Root/
1 | /* |
2 | * linux/mm/vmscan.c |
3 | * |
4 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
5 | * |
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. |
12 | */ |
13 | |
14 | #include <linux/mm.h> |
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/backing-dev.h> |
30 | #include <linux/rmap.h> |
31 | #include <linux/topology.h> |
32 | #include <linux/cpu.h> |
33 | #include <linux/cpuset.h> |
34 | #include <linux/compaction.h> |
35 | #include <linux/notifier.h> |
36 | #include <linux/rwsem.h> |
37 | #include <linux/delay.h> |
38 | #include <linux/kthread.h> |
39 | #include <linux/freezer.h> |
40 | #include <linux/memcontrol.h> |
41 | #include <linux/delayacct.h> |
42 | #include <linux/sysctl.h> |
43 | #include <linux/oom.h> |
44 | #include <linux/prefetch.h> |
45 | |
46 | #include <asm/tlbflush.h> |
47 | #include <asm/div64.h> |
48 | |
49 | #include <linux/swapops.h> |
50 | |
51 | #include "internal.h" |
52 | |
53 | #define CREATE_TRACE_POINTS |
54 | #include <trace/events/vmscan.h> |
55 | |
56 | /* |
57 | * reclaim_mode determines how the inactive list is shrunk |
58 | * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages |
59 | * RECLAIM_MODE_ASYNC: Do not block |
60 | * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback |
61 | * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference |
62 | * page from the LRU and reclaim all pages within a |
63 | * naturally aligned range |
64 | * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of |
65 | * order-0 pages and then compact the zone |
66 | */ |
67 | typedef unsigned __bitwise__ reclaim_mode_t; |
68 | #define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u) |
69 | #define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u) |
70 | #define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u) |
71 | #define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u) |
72 | #define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u) |
73 | |
74 | struct scan_control { |
75 | /* Incremented by the number of inactive pages that were scanned */ |
76 | unsigned long nr_scanned; |
77 | |
78 | /* Number of pages freed so far during a call to shrink_zones() */ |
79 | unsigned long nr_reclaimed; |
80 | |
81 | /* How many pages shrink_list() should reclaim */ |
82 | unsigned long nr_to_reclaim; |
83 | |
84 | unsigned long hibernation_mode; |
85 | |
86 | /* This context's GFP mask */ |
87 | gfp_t gfp_mask; |
88 | |
89 | int may_writepage; |
90 | |
91 | /* Can mapped pages be reclaimed? */ |
92 | int may_unmap; |
93 | |
94 | /* Can pages be swapped as part of reclaim? */ |
95 | int may_swap; |
96 | |
97 | int order; |
98 | |
99 | /* |
100 | * Intend to reclaim enough continuous memory rather than reclaim |
101 | * enough amount of memory. i.e, mode for high order allocation. |
102 | */ |
103 | reclaim_mode_t reclaim_mode; |
104 | |
105 | /* |
106 | * The memory cgroup that hit its limit and as a result is the |
107 | * primary target of this reclaim invocation. |
108 | */ |
109 | struct mem_cgroup *target_mem_cgroup; |
110 | |
111 | /* |
112 | * Nodemask of nodes allowed by the caller. If NULL, all nodes |
113 | * are scanned. |
114 | */ |
115 | nodemask_t *nodemask; |
116 | }; |
117 | |
118 | struct mem_cgroup_zone { |
119 | struct mem_cgroup *mem_cgroup; |
120 | struct zone *zone; |
121 | }; |
122 | |
123 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) |
124 | |
125 | #ifdef ARCH_HAS_PREFETCH |
126 | #define prefetch_prev_lru_page(_page, _base, _field) \ |
127 | do { \ |
128 | if ((_page)->lru.prev != _base) { \ |
129 | struct page *prev; \ |
130 | \ |
131 | prev = lru_to_page(&(_page->lru)); \ |
132 | prefetch(&prev->_field); \ |
133 | } \ |
134 | } while (0) |
135 | #else |
136 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) |
137 | #endif |
138 | |
139 | #ifdef ARCH_HAS_PREFETCHW |
140 | #define prefetchw_prev_lru_page(_page, _base, _field) \ |
141 | do { \ |
142 | if ((_page)->lru.prev != _base) { \ |
143 | struct page *prev; \ |
144 | \ |
145 | prev = lru_to_page(&(_page->lru)); \ |
146 | prefetchw(&prev->_field); \ |
147 | } \ |
148 | } while (0) |
149 | #else |
150 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) |
151 | #endif |
152 | |
153 | /* |
154 | * From 0 .. 100. Higher means more swappy. |
155 | */ |
156 | int vm_swappiness = 60; |
157 | long vm_total_pages; /* The total number of pages which the VM controls */ |
158 | |
159 | static LIST_HEAD(shrinker_list); |
160 | static DECLARE_RWSEM(shrinker_rwsem); |
161 | |
162 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
163 | static bool global_reclaim(struct scan_control *sc) |
164 | { |
165 | return !sc->target_mem_cgroup; |
166 | } |
167 | |
168 | static bool scanning_global_lru(struct mem_cgroup_zone *mz) |
169 | { |
170 | return !mz->mem_cgroup; |
171 | } |
172 | #else |
173 | static bool global_reclaim(struct scan_control *sc) |
174 | { |
175 | return true; |
176 | } |
177 | |
178 | static bool scanning_global_lru(struct mem_cgroup_zone *mz) |
179 | { |
180 | return true; |
181 | } |
182 | #endif |
183 | |
184 | static struct zone_reclaim_stat *get_reclaim_stat(struct mem_cgroup_zone *mz) |
185 | { |
186 | if (!scanning_global_lru(mz)) |
187 | return mem_cgroup_get_reclaim_stat(mz->mem_cgroup, mz->zone); |
188 | |
189 | return &mz->zone->reclaim_stat; |
190 | } |
191 | |
192 | static unsigned long zone_nr_lru_pages(struct mem_cgroup_zone *mz, |
193 | enum lru_list lru) |
194 | { |
195 | if (!scanning_global_lru(mz)) |
196 | return mem_cgroup_zone_nr_lru_pages(mz->mem_cgroup, |
197 | zone_to_nid(mz->zone), |
198 | zone_idx(mz->zone), |
199 | BIT(lru)); |
200 | |
201 | return zone_page_state(mz->zone, NR_LRU_BASE + lru); |
202 | } |
203 | |
204 | |
205 | /* |
206 | * Add a shrinker callback to be called from the vm |
207 | */ |
208 | void register_shrinker(struct shrinker *shrinker) |
209 | { |
210 | atomic_long_set(&shrinker->nr_in_batch, 0); |
211 | down_write(&shrinker_rwsem); |
212 | list_add_tail(&shrinker->list, &shrinker_list); |
213 | up_write(&shrinker_rwsem); |
214 | } |
215 | EXPORT_SYMBOL(register_shrinker); |
216 | |
217 | /* |
218 | * Remove one |
219 | */ |
220 | void unregister_shrinker(struct shrinker *shrinker) |
221 | { |
222 | down_write(&shrinker_rwsem); |
223 | list_del(&shrinker->list); |
224 | up_write(&shrinker_rwsem); |
225 | } |
226 | EXPORT_SYMBOL(unregister_shrinker); |
227 | |
228 | static inline int do_shrinker_shrink(struct shrinker *shrinker, |
229 | struct shrink_control *sc, |
230 | unsigned long nr_to_scan) |
231 | { |
232 | sc->nr_to_scan = nr_to_scan; |
233 | return (*shrinker->shrink)(shrinker, sc); |
234 | } |
235 | |
236 | #define SHRINK_BATCH 128 |
237 | /* |
238 | * Call the shrink functions to age shrinkable caches |
239 | * |
240 | * Here we assume it costs one seek to replace a lru page and that it also |
241 | * takes a seek to recreate a cache object. With this in mind we age equal |
242 | * percentages of the lru and ageable caches. This should balance the seeks |
243 | * generated by these structures. |
244 | * |
245 | * If the vm encountered mapped pages on the LRU it increase the pressure on |
246 | * slab to avoid swapping. |
247 | * |
248 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. |
249 | * |
250 | * `lru_pages' represents the number of on-LRU pages in all the zones which |
251 | * are eligible for the caller's allocation attempt. It is used for balancing |
252 | * slab reclaim versus page reclaim. |
253 | * |
254 | * Returns the number of slab objects which we shrunk. |
255 | */ |
256 | unsigned long shrink_slab(struct shrink_control *shrink, |
257 | unsigned long nr_pages_scanned, |
258 | unsigned long lru_pages) |
259 | { |
260 | struct shrinker *shrinker; |
261 | unsigned long ret = 0; |
262 | |
263 | if (nr_pages_scanned == 0) |
264 | nr_pages_scanned = SWAP_CLUSTER_MAX; |
265 | |
266 | if (!down_read_trylock(&shrinker_rwsem)) { |
267 | /* Assume we'll be able to shrink next time */ |
268 | ret = 1; |
269 | goto out; |
270 | } |
271 | |
272 | list_for_each_entry(shrinker, &shrinker_list, list) { |
273 | unsigned long long delta; |
274 | long total_scan; |
275 | long max_pass; |
276 | int shrink_ret = 0; |
277 | long nr; |
278 | long new_nr; |
279 | long batch_size = shrinker->batch ? shrinker->batch |
280 | : SHRINK_BATCH; |
281 | |
282 | max_pass = do_shrinker_shrink(shrinker, shrink, 0); |
283 | if (max_pass <= 0) |
284 | continue; |
285 | |
286 | /* |
287 | * copy the current shrinker scan count into a local variable |
288 | * and zero it so that other concurrent shrinker invocations |
289 | * don't also do this scanning work. |
290 | */ |
291 | nr = atomic_long_xchg(&shrinker->nr_in_batch, 0); |
292 | |
293 | total_scan = nr; |
294 | delta = (4 * nr_pages_scanned) / shrinker->seeks; |
295 | delta *= max_pass; |
296 | do_div(delta, lru_pages + 1); |
297 | total_scan += delta; |
298 | if (total_scan < 0) { |
299 | printk(KERN_ERR "shrink_slab: %pF negative objects to " |
300 | "delete nr=%ld\n", |
301 | shrinker->shrink, total_scan); |
302 | total_scan = max_pass; |
303 | } |
304 | |
305 | /* |
306 | * We need to avoid excessive windup on filesystem shrinkers |
307 | * due to large numbers of GFP_NOFS allocations causing the |
308 | * shrinkers to return -1 all the time. This results in a large |
309 | * nr being built up so when a shrink that can do some work |
310 | * comes along it empties the entire cache due to nr >>> |
311 | * max_pass. This is bad for sustaining a working set in |
312 | * memory. |
313 | * |
314 | * Hence only allow the shrinker to scan the entire cache when |
315 | * a large delta change is calculated directly. |
316 | */ |
317 | if (delta < max_pass / 4) |
318 | total_scan = min(total_scan, max_pass / 2); |
319 | |
320 | /* |
321 | * Avoid risking looping forever due to too large nr value: |
322 | * never try to free more than twice the estimate number of |
323 | * freeable entries. |
324 | */ |
325 | if (total_scan > max_pass * 2) |
326 | total_scan = max_pass * 2; |
327 | |
328 | trace_mm_shrink_slab_start(shrinker, shrink, nr, |
329 | nr_pages_scanned, lru_pages, |
330 | max_pass, delta, total_scan); |
331 | |
332 | while (total_scan >= batch_size) { |
333 | int nr_before; |
334 | |
335 | nr_before = do_shrinker_shrink(shrinker, shrink, 0); |
336 | shrink_ret = do_shrinker_shrink(shrinker, shrink, |
337 | batch_size); |
338 | if (shrink_ret == -1) |
339 | break; |
340 | if (shrink_ret < nr_before) |
341 | ret += nr_before - shrink_ret; |
342 | count_vm_events(SLABS_SCANNED, batch_size); |
343 | total_scan -= batch_size; |
344 | |
345 | cond_resched(); |
346 | } |
347 | |
348 | /* |
349 | * move the unused scan count back into the shrinker in a |
350 | * manner that handles concurrent updates. If we exhausted the |
351 | * scan, there is no need to do an update. |
352 | */ |
353 | if (total_scan > 0) |
354 | new_nr = atomic_long_add_return(total_scan, |
355 | &shrinker->nr_in_batch); |
356 | else |
357 | new_nr = atomic_long_read(&shrinker->nr_in_batch); |
358 | |
359 | trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr); |
360 | } |
361 | up_read(&shrinker_rwsem); |
362 | out: |
363 | cond_resched(); |
364 | return ret; |
365 | } |
366 | |
367 | static void set_reclaim_mode(int priority, struct scan_control *sc, |
368 | bool sync) |
369 | { |
370 | reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; |
371 | |
372 | /* |
373 | * Initially assume we are entering either lumpy reclaim or |
374 | * reclaim/compaction.Depending on the order, we will either set the |
375 | * sync mode or just reclaim order-0 pages later. |
376 | */ |
377 | if (COMPACTION_BUILD) |
378 | sc->reclaim_mode = RECLAIM_MODE_COMPACTION; |
379 | else |
380 | sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; |
381 | |
382 | /* |
383 | * Avoid using lumpy reclaim or reclaim/compaction if possible by |
384 | * restricting when its set to either costly allocations or when |
385 | * under memory pressure |
386 | */ |
387 | if (sc->order > PAGE_ALLOC_COSTLY_ORDER) |
388 | sc->reclaim_mode |= syncmode; |
389 | else if (sc->order && priority < DEF_PRIORITY - 2) |
390 | sc->reclaim_mode |= syncmode; |
391 | else |
392 | sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; |
393 | } |
394 | |
395 | static void reset_reclaim_mode(struct scan_control *sc) |
396 | { |
397 | sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; |
398 | } |
399 | |
400 | static inline int is_page_cache_freeable(struct page *page) |
401 | { |
402 | /* |
403 | * A freeable page cache page is referenced only by the caller |
404 | * that isolated the page, the page cache radix tree and |
405 | * optional buffer heads at page->private. |
406 | */ |
407 | return page_count(page) - page_has_private(page) == 2; |
408 | } |
409 | |
410 | static int may_write_to_queue(struct backing_dev_info *bdi, |
411 | struct scan_control *sc) |
412 | { |
413 | if (current->flags & PF_SWAPWRITE) |
414 | return 1; |
415 | if (!bdi_write_congested(bdi)) |
416 | return 1; |
417 | if (bdi == current->backing_dev_info) |
418 | return 1; |
419 | |
420 | /* lumpy reclaim for hugepage often need a lot of write */ |
421 | if (sc->order > PAGE_ALLOC_COSTLY_ORDER) |
422 | return 1; |
423 | return 0; |
424 | } |
425 | |
426 | /* |
427 | * We detected a synchronous write error writing a page out. Probably |
428 | * -ENOSPC. We need to propagate that into the address_space for a subsequent |
429 | * fsync(), msync() or close(). |
430 | * |
431 | * The tricky part is that after writepage we cannot touch the mapping: nothing |
432 | * prevents it from being freed up. But we have a ref on the page and once |
433 | * that page is locked, the mapping is pinned. |
434 | * |
435 | * We're allowed to run sleeping lock_page() here because we know the caller has |
436 | * __GFP_FS. |
437 | */ |
438 | static void handle_write_error(struct address_space *mapping, |
439 | struct page *page, int error) |
440 | { |
441 | lock_page(page); |
442 | if (page_mapping(page) == mapping) |
443 | mapping_set_error(mapping, error); |
444 | unlock_page(page); |
445 | } |
446 | |
447 | /* possible outcome of pageout() */ |
448 | typedef enum { |
449 | /* failed to write page out, page is locked */ |
450 | PAGE_KEEP, |
451 | /* move page to the active list, page is locked */ |
452 | PAGE_ACTIVATE, |
453 | /* page has been sent to the disk successfully, page is unlocked */ |
454 | PAGE_SUCCESS, |
455 | /* page is clean and locked */ |
456 | PAGE_CLEAN, |
457 | } pageout_t; |
458 | |
459 | /* |
460 | * pageout is called by shrink_page_list() for each dirty page. |
461 | * Calls ->writepage(). |
462 | */ |
463 | static pageout_t pageout(struct page *page, struct address_space *mapping, |
464 | struct scan_control *sc) |
465 | { |
466 | /* |
467 | * If the page is dirty, only perform writeback if that write |
468 | * will be non-blocking. To prevent this allocation from being |
469 | * stalled by pagecache activity. But note that there may be |
470 | * stalls if we need to run get_block(). We could test |
471 | * PagePrivate for that. |
472 | * |
473 | * If this process is currently in __generic_file_aio_write() against |
474 | * this page's queue, we can perform writeback even if that |
475 | * will block. |
476 | * |
477 | * If the page is swapcache, write it back even if that would |
478 | * block, for some throttling. This happens by accident, because |
479 | * swap_backing_dev_info is bust: it doesn't reflect the |
480 | * congestion state of the swapdevs. Easy to fix, if needed. |
481 | */ |
482 | if (!is_page_cache_freeable(page)) |
483 | return PAGE_KEEP; |
484 | if (!mapping) { |
485 | /* |
486 | * Some data journaling orphaned pages can have |
487 | * page->mapping == NULL while being dirty with clean buffers. |
488 | */ |
489 | if (page_has_private(page)) { |
490 | if (try_to_free_buffers(page)) { |
491 | ClearPageDirty(page); |
492 | printk("%s: orphaned page\n", __func__); |
493 | return PAGE_CLEAN; |
494 | } |
495 | } |
496 | return PAGE_KEEP; |
497 | } |
498 | if (mapping->a_ops->writepage == NULL) |
499 | return PAGE_ACTIVATE; |
500 | if (!may_write_to_queue(mapping->backing_dev_info, sc)) |
501 | return PAGE_KEEP; |
502 | |
503 | if (clear_page_dirty_for_io(page)) { |
504 | int res; |
505 | struct writeback_control wbc = { |
506 | .sync_mode = WB_SYNC_NONE, |
507 | .nr_to_write = SWAP_CLUSTER_MAX, |
508 | .range_start = 0, |
509 | .range_end = LLONG_MAX, |
510 | .for_reclaim = 1, |
511 | }; |
512 | |
513 | SetPageReclaim(page); |
514 | res = mapping->a_ops->writepage(page, &wbc); |
515 | if (res < 0) |
516 | handle_write_error(mapping, page, res); |
517 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
518 | ClearPageReclaim(page); |
519 | return PAGE_ACTIVATE; |
520 | } |
521 | |
522 | if (!PageWriteback(page)) { |
523 | /* synchronous write or broken a_ops? */ |
524 | ClearPageReclaim(page); |
525 | } |
526 | trace_mm_vmscan_writepage(page, |
527 | trace_reclaim_flags(page, sc->reclaim_mode)); |
528 | inc_zone_page_state(page, NR_VMSCAN_WRITE); |
529 | return PAGE_SUCCESS; |
530 | } |
531 | |
532 | return PAGE_CLEAN; |
533 | } |
534 | |
535 | /* |
536 | * Same as remove_mapping, but if the page is removed from the mapping, it |
537 | * gets returned with a refcount of 0. |
538 | */ |
539 | static int __remove_mapping(struct address_space *mapping, struct page *page) |
540 | { |
541 | BUG_ON(!PageLocked(page)); |
542 | BUG_ON(mapping != page_mapping(page)); |
543 | |
544 | spin_lock_irq(&mapping->tree_lock); |
545 | /* |
546 | * The non racy check for a busy page. |
547 | * |
548 | * Must be careful with the order of the tests. When someone has |
549 | * a ref to the page, it may be possible that they dirty it then |
550 | * drop the reference. So if PageDirty is tested before page_count |
551 | * here, then the following race may occur: |
552 | * |
553 | * get_user_pages(&page); |
554 | * [user mapping goes away] |
555 | * write_to(page); |
556 | * !PageDirty(page) [good] |
557 | * SetPageDirty(page); |
558 | * put_page(page); |
559 | * !page_count(page) [good, discard it] |
560 | * |
561 | * [oops, our write_to data is lost] |
562 | * |
563 | * Reversing the order of the tests ensures such a situation cannot |
564 | * escape unnoticed. The smp_rmb is needed to ensure the page->flags |
565 | * load is not satisfied before that of page->_count. |
566 | * |
567 | * Note that if SetPageDirty is always performed via set_page_dirty, |
568 | * and thus under tree_lock, then this ordering is not required. |
569 | */ |
570 | if (!page_freeze_refs(page, 2)) |
571 | goto cannot_free; |
572 | /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ |
573 | if (unlikely(PageDirty(page))) { |
574 | page_unfreeze_refs(page, 2); |
575 | goto cannot_free; |
576 | } |
577 | |
578 | if (PageSwapCache(page)) { |
579 | swp_entry_t swap = { .val = page_private(page) }; |
580 | __delete_from_swap_cache(page); |
581 | spin_unlock_irq(&mapping->tree_lock); |
582 | swapcache_free(swap, page); |
583 | } else { |
584 | void (*freepage)(struct page *); |
585 | |
586 | freepage = mapping->a_ops->freepage; |
587 | |
588 | __delete_from_page_cache(page); |
589 | spin_unlock_irq(&mapping->tree_lock); |
590 | mem_cgroup_uncharge_cache_page(page); |
591 | |
592 | if (freepage != NULL) |
593 | freepage(page); |
594 | } |
595 | |
596 | return 1; |
597 | |
598 | cannot_free: |
599 | spin_unlock_irq(&mapping->tree_lock); |
600 | return 0; |
601 | } |
602 | |
603 | /* |
604 | * Attempt to detach a locked page from its ->mapping. If it is dirty or if |
605 | * someone else has a ref on the page, abort and return 0. If it was |
606 | * successfully detached, return 1. Assumes the caller has a single ref on |
607 | * this page. |
608 | */ |
609 | int remove_mapping(struct address_space *mapping, struct page *page) |
610 | { |
611 | if (__remove_mapping(mapping, page)) { |
612 | /* |
613 | * Unfreezing the refcount with 1 rather than 2 effectively |
614 | * drops the pagecache ref for us without requiring another |
615 | * atomic operation. |
616 | */ |
617 | page_unfreeze_refs(page, 1); |
618 | return 1; |
619 | } |
620 | return 0; |
621 | } |
622 | |
623 | /** |
624 | * putback_lru_page - put previously isolated page onto appropriate LRU list |
625 | * @page: page to be put back to appropriate lru list |
626 | * |
627 | * Add previously isolated @page to appropriate LRU list. |
628 | * Page may still be unevictable for other reasons. |
629 | * |
630 | * lru_lock must not be held, interrupts must be enabled. |
631 | */ |
632 | void putback_lru_page(struct page *page) |
633 | { |
634 | int lru; |
635 | int active = !!TestClearPageActive(page); |
636 | int was_unevictable = PageUnevictable(page); |
637 | |
638 | VM_BUG_ON(PageLRU(page)); |
639 | |
640 | redo: |
641 | ClearPageUnevictable(page); |
642 | |
643 | if (page_evictable(page, NULL)) { |
644 | /* |
645 | * For evictable pages, we can use the cache. |
646 | * In event of a race, worst case is we end up with an |
647 | * unevictable page on [in]active list. |
648 | * We know how to handle that. |
649 | */ |
650 | lru = active + page_lru_base_type(page); |
651 | lru_cache_add_lru(page, lru); |
652 | } else { |
653 | /* |
654 | * Put unevictable pages directly on zone's unevictable |
655 | * list. |
656 | */ |
657 | lru = LRU_UNEVICTABLE; |
658 | add_page_to_unevictable_list(page); |
659 | /* |
660 | * When racing with an mlock or AS_UNEVICTABLE clearing |
661 | * (page is unlocked) make sure that if the other thread |
662 | * does not observe our setting of PG_lru and fails |
663 | * isolation/check_move_unevictable_pages, |
664 | * we see PG_mlocked/AS_UNEVICTABLE cleared below and move |
665 | * the page back to the evictable list. |
666 | * |
667 | * The other side is TestClearPageMlocked() or shmem_lock(). |
668 | */ |
669 | smp_mb(); |
670 | } |
671 | |
672 | /* |
673 | * page's status can change while we move it among lru. If an evictable |
674 | * page is on unevictable list, it never be freed. To avoid that, |
675 | * check after we added it to the list, again. |
676 | */ |
677 | if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { |
678 | if (!isolate_lru_page(page)) { |
679 | put_page(page); |
680 | goto redo; |
681 | } |
682 | /* This means someone else dropped this page from LRU |
683 | * So, it will be freed or putback to LRU again. There is |
684 | * nothing to do here. |
685 | */ |
686 | } |
687 | |
688 | if (was_unevictable && lru != LRU_UNEVICTABLE) |
689 | count_vm_event(UNEVICTABLE_PGRESCUED); |
690 | else if (!was_unevictable && lru == LRU_UNEVICTABLE) |
691 | count_vm_event(UNEVICTABLE_PGCULLED); |
692 | |
693 | put_page(page); /* drop ref from isolate */ |
694 | } |
695 | |
696 | enum page_references { |
697 | PAGEREF_RECLAIM, |
698 | PAGEREF_RECLAIM_CLEAN, |
699 | PAGEREF_KEEP, |
700 | PAGEREF_ACTIVATE, |
701 | }; |
702 | |
703 | static enum page_references page_check_references(struct page *page, |
704 | struct mem_cgroup_zone *mz, |
705 | struct scan_control *sc) |
706 | { |
707 | int referenced_ptes, referenced_page; |
708 | unsigned long vm_flags; |
709 | |
710 | referenced_ptes = page_referenced(page, 1, mz->mem_cgroup, &vm_flags); |
711 | referenced_page = TestClearPageReferenced(page); |
712 | |
713 | /* Lumpy reclaim - ignore references */ |
714 | if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) |
715 | return PAGEREF_RECLAIM; |
716 | |
717 | /* |
718 | * Mlock lost the isolation race with us. Let try_to_unmap() |
719 | * move the page to the unevictable list. |
720 | */ |
721 | if (vm_flags & VM_LOCKED) |
722 | return PAGEREF_RECLAIM; |
723 | |
724 | if (referenced_ptes) { |
725 | if (PageAnon(page)) |
726 | return PAGEREF_ACTIVATE; |
727 | /* |
728 | * All mapped pages start out with page table |
729 | * references from the instantiating fault, so we need |
730 | * to look twice if a mapped file page is used more |
731 | * than once. |
732 | * |
733 | * Mark it and spare it for another trip around the |
734 | * inactive list. Another page table reference will |
735 | * lead to its activation. |
736 | * |
737 | * Note: the mark is set for activated pages as well |
738 | * so that recently deactivated but used pages are |
739 | * quickly recovered. |
740 | */ |
741 | SetPageReferenced(page); |
742 | |
743 | if (referenced_page || referenced_ptes > 1) |
744 | return PAGEREF_ACTIVATE; |
745 | |
746 | /* |
747 | * Activate file-backed executable pages after first usage. |
748 | */ |
749 | if (vm_flags & VM_EXEC) |
750 | return PAGEREF_ACTIVATE; |
751 | |
752 | return PAGEREF_KEEP; |
753 | } |
754 | |
755 | /* Reclaim if clean, defer dirty pages to writeback */ |
756 | if (referenced_page && !PageSwapBacked(page)) |
757 | return PAGEREF_RECLAIM_CLEAN; |
758 | |
759 | return PAGEREF_RECLAIM; |
760 | } |
761 | |
762 | /* |
763 | * shrink_page_list() returns the number of reclaimed pages |
764 | */ |
765 | static unsigned long shrink_page_list(struct list_head *page_list, |
766 | struct mem_cgroup_zone *mz, |
767 | struct scan_control *sc, |
768 | int priority, |
769 | unsigned long *ret_nr_dirty, |
770 | unsigned long *ret_nr_writeback) |
771 | { |
772 | LIST_HEAD(ret_pages); |
773 | LIST_HEAD(free_pages); |
774 | int pgactivate = 0; |
775 | unsigned long nr_dirty = 0; |
776 | unsigned long nr_congested = 0; |
777 | unsigned long nr_reclaimed = 0; |
778 | unsigned long nr_writeback = 0; |
779 | |
780 | cond_resched(); |
781 | |
782 | while (!list_empty(page_list)) { |
783 | enum page_references references; |
784 | struct address_space *mapping; |
785 | struct page *page; |
786 | int may_enter_fs; |
787 | |
788 | cond_resched(); |
789 | |
790 | page = lru_to_page(page_list); |
791 | list_del(&page->lru); |
792 | |
793 | if (!trylock_page(page)) |
794 | goto keep; |
795 | |
796 | VM_BUG_ON(PageActive(page)); |
797 | VM_BUG_ON(page_zone(page) != mz->zone); |
798 | |
799 | sc->nr_scanned++; |
800 | |
801 | if (unlikely(!page_evictable(page, NULL))) |
802 | goto cull_mlocked; |
803 | |
804 | if (!sc->may_unmap && page_mapped(page)) |
805 | goto keep_locked; |
806 | |
807 | /* Double the slab pressure for mapped and swapcache pages */ |
808 | if (page_mapped(page) || PageSwapCache(page)) |
809 | sc->nr_scanned++; |
810 | |
811 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || |
812 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); |
813 | |
814 | if (PageWriteback(page)) { |
815 | nr_writeback++; |
816 | /* |
817 | * Synchronous reclaim cannot queue pages for |
818 | * writeback due to the possibility of stack overflow |
819 | * but if it encounters a page under writeback, wait |
820 | * for the IO to complete. |
821 | */ |
822 | if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && |
823 | may_enter_fs) |
824 | wait_on_page_writeback(page); |
825 | else { |
826 | unlock_page(page); |
827 | goto keep_lumpy; |
828 | } |
829 | } |
830 | |
831 | references = page_check_references(page, mz, sc); |
832 | switch (references) { |
833 | case PAGEREF_ACTIVATE: |
834 | goto activate_locked; |
835 | case PAGEREF_KEEP: |
836 | goto keep_locked; |
837 | case PAGEREF_RECLAIM: |
838 | case PAGEREF_RECLAIM_CLEAN: |
839 | ; /* try to reclaim the page below */ |
840 | } |
841 | |
842 | /* |
843 | * Anonymous process memory has backing store? |
844 | * Try to allocate it some swap space here. |
845 | */ |
846 | if (PageAnon(page) && !PageSwapCache(page)) { |
847 | if (!(sc->gfp_mask & __GFP_IO)) |
848 | goto keep_locked; |
849 | if (!add_to_swap(page)) |
850 | goto activate_locked; |
851 | may_enter_fs = 1; |
852 | } |
853 | |
854 | mapping = page_mapping(page); |
855 | |
856 | /* |
857 | * The page is mapped into the page tables of one or more |
858 | * processes. Try to unmap it here. |
859 | */ |
860 | if (page_mapped(page) && mapping) { |
861 | switch (try_to_unmap(page, TTU_UNMAP)) { |
862 | case SWAP_FAIL: |
863 | goto activate_locked; |
864 | case SWAP_AGAIN: |
865 | goto keep_locked; |
866 | case SWAP_MLOCK: |
867 | goto cull_mlocked; |
868 | case SWAP_SUCCESS: |
869 | ; /* try to free the page below */ |
870 | } |
871 | } |
872 | |
873 | if (PageDirty(page)) { |
874 | nr_dirty++; |
875 | |
876 | /* |
877 | * Only kswapd can writeback filesystem pages to |
878 | * avoid risk of stack overflow but do not writeback |
879 | * unless under significant pressure. |
880 | */ |
881 | if (page_is_file_cache(page) && |
882 | (!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) { |
883 | /* |
884 | * Immediately reclaim when written back. |
885 | * Similar in principal to deactivate_page() |
886 | * except we already have the page isolated |
887 | * and know it's dirty |
888 | */ |
889 | inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE); |
890 | SetPageReclaim(page); |
891 | |
892 | goto keep_locked; |
893 | } |
894 | |
895 | if (references == PAGEREF_RECLAIM_CLEAN) |
896 | goto keep_locked; |
897 | if (!may_enter_fs) |
898 | goto keep_locked; |
899 | if (!sc->may_writepage) |
900 | goto keep_locked; |
901 | |
902 | /* Page is dirty, try to write it out here */ |
903 | switch (pageout(page, mapping, sc)) { |
904 | case PAGE_KEEP: |
905 | nr_congested++; |
906 | goto keep_locked; |
907 | case PAGE_ACTIVATE: |
908 | goto activate_locked; |
909 | case PAGE_SUCCESS: |
910 | if (PageWriteback(page)) |
911 | goto keep_lumpy; |
912 | if (PageDirty(page)) |
913 | goto keep; |
914 | |
915 | /* |
916 | * A synchronous write - probably a ramdisk. Go |
917 | * ahead and try to reclaim the page. |
918 | */ |
919 | if (!trylock_page(page)) |
920 | goto keep; |
921 | if (PageDirty(page) || PageWriteback(page)) |
922 | goto keep_locked; |
923 | mapping = page_mapping(page); |
924 | case PAGE_CLEAN: |
925 | ; /* try to free the page below */ |
926 | } |
927 | } |
928 | |
929 | /* |
930 | * If the page has buffers, try to free the buffer mappings |
931 | * associated with this page. If we succeed we try to free |
932 | * the page as well. |
933 | * |
934 | * We do this even if the page is PageDirty(). |
935 | * try_to_release_page() does not perform I/O, but it is |
936 | * possible for a page to have PageDirty set, but it is actually |
937 | * clean (all its buffers are clean). This happens if the |
938 | * buffers were written out directly, with submit_bh(). ext3 |
939 | * will do this, as well as the blockdev mapping. |
940 | * try_to_release_page() will discover that cleanness and will |
941 | * drop the buffers and mark the page clean - it can be freed. |
942 | * |
943 | * Rarely, pages can have buffers and no ->mapping. These are |
944 | * the pages which were not successfully invalidated in |
945 | * truncate_complete_page(). We try to drop those buffers here |
946 | * and if that worked, and the page is no longer mapped into |
947 | * process address space (page_count == 1) it can be freed. |
948 | * Otherwise, leave the page on the LRU so it is swappable. |
949 | */ |
950 | if (page_has_private(page)) { |
951 | if (!try_to_release_page(page, sc->gfp_mask)) |
952 | goto activate_locked; |
953 | if (!mapping && page_count(page) == 1) { |
954 | unlock_page(page); |
955 | if (put_page_testzero(page)) |
956 | goto free_it; |
957 | else { |
958 | /* |
959 | * rare race with speculative reference. |
960 | * the speculative reference will free |
961 | * this page shortly, so we may |
962 | * increment nr_reclaimed here (and |
963 | * leave it off the LRU). |
964 | */ |
965 | nr_reclaimed++; |
966 | continue; |
967 | } |
968 | } |
969 | } |
970 | |
971 | if (!mapping || !__remove_mapping(mapping, page)) |
972 | goto keep_locked; |
973 | |
974 | /* |
975 | * At this point, we have no other references and there is |
976 | * no way to pick any more up (removed from LRU, removed |
977 | * from pagecache). Can use non-atomic bitops now (and |
978 | * we obviously don't have to worry about waking up a process |
979 | * waiting on the page lock, because there are no references. |
980 | */ |
981 | __clear_page_locked(page); |
982 | free_it: |
983 | nr_reclaimed++; |
984 | |
985 | /* |
986 | * Is there need to periodically free_page_list? It would |
987 | * appear not as the counts should be low |
988 | */ |
989 | list_add(&page->lru, &free_pages); |
990 | continue; |
991 | |
992 | cull_mlocked: |
993 | if (PageSwapCache(page)) |
994 | try_to_free_swap(page); |
995 | unlock_page(page); |
996 | putback_lru_page(page); |
997 | reset_reclaim_mode(sc); |
998 | continue; |
999 | |
1000 | activate_locked: |
1001 | /* Not a candidate for swapping, so reclaim swap space. */ |
1002 | if (PageSwapCache(page) && vm_swap_full()) |
1003 | try_to_free_swap(page); |
1004 | VM_BUG_ON(PageActive(page)); |
1005 | SetPageActive(page); |
1006 | pgactivate++; |
1007 | keep_locked: |
1008 | unlock_page(page); |
1009 | keep: |
1010 | reset_reclaim_mode(sc); |
1011 | keep_lumpy: |
1012 | list_add(&page->lru, &ret_pages); |
1013 | VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); |
1014 | } |
1015 | |
1016 | /* |
1017 | * Tag a zone as congested if all the dirty pages encountered were |
1018 | * backed by a congested BDI. In this case, reclaimers should just |
1019 | * back off and wait for congestion to clear because further reclaim |
1020 | * will encounter the same problem |
1021 | */ |
1022 | if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc)) |
1023 | zone_set_flag(mz->zone, ZONE_CONGESTED); |
1024 | |
1025 | free_hot_cold_page_list(&free_pages, 1); |
1026 | |
1027 | list_splice(&ret_pages, page_list); |
1028 | count_vm_events(PGACTIVATE, pgactivate); |
1029 | *ret_nr_dirty += nr_dirty; |
1030 | *ret_nr_writeback += nr_writeback; |
1031 | return nr_reclaimed; |
1032 | } |
1033 | |
1034 | /* |
1035 | * Attempt to remove the specified page from its LRU. Only take this page |
1036 | * if it is of the appropriate PageActive status. Pages which are being |
1037 | * freed elsewhere are also ignored. |
1038 | * |
1039 | * page: page to consider |
1040 | * mode: one of the LRU isolation modes defined above |
1041 | * |
1042 | * returns 0 on success, -ve errno on failure. |
1043 | */ |
1044 | int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file) |
1045 | { |
1046 | bool all_lru_mode; |
1047 | int ret = -EINVAL; |
1048 | |
1049 | /* Only take pages on the LRU. */ |
1050 | if (!PageLRU(page)) |
1051 | return ret; |
1052 | |
1053 | all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) == |
1054 | (ISOLATE_ACTIVE|ISOLATE_INACTIVE); |
1055 | |
1056 | /* |
1057 | * When checking the active state, we need to be sure we are |
1058 | * dealing with comparible boolean values. Take the logical not |
1059 | * of each. |
1060 | */ |
1061 | if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE)) |
1062 | return ret; |
1063 | |
1064 | if (!all_lru_mode && !!page_is_file_cache(page) != file) |
1065 | return ret; |
1066 | |
1067 | /* |
1068 | * When this function is being called for lumpy reclaim, we |
1069 | * initially look into all LRU pages, active, inactive and |
1070 | * unevictable; only give shrink_page_list evictable pages. |
1071 | */ |
1072 | if (PageUnevictable(page)) |
1073 | return ret; |
1074 | |
1075 | ret = -EBUSY; |
1076 | |
1077 | /* |
1078 | * To minimise LRU disruption, the caller can indicate that it only |
1079 | * wants to isolate pages it will be able to operate on without |
1080 | * blocking - clean pages for the most part. |
1081 | * |
1082 | * ISOLATE_CLEAN means that only clean pages should be isolated. This |
1083 | * is used by reclaim when it is cannot write to backing storage |
1084 | * |
1085 | * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages |
1086 | * that it is possible to migrate without blocking |
1087 | */ |
1088 | if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) { |
1089 | /* All the caller can do on PageWriteback is block */ |
1090 | if (PageWriteback(page)) |
1091 | return ret; |
1092 | |
1093 | if (PageDirty(page)) { |
1094 | struct address_space *mapping; |
1095 | |
1096 | /* ISOLATE_CLEAN means only clean pages */ |
1097 | if (mode & ISOLATE_CLEAN) |
1098 | return ret; |
1099 | |
1100 | /* |
1101 | * Only pages without mappings or that have a |
1102 | * ->migratepage callback are possible to migrate |
1103 | * without blocking |
1104 | */ |
1105 | mapping = page_mapping(page); |
1106 | if (mapping && !mapping->a_ops->migratepage) |
1107 | return ret; |
1108 | } |
1109 | } |
1110 | |
1111 | if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) |
1112 | return ret; |
1113 | |
1114 | if (likely(get_page_unless_zero(page))) { |
1115 | /* |
1116 | * Be careful not to clear PageLRU until after we're |
1117 | * sure the page is not being freed elsewhere -- the |
1118 | * page release code relies on it. |
1119 | */ |
1120 | ClearPageLRU(page); |
1121 | ret = 0; |
1122 | } |
1123 | |
1124 | return ret; |
1125 | } |
1126 | |
1127 | /* |
1128 | * zone->lru_lock is heavily contended. Some of the functions that |
1129 | * shrink the lists perform better by taking out a batch of pages |
1130 | * and working on them outside the LRU lock. |
1131 | * |
1132 | * For pagecache intensive workloads, this function is the hottest |
1133 | * spot in the kernel (apart from copy_*_user functions). |
1134 | * |
1135 | * Appropriate locks must be held before calling this function. |
1136 | * |
1137 | * @nr_to_scan: The number of pages to look through on the list. |
1138 | * @mz: The mem_cgroup_zone to pull pages from. |
1139 | * @dst: The temp list to put pages on to. |
1140 | * @nr_scanned: The number of pages that were scanned. |
1141 | * @order: The caller's attempted allocation order |
1142 | * @mode: One of the LRU isolation modes |
1143 | * @active: True [1] if isolating active pages |
1144 | * @file: True [1] if isolating file [!anon] pages |
1145 | * |
1146 | * returns how many pages were moved onto *@dst. |
1147 | */ |
1148 | static unsigned long isolate_lru_pages(unsigned long nr_to_scan, |
1149 | struct mem_cgroup_zone *mz, struct list_head *dst, |
1150 | unsigned long *nr_scanned, int order, isolate_mode_t mode, |
1151 | int active, int file) |
1152 | { |
1153 | struct lruvec *lruvec; |
1154 | struct list_head *src; |
1155 | unsigned long nr_taken = 0; |
1156 | unsigned long nr_lumpy_taken = 0; |
1157 | unsigned long nr_lumpy_dirty = 0; |
1158 | unsigned long nr_lumpy_failed = 0; |
1159 | unsigned long scan; |
1160 | int lru = LRU_BASE; |
1161 | |
1162 | lruvec = mem_cgroup_zone_lruvec(mz->zone, mz->mem_cgroup); |
1163 | if (active) |
1164 | lru += LRU_ACTIVE; |
1165 | if (file) |
1166 | lru += LRU_FILE; |
1167 | src = &lruvec->lists[lru]; |
1168 | |
1169 | for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { |
1170 | struct page *page; |
1171 | unsigned long pfn; |
1172 | unsigned long end_pfn; |
1173 | unsigned long page_pfn; |
1174 | int zone_id; |
1175 | |
1176 | page = lru_to_page(src); |
1177 | prefetchw_prev_lru_page(page, src, flags); |
1178 | |
1179 | VM_BUG_ON(!PageLRU(page)); |
1180 | |
1181 | switch (__isolate_lru_page(page, mode, file)) { |
1182 | case 0: |
1183 | mem_cgroup_lru_del(page); |
1184 | list_move(&page->lru, dst); |
1185 | nr_taken += hpage_nr_pages(page); |
1186 | break; |
1187 | |
1188 | case -EBUSY: |
1189 | /* else it is being freed elsewhere */ |
1190 | list_move(&page->lru, src); |
1191 | continue; |
1192 | |
1193 | default: |
1194 | BUG(); |
1195 | } |
1196 | |
1197 | if (!order) |
1198 | continue; |
1199 | |
1200 | /* |
1201 | * Attempt to take all pages in the order aligned region |
1202 | * surrounding the tag page. Only take those pages of |
1203 | * the same active state as that tag page. We may safely |
1204 | * round the target page pfn down to the requested order |
1205 | * as the mem_map is guaranteed valid out to MAX_ORDER, |
1206 | * where that page is in a different zone we will detect |
1207 | * it from its zone id and abort this block scan. |
1208 | */ |
1209 | zone_id = page_zone_id(page); |
1210 | page_pfn = page_to_pfn(page); |
1211 | pfn = page_pfn & ~((1 << order) - 1); |
1212 | end_pfn = pfn + (1 << order); |
1213 | for (; pfn < end_pfn; pfn++) { |
1214 | struct page *cursor_page; |
1215 | |
1216 | /* The target page is in the block, ignore it. */ |
1217 | if (unlikely(pfn == page_pfn)) |
1218 | continue; |
1219 | |
1220 | /* Avoid holes within the zone. */ |
1221 | if (unlikely(!pfn_valid_within(pfn))) |
1222 | break; |
1223 | |
1224 | cursor_page = pfn_to_page(pfn); |
1225 | |
1226 | /* Check that we have not crossed a zone boundary. */ |
1227 | if (unlikely(page_zone_id(cursor_page) != zone_id)) |
1228 | break; |
1229 | |
1230 | /* |
1231 | * If we don't have enough swap space, reclaiming of |
1232 | * anon page which don't already have a swap slot is |
1233 | * pointless. |
1234 | */ |
1235 | if (nr_swap_pages <= 0 && PageSwapBacked(cursor_page) && |
1236 | !PageSwapCache(cursor_page)) |
1237 | break; |
1238 | |
1239 | if (__isolate_lru_page(cursor_page, mode, file) == 0) { |
1240 | unsigned int isolated_pages; |
1241 | |
1242 | mem_cgroup_lru_del(cursor_page); |
1243 | list_move(&cursor_page->lru, dst); |
1244 | isolated_pages = hpage_nr_pages(cursor_page); |
1245 | nr_taken += isolated_pages; |
1246 | nr_lumpy_taken += isolated_pages; |
1247 | if (PageDirty(cursor_page)) |
1248 | nr_lumpy_dirty += isolated_pages; |
1249 | scan++; |
1250 | pfn += isolated_pages - 1; |
1251 | } else { |
1252 | /* |
1253 | * Check if the page is freed already. |
1254 | * |
1255 | * We can't use page_count() as that |
1256 | * requires compound_head and we don't |
1257 | * have a pin on the page here. If a |
1258 | * page is tail, we may or may not |
1259 | * have isolated the head, so assume |
1260 | * it's not free, it'd be tricky to |
1261 | * track the head status without a |
1262 | * page pin. |
1263 | */ |
1264 | if (!PageTail(cursor_page) && |
1265 | !atomic_read(&cursor_page->_count)) |
1266 | continue; |
1267 | break; |
1268 | } |
1269 | } |
1270 | |
1271 | /* If we break out of the loop above, lumpy reclaim failed */ |
1272 | if (pfn < end_pfn) |
1273 | nr_lumpy_failed++; |
1274 | } |
1275 | |
1276 | *nr_scanned = scan; |
1277 | |
1278 | trace_mm_vmscan_lru_isolate(order, |
1279 | nr_to_scan, scan, |
1280 | nr_taken, |
1281 | nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, |
1282 | mode, file); |
1283 | return nr_taken; |
1284 | } |
1285 | |
1286 | /** |
1287 | * isolate_lru_page - tries to isolate a page from its LRU list |
1288 | * @page: page to isolate from its LRU list |
1289 | * |
1290 | * Isolates a @page from an LRU list, clears PageLRU and adjusts the |
1291 | * vmstat statistic corresponding to whatever LRU list the page was on. |
1292 | * |
1293 | * Returns 0 if the page was removed from an LRU list. |
1294 | * Returns -EBUSY if the page was not on an LRU list. |
1295 | * |
1296 | * The returned page will have PageLRU() cleared. If it was found on |
1297 | * the active list, it will have PageActive set. If it was found on |
1298 | * the unevictable list, it will have the PageUnevictable bit set. That flag |
1299 | * may need to be cleared by the caller before letting the page go. |
1300 | * |
1301 | * The vmstat statistic corresponding to the list on which the page was |
1302 | * found will be decremented. |
1303 | * |
1304 | * Restrictions: |
1305 | * (1) Must be called with an elevated refcount on the page. This is a |
1306 | * fundamentnal difference from isolate_lru_pages (which is called |
1307 | * without a stable reference). |
1308 | * (2) the lru_lock must not be held. |
1309 | * (3) interrupts must be enabled. |
1310 | */ |
1311 | int isolate_lru_page(struct page *page) |
1312 | { |
1313 | int ret = -EBUSY; |
1314 | |
1315 | VM_BUG_ON(!page_count(page)); |
1316 | |
1317 | if (PageLRU(page)) { |
1318 | struct zone *zone = page_zone(page); |
1319 | |
1320 | spin_lock_irq(&zone->lru_lock); |
1321 | if (PageLRU(page)) { |
1322 | int lru = page_lru(page); |
1323 | ret = 0; |
1324 | get_page(page); |
1325 | ClearPageLRU(page); |
1326 | |
1327 | del_page_from_lru_list(zone, page, lru); |
1328 | } |
1329 | spin_unlock_irq(&zone->lru_lock); |
1330 | } |
1331 | return ret; |
1332 | } |
1333 | |
1334 | /* |
1335 | * Are there way too many processes in the direct reclaim path already? |
1336 | */ |
1337 | static int too_many_isolated(struct zone *zone, int file, |
1338 | struct scan_control *sc) |
1339 | { |
1340 | unsigned long inactive, isolated; |
1341 | |
1342 | if (current_is_kswapd()) |
1343 | return 0; |
1344 | |
1345 | if (!global_reclaim(sc)) |
1346 | return 0; |
1347 | |
1348 | if (file) { |
1349 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); |
1350 | isolated = zone_page_state(zone, NR_ISOLATED_FILE); |
1351 | } else { |
1352 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
1353 | isolated = zone_page_state(zone, NR_ISOLATED_ANON); |
1354 | } |
1355 | |
1356 | return isolated > inactive; |
1357 | } |
1358 | |
1359 | static noinline_for_stack void |
1360 | putback_inactive_pages(struct mem_cgroup_zone *mz, |
1361 | struct list_head *page_list) |
1362 | { |
1363 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz); |
1364 | struct zone *zone = mz->zone; |
1365 | LIST_HEAD(pages_to_free); |
1366 | |
1367 | /* |
1368 | * Put back any unfreeable pages. |
1369 | */ |
1370 | while (!list_empty(page_list)) { |
1371 | struct page *page = lru_to_page(page_list); |
1372 | int lru; |
1373 | |
1374 | VM_BUG_ON(PageLRU(page)); |
1375 | list_del(&page->lru); |
1376 | if (unlikely(!page_evictable(page, NULL))) { |
1377 | spin_unlock_irq(&zone->lru_lock); |
1378 | putback_lru_page(page); |
1379 | spin_lock_irq(&zone->lru_lock); |
1380 | continue; |
1381 | } |
1382 | SetPageLRU(page); |
1383 | lru = page_lru(page); |
1384 | add_page_to_lru_list(zone, page, lru); |
1385 | if (is_active_lru(lru)) { |
1386 | int file = is_file_lru(lru); |
1387 | int numpages = hpage_nr_pages(page); |
1388 | reclaim_stat->recent_rotated[file] += numpages; |
1389 | } |
1390 | if (put_page_testzero(page)) { |
1391 | __ClearPageLRU(page); |
1392 | __ClearPageActive(page); |
1393 | del_page_from_lru_list(zone, page, lru); |
1394 | |
1395 | if (unlikely(PageCompound(page))) { |
1396 | spin_unlock_irq(&zone->lru_lock); |
1397 | (*get_compound_page_dtor(page))(page); |
1398 | spin_lock_irq(&zone->lru_lock); |
1399 | } else |
1400 | list_add(&page->lru, &pages_to_free); |
1401 | } |
1402 | } |
1403 | |
1404 | /* |
1405 | * To save our caller's stack, now use input list for pages to free. |
1406 | */ |
1407 | list_splice(&pages_to_free, page_list); |
1408 | } |
1409 | |
1410 | static noinline_for_stack void |
1411 | update_isolated_counts(struct mem_cgroup_zone *mz, |
1412 | struct list_head *page_list, |
1413 | unsigned long *nr_anon, |
1414 | unsigned long *nr_file) |
1415 | { |
1416 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz); |
1417 | struct zone *zone = mz->zone; |
1418 | unsigned int count[NR_LRU_LISTS] = { 0, }; |
1419 | unsigned long nr_active = 0; |
1420 | struct page *page; |
1421 | int lru; |
1422 | |
1423 | /* |
1424 | * Count pages and clear active flags |
1425 | */ |
1426 | list_for_each_entry(page, page_list, lru) { |
1427 | int numpages = hpage_nr_pages(page); |
1428 | lru = page_lru_base_type(page); |
1429 | if (PageActive(page)) { |
1430 | lru += LRU_ACTIVE; |
1431 | ClearPageActive(page); |
1432 | nr_active += numpages; |
1433 | } |
1434 | count[lru] += numpages; |
1435 | } |
1436 | |
1437 | __count_vm_events(PGDEACTIVATE, nr_active); |
1438 | |
1439 | __mod_zone_page_state(zone, NR_ACTIVE_FILE, |
1440 | -count[LRU_ACTIVE_FILE]); |
1441 | __mod_zone_page_state(zone, NR_INACTIVE_FILE, |
1442 | -count[LRU_INACTIVE_FILE]); |
1443 | __mod_zone_page_state(zone, NR_ACTIVE_ANON, |
1444 | -count[LRU_ACTIVE_ANON]); |
1445 | __mod_zone_page_state(zone, NR_INACTIVE_ANON, |
1446 | -count[LRU_INACTIVE_ANON]); |
1447 | |
1448 | *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; |
1449 | *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; |
1450 | |
1451 | reclaim_stat->recent_scanned[0] += *nr_anon; |
1452 | reclaim_stat->recent_scanned[1] += *nr_file; |
1453 | } |
1454 | |
1455 | /* |
1456 | * Returns true if a direct reclaim should wait on pages under writeback. |
1457 | * |
1458 | * If we are direct reclaiming for contiguous pages and we do not reclaim |
1459 | * everything in the list, try again and wait for writeback IO to complete. |
1460 | * This will stall high-order allocations noticeably. Only do that when really |
1461 | * need to free the pages under high memory pressure. |
1462 | */ |
1463 | static inline bool should_reclaim_stall(unsigned long nr_taken, |
1464 | unsigned long nr_freed, |
1465 | int priority, |
1466 | struct scan_control *sc) |
1467 | { |
1468 | int lumpy_stall_priority; |
1469 | |
1470 | /* kswapd should not stall on sync IO */ |
1471 | if (current_is_kswapd()) |
1472 | return false; |
1473 | |
1474 | /* Only stall on lumpy reclaim */ |
1475 | if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) |
1476 | return false; |
1477 | |
1478 | /* If we have reclaimed everything on the isolated list, no stall */ |
1479 | if (nr_freed == nr_taken) |
1480 | return false; |
1481 | |
1482 | /* |
1483 | * For high-order allocations, there are two stall thresholds. |
1484 | * High-cost allocations stall immediately where as lower |
1485 | * order allocations such as stacks require the scanning |
1486 | * priority to be much higher before stalling. |
1487 | */ |
1488 | if (sc->order > PAGE_ALLOC_COSTLY_ORDER) |
1489 | lumpy_stall_priority = DEF_PRIORITY; |
1490 | else |
1491 | lumpy_stall_priority = DEF_PRIORITY / 3; |
1492 | |
1493 | return priority <= lumpy_stall_priority; |
1494 | } |
1495 | |
1496 | /* |
1497 | * shrink_inactive_list() is a helper for shrink_zone(). It returns the number |
1498 | * of reclaimed pages |
1499 | */ |
1500 | static noinline_for_stack unsigned long |
1501 | shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz, |
1502 | struct scan_control *sc, int priority, int file) |
1503 | { |
1504 | LIST_HEAD(page_list); |
1505 | unsigned long nr_scanned; |
1506 | unsigned long nr_reclaimed = 0; |
1507 | unsigned long nr_taken; |
1508 | unsigned long nr_anon; |
1509 | unsigned long nr_file; |
1510 | unsigned long nr_dirty = 0; |
1511 | unsigned long nr_writeback = 0; |
1512 | isolate_mode_t reclaim_mode = ISOLATE_INACTIVE; |
1513 | struct zone *zone = mz->zone; |
1514 | |
1515 | while (unlikely(too_many_isolated(zone, file, sc))) { |
1516 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
1517 | |
1518 | /* We are about to die and free our memory. Return now. */ |
1519 | if (fatal_signal_pending(current)) |
1520 | return SWAP_CLUSTER_MAX; |
1521 | } |
1522 | |
1523 | set_reclaim_mode(priority, sc, false); |
1524 | if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) |
1525 | reclaim_mode |= ISOLATE_ACTIVE; |
1526 | |
1527 | lru_add_drain(); |
1528 | |
1529 | if (!sc->may_unmap) |
1530 | reclaim_mode |= ISOLATE_UNMAPPED; |
1531 | if (!sc->may_writepage) |
1532 | reclaim_mode |= ISOLATE_CLEAN; |
1533 | |
1534 | spin_lock_irq(&zone->lru_lock); |
1535 | |
1536 | nr_taken = isolate_lru_pages(nr_to_scan, mz, &page_list, |
1537 | &nr_scanned, sc->order, |
1538 | reclaim_mode, 0, file); |
1539 | if (global_reclaim(sc)) { |
1540 | zone->pages_scanned += nr_scanned; |
1541 | if (current_is_kswapd()) |
1542 | __count_zone_vm_events(PGSCAN_KSWAPD, zone, |
1543 | nr_scanned); |
1544 | else |
1545 | __count_zone_vm_events(PGSCAN_DIRECT, zone, |
1546 | nr_scanned); |
1547 | } |
1548 | |
1549 | if (nr_taken == 0) { |
1550 | spin_unlock_irq(&zone->lru_lock); |
1551 | return 0; |
1552 | } |
1553 | |
1554 | update_isolated_counts(mz, &page_list, &nr_anon, &nr_file); |
1555 | |
1556 | __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon); |
1557 | __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file); |
1558 | |
1559 | spin_unlock_irq(&zone->lru_lock); |
1560 | |
1561 | nr_reclaimed = shrink_page_list(&page_list, mz, sc, priority, |
1562 | &nr_dirty, &nr_writeback); |
1563 | |
1564 | /* Check if we should syncronously wait for writeback */ |
1565 | if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { |
1566 | set_reclaim_mode(priority, sc, true); |
1567 | nr_reclaimed += shrink_page_list(&page_list, mz, sc, |
1568 | priority, &nr_dirty, &nr_writeback); |
1569 | } |
1570 | |
1571 | spin_lock_irq(&zone->lru_lock); |
1572 | |
1573 | if (current_is_kswapd()) |
1574 | __count_vm_events(KSWAPD_STEAL, nr_reclaimed); |
1575 | __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); |
1576 | |
1577 | putback_inactive_pages(mz, &page_list); |
1578 | |
1579 | __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); |
1580 | __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); |
1581 | |
1582 | spin_unlock_irq(&zone->lru_lock); |
1583 | |
1584 | free_hot_cold_page_list(&page_list, 1); |
1585 | |
1586 | /* |
1587 | * If reclaim is isolating dirty pages under writeback, it implies |
1588 | * that the long-lived page allocation rate is exceeding the page |
1589 | * laundering rate. Either the global limits are not being effective |
1590 | * at throttling processes due to the page distribution throughout |
1591 | * zones or there is heavy usage of a slow backing device. The |
1592 | * only option is to throttle from reclaim context which is not ideal |
1593 | * as there is no guarantee the dirtying process is throttled in the |
1594 | * same way balance_dirty_pages() manages. |
1595 | * |
1596 | * This scales the number of dirty pages that must be under writeback |
1597 | * before throttling depending on priority. It is a simple backoff |
1598 | * function that has the most effect in the range DEF_PRIORITY to |
1599 | * DEF_PRIORITY-2 which is the priority reclaim is considered to be |
1600 | * in trouble and reclaim is considered to be in trouble. |
1601 | * |
1602 | * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle |
1603 | * DEF_PRIORITY-1 50% must be PageWriteback |
1604 | * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble |
1605 | * ... |
1606 | * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any |
1607 | * isolated page is PageWriteback |
1608 | */ |
1609 | if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority))) |
1610 | wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10); |
1611 | |
1612 | trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, |
1613 | zone_idx(zone), |
1614 | nr_scanned, nr_reclaimed, |
1615 | priority, |
1616 | trace_shrink_flags(file, sc->reclaim_mode)); |
1617 | return nr_reclaimed; |
1618 | } |
1619 | |
1620 | /* |
1621 | * This moves pages from the active list to the inactive list. |
1622 | * |
1623 | * We move them the other way if the page is referenced by one or more |
1624 | * processes, from rmap. |
1625 | * |
1626 | * If the pages are mostly unmapped, the processing is fast and it is |
1627 | * appropriate to hold zone->lru_lock across the whole operation. But if |
1628 | * the pages are mapped, the processing is slow (page_referenced()) so we |
1629 | * should drop zone->lru_lock around each page. It's impossible to balance |
1630 | * this, so instead we remove the pages from the LRU while processing them. |
1631 | * It is safe to rely on PG_active against the non-LRU pages in here because |
1632 | * nobody will play with that bit on a non-LRU page. |
1633 | * |
1634 | * The downside is that we have to touch page->_count against each page. |
1635 | * But we had to alter page->flags anyway. |
1636 | */ |
1637 | |
1638 | static void move_active_pages_to_lru(struct zone *zone, |
1639 | struct list_head *list, |
1640 | struct list_head *pages_to_free, |
1641 | enum lru_list lru) |
1642 | { |
1643 | unsigned long pgmoved = 0; |
1644 | struct page *page; |
1645 | |
1646 | if (buffer_heads_over_limit) { |
1647 | spin_unlock_irq(&zone->lru_lock); |
1648 | list_for_each_entry(page, list, lru) { |
1649 | if (page_has_private(page) && trylock_page(page)) { |
1650 | if (page_has_private(page)) |
1651 | try_to_release_page(page, 0); |
1652 | unlock_page(page); |
1653 | } |
1654 | } |
1655 | spin_lock_irq(&zone->lru_lock); |
1656 | } |
1657 | |
1658 | while (!list_empty(list)) { |
1659 | struct lruvec *lruvec; |
1660 | |
1661 | page = lru_to_page(list); |
1662 | |
1663 | VM_BUG_ON(PageLRU(page)); |
1664 | SetPageLRU(page); |
1665 | |
1666 | lruvec = mem_cgroup_lru_add_list(zone, page, lru); |
1667 | list_move(&page->lru, &lruvec->lists[lru]); |
1668 | pgmoved += hpage_nr_pages(page); |
1669 | |
1670 | if (put_page_testzero(page)) { |
1671 | __ClearPageLRU(page); |
1672 | __ClearPageActive(page); |
1673 | del_page_from_lru_list(zone, page, lru); |
1674 | |
1675 | if (unlikely(PageCompound(page))) { |
1676 | spin_unlock_irq(&zone->lru_lock); |
1677 | (*get_compound_page_dtor(page))(page); |
1678 | spin_lock_irq(&zone->lru_lock); |
1679 | } else |
1680 | list_add(&page->lru, pages_to_free); |
1681 | } |
1682 | } |
1683 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); |
1684 | if (!is_active_lru(lru)) |
1685 | __count_vm_events(PGDEACTIVATE, pgmoved); |
1686 | } |
1687 | |
1688 | static void shrink_active_list(unsigned long nr_to_scan, |
1689 | struct mem_cgroup_zone *mz, |
1690 | struct scan_control *sc, |
1691 | int priority, int file) |
1692 | { |
1693 | unsigned long nr_taken; |
1694 | unsigned long nr_scanned; |
1695 | unsigned long vm_flags; |
1696 | LIST_HEAD(l_hold); /* The pages which were snipped off */ |
1697 | LIST_HEAD(l_active); |
1698 | LIST_HEAD(l_inactive); |
1699 | struct page *page; |
1700 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz); |
1701 | unsigned long nr_rotated = 0; |
1702 | isolate_mode_t reclaim_mode = ISOLATE_ACTIVE; |
1703 | struct zone *zone = mz->zone; |
1704 | |
1705 | lru_add_drain(); |
1706 | |
1707 | if (!sc->may_unmap) |
1708 | reclaim_mode |= ISOLATE_UNMAPPED; |
1709 | if (!sc->may_writepage) |
1710 | reclaim_mode |= ISOLATE_CLEAN; |
1711 | |
1712 | spin_lock_irq(&zone->lru_lock); |
1713 | |
1714 | nr_taken = isolate_lru_pages(nr_to_scan, mz, &l_hold, |
1715 | &nr_scanned, sc->order, |
1716 | reclaim_mode, 1, file); |
1717 | if (global_reclaim(sc)) |
1718 | zone->pages_scanned += nr_scanned; |
1719 | |
1720 | reclaim_stat->recent_scanned[file] += nr_taken; |
1721 | |
1722 | __count_zone_vm_events(PGREFILL, zone, nr_scanned); |
1723 | if (file) |
1724 | __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); |
1725 | else |
1726 | __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); |
1727 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); |
1728 | spin_unlock_irq(&zone->lru_lock); |
1729 | |
1730 | while (!list_empty(&l_hold)) { |
1731 | cond_resched(); |
1732 | page = lru_to_page(&l_hold); |
1733 | list_del(&page->lru); |
1734 | |
1735 | if (unlikely(!page_evictable(page, NULL))) { |
1736 | putback_lru_page(page); |
1737 | continue; |
1738 | } |
1739 | |
1740 | if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) { |
1741 | nr_rotated += hpage_nr_pages(page); |
1742 | /* |
1743 | * Identify referenced, file-backed active pages and |
1744 | * give them one more trip around the active list. So |
1745 | * that executable code get better chances to stay in |
1746 | * memory under moderate memory pressure. Anon pages |
1747 | * are not likely to be evicted by use-once streaming |
1748 | * IO, plus JVM can create lots of anon VM_EXEC pages, |
1749 | * so we ignore them here. |
1750 | */ |
1751 | if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { |
1752 | list_add(&page->lru, &l_active); |
1753 | continue; |
1754 | } |
1755 | } |
1756 | |
1757 | ClearPageActive(page); /* we are de-activating */ |
1758 | list_add(&page->lru, &l_inactive); |
1759 | } |
1760 | |
1761 | /* |
1762 | * Move pages back to the lru list. |
1763 | */ |
1764 | spin_lock_irq(&zone->lru_lock); |
1765 | /* |
1766 | * Count referenced pages from currently used mappings as rotated, |
1767 | * even though only some of them are actually re-activated. This |
1768 | * helps balance scan pressure between file and anonymous pages in |
1769 | * get_scan_ratio. |
1770 | */ |
1771 | reclaim_stat->recent_rotated[file] += nr_rotated; |
1772 | |
1773 | move_active_pages_to_lru(zone, &l_active, &l_hold, |
1774 | LRU_ACTIVE + file * LRU_FILE); |
1775 | move_active_pages_to_lru(zone, &l_inactive, &l_hold, |
1776 | LRU_BASE + file * LRU_FILE); |
1777 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); |
1778 | spin_unlock_irq(&zone->lru_lock); |
1779 | |
1780 | free_hot_cold_page_list(&l_hold, 1); |
1781 | } |
1782 | |
1783 | #ifdef CONFIG_SWAP |
1784 | static int inactive_anon_is_low_global(struct zone *zone) |
1785 | { |
1786 | unsigned long active, inactive; |
1787 | |
1788 | active = zone_page_state(zone, NR_ACTIVE_ANON); |
1789 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
1790 | |
1791 | if (inactive * zone->inactive_ratio < active) |
1792 | return 1; |
1793 | |
1794 | return 0; |
1795 | } |
1796 | |
1797 | /** |
1798 | * inactive_anon_is_low - check if anonymous pages need to be deactivated |
1799 | * @zone: zone to check |
1800 | * @sc: scan control of this context |
1801 | * |
1802 | * Returns true if the zone does not have enough inactive anon pages, |
1803 | * meaning some active anon pages need to be deactivated. |
1804 | */ |
1805 | static int inactive_anon_is_low(struct mem_cgroup_zone *mz) |
1806 | { |
1807 | /* |
1808 | * If we don't have swap space, anonymous page deactivation |
1809 | * is pointless. |
1810 | */ |
1811 | if (!total_swap_pages) |
1812 | return 0; |
1813 | |
1814 | if (!scanning_global_lru(mz)) |
1815 | return mem_cgroup_inactive_anon_is_low(mz->mem_cgroup, |
1816 | mz->zone); |
1817 | |
1818 | return inactive_anon_is_low_global(mz->zone); |
1819 | } |
1820 | #else |
1821 | static inline int inactive_anon_is_low(struct mem_cgroup_zone *mz) |
1822 | { |
1823 | return 0; |
1824 | } |
1825 | #endif |
1826 | |
1827 | static int inactive_file_is_low_global(struct zone *zone) |
1828 | { |
1829 | unsigned long active, inactive; |
1830 | |
1831 | active = zone_page_state(zone, NR_ACTIVE_FILE); |
1832 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); |
1833 | |
1834 | return (active > inactive); |
1835 | } |
1836 | |
1837 | /** |
1838 | * inactive_file_is_low - check if file pages need to be deactivated |
1839 | * @mz: memory cgroup and zone to check |
1840 | * |
1841 | * When the system is doing streaming IO, memory pressure here |
1842 | * ensures that active file pages get deactivated, until more |
1843 | * than half of the file pages are on the inactive list. |
1844 | * |
1845 | * Once we get to that situation, protect the system's working |
1846 | * set from being evicted by disabling active file page aging. |
1847 | * |
1848 | * This uses a different ratio than the anonymous pages, because |
1849 | * the page cache uses a use-once replacement algorithm. |
1850 | */ |
1851 | static int inactive_file_is_low(struct mem_cgroup_zone *mz) |
1852 | { |
1853 | if (!scanning_global_lru(mz)) |
1854 | return mem_cgroup_inactive_file_is_low(mz->mem_cgroup, |
1855 | mz->zone); |
1856 | |
1857 | return inactive_file_is_low_global(mz->zone); |
1858 | } |
1859 | |
1860 | static int inactive_list_is_low(struct mem_cgroup_zone *mz, int file) |
1861 | { |
1862 | if (file) |
1863 | return inactive_file_is_low(mz); |
1864 | else |
1865 | return inactive_anon_is_low(mz); |
1866 | } |
1867 | |
1868 | static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, |
1869 | struct mem_cgroup_zone *mz, |
1870 | struct scan_control *sc, int priority) |
1871 | { |
1872 | int file = is_file_lru(lru); |
1873 | |
1874 | if (is_active_lru(lru)) { |
1875 | if (inactive_list_is_low(mz, file)) |
1876 | shrink_active_list(nr_to_scan, mz, sc, priority, file); |
1877 | return 0; |
1878 | } |
1879 | |
1880 | return shrink_inactive_list(nr_to_scan, mz, sc, priority, file); |
1881 | } |
1882 | |
1883 | static int vmscan_swappiness(struct mem_cgroup_zone *mz, |
1884 | struct scan_control *sc) |
1885 | { |
1886 | if (global_reclaim(sc)) |
1887 | return vm_swappiness; |
1888 | return mem_cgroup_swappiness(mz->mem_cgroup); |
1889 | } |
1890 | |
1891 | /* |
1892 | * Determine how aggressively the anon and file LRU lists should be |
1893 | * scanned. The relative value of each set of LRU lists is determined |
1894 | * by looking at the fraction of the pages scanned we did rotate back |
1895 | * onto the active list instead of evict. |
1896 | * |
1897 | * nr[0] = anon pages to scan; nr[1] = file pages to scan |
1898 | */ |
1899 | static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc, |
1900 | unsigned long *nr, int priority) |
1901 | { |
1902 | unsigned long anon, file, free; |
1903 | unsigned long anon_prio, file_prio; |
1904 | unsigned long ap, fp; |
1905 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz); |
1906 | u64 fraction[2], denominator; |
1907 | enum lru_list lru; |
1908 | int noswap = 0; |
1909 | bool force_scan = false; |
1910 | |
1911 | /* |
1912 | * If the zone or memcg is small, nr[l] can be 0. This |
1913 | * results in no scanning on this priority and a potential |
1914 | * priority drop. Global direct reclaim can go to the next |
1915 | * zone and tends to have no problems. Global kswapd is for |
1916 | * zone balancing and it needs to scan a minimum amount. When |
1917 | * reclaiming for a memcg, a priority drop can cause high |
1918 | * latencies, so it's better to scan a minimum amount there as |
1919 | * well. |
1920 | */ |
1921 | if (current_is_kswapd() && mz->zone->all_unreclaimable) |
1922 | force_scan = true; |
1923 | if (!global_reclaim(sc)) |
1924 | force_scan = true; |
1925 | |
1926 | /* If we have no swap space, do not bother scanning anon pages. */ |
1927 | if (!sc->may_swap || (nr_swap_pages <= 0)) { |
1928 | noswap = 1; |
1929 | fraction[0] = 0; |
1930 | fraction[1] = 1; |
1931 | denominator = 1; |
1932 | goto out; |
1933 | } |
1934 | |
1935 | anon = zone_nr_lru_pages(mz, LRU_ACTIVE_ANON) + |
1936 | zone_nr_lru_pages(mz, LRU_INACTIVE_ANON); |
1937 | file = zone_nr_lru_pages(mz, LRU_ACTIVE_FILE) + |
1938 | zone_nr_lru_pages(mz, LRU_INACTIVE_FILE); |
1939 | |
1940 | if (global_reclaim(sc)) { |
1941 | free = zone_page_state(mz->zone, NR_FREE_PAGES); |
1942 | /* If we have very few page cache pages, |
1943 | force-scan anon pages. */ |
1944 | if (unlikely(file + free <= high_wmark_pages(mz->zone))) { |
1945 | fraction[0] = 1; |
1946 | fraction[1] = 0; |
1947 | denominator = 1; |
1948 | goto out; |
1949 | } |
1950 | } |
1951 | |
1952 | /* |
1953 | * With swappiness at 100, anonymous and file have the same priority. |
1954 | * This scanning priority is essentially the inverse of IO cost. |
1955 | */ |
1956 | anon_prio = vmscan_swappiness(mz, sc); |
1957 | file_prio = 200 - vmscan_swappiness(mz, sc); |
1958 | |
1959 | /* |
1960 | * OK, so we have swap space and a fair amount of page cache |
1961 | * pages. We use the recently rotated / recently scanned |
1962 | * ratios to determine how valuable each cache is. |
1963 | * |
1964 | * Because workloads change over time (and to avoid overflow) |
1965 | * we keep these statistics as a floating average, which ends |
1966 | * up weighing recent references more than old ones. |
1967 | * |
1968 | * anon in [0], file in [1] |
1969 | */ |
1970 | spin_lock_irq(&mz->zone->lru_lock); |
1971 | if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { |
1972 | reclaim_stat->recent_scanned[0] /= 2; |
1973 | reclaim_stat->recent_rotated[0] /= 2; |
1974 | } |
1975 | |
1976 | if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { |
1977 | reclaim_stat->recent_scanned[1] /= 2; |
1978 | reclaim_stat->recent_rotated[1] /= 2; |
1979 | } |
1980 | |
1981 | /* |
1982 | * The amount of pressure on anon vs file pages is inversely |
1983 | * proportional to the fraction of recently scanned pages on |
1984 | * each list that were recently referenced and in active use. |
1985 | */ |
1986 | ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); |
1987 | ap /= reclaim_stat->recent_rotated[0] + 1; |
1988 | |
1989 | fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); |
1990 | fp /= reclaim_stat->recent_rotated[1] + 1; |
1991 | spin_unlock_irq(&mz->zone->lru_lock); |
1992 | |
1993 | fraction[0] = ap; |
1994 | fraction[1] = fp; |
1995 | denominator = ap + fp + 1; |
1996 | out: |
1997 | for_each_evictable_lru(lru) { |
1998 | int file = is_file_lru(lru); |
1999 | unsigned long scan; |
2000 | |
2001 | scan = zone_nr_lru_pages(mz, lru); |
2002 | if (priority || noswap) { |
2003 | scan >>= priority; |
2004 | if (!scan && force_scan) |
2005 | scan = SWAP_CLUSTER_MAX; |
2006 | scan = div64_u64(scan * fraction[file], denominator); |
2007 | } |
2008 | nr[lru] = scan; |
2009 | } |
2010 | } |
2011 | |
2012 | /* |
2013 | * Reclaim/compaction depends on a number of pages being freed. To avoid |
2014 | * disruption to the system, a small number of order-0 pages continue to be |
2015 | * rotated and reclaimed in the normal fashion. However, by the time we get |
2016 | * back to the allocator and call try_to_compact_zone(), we ensure that |
2017 | * there are enough free pages for it to be likely successful |
2018 | */ |
2019 | static inline bool should_continue_reclaim(struct mem_cgroup_zone *mz, |
2020 | unsigned long nr_reclaimed, |
2021 | unsigned long nr_scanned, |
2022 | struct scan_control *sc) |
2023 | { |
2024 | unsigned long pages_for_compaction; |
2025 | unsigned long inactive_lru_pages; |
2026 | |
2027 | /* If not in reclaim/compaction mode, stop */ |
2028 | if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) |
2029 | return false; |
2030 | |
2031 | /* Consider stopping depending on scan and reclaim activity */ |
2032 | if (sc->gfp_mask & __GFP_REPEAT) { |
2033 | /* |
2034 | * For __GFP_REPEAT allocations, stop reclaiming if the |
2035 | * full LRU list has been scanned and we are still failing |
2036 | * to reclaim pages. This full LRU scan is potentially |
2037 | * expensive but a __GFP_REPEAT caller really wants to succeed |
2038 | */ |
2039 | if (!nr_reclaimed && !nr_scanned) |
2040 | return false; |
2041 | } else { |
2042 | /* |
2043 | * For non-__GFP_REPEAT allocations which can presumably |
2044 | * fail without consequence, stop if we failed to reclaim |
2045 | * any pages from the last SWAP_CLUSTER_MAX number of |
2046 | * pages that were scanned. This will return to the |
2047 | * caller faster at the risk reclaim/compaction and |
2048 | * the resulting allocation attempt fails |
2049 | */ |
2050 | if (!nr_reclaimed) |
2051 | return false; |
2052 | } |
2053 | |
2054 | /* |
2055 | * If we have not reclaimed enough pages for compaction and the |
2056 | * inactive lists are large enough, continue reclaiming |
2057 | */ |
2058 | pages_for_compaction = (2UL << sc->order); |
2059 | inactive_lru_pages = zone_nr_lru_pages(mz, LRU_INACTIVE_FILE); |
2060 | if (nr_swap_pages > 0) |
2061 | inactive_lru_pages += zone_nr_lru_pages(mz, LRU_INACTIVE_ANON); |
2062 | if (sc->nr_reclaimed < pages_for_compaction && |
2063 | inactive_lru_pages > pages_for_compaction) |
2064 | return true; |
2065 | |
2066 | /* If compaction would go ahead or the allocation would succeed, stop */ |
2067 | switch (compaction_suitable(mz->zone, sc->order)) { |
2068 | case COMPACT_PARTIAL: |
2069 | case COMPACT_CONTINUE: |
2070 | return false; |
2071 | default: |
2072 | return true; |
2073 | } |
2074 | } |
2075 | |
2076 | /* |
2077 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. |
2078 | */ |
2079 | static void shrink_mem_cgroup_zone(int priority, struct mem_cgroup_zone *mz, |
2080 | struct scan_control *sc) |
2081 | { |
2082 | unsigned long nr[NR_LRU_LISTS]; |
2083 | unsigned long nr_to_scan; |
2084 | enum lru_list lru; |
2085 | unsigned long nr_reclaimed, nr_scanned; |
2086 | unsigned long nr_to_reclaim = sc->nr_to_reclaim; |
2087 | struct blk_plug plug; |
2088 | |
2089 | restart: |
2090 | nr_reclaimed = 0; |
2091 | nr_scanned = sc->nr_scanned; |
2092 | get_scan_count(mz, sc, nr, priority); |
2093 | |
2094 | blk_start_plug(&plug); |
2095 | while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || |
2096 | nr[LRU_INACTIVE_FILE]) { |
2097 | for_each_evictable_lru(lru) { |
2098 | if (nr[lru]) { |
2099 | nr_to_scan = min_t(unsigned long, |
2100 | nr[lru], SWAP_CLUSTER_MAX); |
2101 | nr[lru] -= nr_to_scan; |
2102 | |
2103 | nr_reclaimed += shrink_list(lru, nr_to_scan, |
2104 | mz, sc, priority); |
2105 | } |
2106 | } |
2107 | /* |
2108 | * On large memory systems, scan >> priority can become |
2109 | * really large. This is fine for the starting priority; |
2110 | * we want to put equal scanning pressure on each zone. |
2111 | * However, if the VM has a harder time of freeing pages, |
2112 | * with multiple processes reclaiming pages, the total |
2113 | * freeing target can get unreasonably large. |
2114 | */ |
2115 | if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) |
2116 | break; |
2117 | } |
2118 | blk_finish_plug(&plug); |
2119 | sc->nr_reclaimed += nr_reclaimed; |
2120 | |
2121 | /* |
2122 | * Even if we did not try to evict anon pages at all, we want to |
2123 | * rebalance the anon lru active/inactive ratio. |
2124 | */ |
2125 | if (inactive_anon_is_low(mz)) |
2126 | shrink_active_list(SWAP_CLUSTER_MAX, mz, sc, priority, 0); |
2127 | |
2128 | /* reclaim/compaction might need reclaim to continue */ |
2129 | if (should_continue_reclaim(mz, nr_reclaimed, |
2130 | sc->nr_scanned - nr_scanned, sc)) |
2131 | goto restart; |
2132 | |
2133 | throttle_vm_writeout(sc->gfp_mask); |
2134 | } |
2135 | |
2136 | static void shrink_zone(int priority, struct zone *zone, |
2137 | struct scan_control *sc) |
2138 | { |
2139 | struct mem_cgroup *root = sc->target_mem_cgroup; |
2140 | struct mem_cgroup_reclaim_cookie reclaim = { |
2141 | .zone = zone, |
2142 | .priority = priority, |
2143 | }; |
2144 | struct mem_cgroup *memcg; |
2145 | |
2146 | memcg = mem_cgroup_iter(root, NULL, &reclaim); |
2147 | do { |
2148 | struct mem_cgroup_zone mz = { |
2149 | .mem_cgroup = memcg, |
2150 | .zone = zone, |
2151 | }; |
2152 | |
2153 | shrink_mem_cgroup_zone(priority, &mz, sc); |
2154 | /* |
2155 | * Limit reclaim has historically picked one memcg and |
2156 | * scanned it with decreasing priority levels until |
2157 | * nr_to_reclaim had been reclaimed. This priority |
2158 | * cycle is thus over after a single memcg. |
2159 | * |
2160 | * Direct reclaim and kswapd, on the other hand, have |
2161 | * to scan all memory cgroups to fulfill the overall |
2162 | * scan target for the zone. |
2163 | */ |
2164 | if (!global_reclaim(sc)) { |
2165 | mem_cgroup_iter_break(root, memcg); |
2166 | break; |
2167 | } |
2168 | memcg = mem_cgroup_iter(root, memcg, &reclaim); |
2169 | } while (memcg); |
2170 | } |
2171 | |
2172 | /* Returns true if compaction should go ahead for a high-order request */ |
2173 | static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) |
2174 | { |
2175 | unsigned long balance_gap, watermark; |
2176 | bool watermark_ok; |
2177 | |
2178 | /* Do not consider compaction for orders reclaim is meant to satisfy */ |
2179 | if (sc->order <= PAGE_ALLOC_COSTLY_ORDER) |
2180 | return false; |
2181 | |
2182 | /* |
2183 | * Compaction takes time to run and there are potentially other |
2184 | * callers using the pages just freed. Continue reclaiming until |
2185 | * there is a buffer of free pages available to give compaction |
2186 | * a reasonable chance of completing and allocating the page |
2187 | */ |
2188 | balance_gap = min(low_wmark_pages(zone), |
2189 | (zone->present_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / |
2190 | KSWAPD_ZONE_BALANCE_GAP_RATIO); |
2191 | watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order); |
2192 | watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0); |
2193 | |
2194 | /* |
2195 | * If compaction is deferred, reclaim up to a point where |
2196 | * compaction will have a chance of success when re-enabled |
2197 | */ |
2198 | if (compaction_deferred(zone)) |
2199 | return watermark_ok; |
2200 | |
2201 | /* If compaction is not ready to start, keep reclaiming */ |
2202 | if (!compaction_suitable(zone, sc->order)) |
2203 | return false; |
2204 | |
2205 | return watermark_ok; |
2206 | } |
2207 | |
2208 | /* |
2209 | * This is the direct reclaim path, for page-allocating processes. We only |
2210 | * try to reclaim pages from zones which will satisfy the caller's allocation |
2211 | * request. |
2212 | * |
2213 | * We reclaim from a zone even if that zone is over high_wmark_pages(zone). |
2214 | * Because: |
2215 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order |
2216 | * allocation or |
2217 | * b) The target zone may be at high_wmark_pages(zone) but the lower zones |
2218 | * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' |
2219 | * zone defense algorithm. |
2220 | * |
2221 | * If a zone is deemed to be full of pinned pages then just give it a light |
2222 | * scan then give up on it. |
2223 | * |
2224 | * This function returns true if a zone is being reclaimed for a costly |
2225 | * high-order allocation and compaction is ready to begin. This indicates to |
2226 | * the caller that it should consider retrying the allocation instead of |
2227 | * further reclaim. |
2228 | */ |
2229 | static bool shrink_zones(int priority, struct zonelist *zonelist, |
2230 | struct scan_control *sc) |
2231 | { |
2232 | struct zoneref *z; |
2233 | struct zone *zone; |
2234 | unsigned long nr_soft_reclaimed; |
2235 | unsigned long nr_soft_scanned; |
2236 | bool aborted_reclaim = false; |
2237 | |
2238 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
2239 | gfp_zone(sc->gfp_mask), sc->nodemask) { |
2240 | if (!populated_zone(zone)) |
2241 | continue; |
2242 | /* |
2243 | * Take care memory controller reclaiming has small influence |
2244 | * to global LRU. |
2245 | */ |
2246 | if (global_reclaim(sc)) { |
2247 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2248 | continue; |
2249 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
2250 | continue; /* Let kswapd poll it */ |
2251 | if (COMPACTION_BUILD) { |
2252 | /* |
2253 | * If we already have plenty of memory free for |
2254 | * compaction in this zone, don't free any more. |
2255 | * Even though compaction is invoked for any |
2256 | * non-zero order, only frequent costly order |
2257 | * reclamation is disruptive enough to become a |
2258 | * noticable problem, like transparent huge page |
2259 | * allocations. |
2260 | */ |
2261 | if (compaction_ready(zone, sc)) { |
2262 | aborted_reclaim = true; |
2263 | continue; |
2264 | } |
2265 | } |
2266 | /* |
2267 | * This steals pages from memory cgroups over softlimit |
2268 | * and returns the number of reclaimed pages and |
2269 | * scanned pages. This works for global memory pressure |
2270 | * and balancing, not for a memcg's limit. |
2271 | */ |
2272 | nr_soft_scanned = 0; |
2273 | nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, |
2274 | sc->order, sc->gfp_mask, |
2275 | &nr_soft_scanned); |
2276 | sc->nr_reclaimed += nr_soft_reclaimed; |
2277 | sc->nr_scanned += nr_soft_scanned; |
2278 | /* need some check for avoid more shrink_zone() */ |
2279 | } |
2280 | |
2281 | shrink_zone(priority, zone, sc); |
2282 | } |
2283 | |
2284 | return aborted_reclaim; |
2285 | } |
2286 | |
2287 | static bool zone_reclaimable(struct zone *zone) |
2288 | { |
2289 | return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; |
2290 | } |
2291 | |
2292 | /* All zones in zonelist are unreclaimable? */ |
2293 | static bool all_unreclaimable(struct zonelist *zonelist, |
2294 | struct scan_control *sc) |
2295 | { |
2296 | struct zoneref *z; |
2297 | struct zone *zone; |
2298 | |
2299 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
2300 | gfp_zone(sc->gfp_mask), sc->nodemask) { |
2301 | if (!populated_zone(zone)) |
2302 | continue; |
2303 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2304 | continue; |
2305 | if (!zone->all_unreclaimable) |
2306 | return false; |
2307 | } |
2308 | |
2309 | return true; |
2310 | } |
2311 | |
2312 | /* |
2313 | * This is the main entry point to direct page reclaim. |
2314 | * |
2315 | * If a full scan of the inactive list fails to free enough memory then we |
2316 | * are "out of memory" and something needs to be killed. |
2317 | * |
2318 | * If the caller is !__GFP_FS then the probability of a failure is reasonably |
2319 | * high - the zone may be full of dirty or under-writeback pages, which this |
2320 | * caller can't do much about. We kick the writeback threads and take explicit |
2321 | * naps in the hope that some of these pages can be written. But if the |
2322 | * allocating task holds filesystem locks which prevent writeout this might not |
2323 | * work, and the allocation attempt will fail. |
2324 | * |
2325 | * returns: 0, if no pages reclaimed |
2326 | * else, the number of pages reclaimed |
2327 | */ |
2328 | static unsigned long do_try_to_free_pages(struct zonelist *zonelist, |
2329 | struct scan_control *sc, |
2330 | struct shrink_control *shrink) |
2331 | { |
2332 | int priority; |
2333 | unsigned long total_scanned = 0; |
2334 | struct reclaim_state *reclaim_state = current->reclaim_state; |
2335 | struct zoneref *z; |
2336 | struct zone *zone; |
2337 | unsigned long writeback_threshold; |
2338 | bool aborted_reclaim; |
2339 | |
2340 | get_mems_allowed(); |
2341 | delayacct_freepages_start(); |
2342 | |
2343 | if (global_reclaim(sc)) |
2344 | count_vm_event(ALLOCSTALL); |
2345 | |
2346 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
2347 | sc->nr_scanned = 0; |
2348 | if (!priority) |
2349 | disable_swap_token(sc->target_mem_cgroup); |
2350 | aborted_reclaim = shrink_zones(priority, zonelist, sc); |
2351 | |
2352 | /* |
2353 | * Don't shrink slabs when reclaiming memory from |
2354 | * over limit cgroups |
2355 | */ |
2356 | if (global_reclaim(sc)) { |
2357 | unsigned long lru_pages = 0; |
2358 | for_each_zone_zonelist(zone, z, zonelist, |
2359 | gfp_zone(sc->gfp_mask)) { |
2360 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2361 | continue; |
2362 | |
2363 | lru_pages += zone_reclaimable_pages(zone); |
2364 | } |
2365 | |
2366 | shrink_slab(shrink, sc->nr_scanned, lru_pages); |
2367 | if (reclaim_state) { |
2368 | sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
2369 | reclaim_state->reclaimed_slab = 0; |
2370 | } |
2371 | } |
2372 | total_scanned += sc->nr_scanned; |
2373 | if (sc->nr_reclaimed >= sc->nr_to_reclaim) |
2374 | goto out; |
2375 | |
2376 | /* |
2377 | * Try to write back as many pages as we just scanned. This |
2378 | * tends to cause slow streaming writers to write data to the |
2379 | * disk smoothly, at the dirtying rate, which is nice. But |
2380 | * that's undesirable in laptop mode, where we *want* lumpy |
2381 | * writeout. So in laptop mode, write out the whole world. |
2382 | */ |
2383 | writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; |
2384 | if (total_scanned > writeback_threshold) { |
2385 | wakeup_flusher_threads(laptop_mode ? 0 : total_scanned, |
2386 | WB_REASON_TRY_TO_FREE_PAGES); |
2387 | sc->may_writepage = 1; |
2388 | } |
2389 | |
2390 | /* Take a nap, wait for some writeback to complete */ |
2391 | if (!sc->hibernation_mode && sc->nr_scanned && |
2392 | priority < DEF_PRIORITY - 2) { |
2393 | struct zone *preferred_zone; |
2394 | |
2395 | first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), |
2396 | &cpuset_current_mems_allowed, |
2397 | &preferred_zone); |
2398 | wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); |
2399 | } |
2400 | } |
2401 | |
2402 | out: |
2403 | delayacct_freepages_end(); |
2404 | put_mems_allowed(); |
2405 | |
2406 | if (sc->nr_reclaimed) |
2407 | return sc->nr_reclaimed; |
2408 | |
2409 | /* |
2410 | * As hibernation is going on, kswapd is freezed so that it can't mark |
2411 | * the zone into all_unreclaimable. Thus bypassing all_unreclaimable |
2412 | * check. |
2413 | */ |
2414 | if (oom_killer_disabled) |
2415 | return 0; |
2416 | |
2417 | /* Aborted reclaim to try compaction? don't OOM, then */ |
2418 | if (aborted_reclaim) |
2419 | return 1; |
2420 | |
2421 | /* top priority shrink_zones still had more to do? don't OOM, then */ |
2422 | if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc)) |
2423 | return 1; |
2424 | |
2425 | return 0; |
2426 | } |
2427 | |
2428 | unsigned long try_to_free_pages(struct zonelist *zonelist, int order, |
2429 | gfp_t gfp_mask, nodemask_t *nodemask) |
2430 | { |
2431 | unsigned long nr_reclaimed; |
2432 | struct scan_control sc = { |
2433 | .gfp_mask = gfp_mask, |
2434 | .may_writepage = !laptop_mode, |
2435 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2436 | .may_unmap = 1, |
2437 | .may_swap = 1, |
2438 | .order = order, |
2439 | .target_mem_cgroup = NULL, |
2440 | .nodemask = nodemask, |
2441 | }; |
2442 | struct shrink_control shrink = { |
2443 | .gfp_mask = sc.gfp_mask, |
2444 | }; |
2445 | |
2446 | trace_mm_vmscan_direct_reclaim_begin(order, |
2447 | sc.may_writepage, |
2448 | gfp_mask); |
2449 | |
2450 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
2451 | |
2452 | trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); |
2453 | |
2454 | return nr_reclaimed; |
2455 | } |
2456 | |
2457 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
2458 | |
2459 | unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg, |
2460 | gfp_t gfp_mask, bool noswap, |
2461 | struct zone *zone, |
2462 | unsigned long *nr_scanned) |
2463 | { |
2464 | struct scan_control sc = { |
2465 | .nr_scanned = 0, |
2466 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2467 | .may_writepage = !laptop_mode, |
2468 | .may_unmap = 1, |
2469 | .may_swap = !noswap, |
2470 | .order = 0, |
2471 | .target_mem_cgroup = memcg, |
2472 | }; |
2473 | struct mem_cgroup_zone mz = { |
2474 | .mem_cgroup = memcg, |
2475 | .zone = zone, |
2476 | }; |
2477 | |
2478 | sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
2479 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); |
2480 | |
2481 | trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, |
2482 | sc.may_writepage, |
2483 | sc.gfp_mask); |
2484 | |
2485 | /* |
2486 | * NOTE: Although we can get the priority field, using it |
2487 | * here is not a good idea, since it limits the pages we can scan. |
2488 | * if we don't reclaim here, the shrink_zone from balance_pgdat |
2489 | * will pick up pages from other mem cgroup's as well. We hack |
2490 | * the priority and make it zero. |
2491 | */ |
2492 | shrink_mem_cgroup_zone(0, &mz, &sc); |
2493 | |
2494 | trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); |
2495 | |
2496 | *nr_scanned = sc.nr_scanned; |
2497 | return sc.nr_reclaimed; |
2498 | } |
2499 | |
2500 | unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, |
2501 | gfp_t gfp_mask, |
2502 | bool noswap) |
2503 | { |
2504 | struct zonelist *zonelist; |
2505 | unsigned long nr_reclaimed; |
2506 | int nid; |
2507 | struct scan_control sc = { |
2508 | .may_writepage = !laptop_mode, |
2509 | .may_unmap = 1, |
2510 | .may_swap = !noswap, |
2511 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2512 | .order = 0, |
2513 | .target_mem_cgroup = memcg, |
2514 | .nodemask = NULL, /* we don't care the placement */ |
2515 | .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
2516 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), |
2517 | }; |
2518 | struct shrink_control shrink = { |
2519 | .gfp_mask = sc.gfp_mask, |
2520 | }; |
2521 | |
2522 | /* |
2523 | * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't |
2524 | * take care of from where we get pages. So the node where we start the |
2525 | * scan does not need to be the current node. |
2526 | */ |
2527 | nid = mem_cgroup_select_victim_node(memcg); |
2528 | |
2529 | zonelist = NODE_DATA(nid)->node_zonelists; |
2530 | |
2531 | trace_mm_vmscan_memcg_reclaim_begin(0, |
2532 | sc.may_writepage, |
2533 | sc.gfp_mask); |
2534 | |
2535 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
2536 | |
2537 | trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); |
2538 | |
2539 | return nr_reclaimed; |
2540 | } |
2541 | #endif |
2542 | |
2543 | static void age_active_anon(struct zone *zone, struct scan_control *sc, |
2544 | int priority) |
2545 | { |
2546 | struct mem_cgroup *memcg; |
2547 | |
2548 | if (!total_swap_pages) |
2549 | return; |
2550 | |
2551 | memcg = mem_cgroup_iter(NULL, NULL, NULL); |
2552 | do { |
2553 | struct mem_cgroup_zone mz = { |
2554 | .mem_cgroup = memcg, |
2555 | .zone = zone, |
2556 | }; |
2557 | |
2558 | if (inactive_anon_is_low(&mz)) |
2559 | shrink_active_list(SWAP_CLUSTER_MAX, &mz, |
2560 | sc, priority, 0); |
2561 | |
2562 | memcg = mem_cgroup_iter(NULL, memcg, NULL); |
2563 | } while (memcg); |
2564 | } |
2565 | |
2566 | /* |
2567 | * pgdat_balanced is used when checking if a node is balanced for high-order |
2568 | * allocations. Only zones that meet watermarks and are in a zone allowed |
2569 | * by the callers classzone_idx are added to balanced_pages. The total of |
2570 | * balanced pages must be at least 25% of the zones allowed by classzone_idx |
2571 | * for the node to be considered balanced. Forcing all zones to be balanced |
2572 | * for high orders can cause excessive reclaim when there are imbalanced zones. |
2573 | * The choice of 25% is due to |
2574 | * o a 16M DMA zone that is balanced will not balance a zone on any |
2575 | * reasonable sized machine |
2576 | * o On all other machines, the top zone must be at least a reasonable |
2577 | * percentage of the middle zones. For example, on 32-bit x86, highmem |
2578 | * would need to be at least 256M for it to be balance a whole node. |
2579 | * Similarly, on x86-64 the Normal zone would need to be at least 1G |
2580 | * to balance a node on its own. These seemed like reasonable ratios. |
2581 | */ |
2582 | static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, |
2583 | int classzone_idx) |
2584 | { |
2585 | unsigned long present_pages = 0; |
2586 | int i; |
2587 | |
2588 | for (i = 0; i <= classzone_idx; i++) |
2589 | present_pages += pgdat->node_zones[i].present_pages; |
2590 | |
2591 | /* A special case here: if zone has no page, we think it's balanced */ |
2592 | return balanced_pages >= (present_pages >> 2); |
2593 | } |
2594 | |
2595 | /* is kswapd sleeping prematurely? */ |
2596 | static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, |
2597 | int classzone_idx) |
2598 | { |
2599 | int i; |
2600 | unsigned long balanced = 0; |
2601 | bool all_zones_ok = true; |
2602 | |
2603 | /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ |
2604 | if (remaining) |
2605 | return true; |
2606 | |
2607 | /* Check the watermark levels */ |
2608 | for (i = 0; i <= classzone_idx; i++) { |
2609 | struct zone *zone = pgdat->node_zones + i; |
2610 | |
2611 | if (!populated_zone(zone)) |
2612 | continue; |
2613 | |
2614 | /* |
2615 | * balance_pgdat() skips over all_unreclaimable after |
2616 | * DEF_PRIORITY. Effectively, it considers them balanced so |
2617 | * they must be considered balanced here as well if kswapd |
2618 | * is to sleep |
2619 | */ |
2620 | if (zone->all_unreclaimable) { |
2621 | balanced += zone->present_pages; |
2622 | continue; |
2623 | } |
2624 | |
2625 | if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), |
2626 | i, 0)) |
2627 | all_zones_ok = false; |
2628 | else |
2629 | balanced += zone->present_pages; |
2630 | } |
2631 | |
2632 | /* |
2633 | * For high-order requests, the balanced zones must contain at least |
2634 | * 25% of the nodes pages for kswapd to sleep. For order-0, all zones |
2635 | * must be balanced |
2636 | */ |
2637 | if (order) |
2638 | return !pgdat_balanced(pgdat, balanced, classzone_idx); |
2639 | else |
2640 | return !all_zones_ok; |
2641 | } |
2642 | |
2643 | /* |
2644 | * For kswapd, balance_pgdat() will work across all this node's zones until |
2645 | * they are all at high_wmark_pages(zone). |
2646 | * |
2647 | * Returns the final order kswapd was reclaiming at |
2648 | * |
2649 | * There is special handling here for zones which are full of pinned pages. |
2650 | * This can happen if the pages are all mlocked, or if they are all used by |
2651 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. |
2652 | * What we do is to detect the case where all pages in the zone have been |
2653 | * scanned twice and there has been zero successful reclaim. Mark the zone as |
2654 | * dead and from now on, only perform a short scan. Basically we're polling |
2655 | * the zone for when the problem goes away. |
2656 | * |
2657 | * kswapd scans the zones in the highmem->normal->dma direction. It skips |
2658 | * zones which have free_pages > high_wmark_pages(zone), but once a zone is |
2659 | * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the |
2660 | * lower zones regardless of the number of free pages in the lower zones. This |
2661 | * interoperates with the page allocator fallback scheme to ensure that aging |
2662 | * of pages is balanced across the zones. |
2663 | */ |
2664 | static unsigned long balance_pgdat(pg_data_t *pgdat, int order, |
2665 | int *classzone_idx) |
2666 | { |
2667 | int all_zones_ok; |
2668 | unsigned long balanced; |
2669 | int priority; |
2670 | int i; |
2671 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ |
2672 | unsigned long total_scanned; |
2673 | struct reclaim_state *reclaim_state = current->reclaim_state; |
2674 | unsigned long nr_soft_reclaimed; |
2675 | unsigned long nr_soft_scanned; |
2676 | struct scan_control sc = { |
2677 | .gfp_mask = GFP_KERNEL, |
2678 | .may_unmap = 1, |
2679 | .may_swap = 1, |
2680 | /* |
2681 | * kswapd doesn't want to be bailed out while reclaim. because |
2682 | * we want to put equal scanning pressure on each zone. |
2683 | */ |
2684 | .nr_to_reclaim = ULONG_MAX, |
2685 | .order = order, |
2686 | .target_mem_cgroup = NULL, |
2687 | }; |
2688 | struct shrink_control shrink = { |
2689 | .gfp_mask = sc.gfp_mask, |
2690 | }; |
2691 | loop_again: |
2692 | total_scanned = 0; |
2693 | sc.nr_reclaimed = 0; |
2694 | sc.may_writepage = !laptop_mode; |
2695 | count_vm_event(PAGEOUTRUN); |
2696 | |
2697 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
2698 | unsigned long lru_pages = 0; |
2699 | int has_under_min_watermark_zone = 0; |
2700 | |
2701 | /* The swap token gets in the way of swapout... */ |
2702 | if (!priority) |
2703 | disable_swap_token(NULL); |
2704 | |
2705 | all_zones_ok = 1; |
2706 | balanced = 0; |
2707 | |
2708 | /* |
2709 | * Scan in the highmem->dma direction for the highest |
2710 | * zone which needs scanning |
2711 | */ |
2712 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { |
2713 | struct zone *zone = pgdat->node_zones + i; |
2714 | |
2715 | if (!populated_zone(zone)) |
2716 | continue; |
2717 | |
2718 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
2719 | continue; |
2720 | |
2721 | /* |
2722 | * Do some background aging of the anon list, to give |
2723 | * pages a chance to be referenced before reclaiming. |
2724 | */ |
2725 | age_active_anon(zone, &sc, priority); |
2726 | |
2727 | if (!zone_watermark_ok_safe(zone, order, |
2728 | high_wmark_pages(zone), 0, 0)) { |
2729 | end_zone = i; |
2730 | break; |
2731 | } else { |
2732 | /* If balanced, clear the congested flag */ |
2733 | zone_clear_flag(zone, ZONE_CONGESTED); |
2734 | } |
2735 | } |
2736 | if (i < 0) |
2737 | goto out; |
2738 | |
2739 | for (i = 0; i <= end_zone; i++) { |
2740 | struct zone *zone = pgdat->node_zones + i; |
2741 | |
2742 | lru_pages += zone_reclaimable_pages(zone); |
2743 | } |
2744 | |
2745 | /* |
2746 | * Now scan the zone in the dma->highmem direction, stopping |
2747 | * at the last zone which needs scanning. |
2748 | * |
2749 | * We do this because the page allocator works in the opposite |
2750 | * direction. This prevents the page allocator from allocating |
2751 | * pages behind kswapd's direction of progress, which would |
2752 | * cause too much scanning of the lower zones. |
2753 | */ |
2754 | for (i = 0; i <= end_zone; i++) { |
2755 | struct zone *zone = pgdat->node_zones + i; |
2756 | int nr_slab; |
2757 | unsigned long balance_gap; |
2758 | |
2759 | if (!populated_zone(zone)) |
2760 | continue; |
2761 | |
2762 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
2763 | continue; |
2764 | |
2765 | sc.nr_scanned = 0; |
2766 | |
2767 | nr_soft_scanned = 0; |
2768 | /* |
2769 | * Call soft limit reclaim before calling shrink_zone. |
2770 | */ |
2771 | nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, |
2772 | order, sc.gfp_mask, |
2773 | &nr_soft_scanned); |
2774 | sc.nr_reclaimed += nr_soft_reclaimed; |
2775 | total_scanned += nr_soft_scanned; |
2776 | |
2777 | /* |
2778 | * We put equal pressure on every zone, unless |
2779 | * one zone has way too many pages free |
2780 | * already. The "too many pages" is defined |
2781 | * as the high wmark plus a "gap" where the |
2782 | * gap is either the low watermark or 1% |
2783 | * of the zone, whichever is smaller. |
2784 | */ |
2785 | balance_gap = min(low_wmark_pages(zone), |
2786 | (zone->present_pages + |
2787 | KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / |
2788 | KSWAPD_ZONE_BALANCE_GAP_RATIO); |
2789 | if (!zone_watermark_ok_safe(zone, order, |
2790 | high_wmark_pages(zone) + balance_gap, |
2791 | end_zone, 0)) { |
2792 | shrink_zone(priority, zone, &sc); |
2793 | |
2794 | reclaim_state->reclaimed_slab = 0; |
2795 | nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages); |
2796 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; |
2797 | total_scanned += sc.nr_scanned; |
2798 | |
2799 | if (nr_slab == 0 && !zone_reclaimable(zone)) |
2800 | zone->all_unreclaimable = 1; |
2801 | } |
2802 | |
2803 | /* |
2804 | * If we've done a decent amount of scanning and |
2805 | * the reclaim ratio is low, start doing writepage |
2806 | * even in laptop mode |
2807 | */ |
2808 | if (total_scanned > SWAP_CLUSTER_MAX * 2 && |
2809 | total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) |
2810 | sc.may_writepage = 1; |
2811 | |
2812 | if (zone->all_unreclaimable) { |
2813 | if (end_zone && end_zone == i) |
2814 | end_zone--; |
2815 | continue; |
2816 | } |
2817 | |
2818 | if (!zone_watermark_ok_safe(zone, order, |
2819 | high_wmark_pages(zone), end_zone, 0)) { |
2820 | all_zones_ok = 0; |
2821 | /* |
2822 | * We are still under min water mark. This |
2823 | * means that we have a GFP_ATOMIC allocation |
2824 | * failure risk. Hurry up! |
2825 | */ |
2826 | if (!zone_watermark_ok_safe(zone, order, |
2827 | min_wmark_pages(zone), end_zone, 0)) |
2828 | has_under_min_watermark_zone = 1; |
2829 | } else { |
2830 | /* |
2831 | * If a zone reaches its high watermark, |
2832 | * consider it to be no longer congested. It's |
2833 | * possible there are dirty pages backed by |
2834 | * congested BDIs but as pressure is relieved, |
2835 | * spectulatively avoid congestion waits |
2836 | */ |
2837 | zone_clear_flag(zone, ZONE_CONGESTED); |
2838 | if (i <= *classzone_idx) |
2839 | balanced += zone->present_pages; |
2840 | } |
2841 | |
2842 | } |
2843 | if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) |
2844 | break; /* kswapd: all done */ |
2845 | /* |
2846 | * OK, kswapd is getting into trouble. Take a nap, then take |
2847 | * another pass across the zones. |
2848 | */ |
2849 | if (total_scanned && (priority < DEF_PRIORITY - 2)) { |
2850 | if (has_under_min_watermark_zone) |
2851 | count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); |
2852 | else |
2853 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
2854 | } |
2855 | |
2856 | /* |
2857 | * We do this so kswapd doesn't build up large priorities for |
2858 | * example when it is freeing in parallel with allocators. It |
2859 | * matches the direct reclaim path behaviour in terms of impact |
2860 | * on zone->*_priority. |
2861 | */ |
2862 | if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) |
2863 | break; |
2864 | } |
2865 | out: |
2866 | |
2867 | /* |
2868 | * order-0: All zones must meet high watermark for a balanced node |
2869 | * high-order: Balanced zones must make up at least 25% of the node |
2870 | * for the node to be balanced |
2871 | */ |
2872 | if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { |
2873 | cond_resched(); |
2874 | |
2875 | try_to_freeze(); |
2876 | |
2877 | /* |
2878 | * Fragmentation may mean that the system cannot be |
2879 | * rebalanced for high-order allocations in all zones. |
2880 | * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, |
2881 | * it means the zones have been fully scanned and are still |
2882 | * not balanced. For high-order allocations, there is |
2883 | * little point trying all over again as kswapd may |
2884 | * infinite loop. |
2885 | * |
2886 | * Instead, recheck all watermarks at order-0 as they |
2887 | * are the most important. If watermarks are ok, kswapd will go |
2888 | * back to sleep. High-order users can still perform direct |
2889 | * reclaim if they wish. |
2890 | */ |
2891 | if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) |
2892 | order = sc.order = 0; |
2893 | |
2894 | goto loop_again; |
2895 | } |
2896 | |
2897 | /* |
2898 | * If kswapd was reclaiming at a higher order, it has the option of |
2899 | * sleeping without all zones being balanced. Before it does, it must |
2900 | * ensure that the watermarks for order-0 on *all* zones are met and |
2901 | * that the congestion flags are cleared. The congestion flag must |
2902 | * be cleared as kswapd is the only mechanism that clears the flag |
2903 | * and it is potentially going to sleep here. |
2904 | */ |
2905 | if (order) { |
2906 | for (i = 0; i <= end_zone; i++) { |
2907 | struct zone *zone = pgdat->node_zones + i; |
2908 | |
2909 | if (!populated_zone(zone)) |
2910 | continue; |
2911 | |
2912 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
2913 | continue; |
2914 | |
2915 | /* Confirm the zone is balanced for order-0 */ |
2916 | if (!zone_watermark_ok(zone, 0, |
2917 | high_wmark_pages(zone), 0, 0)) { |
2918 | order = sc.order = 0; |
2919 | goto loop_again; |
2920 | } |
2921 | |
2922 | /* If balanced, clear the congested flag */ |
2923 | zone_clear_flag(zone, ZONE_CONGESTED); |
2924 | if (i <= *classzone_idx) |
2925 | balanced += zone->present_pages; |
2926 | } |
2927 | } |
2928 | |
2929 | /* |
2930 | * Return the order we were reclaiming at so sleeping_prematurely() |
2931 | * makes a decision on the order we were last reclaiming at. However, |
2932 | * if another caller entered the allocator slow path while kswapd |
2933 | * was awake, order will remain at the higher level |
2934 | */ |
2935 | *classzone_idx = end_zone; |
2936 | return order; |
2937 | } |
2938 | |
2939 | static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) |
2940 | { |
2941 | long remaining = 0; |
2942 | DEFINE_WAIT(wait); |
2943 | |
2944 | if (freezing(current) || kthread_should_stop()) |
2945 | return; |
2946 | |
2947 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
2948 | |
2949 | /* Try to sleep for a short interval */ |
2950 | if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { |
2951 | remaining = schedule_timeout(HZ/10); |
2952 | finish_wait(&pgdat->kswapd_wait, &wait); |
2953 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
2954 | } |
2955 | |
2956 | /* |
2957 | * After a short sleep, check if it was a premature sleep. If not, then |
2958 | * go fully to sleep until explicitly woken up. |
2959 | */ |
2960 | if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { |
2961 | trace_mm_vmscan_kswapd_sleep(pgdat->node_id); |
2962 | |
2963 | /* |
2964 | * vmstat counters are not perfectly accurate and the estimated |
2965 | * value for counters such as NR_FREE_PAGES can deviate from the |
2966 | * true value by nr_online_cpus * threshold. To avoid the zone |
2967 | * watermarks being breached while under pressure, we reduce the |
2968 | * per-cpu vmstat threshold while kswapd is awake and restore |
2969 | * them before going back to sleep. |
2970 | */ |
2971 | set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); |
2972 | schedule(); |
2973 | set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); |
2974 | } else { |
2975 | if (remaining) |
2976 | count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); |
2977 | else |
2978 | count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); |
2979 | } |
2980 | finish_wait(&pgdat->kswapd_wait, &wait); |
2981 | } |
2982 | |
2983 | /* |
2984 | * The background pageout daemon, started as a kernel thread |
2985 | * from the init process. |
2986 | * |
2987 | * This basically trickles out pages so that we have _some_ |
2988 | * free memory available even if there is no other activity |
2989 | * that frees anything up. This is needed for things like routing |
2990 | * etc, where we otherwise might have all activity going on in |
2991 | * asynchronous contexts that cannot page things out. |
2992 | * |
2993 | * If there are applications that are active memory-allocators |
2994 | * (most normal use), this basically shouldn't matter. |
2995 | */ |
2996 | static int kswapd(void *p) |
2997 | { |
2998 | unsigned long order, new_order; |
2999 | unsigned balanced_order; |
3000 | int classzone_idx, new_classzone_idx; |
3001 | int balanced_classzone_idx; |
3002 | pg_data_t *pgdat = (pg_data_t*)p; |
3003 | struct task_struct *tsk = current; |
3004 | |
3005 | struct reclaim_state reclaim_state = { |
3006 | .reclaimed_slab = 0, |
3007 | }; |
3008 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); |
3009 | |
3010 | lockdep_set_current_reclaim_state(GFP_KERNEL); |
3011 | |
3012 | if (!cpumask_empty(cpumask)) |
3013 | set_cpus_allowed_ptr(tsk, cpumask); |
3014 | current->reclaim_state = &reclaim_state; |
3015 | |
3016 | /* |
3017 | * Tell the memory management that we're a "memory allocator", |
3018 | * and that if we need more memory we should get access to it |
3019 | * regardless (see "__alloc_pages()"). "kswapd" should |
3020 | * never get caught in the normal page freeing logic. |
3021 | * |
3022 | * (Kswapd normally doesn't need memory anyway, but sometimes |
3023 | * you need a small amount of memory in order to be able to |
3024 | * page out something else, and this flag essentially protects |
3025 | * us from recursively trying to free more memory as we're |
3026 | * trying to free the first piece of memory in the first place). |
3027 | */ |
3028 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; |
3029 | set_freezable(); |
3030 | |
3031 | order = new_order = 0; |
3032 | balanced_order = 0; |
3033 | classzone_idx = new_classzone_idx = pgdat->nr_zones - 1; |
3034 | balanced_classzone_idx = classzone_idx; |
3035 | for ( ; ; ) { |
3036 | int ret; |
3037 | |
3038 | /* |
3039 | * If the last balance_pgdat was unsuccessful it's unlikely a |
3040 | * new request of a similar or harder type will succeed soon |
3041 | * so consider going to sleep on the basis we reclaimed at |
3042 | */ |
3043 | if (balanced_classzone_idx >= new_classzone_idx && |
3044 | balanced_order == new_order) { |
3045 | new_order = pgdat->kswapd_max_order; |
3046 | new_classzone_idx = pgdat->classzone_idx; |
3047 | pgdat->kswapd_max_order = 0; |
3048 | pgdat->classzone_idx = pgdat->nr_zones - 1; |
3049 | } |
3050 | |
3051 | if (order < new_order || classzone_idx > new_classzone_idx) { |
3052 | /* |
3053 | * Don't sleep if someone wants a larger 'order' |
3054 | * allocation or has tigher zone constraints |
3055 | */ |
3056 | order = new_order; |
3057 | classzone_idx = new_classzone_idx; |
3058 | } else { |
3059 | kswapd_try_to_sleep(pgdat, balanced_order, |
3060 | balanced_classzone_idx); |
3061 | order = pgdat->kswapd_max_order; |
3062 | classzone_idx = pgdat->classzone_idx; |
3063 | new_order = order; |
3064 | new_classzone_idx = classzone_idx; |
3065 | pgdat->kswapd_max_order = 0; |
3066 | pgdat->classzone_idx = pgdat->nr_zones - 1; |
3067 | } |
3068 | |
3069 | ret = try_to_freeze(); |
3070 | if (kthread_should_stop()) |
3071 | break; |
3072 | |
3073 | /* |
3074 | * We can speed up thawing tasks if we don't call balance_pgdat |
3075 | * after returning from the refrigerator |
3076 | */ |
3077 | if (!ret) { |
3078 | trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); |
3079 | balanced_classzone_idx = classzone_idx; |
3080 | balanced_order = balance_pgdat(pgdat, order, |
3081 | &balanced_classzone_idx); |
3082 | } |
3083 | } |
3084 | return 0; |
3085 | } |
3086 | |
3087 | /* |
3088 | * A zone is low on free memory, so wake its kswapd task to service it. |
3089 | */ |
3090 | void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) |
3091 | { |
3092 | pg_data_t *pgdat; |
3093 | |
3094 | if (!populated_zone(zone)) |
3095 | return; |
3096 | |
3097 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
3098 | return; |
3099 | pgdat = zone->zone_pgdat; |
3100 | if (pgdat->kswapd_max_order < order) { |
3101 | pgdat->kswapd_max_order = order; |
3102 | pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); |
3103 | } |
3104 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
3105 | return; |
3106 | if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) |
3107 | return; |
3108 | |
3109 | trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); |
3110 | wake_up_interruptible(&pgdat->kswapd_wait); |
3111 | } |
3112 | |
3113 | /* |
3114 | * The reclaimable count would be mostly accurate. |
3115 | * The less reclaimable pages may be |
3116 | * - mlocked pages, which will be moved to unevictable list when encountered |
3117 | * - mapped pages, which may require several travels to be reclaimed |
3118 | * - dirty pages, which is not "instantly" reclaimable |
3119 | */ |
3120 | unsigned long global_reclaimable_pages(void) |
3121 | { |
3122 | int nr; |
3123 | |
3124 | nr = global_page_state(NR_ACTIVE_FILE) + |
3125 | global_page_state(NR_INACTIVE_FILE); |
3126 | |
3127 | if (nr_swap_pages > 0) |
3128 | nr += global_page_state(NR_ACTIVE_ANON) + |
3129 | global_page_state(NR_INACTIVE_ANON); |
3130 | |
3131 | return nr; |
3132 | } |
3133 | |
3134 | unsigned long zone_reclaimable_pages(struct zone *zone) |
3135 | { |
3136 | int nr; |
3137 | |
3138 | nr = zone_page_state(zone, NR_ACTIVE_FILE) + |
3139 | zone_page_state(zone, NR_INACTIVE_FILE); |
3140 | |
3141 | if (nr_swap_pages > 0) |
3142 | nr += zone_page_state(zone, NR_ACTIVE_ANON) + |
3143 | zone_page_state(zone, NR_INACTIVE_ANON); |
3144 | |
3145 | return nr; |
3146 | } |
3147 | |
3148 | #ifdef CONFIG_HIBERNATION |
3149 | /* |
3150 | * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of |
3151 | * freed pages. |
3152 | * |
3153 | * Rather than trying to age LRUs the aim is to preserve the overall |
3154 | * LRU order by reclaiming preferentially |
3155 | * inactive > active > active referenced > active mapped |
3156 | */ |
3157 | unsigned long shrink_all_memory(unsigned long nr_to_reclaim) |
3158 | { |
3159 | struct reclaim_state reclaim_state; |
3160 | struct scan_control sc = { |
3161 | .gfp_mask = GFP_HIGHUSER_MOVABLE, |
3162 | .may_swap = 1, |
3163 | .may_unmap = 1, |
3164 | .may_writepage = 1, |
3165 | .nr_to_reclaim = nr_to_reclaim, |
3166 | .hibernation_mode = 1, |
3167 | .order = 0, |
3168 | }; |
3169 | struct shrink_control shrink = { |
3170 | .gfp_mask = sc.gfp_mask, |
3171 | }; |
3172 | struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); |
3173 | struct task_struct *p = current; |
3174 | unsigned long nr_reclaimed; |
3175 | |
3176 | p->flags |= PF_MEMALLOC; |
3177 | lockdep_set_current_reclaim_state(sc.gfp_mask); |
3178 | reclaim_state.reclaimed_slab = 0; |
3179 | p->reclaim_state = &reclaim_state; |
3180 | |
3181 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
3182 | |
3183 | p->reclaim_state = NULL; |
3184 | lockdep_clear_current_reclaim_state(); |
3185 | p->flags &= ~PF_MEMALLOC; |
3186 | |
3187 | return nr_reclaimed; |
3188 | } |
3189 | #endif /* CONFIG_HIBERNATION */ |
3190 | |
3191 | /* It's optimal to keep kswapds on the same CPUs as their memory, but |
3192 | not required for correctness. So if the last cpu in a node goes |
3193 | away, we get changed to run anywhere: as the first one comes back, |
3194 | restore their cpu bindings. */ |
3195 | static int __devinit cpu_callback(struct notifier_block *nfb, |
3196 | unsigned long action, void *hcpu) |
3197 | { |
3198 | int nid; |
3199 | |
3200 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { |
3201 | for_each_node_state(nid, N_HIGH_MEMORY) { |
3202 | pg_data_t *pgdat = NODE_DATA(nid); |
3203 | const struct cpumask *mask; |
3204 | |
3205 | mask = cpumask_of_node(pgdat->node_id); |
3206 | |
3207 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
3208 | /* One of our CPUs online: restore mask */ |
3209 | set_cpus_allowed_ptr(pgdat->kswapd, mask); |
3210 | } |
3211 | } |
3212 | return NOTIFY_OK; |
3213 | } |
3214 | |
3215 | /* |
3216 | * This kswapd start function will be called by init and node-hot-add. |
3217 | * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. |
3218 | */ |
3219 | int kswapd_run(int nid) |
3220 | { |
3221 | pg_data_t *pgdat = NODE_DATA(nid); |
3222 | int ret = 0; |
3223 | |
3224 | if (pgdat->kswapd) |
3225 | return 0; |
3226 | |
3227 | pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); |
3228 | if (IS_ERR(pgdat->kswapd)) { |
3229 | /* failure at boot is fatal */ |
3230 | BUG_ON(system_state == SYSTEM_BOOTING); |
3231 | printk("Failed to start kswapd on node %d\n",nid); |
3232 | ret = -1; |
3233 | } |
3234 | return ret; |
3235 | } |
3236 | |
3237 | /* |
3238 | * Called by memory hotplug when all memory in a node is offlined. |
3239 | */ |
3240 | void kswapd_stop(int nid) |
3241 | { |
3242 | struct task_struct *kswapd = NODE_DATA(nid)->kswapd; |
3243 | |
3244 | if (kswapd) |
3245 | kthread_stop(kswapd); |
3246 | } |
3247 | |
3248 | static int __init kswapd_init(void) |
3249 | { |
3250 | int nid; |
3251 | |
3252 | swap_setup(); |
3253 | for_each_node_state(nid, N_HIGH_MEMORY) |
3254 | kswapd_run(nid); |
3255 | hotcpu_notifier(cpu_callback, 0); |
3256 | return 0; |
3257 | } |
3258 | |
3259 | module_init(kswapd_init) |
3260 | |
3261 | #ifdef CONFIG_NUMA |
3262 | /* |
3263 | * Zone reclaim mode |
3264 | * |
3265 | * If non-zero call zone_reclaim when the number of free pages falls below |
3266 | * the watermarks. |
3267 | */ |
3268 | int zone_reclaim_mode __read_mostly; |
3269 | |
3270 | #define RECLAIM_OFF 0 |
3271 | #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ |
3272 | #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ |
3273 | #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ |
3274 | |
3275 | /* |
3276 | * Priority for ZONE_RECLAIM. This determines the fraction of pages |
3277 | * of a node considered for each zone_reclaim. 4 scans 1/16th of |
3278 | * a zone. |
3279 | */ |
3280 | #define ZONE_RECLAIM_PRIORITY 4 |
3281 | |
3282 | /* |
3283 | * Percentage of pages in a zone that must be unmapped for zone_reclaim to |
3284 | * occur. |
3285 | */ |
3286 | int sysctl_min_unmapped_ratio = 1; |
3287 | |
3288 | /* |
3289 | * If the number of slab pages in a zone grows beyond this percentage then |
3290 | * slab reclaim needs to occur. |
3291 | */ |
3292 | int sysctl_min_slab_ratio = 5; |
3293 | |
3294 | static inline unsigned long zone_unmapped_file_pages(struct zone *zone) |
3295 | { |
3296 | unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); |
3297 | unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + |
3298 | zone_page_state(zone, NR_ACTIVE_FILE); |
3299 | |
3300 | /* |
3301 | * It's possible for there to be more file mapped pages than |
3302 | * accounted for by the pages on the file LRU lists because |
3303 | * tmpfs pages accounted for as ANON can also be FILE_MAPPED |
3304 | */ |
3305 | return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; |
3306 | } |
3307 | |
3308 | /* Work out how many page cache pages we can reclaim in this reclaim_mode */ |
3309 | static long zone_pagecache_reclaimable(struct zone *zone) |
3310 | { |
3311 | long nr_pagecache_reclaimable; |
3312 | long delta = 0; |
3313 | |
3314 | /* |
3315 | * If RECLAIM_SWAP is set, then all file pages are considered |
3316 | * potentially reclaimable. Otherwise, we have to worry about |
3317 | * pages like swapcache and zone_unmapped_file_pages() provides |
3318 | * a better estimate |
3319 | */ |
3320 | if (zone_reclaim_mode & RECLAIM_SWAP) |
3321 | nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); |
3322 | else |
3323 | nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); |
3324 | |
3325 | /* If we can't clean pages, remove dirty pages from consideration */ |
3326 | if (!(zone_reclaim_mode & RECLAIM_WRITE)) |
3327 | delta += zone_page_state(zone, NR_FILE_DIRTY); |
3328 | |
3329 | /* Watch for any possible underflows due to delta */ |
3330 | if (unlikely(delta > nr_pagecache_reclaimable)) |
3331 | delta = nr_pagecache_reclaimable; |
3332 | |
3333 | return nr_pagecache_reclaimable - delta; |
3334 | } |
3335 | |
3336 | /* |
3337 | * Try to free up some pages from this zone through reclaim. |
3338 | */ |
3339 | static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
3340 | { |
3341 | /* Minimum pages needed in order to stay on node */ |
3342 | const unsigned long nr_pages = 1 << order; |
3343 | struct task_struct *p = current; |
3344 | struct reclaim_state reclaim_state; |
3345 | int priority; |
3346 | struct scan_control sc = { |
3347 | .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), |
3348 | .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), |
3349 | .may_swap = 1, |
3350 | .nr_to_reclaim = max_t(unsigned long, nr_pages, |
3351 | SWAP_CLUSTER_MAX), |
3352 | .gfp_mask = gfp_mask, |
3353 | .order = order, |
3354 | }; |
3355 | struct shrink_control shrink = { |
3356 | .gfp_mask = sc.gfp_mask, |
3357 | }; |
3358 | unsigned long nr_slab_pages0, nr_slab_pages1; |
3359 | |
3360 | cond_resched(); |
3361 | /* |
3362 | * We need to be able to allocate from the reserves for RECLAIM_SWAP |
3363 | * and we also need to be able to write out pages for RECLAIM_WRITE |
3364 | * and RECLAIM_SWAP. |
3365 | */ |
3366 | p->flags |= PF_MEMALLOC | PF_SWAPWRITE; |
3367 | lockdep_set_current_reclaim_state(gfp_mask); |
3368 | reclaim_state.reclaimed_slab = 0; |
3369 | p->reclaim_state = &reclaim_state; |
3370 | |
3371 | if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { |
3372 | /* |
3373 | * Free memory by calling shrink zone with increasing |
3374 | * priorities until we have enough memory freed. |
3375 | */ |
3376 | priority = ZONE_RECLAIM_PRIORITY; |
3377 | do { |
3378 | shrink_zone(priority, zone, &sc); |
3379 | priority--; |
3380 | } while (priority >= 0 && sc.nr_reclaimed < nr_pages); |
3381 | } |
3382 | |
3383 | nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
3384 | if (nr_slab_pages0 > zone->min_slab_pages) { |
3385 | /* |
3386 | * shrink_slab() does not currently allow us to determine how |
3387 | * many pages were freed in this zone. So we take the current |
3388 | * number of slab pages and shake the slab until it is reduced |
3389 | * by the same nr_pages that we used for reclaiming unmapped |
3390 | * pages. |
3391 | * |
3392 | * Note that shrink_slab will free memory on all zones and may |
3393 | * take a long time. |
3394 | */ |
3395 | for (;;) { |
3396 | unsigned long lru_pages = zone_reclaimable_pages(zone); |
3397 | |
3398 | /* No reclaimable slab or very low memory pressure */ |
3399 | if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages)) |
3400 | break; |
3401 | |
3402 | /* Freed enough memory */ |
3403 | nr_slab_pages1 = zone_page_state(zone, |
3404 | NR_SLAB_RECLAIMABLE); |
3405 | if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) |
3406 | break; |
3407 | } |
3408 | |
3409 | /* |
3410 | * Update nr_reclaimed by the number of slab pages we |
3411 | * reclaimed from this zone. |
3412 | */ |
3413 | nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
3414 | if (nr_slab_pages1 < nr_slab_pages0) |
3415 | sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; |
3416 | } |
3417 | |
3418 | p->reclaim_state = NULL; |
3419 | current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); |
3420 | lockdep_clear_current_reclaim_state(); |
3421 | return sc.nr_reclaimed >= nr_pages; |
3422 | } |
3423 | |
3424 | int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
3425 | { |
3426 | int node_id; |
3427 | int ret; |
3428 | |
3429 | /* |
3430 | * Zone reclaim reclaims unmapped file backed pages and |
3431 | * slab pages if we are over the defined limits. |
3432 | * |
3433 | * A small portion of unmapped file backed pages is needed for |
3434 | * file I/O otherwise pages read by file I/O will be immediately |
3435 | * thrown out if the zone is overallocated. So we do not reclaim |
3436 | * if less than a specified percentage of the zone is used by |
3437 | * unmapped file backed pages. |
3438 | */ |
3439 | if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && |
3440 | zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) |
3441 | return ZONE_RECLAIM_FULL; |
3442 | |
3443 | if (zone->all_unreclaimable) |
3444 | return ZONE_RECLAIM_FULL; |
3445 | |
3446 | /* |
3447 | * Do not scan if the allocation should not be delayed. |
3448 | */ |
3449 | if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) |
3450 | return ZONE_RECLAIM_NOSCAN; |
3451 | |
3452 | /* |
3453 | * Only run zone reclaim on the local zone or on zones that do not |
3454 | * have associated processors. This will favor the local processor |
3455 | * over remote processors and spread off node memory allocations |
3456 | * as wide as possible. |
3457 | */ |
3458 | node_id = zone_to_nid(zone); |
3459 | if (node_state(node_id, N_CPU) && node_id != numa_node_id()) |
3460 | return ZONE_RECLAIM_NOSCAN; |
3461 | |
3462 | if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) |
3463 | return ZONE_RECLAIM_NOSCAN; |
3464 | |
3465 | ret = __zone_reclaim(zone, gfp_mask, order); |
3466 | zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); |
3467 | |
3468 | if (!ret) |
3469 | count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); |
3470 | |
3471 | return ret; |
3472 | } |
3473 | #endif |
3474 | |
3475 | /* |
3476 | * page_evictable - test whether a page is evictable |
3477 | * @page: the page to test |
3478 | * @vma: the VMA in which the page is or will be mapped, may be NULL |
3479 | * |
3480 | * Test whether page is evictable--i.e., should be placed on active/inactive |
3481 | * lists vs unevictable list. The vma argument is !NULL when called from the |
3482 | * fault path to determine how to instantate a new page. |
3483 | * |
3484 | * Reasons page might not be evictable: |
3485 | * (1) page's mapping marked unevictable |
3486 | * (2) page is part of an mlocked VMA |
3487 | * |
3488 | */ |
3489 | int page_evictable(struct page *page, struct vm_area_struct *vma) |
3490 | { |
3491 | |
3492 | if (mapping_unevictable(page_mapping(page))) |
3493 | return 0; |
3494 | |
3495 | if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) |
3496 | return 0; |
3497 | |
3498 | return 1; |
3499 | } |
3500 | |
3501 | #ifdef CONFIG_SHMEM |
3502 | /** |
3503 | * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list |
3504 | * @pages: array of pages to check |
3505 | * @nr_pages: number of pages to check |
3506 | * |
3507 | * Checks pages for evictability and moves them to the appropriate lru list. |
3508 | * |
3509 | * This function is only used for SysV IPC SHM_UNLOCK. |
3510 | */ |
3511 | void check_move_unevictable_pages(struct page **pages, int nr_pages) |
3512 | { |
3513 | struct lruvec *lruvec; |
3514 | struct zone *zone = NULL; |
3515 | int pgscanned = 0; |
3516 | int pgrescued = 0; |
3517 | int i; |
3518 | |
3519 | for (i = 0; i < nr_pages; i++) { |
3520 | struct page *page = pages[i]; |
3521 | struct zone *pagezone; |
3522 | |
3523 | pgscanned++; |
3524 | pagezone = page_zone(page); |
3525 | if (pagezone != zone) { |
3526 | if (zone) |
3527 | spin_unlock_irq(&zone->lru_lock); |
3528 | zone = pagezone; |
3529 | spin_lock_irq(&zone->lru_lock); |
3530 | } |
3531 | |
3532 | if (!PageLRU(page) || !PageUnevictable(page)) |
3533 | continue; |
3534 | |
3535 | if (page_evictable(page, NULL)) { |
3536 | enum lru_list lru = page_lru_base_type(page); |
3537 | |
3538 | VM_BUG_ON(PageActive(page)); |
3539 | ClearPageUnevictable(page); |
3540 | __dec_zone_state(zone, NR_UNEVICTABLE); |
3541 | lruvec = mem_cgroup_lru_move_lists(zone, page, |
3542 | LRU_UNEVICTABLE, lru); |
3543 | list_move(&page->lru, &lruvec->lists[lru]); |
3544 | __inc_zone_state(zone, NR_INACTIVE_ANON + lru); |
3545 | pgrescued++; |
3546 | } |
3547 | } |
3548 | |
3549 | if (zone) { |
3550 | __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued); |
3551 | __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned); |
3552 | spin_unlock_irq(&zone->lru_lock); |
3553 | } |
3554 | } |
3555 | #endif /* CONFIG_SHMEM */ |
3556 | |
3557 | static void warn_scan_unevictable_pages(void) |
3558 | { |
3559 | printk_once(KERN_WARNING |
3560 | "%s: The scan_unevictable_pages sysctl/node-interface has been " |
3561 | "disabled for lack of a legitimate use case. If you have " |
3562 | "one, please send an email to linux-mm@kvack.org.\n", |
3563 | current->comm); |
3564 | } |
3565 | |
3566 | /* |
3567 | * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of |
3568 | * all nodes' unevictable lists for evictable pages |
3569 | */ |
3570 | unsigned long scan_unevictable_pages; |
3571 | |
3572 | int scan_unevictable_handler(struct ctl_table *table, int write, |
3573 | void __user *buffer, |
3574 | size_t *length, loff_t *ppos) |
3575 | { |
3576 | warn_scan_unevictable_pages(); |
3577 | proc_doulongvec_minmax(table, write, buffer, length, ppos); |
3578 | scan_unevictable_pages = 0; |
3579 | return 0; |
3580 | } |
3581 | |
3582 | #ifdef CONFIG_NUMA |
3583 | /* |
3584 | * per node 'scan_unevictable_pages' attribute. On demand re-scan of |
3585 | * a specified node's per zone unevictable lists for evictable pages. |
3586 | */ |
3587 | |
3588 | static ssize_t read_scan_unevictable_node(struct device *dev, |
3589 | struct device_attribute *attr, |
3590 | char *buf) |
3591 | { |
3592 | warn_scan_unevictable_pages(); |
3593 | return sprintf(buf, "0\n"); /* always zero; should fit... */ |
3594 | } |
3595 | |
3596 | static ssize_t write_scan_unevictable_node(struct device *dev, |
3597 | struct device_attribute *attr, |
3598 | const char *buf, size_t count) |
3599 | { |
3600 | warn_scan_unevictable_pages(); |
3601 | return 1; |
3602 | } |
3603 | |
3604 | |
3605 | static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, |
3606 | read_scan_unevictable_node, |
3607 | write_scan_unevictable_node); |
3608 | |
3609 | int scan_unevictable_register_node(struct node *node) |
3610 | { |
3611 | return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages); |
3612 | } |
3613 | |
3614 | void scan_unevictable_unregister_node(struct node *node) |
3615 | { |
3616 | device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages); |
3617 | } |
3618 | #endif |
3619 |
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