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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/slab.h> | |
17 | #include <linux/kernel_stat.h> | |
18 | #include <linux/swap.h> | |
19 | #include <linux/pagemap.h> | |
20 | #include <linux/init.h> | |
21 | #include <linux/highmem.h> | |
22 | #include <linux/vmstat.h> | |
23 | #include <linux/file.h> | |
24 | #include <linux/writeback.h> | |
25 | #include <linux/blkdev.h> | |
26 | #include <linux/buffer_head.h> /* for try_to_release_page(), | |
27 | buffer_heads_over_limit */ | |
28 | #include <linux/mm_inline.h> | |
29 | #include <linux/pagevec.h> | |
30 | #include <linux/backing-dev.h> | |
31 | #include <linux/rmap.h> | |
32 | #include <linux/topology.h> | |
33 | #include <linux/cpu.h> | |
34 | #include <linux/cpuset.h> | |
35 | #include <linux/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 | ||
44 | #include <asm/tlbflush.h> | |
45 | #include <asm/div64.h> | |
46 | ||
47 | #include <linux/swapops.h> | |
48 | ||
49 | #include "internal.h" | |
50 | ||
51 | struct scan_control { | |
52 | /* Incremented by the number of inactive pages that were scanned */ | |
53 | unsigned long nr_scanned; | |
54 | ||
55 | /* Number of pages freed so far during a call to shrink_zones() */ | |
56 | unsigned long nr_reclaimed; | |
57 | ||
58 | /* How many pages shrink_list() should reclaim */ | |
59 | unsigned long nr_to_reclaim; | |
60 | ||
61 | unsigned long hibernation_mode; | |
62 | ||
63 | /* This context's GFP mask */ | |
64 | gfp_t gfp_mask; | |
65 | ||
66 | int may_writepage; | |
67 | ||
68 | /* Can mapped pages be reclaimed? */ | |
69 | int may_unmap; | |
70 | ||
71 | /* Can pages be swapped as part of reclaim? */ | |
72 | int may_swap; | |
73 | ||
74 | int swappiness; | |
75 | ||
76 | int all_unreclaimable; | |
77 | ||
78 | int order; | |
79 | ||
80 | /* Which cgroup do we reclaim from */ | |
81 | struct mem_cgroup *mem_cgroup; | |
82 | ||
83 | /* | |
84 | * Nodemask of nodes allowed by the caller. If NULL, all nodes | |
85 | * are scanned. | |
86 | */ | |
87 | nodemask_t *nodemask; | |
88 | ||
89 | /* Pluggable isolate pages callback */ | |
90 | unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst, | |
91 | unsigned long *scanned, int order, int mode, | |
92 | struct zone *z, struct mem_cgroup *mem_cont, | |
93 | int active, int file); | |
94 | }; | |
95 | ||
96 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) | |
97 | ||
98 | #ifdef ARCH_HAS_PREFETCH | |
99 | #define prefetch_prev_lru_page(_page, _base, _field) \ | |
100 | do { \ | |
101 | if ((_page)->lru.prev != _base) { \ | |
102 | struct page *prev; \ | |
103 | \ | |
104 | prev = lru_to_page(&(_page->lru)); \ | |
105 | prefetch(&prev->_field); \ | |
106 | } \ | |
107 | } while (0) | |
108 | #else | |
109 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) | |
110 | #endif | |
111 | ||
112 | #ifdef ARCH_HAS_PREFETCHW | |
113 | #define prefetchw_prev_lru_page(_page, _base, _field) \ | |
114 | do { \ | |
115 | if ((_page)->lru.prev != _base) { \ | |
116 | struct page *prev; \ | |
117 | \ | |
118 | prev = lru_to_page(&(_page->lru)); \ | |
119 | prefetchw(&prev->_field); \ | |
120 | } \ | |
121 | } while (0) | |
122 | #else | |
123 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) | |
124 | #endif | |
125 | ||
126 | /* | |
127 | * From 0 .. 100. Higher means more swappy. | |
128 | */ | |
129 | int vm_swappiness = 60; | |
130 | long vm_total_pages; /* The total number of pages which the VM controls */ | |
131 | ||
132 | static LIST_HEAD(shrinker_list); | |
133 | static DECLARE_RWSEM(shrinker_rwsem); | |
134 | ||
135 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR | |
136 | #define scanning_global_lru(sc) (!(sc)->mem_cgroup) | |
137 | #else | |
138 | #define scanning_global_lru(sc) (1) | |
139 | #endif | |
140 | ||
141 | static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, | |
142 | struct scan_control *sc) | |
143 | { | |
144 | if (!scanning_global_lru(sc)) | |
145 | return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); | |
146 | ||
147 | return &zone->reclaim_stat; | |
148 | } | |
149 | ||
150 | static unsigned long zone_nr_lru_pages(struct zone *zone, | |
151 | struct scan_control *sc, enum lru_list lru) | |
152 | { | |
153 | if (!scanning_global_lru(sc)) | |
154 | return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru); | |
155 | ||
156 | return zone_page_state(zone, NR_LRU_BASE + lru); | |
157 | } | |
158 | ||
159 | ||
160 | /* | |
161 | * Add a shrinker callback to be called from the vm | |
162 | */ | |
163 | void register_shrinker(struct shrinker *shrinker) | |
164 | { | |
165 | shrinker->nr = 0; | |
166 | down_write(&shrinker_rwsem); | |
167 | list_add_tail(&shrinker->list, &shrinker_list); | |
168 | up_write(&shrinker_rwsem); | |
169 | } | |
170 | EXPORT_SYMBOL(register_shrinker); | |
171 | ||
172 | /* | |
173 | * Remove one | |
174 | */ | |
175 | void unregister_shrinker(struct shrinker *shrinker) | |
176 | { | |
177 | down_write(&shrinker_rwsem); | |
178 | list_del(&shrinker->list); | |
179 | up_write(&shrinker_rwsem); | |
180 | } | |
181 | EXPORT_SYMBOL(unregister_shrinker); | |
182 | ||
183 | #define SHRINK_BATCH 128 | |
184 | /* | |
185 | * Call the shrink functions to age shrinkable caches | |
186 | * | |
187 | * Here we assume it costs one seek to replace a lru page and that it also | |
188 | * takes a seek to recreate a cache object. With this in mind we age equal | |
189 | * percentages of the lru and ageable caches. This should balance the seeks | |
190 | * generated by these structures. | |
191 | * | |
192 | * If the vm encountered mapped pages on the LRU it increase the pressure on | |
193 | * slab to avoid swapping. | |
194 | * | |
195 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. | |
196 | * | |
197 | * `lru_pages' represents the number of on-LRU pages in all the zones which | |
198 | * are eligible for the caller's allocation attempt. It is used for balancing | |
199 | * slab reclaim versus page reclaim. | |
200 | * | |
201 | * Returns the number of slab objects which we shrunk. | |
202 | */ | |
203 | unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, | |
204 | unsigned long lru_pages) | |
205 | { | |
206 | struct shrinker *shrinker; | |
207 | unsigned long ret = 0; | |
208 | ||
209 | if (scanned == 0) | |
210 | scanned = SWAP_CLUSTER_MAX; | |
211 | ||
212 | if (!down_read_trylock(&shrinker_rwsem)) | |
213 | return 1; /* Assume we'll be able to shrink next time */ | |
214 | ||
215 | list_for_each_entry(shrinker, &shrinker_list, list) { | |
216 | unsigned long long delta; | |
217 | unsigned long total_scan; | |
218 | unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask); | |
219 | ||
220 | delta = (4 * scanned) / shrinker->seeks; | |
221 | delta *= max_pass; | |
222 | do_div(delta, lru_pages + 1); | |
223 | shrinker->nr += delta; | |
224 | if (shrinker->nr < 0) { | |
225 | printk(KERN_ERR "shrink_slab: %pF negative objects to " | |
226 | "delete nr=%ld\n", | |
227 | shrinker->shrink, shrinker->nr); | |
228 | shrinker->nr = max_pass; | |
229 | } | |
230 | ||
231 | /* | |
232 | * Avoid risking looping forever due to too large nr value: | |
233 | * never try to free more than twice the estimate number of | |
234 | * freeable entries. | |
235 | */ | |
236 | if (shrinker->nr > max_pass * 2) | |
237 | shrinker->nr = max_pass * 2; | |
238 | ||
239 | total_scan = shrinker->nr; | |
240 | shrinker->nr = 0; | |
241 | ||
242 | while (total_scan >= SHRINK_BATCH) { | |
243 | long this_scan = SHRINK_BATCH; | |
244 | int shrink_ret; | |
245 | int nr_before; | |
246 | ||
247 | nr_before = (*shrinker->shrink)(0, gfp_mask); | |
248 | shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask); | |
249 | if (shrink_ret == -1) | |
250 | break; | |
251 | if (shrink_ret < nr_before) | |
252 | ret += nr_before - shrink_ret; | |
253 | count_vm_events(SLABS_SCANNED, this_scan); | |
254 | total_scan -= this_scan; | |
255 | ||
256 | cond_resched(); | |
257 | } | |
258 | ||
259 | shrinker->nr += total_scan; | |
260 | } | |
261 | up_read(&shrinker_rwsem); | |
262 | return ret; | |
263 | } | |
264 | ||
265 | /* Called without lock on whether page is mapped, so answer is unstable */ | |
266 | static inline int page_mapping_inuse(struct page *page) | |
267 | { | |
268 | struct address_space *mapping; | |
269 | ||
270 | /* Page is in somebody's page tables. */ | |
271 | if (page_mapped(page)) | |
272 | return 1; | |
273 | ||
274 | /* Be more reluctant to reclaim swapcache than pagecache */ | |
275 | if (PageSwapCache(page)) | |
276 | return 1; | |
277 | ||
278 | mapping = page_mapping(page); | |
279 | if (!mapping) | |
280 | return 0; | |
281 | ||
282 | /* File is mmap'd by somebody? */ | |
283 | return mapping_mapped(mapping); | |
284 | } | |
285 | ||
286 | static inline int is_page_cache_freeable(struct page *page) | |
287 | { | |
288 | /* | |
289 | * A freeable page cache page is referenced only by the caller | |
290 | * that isolated the page, the page cache radix tree and | |
291 | * optional buffer heads at page->private. | |
292 | */ | |
293 | return page_count(page) - page_has_private(page) == 2; | |
294 | } | |
295 | ||
296 | static int may_write_to_queue(struct backing_dev_info *bdi) | |
297 | { | |
298 | if (current->flags & PF_SWAPWRITE) | |
299 | return 1; | |
300 | if (!bdi_write_congested(bdi)) | |
301 | return 1; | |
302 | if (bdi == current->backing_dev_info) | |
303 | return 1; | |
304 | return 0; | |
305 | } | |
306 | ||
307 | /* | |
308 | * We detected a synchronous write error writing a page out. Probably | |
309 | * -ENOSPC. We need to propagate that into the address_space for a subsequent | |
310 | * fsync(), msync() or close(). | |
311 | * | |
312 | * The tricky part is that after writepage we cannot touch the mapping: nothing | |
313 | * prevents it from being freed up. But we have a ref on the page and once | |
314 | * that page is locked, the mapping is pinned. | |
315 | * | |
316 | * We're allowed to run sleeping lock_page() here because we know the caller has | |
317 | * __GFP_FS. | |
318 | */ | |
319 | static void handle_write_error(struct address_space *mapping, | |
320 | struct page *page, int error) | |
321 | { | |
322 | lock_page(page); | |
323 | if (page_mapping(page) == mapping) | |
324 | mapping_set_error(mapping, error); | |
325 | unlock_page(page); | |
326 | } | |
327 | ||
328 | /* Request for sync pageout. */ | |
329 | enum pageout_io { | |
330 | PAGEOUT_IO_ASYNC, | |
331 | PAGEOUT_IO_SYNC, | |
332 | }; | |
333 | ||
334 | /* possible outcome of pageout() */ | |
335 | typedef enum { | |
336 | /* failed to write page out, page is locked */ | |
337 | PAGE_KEEP, | |
338 | /* move page to the active list, page is locked */ | |
339 | PAGE_ACTIVATE, | |
340 | /* page has been sent to the disk successfully, page is unlocked */ | |
341 | PAGE_SUCCESS, | |
342 | /* page is clean and locked */ | |
343 | PAGE_CLEAN, | |
344 | } pageout_t; | |
345 | ||
346 | /* | |
347 | * pageout is called by shrink_page_list() for each dirty page. | |
348 | * Calls ->writepage(). | |
349 | */ | |
350 | static pageout_t pageout(struct page *page, struct address_space *mapping, | |
351 | enum pageout_io sync_writeback) | |
352 | { | |
353 | /* | |
354 | * If the page is dirty, only perform writeback if that write | |
355 | * will be non-blocking. To prevent this allocation from being | |
356 | * stalled by pagecache activity. But note that there may be | |
357 | * stalls if we need to run get_block(). We could test | |
358 | * PagePrivate for that. | |
359 | * | |
360 | * If this process is currently in __generic_file_aio_write() against | |
361 | * this page's queue, we can perform writeback even if that | |
362 | * will block. | |
363 | * | |
364 | * If the page is swapcache, write it back even if that would | |
365 | * block, for some throttling. This happens by accident, because | |
366 | * swap_backing_dev_info is bust: it doesn't reflect the | |
367 | * congestion state of the swapdevs. Easy to fix, if needed. | |
368 | */ | |
369 | if (!is_page_cache_freeable(page)) | |
370 | return PAGE_KEEP; | |
371 | if (!mapping) { | |
372 | /* | |
373 | * Some data journaling orphaned pages can have | |
374 | * page->mapping == NULL while being dirty with clean buffers. | |
375 | */ | |
376 | if (page_has_private(page)) { | |
377 | if (try_to_free_buffers(page)) { | |
378 | ClearPageDirty(page); | |
379 | printk("%s: orphaned page\n", __func__); | |
380 | return PAGE_CLEAN; | |
381 | } | |
382 | } | |
383 | return PAGE_KEEP; | |
384 | } | |
385 | if (mapping->a_ops->writepage == NULL) | |
386 | return PAGE_ACTIVATE; | |
387 | if (!may_write_to_queue(mapping->backing_dev_info)) | |
388 | return PAGE_KEEP; | |
389 | ||
390 | if (clear_page_dirty_for_io(page)) { | |
391 | int res; | |
392 | struct writeback_control wbc = { | |
393 | .sync_mode = WB_SYNC_NONE, | |
394 | .nr_to_write = SWAP_CLUSTER_MAX, | |
395 | .range_start = 0, | |
396 | .range_end = LLONG_MAX, | |
397 | .nonblocking = 1, | |
398 | .for_reclaim = 1, | |
399 | }; | |
400 | ||
401 | SetPageReclaim(page); | |
402 | res = mapping->a_ops->writepage(page, &wbc); | |
403 | if (res < 0) | |
404 | handle_write_error(mapping, page, res); | |
405 | if (res == AOP_WRITEPAGE_ACTIVATE) { | |
406 | ClearPageReclaim(page); | |
407 | return PAGE_ACTIVATE; | |
408 | } | |
409 | ||
410 | /* | |
411 | * Wait on writeback if requested to. This happens when | |
412 | * direct reclaiming a large contiguous area and the | |
413 | * first attempt to free a range of pages fails. | |
414 | */ | |
415 | if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC) | |
416 | wait_on_page_writeback(page); | |
417 | ||
418 | if (!PageWriteback(page)) { | |
419 | /* synchronous write or broken a_ops? */ | |
420 | ClearPageReclaim(page); | |
421 | } | |
422 | inc_zone_page_state(page, NR_VMSCAN_WRITE); | |
423 | return PAGE_SUCCESS; | |
424 | } | |
425 | ||
426 | return PAGE_CLEAN; | |
427 | } | |
428 | ||
429 | /* | |
430 | * Same as remove_mapping, but if the page is removed from the mapping, it | |
431 | * gets returned with a refcount of 0. | |
432 | */ | |
433 | static int __remove_mapping(struct address_space *mapping, struct page *page) | |
434 | { | |
435 | BUG_ON(!PageLocked(page)); | |
436 | BUG_ON(mapping != page_mapping(page)); | |
437 | ||
438 | spin_lock_irq(&mapping->tree_lock); | |
439 | /* | |
440 | * The non racy check for a busy page. | |
441 | * | |
442 | * Must be careful with the order of the tests. When someone has | |
443 | * a ref to the page, it may be possible that they dirty it then | |
444 | * drop the reference. So if PageDirty is tested before page_count | |
445 | * here, then the following race may occur: | |
446 | * | |
447 | * get_user_pages(&page); | |
448 | * [user mapping goes away] | |
449 | * write_to(page); | |
450 | * !PageDirty(page) [good] | |
451 | * SetPageDirty(page); | |
452 | * put_page(page); | |
453 | * !page_count(page) [good, discard it] | |
454 | * | |
455 | * [oops, our write_to data is lost] | |
456 | * | |
457 | * Reversing the order of the tests ensures such a situation cannot | |
458 | * escape unnoticed. The smp_rmb is needed to ensure the page->flags | |
459 | * load is not satisfied before that of page->_count. | |
460 | * | |
461 | * Note that if SetPageDirty is always performed via set_page_dirty, | |
462 | * and thus under tree_lock, then this ordering is not required. | |
463 | */ | |
464 | if (!page_freeze_refs(page, 2)) | |
465 | goto cannot_free; | |
466 | /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ | |
467 | if (unlikely(PageDirty(page))) { | |
468 | page_unfreeze_refs(page, 2); | |
469 | goto cannot_free; | |
470 | } | |
471 | ||
472 | if (PageSwapCache(page)) { | |
473 | swp_entry_t swap = { .val = page_private(page) }; | |
474 | __delete_from_swap_cache(page); | |
475 | spin_unlock_irq(&mapping->tree_lock); | |
476 | swapcache_free(swap, page); | |
477 | } else { | |
478 | __remove_from_page_cache(page); | |
479 | spin_unlock_irq(&mapping->tree_lock); | |
480 | mem_cgroup_uncharge_cache_page(page); | |
481 | } | |
482 | ||
483 | return 1; | |
484 | ||
485 | cannot_free: | |
486 | spin_unlock_irq(&mapping->tree_lock); | |
487 | return 0; | |
488 | } | |
489 | ||
490 | /* | |
491 | * Attempt to detach a locked page from its ->mapping. If it is dirty or if | |
492 | * someone else has a ref on the page, abort and return 0. If it was | |
493 | * successfully detached, return 1. Assumes the caller has a single ref on | |
494 | * this page. | |
495 | */ | |
496 | int remove_mapping(struct address_space *mapping, struct page *page) | |
497 | { | |
498 | if (__remove_mapping(mapping, page)) { | |
499 | /* | |
500 | * Unfreezing the refcount with 1 rather than 2 effectively | |
501 | * drops the pagecache ref for us without requiring another | |
502 | * atomic operation. | |
503 | */ | |
504 | page_unfreeze_refs(page, 1); | |
505 | return 1; | |
506 | } | |
507 | return 0; | |
508 | } | |
509 | ||
510 | /** | |
511 | * putback_lru_page - put previously isolated page onto appropriate LRU list | |
512 | * @page: page to be put back to appropriate lru list | |
513 | * | |
514 | * Add previously isolated @page to appropriate LRU list. | |
515 | * Page may still be unevictable for other reasons. | |
516 | * | |
517 | * lru_lock must not be held, interrupts must be enabled. | |
518 | */ | |
519 | void putback_lru_page(struct page *page) | |
520 | { | |
521 | int lru; | |
522 | int active = !!TestClearPageActive(page); | |
523 | int was_unevictable = PageUnevictable(page); | |
524 | ||
525 | VM_BUG_ON(PageLRU(page)); | |
526 | ||
527 | redo: | |
528 | ClearPageUnevictable(page); | |
529 | ||
530 | if (page_evictable(page, NULL)) { | |
531 | /* | |
532 | * For evictable pages, we can use the cache. | |
533 | * In event of a race, worst case is we end up with an | |
534 | * unevictable page on [in]active list. | |
535 | * We know how to handle that. | |
536 | */ | |
537 | lru = active + page_lru_base_type(page); | |
538 | lru_cache_add_lru(page, lru); | |
539 | } else { | |
540 | /* | |
541 | * Put unevictable pages directly on zone's unevictable | |
542 | * list. | |
543 | */ | |
544 | lru = LRU_UNEVICTABLE; | |
545 | add_page_to_unevictable_list(page); | |
546 | /* | |
547 | * When racing with an mlock clearing (page is | |
548 | * unlocked), make sure that if the other thread does | |
549 | * not observe our setting of PG_lru and fails | |
550 | * isolation, we see PG_mlocked cleared below and move | |
551 | * the page back to the evictable list. | |
552 | * | |
553 | * The other side is TestClearPageMlocked(). | |
554 | */ | |
555 | smp_mb(); | |
556 | } | |
557 | ||
558 | /* | |
559 | * page's status can change while we move it among lru. If an evictable | |
560 | * page is on unevictable list, it never be freed. To avoid that, | |
561 | * check after we added it to the list, again. | |
562 | */ | |
563 | if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { | |
564 | if (!isolate_lru_page(page)) { | |
565 | put_page(page); | |
566 | goto redo; | |
567 | } | |
568 | /* This means someone else dropped this page from LRU | |
569 | * So, it will be freed or putback to LRU again. There is | |
570 | * nothing to do here. | |
571 | */ | |
572 | } | |
573 | ||
574 | if (was_unevictable && lru != LRU_UNEVICTABLE) | |
575 | count_vm_event(UNEVICTABLE_PGRESCUED); | |
576 | else if (!was_unevictable && lru == LRU_UNEVICTABLE) | |
577 | count_vm_event(UNEVICTABLE_PGCULLED); | |
578 | ||
579 | put_page(page); /* drop ref from isolate */ | |
580 | } | |
581 | ||
582 | /* | |
583 | * shrink_page_list() returns the number of reclaimed pages | |
584 | */ | |
585 | static unsigned long shrink_page_list(struct list_head *page_list, | |
586 | struct scan_control *sc, | |
587 | enum pageout_io sync_writeback) | |
588 | { | |
589 | LIST_HEAD(ret_pages); | |
590 | struct pagevec freed_pvec; | |
591 | int pgactivate = 0; | |
592 | unsigned long nr_reclaimed = 0; | |
593 | unsigned long vm_flags; | |
594 | ||
595 | cond_resched(); | |
596 | ||
597 | pagevec_init(&freed_pvec, 1); | |
598 | while (!list_empty(page_list)) { | |
599 | struct address_space *mapping; | |
600 | struct page *page; | |
601 | int may_enter_fs; | |
602 | int referenced; | |
603 | ||
604 | cond_resched(); | |
605 | ||
606 | page = lru_to_page(page_list); | |
607 | list_del(&page->lru); | |
608 | ||
609 | if (!trylock_page(page)) | |
610 | goto keep; | |
611 | ||
612 | VM_BUG_ON(PageActive(page)); | |
613 | ||
614 | sc->nr_scanned++; | |
615 | ||
616 | if (unlikely(!page_evictable(page, NULL))) | |
617 | goto cull_mlocked; | |
618 | ||
619 | if (!sc->may_unmap && page_mapped(page)) | |
620 | goto keep_locked; | |
621 | ||
622 | /* Double the slab pressure for mapped and swapcache pages */ | |
623 | if (page_mapped(page) || PageSwapCache(page)) | |
624 | sc->nr_scanned++; | |
625 | ||
626 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || | |
627 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); | |
628 | ||
629 | if (PageWriteback(page)) { | |
630 | /* | |
631 | * Synchronous reclaim is performed in two passes, | |
632 | * first an asynchronous pass over the list to | |
633 | * start parallel writeback, and a second synchronous | |
634 | * pass to wait for the IO to complete. Wait here | |
635 | * for any page for which writeback has already | |
636 | * started. | |
637 | */ | |
638 | if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs) | |
639 | wait_on_page_writeback(page); | |
640 | else | |
641 | goto keep_locked; | |
642 | } | |
643 | ||
644 | referenced = page_referenced(page, 1, | |
645 | sc->mem_cgroup, &vm_flags); | |
646 | /* | |
647 | * In active use or really unfreeable? Activate it. | |
648 | * If page which have PG_mlocked lost isoltation race, | |
649 | * try_to_unmap moves it to unevictable list | |
650 | */ | |
651 | if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && | |
652 | referenced && page_mapping_inuse(page) | |
653 | && !(vm_flags & VM_LOCKED)) | |
654 | goto activate_locked; | |
655 | ||
656 | /* | |
657 | * Anonymous process memory has backing store? | |
658 | * Try to allocate it some swap space here. | |
659 | */ | |
660 | if (PageAnon(page) && !PageSwapCache(page)) { | |
661 | if (!(sc->gfp_mask & __GFP_IO)) | |
662 | goto keep_locked; | |
663 | if (!add_to_swap(page)) | |
664 | goto activate_locked; | |
665 | may_enter_fs = 1; | |
666 | } | |
667 | ||
668 | mapping = page_mapping(page); | |
669 | ||
670 | /* | |
671 | * The page is mapped into the page tables of one or more | |
672 | * processes. Try to unmap it here. | |
673 | */ | |
674 | if (page_mapped(page) && mapping) { | |
675 | switch (try_to_unmap(page, TTU_UNMAP)) { | |
676 | case SWAP_FAIL: | |
677 | goto activate_locked; | |
678 | case SWAP_AGAIN: | |
679 | goto keep_locked; | |
680 | case SWAP_MLOCK: | |
681 | goto cull_mlocked; | |
682 | case SWAP_SUCCESS: | |
683 | ; /* try to free the page below */ | |
684 | } | |
685 | } | |
686 | ||
687 | if (PageDirty(page)) { | |
688 | if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced) | |
689 | goto keep_locked; | |
690 | if (!may_enter_fs) | |
691 | goto keep_locked; | |
692 | if (!sc->may_writepage) | |
693 | goto keep_locked; | |
694 | ||
695 | /* Page is dirty, try to write it out here */ | |
696 | switch (pageout(page, mapping, sync_writeback)) { | |
697 | case PAGE_KEEP: | |
698 | goto keep_locked; | |
699 | case PAGE_ACTIVATE: | |
700 | goto activate_locked; | |
701 | case PAGE_SUCCESS: | |
702 | if (PageWriteback(page) || PageDirty(page)) | |
703 | goto keep; | |
704 | /* | |
705 | * A synchronous write - probably a ramdisk. Go | |
706 | * ahead and try to reclaim the page. | |
707 | */ | |
708 | if (!trylock_page(page)) | |
709 | goto keep; | |
710 | if (PageDirty(page) || PageWriteback(page)) | |
711 | goto keep_locked; | |
712 | mapping = page_mapping(page); | |
713 | case PAGE_CLEAN: | |
714 | ; /* try to free the page below */ | |
715 | } | |
716 | } | |
717 | ||
718 | /* | |
719 | * If the page has buffers, try to free the buffer mappings | |
720 | * associated with this page. If we succeed we try to free | |
721 | * the page as well. | |
722 | * | |
723 | * We do this even if the page is PageDirty(). | |
724 | * try_to_release_page() does not perform I/O, but it is | |
725 | * possible for a page to have PageDirty set, but it is actually | |
726 | * clean (all its buffers are clean). This happens if the | |
727 | * buffers were written out directly, with submit_bh(). ext3 | |
728 | * will do this, as well as the blockdev mapping. | |
729 | * try_to_release_page() will discover that cleanness and will | |
730 | * drop the buffers and mark the page clean - it can be freed. | |
731 | * | |
732 | * Rarely, pages can have buffers and no ->mapping. These are | |
733 | * the pages which were not successfully invalidated in | |
734 | * truncate_complete_page(). We try to drop those buffers here | |
735 | * and if that worked, and the page is no longer mapped into | |
736 | * process address space (page_count == 1) it can be freed. | |
737 | * Otherwise, leave the page on the LRU so it is swappable. | |
738 | */ | |
739 | if (page_has_private(page)) { | |
740 | if (!try_to_release_page(page, sc->gfp_mask)) | |
741 | goto activate_locked; | |
742 | if (!mapping && page_count(page) == 1) { | |
743 | unlock_page(page); | |
744 | if (put_page_testzero(page)) | |
745 | goto free_it; | |
746 | else { | |
747 | /* | |
748 | * rare race with speculative reference. | |
749 | * the speculative reference will free | |
750 | * this page shortly, so we may | |
751 | * increment nr_reclaimed here (and | |
752 | * leave it off the LRU). | |
753 | */ | |
754 | nr_reclaimed++; | |
755 | continue; | |
756 | } | |
757 | } | |
758 | } | |
759 | ||
760 | if (!mapping || !__remove_mapping(mapping, page)) | |
761 | goto keep_locked; | |
762 | ||
763 | /* | |
764 | * At this point, we have no other references and there is | |
765 | * no way to pick any more up (removed from LRU, removed | |
766 | * from pagecache). Can use non-atomic bitops now (and | |
767 | * we obviously don't have to worry about waking up a process | |
768 | * waiting on the page lock, because there are no references. | |
769 | */ | |
770 | __clear_page_locked(page); | |
771 | free_it: | |
772 | nr_reclaimed++; | |
773 | if (!pagevec_add(&freed_pvec, page)) { | |
774 | __pagevec_free(&freed_pvec); | |
775 | pagevec_reinit(&freed_pvec); | |
776 | } | |
777 | continue; | |
778 | ||
779 | cull_mlocked: | |
780 | if (PageSwapCache(page)) | |
781 | try_to_free_swap(page); | |
782 | unlock_page(page); | |
783 | putback_lru_page(page); | |
784 | continue; | |
785 | ||
786 | activate_locked: | |
787 | /* Not a candidate for swapping, so reclaim swap space. */ | |
788 | if (PageSwapCache(page) && vm_swap_full()) | |
789 | try_to_free_swap(page); | |
790 | VM_BUG_ON(PageActive(page)); | |
791 | SetPageActive(page); | |
792 | pgactivate++; | |
793 | keep_locked: | |
794 | unlock_page(page); | |
795 | keep: | |
796 | list_add(&page->lru, &ret_pages); | |
797 | VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); | |
798 | } | |
799 | list_splice(&ret_pages, page_list); | |
800 | if (pagevec_count(&freed_pvec)) | |
801 | __pagevec_free(&freed_pvec); | |
802 | count_vm_events(PGACTIVATE, pgactivate); | |
803 | return nr_reclaimed; | |
804 | } | |
805 | ||
806 | /* LRU Isolation modes. */ | |
807 | #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */ | |
808 | #define ISOLATE_ACTIVE 1 /* Isolate active pages. */ | |
809 | #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */ | |
810 | ||
811 | /* | |
812 | * Attempt to remove the specified page from its LRU. Only take this page | |
813 | * if it is of the appropriate PageActive status. Pages which are being | |
814 | * freed elsewhere are also ignored. | |
815 | * | |
816 | * page: page to consider | |
817 | * mode: one of the LRU isolation modes defined above | |
818 | * | |
819 | * returns 0 on success, -ve errno on failure. | |
820 | */ | |
821 | int __isolate_lru_page(struct page *page, int mode, int file) | |
822 | { | |
823 | int ret = -EINVAL; | |
824 | ||
825 | /* Only take pages on the LRU. */ | |
826 | if (!PageLRU(page)) | |
827 | return ret; | |
828 | ||
829 | /* | |
830 | * When checking the active state, we need to be sure we are | |
831 | * dealing with comparible boolean values. Take the logical not | |
832 | * of each. | |
833 | */ | |
834 | if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) | |
835 | return ret; | |
836 | ||
837 | if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) | |
838 | return ret; | |
839 | ||
840 | /* | |
841 | * When this function is being called for lumpy reclaim, we | |
842 | * initially look into all LRU pages, active, inactive and | |
843 | * unevictable; only give shrink_page_list evictable pages. | |
844 | */ | |
845 | if (PageUnevictable(page)) | |
846 | return ret; | |
847 | ||
848 | ret = -EBUSY; | |
849 | ||
850 | if (likely(get_page_unless_zero(page))) { | |
851 | /* | |
852 | * Be careful not to clear PageLRU until after we're | |
853 | * sure the page is not being freed elsewhere -- the | |
854 | * page release code relies on it. | |
855 | */ | |
856 | ClearPageLRU(page); | |
857 | ret = 0; | |
858 | } | |
859 | ||
860 | return ret; | |
861 | } | |
862 | ||
863 | /* | |
864 | * zone->lru_lock is heavily contended. Some of the functions that | |
865 | * shrink the lists perform better by taking out a batch of pages | |
866 | * and working on them outside the LRU lock. | |
867 | * | |
868 | * For pagecache intensive workloads, this function is the hottest | |
869 | * spot in the kernel (apart from copy_*_user functions). | |
870 | * | |
871 | * Appropriate locks must be held before calling this function. | |
872 | * | |
873 | * @nr_to_scan: The number of pages to look through on the list. | |
874 | * @src: The LRU list to pull pages off. | |
875 | * @dst: The temp list to put pages on to. | |
876 | * @scanned: The number of pages that were scanned. | |
877 | * @order: The caller's attempted allocation order | |
878 | * @mode: One of the LRU isolation modes | |
879 | * @file: True [1] if isolating file [!anon] pages | |
880 | * | |
881 | * returns how many pages were moved onto *@dst. | |
882 | */ | |
883 | static unsigned long isolate_lru_pages(unsigned long nr_to_scan, | |
884 | struct list_head *src, struct list_head *dst, | |
885 | unsigned long *scanned, int order, int mode, int file) | |
886 | { | |
887 | unsigned long nr_taken = 0; | |
888 | unsigned long scan; | |
889 | ||
890 | for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { | |
891 | struct page *page; | |
892 | unsigned long pfn; | |
893 | unsigned long end_pfn; | |
894 | unsigned long page_pfn; | |
895 | int zone_id; | |
896 | ||
897 | page = lru_to_page(src); | |
898 | prefetchw_prev_lru_page(page, src, flags); | |
899 | ||
900 | VM_BUG_ON(!PageLRU(page)); | |
901 | ||
902 | switch (__isolate_lru_page(page, mode, file)) { | |
903 | case 0: | |
904 | list_move(&page->lru, dst); | |
905 | mem_cgroup_del_lru(page); | |
906 | nr_taken++; | |
907 | break; | |
908 | ||
909 | case -EBUSY: | |
910 | /* else it is being freed elsewhere */ | |
911 | list_move(&page->lru, src); | |
912 | mem_cgroup_rotate_lru_list(page, page_lru(page)); | |
913 | continue; | |
914 | ||
915 | default: | |
916 | BUG(); | |
917 | } | |
918 | ||
919 | if (!order) | |
920 | continue; | |
921 | ||
922 | /* | |
923 | * Attempt to take all pages in the order aligned region | |
924 | * surrounding the tag page. Only take those pages of | |
925 | * the same active state as that tag page. We may safely | |
926 | * round the target page pfn down to the requested order | |
927 | * as the mem_map is guarenteed valid out to MAX_ORDER, | |
928 | * where that page is in a different zone we will detect | |
929 | * it from its zone id and abort this block scan. | |
930 | */ | |
931 | zone_id = page_zone_id(page); | |
932 | page_pfn = page_to_pfn(page); | |
933 | pfn = page_pfn & ~((1 << order) - 1); | |
934 | end_pfn = pfn + (1 << order); | |
935 | for (; pfn < end_pfn; pfn++) { | |
936 | struct page *cursor_page; | |
937 | ||
938 | /* The target page is in the block, ignore it. */ | |
939 | if (unlikely(pfn == page_pfn)) | |
940 | continue; | |
941 | ||
942 | /* Avoid holes within the zone. */ | |
943 | if (unlikely(!pfn_valid_within(pfn))) | |
944 | break; | |
945 | ||
946 | cursor_page = pfn_to_page(pfn); | |
947 | ||
948 | /* Check that we have not crossed a zone boundary. */ | |
949 | if (unlikely(page_zone_id(cursor_page) != zone_id)) | |
950 | continue; | |
951 | ||
952 | /* | |
953 | * If we don't have enough swap space, reclaiming of | |
954 | * anon page which don't already have a swap slot is | |
955 | * pointless. | |
956 | */ | |
957 | if (nr_swap_pages <= 0 && PageAnon(cursor_page) && | |
958 | !PageSwapCache(cursor_page)) | |
959 | continue; | |
960 | ||
961 | if (__isolate_lru_page(cursor_page, mode, file) == 0) { | |
962 | list_move(&cursor_page->lru, dst); | |
963 | mem_cgroup_del_lru(cursor_page); | |
964 | nr_taken++; | |
965 | scan++; | |
966 | } | |
967 | } | |
968 | } | |
969 | ||
970 | *scanned = scan; | |
971 | return nr_taken; | |
972 | } | |
973 | ||
974 | static unsigned long isolate_pages_global(unsigned long nr, | |
975 | struct list_head *dst, | |
976 | unsigned long *scanned, int order, | |
977 | int mode, struct zone *z, | |
978 | struct mem_cgroup *mem_cont, | |
979 | int active, int file) | |
980 | { | |
981 | int lru = LRU_BASE; | |
982 | if (active) | |
983 | lru += LRU_ACTIVE; | |
984 | if (file) | |
985 | lru += LRU_FILE; | |
986 | return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, | |
987 | mode, file); | |
988 | } | |
989 | ||
990 | /* | |
991 | * clear_active_flags() is a helper for shrink_active_list(), clearing | |
992 | * any active bits from the pages in the list. | |
993 | */ | |
994 | static unsigned long clear_active_flags(struct list_head *page_list, | |
995 | unsigned int *count) | |
996 | { | |
997 | int nr_active = 0; | |
998 | int lru; | |
999 | struct page *page; | |
1000 | ||
1001 | list_for_each_entry(page, page_list, lru) { | |
1002 | lru = page_lru_base_type(page); | |
1003 | if (PageActive(page)) { | |
1004 | lru += LRU_ACTIVE; | |
1005 | ClearPageActive(page); | |
1006 | nr_active++; | |
1007 | } | |
1008 | count[lru]++; | |
1009 | } | |
1010 | ||
1011 | return nr_active; | |
1012 | } | |
1013 | ||
1014 | /** | |
1015 | * isolate_lru_page - tries to isolate a page from its LRU list | |
1016 | * @page: page to isolate from its LRU list | |
1017 | * | |
1018 | * Isolates a @page from an LRU list, clears PageLRU and adjusts the | |
1019 | * vmstat statistic corresponding to whatever LRU list the page was on. | |
1020 | * | |
1021 | * Returns 0 if the page was removed from an LRU list. | |
1022 | * Returns -EBUSY if the page was not on an LRU list. | |
1023 | * | |
1024 | * The returned page will have PageLRU() cleared. If it was found on | |
1025 | * the active list, it will have PageActive set. If it was found on | |
1026 | * the unevictable list, it will have the PageUnevictable bit set. That flag | |
1027 | * may need to be cleared by the caller before letting the page go. | |
1028 | * | |
1029 | * The vmstat statistic corresponding to the list on which the page was | |
1030 | * found will be decremented. | |
1031 | * | |
1032 | * Restrictions: | |
1033 | * (1) Must be called with an elevated refcount on the page. This is a | |
1034 | * fundamentnal difference from isolate_lru_pages (which is called | |
1035 | * without a stable reference). | |
1036 | * (2) the lru_lock must not be held. | |
1037 | * (3) interrupts must be enabled. | |
1038 | */ | |
1039 | int isolate_lru_page(struct page *page) | |
1040 | { | |
1041 | int ret = -EBUSY; | |
1042 | ||
1043 | if (PageLRU(page)) { | |
1044 | struct zone *zone = page_zone(page); | |
1045 | ||
1046 | spin_lock_irq(&zone->lru_lock); | |
1047 | if (PageLRU(page) && get_page_unless_zero(page)) { | |
1048 | int lru = page_lru(page); | |
1049 | ret = 0; | |
1050 | ClearPageLRU(page); | |
1051 | ||
1052 | del_page_from_lru_list(zone, page, lru); | |
1053 | } | |
1054 | spin_unlock_irq(&zone->lru_lock); | |
1055 | } | |
1056 | return ret; | |
1057 | } | |
1058 | ||
1059 | /* | |
1060 | * Are there way too many processes in the direct reclaim path already? | |
1061 | */ | |
1062 | static int too_many_isolated(struct zone *zone, int file, | |
1063 | struct scan_control *sc) | |
1064 | { | |
1065 | unsigned long inactive, isolated; | |
1066 | ||
1067 | if (current_is_kswapd()) | |
1068 | return 0; | |
1069 | ||
1070 | if (!scanning_global_lru(sc)) | |
1071 | return 0; | |
1072 | ||
1073 | if (file) { | |
1074 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); | |
1075 | isolated = zone_page_state(zone, NR_ISOLATED_FILE); | |
1076 | } else { | |
1077 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); | |
1078 | isolated = zone_page_state(zone, NR_ISOLATED_ANON); | |
1079 | } | |
1080 | ||
1081 | return isolated > inactive; | |
1082 | } | |
1083 | ||
1084 | /* | |
1085 | * shrink_inactive_list() is a helper for shrink_zone(). It returns the number | |
1086 | * of reclaimed pages | |
1087 | */ | |
1088 | static unsigned long shrink_inactive_list(unsigned long max_scan, | |
1089 | struct zone *zone, struct scan_control *sc, | |
1090 | int priority, int file) | |
1091 | { | |
1092 | LIST_HEAD(page_list); | |
1093 | struct pagevec pvec; | |
1094 | unsigned long nr_scanned = 0; | |
1095 | unsigned long nr_reclaimed = 0; | |
1096 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); | |
1097 | int lumpy_reclaim = 0; | |
1098 | ||
1099 | while (unlikely(too_many_isolated(zone, file, sc))) { | |
1100 | congestion_wait(BLK_RW_ASYNC, HZ/10); | |
1101 | ||
1102 | /* We are about to die and free our memory. Return now. */ | |
1103 | if (fatal_signal_pending(current)) | |
1104 | return SWAP_CLUSTER_MAX; | |
1105 | } | |
1106 | ||
1107 | /* | |
1108 | * If we need a large contiguous chunk of memory, or have | |
1109 | * trouble getting a small set of contiguous pages, we | |
1110 | * will reclaim both active and inactive pages. | |
1111 | * | |
1112 | * We use the same threshold as pageout congestion_wait below. | |
1113 | */ | |
1114 | if (sc->order > PAGE_ALLOC_COSTLY_ORDER) | |
1115 | lumpy_reclaim = 1; | |
1116 | else if (sc->order && priority < DEF_PRIORITY - 2) | |
1117 | lumpy_reclaim = 1; | |
1118 | ||
1119 | pagevec_init(&pvec, 1); | |
1120 | ||
1121 | lru_add_drain(); | |
1122 | spin_lock_irq(&zone->lru_lock); | |
1123 | do { | |
1124 | struct page *page; | |
1125 | unsigned long nr_taken; | |
1126 | unsigned long nr_scan; | |
1127 | unsigned long nr_freed; | |
1128 | unsigned long nr_active; | |
1129 | unsigned int count[NR_LRU_LISTS] = { 0, }; | |
1130 | int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE; | |
1131 | unsigned long nr_anon; | |
1132 | unsigned long nr_file; | |
1133 | ||
1134 | nr_taken = sc->isolate_pages(SWAP_CLUSTER_MAX, | |
1135 | &page_list, &nr_scan, sc->order, mode, | |
1136 | zone, sc->mem_cgroup, 0, file); | |
1137 | ||
1138 | if (scanning_global_lru(sc)) { | |
1139 | zone->pages_scanned += nr_scan; | |
1140 | if (current_is_kswapd()) | |
1141 | __count_zone_vm_events(PGSCAN_KSWAPD, zone, | |
1142 | nr_scan); | |
1143 | else | |
1144 | __count_zone_vm_events(PGSCAN_DIRECT, zone, | |
1145 | nr_scan); | |
1146 | } | |
1147 | ||
1148 | if (nr_taken == 0) | |
1149 | goto done; | |
1150 | ||
1151 | nr_active = clear_active_flags(&page_list, count); | |
1152 | __count_vm_events(PGDEACTIVATE, nr_active); | |
1153 | ||
1154 | __mod_zone_page_state(zone, NR_ACTIVE_FILE, | |
1155 | -count[LRU_ACTIVE_FILE]); | |
1156 | __mod_zone_page_state(zone, NR_INACTIVE_FILE, | |
1157 | -count[LRU_INACTIVE_FILE]); | |
1158 | __mod_zone_page_state(zone, NR_ACTIVE_ANON, | |
1159 | -count[LRU_ACTIVE_ANON]); | |
1160 | __mod_zone_page_state(zone, NR_INACTIVE_ANON, | |
1161 | -count[LRU_INACTIVE_ANON]); | |
1162 | ||
1163 | nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; | |
1164 | nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; | |
1165 | __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon); | |
1166 | __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file); | |
1167 | ||
1168 | reclaim_stat->recent_scanned[0] += nr_anon; | |
1169 | reclaim_stat->recent_scanned[1] += nr_file; | |
1170 | ||
1171 | spin_unlock_irq(&zone->lru_lock); | |
1172 | ||
1173 | nr_scanned += nr_scan; | |
1174 | nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC); | |
1175 | ||
1176 | /* | |
1177 | * If we are direct reclaiming for contiguous pages and we do | |
1178 | * not reclaim everything in the list, try again and wait | |
1179 | * for IO to complete. This will stall high-order allocations | |
1180 | * but that should be acceptable to the caller | |
1181 | */ | |
1182 | if (nr_freed < nr_taken && !current_is_kswapd() && | |
1183 | lumpy_reclaim) { | |
1184 | congestion_wait(BLK_RW_ASYNC, HZ/10); | |
1185 | ||
1186 | /* | |
1187 | * The attempt at page out may have made some | |
1188 | * of the pages active, mark them inactive again. | |
1189 | */ | |
1190 | nr_active = clear_active_flags(&page_list, count); | |
1191 | count_vm_events(PGDEACTIVATE, nr_active); | |
1192 | ||
1193 | nr_freed += shrink_page_list(&page_list, sc, | |
1194 | PAGEOUT_IO_SYNC); | |
1195 | } | |
1196 | ||
1197 | nr_reclaimed += nr_freed; | |
1198 | ||
1199 | local_irq_disable(); | |
1200 | if (current_is_kswapd()) | |
1201 | __count_vm_events(KSWAPD_STEAL, nr_freed); | |
1202 | __count_zone_vm_events(PGSTEAL, zone, nr_freed); | |
1203 | ||
1204 | spin_lock(&zone->lru_lock); | |
1205 | /* | |
1206 | * Put back any unfreeable pages. | |
1207 | */ | |
1208 | while (!list_empty(&page_list)) { | |
1209 | int lru; | |
1210 | page = lru_to_page(&page_list); | |
1211 | VM_BUG_ON(PageLRU(page)); | |
1212 | list_del(&page->lru); | |
1213 | if (unlikely(!page_evictable(page, NULL))) { | |
1214 | spin_unlock_irq(&zone->lru_lock); | |
1215 | putback_lru_page(page); | |
1216 | spin_lock_irq(&zone->lru_lock); | |
1217 | continue; | |
1218 | } | |
1219 | SetPageLRU(page); | |
1220 | lru = page_lru(page); | |
1221 | add_page_to_lru_list(zone, page, lru); | |
1222 | if (is_active_lru(lru)) { | |
1223 | int file = is_file_lru(lru); | |
1224 | reclaim_stat->recent_rotated[file]++; | |
1225 | } | |
1226 | if (!pagevec_add(&pvec, page)) { | |
1227 | spin_unlock_irq(&zone->lru_lock); | |
1228 | __pagevec_release(&pvec); | |
1229 | spin_lock_irq(&zone->lru_lock); | |
1230 | } | |
1231 | } | |
1232 | __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); | |
1233 | __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); | |
1234 | ||
1235 | } while (nr_scanned < max_scan); | |
1236 | ||
1237 | done: | |
1238 | spin_unlock_irq(&zone->lru_lock); | |
1239 | pagevec_release(&pvec); | |
1240 | return nr_reclaimed; | |
1241 | } | |
1242 | ||
1243 | /* | |
1244 | * We are about to scan this zone at a certain priority level. If that priority | |
1245 | * level is smaller (ie: more urgent) than the previous priority, then note | |
1246 | * that priority level within the zone. This is done so that when the next | |
1247 | * process comes in to scan this zone, it will immediately start out at this | |
1248 | * priority level rather than having to build up its own scanning priority. | |
1249 | * Here, this priority affects only the reclaim-mapped threshold. | |
1250 | */ | |
1251 | static inline void note_zone_scanning_priority(struct zone *zone, int priority) | |
1252 | { | |
1253 | if (priority < zone->prev_priority) | |
1254 | zone->prev_priority = priority; | |
1255 | } | |
1256 | ||
1257 | /* | |
1258 | * This moves pages from the active list to the inactive list. | |
1259 | * | |
1260 | * We move them the other way if the page is referenced by one or more | |
1261 | * processes, from rmap. | |
1262 | * | |
1263 | * If the pages are mostly unmapped, the processing is fast and it is | |
1264 | * appropriate to hold zone->lru_lock across the whole operation. But if | |
1265 | * the pages are mapped, the processing is slow (page_referenced()) so we | |
1266 | * should drop zone->lru_lock around each page. It's impossible to balance | |
1267 | * this, so instead we remove the pages from the LRU while processing them. | |
1268 | * It is safe to rely on PG_active against the non-LRU pages in here because | |
1269 | * nobody will play with that bit on a non-LRU page. | |
1270 | * | |
1271 | * The downside is that we have to touch page->_count against each page. | |
1272 | * But we had to alter page->flags anyway. | |
1273 | */ | |
1274 | ||
1275 | static void move_active_pages_to_lru(struct zone *zone, | |
1276 | struct list_head *list, | |
1277 | enum lru_list lru) | |
1278 | { | |
1279 | unsigned long pgmoved = 0; | |
1280 | struct pagevec pvec; | |
1281 | struct page *page; | |
1282 | ||
1283 | pagevec_init(&pvec, 1); | |
1284 | ||
1285 | while (!list_empty(list)) { | |
1286 | page = lru_to_page(list); | |
1287 | ||
1288 | VM_BUG_ON(PageLRU(page)); | |
1289 | SetPageLRU(page); | |
1290 | ||
1291 | list_move(&page->lru, &zone->lru[lru].list); | |
1292 | mem_cgroup_add_lru_list(page, lru); | |
1293 | pgmoved++; | |
1294 | ||
1295 | if (!pagevec_add(&pvec, page) || list_empty(list)) { | |
1296 | spin_unlock_irq(&zone->lru_lock); | |
1297 | if (buffer_heads_over_limit) | |
1298 | pagevec_strip(&pvec); | |
1299 | __pagevec_release(&pvec); | |
1300 | spin_lock_irq(&zone->lru_lock); | |
1301 | } | |
1302 | } | |
1303 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); | |
1304 | if (!is_active_lru(lru)) | |
1305 | __count_vm_events(PGDEACTIVATE, pgmoved); | |
1306 | } | |
1307 | ||
1308 | static void shrink_active_list(unsigned long nr_pages, struct zone *zone, | |
1309 | struct scan_control *sc, int priority, int file) | |
1310 | { | |
1311 | unsigned long nr_taken; | |
1312 | unsigned long pgscanned; | |
1313 | unsigned long vm_flags; | |
1314 | LIST_HEAD(l_hold); /* The pages which were snipped off */ | |
1315 | LIST_HEAD(l_active); | |
1316 | LIST_HEAD(l_inactive); | |
1317 | struct page *page; | |
1318 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); | |
1319 | unsigned long nr_rotated = 0; | |
1320 | ||
1321 | lru_add_drain(); | |
1322 | spin_lock_irq(&zone->lru_lock); | |
1323 | nr_taken = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order, | |
1324 | ISOLATE_ACTIVE, zone, | |
1325 | sc->mem_cgroup, 1, file); | |
1326 | /* | |
1327 | * zone->pages_scanned is used for detect zone's oom | |
1328 | * mem_cgroup remembers nr_scan by itself. | |
1329 | */ | |
1330 | if (scanning_global_lru(sc)) { | |
1331 | zone->pages_scanned += pgscanned; | |
1332 | } | |
1333 | reclaim_stat->recent_scanned[file] += nr_taken; | |
1334 | ||
1335 | __count_zone_vm_events(PGREFILL, zone, pgscanned); | |
1336 | if (file) | |
1337 | __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); | |
1338 | else | |
1339 | __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); | |
1340 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); | |
1341 | spin_unlock_irq(&zone->lru_lock); | |
1342 | ||
1343 | while (!list_empty(&l_hold)) { | |
1344 | cond_resched(); | |
1345 | page = lru_to_page(&l_hold); | |
1346 | list_del(&page->lru); | |
1347 | ||
1348 | if (unlikely(!page_evictable(page, NULL))) { | |
1349 | putback_lru_page(page); | |
1350 | continue; | |
1351 | } | |
1352 | ||
1353 | /* page_referenced clears PageReferenced */ | |
1354 | if (page_mapping_inuse(page) && | |
1355 | page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { | |
1356 | nr_rotated++; | |
1357 | /* | |
1358 | * Identify referenced, file-backed active pages and | |
1359 | * give them one more trip around the active list. So | |
1360 | * that executable code get better chances to stay in | |
1361 | * memory under moderate memory pressure. Anon pages | |
1362 | * are not likely to be evicted by use-once streaming | |
1363 | * IO, plus JVM can create lots of anon VM_EXEC pages, | |
1364 | * so we ignore them here. | |
1365 | */ | |
1366 | if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { | |
1367 | list_add(&page->lru, &l_active); | |
1368 | continue; | |
1369 | } | |
1370 | } | |
1371 | ||
1372 | ClearPageActive(page); /* we are de-activating */ | |
1373 | list_add(&page->lru, &l_inactive); | |
1374 | } | |
1375 | ||
1376 | /* | |
1377 | * Move pages back to the lru list. | |
1378 | */ | |
1379 | spin_lock_irq(&zone->lru_lock); | |
1380 | /* | |
1381 | * Count referenced pages from currently used mappings as rotated, | |
1382 | * even though only some of them are actually re-activated. This | |
1383 | * helps balance scan pressure between file and anonymous pages in | |
1384 | * get_scan_ratio. | |
1385 | */ | |
1386 | reclaim_stat->recent_rotated[file] += nr_rotated; | |
1387 | ||
1388 | move_active_pages_to_lru(zone, &l_active, | |
1389 | LRU_ACTIVE + file * LRU_FILE); | |
1390 | move_active_pages_to_lru(zone, &l_inactive, | |
1391 | LRU_BASE + file * LRU_FILE); | |
1392 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); | |
1393 | spin_unlock_irq(&zone->lru_lock); | |
1394 | } | |
1395 | ||
1396 | static int inactive_anon_is_low_global(struct zone *zone) | |
1397 | { | |
1398 | unsigned long active, inactive; | |
1399 | ||
1400 | active = zone_page_state(zone, NR_ACTIVE_ANON); | |
1401 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); | |
1402 | ||
1403 | if (inactive * zone->inactive_ratio < active) | |
1404 | return 1; | |
1405 | ||
1406 | return 0; | |
1407 | } | |
1408 | ||
1409 | /** | |
1410 | * inactive_anon_is_low - check if anonymous pages need to be deactivated | |
1411 | * @zone: zone to check | |
1412 | * @sc: scan control of this context | |
1413 | * | |
1414 | * Returns true if the zone does not have enough inactive anon pages, | |
1415 | * meaning some active anon pages need to be deactivated. | |
1416 | */ | |
1417 | static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) | |
1418 | { | |
1419 | int low; | |
1420 | ||
1421 | if (scanning_global_lru(sc)) | |
1422 | low = inactive_anon_is_low_global(zone); | |
1423 | else | |
1424 | low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); | |
1425 | return low; | |
1426 | } | |
1427 | ||
1428 | static int inactive_file_is_low_global(struct zone *zone) | |
1429 | { | |
1430 | unsigned long active, inactive; | |
1431 | ||
1432 | active = zone_page_state(zone, NR_ACTIVE_FILE); | |
1433 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); | |
1434 | ||
1435 | return (active > inactive); | |
1436 | } | |
1437 | ||
1438 | /** | |
1439 | * inactive_file_is_low - check if file pages need to be deactivated | |
1440 | * @zone: zone to check | |
1441 | * @sc: scan control of this context | |
1442 | * | |
1443 | * When the system is doing streaming IO, memory pressure here | |
1444 | * ensures that active file pages get deactivated, until more | |
1445 | * than half of the file pages are on the inactive list. | |
1446 | * | |
1447 | * Once we get to that situation, protect the system's working | |
1448 | * set from being evicted by disabling active file page aging. | |
1449 | * | |
1450 | * This uses a different ratio than the anonymous pages, because | |
1451 | * the page cache uses a use-once replacement algorithm. | |
1452 | */ | |
1453 | static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) | |
1454 | { | |
1455 | int low; | |
1456 | ||
1457 | if (scanning_global_lru(sc)) | |
1458 | low = inactive_file_is_low_global(zone); | |
1459 | else | |
1460 | low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); | |
1461 | return low; | |
1462 | } | |
1463 | ||
1464 | static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, | |
1465 | int file) | |
1466 | { | |
1467 | if (file) | |
1468 | return inactive_file_is_low(zone, sc); | |
1469 | else | |
1470 | return inactive_anon_is_low(zone, sc); | |
1471 | } | |
1472 | ||
1473 | static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, | |
1474 | struct zone *zone, struct scan_control *sc, int priority) | |
1475 | { | |
1476 | int file = is_file_lru(lru); | |
1477 | ||
1478 | if (is_active_lru(lru)) { | |
1479 | if (inactive_list_is_low(zone, sc, file)) | |
1480 | shrink_active_list(nr_to_scan, zone, sc, priority, file); | |
1481 | return 0; | |
1482 | } | |
1483 | ||
1484 | return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); | |
1485 | } | |
1486 | ||
1487 | /* | |
1488 | * Determine how aggressively the anon and file LRU lists should be | |
1489 | * scanned. The relative value of each set of LRU lists is determined | |
1490 | * by looking at the fraction of the pages scanned we did rotate back | |
1491 | * onto the active list instead of evict. | |
1492 | * | |
1493 | * percent[0] specifies how much pressure to put on ram/swap backed | |
1494 | * memory, while percent[1] determines pressure on the file LRUs. | |
1495 | */ | |
1496 | static void get_scan_ratio(struct zone *zone, struct scan_control *sc, | |
1497 | unsigned long *percent) | |
1498 | { | |
1499 | unsigned long anon, file, free; | |
1500 | unsigned long anon_prio, file_prio; | |
1501 | unsigned long ap, fp; | |
1502 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); | |
1503 | ||
1504 | anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + | |
1505 | zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); | |
1506 | file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + | |
1507 | zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); | |
1508 | ||
1509 | if (scanning_global_lru(sc)) { | |
1510 | free = zone_page_state(zone, NR_FREE_PAGES); | |
1511 | /* If we have very few page cache pages, | |
1512 | force-scan anon pages. */ | |
1513 | if (unlikely(file + free <= high_wmark_pages(zone))) { | |
1514 | percent[0] = 100; | |
1515 | percent[1] = 0; | |
1516 | return; | |
1517 | } | |
1518 | } | |
1519 | ||
1520 | /* | |
1521 | * OK, so we have swap space and a fair amount of page cache | |
1522 | * pages. We use the recently rotated / recently scanned | |
1523 | * ratios to determine how valuable each cache is. | |
1524 | * | |
1525 | * Because workloads change over time (and to avoid overflow) | |
1526 | * we keep these statistics as a floating average, which ends | |
1527 | * up weighing recent references more than old ones. | |
1528 | * | |
1529 | * anon in [0], file in [1] | |
1530 | */ | |
1531 | if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { | |
1532 | spin_lock_irq(&zone->lru_lock); | |
1533 | reclaim_stat->recent_scanned[0] /= 2; | |
1534 | reclaim_stat->recent_rotated[0] /= 2; | |
1535 | spin_unlock_irq(&zone->lru_lock); | |
1536 | } | |
1537 | ||
1538 | if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { | |
1539 | spin_lock_irq(&zone->lru_lock); | |
1540 | reclaim_stat->recent_scanned[1] /= 2; | |
1541 | reclaim_stat->recent_rotated[1] /= 2; | |
1542 | spin_unlock_irq(&zone->lru_lock); | |
1543 | } | |
1544 | ||
1545 | /* | |
1546 | * With swappiness at 100, anonymous and file have the same priority. | |
1547 | * This scanning priority is essentially the inverse of IO cost. | |
1548 | */ | |
1549 | anon_prio = sc->swappiness; | |
1550 | file_prio = 200 - sc->swappiness; | |
1551 | ||
1552 | /* | |
1553 | * The amount of pressure on anon vs file pages is inversely | |
1554 | * proportional to the fraction of recently scanned pages on | |
1555 | * each list that were recently referenced and in active use. | |
1556 | */ | |
1557 | ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); | |
1558 | ap /= reclaim_stat->recent_rotated[0] + 1; | |
1559 | ||
1560 | fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); | |
1561 | fp /= reclaim_stat->recent_rotated[1] + 1; | |
1562 | ||
1563 | /* Normalize to percentages */ | |
1564 | percent[0] = 100 * ap / (ap + fp + 1); | |
1565 | percent[1] = 100 - percent[0]; | |
1566 | } | |
1567 | ||
1568 | /* | |
1569 | * Smallish @nr_to_scan's are deposited in @nr_saved_scan, | |
1570 | * until we collected @swap_cluster_max pages to scan. | |
1571 | */ | |
1572 | static unsigned long nr_scan_try_batch(unsigned long nr_to_scan, | |
1573 | unsigned long *nr_saved_scan) | |
1574 | { | |
1575 | unsigned long nr; | |
1576 | ||
1577 | *nr_saved_scan += nr_to_scan; | |
1578 | nr = *nr_saved_scan; | |
1579 | ||
1580 | if (nr >= SWAP_CLUSTER_MAX) | |
1581 | *nr_saved_scan = 0; | |
1582 | else | |
1583 | nr = 0; | |
1584 | ||
1585 | return nr; | |
1586 | } | |
1587 | ||
1588 | /* | |
1589 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. | |
1590 | */ | |
1591 | static void shrink_zone(int priority, struct zone *zone, | |
1592 | struct scan_control *sc) | |
1593 | { | |
1594 | unsigned long nr[NR_LRU_LISTS]; | |
1595 | unsigned long nr_to_scan; | |
1596 | unsigned long percent[2]; /* anon @ 0; file @ 1 */ | |
1597 | enum lru_list l; | |
1598 | unsigned long nr_reclaimed = sc->nr_reclaimed; | |
1599 | unsigned long nr_to_reclaim = sc->nr_to_reclaim; | |
1600 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); | |
1601 | int noswap = 0; | |
1602 | ||
1603 | /* If we have no swap space, do not bother scanning anon pages. */ | |
1604 | if (!sc->may_swap || (nr_swap_pages <= 0)) { | |
1605 | noswap = 1; | |
1606 | percent[0] = 0; | |
1607 | percent[1] = 100; | |
1608 | } else | |
1609 | get_scan_ratio(zone, sc, percent); | |
1610 | ||
1611 | for_each_evictable_lru(l) { | |
1612 | int file = is_file_lru(l); | |
1613 | unsigned long scan; | |
1614 | ||
1615 | scan = zone_nr_lru_pages(zone, sc, l); | |
1616 | if (priority || noswap) { | |
1617 | scan >>= priority; | |
1618 | scan = (scan * percent[file]) / 100; | |
1619 | } | |
1620 | nr[l] = nr_scan_try_batch(scan, | |
1621 | &reclaim_stat->nr_saved_scan[l]); | |
1622 | } | |
1623 | ||
1624 | while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || | |
1625 | nr[LRU_INACTIVE_FILE]) { | |
1626 | for_each_evictable_lru(l) { | |
1627 | if (nr[l]) { | |
1628 | nr_to_scan = min_t(unsigned long, | |
1629 | nr[l], SWAP_CLUSTER_MAX); | |
1630 | nr[l] -= nr_to_scan; | |
1631 | ||
1632 | nr_reclaimed += shrink_list(l, nr_to_scan, | |
1633 | zone, sc, priority); | |
1634 | } | |
1635 | } | |
1636 | /* | |
1637 | * On large memory systems, scan >> priority can become | |
1638 | * really large. This is fine for the starting priority; | |
1639 | * we want to put equal scanning pressure on each zone. | |
1640 | * However, if the VM has a harder time of freeing pages, | |
1641 | * with multiple processes reclaiming pages, the total | |
1642 | * freeing target can get unreasonably large. | |
1643 | */ | |
1644 | if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) | |
1645 | break; | |
1646 | } | |
1647 | ||
1648 | sc->nr_reclaimed = nr_reclaimed; | |
1649 | ||
1650 | /* | |
1651 | * Even if we did not try to evict anon pages at all, we want to | |
1652 | * rebalance the anon lru active/inactive ratio. | |
1653 | */ | |
1654 | if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0) | |
1655 | shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); | |
1656 | ||
1657 | throttle_vm_writeout(sc->gfp_mask); | |
1658 | } | |
1659 | ||
1660 | /* | |
1661 | * This is the direct reclaim path, for page-allocating processes. We only | |
1662 | * try to reclaim pages from zones which will satisfy the caller's allocation | |
1663 | * request. | |
1664 | * | |
1665 | * We reclaim from a zone even if that zone is over high_wmark_pages(zone). | |
1666 | * Because: | |
1667 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order | |
1668 | * allocation or | |
1669 | * b) The target zone may be at high_wmark_pages(zone) but the lower zones | |
1670 | * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' | |
1671 | * zone defense algorithm. | |
1672 | * | |
1673 | * If a zone is deemed to be full of pinned pages then just give it a light | |
1674 | * scan then give up on it. | |
1675 | */ | |
1676 | static void shrink_zones(int priority, struct zonelist *zonelist, | |
1677 | struct scan_control *sc) | |
1678 | { | |
1679 | enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask); | |
1680 | struct zoneref *z; | |
1681 | struct zone *zone; | |
1682 | ||
1683 | sc->all_unreclaimable = 1; | |
1684 | for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx, | |
1685 | sc->nodemask) { | |
1686 | if (!populated_zone(zone)) | |
1687 | continue; | |
1688 | /* | |
1689 | * Take care memory controller reclaiming has small influence | |
1690 | * to global LRU. | |
1691 | */ | |
1692 | if (scanning_global_lru(sc)) { | |
1693 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) | |
1694 | continue; | |
1695 | note_zone_scanning_priority(zone, priority); | |
1696 | ||
1697 | if (zone_is_all_unreclaimable(zone) && | |
1698 | priority != DEF_PRIORITY) | |
1699 | continue; /* Let kswapd poll it */ | |
1700 | sc->all_unreclaimable = 0; | |
1701 | } else { | |
1702 | /* | |
1703 | * Ignore cpuset limitation here. We just want to reduce | |
1704 | * # of used pages by us regardless of memory shortage. | |
1705 | */ | |
1706 | sc->all_unreclaimable = 0; | |
1707 | mem_cgroup_note_reclaim_priority(sc->mem_cgroup, | |
1708 | priority); | |
1709 | } | |
1710 | ||
1711 | shrink_zone(priority, zone, sc); | |
1712 | } | |
1713 | } | |
1714 | ||
1715 | /* | |
1716 | * This is the main entry point to direct page reclaim. | |
1717 | * | |
1718 | * If a full scan of the inactive list fails to free enough memory then we | |
1719 | * are "out of memory" and something needs to be killed. | |
1720 | * | |
1721 | * If the caller is !__GFP_FS then the probability of a failure is reasonably | |
1722 | * high - the zone may be full of dirty or under-writeback pages, which this | |
1723 | * caller can't do much about. We kick the writeback threads and take explicit | |
1724 | * naps in the hope that some of these pages can be written. But if the | |
1725 | * allocating task holds filesystem locks which prevent writeout this might not | |
1726 | * work, and the allocation attempt will fail. | |
1727 | * | |
1728 | * returns: 0, if no pages reclaimed | |
1729 | * else, the number of pages reclaimed | |
1730 | */ | |
1731 | static unsigned long do_try_to_free_pages(struct zonelist *zonelist, | |
1732 | struct scan_control *sc) | |
1733 | { | |
1734 | int priority; | |
1735 | unsigned long ret = 0; | |
1736 | unsigned long total_scanned = 0; | |
1737 | struct reclaim_state *reclaim_state = current->reclaim_state; | |
1738 | unsigned long lru_pages = 0; | |
1739 | struct zoneref *z; | |
1740 | struct zone *zone; | |
1741 | enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask); | |
1742 | unsigned long writeback_threshold; | |
1743 | ||
1744 | delayacct_freepages_start(); | |
1745 | ||
1746 | if (scanning_global_lru(sc)) | |
1747 | count_vm_event(ALLOCSTALL); | |
1748 | /* | |
1749 | * mem_cgroup will not do shrink_slab. | |
1750 | */ | |
1751 | if (scanning_global_lru(sc)) { | |
1752 | for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) { | |
1753 | ||
1754 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) | |
1755 | continue; | |
1756 | ||
1757 | lru_pages += zone_reclaimable_pages(zone); | |
1758 | } | |
1759 | } | |
1760 | ||
1761 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { | |
1762 | sc->nr_scanned = 0; | |
1763 | if (!priority) | |
1764 | disable_swap_token(); | |
1765 | shrink_zones(priority, zonelist, sc); | |
1766 | /* | |
1767 | * Don't shrink slabs when reclaiming memory from | |
1768 | * over limit cgroups | |
1769 | */ | |
1770 | if (scanning_global_lru(sc)) { | |
1771 | shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages); | |
1772 | if (reclaim_state) { | |
1773 | sc->nr_reclaimed += reclaim_state->reclaimed_slab; | |
1774 | reclaim_state->reclaimed_slab = 0; | |
1775 | } | |
1776 | } | |
1777 | total_scanned += sc->nr_scanned; | |
1778 | if (sc->nr_reclaimed >= sc->nr_to_reclaim) { | |
1779 | ret = sc->nr_reclaimed; | |
1780 | goto out; | |
1781 | } | |
1782 | ||
1783 | /* | |
1784 | * Try to write back as many pages as we just scanned. This | |
1785 | * tends to cause slow streaming writers to write data to the | |
1786 | * disk smoothly, at the dirtying rate, which is nice. But | |
1787 | * that's undesirable in laptop mode, where we *want* lumpy | |
1788 | * writeout. So in laptop mode, write out the whole world. | |
1789 | */ | |
1790 | writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; | |
1791 | if (total_scanned > writeback_threshold) { | |
1792 | wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); | |
1793 | sc->may_writepage = 1; | |
1794 | } | |
1795 | ||
1796 | /* Take a nap, wait for some writeback to complete */ | |
1797 | if (!sc->hibernation_mode && sc->nr_scanned && | |
1798 | priority < DEF_PRIORITY - 2) | |
1799 | congestion_wait(BLK_RW_ASYNC, HZ/10); | |
1800 | } | |
1801 | /* top priority shrink_zones still had more to do? don't OOM, then */ | |
1802 | if (!sc->all_unreclaimable && scanning_global_lru(sc)) | |
1803 | ret = sc->nr_reclaimed; | |
1804 | out: | |
1805 | /* | |
1806 | * Now that we've scanned all the zones at this priority level, note | |
1807 | * that level within the zone so that the next thread which performs | |
1808 | * scanning of this zone will immediately start out at this priority | |
1809 | * level. This affects only the decision whether or not to bring | |
1810 | * mapped pages onto the inactive list. | |
1811 | */ | |
1812 | if (priority < 0) | |
1813 | priority = 0; | |
1814 | ||
1815 | if (scanning_global_lru(sc)) { | |
1816 | for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) { | |
1817 | ||
1818 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) | |
1819 | continue; | |
1820 | ||
1821 | zone->prev_priority = priority; | |
1822 | } | |
1823 | } else | |
1824 | mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority); | |
1825 | ||
1826 | delayacct_freepages_end(); | |
1827 | ||
1828 | return ret; | |
1829 | } | |
1830 | ||
1831 | unsigned long try_to_free_pages(struct zonelist *zonelist, int order, | |
1832 | gfp_t gfp_mask, nodemask_t *nodemask) | |
1833 | { | |
1834 | struct scan_control sc = { | |
1835 | .gfp_mask = gfp_mask, | |
1836 | .may_writepage = !laptop_mode, | |
1837 | .nr_to_reclaim = SWAP_CLUSTER_MAX, | |
1838 | .may_unmap = 1, | |
1839 | .may_swap = 1, | |
1840 | .swappiness = vm_swappiness, | |
1841 | .order = order, | |
1842 | .mem_cgroup = NULL, | |
1843 | .isolate_pages = isolate_pages_global, | |
1844 | .nodemask = nodemask, | |
1845 | }; | |
1846 | ||
1847 | return do_try_to_free_pages(zonelist, &sc); | |
1848 | } | |
1849 | ||
1850 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR | |
1851 | ||
1852 | unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, | |
1853 | gfp_t gfp_mask, bool noswap, | |
1854 | unsigned int swappiness, | |
1855 | struct zone *zone, int nid) | |
1856 | { | |
1857 | struct scan_control sc = { | |
1858 | .may_writepage = !laptop_mode, | |
1859 | .may_unmap = 1, | |
1860 | .may_swap = !noswap, | |
1861 | .swappiness = swappiness, | |
1862 | .order = 0, | |
1863 | .mem_cgroup = mem, | |
1864 | .isolate_pages = mem_cgroup_isolate_pages, | |
1865 | }; | |
1866 | nodemask_t nm = nodemask_of_node(nid); | |
1867 | ||
1868 | sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | | |
1869 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); | |
1870 | sc.nodemask = &nm; | |
1871 | sc.nr_reclaimed = 0; | |
1872 | sc.nr_scanned = 0; | |
1873 | /* | |
1874 | * NOTE: Although we can get the priority field, using it | |
1875 | * here is not a good idea, since it limits the pages we can scan. | |
1876 | * if we don't reclaim here, the shrink_zone from balance_pgdat | |
1877 | * will pick up pages from other mem cgroup's as well. We hack | |
1878 | * the priority and make it zero. | |
1879 | */ | |
1880 | shrink_zone(0, zone, &sc); | |
1881 | return sc.nr_reclaimed; | |
1882 | } | |
1883 | ||
1884 | unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, | |
1885 | gfp_t gfp_mask, | |
1886 | bool noswap, | |
1887 | unsigned int swappiness) | |
1888 | { | |
1889 | struct zonelist *zonelist; | |
1890 | struct scan_control sc = { | |
1891 | .may_writepage = !laptop_mode, | |
1892 | .may_unmap = 1, | |
1893 | .may_swap = !noswap, | |
1894 | .nr_to_reclaim = SWAP_CLUSTER_MAX, | |
1895 | .swappiness = swappiness, | |
1896 | .order = 0, | |
1897 | .mem_cgroup = mem_cont, | |
1898 | .isolate_pages = mem_cgroup_isolate_pages, | |
1899 | .nodemask = NULL, /* we don't care the placement */ | |
1900 | }; | |
1901 | ||
1902 | sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | | |
1903 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); | |
1904 | zonelist = NODE_DATA(numa_node_id())->node_zonelists; | |
1905 | return do_try_to_free_pages(zonelist, &sc); | |
1906 | } | |
1907 | #endif | |
1908 | ||
1909 | /* is kswapd sleeping prematurely? */ | |
1910 | static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining) | |
1911 | { | |
1912 | int i; | |
1913 | ||
1914 | /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ | |
1915 | if (remaining) | |
1916 | return 1; | |
1917 | ||
1918 | /* If after HZ/10, a zone is below the high mark, it's premature */ | |
1919 | for (i = 0; i < pgdat->nr_zones; i++) { | |
1920 | struct zone *zone = pgdat->node_zones + i; | |
1921 | ||
1922 | if (!populated_zone(zone)) | |
1923 | continue; | |
1924 | ||
1925 | if (zone_is_all_unreclaimable(zone)) | |
1926 | continue; | |
1927 | ||
1928 | if (!zone_watermark_ok(zone, order, high_wmark_pages(zone), | |
1929 | 0, 0)) | |
1930 | return 1; | |
1931 | } | |
1932 | ||
1933 | return 0; | |
1934 | } | |
1935 | ||
1936 | /* | |
1937 | * For kswapd, balance_pgdat() will work across all this node's zones until | |
1938 | * they are all at high_wmark_pages(zone). | |
1939 | * | |
1940 | * Returns the number of pages which were actually freed. | |
1941 | * | |
1942 | * There is special handling here for zones which are full of pinned pages. | |
1943 | * This can happen if the pages are all mlocked, or if they are all used by | |
1944 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. | |
1945 | * What we do is to detect the case where all pages in the zone have been | |
1946 | * scanned twice and there has been zero successful reclaim. Mark the zone as | |
1947 | * dead and from now on, only perform a short scan. Basically we're polling | |
1948 | * the zone for when the problem goes away. | |
1949 | * | |
1950 | * kswapd scans the zones in the highmem->normal->dma direction. It skips | |
1951 | * zones which have free_pages > high_wmark_pages(zone), but once a zone is | |
1952 | * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the | |
1953 | * lower zones regardless of the number of free pages in the lower zones. This | |
1954 | * interoperates with the page allocator fallback scheme to ensure that aging | |
1955 | * of pages is balanced across the zones. | |
1956 | */ | |
1957 | static unsigned long balance_pgdat(pg_data_t *pgdat, int order) | |
1958 | { | |
1959 | int all_zones_ok; | |
1960 | int priority; | |
1961 | int i; | |
1962 | unsigned long total_scanned; | |
1963 | struct reclaim_state *reclaim_state = current->reclaim_state; | |
1964 | struct scan_control sc = { | |
1965 | .gfp_mask = GFP_KERNEL, | |
1966 | .may_unmap = 1, | |
1967 | .may_swap = 1, | |
1968 | /* | |
1969 | * kswapd doesn't want to be bailed out while reclaim. because | |
1970 | * we want to put equal scanning pressure on each zone. | |
1971 | */ | |
1972 | .nr_to_reclaim = ULONG_MAX, | |
1973 | .swappiness = vm_swappiness, | |
1974 | .order = order, | |
1975 | .mem_cgroup = NULL, | |
1976 | .isolate_pages = isolate_pages_global, | |
1977 | }; | |
1978 | /* | |
1979 | * temp_priority is used to remember the scanning priority at which | |
1980 | * this zone was successfully refilled to | |
1981 | * free_pages == high_wmark_pages(zone). | |
1982 | */ | |
1983 | int temp_priority[MAX_NR_ZONES]; | |
1984 | ||
1985 | loop_again: | |
1986 | total_scanned = 0; | |
1987 | sc.nr_reclaimed = 0; | |
1988 | sc.may_writepage = !laptop_mode; | |
1989 | count_vm_event(PAGEOUTRUN); | |
1990 | ||
1991 | for (i = 0; i < pgdat->nr_zones; i++) | |
1992 | temp_priority[i] = DEF_PRIORITY; | |
1993 | ||
1994 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { | |
1995 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ | |
1996 | unsigned long lru_pages = 0; | |
1997 | int has_under_min_watermark_zone = 0; | |
1998 | ||
1999 | /* The swap token gets in the way of swapout... */ | |
2000 | if (!priority) | |
2001 | disable_swap_token(); | |
2002 | ||
2003 | all_zones_ok = 1; | |
2004 | ||
2005 | /* | |
2006 | * Scan in the highmem->dma direction for the highest | |
2007 | * zone which needs scanning | |
2008 | */ | |
2009 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { | |
2010 | struct zone *zone = pgdat->node_zones + i; | |
2011 | ||
2012 | if (!populated_zone(zone)) | |
2013 | continue; | |
2014 | ||
2015 | if (zone_is_all_unreclaimable(zone) && | |
2016 | priority != DEF_PRIORITY) | |
2017 | continue; | |
2018 | ||
2019 | /* | |
2020 | * Do some background aging of the anon list, to give | |
2021 | * pages a chance to be referenced before reclaiming. | |
2022 | */ | |
2023 | if (inactive_anon_is_low(zone, &sc)) | |
2024 | shrink_active_list(SWAP_CLUSTER_MAX, zone, | |
2025 | &sc, priority, 0); | |
2026 | ||
2027 | if (!zone_watermark_ok(zone, order, | |
2028 | high_wmark_pages(zone), 0, 0)) { | |
2029 | end_zone = i; | |
2030 | break; | |
2031 | } | |
2032 | } | |
2033 | if (i < 0) | |
2034 | goto out; | |
2035 | ||
2036 | for (i = 0; i <= end_zone; i++) { | |
2037 | struct zone *zone = pgdat->node_zones + i; | |
2038 | ||
2039 | lru_pages += zone_reclaimable_pages(zone); | |
2040 | } | |
2041 | ||
2042 | /* | |
2043 | * Now scan the zone in the dma->highmem direction, stopping | |
2044 | * at the last zone which needs scanning. | |
2045 | * | |
2046 | * We do this because the page allocator works in the opposite | |
2047 | * direction. This prevents the page allocator from allocating | |
2048 | * pages behind kswapd's direction of progress, which would | |
2049 | * cause too much scanning of the lower zones. | |
2050 | */ | |
2051 | for (i = 0; i <= end_zone; i++) { | |
2052 | struct zone *zone = pgdat->node_zones + i; | |
2053 | int nr_slab; | |
2054 | int nid, zid; | |
2055 | ||
2056 | if (!populated_zone(zone)) | |
2057 | continue; | |
2058 | ||
2059 | if (zone_is_all_unreclaimable(zone) && | |
2060 | priority != DEF_PRIORITY) | |
2061 | continue; | |
2062 | ||
2063 | if (!zone_watermark_ok(zone, order, | |
2064 | high_wmark_pages(zone), end_zone, 0)) | |
2065 | all_zones_ok = 0; | |
2066 | temp_priority[i] = priority; | |
2067 | sc.nr_scanned = 0; | |
2068 | note_zone_scanning_priority(zone, priority); | |
2069 | ||
2070 | nid = pgdat->node_id; | |
2071 | zid = zone_idx(zone); | |
2072 | /* | |
2073 | * Call soft limit reclaim before calling shrink_zone. | |
2074 | * For now we ignore the return value | |
2075 | */ | |
2076 | mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask, | |
2077 | nid, zid); | |
2078 | /* | |
2079 | * We put equal pressure on every zone, unless one | |
2080 | * zone has way too many pages free already. | |
2081 | */ | |
2082 | if (!zone_watermark_ok(zone, order, | |
2083 | 8*high_wmark_pages(zone), end_zone, 0)) | |
2084 | shrink_zone(priority, zone, &sc); | |
2085 | reclaim_state->reclaimed_slab = 0; | |
2086 | nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, | |
2087 | lru_pages); | |
2088 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; | |
2089 | total_scanned += sc.nr_scanned; | |
2090 | if (zone_is_all_unreclaimable(zone)) | |
2091 | continue; | |
2092 | if (nr_slab == 0 && zone->pages_scanned >= | |
2093 | (zone_reclaimable_pages(zone) * 6)) | |
2094 | zone_set_flag(zone, | |
2095 | ZONE_ALL_UNRECLAIMABLE); | |
2096 | /* | |
2097 | * If we've done a decent amount of scanning and | |
2098 | * the reclaim ratio is low, start doing writepage | |
2099 | * even in laptop mode | |
2100 | */ | |
2101 | if (total_scanned > SWAP_CLUSTER_MAX * 2 && | |
2102 | total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) | |
2103 | sc.may_writepage = 1; | |
2104 | ||
2105 | /* | |
2106 | * We are still under min water mark. it mean we have | |
2107 | * GFP_ATOMIC allocation failure risk. Hurry up! | |
2108 | */ | |
2109 | if (!zone_watermark_ok(zone, order, min_wmark_pages(zone), | |
2110 | end_zone, 0)) | |
2111 | has_under_min_watermark_zone = 1; | |
2112 | ||
2113 | } | |
2114 | if (all_zones_ok) | |
2115 | break; /* kswapd: all done */ | |
2116 | /* | |
2117 | * OK, kswapd is getting into trouble. Take a nap, then take | |
2118 | * another pass across the zones. | |
2119 | */ | |
2120 | if (total_scanned && (priority < DEF_PRIORITY - 2)) { | |
2121 | if (has_under_min_watermark_zone) | |
2122 | count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); | |
2123 | else | |
2124 | congestion_wait(BLK_RW_ASYNC, HZ/10); | |
2125 | } | |
2126 | ||
2127 | /* | |
2128 | * We do this so kswapd doesn't build up large priorities for | |
2129 | * example when it is freeing in parallel with allocators. It | |
2130 | * matches the direct reclaim path behaviour in terms of impact | |
2131 | * on zone->*_priority. | |
2132 | */ | |
2133 | if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) | |
2134 | break; | |
2135 | } | |
2136 | out: | |
2137 | /* | |
2138 | * Note within each zone the priority level at which this zone was | |
2139 | * brought into a happy state. So that the next thread which scans this | |
2140 | * zone will start out at that priority level. | |
2141 | */ | |
2142 | for (i = 0; i < pgdat->nr_zones; i++) { | |
2143 | struct zone *zone = pgdat->node_zones + i; | |
2144 | ||
2145 | zone->prev_priority = temp_priority[i]; | |
2146 | } | |
2147 | if (!all_zones_ok) { | |
2148 | cond_resched(); | |
2149 | ||
2150 | try_to_freeze(); | |
2151 | ||
2152 | /* | |
2153 | * Fragmentation may mean that the system cannot be | |
2154 | * rebalanced for high-order allocations in all zones. | |
2155 | * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, | |
2156 | * it means the zones have been fully scanned and are still | |
2157 | * not balanced. For high-order allocations, there is | |
2158 | * little point trying all over again as kswapd may | |
2159 | * infinite loop. | |
2160 | * | |
2161 | * Instead, recheck all watermarks at order-0 as they | |
2162 | * are the most important. If watermarks are ok, kswapd will go | |
2163 | * back to sleep. High-order users can still perform direct | |
2164 | * reclaim if they wish. | |
2165 | */ | |
2166 | if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) | |
2167 | order = sc.order = 0; | |
2168 | ||
2169 | goto loop_again; | |
2170 | } | |
2171 | ||
2172 | return sc.nr_reclaimed; | |
2173 | } | |
2174 | ||
2175 | /* | |
2176 | * The background pageout daemon, started as a kernel thread | |
2177 | * from the init process. | |
2178 | * | |
2179 | * This basically trickles out pages so that we have _some_ | |
2180 | * free memory available even if there is no other activity | |
2181 | * that frees anything up. This is needed for things like routing | |
2182 | * etc, where we otherwise might have all activity going on in | |
2183 | * asynchronous contexts that cannot page things out. | |
2184 | * | |
2185 | * If there are applications that are active memory-allocators | |
2186 | * (most normal use), this basically shouldn't matter. | |
2187 | */ | |
2188 | static int kswapd(void *p) | |
2189 | { | |
2190 | unsigned long order; | |
2191 | pg_data_t *pgdat = (pg_data_t*)p; | |
2192 | struct task_struct *tsk = current; | |
2193 | DEFINE_WAIT(wait); | |
2194 | struct reclaim_state reclaim_state = { | |
2195 | .reclaimed_slab = 0, | |
2196 | }; | |
2197 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); | |
2198 | ||
2199 | lockdep_set_current_reclaim_state(GFP_KERNEL); | |
2200 | ||
2201 | if (!cpumask_empty(cpumask)) | |
2202 | set_cpus_allowed_ptr(tsk, cpumask); | |
2203 | current->reclaim_state = &reclaim_state; | |
2204 | ||
2205 | /* | |
2206 | * Tell the memory management that we're a "memory allocator", | |
2207 | * and that if we need more memory we should get access to it | |
2208 | * regardless (see "__alloc_pages()"). "kswapd" should | |
2209 | * never get caught in the normal page freeing logic. | |
2210 | * | |
2211 | * (Kswapd normally doesn't need memory anyway, but sometimes | |
2212 | * you need a small amount of memory in order to be able to | |
2213 | * page out something else, and this flag essentially protects | |
2214 | * us from recursively trying to free more memory as we're | |
2215 | * trying to free the first piece of memory in the first place). | |
2216 | */ | |
2217 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; | |
2218 | set_freezable(); | |
2219 | ||
2220 | order = 0; | |
2221 | for ( ; ; ) { | |
2222 | unsigned long new_order; | |
2223 | int ret; | |
2224 | ||
2225 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); | |
2226 | new_order = pgdat->kswapd_max_order; | |
2227 | pgdat->kswapd_max_order = 0; | |
2228 | if (order < new_order) { | |
2229 | /* | |
2230 | * Don't sleep if someone wants a larger 'order' | |
2231 | * allocation | |
2232 | */ | |
2233 | order = new_order; | |
2234 | } else { | |
2235 | if (!freezing(current) && !kthread_should_stop()) { | |
2236 | long remaining = 0; | |
2237 | ||
2238 | /* Try to sleep for a short interval */ | |
2239 | if (!sleeping_prematurely(pgdat, order, remaining)) { | |
2240 | remaining = schedule_timeout(HZ/10); | |
2241 | finish_wait(&pgdat->kswapd_wait, &wait); | |
2242 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); | |
2243 | } | |
2244 | ||
2245 | /* | |
2246 | * After a short sleep, check if it was a | |
2247 | * premature sleep. If not, then go fully | |
2248 | * to sleep until explicitly woken up | |
2249 | */ | |
2250 | if (!sleeping_prematurely(pgdat, order, remaining)) | |
2251 | schedule(); | |
2252 | else { | |
2253 | if (remaining) | |
2254 | count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); | |
2255 | else | |
2256 | count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); | |
2257 | } | |
2258 | } | |
2259 | ||
2260 | order = pgdat->kswapd_max_order; | |
2261 | } | |
2262 | finish_wait(&pgdat->kswapd_wait, &wait); | |
2263 | ||
2264 | ret = try_to_freeze(); | |
2265 | if (kthread_should_stop()) | |
2266 | break; | |
2267 | ||
2268 | /* | |
2269 | * We can speed up thawing tasks if we don't call balance_pgdat | |
2270 | * after returning from the refrigerator | |
2271 | */ | |
2272 | if (!ret) | |
2273 | balance_pgdat(pgdat, order); | |
2274 | } | |
2275 | return 0; | |
2276 | } | |
2277 | ||
2278 | /* | |
2279 | * A zone is low on free memory, so wake its kswapd task to service it. | |
2280 | */ | |
2281 | void wakeup_kswapd(struct zone *zone, int order) | |
2282 | { | |
2283 | pg_data_t *pgdat; | |
2284 | ||
2285 | if (!populated_zone(zone)) | |
2286 | return; | |
2287 | ||
2288 | pgdat = zone->zone_pgdat; | |
2289 | if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0)) | |
2290 | return; | |
2291 | if (pgdat->kswapd_max_order < order) | |
2292 | pgdat->kswapd_max_order = order; | |
2293 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) | |
2294 | return; | |
2295 | if (!waitqueue_active(&pgdat->kswapd_wait)) | |
2296 | return; | |
2297 | wake_up_interruptible(&pgdat->kswapd_wait); | |
2298 | } | |
2299 | ||
2300 | /* | |
2301 | * The reclaimable count would be mostly accurate. | |
2302 | * The less reclaimable pages may be | |
2303 | * - mlocked pages, which will be moved to unevictable list when encountered | |
2304 | * - mapped pages, which may require several travels to be reclaimed | |
2305 | * - dirty pages, which is not "instantly" reclaimable | |
2306 | */ | |
2307 | unsigned long global_reclaimable_pages(void) | |
2308 | { | |
2309 | int nr; | |
2310 | ||
2311 | nr = global_page_state(NR_ACTIVE_FILE) + | |
2312 | global_page_state(NR_INACTIVE_FILE); | |
2313 | ||
2314 | if (nr_swap_pages > 0) | |
2315 | nr += global_page_state(NR_ACTIVE_ANON) + | |
2316 | global_page_state(NR_INACTIVE_ANON); | |
2317 | ||
2318 | return nr; | |
2319 | } | |
2320 | ||
2321 | unsigned long zone_reclaimable_pages(struct zone *zone) | |
2322 | { | |
2323 | int nr; | |
2324 | ||
2325 | nr = zone_page_state(zone, NR_ACTIVE_FILE) + | |
2326 | zone_page_state(zone, NR_INACTIVE_FILE); | |
2327 | ||
2328 | if (nr_swap_pages > 0) | |
2329 | nr += zone_page_state(zone, NR_ACTIVE_ANON) + | |
2330 | zone_page_state(zone, NR_INACTIVE_ANON); | |
2331 | ||
2332 | return nr; | |
2333 | } | |
2334 | ||
2335 | #ifdef CONFIG_HIBERNATION | |
2336 | /* | |
2337 | * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of | |
2338 | * freed pages. | |
2339 | * | |
2340 | * Rather than trying to age LRUs the aim is to preserve the overall | |
2341 | * LRU order by reclaiming preferentially | |
2342 | * inactive > active > active referenced > active mapped | |
2343 | */ | |
2344 | unsigned long shrink_all_memory(unsigned long nr_to_reclaim) | |
2345 | { | |
2346 | struct reclaim_state reclaim_state; | |
2347 | struct scan_control sc = { | |
2348 | .gfp_mask = GFP_HIGHUSER_MOVABLE, | |
2349 | .may_swap = 1, | |
2350 | .may_unmap = 1, | |
2351 | .may_writepage = 1, | |
2352 | .nr_to_reclaim = nr_to_reclaim, | |
2353 | .hibernation_mode = 1, | |
2354 | .swappiness = vm_swappiness, | |
2355 | .order = 0, | |
2356 | .isolate_pages = isolate_pages_global, | |
2357 | }; | |
2358 | struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); | |
2359 | struct task_struct *p = current; | |
2360 | unsigned long nr_reclaimed; | |
2361 | ||
2362 | p->flags |= PF_MEMALLOC; | |
2363 | lockdep_set_current_reclaim_state(sc.gfp_mask); | |
2364 | reclaim_state.reclaimed_slab = 0; | |
2365 | p->reclaim_state = &reclaim_state; | |
2366 | ||
2367 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc); | |
2368 | ||
2369 | p->reclaim_state = NULL; | |
2370 | lockdep_clear_current_reclaim_state(); | |
2371 | p->flags &= ~PF_MEMALLOC; | |
2372 | ||
2373 | return nr_reclaimed; | |
2374 | } | |
2375 | #endif /* CONFIG_HIBERNATION */ | |
2376 | ||
2377 | /* It's optimal to keep kswapds on the same CPUs as their memory, but | |
2378 | not required for correctness. So if the last cpu in a node goes | |
2379 | away, we get changed to run anywhere: as the first one comes back, | |
2380 | restore their cpu bindings. */ | |
2381 | static int __devinit cpu_callback(struct notifier_block *nfb, | |
2382 | unsigned long action, void *hcpu) | |
2383 | { | |
2384 | int nid; | |
2385 | ||
2386 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { | |
2387 | for_each_node_state(nid, N_HIGH_MEMORY) { | |
2388 | pg_data_t *pgdat = NODE_DATA(nid); | |
2389 | const struct cpumask *mask; | |
2390 | ||
2391 | mask = cpumask_of_node(pgdat->node_id); | |
2392 | ||
2393 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) | |
2394 | /* One of our CPUs online: restore mask */ | |
2395 | set_cpus_allowed_ptr(pgdat->kswapd, mask); | |
2396 | } | |
2397 | } | |
2398 | return NOTIFY_OK; | |
2399 | } | |
2400 | ||
2401 | /* | |
2402 | * This kswapd start function will be called by init and node-hot-add. | |
2403 | * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. | |
2404 | */ | |
2405 | int kswapd_run(int nid) | |
2406 | { | |
2407 | pg_data_t *pgdat = NODE_DATA(nid); | |
2408 | int ret = 0; | |
2409 | ||
2410 | if (pgdat->kswapd) | |
2411 | return 0; | |
2412 | ||
2413 | pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); | |
2414 | if (IS_ERR(pgdat->kswapd)) { | |
2415 | /* failure at boot is fatal */ | |
2416 | BUG_ON(system_state == SYSTEM_BOOTING); | |
2417 | printk("Failed to start kswapd on node %d\n",nid); | |
2418 | ret = -1; | |
2419 | } | |
2420 | return ret; | |
2421 | } | |
2422 | ||
2423 | /* | |
2424 | * Called by memory hotplug when all memory in a node is offlined. | |
2425 | */ | |
2426 | void kswapd_stop(int nid) | |
2427 | { | |
2428 | struct task_struct *kswapd = NODE_DATA(nid)->kswapd; | |
2429 | ||
2430 | if (kswapd) | |
2431 | kthread_stop(kswapd); | |
2432 | } | |
2433 | ||
2434 | static int __init kswapd_init(void) | |
2435 | { | |
2436 | int nid; | |
2437 | ||
2438 | swap_setup(); | |
2439 | for_each_node_state(nid, N_HIGH_MEMORY) | |
2440 | kswapd_run(nid); | |
2441 | hotcpu_notifier(cpu_callback, 0); | |
2442 | return 0; | |
2443 | } | |
2444 | ||
2445 | module_init(kswapd_init) | |
2446 | ||
2447 | #ifdef CONFIG_NUMA | |
2448 | /* | |
2449 | * Zone reclaim mode | |
2450 | * | |
2451 | * If non-zero call zone_reclaim when the number of free pages falls below | |
2452 | * the watermarks. | |
2453 | */ | |
2454 | int zone_reclaim_mode __read_mostly; | |
2455 | ||
2456 | #define RECLAIM_OFF 0 | |
2457 | #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ | |
2458 | #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ | |
2459 | #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ | |
2460 | ||
2461 | /* | |
2462 | * Priority for ZONE_RECLAIM. This determines the fraction of pages | |
2463 | * of a node considered for each zone_reclaim. 4 scans 1/16th of | |
2464 | * a zone. | |
2465 | */ | |
2466 | #define ZONE_RECLAIM_PRIORITY 4 | |
2467 | ||
2468 | /* | |
2469 | * Percentage of pages in a zone that must be unmapped for zone_reclaim to | |
2470 | * occur. | |
2471 | */ | |
2472 | int sysctl_min_unmapped_ratio = 1; | |
2473 | ||
2474 | /* | |
2475 | * If the number of slab pages in a zone grows beyond this percentage then | |
2476 | * slab reclaim needs to occur. | |
2477 | */ | |
2478 | int sysctl_min_slab_ratio = 5; | |
2479 | ||
2480 | static inline unsigned long zone_unmapped_file_pages(struct zone *zone) | |
2481 | { | |
2482 | unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); | |
2483 | unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + | |
2484 | zone_page_state(zone, NR_ACTIVE_FILE); | |
2485 | ||
2486 | /* | |
2487 | * It's possible for there to be more file mapped pages than | |
2488 | * accounted for by the pages on the file LRU lists because | |
2489 | * tmpfs pages accounted for as ANON can also be FILE_MAPPED | |
2490 | */ | |
2491 | return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; | |
2492 | } | |
2493 | ||
2494 | /* Work out how many page cache pages we can reclaim in this reclaim_mode */ | |
2495 | static long zone_pagecache_reclaimable(struct zone *zone) | |
2496 | { | |
2497 | long nr_pagecache_reclaimable; | |
2498 | long delta = 0; | |
2499 | ||
2500 | /* | |
2501 | * If RECLAIM_SWAP is set, then all file pages are considered | |
2502 | * potentially reclaimable. Otherwise, we have to worry about | |
2503 | * pages like swapcache and zone_unmapped_file_pages() provides | |
2504 | * a better estimate | |
2505 | */ | |
2506 | if (zone_reclaim_mode & RECLAIM_SWAP) | |
2507 | nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); | |
2508 | else | |
2509 | nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); | |
2510 | ||
2511 | /* If we can't clean pages, remove dirty pages from consideration */ | |
2512 | if (!(zone_reclaim_mode & RECLAIM_WRITE)) | |
2513 | delta += zone_page_state(zone, NR_FILE_DIRTY); | |
2514 | ||
2515 | /* Watch for any possible underflows due to delta */ | |
2516 | if (unlikely(delta > nr_pagecache_reclaimable)) | |
2517 | delta = nr_pagecache_reclaimable; | |
2518 | ||
2519 | return nr_pagecache_reclaimable - delta; | |
2520 | } | |
2521 | ||
2522 | /* | |
2523 | * Try to free up some pages from this zone through reclaim. | |
2524 | */ | |
2525 | static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) | |
2526 | { | |
2527 | /* Minimum pages needed in order to stay on node */ | |
2528 | const unsigned long nr_pages = 1 << order; | |
2529 | struct task_struct *p = current; | |
2530 | struct reclaim_state reclaim_state; | |
2531 | int priority; | |
2532 | struct scan_control sc = { | |
2533 | .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), | |
2534 | .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), | |
2535 | .may_swap = 1, | |
2536 | .nr_to_reclaim = max_t(unsigned long, nr_pages, | |
2537 | SWAP_CLUSTER_MAX), | |
2538 | .gfp_mask = gfp_mask, | |
2539 | .swappiness = vm_swappiness, | |
2540 | .order = order, | |
2541 | .isolate_pages = isolate_pages_global, | |
2542 | }; | |
2543 | unsigned long slab_reclaimable; | |
2544 | ||
2545 | disable_swap_token(); | |
2546 | cond_resched(); | |
2547 | /* | |
2548 | * We need to be able to allocate from the reserves for RECLAIM_SWAP | |
2549 | * and we also need to be able to write out pages for RECLAIM_WRITE | |
2550 | * and RECLAIM_SWAP. | |
2551 | */ | |
2552 | p->flags |= PF_MEMALLOC | PF_SWAPWRITE; | |
2553 | reclaim_state.reclaimed_slab = 0; | |
2554 | p->reclaim_state = &reclaim_state; | |
2555 | ||
2556 | if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { | |
2557 | /* | |
2558 | * Free memory by calling shrink zone with increasing | |
2559 | * priorities until we have enough memory freed. | |
2560 | */ | |
2561 | priority = ZONE_RECLAIM_PRIORITY; | |
2562 | do { | |
2563 | note_zone_scanning_priority(zone, priority); | |
2564 | shrink_zone(priority, zone, &sc); | |
2565 | priority--; | |
2566 | } while (priority >= 0 && sc.nr_reclaimed < nr_pages); | |
2567 | } | |
2568 | ||
2569 | slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE); | |
2570 | if (slab_reclaimable > zone->min_slab_pages) { | |
2571 | /* | |
2572 | * shrink_slab() does not currently allow us to determine how | |
2573 | * many pages were freed in this zone. So we take the current | |
2574 | * number of slab pages and shake the slab until it is reduced | |
2575 | * by the same nr_pages that we used for reclaiming unmapped | |
2576 | * pages. | |
2577 | * | |
2578 | * Note that shrink_slab will free memory on all zones and may | |
2579 | * take a long time. | |
2580 | */ | |
2581 | while (shrink_slab(sc.nr_scanned, gfp_mask, order) && | |
2582 | zone_page_state(zone, NR_SLAB_RECLAIMABLE) > | |
2583 | slab_reclaimable - nr_pages) | |
2584 | ; | |
2585 | ||
2586 | /* | |
2587 | * Update nr_reclaimed by the number of slab pages we | |
2588 | * reclaimed from this zone. | |
2589 | */ | |
2590 | sc.nr_reclaimed += slab_reclaimable - | |
2591 | zone_page_state(zone, NR_SLAB_RECLAIMABLE); | |
2592 | } | |
2593 | ||
2594 | p->reclaim_state = NULL; | |
2595 | current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); | |
2596 | return sc.nr_reclaimed >= nr_pages; | |
2597 | } | |
2598 | ||
2599 | int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) | |
2600 | { | |
2601 | int node_id; | |
2602 | int ret; | |
2603 | ||
2604 | /* | |
2605 | * Zone reclaim reclaims unmapped file backed pages and | |
2606 | * slab pages if we are over the defined limits. | |
2607 | * | |
2608 | * A small portion of unmapped file backed pages is needed for | |
2609 | * file I/O otherwise pages read by file I/O will be immediately | |
2610 | * thrown out if the zone is overallocated. So we do not reclaim | |
2611 | * if less than a specified percentage of the zone is used by | |
2612 | * unmapped file backed pages. | |
2613 | */ | |
2614 | if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && | |
2615 | zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) | |
2616 | return ZONE_RECLAIM_FULL; | |
2617 | ||
2618 | if (zone_is_all_unreclaimable(zone)) | |
2619 | return ZONE_RECLAIM_FULL; | |
2620 | ||
2621 | /* | |
2622 | * Do not scan if the allocation should not be delayed. | |
2623 | */ | |
2624 | if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) | |
2625 | return ZONE_RECLAIM_NOSCAN; | |
2626 | ||
2627 | /* | |
2628 | * Only run zone reclaim on the local zone or on zones that do not | |
2629 | * have associated processors. This will favor the local processor | |
2630 | * over remote processors and spread off node memory allocations | |
2631 | * as wide as possible. | |
2632 | */ | |
2633 | node_id = zone_to_nid(zone); | |
2634 | if (node_state(node_id, N_CPU) && node_id != numa_node_id()) | |
2635 | return ZONE_RECLAIM_NOSCAN; | |
2636 | ||
2637 | if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) | |
2638 | return ZONE_RECLAIM_NOSCAN; | |
2639 | ||
2640 | ret = __zone_reclaim(zone, gfp_mask, order); | |
2641 | zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); | |
2642 | ||
2643 | if (!ret) | |
2644 | count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); | |
2645 | ||
2646 | return ret; | |
2647 | } | |
2648 | #endif | |
2649 | ||
2650 | /* | |
2651 | * page_evictable - test whether a page is evictable | |
2652 | * @page: the page to test | |
2653 | * @vma: the VMA in which the page is or will be mapped, may be NULL | |
2654 | * | |
2655 | * Test whether page is evictable--i.e., should be placed on active/inactive | |
2656 | * lists vs unevictable list. The vma argument is !NULL when called from the | |
2657 | * fault path to determine how to instantate a new page. | |
2658 | * | |
2659 | * Reasons page might not be evictable: | |
2660 | * (1) page's mapping marked unevictable | |
2661 | * (2) page is part of an mlocked VMA | |
2662 | * | |
2663 | */ | |
2664 | int page_evictable(struct page *page, struct vm_area_struct *vma) | |
2665 | { | |
2666 | ||
2667 | if (mapping_unevictable(page_mapping(page))) | |
2668 | return 0; | |
2669 | ||
2670 | if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) | |
2671 | return 0; | |
2672 | ||
2673 | return 1; | |
2674 | } | |
2675 | ||
2676 | /** | |
2677 | * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list | |
2678 | * @page: page to check evictability and move to appropriate lru list | |
2679 | * @zone: zone page is in | |
2680 | * | |
2681 | * Checks a page for evictability and moves the page to the appropriate | |
2682 | * zone lru list. | |
2683 | * | |
2684 | * Restrictions: zone->lru_lock must be held, page must be on LRU and must | |
2685 | * have PageUnevictable set. | |
2686 | */ | |
2687 | static void check_move_unevictable_page(struct page *page, struct zone *zone) | |
2688 | { | |
2689 | VM_BUG_ON(PageActive(page)); | |
2690 | ||
2691 | retry: | |
2692 | ClearPageUnevictable(page); | |
2693 | if (page_evictable(page, NULL)) { | |
2694 | enum lru_list l = page_lru_base_type(page); | |
2695 | ||
2696 | __dec_zone_state(zone, NR_UNEVICTABLE); | |
2697 | list_move(&page->lru, &zone->lru[l].list); | |
2698 | mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); | |
2699 | __inc_zone_state(zone, NR_INACTIVE_ANON + l); | |
2700 | __count_vm_event(UNEVICTABLE_PGRESCUED); | |
2701 | } else { | |
2702 | /* | |
2703 | * rotate unevictable list | |
2704 | */ | |
2705 | SetPageUnevictable(page); | |
2706 | list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); | |
2707 | mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); | |
2708 | if (page_evictable(page, NULL)) | |
2709 | goto retry; | |
2710 | } | |
2711 | } | |
2712 | ||
2713 | /** | |
2714 | * scan_mapping_unevictable_pages - scan an address space for evictable pages | |
2715 | * @mapping: struct address_space to scan for evictable pages | |
2716 | * | |
2717 | * Scan all pages in mapping. Check unevictable pages for | |
2718 | * evictability and move them to the appropriate zone lru list. | |
2719 | */ | |
2720 | void scan_mapping_unevictable_pages(struct address_space *mapping) | |
2721 | { | |
2722 | pgoff_t next = 0; | |
2723 | pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> | |
2724 | PAGE_CACHE_SHIFT; | |
2725 | struct zone *zone; | |
2726 | struct pagevec pvec; | |
2727 | ||
2728 | if (mapping->nrpages == 0) | |
2729 | return; | |
2730 | ||
2731 | pagevec_init(&pvec, 0); | |
2732 | while (next < end && | |
2733 | pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { | |
2734 | int i; | |
2735 | int pg_scanned = 0; | |
2736 | ||
2737 | zone = NULL; | |
2738 | ||
2739 | for (i = 0; i < pagevec_count(&pvec); i++) { | |
2740 | struct page *page = pvec.pages[i]; | |
2741 | pgoff_t page_index = page->index; | |
2742 | struct zone *pagezone = page_zone(page); | |
2743 | ||
2744 | pg_scanned++; | |
2745 | if (page_index > next) | |
2746 | next = page_index; | |
2747 | next++; | |
2748 | ||
2749 | if (pagezone != zone) { | |
2750 | if (zone) | |
2751 | spin_unlock_irq(&zone->lru_lock); | |
2752 | zone = pagezone; | |
2753 | spin_lock_irq(&zone->lru_lock); | |
2754 | } | |
2755 | ||
2756 | if (PageLRU(page) && PageUnevictable(page)) | |
2757 | check_move_unevictable_page(page, zone); | |
2758 | } | |
2759 | if (zone) | |
2760 | spin_unlock_irq(&zone->lru_lock); | |
2761 | pagevec_release(&pvec); | |
2762 | ||
2763 | count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); | |
2764 | } | |
2765 | ||
2766 | } | |
2767 | ||
2768 | /** | |
2769 | * scan_zone_unevictable_pages - check unevictable list for evictable pages | |
2770 | * @zone - zone of which to scan the unevictable list | |
2771 | * | |
2772 | * Scan @zone's unevictable LRU lists to check for pages that have become | |
2773 | * evictable. Move those that have to @zone's inactive list where they | |
2774 | * become candidates for reclaim, unless shrink_inactive_zone() decides | |
2775 | * to reactivate them. Pages that are still unevictable are rotated | |
2776 | * back onto @zone's unevictable list. | |
2777 | */ | |
2778 | #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ | |
2779 | static void scan_zone_unevictable_pages(struct zone *zone) | |
2780 | { | |
2781 | struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; | |
2782 | unsigned long scan; | |
2783 | unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); | |
2784 | ||
2785 | while (nr_to_scan > 0) { | |
2786 | unsigned long batch_size = min(nr_to_scan, | |
2787 | SCAN_UNEVICTABLE_BATCH_SIZE); | |
2788 | ||
2789 | spin_lock_irq(&zone->lru_lock); | |
2790 | for (scan = 0; scan < batch_size; scan++) { | |
2791 | struct page *page = lru_to_page(l_unevictable); | |
2792 | ||
2793 | if (!trylock_page(page)) | |
2794 | continue; | |
2795 | ||
2796 | prefetchw_prev_lru_page(page, l_unevictable, flags); | |
2797 | ||
2798 | if (likely(PageLRU(page) && PageUnevictable(page))) | |
2799 | check_move_unevictable_page(page, zone); | |
2800 | ||
2801 | unlock_page(page); | |
2802 | } | |
2803 | spin_unlock_irq(&zone->lru_lock); | |
2804 | ||
2805 | nr_to_scan -= batch_size; | |
2806 | } | |
2807 | } | |
2808 | ||
2809 | ||
2810 | /** | |
2811 | * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages | |
2812 | * | |
2813 | * A really big hammer: scan all zones' unevictable LRU lists to check for | |
2814 | * pages that have become evictable. Move those back to the zones' | |
2815 | * inactive list where they become candidates for reclaim. | |
2816 | * This occurs when, e.g., we have unswappable pages on the unevictable lists, | |
2817 | * and we add swap to the system. As such, it runs in the context of a task | |
2818 | * that has possibly/probably made some previously unevictable pages | |
2819 | * evictable. | |
2820 | */ | |
2821 | static void scan_all_zones_unevictable_pages(void) | |
2822 | { | |
2823 | struct zone *zone; | |
2824 | ||
2825 | for_each_zone(zone) { | |
2826 | scan_zone_unevictable_pages(zone); | |
2827 | } | |
2828 | } | |
2829 | ||
2830 | /* | |
2831 | * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of | |
2832 | * all nodes' unevictable lists for evictable pages | |
2833 | */ | |
2834 | unsigned long scan_unevictable_pages; | |
2835 | ||
2836 | int scan_unevictable_handler(struct ctl_table *table, int write, | |
2837 | void __user *buffer, | |
2838 | size_t *length, loff_t *ppos) | |
2839 | { | |
2840 | proc_doulongvec_minmax(table, write, buffer, length, ppos); | |
2841 | ||
2842 | if (write && *(unsigned long *)table->data) | |
2843 | scan_all_zones_unevictable_pages(); | |
2844 | ||
2845 | scan_unevictable_pages = 0; | |
2846 | return 0; | |
2847 | } | |
2848 | ||
2849 | /* | |
2850 | * per node 'scan_unevictable_pages' attribute. On demand re-scan of | |
2851 | * a specified node's per zone unevictable lists for evictable pages. | |
2852 | */ | |
2853 | ||
2854 | static ssize_t read_scan_unevictable_node(struct sys_device *dev, | |
2855 | struct sysdev_attribute *attr, | |
2856 | char *buf) | |
2857 | { | |
2858 | return sprintf(buf, "0\n"); /* always zero; should fit... */ | |
2859 | } | |
2860 | ||
2861 | static ssize_t write_scan_unevictable_node(struct sys_device *dev, | |
2862 | struct sysdev_attribute *attr, | |
2863 | const char *buf, size_t count) | |
2864 | { | |
2865 | struct zone *node_zones = NODE_DATA(dev->id)->node_zones; | |
2866 | struct zone *zone; | |
2867 | unsigned long res; | |
2868 | unsigned long req = strict_strtoul(buf, 10, &res); | |
2869 | ||
2870 | if (!req) | |
2871 | return 1; /* zero is no-op */ | |
2872 | ||
2873 | for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { | |
2874 | if (!populated_zone(zone)) | |
2875 | continue; | |
2876 | scan_zone_unevictable_pages(zone); | |
2877 | } | |
2878 | return 1; | |
2879 | } | |
2880 | ||
2881 | ||
2882 | static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, | |
2883 | read_scan_unevictable_node, | |
2884 | write_scan_unevictable_node); | |
2885 | ||
2886 | int scan_unevictable_register_node(struct node *node) | |
2887 | { | |
2888 | return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); | |
2889 | } | |
2890 | ||
2891 | void scan_unevictable_unregister_node(struct node *node) | |
2892 | { | |
2893 | sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); | |
2894 | } | |
2895 |