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1 | /* |
2 | * linux/mm/vmscan.c |
3 | * |
4 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
5 | * |
6 | * Swap reorganised 29.12.95, Stephen Tweedie. |
7 | * kswapd added: 7.1.96 sct |
8 | * Removed kswapd_ctl limits, and swap out as many pages as needed |
9 | * to bring the system back to freepages.high: 2.4.97, Rik van Riel. |
10 | * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). |
11 | * Multiqueue VM started 5.8.00, Rik van Riel. |
12 | */ |
13 | |
14 | #include <linux/mm.h> |
15 | #include <linux/module.h> |
16 | #include <linux/slab.h> |
17 | #include <linux/kernel_stat.h> |
18 | #include <linux/swap.h> |
19 | #include <linux/pagemap.h> |
20 | #include <linux/init.h> |
21 | #include <linux/highmem.h> |
22 | #include <linux/vmstat.h> |
23 | #include <linux/file.h> |
24 | #include <linux/writeback.h> |
25 | #include <linux/blkdev.h> |
26 | #include <linux/buffer_head.h> /* for try_to_release_page(), |
27 | buffer_heads_over_limit */ |
28 | #include <linux/mm_inline.h> |
29 | #include <linux/pagevec.h> |
30 | #include <linux/backing-dev.h> |
31 | #include <linux/rmap.h> |
32 | #include <linux/topology.h> |
33 | #include <linux/cpu.h> |
34 | #include <linux/cpuset.h> |
35 | #include <linux/notifier.h> |
36 | #include <linux/rwsem.h> |
37 | #include <linux/delay.h> |
38 | #include <linux/kthread.h> |
39 | #include <linux/freezer.h> |
40 | #include <linux/memcontrol.h> |
41 | #include <linux/delayacct.h> |
42 | #include <linux/sysctl.h> |
43 | |
44 | #include <asm/tlbflush.h> |
45 | #include <asm/div64.h> |
46 | |
47 | #include <linux/swapops.h> |
48 | |
49 | #include "internal.h" |
50 | |
51 | struct scan_control { |
52 | /* Incremented by the number of inactive pages that were scanned */ |
53 | unsigned long nr_scanned; |
54 | |
55 | /* Number of pages freed so far during a call to shrink_zones() */ |
56 | unsigned long nr_reclaimed; |
57 | |
58 | /* This context's GFP mask */ |
59 | gfp_t gfp_mask; |
60 | |
61 | int may_writepage; |
62 | |
63 | /* Can mapped pages be reclaimed? */ |
64 | int may_unmap; |
65 | |
66 | /* Can pages be swapped as part of reclaim? */ |
67 | int may_swap; |
68 | |
69 | /* This context's SWAP_CLUSTER_MAX. If freeing memory for |
70 | * suspend, we effectively ignore SWAP_CLUSTER_MAX. |
71 | * In this context, it doesn't matter that we scan the |
72 | * whole list at once. */ |
73 | int swap_cluster_max; |
74 | |
75 | int swappiness; |
76 | |
77 | int all_unreclaimable; |
78 | |
79 | int order; |
80 | |
81 | /* Which cgroup do we reclaim from */ |
82 | struct mem_cgroup *mem_cgroup; |
83 | |
84 | /* |
85 | * Nodemask of nodes allowed by the caller. If NULL, all nodes |
86 | * are scanned. |
87 | */ |
88 | nodemask_t *nodemask; |
89 | |
90 | /* Pluggable isolate pages callback */ |
91 | unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst, |
92 | unsigned long *scanned, int order, int mode, |
93 | struct zone *z, struct mem_cgroup *mem_cont, |
94 | int active, int file); |
95 | }; |
96 | |
97 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) |
98 | |
99 | #ifdef ARCH_HAS_PREFETCH |
100 | #define prefetch_prev_lru_page(_page, _base, _field) \ |
101 | do { \ |
102 | if ((_page)->lru.prev != _base) { \ |
103 | struct page *prev; \ |
104 | \ |
105 | prev = lru_to_page(&(_page->lru)); \ |
106 | prefetch(&prev->_field); \ |
107 | } \ |
108 | } while (0) |
109 | #else |
110 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) |
111 | #endif |
112 | |
113 | #ifdef ARCH_HAS_PREFETCHW |
114 | #define prefetchw_prev_lru_page(_page, _base, _field) \ |
115 | do { \ |
116 | if ((_page)->lru.prev != _base) { \ |
117 | struct page *prev; \ |
118 | \ |
119 | prev = lru_to_page(&(_page->lru)); \ |
120 | prefetchw(&prev->_field); \ |
121 | } \ |
122 | } while (0) |
123 | #else |
124 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) |
125 | #endif |
126 | |
127 | /* |
128 | * From 0 .. 100. Higher means more swappy. |
129 | */ |
130 | int vm_swappiness = 60; |
131 | long vm_total_pages; /* The total number of pages which the VM controls */ |
132 | |
133 | static LIST_HEAD(shrinker_list); |
134 | static DECLARE_RWSEM(shrinker_rwsem); |
135 | |
136 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
137 | #define scanning_global_lru(sc) (!(sc)->mem_cgroup) |
138 | #else |
139 | #define scanning_global_lru(sc) (1) |
140 | #endif |
141 | |
142 | static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, |
143 | struct scan_control *sc) |
144 | { |
145 | if (!scanning_global_lru(sc)) |
146 | return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); |
147 | |
148 | return &zone->reclaim_stat; |
149 | } |
150 | |
151 | static unsigned long zone_nr_pages(struct zone *zone, struct scan_control *sc, |
152 | enum lru_list lru) |
153 | { |
154 | if (!scanning_global_lru(sc)) |
155 | return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru); |
156 | |
157 | return zone_page_state(zone, NR_LRU_BASE + lru); |
158 | } |
159 | |
160 | |
161 | /* |
162 | * Add a shrinker callback to be called from the vm |
163 | */ |
164 | void register_shrinker(struct shrinker *shrinker) |
165 | { |
166 | shrinker->nr = 0; |
167 | down_write(&shrinker_rwsem); |
168 | list_add_tail(&shrinker->list, &shrinker_list); |
169 | up_write(&shrinker_rwsem); |
170 | } |
171 | EXPORT_SYMBOL(register_shrinker); |
172 | |
173 | /* |
174 | * Remove one |
175 | */ |
176 | void unregister_shrinker(struct shrinker *shrinker) |
177 | { |
178 | down_write(&shrinker_rwsem); |
179 | list_del(&shrinker->list); |
180 | up_write(&shrinker_rwsem); |
181 | } |
182 | EXPORT_SYMBOL(unregister_shrinker); |
183 | |
184 | #define SHRINK_BATCH 128 |
185 | /* |
186 | * Call the shrink functions to age shrinkable caches |
187 | * |
188 | * Here we assume it costs one seek to replace a lru page and that it also |
189 | * takes a seek to recreate a cache object. With this in mind we age equal |
190 | * percentages of the lru and ageable caches. This should balance the seeks |
191 | * generated by these structures. |
192 | * |
193 | * If the vm encountered mapped pages on the LRU it increase the pressure on |
194 | * slab to avoid swapping. |
195 | * |
196 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. |
197 | * |
198 | * `lru_pages' represents the number of on-LRU pages in all the zones which |
199 | * are eligible for the caller's allocation attempt. It is used for balancing |
200 | * slab reclaim versus page reclaim. |
201 | * |
202 | * Returns the number of slab objects which we shrunk. |
203 | */ |
204 | unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, |
205 | unsigned long lru_pages) |
206 | { |
207 | struct shrinker *shrinker; |
208 | unsigned long ret = 0; |
209 | |
210 | if (scanned == 0) |
211 | scanned = SWAP_CLUSTER_MAX; |
212 | |
213 | if (!down_read_trylock(&shrinker_rwsem)) |
214 | return 1; /* Assume we'll be able to shrink next time */ |
215 | |
216 | list_for_each_entry(shrinker, &shrinker_list, list) { |
217 | unsigned long long delta; |
218 | unsigned long total_scan; |
219 | unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask); |
220 | |
221 | delta = (4 * scanned) / shrinker->seeks; |
222 | delta *= max_pass; |
223 | do_div(delta, lru_pages + 1); |
224 | shrinker->nr += delta; |
225 | if (shrinker->nr < 0) { |
226 | printk(KERN_ERR "shrink_slab: %pF negative objects to " |
227 | "delete nr=%ld\n", |
228 | shrinker->shrink, shrinker->nr); |
229 | shrinker->nr = max_pass; |
230 | } |
231 | |
232 | /* |
233 | * Avoid risking looping forever due to too large nr value: |
234 | * never try to free more than twice the estimate number of |
235 | * freeable entries. |
236 | */ |
237 | if (shrinker->nr > max_pass * 2) |
238 | shrinker->nr = max_pass * 2; |
239 | |
240 | total_scan = shrinker->nr; |
241 | shrinker->nr = 0; |
242 | |
243 | while (total_scan >= SHRINK_BATCH) { |
244 | long this_scan = SHRINK_BATCH; |
245 | int shrink_ret; |
246 | int nr_before; |
247 | |
248 | nr_before = (*shrinker->shrink)(0, gfp_mask); |
249 | shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask); |
250 | if (shrink_ret == -1) |
251 | break; |
252 | if (shrink_ret < nr_before) |
253 | ret += nr_before - shrink_ret; |
254 | count_vm_events(SLABS_SCANNED, this_scan); |
255 | total_scan -= this_scan; |
256 | |
257 | cond_resched(); |
258 | } |
259 | |
260 | shrinker->nr += total_scan; |
261 | } |
262 | up_read(&shrinker_rwsem); |
263 | return ret; |
264 | } |
265 | |
266 | /* Called without lock on whether page is mapped, so answer is unstable */ |
267 | static inline int page_mapping_inuse(struct page *page) |
268 | { |
269 | struct address_space *mapping; |
270 | |
271 | /* Page is in somebody's page tables. */ |
272 | if (page_mapped(page)) |
273 | return 1; |
274 | |
275 | /* Be more reluctant to reclaim swapcache than pagecache */ |
276 | if (PageSwapCache(page)) |
277 | return 1; |
278 | |
279 | mapping = page_mapping(page); |
280 | if (!mapping) |
281 | return 0; |
282 | |
283 | /* File is mmap'd by somebody? */ |
284 | return mapping_mapped(mapping); |
285 | } |
286 | |
287 | static inline int is_page_cache_freeable(struct page *page) |
288 | { |
289 | return page_count(page) - !!page_has_private(page) == 2; |
290 | } |
291 | |
292 | static int may_write_to_queue(struct backing_dev_info *bdi) |
293 | { |
294 | if (current->flags & PF_SWAPWRITE) |
295 | return 1; |
296 | if (!bdi_write_congested(bdi)) |
297 | return 1; |
298 | if (bdi == current->backing_dev_info) |
299 | return 1; |
300 | return 0; |
301 | } |
302 | |
303 | /* |
304 | * We detected a synchronous write error writing a page out. Probably |
305 | * -ENOSPC. We need to propagate that into the address_space for a subsequent |
306 | * fsync(), msync() or close(). |
307 | * |
308 | * The tricky part is that after writepage we cannot touch the mapping: nothing |
309 | * prevents it from being freed up. But we have a ref on the page and once |
310 | * that page is locked, the mapping is pinned. |
311 | * |
312 | * We're allowed to run sleeping lock_page() here because we know the caller has |
313 | * __GFP_FS. |
314 | */ |
315 | static void handle_write_error(struct address_space *mapping, |
316 | struct page *page, int error) |
317 | { |
318 | lock_page(page); |
319 | if (page_mapping(page) == mapping) |
320 | mapping_set_error(mapping, error); |
321 | unlock_page(page); |
322 | } |
323 | |
324 | /* Request for sync pageout. */ |
325 | enum pageout_io { |
326 | PAGEOUT_IO_ASYNC, |
327 | PAGEOUT_IO_SYNC, |
328 | }; |
329 | |
330 | /* possible outcome of pageout() */ |
331 | typedef enum { |
332 | /* failed to write page out, page is locked */ |
333 | PAGE_KEEP, |
334 | /* move page to the active list, page is locked */ |
335 | PAGE_ACTIVATE, |
336 | /* page has been sent to the disk successfully, page is unlocked */ |
337 | PAGE_SUCCESS, |
338 | /* page is clean and locked */ |
339 | PAGE_CLEAN, |
340 | } pageout_t; |
341 | |
342 | /* |
343 | * pageout is called by shrink_page_list() for each dirty page. |
344 | * Calls ->writepage(). |
345 | */ |
346 | static pageout_t pageout(struct page *page, struct address_space *mapping, |
347 | enum pageout_io sync_writeback) |
348 | { |
349 | /* |
350 | * If the page is dirty, only perform writeback if that write |
351 | * will be non-blocking. To prevent this allocation from being |
352 | * stalled by pagecache activity. But note that there may be |
353 | * stalls if we need to run get_block(). We could test |
354 | * PagePrivate for that. |
355 | * |
356 | * If this process is currently in generic_file_write() against |
357 | * this page's queue, we can perform writeback even if that |
358 | * will block. |
359 | * |
360 | * If the page is swapcache, write it back even if that would |
361 | * block, for some throttling. This happens by accident, because |
362 | * swap_backing_dev_info is bust: it doesn't reflect the |
363 | * congestion state of the swapdevs. Easy to fix, if needed. |
364 | * See swapfile.c:page_queue_congested(). |
365 | */ |
366 | if (!is_page_cache_freeable(page)) |
367 | return PAGE_KEEP; |
368 | if (!mapping) { |
369 | /* |
370 | * Some data journaling orphaned pages can have |
371 | * page->mapping == NULL while being dirty with clean buffers. |
372 | */ |
373 | if (page_has_private(page)) { |
374 | if (try_to_free_buffers(page)) { |
375 | ClearPageDirty(page); |
376 | printk("%s: orphaned page\n", __func__); |
377 | return PAGE_CLEAN; |
378 | } |
379 | } |
380 | return PAGE_KEEP; |
381 | } |
382 | if (mapping->a_ops->writepage == NULL) |
383 | return PAGE_ACTIVATE; |
384 | if (!may_write_to_queue(mapping->backing_dev_info)) |
385 | return PAGE_KEEP; |
386 | |
387 | if (clear_page_dirty_for_io(page)) { |
388 | int res; |
389 | struct writeback_control wbc = { |
390 | .sync_mode = WB_SYNC_NONE, |
391 | .nr_to_write = SWAP_CLUSTER_MAX, |
392 | .range_start = 0, |
393 | .range_end = LLONG_MAX, |
394 | .nonblocking = 1, |
395 | .for_reclaim = 1, |
396 | }; |
397 | |
398 | SetPageReclaim(page); |
399 | res = mapping->a_ops->writepage(page, &wbc); |
400 | if (res < 0) |
401 | handle_write_error(mapping, page, res); |
402 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
403 | ClearPageReclaim(page); |
404 | return PAGE_ACTIVATE; |
405 | } |
406 | |
407 | /* |
408 | * Wait on writeback if requested to. This happens when |
409 | * direct reclaiming a large contiguous area and the |
410 | * first attempt to free a range of pages fails. |
411 | */ |
412 | if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC) |
413 | wait_on_page_writeback(page); |
414 | |
415 | if (!PageWriteback(page)) { |
416 | /* synchronous write or broken a_ops? */ |
417 | ClearPageReclaim(page); |
418 | } |
419 | inc_zone_page_state(page, NR_VMSCAN_WRITE); |
420 | return PAGE_SUCCESS; |
421 | } |
422 | |
423 | return PAGE_CLEAN; |
424 | } |
425 | |
426 | /* |
427 | * Same as remove_mapping, but if the page is removed from the mapping, it |
428 | * gets returned with a refcount of 0. |
429 | */ |
430 | static int __remove_mapping(struct address_space *mapping, struct page *page) |
431 | { |
432 | BUG_ON(!PageLocked(page)); |
433 | BUG_ON(mapping != page_mapping(page)); |
434 | |
435 | spin_lock_irq(&mapping->tree_lock); |
436 | /* |
437 | * The non racy check for a busy page. |
438 | * |
439 | * Must be careful with the order of the tests. When someone has |
440 | * a ref to the page, it may be possible that they dirty it then |
441 | * drop the reference. So if PageDirty is tested before page_count |
442 | * here, then the following race may occur: |
443 | * |
444 | * get_user_pages(&page); |
445 | * [user mapping goes away] |
446 | * write_to(page); |
447 | * !PageDirty(page) [good] |
448 | * SetPageDirty(page); |
449 | * put_page(page); |
450 | * !page_count(page) [good, discard it] |
451 | * |
452 | * [oops, our write_to data is lost] |
453 | * |
454 | * Reversing the order of the tests ensures such a situation cannot |
455 | * escape unnoticed. The smp_rmb is needed to ensure the page->flags |
456 | * load is not satisfied before that of page->_count. |
457 | * |
458 | * Note that if SetPageDirty is always performed via set_page_dirty, |
459 | * and thus under tree_lock, then this ordering is not required. |
460 | */ |
461 | if (!page_freeze_refs(page, 2)) |
462 | goto cannot_free; |
463 | /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ |
464 | if (unlikely(PageDirty(page))) { |
465 | page_unfreeze_refs(page, 2); |
466 | goto cannot_free; |
467 | } |
468 | |
469 | if (PageSwapCache(page)) { |
470 | swp_entry_t swap = { .val = page_private(page) }; |
471 | __delete_from_swap_cache(page); |
472 | spin_unlock_irq(&mapping->tree_lock); |
473 | swapcache_free(swap, page); |
474 | } else { |
475 | __remove_from_page_cache(page); |
476 | spin_unlock_irq(&mapping->tree_lock); |
477 | mem_cgroup_uncharge_cache_page(page); |
478 | } |
479 | |
480 | return 1; |
481 | |
482 | cannot_free: |
483 | spin_unlock_irq(&mapping->tree_lock); |
484 | return 0; |
485 | } |
486 | |
487 | /* |
488 | * Attempt to detach a locked page from its ->mapping. If it is dirty or if |
489 | * someone else has a ref on the page, abort and return 0. If it was |
490 | * successfully detached, return 1. Assumes the caller has a single ref on |
491 | * this page. |
492 | */ |
493 | int remove_mapping(struct address_space *mapping, struct page *page) |
494 | { |
495 | if (__remove_mapping(mapping, page)) { |
496 | /* |
497 | * Unfreezing the refcount with 1 rather than 2 effectively |
498 | * drops the pagecache ref for us without requiring another |
499 | * atomic operation. |
500 | */ |
501 | page_unfreeze_refs(page, 1); |
502 | return 1; |
503 | } |
504 | return 0; |
505 | } |
506 | |
507 | /** |
508 | * putback_lru_page - put previously isolated page onto appropriate LRU list |
509 | * @page: page to be put back to appropriate lru list |
510 | * |
511 | * Add previously isolated @page to appropriate LRU list. |
512 | * Page may still be unevictable for other reasons. |
513 | * |
514 | * lru_lock must not be held, interrupts must be enabled. |
515 | */ |
516 | void putback_lru_page(struct page *page) |
517 | { |
518 | int lru; |
519 | int active = !!TestClearPageActive(page); |
520 | int was_unevictable = PageUnevictable(page); |
521 | |
522 | VM_BUG_ON(PageLRU(page)); |
523 | |
524 | redo: |
525 | ClearPageUnevictable(page); |
526 | |
527 | if (page_evictable(page, NULL)) { |
528 | /* |
529 | * For evictable pages, we can use the cache. |
530 | * In event of a race, worst case is we end up with an |
531 | * unevictable page on [in]active list. |
532 | * We know how to handle that. |
533 | */ |
534 | lru = active + page_is_file_cache(page); |
535 | lru_cache_add_lru(page, lru); |
536 | } else { |
537 | /* |
538 | * Put unevictable pages directly on zone's unevictable |
539 | * list. |
540 | */ |
541 | lru = LRU_UNEVICTABLE; |
542 | add_page_to_unevictable_list(page); |
543 | } |
544 | |
545 | /* |
546 | * page's status can change while we move it among lru. If an evictable |
547 | * page is on unevictable list, it never be freed. To avoid that, |
548 | * check after we added it to the list, again. |
549 | */ |
550 | if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { |
551 | if (!isolate_lru_page(page)) { |
552 | put_page(page); |
553 | goto redo; |
554 | } |
555 | /* This means someone else dropped this page from LRU |
556 | * So, it will be freed or putback to LRU again. There is |
557 | * nothing to do here. |
558 | */ |
559 | } |
560 | |
561 | if (was_unevictable && lru != LRU_UNEVICTABLE) |
562 | count_vm_event(UNEVICTABLE_PGRESCUED); |
563 | else if (!was_unevictable && lru == LRU_UNEVICTABLE) |
564 | count_vm_event(UNEVICTABLE_PGCULLED); |
565 | |
566 | put_page(page); /* drop ref from isolate */ |
567 | } |
568 | |
569 | /* |
570 | * shrink_page_list() returns the number of reclaimed pages |
571 | */ |
572 | static unsigned long shrink_page_list(struct list_head *page_list, |
573 | struct scan_control *sc, |
574 | enum pageout_io sync_writeback) |
575 | { |
576 | LIST_HEAD(ret_pages); |
577 | struct pagevec freed_pvec; |
578 | int pgactivate = 0; |
579 | unsigned long nr_reclaimed = 0; |
580 | unsigned long vm_flags; |
581 | |
582 | cond_resched(); |
583 | |
584 | pagevec_init(&freed_pvec, 1); |
585 | while (!list_empty(page_list)) { |
586 | struct address_space *mapping; |
587 | struct page *page; |
588 | int may_enter_fs; |
589 | int referenced; |
590 | |
591 | cond_resched(); |
592 | |
593 | page = lru_to_page(page_list); |
594 | list_del(&page->lru); |
595 | |
596 | if (!trylock_page(page)) |
597 | goto keep; |
598 | |
599 | VM_BUG_ON(PageActive(page)); |
600 | |
601 | sc->nr_scanned++; |
602 | |
603 | if (unlikely(!page_evictable(page, NULL))) |
604 | goto cull_mlocked; |
605 | |
606 | if (!sc->may_unmap && page_mapped(page)) |
607 | goto keep_locked; |
608 | |
609 | /* Double the slab pressure for mapped and swapcache pages */ |
610 | if (page_mapped(page) || PageSwapCache(page)) |
611 | sc->nr_scanned++; |
612 | |
613 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || |
614 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); |
615 | |
616 | if (PageWriteback(page)) { |
617 | /* |
618 | * Synchronous reclaim is performed in two passes, |
619 | * first an asynchronous pass over the list to |
620 | * start parallel writeback, and a second synchronous |
621 | * pass to wait for the IO to complete. Wait here |
622 | * for any page for which writeback has already |
623 | * started. |
624 | */ |
625 | if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs) |
626 | wait_on_page_writeback(page); |
627 | else |
628 | goto keep_locked; |
629 | } |
630 | |
631 | referenced = page_referenced(page, 1, |
632 | sc->mem_cgroup, &vm_flags); |
633 | /* |
634 | * In active use or really unfreeable? Activate it. |
635 | * If page which have PG_mlocked lost isoltation race, |
636 | * try_to_unmap moves it to unevictable list |
637 | */ |
638 | if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && |
639 | referenced && page_mapping_inuse(page) |
640 | && !(vm_flags & VM_LOCKED)) |
641 | goto activate_locked; |
642 | |
643 | /* |
644 | * Anonymous process memory has backing store? |
645 | * Try to allocate it some swap space here. |
646 | */ |
647 | if (PageAnon(page) && !PageSwapCache(page)) { |
648 | if (!(sc->gfp_mask & __GFP_IO)) |
649 | goto keep_locked; |
650 | if (!add_to_swap(page)) |
651 | goto activate_locked; |
652 | may_enter_fs = 1; |
653 | } |
654 | |
655 | mapping = page_mapping(page); |
656 | |
657 | /* |
658 | * The page is mapped into the page tables of one or more |
659 | * processes. Try to unmap it here. |
660 | */ |
661 | if (page_mapped(page) && mapping) { |
662 | switch (try_to_unmap(page, 0)) { |
663 | case SWAP_FAIL: |
664 | goto activate_locked; |
665 | case SWAP_AGAIN: |
666 | goto keep_locked; |
667 | case SWAP_MLOCK: |
668 | goto cull_mlocked; |
669 | case SWAP_SUCCESS: |
670 | ; /* try to free the page below */ |
671 | } |
672 | } |
673 | |
674 | if (PageDirty(page)) { |
675 | if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced) |
676 | goto keep_locked; |
677 | if (!may_enter_fs) |
678 | goto keep_locked; |
679 | if (!sc->may_writepage) |
680 | goto keep_locked; |
681 | |
682 | /* Page is dirty, try to write it out here */ |
683 | switch (pageout(page, mapping, sync_writeback)) { |
684 | case PAGE_KEEP: |
685 | goto keep_locked; |
686 | case PAGE_ACTIVATE: |
687 | goto activate_locked; |
688 | case PAGE_SUCCESS: |
689 | if (PageWriteback(page) || PageDirty(page)) |
690 | goto keep; |
691 | /* |
692 | * A synchronous write - probably a ramdisk. Go |
693 | * ahead and try to reclaim the page. |
694 | */ |
695 | if (!trylock_page(page)) |
696 | goto keep; |
697 | if (PageDirty(page) || PageWriteback(page)) |
698 | goto keep_locked; |
699 | mapping = page_mapping(page); |
700 | case PAGE_CLEAN: |
701 | ; /* try to free the page below */ |
702 | } |
703 | } |
704 | |
705 | /* |
706 | * If the page has buffers, try to free the buffer mappings |
707 | * associated with this page. If we succeed we try to free |
708 | * the page as well. |
709 | * |
710 | * We do this even if the page is PageDirty(). |
711 | * try_to_release_page() does not perform I/O, but it is |
712 | * possible for a page to have PageDirty set, but it is actually |
713 | * clean (all its buffers are clean). This happens if the |
714 | * buffers were written out directly, with submit_bh(). ext3 |
715 | * will do this, as well as the blockdev mapping. |
716 | * try_to_release_page() will discover that cleanness and will |
717 | * drop the buffers and mark the page clean - it can be freed. |
718 | * |
719 | * Rarely, pages can have buffers and no ->mapping. These are |
720 | * the pages which were not successfully invalidated in |
721 | * truncate_complete_page(). We try to drop those buffers here |
722 | * and if that worked, and the page is no longer mapped into |
723 | * process address space (page_count == 1) it can be freed. |
724 | * Otherwise, leave the page on the LRU so it is swappable. |
725 | */ |
726 | if (page_has_private(page)) { |
727 | if (!try_to_release_page(page, sc->gfp_mask)) |
728 | goto activate_locked; |
729 | if (!mapping && page_count(page) == 1) { |
730 | unlock_page(page); |
731 | if (put_page_testzero(page)) |
732 | goto free_it; |
733 | else { |
734 | /* |
735 | * rare race with speculative reference. |
736 | * the speculative reference will free |
737 | * this page shortly, so we may |
738 | * increment nr_reclaimed here (and |
739 | * leave it off the LRU). |
740 | */ |
741 | nr_reclaimed++; |
742 | continue; |
743 | } |
744 | } |
745 | } |
746 | |
747 | if (!mapping || !__remove_mapping(mapping, page)) |
748 | goto keep_locked; |
749 | |
750 | /* |
751 | * At this point, we have no other references and there is |
752 | * no way to pick any more up (removed from LRU, removed |
753 | * from pagecache). Can use non-atomic bitops now (and |
754 | * we obviously don't have to worry about waking up a process |
755 | * waiting on the page lock, because there are no references. |
756 | */ |
757 | __clear_page_locked(page); |
758 | free_it: |
759 | nr_reclaimed++; |
760 | if (!pagevec_add(&freed_pvec, page)) { |
761 | __pagevec_free(&freed_pvec); |
762 | pagevec_reinit(&freed_pvec); |
763 | } |
764 | continue; |
765 | |
766 | cull_mlocked: |
767 | if (PageSwapCache(page)) |
768 | try_to_free_swap(page); |
769 | unlock_page(page); |
770 | putback_lru_page(page); |
771 | continue; |
772 | |
773 | activate_locked: |
774 | /* Not a candidate for swapping, so reclaim swap space. */ |
775 | if (PageSwapCache(page) && vm_swap_full()) |
776 | try_to_free_swap(page); |
777 | VM_BUG_ON(PageActive(page)); |
778 | SetPageActive(page); |
779 | pgactivate++; |
780 | keep_locked: |
781 | unlock_page(page); |
782 | keep: |
783 | list_add(&page->lru, &ret_pages); |
784 | VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); |
785 | } |
786 | list_splice(&ret_pages, page_list); |
787 | if (pagevec_count(&freed_pvec)) |
788 | __pagevec_free(&freed_pvec); |
789 | count_vm_events(PGACTIVATE, pgactivate); |
790 | return nr_reclaimed; |
791 | } |
792 | |
793 | /* LRU Isolation modes. */ |
794 | #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */ |
795 | #define ISOLATE_ACTIVE 1 /* Isolate active pages. */ |
796 | #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */ |
797 | |
798 | /* |
799 | * Attempt to remove the specified page from its LRU. Only take this page |
800 | * if it is of the appropriate PageActive status. Pages which are being |
801 | * freed elsewhere are also ignored. |
802 | * |
803 | * page: page to consider |
804 | * mode: one of the LRU isolation modes defined above |
805 | * |
806 | * returns 0 on success, -ve errno on failure. |
807 | */ |
808 | int __isolate_lru_page(struct page *page, int mode, int file) |
809 | { |
810 | int ret = -EINVAL; |
811 | |
812 | /* Only take pages on the LRU. */ |
813 | if (!PageLRU(page)) |
814 | return ret; |
815 | |
816 | /* |
817 | * When checking the active state, we need to be sure we are |
818 | * dealing with comparible boolean values. Take the logical not |
819 | * of each. |
820 | */ |
821 | if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) |
822 | return ret; |
823 | |
824 | if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file)) |
825 | return ret; |
826 | |
827 | /* |
828 | * When this function is being called for lumpy reclaim, we |
829 | * initially look into all LRU pages, active, inactive and |
830 | * unevictable; only give shrink_page_list evictable pages. |
831 | */ |
832 | if (PageUnevictable(page)) |
833 | return ret; |
834 | |
835 | ret = -EBUSY; |
836 | |
837 | if (likely(get_page_unless_zero(page))) { |
838 | /* |
839 | * Be careful not to clear PageLRU until after we're |
840 | * sure the page is not being freed elsewhere -- the |
841 | * page release code relies on it. |
842 | */ |
843 | ClearPageLRU(page); |
844 | ret = 0; |
845 | } |
846 | |
847 | return ret; |
848 | } |
849 | |
850 | /* |
851 | * zone->lru_lock is heavily contended. Some of the functions that |
852 | * shrink the lists perform better by taking out a batch of pages |
853 | * and working on them outside the LRU lock. |
854 | * |
855 | * For pagecache intensive workloads, this function is the hottest |
856 | * spot in the kernel (apart from copy_*_user functions). |
857 | * |
858 | * Appropriate locks must be held before calling this function. |
859 | * |
860 | * @nr_to_scan: The number of pages to look through on the list. |
861 | * @src: The LRU list to pull pages off. |
862 | * @dst: The temp list to put pages on to. |
863 | * @scanned: The number of pages that were scanned. |
864 | * @order: The caller's attempted allocation order |
865 | * @mode: One of the LRU isolation modes |
866 | * @file: True [1] if isolating file [!anon] pages |
867 | * |
868 | * returns how many pages were moved onto *@dst. |
869 | */ |
870 | static unsigned long isolate_lru_pages(unsigned long nr_to_scan, |
871 | struct list_head *src, struct list_head *dst, |
872 | unsigned long *scanned, int order, int mode, int file) |
873 | { |
874 | unsigned long nr_taken = 0; |
875 | unsigned long scan; |
876 | |
877 | for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { |
878 | struct page *page; |
879 | unsigned long pfn; |
880 | unsigned long end_pfn; |
881 | unsigned long page_pfn; |
882 | int zone_id; |
883 | |
884 | page = lru_to_page(src); |
885 | prefetchw_prev_lru_page(page, src, flags); |
886 | |
887 | VM_BUG_ON(!PageLRU(page)); |
888 | |
889 | switch (__isolate_lru_page(page, mode, file)) { |
890 | case 0: |
891 | list_move(&page->lru, dst); |
892 | mem_cgroup_del_lru(page); |
893 | nr_taken++; |
894 | break; |
895 | |
896 | case -EBUSY: |
897 | /* else it is being freed elsewhere */ |
898 | list_move(&page->lru, src); |
899 | mem_cgroup_rotate_lru_list(page, page_lru(page)); |
900 | continue; |
901 | |
902 | default: |
903 | BUG(); |
904 | } |
905 | |
906 | if (!order) |
907 | continue; |
908 | |
909 | /* |
910 | * Attempt to take all pages in the order aligned region |
911 | * surrounding the tag page. Only take those pages of |
912 | * the same active state as that tag page. We may safely |
913 | * round the target page pfn down to the requested order |
914 | * as the mem_map is guarenteed valid out to MAX_ORDER, |
915 | * where that page is in a different zone we will detect |
916 | * it from its zone id and abort this block scan. |
917 | */ |
918 | zone_id = page_zone_id(page); |
919 | page_pfn = page_to_pfn(page); |
920 | pfn = page_pfn & ~((1 << order) - 1); |
921 | end_pfn = pfn + (1 << order); |
922 | for (; pfn < end_pfn; pfn++) { |
923 | struct page *cursor_page; |
924 | |
925 | /* The target page is in the block, ignore it. */ |
926 | if (unlikely(pfn == page_pfn)) |
927 | continue; |
928 | |
929 | /* Avoid holes within the zone. */ |
930 | if (unlikely(!pfn_valid_within(pfn))) |
931 | break; |
932 | |
933 | cursor_page = pfn_to_page(pfn); |
934 | |
935 | /* Check that we have not crossed a zone boundary. */ |
936 | if (unlikely(page_zone_id(cursor_page) != zone_id)) |
937 | continue; |
938 | if (__isolate_lru_page(cursor_page, mode, file) == 0) { |
939 | list_move(&cursor_page->lru, dst); |
940 | mem_cgroup_del_lru(cursor_page); |
941 | nr_taken++; |
942 | scan++; |
943 | } |
944 | } |
945 | } |
946 | |
947 | *scanned = scan; |
948 | return nr_taken; |
949 | } |
950 | |
951 | static unsigned long isolate_pages_global(unsigned long nr, |
952 | struct list_head *dst, |
953 | unsigned long *scanned, int order, |
954 | int mode, struct zone *z, |
955 | struct mem_cgroup *mem_cont, |
956 | int active, int file) |
957 | { |
958 | int lru = LRU_BASE; |
959 | if (active) |
960 | lru += LRU_ACTIVE; |
961 | if (file) |
962 | lru += LRU_FILE; |
963 | return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, |
964 | mode, !!file); |
965 | } |
966 | |
967 | /* |
968 | * clear_active_flags() is a helper for shrink_active_list(), clearing |
969 | * any active bits from the pages in the list. |
970 | */ |
971 | static unsigned long clear_active_flags(struct list_head *page_list, |
972 | unsigned int *count) |
973 | { |
974 | int nr_active = 0; |
975 | int lru; |
976 | struct page *page; |
977 | |
978 | list_for_each_entry(page, page_list, lru) { |
979 | lru = page_is_file_cache(page); |
980 | if (PageActive(page)) { |
981 | lru += LRU_ACTIVE; |
982 | ClearPageActive(page); |
983 | nr_active++; |
984 | } |
985 | count[lru]++; |
986 | } |
987 | |
988 | return nr_active; |
989 | } |
990 | |
991 | /** |
992 | * isolate_lru_page - tries to isolate a page from its LRU list |
993 | * @page: page to isolate from its LRU list |
994 | * |
995 | * Isolates a @page from an LRU list, clears PageLRU and adjusts the |
996 | * vmstat statistic corresponding to whatever LRU list the page was on. |
997 | * |
998 | * Returns 0 if the page was removed from an LRU list. |
999 | * Returns -EBUSY if the page was not on an LRU list. |
1000 | * |
1001 | * The returned page will have PageLRU() cleared. If it was found on |
1002 | * the active list, it will have PageActive set. If it was found on |
1003 | * the unevictable list, it will have the PageUnevictable bit set. That flag |
1004 | * may need to be cleared by the caller before letting the page go. |
1005 | * |
1006 | * The vmstat statistic corresponding to the list on which the page was |
1007 | * found will be decremented. |
1008 | * |
1009 | * Restrictions: |
1010 | * (1) Must be called with an elevated refcount on the page. This is a |
1011 | * fundamentnal difference from isolate_lru_pages (which is called |
1012 | * without a stable reference). |
1013 | * (2) the lru_lock must not be held. |
1014 | * (3) interrupts must be enabled. |
1015 | */ |
1016 | int isolate_lru_page(struct page *page) |
1017 | { |
1018 | int ret = -EBUSY; |
1019 | |
1020 | if (PageLRU(page)) { |
1021 | struct zone *zone = page_zone(page); |
1022 | |
1023 | spin_lock_irq(&zone->lru_lock); |
1024 | if (PageLRU(page) && get_page_unless_zero(page)) { |
1025 | int lru = page_lru(page); |
1026 | ret = 0; |
1027 | ClearPageLRU(page); |
1028 | |
1029 | del_page_from_lru_list(zone, page, lru); |
1030 | } |
1031 | spin_unlock_irq(&zone->lru_lock); |
1032 | } |
1033 | return ret; |
1034 | } |
1035 | |
1036 | /* |
1037 | * shrink_inactive_list() is a helper for shrink_zone(). It returns the number |
1038 | * of reclaimed pages |
1039 | */ |
1040 | static unsigned long shrink_inactive_list(unsigned long max_scan, |
1041 | struct zone *zone, struct scan_control *sc, |
1042 | int priority, int file) |
1043 | { |
1044 | LIST_HEAD(page_list); |
1045 | struct pagevec pvec; |
1046 | unsigned long nr_scanned = 0; |
1047 | unsigned long nr_reclaimed = 0; |
1048 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
1049 | int lumpy_reclaim = 0; |
1050 | |
1051 | /* |
1052 | * If we need a large contiguous chunk of memory, or have |
1053 | * trouble getting a small set of contiguous pages, we |
1054 | * will reclaim both active and inactive pages. |
1055 | * |
1056 | * We use the same threshold as pageout congestion_wait below. |
1057 | */ |
1058 | if (sc->order > PAGE_ALLOC_COSTLY_ORDER) |
1059 | lumpy_reclaim = 1; |
1060 | else if (sc->order && priority < DEF_PRIORITY - 2) |
1061 | lumpy_reclaim = 1; |
1062 | |
1063 | pagevec_init(&pvec, 1); |
1064 | |
1065 | lru_add_drain(); |
1066 | spin_lock_irq(&zone->lru_lock); |
1067 | do { |
1068 | struct page *page; |
1069 | unsigned long nr_taken; |
1070 | unsigned long nr_scan; |
1071 | unsigned long nr_freed; |
1072 | unsigned long nr_active; |
1073 | unsigned int count[NR_LRU_LISTS] = { 0, }; |
1074 | int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE; |
1075 | |
1076 | nr_taken = sc->isolate_pages(sc->swap_cluster_max, |
1077 | &page_list, &nr_scan, sc->order, mode, |
1078 | zone, sc->mem_cgroup, 0, file); |
1079 | nr_active = clear_active_flags(&page_list, count); |
1080 | __count_vm_events(PGDEACTIVATE, nr_active); |
1081 | |
1082 | __mod_zone_page_state(zone, NR_ACTIVE_FILE, |
1083 | -count[LRU_ACTIVE_FILE]); |
1084 | __mod_zone_page_state(zone, NR_INACTIVE_FILE, |
1085 | -count[LRU_INACTIVE_FILE]); |
1086 | __mod_zone_page_state(zone, NR_ACTIVE_ANON, |
1087 | -count[LRU_ACTIVE_ANON]); |
1088 | __mod_zone_page_state(zone, NR_INACTIVE_ANON, |
1089 | -count[LRU_INACTIVE_ANON]); |
1090 | |
1091 | if (scanning_global_lru(sc)) |
1092 | zone->pages_scanned += nr_scan; |
1093 | |
1094 | reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON]; |
1095 | reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON]; |
1096 | reclaim_stat->recent_scanned[1] += count[LRU_INACTIVE_FILE]; |
1097 | reclaim_stat->recent_scanned[1] += count[LRU_ACTIVE_FILE]; |
1098 | |
1099 | spin_unlock_irq(&zone->lru_lock); |
1100 | |
1101 | nr_scanned += nr_scan; |
1102 | nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC); |
1103 | |
1104 | /* |
1105 | * If we are direct reclaiming for contiguous pages and we do |
1106 | * not reclaim everything in the list, try again and wait |
1107 | * for IO to complete. This will stall high-order allocations |
1108 | * but that should be acceptable to the caller |
1109 | */ |
1110 | if (nr_freed < nr_taken && !current_is_kswapd() && |
1111 | lumpy_reclaim) { |
1112 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
1113 | |
1114 | /* |
1115 | * The attempt at page out may have made some |
1116 | * of the pages active, mark them inactive again. |
1117 | */ |
1118 | nr_active = clear_active_flags(&page_list, count); |
1119 | count_vm_events(PGDEACTIVATE, nr_active); |
1120 | |
1121 | nr_freed += shrink_page_list(&page_list, sc, |
1122 | PAGEOUT_IO_SYNC); |
1123 | } |
1124 | |
1125 | nr_reclaimed += nr_freed; |
1126 | local_irq_disable(); |
1127 | if (current_is_kswapd()) { |
1128 | __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan); |
1129 | __count_vm_events(KSWAPD_STEAL, nr_freed); |
1130 | } else if (scanning_global_lru(sc)) |
1131 | __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan); |
1132 | |
1133 | __count_zone_vm_events(PGSTEAL, zone, nr_freed); |
1134 | |
1135 | if (nr_taken == 0) |
1136 | goto done; |
1137 | |
1138 | spin_lock(&zone->lru_lock); |
1139 | /* |
1140 | * Put back any unfreeable pages. |
1141 | */ |
1142 | while (!list_empty(&page_list)) { |
1143 | int lru; |
1144 | page = lru_to_page(&page_list); |
1145 | VM_BUG_ON(PageLRU(page)); |
1146 | list_del(&page->lru); |
1147 | if (unlikely(!page_evictable(page, NULL))) { |
1148 | spin_unlock_irq(&zone->lru_lock); |
1149 | putback_lru_page(page); |
1150 | spin_lock_irq(&zone->lru_lock); |
1151 | continue; |
1152 | } |
1153 | SetPageLRU(page); |
1154 | lru = page_lru(page); |
1155 | add_page_to_lru_list(zone, page, lru); |
1156 | if (PageActive(page)) { |
1157 | int file = !!page_is_file_cache(page); |
1158 | reclaim_stat->recent_rotated[file]++; |
1159 | } |
1160 | if (!pagevec_add(&pvec, page)) { |
1161 | spin_unlock_irq(&zone->lru_lock); |
1162 | __pagevec_release(&pvec); |
1163 | spin_lock_irq(&zone->lru_lock); |
1164 | } |
1165 | } |
1166 | } while (nr_scanned < max_scan); |
1167 | spin_unlock(&zone->lru_lock); |
1168 | done: |
1169 | local_irq_enable(); |
1170 | pagevec_release(&pvec); |
1171 | return nr_reclaimed; |
1172 | } |
1173 | |
1174 | /* |
1175 | * We are about to scan this zone at a certain priority level. If that priority |
1176 | * level is smaller (ie: more urgent) than the previous priority, then note |
1177 | * that priority level within the zone. This is done so that when the next |
1178 | * process comes in to scan this zone, it will immediately start out at this |
1179 | * priority level rather than having to build up its own scanning priority. |
1180 | * Here, this priority affects only the reclaim-mapped threshold. |
1181 | */ |
1182 | static inline void note_zone_scanning_priority(struct zone *zone, int priority) |
1183 | { |
1184 | if (priority < zone->prev_priority) |
1185 | zone->prev_priority = priority; |
1186 | } |
1187 | |
1188 | /* |
1189 | * This moves pages from the active list to the inactive list. |
1190 | * |
1191 | * We move them the other way if the page is referenced by one or more |
1192 | * processes, from rmap. |
1193 | * |
1194 | * If the pages are mostly unmapped, the processing is fast and it is |
1195 | * appropriate to hold zone->lru_lock across the whole operation. But if |
1196 | * the pages are mapped, the processing is slow (page_referenced()) so we |
1197 | * should drop zone->lru_lock around each page. It's impossible to balance |
1198 | * this, so instead we remove the pages from the LRU while processing them. |
1199 | * It is safe to rely on PG_active against the non-LRU pages in here because |
1200 | * nobody will play with that bit on a non-LRU page. |
1201 | * |
1202 | * The downside is that we have to touch page->_count against each page. |
1203 | * But we had to alter page->flags anyway. |
1204 | */ |
1205 | |
1206 | static void move_active_pages_to_lru(struct zone *zone, |
1207 | struct list_head *list, |
1208 | enum lru_list lru) |
1209 | { |
1210 | unsigned long pgmoved = 0; |
1211 | struct pagevec pvec; |
1212 | struct page *page; |
1213 | |
1214 | pagevec_init(&pvec, 1); |
1215 | |
1216 | while (!list_empty(list)) { |
1217 | page = lru_to_page(list); |
1218 | prefetchw_prev_lru_page(page, list, flags); |
1219 | |
1220 | VM_BUG_ON(PageLRU(page)); |
1221 | SetPageLRU(page); |
1222 | |
1223 | VM_BUG_ON(!PageActive(page)); |
1224 | if (!is_active_lru(lru)) |
1225 | ClearPageActive(page); /* we are de-activating */ |
1226 | |
1227 | list_move(&page->lru, &zone->lru[lru].list); |
1228 | mem_cgroup_add_lru_list(page, lru); |
1229 | pgmoved++; |
1230 | |
1231 | if (!pagevec_add(&pvec, page) || list_empty(list)) { |
1232 | spin_unlock_irq(&zone->lru_lock); |
1233 | if (buffer_heads_over_limit) |
1234 | pagevec_strip(&pvec); |
1235 | __pagevec_release(&pvec); |
1236 | spin_lock_irq(&zone->lru_lock); |
1237 | } |
1238 | } |
1239 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); |
1240 | if (!is_active_lru(lru)) |
1241 | __count_vm_events(PGDEACTIVATE, pgmoved); |
1242 | } |
1243 | |
1244 | static void shrink_active_list(unsigned long nr_pages, struct zone *zone, |
1245 | struct scan_control *sc, int priority, int file) |
1246 | { |
1247 | unsigned long pgmoved; |
1248 | unsigned long pgscanned; |
1249 | unsigned long vm_flags; |
1250 | LIST_HEAD(l_hold); /* The pages which were snipped off */ |
1251 | LIST_HEAD(l_active); |
1252 | LIST_HEAD(l_inactive); |
1253 | struct page *page; |
1254 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
1255 | |
1256 | lru_add_drain(); |
1257 | spin_lock_irq(&zone->lru_lock); |
1258 | pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order, |
1259 | ISOLATE_ACTIVE, zone, |
1260 | sc->mem_cgroup, 1, file); |
1261 | /* |
1262 | * zone->pages_scanned is used for detect zone's oom |
1263 | * mem_cgroup remembers nr_scan by itself. |
1264 | */ |
1265 | if (scanning_global_lru(sc)) { |
1266 | zone->pages_scanned += pgscanned; |
1267 | } |
1268 | reclaim_stat->recent_scanned[!!file] += pgmoved; |
1269 | |
1270 | __count_zone_vm_events(PGREFILL, zone, pgscanned); |
1271 | if (file) |
1272 | __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved); |
1273 | else |
1274 | __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved); |
1275 | spin_unlock_irq(&zone->lru_lock); |
1276 | |
1277 | pgmoved = 0; /* count referenced (mapping) mapped pages */ |
1278 | while (!list_empty(&l_hold)) { |
1279 | cond_resched(); |
1280 | page = lru_to_page(&l_hold); |
1281 | list_del(&page->lru); |
1282 | |
1283 | if (unlikely(!page_evictable(page, NULL))) { |
1284 | putback_lru_page(page); |
1285 | continue; |
1286 | } |
1287 | |
1288 | /* page_referenced clears PageReferenced */ |
1289 | if (page_mapping_inuse(page) && |
1290 | page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { |
1291 | pgmoved++; |
1292 | /* |
1293 | * Identify referenced, file-backed active pages and |
1294 | * give them one more trip around the active list. So |
1295 | * that executable code get better chances to stay in |
1296 | * memory under moderate memory pressure. Anon pages |
1297 | * are not likely to be evicted by use-once streaming |
1298 | * IO, plus JVM can create lots of anon VM_EXEC pages, |
1299 | * so we ignore them here. |
1300 | */ |
1301 | if ((vm_flags & VM_EXEC) && !PageAnon(page)) { |
1302 | list_add(&page->lru, &l_active); |
1303 | continue; |
1304 | } |
1305 | } |
1306 | |
1307 | list_add(&page->lru, &l_inactive); |
1308 | } |
1309 | |
1310 | /* |
1311 | * Move pages back to the lru list. |
1312 | */ |
1313 | spin_lock_irq(&zone->lru_lock); |
1314 | /* |
1315 | * Count referenced pages from currently used mappings as rotated, |
1316 | * even though only some of them are actually re-activated. This |
1317 | * helps balance scan pressure between file and anonymous pages in |
1318 | * get_scan_ratio. |
1319 | */ |
1320 | reclaim_stat->recent_rotated[!!file] += pgmoved; |
1321 | |
1322 | move_active_pages_to_lru(zone, &l_active, |
1323 | LRU_ACTIVE + file * LRU_FILE); |
1324 | move_active_pages_to_lru(zone, &l_inactive, |
1325 | LRU_BASE + file * LRU_FILE); |
1326 | |
1327 | spin_unlock_irq(&zone->lru_lock); |
1328 | } |
1329 | |
1330 | static int inactive_anon_is_low_global(struct zone *zone) |
1331 | { |
1332 | unsigned long active, inactive; |
1333 | |
1334 | active = zone_page_state(zone, NR_ACTIVE_ANON); |
1335 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
1336 | |
1337 | if (inactive * zone->inactive_ratio < active) |
1338 | return 1; |
1339 | |
1340 | return 0; |
1341 | } |
1342 | |
1343 | /** |
1344 | * inactive_anon_is_low - check if anonymous pages need to be deactivated |
1345 | * @zone: zone to check |
1346 | * @sc: scan control of this context |
1347 | * |
1348 | * Returns true if the zone does not have enough inactive anon pages, |
1349 | * meaning some active anon pages need to be deactivated. |
1350 | */ |
1351 | static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) |
1352 | { |
1353 | int low; |
1354 | |
1355 | if (scanning_global_lru(sc)) |
1356 | low = inactive_anon_is_low_global(zone); |
1357 | else |
1358 | low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); |
1359 | return low; |
1360 | } |
1361 | |
1362 | static int inactive_file_is_low_global(struct zone *zone) |
1363 | { |
1364 | unsigned long active, inactive; |
1365 | |
1366 | active = zone_page_state(zone, NR_ACTIVE_FILE); |
1367 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); |
1368 | |
1369 | return (active > inactive); |
1370 | } |
1371 | |
1372 | /** |
1373 | * inactive_file_is_low - check if file pages need to be deactivated |
1374 | * @zone: zone to check |
1375 | * @sc: scan control of this context |
1376 | * |
1377 | * When the system is doing streaming IO, memory pressure here |
1378 | * ensures that active file pages get deactivated, until more |
1379 | * than half of the file pages are on the inactive list. |
1380 | * |
1381 | * Once we get to that situation, protect the system's working |
1382 | * set from being evicted by disabling active file page aging. |
1383 | * |
1384 | * This uses a different ratio than the anonymous pages, because |
1385 | * the page cache uses a use-once replacement algorithm. |
1386 | */ |
1387 | static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) |
1388 | { |
1389 | int low; |
1390 | |
1391 | if (scanning_global_lru(sc)) |
1392 | low = inactive_file_is_low_global(zone); |
1393 | else |
1394 | low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); |
1395 | return low; |
1396 | } |
1397 | |
1398 | static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, |
1399 | struct zone *zone, struct scan_control *sc, int priority) |
1400 | { |
1401 | int file = is_file_lru(lru); |
1402 | |
1403 | if (lru == LRU_ACTIVE_FILE && inactive_file_is_low(zone, sc)) { |
1404 | shrink_active_list(nr_to_scan, zone, sc, priority, file); |
1405 | return 0; |
1406 | } |
1407 | |
1408 | if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) { |
1409 | shrink_active_list(nr_to_scan, zone, sc, priority, file); |
1410 | return 0; |
1411 | } |
1412 | return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); |
1413 | } |
1414 | |
1415 | /* |
1416 | * Determine how aggressively the anon and file LRU lists should be |
1417 | * scanned. The relative value of each set of LRU lists is determined |
1418 | * by looking at the fraction of the pages scanned we did rotate back |
1419 | * onto the active list instead of evict. |
1420 | * |
1421 | * percent[0] specifies how much pressure to put on ram/swap backed |
1422 | * memory, while percent[1] determines pressure on the file LRUs. |
1423 | */ |
1424 | static void get_scan_ratio(struct zone *zone, struct scan_control *sc, |
1425 | unsigned long *percent) |
1426 | { |
1427 | unsigned long anon, file, free; |
1428 | unsigned long anon_prio, file_prio; |
1429 | unsigned long ap, fp; |
1430 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
1431 | |
1432 | anon = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) + |
1433 | zone_nr_pages(zone, sc, LRU_INACTIVE_ANON); |
1434 | file = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) + |
1435 | zone_nr_pages(zone, sc, LRU_INACTIVE_FILE); |
1436 | |
1437 | if (scanning_global_lru(sc)) { |
1438 | free = zone_page_state(zone, NR_FREE_PAGES); |
1439 | /* If we have very few page cache pages, |
1440 | force-scan anon pages. */ |
1441 | if (unlikely(file + free <= high_wmark_pages(zone))) { |
1442 | percent[0] = 100; |
1443 | percent[1] = 0; |
1444 | return; |
1445 | } |
1446 | } |
1447 | |
1448 | /* |
1449 | * OK, so we have swap space and a fair amount of page cache |
1450 | * pages. We use the recently rotated / recently scanned |
1451 | * ratios to determine how valuable each cache is. |
1452 | * |
1453 | * Because workloads change over time (and to avoid overflow) |
1454 | * we keep these statistics as a floating average, which ends |
1455 | * up weighing recent references more than old ones. |
1456 | * |
1457 | * anon in [0], file in [1] |
1458 | */ |
1459 | if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { |
1460 | spin_lock_irq(&zone->lru_lock); |
1461 | reclaim_stat->recent_scanned[0] /= 2; |
1462 | reclaim_stat->recent_rotated[0] /= 2; |
1463 | spin_unlock_irq(&zone->lru_lock); |
1464 | } |
1465 | |
1466 | if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { |
1467 | spin_lock_irq(&zone->lru_lock); |
1468 | reclaim_stat->recent_scanned[1] /= 2; |
1469 | reclaim_stat->recent_rotated[1] /= 2; |
1470 | spin_unlock_irq(&zone->lru_lock); |
1471 | } |
1472 | |
1473 | /* |
1474 | * With swappiness at 100, anonymous and file have the same priority. |
1475 | * This scanning priority is essentially the inverse of IO cost. |
1476 | */ |
1477 | anon_prio = sc->swappiness; |
1478 | file_prio = 200 - sc->swappiness; |
1479 | |
1480 | /* |
1481 | * The amount of pressure on anon vs file pages is inversely |
1482 | * proportional to the fraction of recently scanned pages on |
1483 | * each list that were recently referenced and in active use. |
1484 | */ |
1485 | ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); |
1486 | ap /= reclaim_stat->recent_rotated[0] + 1; |
1487 | |
1488 | fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); |
1489 | fp /= reclaim_stat->recent_rotated[1] + 1; |
1490 | |
1491 | /* Normalize to percentages */ |
1492 | percent[0] = 100 * ap / (ap + fp + 1); |
1493 | percent[1] = 100 - percent[0]; |
1494 | } |
1495 | |
1496 | /* |
1497 | * Smallish @nr_to_scan's are deposited in @nr_saved_scan, |
1498 | * until we collected @swap_cluster_max pages to scan. |
1499 | */ |
1500 | static unsigned long nr_scan_try_batch(unsigned long nr_to_scan, |
1501 | unsigned long *nr_saved_scan, |
1502 | unsigned long swap_cluster_max) |
1503 | { |
1504 | unsigned long nr; |
1505 | |
1506 | *nr_saved_scan += nr_to_scan; |
1507 | nr = *nr_saved_scan; |
1508 | |
1509 | if (nr >= swap_cluster_max) |
1510 | *nr_saved_scan = 0; |
1511 | else |
1512 | nr = 0; |
1513 | |
1514 | return nr; |
1515 | } |
1516 | |
1517 | /* |
1518 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. |
1519 | */ |
1520 | static void shrink_zone(int priority, struct zone *zone, |
1521 | struct scan_control *sc) |
1522 | { |
1523 | unsigned long nr[NR_LRU_LISTS]; |
1524 | unsigned long nr_to_scan; |
1525 | unsigned long percent[2]; /* anon @ 0; file @ 1 */ |
1526 | enum lru_list l; |
1527 | unsigned long nr_reclaimed = sc->nr_reclaimed; |
1528 | unsigned long swap_cluster_max = sc->swap_cluster_max; |
1529 | int noswap = 0; |
1530 | |
1531 | /* If we have no swap space, do not bother scanning anon pages. */ |
1532 | if (!sc->may_swap || (nr_swap_pages <= 0)) { |
1533 | noswap = 1; |
1534 | percent[0] = 0; |
1535 | percent[1] = 100; |
1536 | } else |
1537 | get_scan_ratio(zone, sc, percent); |
1538 | |
1539 | for_each_evictable_lru(l) { |
1540 | int file = is_file_lru(l); |
1541 | unsigned long scan; |
1542 | |
1543 | scan = zone_nr_pages(zone, sc, l); |
1544 | if (priority || noswap) { |
1545 | scan >>= priority; |
1546 | scan = (scan * percent[file]) / 100; |
1547 | } |
1548 | if (scanning_global_lru(sc)) |
1549 | nr[l] = nr_scan_try_batch(scan, |
1550 | &zone->lru[l].nr_saved_scan, |
1551 | swap_cluster_max); |
1552 | else |
1553 | nr[l] = scan; |
1554 | } |
1555 | |
1556 | while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || |
1557 | nr[LRU_INACTIVE_FILE]) { |
1558 | for_each_evictable_lru(l) { |
1559 | if (nr[l]) { |
1560 | nr_to_scan = min(nr[l], swap_cluster_max); |
1561 | nr[l] -= nr_to_scan; |
1562 | |
1563 | nr_reclaimed += shrink_list(l, nr_to_scan, |
1564 | zone, sc, priority); |
1565 | } |
1566 | } |
1567 | /* |
1568 | * On large memory systems, scan >> priority can become |
1569 | * really large. This is fine for the starting priority; |
1570 | * we want to put equal scanning pressure on each zone. |
1571 | * However, if the VM has a harder time of freeing pages, |
1572 | * with multiple processes reclaiming pages, the total |
1573 | * freeing target can get unreasonably large. |
1574 | */ |
1575 | if (nr_reclaimed > swap_cluster_max && |
1576 | priority < DEF_PRIORITY && !current_is_kswapd()) |
1577 | break; |
1578 | } |
1579 | |
1580 | sc->nr_reclaimed = nr_reclaimed; |
1581 | |
1582 | /* |
1583 | * Even if we did not try to evict anon pages at all, we want to |
1584 | * rebalance the anon lru active/inactive ratio. |
1585 | */ |
1586 | if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0) |
1587 | shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); |
1588 | |
1589 | throttle_vm_writeout(sc->gfp_mask); |
1590 | } |
1591 | |
1592 | /* |
1593 | * This is the direct reclaim path, for page-allocating processes. We only |
1594 | * try to reclaim pages from zones which will satisfy the caller's allocation |
1595 | * request. |
1596 | * |
1597 | * We reclaim from a zone even if that zone is over high_wmark_pages(zone). |
1598 | * Because: |
1599 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order |
1600 | * allocation or |
1601 | * b) The target zone may be at high_wmark_pages(zone) but the lower zones |
1602 | * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' |
1603 | * zone defense algorithm. |
1604 | * |
1605 | * If a zone is deemed to be full of pinned pages then just give it a light |
1606 | * scan then give up on it. |
1607 | */ |
1608 | static void shrink_zones(int priority, struct zonelist *zonelist, |
1609 | struct scan_control *sc) |
1610 | { |
1611 | enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask); |
1612 | struct zoneref *z; |
1613 | struct zone *zone; |
1614 | |
1615 | sc->all_unreclaimable = 1; |
1616 | for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx, |
1617 | sc->nodemask) { |
1618 | if (!populated_zone(zone)) |
1619 | continue; |
1620 | /* |
1621 | * Take care memory controller reclaiming has small influence |
1622 | * to global LRU. |
1623 | */ |
1624 | if (scanning_global_lru(sc)) { |
1625 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
1626 | continue; |
1627 | note_zone_scanning_priority(zone, priority); |
1628 | |
1629 | if (zone_is_all_unreclaimable(zone) && |
1630 | priority != DEF_PRIORITY) |
1631 | continue; /* Let kswapd poll it */ |
1632 | sc->all_unreclaimable = 0; |
1633 | } else { |
1634 | /* |
1635 | * Ignore cpuset limitation here. We just want to reduce |
1636 | * # of used pages by us regardless of memory shortage. |
1637 | */ |
1638 | sc->all_unreclaimable = 0; |
1639 | mem_cgroup_note_reclaim_priority(sc->mem_cgroup, |
1640 | priority); |
1641 | } |
1642 | |
1643 | shrink_zone(priority, zone, sc); |
1644 | } |
1645 | } |
1646 | |
1647 | /* |
1648 | * This is the main entry point to direct page reclaim. |
1649 | * |
1650 | * If a full scan of the inactive list fails to free enough memory then we |
1651 | * are "out of memory" and something needs to be killed. |
1652 | * |
1653 | * If the caller is !__GFP_FS then the probability of a failure is reasonably |
1654 | * high - the zone may be full of dirty or under-writeback pages, which this |
1655 | * caller can't do much about. We kick pdflush and take explicit naps in the |
1656 | * hope that some of these pages can be written. But if the allocating task |
1657 | * holds filesystem locks which prevent writeout this might not work, and the |
1658 | * allocation attempt will fail. |
1659 | * |
1660 | * returns: 0, if no pages reclaimed |
1661 | * else, the number of pages reclaimed |
1662 | */ |
1663 | static unsigned long do_try_to_free_pages(struct zonelist *zonelist, |
1664 | struct scan_control *sc) |
1665 | { |
1666 | int priority; |
1667 | unsigned long ret = 0; |
1668 | unsigned long total_scanned = 0; |
1669 | struct reclaim_state *reclaim_state = current->reclaim_state; |
1670 | unsigned long lru_pages = 0; |
1671 | struct zoneref *z; |
1672 | struct zone *zone; |
1673 | enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask); |
1674 | |
1675 | delayacct_freepages_start(); |
1676 | |
1677 | if (scanning_global_lru(sc)) |
1678 | count_vm_event(ALLOCSTALL); |
1679 | /* |
1680 | * mem_cgroup will not do shrink_slab. |
1681 | */ |
1682 | if (scanning_global_lru(sc)) { |
1683 | for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) { |
1684 | |
1685 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
1686 | continue; |
1687 | |
1688 | lru_pages += zone_lru_pages(zone); |
1689 | } |
1690 | } |
1691 | |
1692 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
1693 | sc->nr_scanned = 0; |
1694 | if (!priority) |
1695 | disable_swap_token(); |
1696 | shrink_zones(priority, zonelist, sc); |
1697 | /* |
1698 | * Don't shrink slabs when reclaiming memory from |
1699 | * over limit cgroups |
1700 | */ |
1701 | if (scanning_global_lru(sc)) { |
1702 | shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages); |
1703 | if (reclaim_state) { |
1704 | sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
1705 | reclaim_state->reclaimed_slab = 0; |
1706 | } |
1707 | } |
1708 | total_scanned += sc->nr_scanned; |
1709 | if (sc->nr_reclaimed >= sc->swap_cluster_max) { |
1710 | ret = sc->nr_reclaimed; |
1711 | goto out; |
1712 | } |
1713 | |
1714 | /* |
1715 | * Try to write back as many pages as we just scanned. This |
1716 | * tends to cause slow streaming writers to write data to the |
1717 | * disk smoothly, at the dirtying rate, which is nice. But |
1718 | * that's undesirable in laptop mode, where we *want* lumpy |
1719 | * writeout. So in laptop mode, write out the whole world. |
1720 | */ |
1721 | if (total_scanned > sc->swap_cluster_max + |
1722 | sc->swap_cluster_max / 2) { |
1723 | wakeup_pdflush(laptop_mode ? 0 : total_scanned); |
1724 | sc->may_writepage = 1; |
1725 | } |
1726 | |
1727 | /* Take a nap, wait for some writeback to complete */ |
1728 | if (sc->nr_scanned && priority < DEF_PRIORITY - 2) |
1729 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
1730 | } |
1731 | /* top priority shrink_zones still had more to do? don't OOM, then */ |
1732 | if (!sc->all_unreclaimable && scanning_global_lru(sc)) |
1733 | ret = sc->nr_reclaimed; |
1734 | out: |
1735 | /* |
1736 | * Now that we've scanned all the zones at this priority level, note |
1737 | * that level within the zone so that the next thread which performs |
1738 | * scanning of this zone will immediately start out at this priority |
1739 | * level. This affects only the decision whether or not to bring |
1740 | * mapped pages onto the inactive list. |
1741 | */ |
1742 | if (priority < 0) |
1743 | priority = 0; |
1744 | |
1745 | if (scanning_global_lru(sc)) { |
1746 | for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) { |
1747 | |
1748 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
1749 | continue; |
1750 | |
1751 | zone->prev_priority = priority; |
1752 | } |
1753 | } else |
1754 | mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority); |
1755 | |
1756 | delayacct_freepages_end(); |
1757 | |
1758 | return ret; |
1759 | } |
1760 | |
1761 | unsigned long try_to_free_pages(struct zonelist *zonelist, int order, |
1762 | gfp_t gfp_mask, nodemask_t *nodemask) |
1763 | { |
1764 | struct scan_control sc = { |
1765 | .gfp_mask = gfp_mask, |
1766 | .may_writepage = !laptop_mode, |
1767 | .swap_cluster_max = SWAP_CLUSTER_MAX, |
1768 | .may_unmap = 1, |
1769 | .may_swap = 1, |
1770 | .swappiness = vm_swappiness, |
1771 | .order = order, |
1772 | .mem_cgroup = NULL, |
1773 | .isolate_pages = isolate_pages_global, |
1774 | .nodemask = nodemask, |
1775 | }; |
1776 | |
1777 | return do_try_to_free_pages(zonelist, &sc); |
1778 | } |
1779 | |
1780 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
1781 | |
1782 | unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, |
1783 | gfp_t gfp_mask, |
1784 | bool noswap, |
1785 | unsigned int swappiness) |
1786 | { |
1787 | struct scan_control sc = { |
1788 | .may_writepage = !laptop_mode, |
1789 | .may_unmap = 1, |
1790 | .may_swap = !noswap, |
1791 | .swap_cluster_max = SWAP_CLUSTER_MAX, |
1792 | .swappiness = swappiness, |
1793 | .order = 0, |
1794 | .mem_cgroup = mem_cont, |
1795 | .isolate_pages = mem_cgroup_isolate_pages, |
1796 | .nodemask = NULL, /* we don't care the placement */ |
1797 | }; |
1798 | struct zonelist *zonelist; |
1799 | |
1800 | sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
1801 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); |
1802 | zonelist = NODE_DATA(numa_node_id())->node_zonelists; |
1803 | return do_try_to_free_pages(zonelist, &sc); |
1804 | } |
1805 | #endif |
1806 | |
1807 | /* |
1808 | * For kswapd, balance_pgdat() will work across all this node's zones until |
1809 | * they are all at high_wmark_pages(zone). |
1810 | * |
1811 | * Returns the number of pages which were actually freed. |
1812 | * |
1813 | * There is special handling here for zones which are full of pinned pages. |
1814 | * This can happen if the pages are all mlocked, or if they are all used by |
1815 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. |
1816 | * What we do is to detect the case where all pages in the zone have been |
1817 | * scanned twice and there has been zero successful reclaim. Mark the zone as |
1818 | * dead and from now on, only perform a short scan. Basically we're polling |
1819 | * the zone for when the problem goes away. |
1820 | * |
1821 | * kswapd scans the zones in the highmem->normal->dma direction. It skips |
1822 | * zones which have free_pages > high_wmark_pages(zone), but once a zone is |
1823 | * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the |
1824 | * lower zones regardless of the number of free pages in the lower zones. This |
1825 | * interoperates with the page allocator fallback scheme to ensure that aging |
1826 | * of pages is balanced across the zones. |
1827 | */ |
1828 | static unsigned long balance_pgdat(pg_data_t *pgdat, int order) |
1829 | { |
1830 | int all_zones_ok; |
1831 | int priority; |
1832 | int i; |
1833 | unsigned long total_scanned; |
1834 | struct reclaim_state *reclaim_state = current->reclaim_state; |
1835 | struct scan_control sc = { |
1836 | .gfp_mask = GFP_KERNEL, |
1837 | .may_unmap = 1, |
1838 | .may_swap = 1, |
1839 | .swap_cluster_max = SWAP_CLUSTER_MAX, |
1840 | .swappiness = vm_swappiness, |
1841 | .order = order, |
1842 | .mem_cgroup = NULL, |
1843 | .isolate_pages = isolate_pages_global, |
1844 | }; |
1845 | /* |
1846 | * temp_priority is used to remember the scanning priority at which |
1847 | * this zone was successfully refilled to |
1848 | * free_pages == high_wmark_pages(zone). |
1849 | */ |
1850 | int temp_priority[MAX_NR_ZONES]; |
1851 | |
1852 | loop_again: |
1853 | total_scanned = 0; |
1854 | sc.nr_reclaimed = 0; |
1855 | sc.may_writepage = !laptop_mode; |
1856 | count_vm_event(PAGEOUTRUN); |
1857 | |
1858 | for (i = 0; i < pgdat->nr_zones; i++) |
1859 | temp_priority[i] = DEF_PRIORITY; |
1860 | |
1861 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
1862 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ |
1863 | unsigned long lru_pages = 0; |
1864 | |
1865 | /* The swap token gets in the way of swapout... */ |
1866 | if (!priority) |
1867 | disable_swap_token(); |
1868 | |
1869 | all_zones_ok = 1; |
1870 | |
1871 | /* |
1872 | * Scan in the highmem->dma direction for the highest |
1873 | * zone which needs scanning |
1874 | */ |
1875 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { |
1876 | struct zone *zone = pgdat->node_zones + i; |
1877 | |
1878 | if (!populated_zone(zone)) |
1879 | continue; |
1880 | |
1881 | if (zone_is_all_unreclaimable(zone) && |
1882 | priority != DEF_PRIORITY) |
1883 | continue; |
1884 | |
1885 | /* |
1886 | * Do some background aging of the anon list, to give |
1887 | * pages a chance to be referenced before reclaiming. |
1888 | */ |
1889 | if (inactive_anon_is_low(zone, &sc)) |
1890 | shrink_active_list(SWAP_CLUSTER_MAX, zone, |
1891 | &sc, priority, 0); |
1892 | |
1893 | if (!zone_watermark_ok(zone, order, |
1894 | high_wmark_pages(zone), 0, 0)) { |
1895 | end_zone = i; |
1896 | break; |
1897 | } |
1898 | } |
1899 | if (i < 0) |
1900 | goto out; |
1901 | |
1902 | for (i = 0; i <= end_zone; i++) { |
1903 | struct zone *zone = pgdat->node_zones + i; |
1904 | |
1905 | lru_pages += zone_lru_pages(zone); |
1906 | } |
1907 | |
1908 | /* |
1909 | * Now scan the zone in the dma->highmem direction, stopping |
1910 | * at the last zone which needs scanning. |
1911 | * |
1912 | * We do this because the page allocator works in the opposite |
1913 | * direction. This prevents the page allocator from allocating |
1914 | * pages behind kswapd's direction of progress, which would |
1915 | * cause too much scanning of the lower zones. |
1916 | */ |
1917 | for (i = 0; i <= end_zone; i++) { |
1918 | struct zone *zone = pgdat->node_zones + i; |
1919 | int nr_slab; |
1920 | |
1921 | if (!populated_zone(zone)) |
1922 | continue; |
1923 | |
1924 | if (zone_is_all_unreclaimable(zone) && |
1925 | priority != DEF_PRIORITY) |
1926 | continue; |
1927 | |
1928 | if (!zone_watermark_ok(zone, order, |
1929 | high_wmark_pages(zone), end_zone, 0)) |
1930 | all_zones_ok = 0; |
1931 | temp_priority[i] = priority; |
1932 | sc.nr_scanned = 0; |
1933 | note_zone_scanning_priority(zone, priority); |
1934 | /* |
1935 | * We put equal pressure on every zone, unless one |
1936 | * zone has way too many pages free already. |
1937 | */ |
1938 | if (!zone_watermark_ok(zone, order, |
1939 | 8*high_wmark_pages(zone), end_zone, 0)) |
1940 | shrink_zone(priority, zone, &sc); |
1941 | reclaim_state->reclaimed_slab = 0; |
1942 | nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, |
1943 | lru_pages); |
1944 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; |
1945 | total_scanned += sc.nr_scanned; |
1946 | if (zone_is_all_unreclaimable(zone)) |
1947 | continue; |
1948 | if (nr_slab == 0 && zone->pages_scanned >= |
1949 | (zone_lru_pages(zone) * 6)) |
1950 | zone_set_flag(zone, |
1951 | ZONE_ALL_UNRECLAIMABLE); |
1952 | /* |
1953 | * If we've done a decent amount of scanning and |
1954 | * the reclaim ratio is low, start doing writepage |
1955 | * even in laptop mode |
1956 | */ |
1957 | if (total_scanned > SWAP_CLUSTER_MAX * 2 && |
1958 | total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) |
1959 | sc.may_writepage = 1; |
1960 | } |
1961 | if (all_zones_ok) |
1962 | break; /* kswapd: all done */ |
1963 | /* |
1964 | * OK, kswapd is getting into trouble. Take a nap, then take |
1965 | * another pass across the zones. |
1966 | */ |
1967 | if (total_scanned && priority < DEF_PRIORITY - 2) |
1968 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
1969 | |
1970 | /* |
1971 | * We do this so kswapd doesn't build up large priorities for |
1972 | * example when it is freeing in parallel with allocators. It |
1973 | * matches the direct reclaim path behaviour in terms of impact |
1974 | * on zone->*_priority. |
1975 | */ |
1976 | if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) |
1977 | break; |
1978 | } |
1979 | out: |
1980 | /* |
1981 | * Note within each zone the priority level at which this zone was |
1982 | * brought into a happy state. So that the next thread which scans this |
1983 | * zone will start out at that priority level. |
1984 | */ |
1985 | for (i = 0; i < pgdat->nr_zones; i++) { |
1986 | struct zone *zone = pgdat->node_zones + i; |
1987 | |
1988 | zone->prev_priority = temp_priority[i]; |
1989 | } |
1990 | if (!all_zones_ok) { |
1991 | cond_resched(); |
1992 | |
1993 | try_to_freeze(); |
1994 | |
1995 | /* |
1996 | * Fragmentation may mean that the system cannot be |
1997 | * rebalanced for high-order allocations in all zones. |
1998 | * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, |
1999 | * it means the zones have been fully scanned and are still |
2000 | * not balanced. For high-order allocations, there is |
2001 | * little point trying all over again as kswapd may |
2002 | * infinite loop. |
2003 | * |
2004 | * Instead, recheck all watermarks at order-0 as they |
2005 | * are the most important. If watermarks are ok, kswapd will go |
2006 | * back to sleep. High-order users can still perform direct |
2007 | * reclaim if they wish. |
2008 | */ |
2009 | if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) |
2010 | order = sc.order = 0; |
2011 | |
2012 | goto loop_again; |
2013 | } |
2014 | |
2015 | return sc.nr_reclaimed; |
2016 | } |
2017 | |
2018 | /* |
2019 | * The background pageout daemon, started as a kernel thread |
2020 | * from the init process. |
2021 | * |
2022 | * This basically trickles out pages so that we have _some_ |
2023 | * free memory available even if there is no other activity |
2024 | * that frees anything up. This is needed for things like routing |
2025 | * etc, where we otherwise might have all activity going on in |
2026 | * asynchronous contexts that cannot page things out. |
2027 | * |
2028 | * If there are applications that are active memory-allocators |
2029 | * (most normal use), this basically shouldn't matter. |
2030 | */ |
2031 | static int kswapd(void *p) |
2032 | { |
2033 | unsigned long order; |
2034 | pg_data_t *pgdat = (pg_data_t*)p; |
2035 | struct task_struct *tsk = current; |
2036 | DEFINE_WAIT(wait); |
2037 | struct reclaim_state reclaim_state = { |
2038 | .reclaimed_slab = 0, |
2039 | }; |
2040 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); |
2041 | |
2042 | lockdep_set_current_reclaim_state(GFP_KERNEL); |
2043 | |
2044 | if (!cpumask_empty(cpumask)) |
2045 | set_cpus_allowed_ptr(tsk, cpumask); |
2046 | current->reclaim_state = &reclaim_state; |
2047 | |
2048 | /* |
2049 | * Tell the memory management that we're a "memory allocator", |
2050 | * and that if we need more memory we should get access to it |
2051 | * regardless (see "__alloc_pages()"). "kswapd" should |
2052 | * never get caught in the normal page freeing logic. |
2053 | * |
2054 | * (Kswapd normally doesn't need memory anyway, but sometimes |
2055 | * you need a small amount of memory in order to be able to |
2056 | * page out something else, and this flag essentially protects |
2057 | * us from recursively trying to free more memory as we're |
2058 | * trying to free the first piece of memory in the first place). |
2059 | */ |
2060 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; |
2061 | set_freezable(); |
2062 | |
2063 | order = 0; |
2064 | for ( ; ; ) { |
2065 | unsigned long new_order; |
2066 | |
2067 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
2068 | new_order = pgdat->kswapd_max_order; |
2069 | pgdat->kswapd_max_order = 0; |
2070 | if (order < new_order) { |
2071 | /* |
2072 | * Don't sleep if someone wants a larger 'order' |
2073 | * allocation |
2074 | */ |
2075 | order = new_order; |
2076 | } else { |
2077 | if (!freezing(current)) |
2078 | schedule(); |
2079 | |
2080 | order = pgdat->kswapd_max_order; |
2081 | } |
2082 | finish_wait(&pgdat->kswapd_wait, &wait); |
2083 | |
2084 | if (!try_to_freeze()) { |
2085 | /* We can speed up thawing tasks if we don't call |
2086 | * balance_pgdat after returning from the refrigerator |
2087 | */ |
2088 | balance_pgdat(pgdat, order); |
2089 | } |
2090 | } |
2091 | return 0; |
2092 | } |
2093 | |
2094 | /* |
2095 | * A zone is low on free memory, so wake its kswapd task to service it. |
2096 | */ |
2097 | void wakeup_kswapd(struct zone *zone, int order) |
2098 | { |
2099 | pg_data_t *pgdat; |
2100 | |
2101 | if (!populated_zone(zone)) |
2102 | return; |
2103 | |
2104 | pgdat = zone->zone_pgdat; |
2105 | if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0)) |
2106 | return; |
2107 | if (pgdat->kswapd_max_order < order) |
2108 | pgdat->kswapd_max_order = order; |
2109 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2110 | return; |
2111 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
2112 | return; |
2113 | wake_up_interruptible(&pgdat->kswapd_wait); |
2114 | } |
2115 | |
2116 | unsigned long global_lru_pages(void) |
2117 | { |
2118 | return global_page_state(NR_ACTIVE_ANON) |
2119 | + global_page_state(NR_ACTIVE_FILE) |
2120 | + global_page_state(NR_INACTIVE_ANON) |
2121 | + global_page_state(NR_INACTIVE_FILE); |
2122 | } |
2123 | |
2124 | #ifdef CONFIG_HIBERNATION |
2125 | /* |
2126 | * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages |
2127 | * from LRU lists system-wide, for given pass and priority. |
2128 | * |
2129 | * For pass > 3 we also try to shrink the LRU lists that contain a few pages |
2130 | */ |
2131 | static void shrink_all_zones(unsigned long nr_pages, int prio, |
2132 | int pass, struct scan_control *sc) |
2133 | { |
2134 | struct zone *zone; |
2135 | unsigned long nr_reclaimed = 0; |
2136 | |
2137 | for_each_populated_zone(zone) { |
2138 | enum lru_list l; |
2139 | |
2140 | if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY) |
2141 | continue; |
2142 | |
2143 | for_each_evictable_lru(l) { |
2144 | enum zone_stat_item ls = NR_LRU_BASE + l; |
2145 | unsigned long lru_pages = zone_page_state(zone, ls); |
2146 | |
2147 | /* For pass = 0, we don't shrink the active list */ |
2148 | if (pass == 0 && (l == LRU_ACTIVE_ANON || |
2149 | l == LRU_ACTIVE_FILE)) |
2150 | continue; |
2151 | |
2152 | zone->lru[l].nr_saved_scan += (lru_pages >> prio) + 1; |
2153 | if (zone->lru[l].nr_saved_scan >= nr_pages || pass > 3) { |
2154 | unsigned long nr_to_scan; |
2155 | |
2156 | zone->lru[l].nr_saved_scan = 0; |
2157 | nr_to_scan = min(nr_pages, lru_pages); |
2158 | nr_reclaimed += shrink_list(l, nr_to_scan, zone, |
2159 | sc, prio); |
2160 | if (nr_reclaimed >= nr_pages) { |
2161 | sc->nr_reclaimed += nr_reclaimed; |
2162 | return; |
2163 | } |
2164 | } |
2165 | } |
2166 | } |
2167 | sc->nr_reclaimed += nr_reclaimed; |
2168 | } |
2169 | |
2170 | /* |
2171 | * Try to free `nr_pages' of memory, system-wide, and return the number of |
2172 | * freed pages. |
2173 | * |
2174 | * Rather than trying to age LRUs the aim is to preserve the overall |
2175 | * LRU order by reclaiming preferentially |
2176 | * inactive > active > active referenced > active mapped |
2177 | */ |
2178 | unsigned long shrink_all_memory(unsigned long nr_pages) |
2179 | { |
2180 | unsigned long lru_pages, nr_slab; |
2181 | int pass; |
2182 | struct reclaim_state reclaim_state; |
2183 | struct scan_control sc = { |
2184 | .gfp_mask = GFP_KERNEL, |
2185 | .may_unmap = 0, |
2186 | .may_writepage = 1, |
2187 | .isolate_pages = isolate_pages_global, |
2188 | .nr_reclaimed = 0, |
2189 | }; |
2190 | |
2191 | current->reclaim_state = &reclaim_state; |
2192 | |
2193 | lru_pages = global_lru_pages(); |
2194 | nr_slab = global_page_state(NR_SLAB_RECLAIMABLE); |
2195 | /* If slab caches are huge, it's better to hit them first */ |
2196 | while (nr_slab >= lru_pages) { |
2197 | reclaim_state.reclaimed_slab = 0; |
2198 | shrink_slab(nr_pages, sc.gfp_mask, lru_pages); |
2199 | if (!reclaim_state.reclaimed_slab) |
2200 | break; |
2201 | |
2202 | sc.nr_reclaimed += reclaim_state.reclaimed_slab; |
2203 | if (sc.nr_reclaimed >= nr_pages) |
2204 | goto out; |
2205 | |
2206 | nr_slab -= reclaim_state.reclaimed_slab; |
2207 | } |
2208 | |
2209 | /* |
2210 | * We try to shrink LRUs in 5 passes: |
2211 | * 0 = Reclaim from inactive_list only |
2212 | * 1 = Reclaim from active list but don't reclaim mapped |
2213 | * 2 = 2nd pass of type 1 |
2214 | * 3 = Reclaim mapped (normal reclaim) |
2215 | * 4 = 2nd pass of type 3 |
2216 | */ |
2217 | for (pass = 0; pass < 5; pass++) { |
2218 | int prio; |
2219 | |
2220 | /* Force reclaiming mapped pages in the passes #3 and #4 */ |
2221 | if (pass > 2) |
2222 | sc.may_unmap = 1; |
2223 | |
2224 | for (prio = DEF_PRIORITY; prio >= 0; prio--) { |
2225 | unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed; |
2226 | |
2227 | sc.nr_scanned = 0; |
2228 | sc.swap_cluster_max = nr_to_scan; |
2229 | shrink_all_zones(nr_to_scan, prio, pass, &sc); |
2230 | if (sc.nr_reclaimed >= nr_pages) |
2231 | goto out; |
2232 | |
2233 | reclaim_state.reclaimed_slab = 0; |
2234 | shrink_slab(sc.nr_scanned, sc.gfp_mask, |
2235 | global_lru_pages()); |
2236 | sc.nr_reclaimed += reclaim_state.reclaimed_slab; |
2237 | if (sc.nr_reclaimed >= nr_pages) |
2238 | goto out; |
2239 | |
2240 | if (sc.nr_scanned && prio < DEF_PRIORITY - 2) |
2241 | congestion_wait(BLK_RW_ASYNC, HZ / 10); |
2242 | } |
2243 | } |
2244 | |
2245 | /* |
2246 | * If sc.nr_reclaimed = 0, we could not shrink LRUs, but there may be |
2247 | * something in slab caches |
2248 | */ |
2249 | if (!sc.nr_reclaimed) { |
2250 | do { |
2251 | reclaim_state.reclaimed_slab = 0; |
2252 | shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages()); |
2253 | sc.nr_reclaimed += reclaim_state.reclaimed_slab; |
2254 | } while (sc.nr_reclaimed < nr_pages && |
2255 | reclaim_state.reclaimed_slab > 0); |
2256 | } |
2257 | |
2258 | |
2259 | out: |
2260 | current->reclaim_state = NULL; |
2261 | |
2262 | return sc.nr_reclaimed; |
2263 | } |
2264 | #endif /* CONFIG_HIBERNATION */ |
2265 | |
2266 | /* It's optimal to keep kswapds on the same CPUs as their memory, but |
2267 | not required for correctness. So if the last cpu in a node goes |
2268 | away, we get changed to run anywhere: as the first one comes back, |
2269 | restore their cpu bindings. */ |
2270 | static int __devinit cpu_callback(struct notifier_block *nfb, |
2271 | unsigned long action, void *hcpu) |
2272 | { |
2273 | int nid; |
2274 | |
2275 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { |
2276 | for_each_node_state(nid, N_HIGH_MEMORY) { |
2277 | pg_data_t *pgdat = NODE_DATA(nid); |
2278 | const struct cpumask *mask; |
2279 | |
2280 | mask = cpumask_of_node(pgdat->node_id); |
2281 | |
2282 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
2283 | /* One of our CPUs online: restore mask */ |
2284 | set_cpus_allowed_ptr(pgdat->kswapd, mask); |
2285 | } |
2286 | } |
2287 | return NOTIFY_OK; |
2288 | } |
2289 | |
2290 | /* |
2291 | * This kswapd start function will be called by init and node-hot-add. |
2292 | * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. |
2293 | */ |
2294 | int kswapd_run(int nid) |
2295 | { |
2296 | pg_data_t *pgdat = NODE_DATA(nid); |
2297 | int ret = 0; |
2298 | |
2299 | if (pgdat->kswapd) |
2300 | return 0; |
2301 | |
2302 | pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); |
2303 | if (IS_ERR(pgdat->kswapd)) { |
2304 | /* failure at boot is fatal */ |
2305 | BUG_ON(system_state == SYSTEM_BOOTING); |
2306 | printk("Failed to start kswapd on node %d\n",nid); |
2307 | ret = -1; |
2308 | } |
2309 | return ret; |
2310 | } |
2311 | |
2312 | static int __init kswapd_init(void) |
2313 | { |
2314 | int nid; |
2315 | |
2316 | swap_setup(); |
2317 | for_each_node_state(nid, N_HIGH_MEMORY) |
2318 | kswapd_run(nid); |
2319 | hotcpu_notifier(cpu_callback, 0); |
2320 | return 0; |
2321 | } |
2322 | |
2323 | module_init(kswapd_init) |
2324 | |
2325 | #ifdef CONFIG_NUMA |
2326 | /* |
2327 | * Zone reclaim mode |
2328 | * |
2329 | * If non-zero call zone_reclaim when the number of free pages falls below |
2330 | * the watermarks. |
2331 | */ |
2332 | int zone_reclaim_mode __read_mostly; |
2333 | |
2334 | #define RECLAIM_OFF 0 |
2335 | #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ |
2336 | #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ |
2337 | #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ |
2338 | |
2339 | /* |
2340 | * Priority for ZONE_RECLAIM. This determines the fraction of pages |
2341 | * of a node considered for each zone_reclaim. 4 scans 1/16th of |
2342 | * a zone. |
2343 | */ |
2344 | #define ZONE_RECLAIM_PRIORITY 4 |
2345 | |
2346 | /* |
2347 | * Percentage of pages in a zone that must be unmapped for zone_reclaim to |
2348 | * occur. |
2349 | */ |
2350 | int sysctl_min_unmapped_ratio = 1; |
2351 | |
2352 | /* |
2353 | * If the number of slab pages in a zone grows beyond this percentage then |
2354 | * slab reclaim needs to occur. |
2355 | */ |
2356 | int sysctl_min_slab_ratio = 5; |
2357 | |
2358 | static inline unsigned long zone_unmapped_file_pages(struct zone *zone) |
2359 | { |
2360 | unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); |
2361 | unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + |
2362 | zone_page_state(zone, NR_ACTIVE_FILE); |
2363 | |
2364 | /* |
2365 | * It's possible for there to be more file mapped pages than |
2366 | * accounted for by the pages on the file LRU lists because |
2367 | * tmpfs pages accounted for as ANON can also be FILE_MAPPED |
2368 | */ |
2369 | return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; |
2370 | } |
2371 | |
2372 | /* Work out how many page cache pages we can reclaim in this reclaim_mode */ |
2373 | static long zone_pagecache_reclaimable(struct zone *zone) |
2374 | { |
2375 | long nr_pagecache_reclaimable; |
2376 | long delta = 0; |
2377 | |
2378 | /* |
2379 | * If RECLAIM_SWAP is set, then all file pages are considered |
2380 | * potentially reclaimable. Otherwise, we have to worry about |
2381 | * pages like swapcache and zone_unmapped_file_pages() provides |
2382 | * a better estimate |
2383 | */ |
2384 | if (zone_reclaim_mode & RECLAIM_SWAP) |
2385 | nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); |
2386 | else |
2387 | nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); |
2388 | |
2389 | /* If we can't clean pages, remove dirty pages from consideration */ |
2390 | if (!(zone_reclaim_mode & RECLAIM_WRITE)) |
2391 | delta += zone_page_state(zone, NR_FILE_DIRTY); |
2392 | |
2393 | /* Watch for any possible underflows due to delta */ |
2394 | if (unlikely(delta > nr_pagecache_reclaimable)) |
2395 | delta = nr_pagecache_reclaimable; |
2396 | |
2397 | return nr_pagecache_reclaimable - delta; |
2398 | } |
2399 | |
2400 | /* |
2401 | * Try to free up some pages from this zone through reclaim. |
2402 | */ |
2403 | static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
2404 | { |
2405 | /* Minimum pages needed in order to stay on node */ |
2406 | const unsigned long nr_pages = 1 << order; |
2407 | struct task_struct *p = current; |
2408 | struct reclaim_state reclaim_state; |
2409 | int priority; |
2410 | struct scan_control sc = { |
2411 | .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), |
2412 | .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), |
2413 | .may_swap = 1, |
2414 | .swap_cluster_max = max_t(unsigned long, nr_pages, |
2415 | SWAP_CLUSTER_MAX), |
2416 | .gfp_mask = gfp_mask, |
2417 | .swappiness = vm_swappiness, |
2418 | .order = order, |
2419 | .isolate_pages = isolate_pages_global, |
2420 | }; |
2421 | unsigned long slab_reclaimable; |
2422 | |
2423 | disable_swap_token(); |
2424 | cond_resched(); |
2425 | /* |
2426 | * We need to be able to allocate from the reserves for RECLAIM_SWAP |
2427 | * and we also need to be able to write out pages for RECLAIM_WRITE |
2428 | * and RECLAIM_SWAP. |
2429 | */ |
2430 | p->flags |= PF_MEMALLOC | PF_SWAPWRITE; |
2431 | reclaim_state.reclaimed_slab = 0; |
2432 | p->reclaim_state = &reclaim_state; |
2433 | |
2434 | if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { |
2435 | /* |
2436 | * Free memory by calling shrink zone with increasing |
2437 | * priorities until we have enough memory freed. |
2438 | */ |
2439 | priority = ZONE_RECLAIM_PRIORITY; |
2440 | do { |
2441 | note_zone_scanning_priority(zone, priority); |
2442 | shrink_zone(priority, zone, &sc); |
2443 | priority--; |
2444 | } while (priority >= 0 && sc.nr_reclaimed < nr_pages); |
2445 | } |
2446 | |
2447 | slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
2448 | if (slab_reclaimable > zone->min_slab_pages) { |
2449 | /* |
2450 | * shrink_slab() does not currently allow us to determine how |
2451 | * many pages were freed in this zone. So we take the current |
2452 | * number of slab pages and shake the slab until it is reduced |
2453 | * by the same nr_pages that we used for reclaiming unmapped |
2454 | * pages. |
2455 | * |
2456 | * Note that shrink_slab will free memory on all zones and may |
2457 | * take a long time. |
2458 | */ |
2459 | while (shrink_slab(sc.nr_scanned, gfp_mask, order) && |
2460 | zone_page_state(zone, NR_SLAB_RECLAIMABLE) > |
2461 | slab_reclaimable - nr_pages) |
2462 | ; |
2463 | |
2464 | /* |
2465 | * Update nr_reclaimed by the number of slab pages we |
2466 | * reclaimed from this zone. |
2467 | */ |
2468 | sc.nr_reclaimed += slab_reclaimable - |
2469 | zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
2470 | } |
2471 | |
2472 | p->reclaim_state = NULL; |
2473 | current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); |
2474 | return sc.nr_reclaimed >= nr_pages; |
2475 | } |
2476 | |
2477 | int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
2478 | { |
2479 | int node_id; |
2480 | int ret; |
2481 | |
2482 | /* |
2483 | * Zone reclaim reclaims unmapped file backed pages and |
2484 | * slab pages if we are over the defined limits. |
2485 | * |
2486 | * A small portion of unmapped file backed pages is needed for |
2487 | * file I/O otherwise pages read by file I/O will be immediately |
2488 | * thrown out if the zone is overallocated. So we do not reclaim |
2489 | * if less than a specified percentage of the zone is used by |
2490 | * unmapped file backed pages. |
2491 | */ |
2492 | if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && |
2493 | zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) |
2494 | return ZONE_RECLAIM_FULL; |
2495 | |
2496 | if (zone_is_all_unreclaimable(zone)) |
2497 | return ZONE_RECLAIM_FULL; |
2498 | |
2499 | /* |
2500 | * Do not scan if the allocation should not be delayed. |
2501 | */ |
2502 | if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) |
2503 | return ZONE_RECLAIM_NOSCAN; |
2504 | |
2505 | /* |
2506 | * Only run zone reclaim on the local zone or on zones that do not |
2507 | * have associated processors. This will favor the local processor |
2508 | * over remote processors and spread off node memory allocations |
2509 | * as wide as possible. |
2510 | */ |
2511 | node_id = zone_to_nid(zone); |
2512 | if (node_state(node_id, N_CPU) && node_id != numa_node_id()) |
2513 | return ZONE_RECLAIM_NOSCAN; |
2514 | |
2515 | if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) |
2516 | return ZONE_RECLAIM_NOSCAN; |
2517 | |
2518 | ret = __zone_reclaim(zone, gfp_mask, order); |
2519 | zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); |
2520 | |
2521 | if (!ret) |
2522 | count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); |
2523 | |
2524 | return ret; |
2525 | } |
2526 | #endif |
2527 | |
2528 | /* |
2529 | * page_evictable - test whether a page is evictable |
2530 | * @page: the page to test |
2531 | * @vma: the VMA in which the page is or will be mapped, may be NULL |
2532 | * |
2533 | * Test whether page is evictable--i.e., should be placed on active/inactive |
2534 | * lists vs unevictable list. The vma argument is !NULL when called from the |
2535 | * fault path to determine how to instantate a new page. |
2536 | * |
2537 | * Reasons page might not be evictable: |
2538 | * (1) page's mapping marked unevictable |
2539 | * (2) page is part of an mlocked VMA |
2540 | * |
2541 | */ |
2542 | int page_evictable(struct page *page, struct vm_area_struct *vma) |
2543 | { |
2544 | |
2545 | if (mapping_unevictable(page_mapping(page))) |
2546 | return 0; |
2547 | |
2548 | if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) |
2549 | return 0; |
2550 | |
2551 | return 1; |
2552 | } |
2553 | |
2554 | /** |
2555 | * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list |
2556 | * @page: page to check evictability and move to appropriate lru list |
2557 | * @zone: zone page is in |
2558 | * |
2559 | * Checks a page for evictability and moves the page to the appropriate |
2560 | * zone lru list. |
2561 | * |
2562 | * Restrictions: zone->lru_lock must be held, page must be on LRU and must |
2563 | * have PageUnevictable set. |
2564 | */ |
2565 | static void check_move_unevictable_page(struct page *page, struct zone *zone) |
2566 | { |
2567 | VM_BUG_ON(PageActive(page)); |
2568 | |
2569 | retry: |
2570 | ClearPageUnevictable(page); |
2571 | if (page_evictable(page, NULL)) { |
2572 | enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page); |
2573 | |
2574 | __dec_zone_state(zone, NR_UNEVICTABLE); |
2575 | list_move(&page->lru, &zone->lru[l].list); |
2576 | mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); |
2577 | __inc_zone_state(zone, NR_INACTIVE_ANON + l); |
2578 | __count_vm_event(UNEVICTABLE_PGRESCUED); |
2579 | } else { |
2580 | /* |
2581 | * rotate unevictable list |
2582 | */ |
2583 | SetPageUnevictable(page); |
2584 | list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); |
2585 | mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); |
2586 | if (page_evictable(page, NULL)) |
2587 | goto retry; |
2588 | } |
2589 | } |
2590 | |
2591 | /** |
2592 | * scan_mapping_unevictable_pages - scan an address space for evictable pages |
2593 | * @mapping: struct address_space to scan for evictable pages |
2594 | * |
2595 | * Scan all pages in mapping. Check unevictable pages for |
2596 | * evictability and move them to the appropriate zone lru list. |
2597 | */ |
2598 | void scan_mapping_unevictable_pages(struct address_space *mapping) |
2599 | { |
2600 | pgoff_t next = 0; |
2601 | pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> |
2602 | PAGE_CACHE_SHIFT; |
2603 | struct zone *zone; |
2604 | struct pagevec pvec; |
2605 | |
2606 | if (mapping->nrpages == 0) |
2607 | return; |
2608 | |
2609 | pagevec_init(&pvec, 0); |
2610 | while (next < end && |
2611 | pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { |
2612 | int i; |
2613 | int pg_scanned = 0; |
2614 | |
2615 | zone = NULL; |
2616 | |
2617 | for (i = 0; i < pagevec_count(&pvec); i++) { |
2618 | struct page *page = pvec.pages[i]; |
2619 | pgoff_t page_index = page->index; |
2620 | struct zone *pagezone = page_zone(page); |
2621 | |
2622 | pg_scanned++; |
2623 | if (page_index > next) |
2624 | next = page_index; |
2625 | next++; |
2626 | |
2627 | if (pagezone != zone) { |
2628 | if (zone) |
2629 | spin_unlock_irq(&zone->lru_lock); |
2630 | zone = pagezone; |
2631 | spin_lock_irq(&zone->lru_lock); |
2632 | } |
2633 | |
2634 | if (PageLRU(page) && PageUnevictable(page)) |
2635 | check_move_unevictable_page(page, zone); |
2636 | } |
2637 | if (zone) |
2638 | spin_unlock_irq(&zone->lru_lock); |
2639 | pagevec_release(&pvec); |
2640 | |
2641 | count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); |
2642 | } |
2643 | |
2644 | } |
2645 | |
2646 | /** |
2647 | * scan_zone_unevictable_pages - check unevictable list for evictable pages |
2648 | * @zone - zone of which to scan the unevictable list |
2649 | * |
2650 | * Scan @zone's unevictable LRU lists to check for pages that have become |
2651 | * evictable. Move those that have to @zone's inactive list where they |
2652 | * become candidates for reclaim, unless shrink_inactive_zone() decides |
2653 | * to reactivate them. Pages that are still unevictable are rotated |
2654 | * back onto @zone's unevictable list. |
2655 | */ |
2656 | #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ |
2657 | static void scan_zone_unevictable_pages(struct zone *zone) |
2658 | { |
2659 | struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; |
2660 | unsigned long scan; |
2661 | unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); |
2662 | |
2663 | while (nr_to_scan > 0) { |
2664 | unsigned long batch_size = min(nr_to_scan, |
2665 | SCAN_UNEVICTABLE_BATCH_SIZE); |
2666 | |
2667 | spin_lock_irq(&zone->lru_lock); |
2668 | for (scan = 0; scan < batch_size; scan++) { |
2669 | struct page *page = lru_to_page(l_unevictable); |
2670 | |
2671 | if (!trylock_page(page)) |
2672 | continue; |
2673 | |
2674 | prefetchw_prev_lru_page(page, l_unevictable, flags); |
2675 | |
2676 | if (likely(PageLRU(page) && PageUnevictable(page))) |
2677 | check_move_unevictable_page(page, zone); |
2678 | |
2679 | unlock_page(page); |
2680 | } |
2681 | spin_unlock_irq(&zone->lru_lock); |
2682 | |
2683 | nr_to_scan -= batch_size; |
2684 | } |
2685 | } |
2686 | |
2687 | |
2688 | /** |
2689 | * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages |
2690 | * |
2691 | * A really big hammer: scan all zones' unevictable LRU lists to check for |
2692 | * pages that have become evictable. Move those back to the zones' |
2693 | * inactive list where they become candidates for reclaim. |
2694 | * This occurs when, e.g., we have unswappable pages on the unevictable lists, |
2695 | * and we add swap to the system. As such, it runs in the context of a task |
2696 | * that has possibly/probably made some previously unevictable pages |
2697 | * evictable. |
2698 | */ |
2699 | static void scan_all_zones_unevictable_pages(void) |
2700 | { |
2701 | struct zone *zone; |
2702 | |
2703 | for_each_zone(zone) { |
2704 | scan_zone_unevictable_pages(zone); |
2705 | } |
2706 | } |
2707 | |
2708 | /* |
2709 | * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of |
2710 | * all nodes' unevictable lists for evictable pages |
2711 | */ |
2712 | unsigned long scan_unevictable_pages; |
2713 | |
2714 | int scan_unevictable_handler(struct ctl_table *table, int write, |
2715 | struct file *file, void __user *buffer, |
2716 | size_t *length, loff_t *ppos) |
2717 | { |
2718 | proc_doulongvec_minmax(table, write, file, buffer, length, ppos); |
2719 | |
2720 | if (write && *(unsigned long *)table->data) |
2721 | scan_all_zones_unevictable_pages(); |
2722 | |
2723 | scan_unevictable_pages = 0; |
2724 | return 0; |
2725 | } |
2726 | |
2727 | /* |
2728 | * per node 'scan_unevictable_pages' attribute. On demand re-scan of |
2729 | * a specified node's per zone unevictable lists for evictable pages. |
2730 | */ |
2731 | |
2732 | static ssize_t read_scan_unevictable_node(struct sys_device *dev, |
2733 | struct sysdev_attribute *attr, |
2734 | char *buf) |
2735 | { |
2736 | return sprintf(buf, "0\n"); /* always zero; should fit... */ |
2737 | } |
2738 | |
2739 | static ssize_t write_scan_unevictable_node(struct sys_device *dev, |
2740 | struct sysdev_attribute *attr, |
2741 | const char *buf, size_t count) |
2742 | { |
2743 | struct zone *node_zones = NODE_DATA(dev->id)->node_zones; |
2744 | struct zone *zone; |
2745 | unsigned long res; |
2746 | unsigned long req = strict_strtoul(buf, 10, &res); |
2747 | |
2748 | if (!req) |
2749 | return 1; /* zero is no-op */ |
2750 | |
2751 | for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { |
2752 | if (!populated_zone(zone)) |
2753 | continue; |
2754 | scan_zone_unevictable_pages(zone); |
2755 | } |
2756 | return 1; |
2757 | } |
2758 | |
2759 | |
2760 | static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, |
2761 | read_scan_unevictable_node, |
2762 | write_scan_unevictable_node); |
2763 | |
2764 | int scan_unevictable_register_node(struct node *node) |
2765 | { |
2766 | return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); |
2767 | } |
2768 | |
2769 | void scan_unevictable_unregister_node(struct node *node) |
2770 | { |
2771 | sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); |
2772 | } |
2773 | |
2774 |
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