 * For pagecache intensive workloads, this function is the hottest
1077 * spot in the kernel (apart from copy_*_user functions).
1079 * Appropriate locks must be held before calling this function.
1081 * @nr_to_scan: The number of pages to look through on the list.
1082 * @src: The LRU list to pull pages off.
1083 * @dst: The temp list to put pages on to.
1084 * @scanned: The number of pages that were scanned.
1085 * @order: The caller's attempted allocation order
1086 * @mode: One of the LRU isolation modes
1087 * @file: True [1] if isolating file [!anon] pages
1089 * returns how many pages were moved onto *@dst.
1091 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1092 struct list_head
*src
, struct list_head
*dst
,
1093 unsigned long *scanned
, int order
, isolate_mode_t mode
,
1096 unsigned long nr_taken
= 0;
1097 unsigned long nr_lumpy_taken
= 0;
1098 unsigned long nr_lumpy_dirty
= 0;
1099 unsigned long nr_lumpy_failed
= 0;
1102 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
1105 unsigned long end_pfn
;
1106 unsigned long page_pfn
;
1109 page
= lru_to_page(src
);
1110 prefetchw_prev_lru_page(page
, src
, flags
);
1112 VM_BUG_ON(!PageLRU(page
));
1114 switch (__isolate_lru_page(page
, mode
, file
)) {
1116 list_move(&page
->lru
, dst
);
1117 mem_cgroup_del_lru(page
);
1118 nr_taken
+= hpage_nr_pages(page
);
1122 /* else it is being freed elsewhere */
1123 list_move(&page
->lru
, src
);
1124 mem_cgroup_rotate_lru_list(page
, page_lru(page
));
1135 * Attempt to take all pages in the order aligned region
1136 * surrounding the tag page. Only take those pages of
1137 * the same active state as that tag page. We may safely
1138 * round the target page pfn down to the requested order
1139 * as the mem_map is guaranteed valid out to MAX_ORDER,
1140 * where that page is in a different zone we will detect
1141 * it from its zone id and abort this block scan.
1143 zone_id
= page_zone_id(page
);
1144 page_pfn
= page_to_pfn(page
);
1145 pfn
= page_pfn
& ~((1 << order
) - 1);
1146 end_pfn
= pfn
+ (1 << order
);
1147 for (; pfn
< end_pfn
; pfn
++) {
1148 struct page
*cursor_page
;
1150 /* The target page is in the block, ignore it. */
1151 if (unlikely(pfn
== page_pfn
))
1154 /* Avoid holes within the zone. */
1155 if (unlikely(!pfn_valid_within(pfn
)))
1158 cursor_page
= pfn_to_page(pfn
);
1160 /* Check that we have not crossed a zone boundary. */
1161 if (unlikely(page_zone_id(cursor_page
) != zone_id
))
1165 * If we don't have enough swap space, reclaiming of
1166 * anon page which don't already have a swap slot is
1169 if (nr_swap_pages
<= 0 && PageSwapBacked(cursor_page
) &&
1170 !PageSwapCache(cursor_page
))
1173 if (__isolate_lru_page(cursor_page
, mode
, file
) == 0) {
1174 list_move(&cursor_page
->lru
, dst
);
1175 mem_cgroup_del_lru(cursor_page
);
1176 nr_taken
+= hpage_nr_pages(cursor_page
);
1178 if (PageDirty(cursor_page
))
1183 * Check if the page is freed already.
1185 * We can't use page_count() as that
1186 * requires compound_head and we don't
1187 * have a pin on the page here. If a
1188 * page is tail, we may or may not
1189 * have isolated the head, so assume
1190 * it's not free, it'd be tricky to
1191 * track the head status without a
1194 if (!PageTail(cursor_page
) &&
1195 !atomic_read(&cursor_page
->_count
))
1201 /* If we break out of the loop above, lumpy reclaim failed */
1208 trace_mm_vmscan_lru_isolate(order
,
1211 nr_lumpy_taken
, nr_lumpy_dirty
, nr_lumpy_failed
,
1216 static unsigned long isolate_pages_global(unsigned long nr
,
1217 struct list_head
*dst
,
1218 unsigned long *scanned
, int order
,
1219 isolate_mode_t mode
,
1220 struct zone
*z
, int active
, int file
)
1227 return isolate_lru_pages(nr
, &z
->lru
[lru
].list
, dst
, scanned
, order
,
1232 * clear_active_flags() is a helper for shrink_active_list(), clearing
1233 * any active bits from the pages in the list.
1235 static unsigned long clear_active_flags(struct list_head
*page_list
,
1236 unsigned int *count
)
1242 list_for_each_entry(page
, page_list
, lru
) {
1243 int numpages
= hpage_nr_pages(page
);
1244 lru
= page_lru_base_type(page
);
1245 if (PageActive(page
)) {
1247 ClearPageActive(page
);
1248 nr_active
+= numpages
;
1251 count
[lru
] += numpages
;
1258 * isolate_lru_page - tries to isolate a page from its LRU list
1259 * @page: page to isolate from its LRU list
1261 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1262 * vmstat statistic corresponding to whatever LRU list the page was on.
1264 * Returns 0 if the page was removed from an LRU list.
1265 * Returns -EBUSY if the page was not on an LRU list.
1267 * The returned page will have PageLRU() cleared. If it was found on
1268 * the active list, it will have PageActive set. If it was found on
1269 * the unevictable list, it will have the PageUnevictable bit set. That flag
1270 * may need to be cleared by the caller before letting the page go.
1272 * The vmstat statistic corresponding to the list on which the page was
1273 * found will be decremented.
1276 * (1) Must be called with an elevated refcount on the page. This is a
1277 * fundamentnal difference from isolate_lru_pages (which is called
1278 * without a stable reference).
1279 * (2) the lru_lock must not be held.
1280 * (3) interrupts must be enabled.
1282 int isolate_lru_page(struct page
*page
)
1286 VM_BUG_ON(!page_count(page
));
1288 if (PageLRU(page
)) {
1289 struct zone
*zone
= page_zone(page
);
1291 spin_lock_irq(&zone
->lru_lock
);
1292 if (PageLRU(page
)) {
1293 int lru
= page_lru(page
);
1298 del_page_from_lru_list(zone
, page
, lru
);
1300 spin_unlock_irq(&zone
->lru_lock
);
1306 * Are there way too many processes in the direct reclaim path already?
1308 static int too_many_isolated(struct zone
*zone
, int file
,
1309 struct scan_control
*sc
)
1311 unsigned long inactive
, isolated
;
1313 if (current_is_kswapd())
1316 if (!scanning_global_lru(sc
))
1320 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1321 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1323 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1324 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1327 return isolated
> inactive
;
1331 * TODO: Try merging with migrations version of putback_lru_pages
1333 static noinline_for_stack
void
1334 putback_lru_pages(struct zone
*zone
, struct scan_control
*sc
,
1335 unsigned long nr_anon
, unsigned long nr_file
,
1336 struct list_head
*page_list
)
1339 struct pagevec pvec
;
1340 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1342 pagevec_init(&pvec
, 1);
1345 * Put back any unfreeable pages.
1347 spin_lock(&zone
->lru_lock
);
1348 while (!list_empty(page_list
)) {
1350 page
= lru_to_page(page_list
);
1351 VM_BUG_ON(PageLRU(page
));
1352 list_del(&page
->lru
);
1353 if (unlikely(!page_evictable(page
, NULL
))) {
1354 spin_unlock_irq(&zone
->lru_lock
);
1355 putback_lru_page(page
);
1356 spin_lock_irq(&zone
->lru_lock
);
1360 lru
= page_lru(page
);
1361 add_page_to_lru_list(zone
, page
, lru
);
1362 if (is_active_lru(lru
)) {
1363 int file
= is_file_lru(lru
);
1364 int numpages
= hpage_nr_pages(page
);
1365 reclaim_stat
->recent_rotated
[file
] += numpages
;
1367 if (!pagevec_add(&pvec
, page
)) {
1368 spin_unlock_irq(&zone
->lru_lock
);
1369 __pagevec_release(&pvec
);
1370 spin_lock_irq(&zone
->lru_lock
);
1373 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, -nr_anon
);
1374 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -nr_file
);
1376 spin_unlock_irq(&zone
->lru_lock
);
1377 pagevec_release(&pvec
);
1380 static noinline_for_stack
void update_isolated_counts(struct zone
*zone
,
1381 struct scan_control
*sc
,
1382 unsigned long *nr_anon
,
1383 unsigned long *nr_file
,
1384 struct list_head
*isolated_list
)
1386 unsigned long nr_active
;
1387 unsigned int count
[NR_LRU_LISTS
] = { 0, };
1388 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1390 nr_active
= clear_active_flags(isolated_list
, count
);
1391 __count_vm_events(PGDEACTIVATE
, nr_active
);
1393 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
1394 -count
[LRU_ACTIVE_FILE
]);
1395 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
1396 -count
[LRU_INACTIVE_FILE
]);
1397 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
1398 -count
[LRU_ACTIVE_ANON
]);
1399 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
1400 -count
[LRU_INACTIVE_ANON
]);
1402 *nr_anon
= count
[LRU_ACTIVE_ANON
] + count
[LRU_INACTIVE_ANON
];
1403 *nr_file
= count
[LRU_ACTIVE_FILE
] + count
[LRU_INACTIVE_FILE
];
1404 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, *nr_anon
);
1405 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, *nr_file
);
1407 reclaim_stat
->recent_scanned
[0] += *nr_anon
;
1408 reclaim_stat
->recent_scanned
[1] += *nr_file
;
1412 * Returns true if a direct reclaim should wait on pages under writeback.
1414 * If we are direct reclaiming for contiguous pages and we do not reclaim
1415 * everything in the list, try again and wait for writeback IO to complete.
1416 * This will stall high-order allocations noticeably. Only do that when really
1417 * need to free the pages under high memory pressure.
1419 static inline bool should_reclaim_stall(unsigned long nr_taken
,
1420 unsigned long nr_freed
,
1422 struct scan_control
*sc
)
1424 int lumpy_stall_priority
;
1426 /* kswapd should not stall on sync IO */
1427 if (current_is_kswapd())
1430 /* Only stall on lumpy reclaim */
1431 if (sc
->reclaim_mode
& RECLAIM_MODE_SINGLE
)
1434 /* If we have reclaimed everything on the isolated list, no stall */
1435 if (nr_freed
== nr_taken
)
1439 * For high-order allocations, there are two stall thresholds.
1440 * High-cost allocations stall immediately where as lower
1441 * order allocations such as stacks require the scanning
1442 * priority to be much higher before stalling.
1444 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
1445 lumpy_stall_priority
= DEF_PRIORITY
;
1447 lumpy_stall_priority
= DEF_PRIORITY
/ 3;
1449 return priority
<= lumpy_stall_priority
;
1453 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1454 * of reclaimed pages
1456 static noinline_for_stack
unsigned long
1457 shrink_inactive_list(unsigned long nr_to_scan
, struct zone
*zone
,
1458 struct scan_control
*sc
, int priority
, int file
)
1460 LIST_HEAD(page_list
);
1461 unsigned long nr_scanned
;
1462 unsigned long nr_reclaimed
= 0;
1463 unsigned long nr_taken
;
1464 unsigned long nr_anon
;
1465 unsigned long nr_file
;
1466 unsigned long nr_dirty
= 0;
1467 unsigned long nr_writeback
= 0;
1468 isolate_mode_t reclaim_mode
= ISOLATE_INACTIVE
;
1470 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1471 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1473 /* We are about to die and free our memory. Return now. */
1474 if (fatal_signal_pending(current
))
1475 return SWAP_CLUSTER_MAX
;
1478 set_reclaim_mode(priority
, sc
, false);
1479 if (sc
->reclaim_mode
& RECLAIM_MODE_LUMPYRECLAIM
)
1480 reclaim_mode
|= ISOLATE_ACTIVE
;
1485 reclaim_mode
|= ISOLATE_UNMAPPED
;
1486 if (!sc
->may_writepage
)
1487 reclaim_mode
|= ISOLATE_CLEAN
;
1489 spin_lock_irq(&zone
->lru_lock
);
1491 if (scanning_global_lru(sc
)) {
1492 nr_taken
= isolate_pages_global(nr_to_scan
, &page_list
,
1493 &nr_scanned
, sc
->order
, reclaim_mode
, zone
, 0, file
);
1494 zone
->pages_scanned
+= nr_scanned
;
1495 if (current_is_kswapd())
1496 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
,
1499 __count_zone_vm_events(PGSCAN_DIRECT
, zone
,
1502 nr_taken
= mem_cgroup_isolate_pages(nr_to_scan
, &page_list
,
1503 &nr_scanned
, sc
->order
, reclaim_mode
, zone
,
1504 sc
->mem_cgroup
, 0, file
);
1506 * mem_cgroup_isolate_pages() keeps track of
1507 * scanned pages on its own.
1511 if (nr_taken
== 0) {
1512 spin_unlock_irq(&zone
->lru_lock
);
1516 update_isolated_counts(zone
, sc
, &nr_anon
, &nr_file
, &page_list
);
1518 spin_unlock_irq(&zone
->lru_lock
);
1520 nr_reclaimed
= shrink_page_list(&page_list
, zone
, sc
, priority
,
1521 &nr_dirty
, &nr_writeback
);
1523 /* Check if we should syncronously wait for writeback */
1524 if (should_reclaim_stall(nr_taken
, nr_reclaimed
, priority
, sc
)) {
1525 set_reclaim_mode(priority
, sc
, true);
1526 nr_reclaimed
+= shrink_page_list(&page_list
, zone
, sc
,
1527 priority
, &nr_dirty
, &nr_writeback
);
1530 local_irq_disable();
1531 if (current_is_kswapd())
1532 __count_vm_events(KSWAPD_STEAL
, nr_reclaimed
);
1533 __count_zone_vm_events(PGSTEAL
, zone
, nr_reclaimed
);
1535 putback_lru_pages(zone
, sc
, nr_anon
, nr_file
, &page_list
);
1538 * If reclaim is isolating dirty pages under writeback, it implies
1539 * that the long-lived page allocation rate is exceeding the page
1540 * laundering rate. Either the global limits are not being effective
1541 * at throttling processes due to the page distribution throughout
1542 * zones or there is heavy usage of a slow backing device. The
1543 * only option is to throttle from reclaim context which is not ideal
1544 * as there is no guarantee the dirtying process is throttled in the
1545 * same way balance_dirty_pages() manages.
1547 * This scales the number of dirty pages that must be under writeback
1548 * before throttling depending on priority. It is a simple backoff
1549 * function that has the most effect in the range DEF_PRIORITY to
1550 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1551 * in trouble and reclaim is considered to be in trouble.
1553 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1554 * DEF_PRIORITY-1 50% must be PageWriteback
1555 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1557 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1558 * isolated page is PageWriteback
1560 if (nr_writeback
&& nr_writeback
>= (nr_taken
>> (DEF_PRIORITY
-priority
)))
1561 wait_iff_congested(zone
, BLK_RW_ASYNC
, HZ
/10);
1563 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1565 nr_scanned
, nr_reclaimed
,
1567 trace_shrink_flags(file
, sc
->reclaim_mode
));
1568 return nr_reclaimed
;
1572 * This moves pages from the active list to the inactive list.
1574 * We move them the other way if the page is referenced by one or more
1575 * processes, from rmap.
1577 * If the pages are mostly unmapped, the processing is fast and it is
1578 * appropriate to hold zone->lru_lock across the whole operation. But if
1579 * the pages are mapped, the processing is slow (page_referenced()) so we
1580 * should drop zone->lru_lock around each page. It's impossible to balance
1581 * this, so instead we remove the pages from the LRU while processing them.
1582 * It is safe to rely on PG_active against the non-LRU pages in here because
1583 * nobody will play with that bit on a non-LRU page.
1585 * The downside is that we have to touch page->_count against each page.
1586 * But we had to alter page->flags anyway.
1589 static void move_active_pages_to_lru(struct zone
*zone
,
1590 struct list_head
*list
,
1593 unsigned long pgmoved
= 0;
1594 struct pagevec pvec
;
1597 pagevec_init(&pvec
, 1);
1599 while (!list_empty(list
)) {
1600 page
= lru_to_page(list
);
1602 VM_BUG_ON(PageLRU(page
));
1605 list_move(&page
->lru
, &zone
->lru
[lru
].list
);
1606 mem_cgroup_add_lru_list(page
, lru
);
1607 pgmoved
+= hpage_nr_pages(page
);
1609 if (!pagevec_add(&pvec
, page
) || list_empty(list
)) {
1610 spin_unlock_irq(&zone
->lru_lock
);
1611 if (buffer_heads_over_limit
)
1612 pagevec_strip(&pvec
);
1613 __pagevec_release(&pvec
);
1614 spin_lock_irq(&zone
->lru_lock
);
1617 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1618 if (!is_active_lru(lru
))
1619 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1622 static void shrink_active_list(unsigned long nr_pages
, struct zone
*zone
,
1623 struct scan_control
*sc
, int priority
, int file
)
1625 unsigned long nr_taken
;
1626 unsigned long pgscanned
;
1627 unsigned long vm_flags
;
1628 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1629 LIST_HEAD(l_active
);
1630 LIST_HEAD(l_inactive
);
1632 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1633 unsigned long nr_rotated
= 0;
1634 isolate_mode_t reclaim_mode
= ISOLATE_ACTIVE
;
1639 reclaim_mode
|= ISOLATE_UNMAPPED
;
1640 if (!sc
->may_writepage
)
1641 reclaim_mode
|= ISOLATE_CLEAN
;
1643 spin_lock_irq(&zone
->lru_lock
);
1644 if (scanning_global_lru(sc
)) {
1645 nr_taken
= isolate_pages_global(nr_pages
, &l_hold
,
1646 &pgscanned
, sc
->order
,
1649 zone
->pages_scanned
+= pgscanned
;
1651 nr_taken
= mem_cgroup_isolate_pages(nr_pages
, &l_hold
,
1652 &pgscanned
, sc
->order
,
1654 sc
->mem_cgroup
, 1, file
);
1656 * mem_cgroup_isolate_pages() keeps track of
1657 * scanned pages on its own.
1661 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1663 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1665 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -nr_taken
);
1667 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -nr_taken
);
1668 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1669 spin_unlock_irq(&zone
->lru_lock
);
1671 while (!list_empty(&l_hold
)) {
1673 page
= lru_to_page(&l_hold
);
1674 list_del(&page
->lru
);
1676 if (unlikely(!page_evictable(page
, NULL
))) {
1677 putback_lru_page(page
);
1681 if (page_referenced(page
, 0, sc
->mem_cgroup
, &vm_flags
)) {
1682 nr_rotated
+= hpage_nr_pages(page
);
1684 * Identify referenced, file-backed active pages and
1685 * give them one more trip around the active list. So
1686 * that executable code get better chances to stay in
1687 * memory under moderate memory pressure. Anon pages
1688 * are not likely to be evicted by use-once streaming
1689 * IO, plus JVM can create lots of anon VM_EXEC pages,
1690 * so we ignore them here.
1692 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1693 list_add(&page
->lru
, &l_active
);
1698 ClearPageActive(page
); /* we are de-activating */
1699 list_add(&page
->lru
, &l_inactive
);
1703 * Move pages back to the lru list.
1705 spin_lock_irq(&zone
->lru_lock
);
1707 * Count referenced pages from currently used mappings as rotated,
1708 * even though only some of them are actually re-activated. This
1709 * helps balance scan pressure between file and anonymous pages in
1712 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1714 move_active_pages_to_lru(zone
, &l_active
,
1715 LRU_ACTIVE
+ file
* LRU_FILE
);
1716 move_active_pages_to_lru(zone
, &l_inactive
,
1717 LRU_BASE
+ file
* LRU_FILE
);
1718 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1719 spin_unlock_irq(&zone
->lru_lock
);
1723 static int inactive_anon_is_low_global(struct zone
*zone
)
1725 unsigned long active
, inactive
;
1727 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1728 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1730 if (inactive
* zone
->inactive_ratio
< active
)
1737 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1738 * @zone: zone to check
1739 * @sc: scan control of this context
1741 * Returns true if the zone does not have enough inactive anon pages,
1742 * meaning some active anon pages need to be deactivated.
1744 static int inactive_anon_is_low(struct zone
*zone
, struct scan_control
*sc
)
1749 * If we don't have swap space, anonymous page deactivation
1752 if (!total_swap_pages
)
1755 if (scanning_global_lru(sc
))
1756 low
= inactive_anon_is_low_global(zone
);
1758 low
= mem_cgroup_inactive_anon_is_low(sc
->mem_cgroup
, zone
);
1762 static inline int inactive_anon_is_low(struct zone
*zone
,
1763 struct scan_control
*sc
)
1769 static int inactive_file_is_low_global(struct zone
*zone
)
1771 unsigned long active
, inactive
;
1773 active
= zone_page_state(zone
, NR_ACTIVE_FILE
);
1774 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1776 return (active
> inactive
);
1780 * inactive_file_is_low - check if file pages need to be deactivated
1781 * @zone: zone to check
1782 * @sc: scan control of this context
1784 * When the system is doing streaming IO, memory pressure here
1785 * ensures that active file pages get deactivated, until more
1786 * than half of the file pages are on the inactive list.
1788 * Once we get to that situation, protect the system's working
1789 * set from being evicted by disabling active file page aging.
1791 * This uses a different ratio than the anonymous pages, because
1792 * the page cache uses a use-once replacement algorithm.
1794 static int inactive_file_is_low(struct zone
*zone
, struct scan_control
*sc
)
1798 if (scanning_global_lru(sc
))
1799 low
= inactive_file_is_low_global(zone
);
1801 low
= mem_cgroup_inactive_file_is_low(sc
->mem_cgroup
, zone
);
1805 static int inactive_list_is_low(struct zone
*zone
, struct scan_control
*sc
,
1809 return inactive_file_is_low(zone
, sc
);
1811 return inactive_anon_is_low(zone
, sc
);
1814 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1815 struct zone
*zone
, struct scan_control
*sc
, int priority
)
1817 int file
= is_file_lru(lru
);
1819 if (is_active_lru(lru
)) {
1820 if (inactive_list_is_low(zone
, sc
, file
))
1821 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1825 return shrink_inactive_list(nr_to_scan
, zone
, sc
, priority
, file
);
1828 static int vmscan_swappiness(struct scan_control
*sc
)
1830 if (scanning_global_lru(sc
))
1831 return vm_swappiness
;
1832 return mem_cgroup_swappiness(sc
->mem_cgroup
);
1836 * Determine how aggressively the anon and file LRU lists should be
1837 * scanned. The relative value of each set of LRU lists is determined
1838 * by looking at the fraction of the pages scanned we did rotate back
1839 * onto the active list instead of evict.
1841 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1843 static void get_scan_count(struct zone
*zone
, struct scan_control
*sc
,
1844 unsigned long *nr
, int priority
)
1846 unsigned long anon
, file
, free
;
1847 unsigned long anon_prio
, file_prio
;
1848 unsigned long ap
, fp
;
1849 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1850 u64 fraction
[2], denominator
;
1853 bool force_scan
= false;
1856 * If the zone or memcg is small, nr[l] can be 0. This
1857 * results in no scanning on this priority and a potential
1858 * priority drop. Global direct reclaim can go to the next
1859 * zone and tends to have no problems. Global kswapd is for
1860 * zone balancing and it needs to scan a minimum amount. When
1861 * reclaiming for a memcg, a priority drop can cause high
1862 * latencies, so it's better to scan a minimum amount there as
1865 if (scanning_global_lru(sc
) && current_is_kswapd())
1867 if (!scanning_global_lru(sc
))
1870 /* If we have no swap space, do not bother scanning anon pages. */
1871 if (!sc
->may_swap
|| (nr_swap_pages
<= 0)) {
1879 anon
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_ANON
) +
1880 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
);
1881 file
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_FILE
) +
1882 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
1884 if (scanning_global_lru(sc
)) {
1885 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1886 /* If we have very few page cache pages,
1887 force-scan anon pages. */
1888 if (unlikely(file
+ free
<= high_wmark_pages(zone
))) {
1897 * With swappiness at 100, anonymous and file have the same priority.
1898 * This scanning priority is essentially the inverse of IO cost.
1900 anon_prio
= vmscan_swappiness(sc
);
1901 file_prio
= 200 - vmscan_swappiness(sc
);
1904 * OK, so we have swap space and a fair amount of page cache
1905 * pages. We use the recently rotated / recently scanned
1906 * ratios to determine how valuable each cache is.
1908 * Because workloads change over time (and to avoid overflow)
1909 * we keep these statistics as a floating average, which ends
1910 * up weighing recent references more than old ones.
1912 * anon in [0], file in [1]
1914 spin_lock_irq(&zone
->lru_lock
);
1915 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1916 reclaim_stat
->recent_scanned
[0] /= 2;
1917 reclaim_stat
->recent_rotated
[0] /= 2;
1920 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1921 reclaim_stat
->recent_scanned
[1] /= 2;
1922 reclaim_stat
->recent_rotated
[1] /= 2;
1926 * The amount of pressure on anon vs file pages is inversely
1927 * proportional to the fraction of recently scanned pages on
1928 * each list that were recently referenced and in active use.
1930 ap
= (anon_prio
+ 1) * (reclaim_stat
->recent_scanned
[0] + 1);
1931 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1933 fp
= (file_prio
+ 1) * (reclaim_stat
->recent_scanned
[1] + 1);
1934 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1935 spin_unlock_irq(&zone
->lru_lock
);
1939 denominator
= ap
+ fp
+ 1;
1941 for_each_evictable_lru(l
) {
1942 int file
= is_file_lru(l
);
1945 scan
= zone_nr_lru_pages(zone
, sc
, l
);
1946 if (priority
|| noswap
) {
1948 if (!scan
&& force_scan
)
1949 scan
= SWAP_CLUSTER_MAX
;
1950 scan
= div64_u64(scan
* fraction
[file
], denominator
);
1957 * Reclaim/compaction depends on a number of pages being freed. To avoid
1958 * disruption to the system, a small number of order-0 pages continue to be
1959 * rotated and reclaimed in the normal fashion. However, by the time we get
1960 * back to the allocator and call try_to_compact_zone(), we ensure that
1961 * there are enough free pages for it to be likely successful
1963 static inline bool should_continue_reclaim(struct zone
*zone
,
1964 unsigned long nr_reclaimed
,
1965 unsigned long nr_scanned
,
1966 struct scan_control
*sc
)
1968 unsigned long pages_for_compaction
;
1969 unsigned long inactive_lru_pages
;
1971 /* If not in reclaim/compaction mode, stop */
1972 if (!(sc
->reclaim_mode
& RECLAIM_MODE_COMPACTION
))
1975 /* Consider stopping depending on scan and reclaim activity */
1976 if (sc
->gfp_mask
& __GFP_REPEAT
) {
1978 * For __GFP_REPEAT allocations, stop reclaiming if the
1979 * full LRU list has been scanned and we are still failing
1980 * to reclaim pages. This full LRU scan is potentially
1981 * expensive but a __GFP_REPEAT caller really wants to succeed
1983 if (!nr_reclaimed
&& !nr_scanned
)
1987 * For non-__GFP_REPEAT allocations which can presumably
1988 * fail without consequence, stop if we failed to reclaim
1989 * any pages from the last SWAP_CLUSTER_MAX number of
1990 * pages that were scanned. This will return to the
1991 * caller faster at the risk reclaim/compaction and
1992 * the resulting allocation attempt fails
1999 * If we have not reclaimed enough pages for compaction and the
2000 * inactive lists are large enough, continue reclaiming
2002 pages_for_compaction
= (2UL << sc
->order
);
2003 inactive_lru_pages
= zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
2004 if (nr_swap_pages
> 0)
2005 inactive_lru_pages
+= zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
);
2006 if (sc
->nr_reclaimed
< pages_for_compaction
&&
2007 inactive_lru_pages
> pages_for_compaction
)
2010 /* If compaction would go ahead or the allocation would succeed, stop */
2011 switch (compaction_suitable(zone
, sc
->order
)) {
2012 case COMPACT_PARTIAL
:
2013 case COMPACT_CONTINUE
:
2021 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2023 static void shrink_zone(int priority
, struct zone
*zone
,
2024 struct scan_control
*sc
)
2026 unsigned long nr
[NR_LRU_LISTS
];
2027 unsigned long nr_to_scan
;
2029 unsigned long nr_reclaimed
, nr_scanned
;
2030 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2031 struct blk_plug plug
;
2035 nr_scanned
= sc
->nr_scanned
;
2036 get_scan_count(zone
, sc
, nr
, priority
);
2038 blk_start_plug(&plug
);
2039 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2040 nr
[LRU_INACTIVE_FILE
]) {
2041 for_each_evictable_lru(l
) {
2043 nr_to_scan
= min_t(unsigned long,
2044 nr
[l
], SWAP_CLUSTER_MAX
);
2045 nr
[l
] -= nr_to_scan
;
2047 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
2048 zone
, sc
, priority
);
2052 * On large memory systems, scan >> priority can become
2053 * really large. This is fine for the starting priority;
2054 * we want to put equal scanning pressure on each zone.
2055 * However, if the VM has a harder time of freeing pages,
2056 * with multiple processes reclaiming pages, the total
2057 * freeing target can get unreasonably large.
2059 if (nr_reclaimed
>= nr_to_reclaim
&& priority
< DEF_PRIORITY
)
2062 blk_finish_plug(&plug
);
2063 sc
->nr_reclaimed
+= nr_reclaimed
;
2066 * Even if we did not try to evict anon pages at all, we want to
2067 * rebalance the anon lru active/inactive ratio.
2069 if (inactive_anon_is_low(zone
, sc
))
2070 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
2072 /* reclaim/compaction might need reclaim to continue */
2073 if (should_continue_reclaim(zone
, nr_reclaimed
,
2074 sc
->nr_scanned
- nr_scanned
, sc
))
2077 throttle_vm_writeout(sc
->gfp_mask
);
2081 * This is the direct reclaim path, for page-allocating processes. We only
2082 * try to reclaim pages from zones which will satisfy the caller's allocation
2085 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2087 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2089 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2090 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2091 * zone defense algorithm.
2093 * If a zone is deemed to be full of pinned pages then just give it a light
2094 * scan then give up on it.
2096 * This function returns true if a zone is being reclaimed for a costly
2097 * high-order allocation and compaction is either ready to begin or deferred.
2098 * This indicates to the caller that it should retry the allocation or fail.
2100 static bool shrink_zones(int priority
, struct zonelist
*zonelist
,
2101 struct scan_control
*sc
)
2105 unsigned long nr_soft_reclaimed
;
2106 unsigned long nr_soft_scanned
;
2107 bool should_abort_reclaim
= false;
2109 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2110 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2111 if (!populated_zone(zone
))
2114 * Take care memory controller reclaiming has small influence
2117 if (scanning_global_lru(sc
)) {
2118 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2120 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2121 continue; /* Let kswapd poll it */
2122 if (COMPACTION_BUILD
) {
2124 * If we already have plenty of memory free for
2125 * compaction in this zone, don't free any more.
2126 * Even though compaction is invoked for any
2127 * non-zero order, only frequent costly order
2128 * reclamation is disruptive enough to become a
2129 * noticable problem, like transparent huge page
2132 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
2133 (compaction_suitable(zone
, sc
->order
) ||
2134 compaction_deferred(zone
))) {
2135 should_abort_reclaim
= true;
2140 * This steals pages from memory cgroups over softlimit
2141 * and returns the number of reclaimed pages and
2142 * scanned pages. This works for global memory pressure
2143 * and balancing, not for a memcg's limit.
2145 nr_soft_scanned
= 0;
2146 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2147 sc
->order
, sc
->gfp_mask
,
2149 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2150 sc
->nr_scanned
+= nr_soft_scanned
;
2151 /* need some check for avoid more shrink_zone() */
2154 shrink_zone(priority
, zone
, sc
);
2157 return should_abort_reclaim
;
2160 static bool zone_reclaimable(struct zone
*zone
)
2162 return zone
->pages_scanned
< zone_reclaimable_pages(zone
) * 6;
2165 /* All zones in zonelist are unreclaimable? */
2166 static bool all_unreclaimable(struct zonelist
*zonelist
,
2167 struct scan_control
*sc
)
2172 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2173 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2174 if (!populated_zone(zone
))
2176 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2178 if (!zone
->all_unreclaimable
)
2186 * This is the main entry point to direct page reclaim.
2188 * If a full scan of the inactive list fails to free enough memory then we
2189 * are "out of memory" and something needs to be killed.
2191 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2192 * high - the zone may be full of dirty or under-writeback pages, which this
2193 * caller can't do much about. We kick the writeback threads and take explicit
2194 * naps in the hope that some of these pages can be written. But if the
2195 * allocating task holds filesystem locks which prevent writeout this might not
2196 * work, and the allocation attempt will fail.
2198 * returns: 0, if no pages reclaimed
2199 * else, the number of pages reclaimed
2201 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2202 struct scan_control
*sc
,
2203 struct shrink_control
*shrink
)
2206 unsigned long total_scanned
= 0;
2207 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2210 unsigned long writeback_threshold
;
2213 delayacct_freepages_start();
2215 if (scanning_global_lru(sc
))
2216 count_vm_event(ALLOCSTALL
);
2218 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2221 disable_swap_token(sc
->mem_cgroup
);
2222 if (shrink_zones(priority
, zonelist
, sc
))
2226 * Don't shrink slabs when reclaiming memory from
2227 * over limit cgroups
2229 if (scanning_global_lru(sc
)) {
2230 unsigned long lru_pages
= 0;
2231 for_each_zone_zonelist(zone
, z
, zonelist
,
2232 gfp_zone(sc
->gfp_mask
)) {
2233 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2236 lru_pages
+= zone_reclaimable_pages(zone
);
2239 shrink_slab(shrink
, sc
->nr_scanned
, lru_pages
);
2240 if (reclaim_state
) {
2241 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2242 reclaim_state
->reclaimed_slab
= 0;
2245 total_scanned
+= sc
->nr_scanned
;
2246 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2250 * Try to write back as many pages as we just scanned. This
2251 * tends to cause slow streaming writers to write data to the
2252 * disk smoothly, at the dirtying rate, which is nice. But
2253 * that's undesirable in laptop mode, where we *want* lumpy
2254 * writeout. So in laptop mode, write out the whole world.
2256 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2257 if (total_scanned
> writeback_threshold
) {
2258 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
,
2259 WB_REASON_TRY_TO_FREE_PAGES
);
2260 sc
->may_writepage
= 1;
2263 /* Take a nap, wait for some writeback to complete */
2264 if (!sc
->hibernation_mode
&& sc
->nr_scanned
&&
2265 priority
< DEF_PRIORITY
- 2) {
2266 struct zone
*preferred_zone
;
2268 first_zones_zonelist(zonelist
, gfp_zone(sc
->gfp_mask
),
2269 &cpuset_current_mems_allowed
,
2271 wait_iff_congested(preferred_zone
, BLK_RW_ASYNC
, HZ
/10);
2276 delayacct_freepages_end();
2279 if (sc
->nr_reclaimed
)
2280 return sc
->nr_reclaimed
;
2283 * As hibernation is going on, kswapd is freezed so that it can't mark
2284 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2287 if (oom_killer_disabled
)
2290 /* top priority shrink_zones still had more to do? don't OOM, then */
2291 if (scanning_global_lru(sc
) && !all_unreclaimable(zonelist
, sc
))
2297 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2298 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2300 unsigned long nr_reclaimed
;
2301 struct scan_control sc
= {
2302 .gfp_mask
= gfp_mask
,
2303 .may_writepage
= !laptop_mode
,
2304 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2309 .nodemask
= nodemask
,
2311 struct shrink_control shrink
= {
2312 .gfp_mask
= sc
.gfp_mask
,
2315 trace_mm_vmscan_direct_reclaim_begin(order
,
2319 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2321 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2323 return nr_reclaimed
;
2326 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2328 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*mem
,
2329 gfp_t gfp_mask
, bool noswap
,
2331 unsigned long *nr_scanned
)
2333 struct scan_control sc
= {
2335 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2336 .may_writepage
= !laptop_mode
,
2338 .may_swap
= !noswap
,
2343 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2344 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2346 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2351 * NOTE: Although we can get the priority field, using it
2352 * here is not a good idea, since it limits the pages we can scan.
2353 * if we don't reclaim here, the shrink_zone from balance_pgdat
2354 * will pick up pages from other mem cgroup's as well. We hack
2355 * the priority and make it zero.
2357 shrink_zone(0, zone
, &sc
);
2359 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2361 *nr_scanned
= sc
.nr_scanned
;
2362 return sc
.nr_reclaimed
;
2365 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*mem_cont
,
2369 struct zonelist
*zonelist
;
2370 unsigned long nr_reclaimed
;
2372 struct scan_control sc
= {
2373 .may_writepage
= !laptop_mode
,
2375 .may_swap
= !noswap
,
2376 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2378 .mem_cgroup
= mem_cont
,
2379 .nodemask
= NULL
, /* we don't care the placement */
2380 .gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2381 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
2383 struct shrink_control shrink
= {
2384 .gfp_mask
= sc
.gfp_mask
,
2388 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2389 * take care of from where we get pages. So the node where we start the
2390 * scan does not need to be the current node.
2392 nid
= mem_cgroup_select_victim_node(mem_cont
);
2394 zonelist
= NODE_DATA(nid
)->node_zonelists
;
2396 trace_mm_vmscan_memcg_reclaim_begin(0,
2400 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2402 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2404 return nr_reclaimed
;
2409 * pgdat_balanced is used when checking if a node is balanced for high-order
2410 * allocations. Only zones that meet watermarks and are in a zone allowed
2411 * by the callers classzone_idx are added to balanced_pages. The total of
2412 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2413 * for the node to be considered balanced. Forcing all zones to be balanced
2414 * for high orders can cause excessive reclaim when there are imbalanced zones.
2415 * The choice of 25% is due to
2416 * o a 16M DMA zone that is balanced will not balance a zone on any
2417 * reasonable sized machine
2418 * o On all other machines, the top zone must be at least a reasonable
2419 * percentage of the middle zones. For example, on 32-bit x86, highmem
2420 * would need to be at least 256M for it to be balance a whole node.
2421 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2422 * to balance a node on its own. These seemed like reasonable ratios.
2424 static bool pgdat_balanced(pg_data_t
*pgdat
, unsigned long balanced_pages
,
2427 unsigned long present_pages
= 0;
2430 for (i
= 0; i
<= classzone_idx
; i
++)
2431 present_pages
+= pgdat
->node_zones
[i
].present_pages
;
2433 /* A special case here: if zone has no page, we think it's balanced */
2434 return balanced_pages
>= (present_pages
>> 2);
2437 /* is kswapd sleeping prematurely? */
2438 static bool sleeping_prematurely(pg_data_t
*pgdat
, int order
, long remaining
,
2442 unsigned long balanced
= 0;
2443 bool all_zones_ok
= true;
2445 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2449 /* Check the watermark levels */
2450 for (i
= 0; i
<= classzone_idx
; i
++) {
2451 struct zone
*zone
= pgdat
->node_zones
+ i
;
2453 if (!populated_zone(zone
))
2457 * balance_pgdat() skips over all_unreclaimable after
2458 * DEF_PRIORITY. Effectively, it considers them balanced so
2459 * they must be considered balanced here as well if kswapd
2462 if (zone
->all_unreclaimable
) {
2463 balanced
+= zone
->present_pages
;
2467 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
),
2469 all_zones_ok
= false;
2471 balanced
+= zone
->present_pages
;
2475 * For high-order requests, the balanced zones must contain at least
2476 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2480 return !pgdat_balanced(pgdat
, balanced
, classzone_idx
);
2482 return !all_zones_ok
;
2486 * For kswapd, balance_pgdat() will work across all this node's zones until
2487 * they are all at high_wmark_pages(zone).
2489 * Returns the final order kswapd was reclaiming at
2491 * There is special handling here for zones which are full of pinned pages.
2492 * This can happen if the pages are all mlocked, or if they are all used by
2493 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2494 * What we do is to detect the case where all pages in the zone have been
2495 * scanned twice and there has been zero successful reclaim. Mark the zone as
2496 * dead and from now on, only perform a short scan. Basically we're polling
2497 * the zone for when the problem goes away.
2499 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2500 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2501 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2502 * lower zones regardless of the number of free pages in the lower zones. This
2503 * interoperates with the page allocator fallback scheme to ensure that aging
2504 * of pages is balanced across the zones.
2506 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
2510 unsigned long balanced
;
2513 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
2514 unsigned long total_scanned
;
2515 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2516 unsigned long nr_soft_reclaimed
;
2517 unsigned long nr_soft_scanned
;
2518 struct scan_control sc
= {
2519 .gfp_mask
= GFP_KERNEL
,
2523 * kswapd doesn't want to be bailed out while reclaim. because
2524 * we want to put equal scanning pressure on each zone.
2526 .nr_to_reclaim
= ULONG_MAX
,
2530 struct shrink_control shrink
= {
2531 .gfp_mask
= sc
.gfp_mask
,
2535 sc
.nr_reclaimed
= 0;
2536 sc
.may_writepage
= !laptop_mode
;
2537 count_vm_event(PAGEOUTRUN
);
2539 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2540 unsigned long lru_pages
= 0;
2541 int has_under_min_watermark_zone
= 0;
2543 /* The swap token gets in the way of swapout... */
2545 disable_swap_token(NULL
);
2551 * Scan in the highmem->dma direction for the highest
2552 * zone which needs scanning
2554 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
2555 struct zone
*zone
= pgdat
->node_zones
+ i
;
2557 if (!populated_zone(zone
))
2560 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2564 * Do some background aging of the anon list, to give
2565 * pages a chance to be referenced before reclaiming.
2567 if (inactive_anon_is_low(zone
, &sc
))
2568 shrink_active_list(SWAP_CLUSTER_MAX
, zone
,
2571 if (!zone_watermark_ok_safe(zone
, order
,
2572 high_wmark_pages(zone
), 0, 0)) {
2576 /* If balanced, clear the congested flag */
2577 zone_clear_flag(zone
, ZONE_CONGESTED
);
2583 for (i
= 0; i
<= end_zone
; i
++) {
2584 struct zone
*zone
= pgdat
->node_zones
+ i
;
2586 lru_pages
+= zone_reclaimable_pages(zone
);
2590 * Now scan the zone in the dma->highmem direction, stopping
2591 * at the last zone which needs scanning.
2593 * We do this because the page allocator works in the opposite
2594 * direction. This prevents the page allocator from allocating
2595 * pages behind kswapd's direction of progress, which would
2596 * cause too much scanning of the lower zones.
2598 for (i
= 0; i
<= end_zone
; i
++) {
2599 struct zone
*zone
= pgdat
->node_zones
+ i
;
2601 unsigned long balance_gap
;
2603 if (!populated_zone(zone
))
2606 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2611 nr_soft_scanned
= 0;
2613 * Call soft limit reclaim before calling shrink_zone.
2615 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2618 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
2619 total_scanned
+= nr_soft_scanned
;
2622 * We put equal pressure on every zone, unless
2623 * one zone has way too many pages free
2624 * already. The "too many pages" is defined
2625 * as the high wmark plus a "gap" where the
2626 * gap is either the low watermark or 1%
2627 * of the zone, whichever is smaller.
2629 balance_gap
= min(low_wmark_pages(zone
),
2630 (zone
->present_pages
+
2631 KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2632 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2633 if (!zone_watermark_ok_safe(zone
, order
,
2634 high_wmark_pages(zone
) + balance_gap
,
2636 shrink_zone(priority
, zone
, &sc
);
2638 reclaim_state
->reclaimed_slab
= 0;
2639 nr_slab
= shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
);
2640 sc
.nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2641 total_scanned
+= sc
.nr_scanned
;
2643 if (nr_slab
== 0 && !zone_reclaimable(zone
))
2644 zone
->all_unreclaimable
= 1;
2648 * If we've done a decent amount of scanning and
2649 * the reclaim ratio is low, start doing writepage
2650 * even in laptop mode
2652 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
2653 total_scanned
> sc
.nr_reclaimed
+ sc
.nr_reclaimed
/ 2)
2654 sc
.may_writepage
= 1;
2656 if (zone
->all_unreclaimable
) {
2657 if (end_zone
&& end_zone
== i
)
2662 if (!zone_watermark_ok_safe(zone
, order
,
2663 high_wmark_pages(zone
), end_zone
, 0)) {
2666 * We are still under min water mark. This
2667 * means that we have a GFP_ATOMIC allocation
2668 * failure risk. Hurry up!
2670 if (!zone_watermark_ok_safe(zone
, order
,
2671 min_wmark_pages(zone
), end_zone
, 0))
2672 has_under_min_watermark_zone
= 1;
2675 * If a zone reaches its high watermark,
2676 * consider it to be no longer congested. It's
2677 * possible there are dirty pages backed by
2678 * congested BDIs but as pressure is relieved,
2679 * spectulatively avoid congestion waits
2681 zone_clear_flag(zone
, ZONE_CONGESTED
);
2682 if (i
<= *classzone_idx
)
2683 balanced
+= zone
->present_pages
;
2687 if (all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))
2688 break; /* kswapd: all done */
2690 * OK, kswapd is getting into trouble. Take a nap, then take
2691 * another pass across the zones.
2693 if (total_scanned
&& (priority
< DEF_PRIORITY
- 2)) {
2694 if (has_under_min_watermark_zone
)
2695 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT
);
2697 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
2701 * We do this so kswapd doesn't build up large priorities for
2702 * example when it is freeing in parallel with allocators. It
2703 * matches the direct reclaim path behaviour in terms of impact
2704 * on zone->*_priority.
2706 if (sc
.nr_reclaimed
>= SWAP_CLUSTER_MAX
)
2712 * order-0: All zones must meet high watermark for a balanced node
2713 * high-order: Balanced zones must make up at least 25% of the node
2714 * for the node to be balanced
2716 if (!(all_zones_ok
|| (order
&& pgdat_balanced(pgdat
, balanced
, *classzone_idx
)))) {
2722 * Fragmentation may mean that the system cannot be
2723 * rebalanced for high-order allocations in all zones.
2724 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2725 * it means the zones have been fully scanned and are still
2726 * not balanced. For high-order allocations, there is
2727 * little point trying all over again as kswapd may
2730 * Instead, recheck all watermarks at order-0 as they
2731 * are the most important. If watermarks are ok, kswapd will go
2732 * back to sleep. High-order users can still perform direct
2733 * reclaim if they wish.
2735 if (sc
.nr_reclaimed
< SWAP_CLUSTER_MAX
)
2736 order
= sc
.order
= 0;
2742 * If kswapd was reclaiming at a higher order, it has the option of
2743 * sleeping without all zones being balanced. Before it does, it must
2744 * ensure that the watermarks for order-0 on *all* zones are met and
2745 * that the congestion flags are cleared. The congestion flag must
2746 * be cleared as kswapd is the only mechanism that clears the flag
2747 * and it is potentially going to sleep here.
2750 for (i
= 0; i
<= end_zone
; i
++) {
2751 struct zone
*zone
= pgdat
->node_zones
+ i
;
2753 if (!populated_zone(zone
))
2756 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2759 /* Confirm the zone is balanced for order-0 */
2760 if (!zone_watermark_ok(zone
, 0,
2761 high_wmark_pages(zone
), 0, 0)) {
2762 order
= sc
.order
= 0;
2766 /* If balanced, clear the congested flag */
2767 zone_clear_flag(zone
, ZONE_CONGESTED
);
2768 if (i
<= *classzone_idx
)
2769 balanced
+= zone
->present_pages
;
2774 * Return the order we were reclaiming at so sleeping_prematurely()
2775 * makes a decision on the order we were last reclaiming at. However,
2776 * if another caller entered the allocator slow path while kswapd
2777 * was awake, order will remain at the higher level
2779 *classzone_idx
= end_zone
;
2783 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2788 if (freezing(current
) || kthread_should_stop())
2791 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2793 /* Try to sleep for a short interval */
2794 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2795 remaining
= schedule_timeout(HZ
/10);
2796 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2797 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2801 * After a short sleep, check if it was a premature sleep. If not, then
2802 * go fully to sleep until explicitly woken up.
2804 if (!sleeping_prematurely(pgdat
, order
, remaining
, classzone_idx
)) {
2805 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
2808 * vmstat counters are not perfectly accurate and the estimated
2809 * value for counters such as NR_FREE_PAGES can deviate from the
2810 * true value by nr_online_cpus * threshold. To avoid the zone
2811 * watermarks being breached while under pressure, we reduce the
2812 * per-cpu vmstat threshold while kswapd is awake and restore
2813 * them before going back to sleep.
2815 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
2817 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
2820 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
2822 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
2824 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2828 * The background pageout daemon, started as a kernel thread
2829 * from the init process.
2831 * This basically trickles out pages so that we have _some_
2832 * free memory available even if there is no other activity
2833 * that frees anything up. This is needed for things like routing
2834 * etc, where we otherwise might have all activity going on in
2835 * asynchronous contexts that cannot page things out.
2837 * If there are applications that are active memory-allocators
2838 * (most normal use), this basically shouldn't matter.
2840 static int kswapd(void *p
)
2842 unsigned long order
, new_order
;
2843 unsigned balanced_order
;
2844 int classzone_idx
, new_classzone_idx
;
2845 int balanced_classzone_idx
;
2846 pg_data_t
*pgdat
= (pg_data_t
*)p
;
2847 struct task_struct
*tsk
= current
;
2849 struct reclaim_state reclaim_state
= {
2850 .reclaimed_slab
= 0,
2852 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
2854 lockdep_set_current_reclaim_state(GFP_KERNEL
);
2856 if (!cpumask_empty(cpumask
))
2857 set_cpus_allowed_ptr(tsk
, cpumask
);
2858 current
->reclaim_state
= &reclaim_state
;
2861 * Tell the memory management that we're a "memory allocator",
2862 * and that if we need more memory we should get access to it
2863 * regardless (see "__alloc_pages()"). "kswapd" should
2864 * never get caught in the normal page freeing logic.
2866 * (Kswapd normally doesn't need memory anyway, but sometimes
2867 * you need a small amount of memory in order to be able to
2868 * page out something else, and this flag essentially protects
2869 * us from recursively trying to free more memory as we're
2870 * trying to free the first piece of memory in the first place).
2872 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
2875 order
= new_order
= 0;
2877 classzone_idx
= new_classzone_idx
= pgdat
->nr_zones
- 1;
2878 balanced_classzone_idx
= classzone_idx
;
2883 * If the last balance_pgdat was unsuccessful it's unlikely a
2884 * new request of a similar or harder type will succeed soon
2885 * so consider going to sleep on the basis we reclaimed at
2887 if (balanced_classzone_idx
>= new_classzone_idx
&&
2888 balanced_order
== new_order
) {
2889 new_order
= pgdat
->kswapd_max_order
;
2890 new_classzone_idx
= pgdat
->classzone_idx
;
2891 pgdat
->kswapd_max_order
= 0;
2892 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
2895 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
2897 * Don't sleep if someone wants a larger 'order'
2898 * allocation or has tigher zone constraints
2901 classzone_idx
= new_classzone_idx
;
2903 kswapd_try_to_sleep(pgdat
, balanced_order
,
2904 balanced_classzone_idx
);
2905 order
= pgdat
->kswapd_max_order
;
2906 classzone_idx
= pgdat
->classzone_idx
;
2908 new_classzone_idx
= classzone_idx
;
2909 pgdat
->kswapd_max_order
= 0;
2910 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
2913 ret
= try_to_freeze();
2914 if (kthread_should_stop())
2918 * We can speed up thawing tasks if we don't call balance_pgdat
2919 * after returning from the refrigerator
2922 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
2923 balanced_classzone_idx
= classzone_idx
;
2924 balanced_order
= balance_pgdat(pgdat
, order
,
2925 &balanced_classzone_idx
);
2932 * A zone is low on free memory, so wake its kswapd task to service it.
2934 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
2938 if (!populated_zone(zone
))
2941 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2943 pgdat
= zone
->zone_pgdat
;
2944 if (pgdat
->kswapd_max_order
< order
) {
2945 pgdat
->kswapd_max_order
= order
;
2946 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
2948 if (!waitqueue_active(&pgdat
->kswapd_wait
))
2950 if (zone_watermark_ok_safe(zone
, order
, low_wmark_pages(zone
), 0, 0))
2953 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
2954 wake_up_interruptible(&pgdat
->kswapd_wait
);
2958 * The reclaimable count would be mostly accurate.
2959 * The less reclaimable pages may be
2960 * - mlocked pages, which will be moved to unevictable list when encountered
2961 * - mapped pages, which may require several travels to be reclaimed
2962 * - dirty pages, which is not "instantly" reclaimable
2964 unsigned long global_reclaimable_pages(void)
2968 nr
= global_page_state(NR_ACTIVE_FILE
) +
2969 global_page_state(NR_INACTIVE_FILE
);
2971 if (nr_swap_pages
> 0)
2972 nr
+= global_page_state(NR_ACTIVE_ANON
) +
2973 global_page_state(NR_INACTIVE_ANON
);
2978 unsigned long zone_reclaimable_pages(struct zone
*zone
)
2982 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
2983 zone_page_state(zone
, NR_INACTIVE_FILE
);
2985 if (nr_swap_pages
> 0)
2986 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
2987 zone_page_state(zone
, NR_INACTIVE_ANON
);
2992 #ifdef CONFIG_HIBERNATION
2994 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2997 * Rather than trying to age LRUs the aim is to preserve the overall
2998 * LRU order by reclaiming preferentially
2999 * inactive > active > active referenced > active mapped
3001 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
3003 struct reclaim_state reclaim_state
;
3004 struct scan_control sc
= {
3005 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
3009 .nr_to_reclaim
= nr_to_reclaim
,
3010 .hibernation_mode
= 1,
3013 struct shrink_control shrink
= {
3014 .gfp_mask
= sc
.gfp_mask
,
3016 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3017 struct task_struct
*p
= current
;
3018 unsigned long nr_reclaimed
;
3020 p
->flags
|= PF_MEMALLOC
;
3021 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
3022 reclaim_state
.reclaimed_slab
= 0;
3023 p
->reclaim_state
= &reclaim_state
;
3025 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
3027 p
->reclaim_state
= NULL
;
3028 lockdep_clear_current_reclaim_state();
3029 p
->flags
&= ~PF_MEMALLOC
;
3031 return nr_reclaimed
;
3033 #endif /* CONFIG_HIBERNATION */
3035 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3036 not required for correctness. So if the last cpu in a node goes
3037 away, we get changed to run anywhere: as the first one comes back,
3038 restore their cpu bindings. */
3039 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
3040 unsigned long action
, void *hcpu
)
3044 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
3045 for_each_node_state(nid
, N_HIGH_MEMORY
) {
3046 pg_data_t
*pgdat
= NODE_DATA(nid
);
3047 const struct cpumask
*mask
;
3049 mask
= cpumask_of_node(pgdat
->node_id
);
3051 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3052 /* One of our CPUs online: restore mask */
3053 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
3060 * This kswapd start function will be called by init and node-hot-add.
3061 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3063 int kswapd_run(int nid
)
3065 pg_data_t
*pgdat
= NODE_DATA(nid
);
3071 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
3072 if (IS_ERR(pgdat
->kswapd
)) {
3073 /* failure at boot is fatal */
3074 BUG_ON(system_state
== SYSTEM_BOOTING
);
3075 printk("Failed to start kswapd on node %d\n",nid
);
3082 * Called by memory hotplug when all memory in a node is offlined.
3084 void kswapd_stop(int nid
)
3086 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
3089 kthread_stop(kswapd
);
3092 static int __init
kswapd_init(void)
3097 for_each_node_state(nid
, N_HIGH_MEMORY
)
3099 hotcpu_notifier(cpu_callback
, 0);
3103 module_init(kswapd_init
)
3109 * If non-zero call zone_reclaim when the number of free pages falls below
3112 int zone_reclaim_mode __read_mostly
;
3114 #define RECLAIM_OFF 0
3115 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3116 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3117 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3120 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3121 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3124 #define ZONE_RECLAIM_PRIORITY 4
3127 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3130 int sysctl_min_unmapped_ratio
= 1;
3133 * If the number of slab pages in a zone grows beyond this percentage then
3134 * slab reclaim needs to occur.
3136 int sysctl_min_slab_ratio
= 5;
3138 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
3140 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
3141 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
3142 zone_page_state(zone
, NR_ACTIVE_FILE
);
3145 * It's possible for there to be more file mapped pages than
3146 * accounted for by the pages on the file LRU lists because
3147 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3149 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
3152 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3153 static long zone_pagecache_reclaimable(struct zone
*zone
)
3155 long nr_pagecache_reclaimable
;
3159 * If RECLAIM_SWAP is set, then all file pages are considered
3160 * potentially reclaimable. Otherwise, we have to worry about
3161 * pages like swapcache and zone_unmapped_file_pages() provides
3164 if (zone_reclaim_mode
& RECLAIM_SWAP
)
3165 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
3167 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
3169 /* If we can't clean pages, remove dirty pages from consideration */
3170 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
3171 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
3173 /* Watch for any possible underflows due to delta */
3174 if (unlikely(delta
> nr_pagecache_reclaimable
))
3175 delta
= nr_pagecache_reclaimable
;
3177 return nr_pagecache_reclaimable
- delta
;
3181 * Try to free up some pages from this zone through reclaim.
3183 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3185 /* Minimum pages needed in order to stay on node */
3186 const unsigned long nr_pages
= 1 << order
;
3187 struct task_struct
*p
= current
;
3188 struct reclaim_state reclaim_state
;
3190 struct scan_control sc
= {
3191 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
3192 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
3194 .nr_to_reclaim
= max_t(unsigned long, nr_pages
,
3196 .gfp_mask
= gfp_mask
,
3199 struct shrink_control shrink
= {
3200 .gfp_mask
= sc
.gfp_mask
,
3202 unsigned long nr_slab_pages0
, nr_slab_pages1
;
3206 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3207 * and we also need to be able to write out pages for RECLAIM_WRITE
3210 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
3211 lockdep_set_current_reclaim_state(gfp_mask
);
3212 reclaim_state
.reclaimed_slab
= 0;
3213 p
->reclaim_state
= &reclaim_state
;
3215 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
3217 * Free memory by calling shrink zone with increasing
3218 * priorities until we have enough memory freed.
3220 priority
= ZONE_RECLAIM_PRIORITY
;
3222 shrink_zone(priority
, zone
, &sc
);
3224 } while (priority
>= 0 && sc
.nr_reclaimed
< nr_pages
);
3227 nr_slab_pages0
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3228 if (nr_slab_pages0
> zone
->min_slab_pages
) {
3230 * shrink_slab() does not currently allow us to determine how
3231 * many pages were freed in this zone. So we take the current
3232 * number of slab pages and shake the slab until it is reduced
3233 * by the same nr_pages that we used for reclaiming unmapped
3236 * Note that shrink_slab will free memory on all zones and may
3240 unsigned long lru_pages
= zone_reclaimable_pages(zone
);
3242 /* No reclaimable slab or very low memory pressure */
3243 if (!shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
))
3246 /* Freed enough memory */
3247 nr_slab_pages1
= zone_page_state(zone
,
3248 NR_SLAB_RECLAIMABLE
);
3249 if (nr_slab_pages1
+ nr_pages
<= nr_slab_pages0
)
3254 * Update nr_reclaimed by the number of slab pages we
3255 * reclaimed from this zone.
3257 nr_slab_pages1
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3258 if (nr_slab_pages1
< nr_slab_pages0
)
3259 sc
.nr_reclaimed
+= nr_slab_pages0
- nr_slab_pages1
;
3262 p
->reclaim_state
= NULL
;
3263 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3264 lockdep_clear_current_reclaim_state();
3265 return sc
.nr_reclaimed
>= nr_pages
;
3268 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3274 * Zone reclaim reclaims unmapped file backed pages and
3275 * slab pages if we are over the defined limits.
3277 * A small portion of unmapped file backed pages is needed for
3278 * file I/O otherwise pages read by file I/O will be immediately
3279 * thrown out if the zone is overallocated. So we do not reclaim
3280 * if less than a specified percentage of the zone is used by
3281 * unmapped file backed pages.
3283 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3284 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3285 return ZONE_RECLAIM_FULL
;
3287 if (zone
->all_unreclaimable
)
3288 return ZONE_RECLAIM_FULL
;
3291 * Do not scan if the allocation should not be delayed.
3293 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3294 return ZONE_RECLAIM_NOSCAN
;
3297 * Only run zone reclaim on the local zone or on zones that do not
3298 * have associated processors. This will favor the local processor
3299 * over remote processors and spread off node memory allocations
3300 * as wide as possible.
3302 node_id
= zone_to_nid(zone
);
3303 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3304 return ZONE_RECLAIM_NOSCAN
;
3306 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
3307 return ZONE_RECLAIM_NOSCAN
;
3309 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3310 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
3313 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3320 * page_evictable - test whether a page is evictable
3321 * @page: the page to test
3322 * @vma: the VMA in which the page is or will be mapped, may be NULL
3324 * Test whether page is evictable--i.e., should be placed on active/inactive
3325 * lists vs unevictable list. The vma argument is !NULL when called from the
3326 * fault path to determine how to instantate a new page.
3328 * Reasons page might not be evictable:
3329 * (1) page's mapping marked unevictable
3330 * (2) page is part of an mlocked VMA
3333 int page_evictable(struct page
*page
, struct vm_area_struct
*vma
)
3336 if (mapping_unevictable(page_mapping(page
)))
3339 if (PageMlocked(page
) || (vma
&& is_mlocked_vma(vma
, page
)))
3346 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3347 * @page: page to check evictability and move to appropriate lru list
3348 * @zone: zone page is in
3350 * Checks a page for evictability and moves the page to the appropriate
3353 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3354 * have PageUnevictable set.
3356 static void check_move_unevictable_page(struct page
*page
, struct zone
*zone
)
3358 VM_BUG_ON(PageActive(page
));
3361 ClearPageUnevictable(page
);
3362 if (page_evictable(page
, NULL
)) {
3363 enum lru_list l
= page_lru_base_type(page
);
3365 __dec_zone_state(zone
, NR_UNEVICTABLE
);
3366 list_move(&page
->lru
, &zone
->lru
[l
].list
);
3367 mem_cgroup_move_lists(page
, LRU_UNEVICTABLE
, l
);
3368 __inc_zone_state(zone
, NR_INACTIVE_ANON
+ l
);
3369 __count_vm_event(UNEVICTABLE_PGRESCUED
);
3372 * rotate unevictable list
3374 SetPageUnevictable(page
);
3375 list_move(&page
->lru
, &zone
->lru
[LRU_UNEVICTABLE
].list
);
3376 mem_cgroup_rotate_lru_list(page
, LRU_UNEVICTABLE
);
3377 if (page_evictable(page
, NULL
))
3383 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3384 * @mapping: struct address_space to scan for evictable pages
3386 * Scan all pages in mapping. Check unevictable pages for
3387 * evictability and move them to the appropriate zone lru list.
3389 void scan_mapping_unevictable_pages(struct address_space
*mapping
)
3392 pgoff_t end
= (i_size_read(mapping
->host
) + PAGE_CACHE_SIZE
- 1) >>
3395 struct pagevec pvec
;
3397 if (mapping
->nrpages
== 0)
3400 pagevec_init(&pvec
, 0);
3401 while (next
< end
&&
3402 pagevec_lookup(&pvec
, mapping
, next
, PAGEVEC_SIZE
)) {
3408 for (i
= 0; i
< pagevec_count(&pvec
); i
++) {
3409 struct page
*page
= pvec
.pages
[i
];
3410 pgoff_t page_index
= page
->index
;
3411 struct zone
*pagezone
= page_zone(page
);
3414 if (page_index
> next
)
3418 if (pagezone
!= zone
) {
3420 spin_unlock_irq(&zone
->lru_lock
);
3422 spin_lock_irq(&zone
->lru_lock
);
3425 if (PageLRU(page
) && PageUnevictable(page
))
3426 check_move_unevictable_page(page
, zone
);
3429 spin_unlock_irq(&zone
->lru_lock
);
3430 pagevec_release(&pvec
);
3432 count_vm_events(UNEVICTABLE_PGSCANNED
, pg_scanned
);
3437 static void warn_scan_unevictable_pages(void)
3439 printk_once(KERN_WARNING
3440 "%s: The scan_unevictable_pages sysctl/node-interface has been "
3441 "disabled for lack of a legitimate use case. If you have "
3442 "one, please send an email to linux-mm@kvack.org.\n",
3447 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3448 * all nodes' unevictable lists for evictable pages
3450 unsigned long scan_unevictable_pages
;
3452 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
3453 void __user
*buffer
,
3454 size_t *length
, loff_t
*ppos
)
3456 warn_scan_unevictable_pages();
3457 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
3458 scan_unevictable_pages
= 0;
3464 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3465 * a specified node's per zone unevictable lists for evictable pages.
3468 static ssize_t
read_scan_unevictable_node(struct device
*dev
,
3469 struct device_attribute
*attr
,
3472 warn_scan_unevictable_pages();
3473 return sprintf(buf
, "0\n"); /* always zero; should fit... */
3476 static ssize_t
write_scan_unevictable_node(struct device
*dev
,
3477 struct device_attribute
*attr
,
3478 const char *buf
, size_t count
)
3480 warn_scan_unevictable_pages();
3485 static DEVICE_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
3486 read_scan_unevictable_node
,
3487 write_scan_unevictable_node
);
3489 int scan_unevictable_register_node(struct node
*node
)
3491 return device_create_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);
3494 void scan_unevictable_unregister_node(struct node
*node
)
3496 device_remove_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);