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