Root/
1 | /* |
2 | * linux/mm/vmscan.c |
3 | * |
4 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
5 | * |
6 | * Swap reorganised 29.12.95, Stephen Tweedie. |
7 | * kswapd added: 7.1.96 sct |
8 | * Removed kswapd_ctl limits, and swap out as many pages as needed |
9 | * to bring the system back to freepages.high: 2.4.97, Rik van Riel. |
10 | * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). |
11 | * Multiqueue VM started 5.8.00, Rik van Riel. |
12 | */ |
13 | |
14 | #include <linux/mm.h> |
15 | #include <linux/module.h> |
16 | #include <linux/gfp.h> |
17 | #include <linux/kernel_stat.h> |
18 | #include <linux/swap.h> |
19 | #include <linux/pagemap.h> |
20 | #include <linux/init.h> |
21 | #include <linux/highmem.h> |
22 | #include <linux/vmstat.h> |
23 | #include <linux/file.h> |
24 | #include <linux/writeback.h> |
25 | #include <linux/blkdev.h> |
26 | #include <linux/buffer_head.h> /* for try_to_release_page(), |
27 | buffer_heads_over_limit */ |
28 | #include <linux/mm_inline.h> |
29 | #include <linux/pagevec.h> |
30 | #include <linux/backing-dev.h> |
31 | #include <linux/rmap.h> |
32 | #include <linux/topology.h> |
33 | #include <linux/cpu.h> |
34 | #include <linux/cpuset.h> |
35 | #include <linux/compaction.h> |
36 | #include <linux/notifier.h> |
37 | #include <linux/rwsem.h> |
38 | #include <linux/delay.h> |
39 | #include <linux/kthread.h> |
40 | #include <linux/freezer.h> |
41 | #include <linux/memcontrol.h> |
42 | #include <linux/delayacct.h> |
43 | #include <linux/sysctl.h> |
44 | |
45 | #include <asm/tlbflush.h> |
46 | #include <asm/div64.h> |
47 | |
48 | #include <linux/swapops.h> |
49 | |
50 | #include "internal.h" |
51 | |
52 | #define CREATE_TRACE_POINTS |
53 | #include <trace/events/vmscan.h> |
54 | |
55 | /* |
56 | * reclaim_mode determines how the inactive list is shrunk |
57 | * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages |
58 | * RECLAIM_MODE_ASYNC: Do not block |
59 | * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback |
60 | * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference |
61 | * page from the LRU and reclaim all pages within a |
62 | * naturally aligned range |
63 | * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of |
64 | * order-0 pages and then compact the zone |
65 | */ |
66 | typedef unsigned __bitwise__ reclaim_mode_t; |
67 | #define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u) |
68 | #define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u) |
69 | #define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u) |
70 | #define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u) |
71 | #define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u) |
72 | |
73 | struct scan_control { |
74 | /* Incremented by the number of inactive pages that were scanned */ |
75 | unsigned long nr_scanned; |
76 | |
77 | /* Number of pages freed so far during a call to shrink_zones() */ |
78 | unsigned long nr_reclaimed; |
79 | |
80 | /* How many pages shrink_list() should reclaim */ |
81 | unsigned long nr_to_reclaim; |
82 | |
83 | unsigned long hibernation_mode; |
84 | |
85 | /* This context's GFP mask */ |
86 | gfp_t gfp_mask; |
87 | |
88 | int may_writepage; |
89 | |
90 | /* Can mapped pages be reclaimed? */ |
91 | int may_unmap; |
92 | |
93 | /* Can pages be swapped as part of reclaim? */ |
94 | int may_swap; |
95 | |
96 | int swappiness; |
97 | |
98 | int order; |
99 | |
100 | /* |
101 | * Intend to reclaim enough continuous memory rather than reclaim |
102 | * enough amount of memory. i.e, mode for high order allocation. |
103 | */ |
104 | reclaim_mode_t reclaim_mode; |
105 | |
106 | /* Which cgroup do we reclaim from */ |
107 | struct mem_cgroup *mem_cgroup; |
108 | |
109 | /* |
110 | * Nodemask of nodes allowed by the caller. If NULL, all nodes |
111 | * are scanned. |
112 | */ |
113 | nodemask_t *nodemask; |
114 | }; |
115 | |
116 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) |
117 | |
118 | #ifdef ARCH_HAS_PREFETCH |
119 | #define prefetch_prev_lru_page(_page, _base, _field) \ |
120 | do { \ |
121 | if ((_page)->lru.prev != _base) { \ |
122 | struct page *prev; \ |
123 | \ |
124 | prev = lru_to_page(&(_page->lru)); \ |
125 | prefetch(&prev->_field); \ |
126 | } \ |
127 | } while (0) |
128 | #else |
129 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) |
130 | #endif |
131 | |
132 | #ifdef ARCH_HAS_PREFETCHW |
133 | #define prefetchw_prev_lru_page(_page, _base, _field) \ |
134 | do { \ |
135 | if ((_page)->lru.prev != _base) { \ |
136 | struct page *prev; \ |
137 | \ |
138 | prev = lru_to_page(&(_page->lru)); \ |
139 | prefetchw(&prev->_field); \ |
140 | } \ |
141 | } while (0) |
142 | #else |
143 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) |
144 | #endif |
145 | |
146 | /* |
147 | * From 0 .. 100. Higher means more swappy. |
148 | */ |
149 | int vm_swappiness = 60; |
150 | long vm_total_pages; /* The total number of pages which the VM controls */ |
151 | |
152 | static LIST_HEAD(shrinker_list); |
153 | static DECLARE_RWSEM(shrinker_rwsem); |
154 | |
155 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
156 | #define scanning_global_lru(sc) (!(sc)->mem_cgroup) |
157 | #else |
158 | #define scanning_global_lru(sc) (1) |
159 | #endif |
160 | |
161 | static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, |
162 | struct scan_control *sc) |
163 | { |
164 | if (!scanning_global_lru(sc)) |
165 | return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); |
166 | |
167 | return &zone->reclaim_stat; |
168 | } |
169 | |
170 | static unsigned long zone_nr_lru_pages(struct zone *zone, |
171 | struct scan_control *sc, enum lru_list lru) |
172 | { |
173 | if (!scanning_global_lru(sc)) |
174 | return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru); |
175 | |
176 | return zone_page_state(zone, NR_LRU_BASE + lru); |
177 | } |
178 | |
179 | |
180 | /* |
181 | * Add a shrinker callback to be called from the vm |
182 | */ |
183 | void register_shrinker(struct shrinker *shrinker) |
184 | { |
185 | shrinker->nr = 0; |
186 | down_write(&shrinker_rwsem); |
187 | list_add_tail(&shrinker->list, &shrinker_list); |
188 | up_write(&shrinker_rwsem); |
189 | } |
190 | EXPORT_SYMBOL(register_shrinker); |
191 | |
192 | /* |
193 | * Remove one |
194 | */ |
195 | void unregister_shrinker(struct shrinker *shrinker) |
196 | { |
197 | down_write(&shrinker_rwsem); |
198 | list_del(&shrinker->list); |
199 | up_write(&shrinker_rwsem); |
200 | } |
201 | EXPORT_SYMBOL(unregister_shrinker); |
202 | |
203 | #define SHRINK_BATCH 128 |
204 | /* |
205 | * Call the shrink functions to age shrinkable caches |
206 | * |
207 | * Here we assume it costs one seek to replace a lru page and that it also |
208 | * takes a seek to recreate a cache object. With this in mind we age equal |
209 | * percentages of the lru and ageable caches. This should balance the seeks |
210 | * generated by these structures. |
211 | * |
212 | * If the vm encountered mapped pages on the LRU it increase the pressure on |
213 | * slab to avoid swapping. |
214 | * |
215 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. |
216 | * |
217 | * `lru_pages' represents the number of on-LRU pages in all the zones which |
218 | * are eligible for the caller's allocation attempt. It is used for balancing |
219 | * slab reclaim versus page reclaim. |
220 | * |
221 | * Returns the number of slab objects which we shrunk. |
222 | */ |
223 | unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, |
224 | unsigned long lru_pages) |
225 | { |
226 | struct shrinker *shrinker; |
227 | unsigned long ret = 0; |
228 | |
229 | if (scanned == 0) |
230 | scanned = SWAP_CLUSTER_MAX; |
231 | |
232 | if (!down_read_trylock(&shrinker_rwsem)) |
233 | return 1; /* Assume we'll be able to shrink next time */ |
234 | |
235 | list_for_each_entry(shrinker, &shrinker_list, list) { |
236 | unsigned long long delta; |
237 | unsigned long total_scan; |
238 | unsigned long max_pass; |
239 | |
240 | max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask); |
241 | delta = (4 * scanned) / shrinker->seeks; |
242 | delta *= max_pass; |
243 | do_div(delta, lru_pages + 1); |
244 | shrinker->nr += delta; |
245 | if (shrinker->nr < 0) { |
246 | printk(KERN_ERR "shrink_slab: %pF negative objects to " |
247 | "delete nr=%ld\n", |
248 | shrinker->shrink, shrinker->nr); |
249 | shrinker->nr = max_pass; |
250 | } |
251 | |
252 | /* |
253 | * Avoid risking looping forever due to too large nr value: |
254 | * never try to free more than twice the estimate number of |
255 | * freeable entries. |
256 | */ |
257 | if (shrinker->nr > max_pass * 2) |
258 | shrinker->nr = max_pass * 2; |
259 | |
260 | total_scan = shrinker->nr; |
261 | shrinker->nr = 0; |
262 | |
263 | while (total_scan >= SHRINK_BATCH) { |
264 | long this_scan = SHRINK_BATCH; |
265 | int shrink_ret; |
266 | int nr_before; |
267 | |
268 | nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask); |
269 | shrink_ret = (*shrinker->shrink)(shrinker, this_scan, |
270 | gfp_mask); |
271 | if (shrink_ret == -1) |
272 | break; |
273 | if (shrink_ret < nr_before) |
274 | ret += nr_before - shrink_ret; |
275 | count_vm_events(SLABS_SCANNED, this_scan); |
276 | total_scan -= this_scan; |
277 | |
278 | cond_resched(); |
279 | } |
280 | |
281 | shrinker->nr += total_scan; |
282 | } |
283 | up_read(&shrinker_rwsem); |
284 | return ret; |
285 | } |
286 | |
287 | static void set_reclaim_mode(int priority, struct scan_control *sc, |
288 | bool sync) |
289 | { |
290 | reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; |
291 | |
292 | /* |
293 | * Initially assume we are entering either lumpy reclaim or |
294 | * reclaim/compaction.Depending on the order, we will either set the |
295 | * sync mode or just reclaim order-0 pages later. |
296 | */ |
297 | if (COMPACTION_BUILD) |
298 | sc->reclaim_mode = RECLAIM_MODE_COMPACTION; |
299 | else |
300 | sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; |
301 | |
302 | /* |
303 | * Avoid using lumpy reclaim or reclaim/compaction if possible by |
304 | * restricting when its set to either costly allocations or when |
305 | * under memory pressure |
306 | */ |
307 | if (sc->order > PAGE_ALLOC_COSTLY_ORDER) |
308 | sc->reclaim_mode |= syncmode; |
309 | else if (sc->order && priority < DEF_PRIORITY - 2) |
310 | sc->reclaim_mode |= syncmode; |
311 | else |
312 | sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; |
313 | } |
314 | |
315 | static void reset_reclaim_mode(struct scan_control *sc) |
316 | { |
317 | sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; |
318 | } |
319 | |
320 | static inline int is_page_cache_freeable(struct page *page) |
321 | { |
322 | /* |
323 | * A freeable page cache page is referenced only by the caller |
324 | * that isolated the page, the page cache radix tree and |
325 | * optional buffer heads at page->private. |
326 | */ |
327 | return page_count(page) - page_has_private(page) == 2; |
328 | } |
329 | |
330 | static int may_write_to_queue(struct backing_dev_info *bdi, |
331 | struct scan_control *sc) |
332 | { |
333 | if (current->flags & PF_SWAPWRITE) |
334 | return 1; |
335 | if (!bdi_write_congested(bdi)) |
336 | return 1; |
337 | if (bdi == current->backing_dev_info) |
338 | return 1; |
339 | |
340 | /* lumpy reclaim for hugepage often need a lot of write */ |
341 | if (sc->order > PAGE_ALLOC_COSTLY_ORDER) |
342 | return 1; |
343 | return 0; |
344 | } |
345 | |
346 | /* |
347 | * We detected a synchronous write error writing a page out. Probably |
348 | * -ENOSPC. We need to propagate that into the address_space for a subsequent |
349 | * fsync(), msync() or close(). |
350 | * |
351 | * The tricky part is that after writepage we cannot touch the mapping: nothing |
352 | * prevents it from being freed up. But we have a ref on the page and once |
353 | * that page is locked, the mapping is pinned. |
354 | * |
355 | * We're allowed to run sleeping lock_page() here because we know the caller has |
356 | * __GFP_FS. |
357 | */ |
358 | static void handle_write_error(struct address_space *mapping, |
359 | struct page *page, int error) |
360 | { |
361 | lock_page_nosync(page); |
362 | if (page_mapping(page) == mapping) |
363 | mapping_set_error(mapping, error); |
364 | unlock_page(page); |
365 | } |
366 | |
367 | /* possible outcome of pageout() */ |
368 | typedef enum { |
369 | /* failed to write page out, page is locked */ |
370 | PAGE_KEEP, |
371 | /* move page to the active list, page is locked */ |
372 | PAGE_ACTIVATE, |
373 | /* page has been sent to the disk successfully, page is unlocked */ |
374 | PAGE_SUCCESS, |
375 | /* page is clean and locked */ |
376 | PAGE_CLEAN, |
377 | } pageout_t; |
378 | |
379 | /* |
380 | * pageout is called by shrink_page_list() for each dirty page. |
381 | * Calls ->writepage(). |
382 | */ |
383 | static pageout_t pageout(struct page *page, struct address_space *mapping, |
384 | struct scan_control *sc) |
385 | { |
386 | /* |
387 | * If the page is dirty, only perform writeback if that write |
388 | * will be non-blocking. To prevent this allocation from being |
389 | * stalled by pagecache activity. But note that there may be |
390 | * stalls if we need to run get_block(). We could test |
391 | * PagePrivate for that. |
392 | * |
393 | * If this process is currently in __generic_file_aio_write() against |
394 | * this page's queue, we can perform writeback even if that |
395 | * will block. |
396 | * |
397 | * If the page is swapcache, write it back even if that would |
398 | * block, for some throttling. This happens by accident, because |
399 | * swap_backing_dev_info is bust: it doesn't reflect the |
400 | * congestion state of the swapdevs. Easy to fix, if needed. |
401 | */ |
402 | if (!is_page_cache_freeable(page)) |
403 | return PAGE_KEEP; |
404 | if (!mapping) { |
405 | /* |
406 | * Some data journaling orphaned pages can have |
407 | * page->mapping == NULL while being dirty with clean buffers. |
408 | */ |
409 | if (page_has_private(page)) { |
410 | if (try_to_free_buffers(page)) { |
411 | ClearPageDirty(page); |
412 | printk("%s: orphaned page\n", __func__); |
413 | return PAGE_CLEAN; |
414 | } |
415 | } |
416 | return PAGE_KEEP; |
417 | } |
418 | if (mapping->a_ops->writepage == NULL) |
419 | return PAGE_ACTIVATE; |
420 | if (!may_write_to_queue(mapping->backing_dev_info, sc)) |
421 | return PAGE_KEEP; |
422 | |
423 | if (clear_page_dirty_for_io(page)) { |
424 | int res; |
425 | struct writeback_control wbc = { |
426 | .sync_mode = WB_SYNC_NONE, |
427 | .nr_to_write = SWAP_CLUSTER_MAX, |
428 | .range_start = 0, |
429 | .range_end = LLONG_MAX, |
430 | .for_reclaim = 1, |
431 | }; |
432 | |
433 | SetPageReclaim(page); |
434 | res = mapping->a_ops->writepage(page, &wbc); |
435 | if (res < 0) |
436 | handle_write_error(mapping, page, res); |
437 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
438 | ClearPageReclaim(page); |
439 | return PAGE_ACTIVATE; |
440 | } |
441 | |
442 | /* |
443 | * Wait on writeback if requested to. This happens when |
444 | * direct reclaiming a large contiguous area and the |
445 | * first attempt to free a range of pages fails. |
446 | */ |
447 | if (PageWriteback(page) && |
448 | (sc->reclaim_mode & RECLAIM_MODE_SYNC)) |
449 | wait_on_page_writeback(page); |
450 | |
451 | if (!PageWriteback(page)) { |
452 | /* synchronous write or broken a_ops? */ |
453 | ClearPageReclaim(page); |
454 | } |
455 | trace_mm_vmscan_writepage(page, |
456 | trace_reclaim_flags(page, sc->reclaim_mode)); |
457 | inc_zone_page_state(page, NR_VMSCAN_WRITE); |
458 | return PAGE_SUCCESS; |
459 | } |
460 | |
461 | return PAGE_CLEAN; |
462 | } |
463 | |
464 | /* |
465 | * Same as remove_mapping, but if the page is removed from the mapping, it |
466 | * gets returned with a refcount of 0. |
467 | */ |
468 | static int __remove_mapping(struct address_space *mapping, struct page *page) |
469 | { |
470 | BUG_ON(!PageLocked(page)); |
471 | BUG_ON(mapping != page_mapping(page)); |
472 | |
473 | spin_lock_irq(&mapping->tree_lock); |
474 | /* |
475 | * The non racy check for a busy page. |
476 | * |
477 | * Must be careful with the order of the tests. When someone has |
478 | * a ref to the page, it may be possible that they dirty it then |
479 | * drop the reference. So if PageDirty is tested before page_count |
480 | * here, then the following race may occur: |
481 | * |
482 | * get_user_pages(&page); |
483 | * [user mapping goes away] |
484 | * write_to(page); |
485 | * !PageDirty(page) [good] |
486 | * SetPageDirty(page); |
487 | * put_page(page); |
488 | * !page_count(page) [good, discard it] |
489 | * |
490 | * [oops, our write_to data is lost] |
491 | * |
492 | * Reversing the order of the tests ensures such a situation cannot |
493 | * escape unnoticed. The smp_rmb is needed to ensure the page->flags |
494 | * load is not satisfied before that of page->_count. |
495 | * |
496 | * Note that if SetPageDirty is always performed via set_page_dirty, |
497 | * and thus under tree_lock, then this ordering is not required. |
498 | */ |
499 | if (!page_freeze_refs(page, 2)) |
500 | goto cannot_free; |
501 | /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ |
502 | if (unlikely(PageDirty(page))) { |
503 | page_unfreeze_refs(page, 2); |
504 | goto cannot_free; |
505 | } |
506 | |
507 | if (PageSwapCache(page)) { |
508 | swp_entry_t swap = { .val = page_private(page) }; |
509 | __delete_from_swap_cache(page); |
510 | spin_unlock_irq(&mapping->tree_lock); |
511 | swapcache_free(swap, page); |
512 | } else { |
513 | void (*freepage)(struct page *); |
514 | |
515 | freepage = mapping->a_ops->freepage; |
516 | |
517 | __remove_from_page_cache(page); |
518 | spin_unlock_irq(&mapping->tree_lock); |
519 | mem_cgroup_uncharge_cache_page(page); |
520 | |
521 | if (freepage != NULL) |
522 | freepage(page); |
523 | } |
524 | |
525 | return 1; |
526 | |
527 | cannot_free: |
528 | spin_unlock_irq(&mapping->tree_lock); |
529 | return 0; |
530 | } |
531 | |
532 | /* |
533 | * Attempt to detach a locked page from its ->mapping. If it is dirty or if |
534 | * someone else has a ref on the page, abort and return 0. If it was |
535 | * successfully detached, return 1. Assumes the caller has a single ref on |
536 | * this page. |
537 | */ |
538 | int remove_mapping(struct address_space *mapping, struct page *page) |
539 | { |
540 | if (__remove_mapping(mapping, page)) { |
541 | /* |
542 | * Unfreezing the refcount with 1 rather than 2 effectively |
543 | * drops the pagecache ref for us without requiring another |
544 | * atomic operation. |
545 | */ |
546 | page_unfreeze_refs(page, 1); |
547 | return 1; |
548 | } |
549 | return 0; |
550 | } |
551 | |
552 | /** |
553 | * putback_lru_page - put previously isolated page onto appropriate LRU list |
554 | * @page: page to be put back to appropriate lru list |
555 | * |
556 | * Add previously isolated @page to appropriate LRU list. |
557 | * Page may still be unevictable for other reasons. |
558 | * |
559 | * lru_lock must not be held, interrupts must be enabled. |
560 | */ |
561 | void putback_lru_page(struct page *page) |
562 | { |
563 | int lru; |
564 | int active = !!TestClearPageActive(page); |
565 | int was_unevictable = PageUnevictable(page); |
566 | |
567 | VM_BUG_ON(PageLRU(page)); |
568 | |
569 | redo: |
570 | ClearPageUnevictable(page); |
571 | |
572 | if (page_evictable(page, NULL)) { |
573 | /* |
574 | * For evictable pages, we can use the cache. |
575 | * In event of a race, worst case is we end up with an |
576 | * unevictable page on [in]active list. |
577 | * We know how to handle that. |
578 | */ |
579 | lru = active + page_lru_base_type(page); |
580 | lru_cache_add_lru(page, lru); |
581 | } else { |
582 | /* |
583 | * Put unevictable pages directly on zone's unevictable |
584 | * list. |
585 | */ |
586 | lru = LRU_UNEVICTABLE; |
587 | add_page_to_unevictable_list(page); |
588 | /* |
589 | * When racing with an mlock clearing (page is |
590 | * unlocked), make sure that if the other thread does |
591 | * not observe our setting of PG_lru and fails |
592 | * isolation, we see PG_mlocked cleared below and move |
593 | * the page back to the evictable list. |
594 | * |
595 | * The other side is TestClearPageMlocked(). |
596 | */ |
597 | smp_mb(); |
598 | } |
599 | |
600 | /* |
601 | * page's status can change while we move it among lru. If an evictable |
602 | * page is on unevictable list, it never be freed. To avoid that, |
603 | * check after we added it to the list, again. |
604 | */ |
605 | if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { |
606 | if (!isolate_lru_page(page)) { |
607 | put_page(page); |
608 | goto redo; |
609 | } |
610 | /* This means someone else dropped this page from LRU |
611 | * So, it will be freed or putback to LRU again. There is |
612 | * nothing to do here. |
613 | */ |
614 | } |
615 | |
616 | if (was_unevictable && lru != LRU_UNEVICTABLE) |
617 | count_vm_event(UNEVICTABLE_PGRESCUED); |
618 | else if (!was_unevictable && lru == LRU_UNEVICTABLE) |
619 | count_vm_event(UNEVICTABLE_PGCULLED); |
620 | |
621 | put_page(page); /* drop ref from isolate */ |
622 | } |
623 | |
624 | enum page_references { |
625 | PAGEREF_RECLAIM, |
626 | PAGEREF_RECLAIM_CLEAN, |
627 | PAGEREF_KEEP, |
628 | PAGEREF_ACTIVATE, |
629 | }; |
630 | |
631 | static enum page_references page_check_references(struct page *page, |
632 | struct scan_control *sc) |
633 | { |
634 | int referenced_ptes, referenced_page; |
635 | unsigned long vm_flags; |
636 | |
637 | referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags); |
638 | referenced_page = TestClearPageReferenced(page); |
639 | |
640 | /* Lumpy reclaim - ignore references */ |
641 | if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) |
642 | return PAGEREF_RECLAIM; |
643 | |
644 | /* |
645 | * Mlock lost the isolation race with us. Let try_to_unmap() |
646 | * move the page to the unevictable list. |
647 | */ |
648 | if (vm_flags & VM_LOCKED) |
649 | return PAGEREF_RECLAIM; |
650 | |
651 | if (referenced_ptes) { |
652 | if (PageAnon(page)) |
653 | return PAGEREF_ACTIVATE; |
654 | /* |
655 | * All mapped pages start out with page table |
656 | * references from the instantiating fault, so we need |
657 | * to look twice if a mapped file page is used more |
658 | * than once. |
659 | * |
660 | * Mark it and spare it for another trip around the |
661 | * inactive list. Another page table reference will |
662 | * lead to its activation. |
663 | * |
664 | * Note: the mark is set for activated pages as well |
665 | * so that recently deactivated but used pages are |
666 | * quickly recovered. |
667 | */ |
668 | SetPageReferenced(page); |
669 | |
670 | if (referenced_page) |
671 | return PAGEREF_ACTIVATE; |
672 | |
673 | return PAGEREF_KEEP; |
674 | } |
675 | |
676 | /* Reclaim if clean, defer dirty pages to writeback */ |
677 | if (referenced_page && !PageSwapBacked(page)) |
678 | return PAGEREF_RECLAIM_CLEAN; |
679 | |
680 | return PAGEREF_RECLAIM; |
681 | } |
682 | |
683 | static noinline_for_stack void free_page_list(struct list_head *free_pages) |
684 | { |
685 | struct pagevec freed_pvec; |
686 | struct page *page, *tmp; |
687 | |
688 | pagevec_init(&freed_pvec, 1); |
689 | |
690 | list_for_each_entry_safe(page, tmp, free_pages, lru) { |
691 | list_del(&page->lru); |
692 | if (!pagevec_add(&freed_pvec, page)) { |
693 | __pagevec_free(&freed_pvec); |
694 | pagevec_reinit(&freed_pvec); |
695 | } |
696 | } |
697 | |
698 | pagevec_free(&freed_pvec); |
699 | } |
700 | |
701 | /* |
702 | * shrink_page_list() returns the number of reclaimed pages |
703 | */ |
704 | static unsigned long shrink_page_list(struct list_head *page_list, |
705 | struct zone *zone, |
706 | struct scan_control *sc) |
707 | { |
708 | LIST_HEAD(ret_pages); |
709 | LIST_HEAD(free_pages); |
710 | int pgactivate = 0; |
711 | unsigned long nr_dirty = 0; |
712 | unsigned long nr_congested = 0; |
713 | unsigned long nr_reclaimed = 0; |
714 | |
715 | cond_resched(); |
716 | |
717 | while (!list_empty(page_list)) { |
718 | enum page_references references; |
719 | struct address_space *mapping; |
720 | struct page *page; |
721 | int may_enter_fs; |
722 | |
723 | cond_resched(); |
724 | |
725 | page = lru_to_page(page_list); |
726 | list_del(&page->lru); |
727 | |
728 | if (!trylock_page(page)) |
729 | goto keep; |
730 | |
731 | VM_BUG_ON(PageActive(page)); |
732 | VM_BUG_ON(page_zone(page) != zone); |
733 | |
734 | sc->nr_scanned++; |
735 | |
736 | if (unlikely(!page_evictable(page, NULL))) |
737 | goto cull_mlocked; |
738 | |
739 | if (!sc->may_unmap && page_mapped(page)) |
740 | goto keep_locked; |
741 | |
742 | /* Double the slab pressure for mapped and swapcache pages */ |
743 | if (page_mapped(page) || PageSwapCache(page)) |
744 | sc->nr_scanned++; |
745 | |
746 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || |
747 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); |
748 | |
749 | if (PageWriteback(page)) { |
750 | /* |
751 | * Synchronous reclaim is performed in two passes, |
752 | * first an asynchronous pass over the list to |
753 | * start parallel writeback, and a second synchronous |
754 | * pass to wait for the IO to complete. Wait here |
755 | * for any page for which writeback has already |
756 | * started. |
757 | */ |
758 | if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && |
759 | may_enter_fs) |
760 | wait_on_page_writeback(page); |
761 | else { |
762 | unlock_page(page); |
763 | goto keep_lumpy; |
764 | } |
765 | } |
766 | |
767 | references = page_check_references(page, sc); |
768 | switch (references) { |
769 | case PAGEREF_ACTIVATE: |
770 | goto activate_locked; |
771 | case PAGEREF_KEEP: |
772 | goto keep_locked; |
773 | case PAGEREF_RECLAIM: |
774 | case PAGEREF_RECLAIM_CLEAN: |
775 | ; /* try to reclaim the page below */ |
776 | } |
777 | |
778 | /* |
779 | * Anonymous process memory has backing store? |
780 | * Try to allocate it some swap space here. |
781 | */ |
782 | if (PageAnon(page) && !PageSwapCache(page)) { |
783 | if (!(sc->gfp_mask & __GFP_IO)) |
784 | goto keep_locked; |
785 | if (!add_to_swap(page)) |
786 | goto activate_locked; |
787 | may_enter_fs = 1; |
788 | } |
789 | |
790 | mapping = page_mapping(page); |
791 | |
792 | /* |
793 | * The page is mapped into the page tables of one or more |
794 | * processes. Try to unmap it here. |
795 | */ |
796 | if (page_mapped(page) && mapping) { |
797 | switch (try_to_unmap(page, TTU_UNMAP)) { |
798 | case SWAP_FAIL: |
799 | goto activate_locked; |
800 | case SWAP_AGAIN: |
801 | goto keep_locked; |
802 | case SWAP_MLOCK: |
803 | goto cull_mlocked; |
804 | case SWAP_SUCCESS: |
805 | ; /* try to free the page below */ |
806 | } |
807 | } |
808 | |
809 | if (PageDirty(page)) { |
810 | nr_dirty++; |
811 | |
812 | if (references == PAGEREF_RECLAIM_CLEAN) |
813 | goto keep_locked; |
814 | if (!may_enter_fs) |
815 | goto keep_locked; |
816 | if (!sc->may_writepage) |
817 | goto keep_locked; |
818 | |
819 | /* Page is dirty, try to write it out here */ |
820 | switch (pageout(page, mapping, sc)) { |
821 | case PAGE_KEEP: |
822 | nr_congested++; |
823 | goto keep_locked; |
824 | case PAGE_ACTIVATE: |
825 | goto activate_locked; |
826 | case PAGE_SUCCESS: |
827 | if (PageWriteback(page)) |
828 | goto keep_lumpy; |
829 | if (PageDirty(page)) |
830 | goto keep; |
831 | |
832 | /* |
833 | * A synchronous write - probably a ramdisk. Go |
834 | * ahead and try to reclaim the page. |
835 | */ |
836 | if (!trylock_page(page)) |
837 | goto keep; |
838 | if (PageDirty(page) || PageWriteback(page)) |
839 | goto keep_locked; |
840 | mapping = page_mapping(page); |
841 | case PAGE_CLEAN: |
842 | ; /* try to free the page below */ |
843 | } |
844 | } |
845 | |
846 | /* |
847 | * If the page has buffers, try to free the buffer mappings |
848 | * associated with this page. If we succeed we try to free |
849 | * the page as well. |
850 | * |
851 | * We do this even if the page is PageDirty(). |
852 | * try_to_release_page() does not perform I/O, but it is |
853 | * possible for a page to have PageDirty set, but it is actually |
854 | * clean (all its buffers are clean). This happens if the |
855 | * buffers were written out directly, with submit_bh(). ext3 |
856 | * will do this, as well as the blockdev mapping. |
857 | * try_to_release_page() will discover that cleanness and will |
858 | * drop the buffers and mark the page clean - it can be freed. |
859 | * |
860 | * Rarely, pages can have buffers and no ->mapping. These are |
861 | * the pages which were not successfully invalidated in |
862 | * truncate_complete_page(). We try to drop those buffers here |
863 | * and if that worked, and the page is no longer mapped into |
864 | * process address space (page_count == 1) it can be freed. |
865 | * Otherwise, leave the page on the LRU so it is swappable. |
866 | */ |
867 | if (page_has_private(page)) { |
868 | if (!try_to_release_page(page, sc->gfp_mask)) |
869 | goto activate_locked; |
870 | if (!mapping && page_count(page) == 1) { |
871 | unlock_page(page); |
872 | if (put_page_testzero(page)) |
873 | goto free_it; |
874 | else { |
875 | /* |
876 | * rare race with speculative reference. |
877 | * the speculative reference will free |
878 | * this page shortly, so we may |
879 | * increment nr_reclaimed here (and |
880 | * leave it off the LRU). |
881 | */ |
882 | nr_reclaimed++; |
883 | continue; |
884 | } |
885 | } |
886 | } |
887 | |
888 | if (!mapping || !__remove_mapping(mapping, page)) |
889 | goto keep_locked; |
890 | |
891 | /* |
892 | * At this point, we have no other references and there is |
893 | * no way to pick any more up (removed from LRU, removed |
894 | * from pagecache). Can use non-atomic bitops now (and |
895 | * we obviously don't have to worry about waking up a process |
896 | * waiting on the page lock, because there are no references. |
897 | */ |
898 | __clear_page_locked(page); |
899 | free_it: |
900 | nr_reclaimed++; |
901 | |
902 | /* |
903 | * Is there need to periodically free_page_list? It would |
904 | * appear not as the counts should be low |
905 | */ |
906 | list_add(&page->lru, &free_pages); |
907 | continue; |
908 | |
909 | cull_mlocked: |
910 | if (PageSwapCache(page)) |
911 | try_to_free_swap(page); |
912 | unlock_page(page); |
913 | putback_lru_page(page); |
914 | reset_reclaim_mode(sc); |
915 | continue; |
916 | |
917 | activate_locked: |
918 | /* Not a candidate for swapping, so reclaim swap space. */ |
919 | if (PageSwapCache(page) && vm_swap_full()) |
920 | try_to_free_swap(page); |
921 | VM_BUG_ON(PageActive(page)); |
922 | SetPageActive(page); |
923 | pgactivate++; |
924 | keep_locked: |
925 | unlock_page(page); |
926 | keep: |
927 | reset_reclaim_mode(sc); |
928 | keep_lumpy: |
929 | list_add(&page->lru, &ret_pages); |
930 | VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); |
931 | } |
932 | |
933 | /* |
934 | * Tag a zone as congested if all the dirty pages encountered were |
935 | * backed by a congested BDI. In this case, reclaimers should just |
936 | * back off and wait for congestion to clear because further reclaim |
937 | * will encounter the same problem |
938 | */ |
939 | if (nr_dirty == nr_congested && nr_dirty != 0) |
940 | zone_set_flag(zone, ZONE_CONGESTED); |
941 | |
942 | free_page_list(&free_pages); |
943 | |
944 | list_splice(&ret_pages, page_list); |
945 | count_vm_events(PGACTIVATE, pgactivate); |
946 | return nr_reclaimed; |
947 | } |
948 | |
949 | /* |
950 | * Attempt to remove the specified page from its LRU. Only take this page |
951 | * if it is of the appropriate PageActive status. Pages which are being |
952 | * freed elsewhere are also ignored. |
953 | * |
954 | * page: page to consider |
955 | * mode: one of the LRU isolation modes defined above |
956 | * |
957 | * returns 0 on success, -ve errno on failure. |
958 | */ |
959 | int __isolate_lru_page(struct page *page, int mode, int file) |
960 | { |
961 | int ret = -EINVAL; |
962 | |
963 | /* Only take pages on the LRU. */ |
964 | if (!PageLRU(page)) |
965 | return ret; |
966 | |
967 | /* |
968 | * When checking the active state, we need to be sure we are |
969 | * dealing with comparible boolean values. Take the logical not |
970 | * of each. |
971 | */ |
972 | if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) |
973 | return ret; |
974 | |
975 | if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) |
976 | return ret; |
977 | |
978 | /* |
979 | * When this function is being called for lumpy reclaim, we |
980 | * initially look into all LRU pages, active, inactive and |
981 | * unevictable; only give shrink_page_list evictable pages. |
982 | */ |
983 | if (PageUnevictable(page)) |
984 | return ret; |
985 | |
986 | ret = -EBUSY; |
987 | |
988 | if (likely(get_page_unless_zero(page))) { |
989 | /* |
990 | * Be careful not to clear PageLRU until after we're |
991 | * sure the page is not being freed elsewhere -- the |
992 | * page release code relies on it. |
993 | */ |
994 | ClearPageLRU(page); |
995 | ret = 0; |
996 | } |
997 | |
998 | return ret; |
999 | } |
1000 | |
1001 | /* |
1002 | * zone->lru_lock is heavily contended. Some of the functions that |
1003 | * shrink the lists perform better by taking out a batch of pages |
1004 | * and working on them outside the LRU lock. |
1005 | * |
1006 | * For pagecache intensive workloads, this function is the hottest |
1007 | * spot in the kernel (apart from copy_*_user functions). |
1008 | * |
1009 | * Appropriate locks must be held before calling this function. |
1010 | * |
1011 | * @nr_to_scan: The number of pages to look through on the list. |
1012 | * @src: The LRU list to pull pages off. |
1013 | * @dst: The temp list to put pages on to. |
1014 | * @scanned: The number of pages that were scanned. |
1015 | * @order: The caller's attempted allocation order |
1016 | * @mode: One of the LRU isolation modes |
1017 | * @file: True [1] if isolating file [!anon] pages |
1018 | * |
1019 | * returns how many pages were moved onto *@dst. |
1020 | */ |
1021 | static unsigned long isolate_lru_pages(unsigned long nr_to_scan, |
1022 | struct list_head *src, struct list_head *dst, |
1023 | unsigned long *scanned, int order, int mode, int file) |
1024 | { |
1025 | unsigned long nr_taken = 0; |
1026 | unsigned long nr_lumpy_taken = 0; |
1027 | unsigned long nr_lumpy_dirty = 0; |
1028 | unsigned long nr_lumpy_failed = 0; |
1029 | unsigned long scan; |
1030 | |
1031 | for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { |
1032 | struct page *page; |
1033 | unsigned long pfn; |
1034 | unsigned long end_pfn; |
1035 | unsigned long page_pfn; |
1036 | int zone_id; |
1037 | |
1038 | page = lru_to_page(src); |
1039 | prefetchw_prev_lru_page(page, src, flags); |
1040 | |
1041 | VM_BUG_ON(!PageLRU(page)); |
1042 | |
1043 | switch (__isolate_lru_page(page, mode, file)) { |
1044 | case 0: |
1045 | list_move(&page->lru, dst); |
1046 | mem_cgroup_del_lru(page); |
1047 | nr_taken += hpage_nr_pages(page); |
1048 | break; |
1049 | |
1050 | case -EBUSY: |
1051 | /* else it is being freed elsewhere */ |
1052 | list_move(&page->lru, src); |
1053 | mem_cgroup_rotate_lru_list(page, page_lru(page)); |
1054 | continue; |
1055 | |
1056 | default: |
1057 | BUG(); |
1058 | } |
1059 | |
1060 | if (!order) |
1061 | continue; |
1062 | |
1063 | /* |
1064 | * Attempt to take all pages in the order aligned region |
1065 | * surrounding the tag page. Only take those pages of |
1066 | * the same active state as that tag page. We may safely |
1067 | * round the target page pfn down to the requested order |
1068 | * as the mem_map is guarenteed valid out to MAX_ORDER, |
1069 | * where that page is in a different zone we will detect |
1070 | * it from its zone id and abort this block scan. |
1071 | */ |
1072 | zone_id = page_zone_id(page); |
1073 | page_pfn = page_to_pfn(page); |
1074 | pfn = page_pfn & ~((1 << order) - 1); |
1075 | end_pfn = pfn + (1 << order); |
1076 | for (; pfn < end_pfn; pfn++) { |
1077 | struct page *cursor_page; |
1078 | |
1079 | /* The target page is in the block, ignore it. */ |
1080 | if (unlikely(pfn == page_pfn)) |
1081 | continue; |
1082 | |
1083 | /* Avoid holes within the zone. */ |
1084 | if (unlikely(!pfn_valid_within(pfn))) |
1085 | break; |
1086 | |
1087 | cursor_page = pfn_to_page(pfn); |
1088 | |
1089 | /* Check that we have not crossed a zone boundary. */ |
1090 | if (unlikely(page_zone_id(cursor_page) != zone_id)) |
1091 | break; |
1092 | |
1093 | /* |
1094 | * If we don't have enough swap space, reclaiming of |
1095 | * anon page which don't already have a swap slot is |
1096 | * pointless. |
1097 | */ |
1098 | if (nr_swap_pages <= 0 && PageAnon(cursor_page) && |
1099 | !PageSwapCache(cursor_page)) |
1100 | break; |
1101 | |
1102 | if (__isolate_lru_page(cursor_page, mode, file) == 0) { |
1103 | list_move(&cursor_page->lru, dst); |
1104 | mem_cgroup_del_lru(cursor_page); |
1105 | nr_taken += hpage_nr_pages(page); |
1106 | nr_lumpy_taken++; |
1107 | if (PageDirty(cursor_page)) |
1108 | nr_lumpy_dirty++; |
1109 | scan++; |
1110 | } else { |
1111 | /* the page is freed already. */ |
1112 | if (!page_count(cursor_page)) |
1113 | continue; |
1114 | break; |
1115 | } |
1116 | } |
1117 | |
1118 | /* If we break out of the loop above, lumpy reclaim failed */ |
1119 | if (pfn < end_pfn) |
1120 | nr_lumpy_failed++; |
1121 | } |
1122 | |
1123 | *scanned = scan; |
1124 | |
1125 | trace_mm_vmscan_lru_isolate(order, |
1126 | nr_to_scan, scan, |
1127 | nr_taken, |
1128 | nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, |
1129 | mode); |
1130 | return nr_taken; |
1131 | } |
1132 | |
1133 | static unsigned long isolate_pages_global(unsigned long nr, |
1134 | struct list_head *dst, |
1135 | unsigned long *scanned, int order, |
1136 | int mode, struct zone *z, |
1137 | int active, int file) |
1138 | { |
1139 | int lru = LRU_BASE; |
1140 | if (active) |
1141 | lru += LRU_ACTIVE; |
1142 | if (file) |
1143 | lru += LRU_FILE; |
1144 | return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, |
1145 | mode, file); |
1146 | } |
1147 | |
1148 | /* |
1149 | * clear_active_flags() is a helper for shrink_active_list(), clearing |
1150 | * any active bits from the pages in the list. |
1151 | */ |
1152 | static unsigned long clear_active_flags(struct list_head *page_list, |
1153 | unsigned int *count) |
1154 | { |
1155 | int nr_active = 0; |
1156 | int lru; |
1157 | struct page *page; |
1158 | |
1159 | list_for_each_entry(page, page_list, lru) { |
1160 | int numpages = hpage_nr_pages(page); |
1161 | lru = page_lru_base_type(page); |
1162 | if (PageActive(page)) { |
1163 | lru += LRU_ACTIVE; |
1164 | ClearPageActive(page); |
1165 | nr_active += numpages; |
1166 | } |
1167 | if (count) |
1168 | count[lru] += numpages; |
1169 | } |
1170 | |
1171 | return nr_active; |
1172 | } |
1173 | |
1174 | /** |
1175 | * isolate_lru_page - tries to isolate a page from its LRU list |
1176 | * @page: page to isolate from its LRU list |
1177 | * |
1178 | * Isolates a @page from an LRU list, clears PageLRU and adjusts the |
1179 | * vmstat statistic corresponding to whatever LRU list the page was on. |
1180 | * |
1181 | * Returns 0 if the page was removed from an LRU list. |
1182 | * Returns -EBUSY if the page was not on an LRU list. |
1183 | * |
1184 | * The returned page will have PageLRU() cleared. If it was found on |
1185 | * the active list, it will have PageActive set. If it was found on |
1186 | * the unevictable list, it will have the PageUnevictable bit set. That flag |
1187 | * may need to be cleared by the caller before letting the page go. |
1188 | * |
1189 | * The vmstat statistic corresponding to the list on which the page was |
1190 | * found will be decremented. |
1191 | * |
1192 | * Restrictions: |
1193 | * (1) Must be called with an elevated refcount on the page. This is a |
1194 | * fundamentnal difference from isolate_lru_pages (which is called |
1195 | * without a stable reference). |
1196 | * (2) the lru_lock must not be held. |
1197 | * (3) interrupts must be enabled. |
1198 | */ |
1199 | int isolate_lru_page(struct page *page) |
1200 | { |
1201 | int ret = -EBUSY; |
1202 | |
1203 | if (PageLRU(page)) { |
1204 | struct zone *zone = page_zone(page); |
1205 | |
1206 | spin_lock_irq(&zone->lru_lock); |
1207 | if (PageLRU(page) && get_page_unless_zero(page)) { |
1208 | int lru = page_lru(page); |
1209 | ret = 0; |
1210 | ClearPageLRU(page); |
1211 | |
1212 | del_page_from_lru_list(zone, page, lru); |
1213 | } |
1214 | spin_unlock_irq(&zone->lru_lock); |
1215 | } |
1216 | return ret; |
1217 | } |
1218 | |
1219 | /* |
1220 | * Are there way too many processes in the direct reclaim path already? |
1221 | */ |
1222 | static int too_many_isolated(struct zone *zone, int file, |
1223 | struct scan_control *sc) |
1224 | { |
1225 | unsigned long inactive, isolated; |
1226 | |
1227 | if (current_is_kswapd()) |
1228 | return 0; |
1229 | |
1230 | if (!scanning_global_lru(sc)) |
1231 | return 0; |
1232 | |
1233 | if (file) { |
1234 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); |
1235 | isolated = zone_page_state(zone, NR_ISOLATED_FILE); |
1236 | } else { |
1237 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
1238 | isolated = zone_page_state(zone, NR_ISOLATED_ANON); |
1239 | } |
1240 | |
1241 | return isolated > inactive; |
1242 | } |
1243 | |
1244 | /* |
1245 | * TODO: Try merging with migrations version of putback_lru_pages |
1246 | */ |
1247 | static noinline_for_stack void |
1248 | putback_lru_pages(struct zone *zone, struct scan_control *sc, |
1249 | unsigned long nr_anon, unsigned long nr_file, |
1250 | struct list_head *page_list) |
1251 | { |
1252 | struct page *page; |
1253 | struct pagevec pvec; |
1254 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
1255 | |
1256 | pagevec_init(&pvec, 1); |
1257 | |
1258 | /* |
1259 | * Put back any unfreeable pages. |
1260 | */ |
1261 | spin_lock(&zone->lru_lock); |
1262 | while (!list_empty(page_list)) { |
1263 | int lru; |
1264 | page = lru_to_page(page_list); |
1265 | VM_BUG_ON(PageLRU(page)); |
1266 | list_del(&page->lru); |
1267 | if (unlikely(!page_evictable(page, NULL))) { |
1268 | spin_unlock_irq(&zone->lru_lock); |
1269 | putback_lru_page(page); |
1270 | spin_lock_irq(&zone->lru_lock); |
1271 | continue; |
1272 | } |
1273 | SetPageLRU(page); |
1274 | lru = page_lru(page); |
1275 | add_page_to_lru_list(zone, page, lru); |
1276 | if (is_active_lru(lru)) { |
1277 | int file = is_file_lru(lru); |
1278 | int numpages = hpage_nr_pages(page); |
1279 | reclaim_stat->recent_rotated[file] += numpages; |
1280 | } |
1281 | if (!pagevec_add(&pvec, page)) { |
1282 | spin_unlock_irq(&zone->lru_lock); |
1283 | __pagevec_release(&pvec); |
1284 | spin_lock_irq(&zone->lru_lock); |
1285 | } |
1286 | } |
1287 | __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); |
1288 | __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); |
1289 | |
1290 | spin_unlock_irq(&zone->lru_lock); |
1291 | pagevec_release(&pvec); |
1292 | } |
1293 | |
1294 | static noinline_for_stack void update_isolated_counts(struct zone *zone, |
1295 | struct scan_control *sc, |
1296 | unsigned long *nr_anon, |
1297 | unsigned long *nr_file, |
1298 | struct list_head *isolated_list) |
1299 | { |
1300 | unsigned long nr_active; |
1301 | unsigned int count[NR_LRU_LISTS] = { 0, }; |
1302 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
1303 | |
1304 | nr_active = clear_active_flags(isolated_list, count); |
1305 | __count_vm_events(PGDEACTIVATE, nr_active); |
1306 | |
1307 | __mod_zone_page_state(zone, NR_ACTIVE_FILE, |
1308 | -count[LRU_ACTIVE_FILE]); |
1309 | __mod_zone_page_state(zone, NR_INACTIVE_FILE, |
1310 | -count[LRU_INACTIVE_FILE]); |
1311 | __mod_zone_page_state(zone, NR_ACTIVE_ANON, |
1312 | -count[LRU_ACTIVE_ANON]); |
1313 | __mod_zone_page_state(zone, NR_INACTIVE_ANON, |
1314 | -count[LRU_INACTIVE_ANON]); |
1315 | |
1316 | *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; |
1317 | *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; |
1318 | __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); |
1319 | __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); |
1320 | |
1321 | reclaim_stat->recent_scanned[0] += *nr_anon; |
1322 | reclaim_stat->recent_scanned[1] += *nr_file; |
1323 | } |
1324 | |
1325 | /* |
1326 | * Returns true if the caller should wait to clean dirty/writeback pages. |
1327 | * |
1328 | * If we are direct reclaiming for contiguous pages and we do not reclaim |
1329 | * everything in the list, try again and wait for writeback IO to complete. |
1330 | * This will stall high-order allocations noticeably. Only do that when really |
1331 | * need to free the pages under high memory pressure. |
1332 | */ |
1333 | static inline bool should_reclaim_stall(unsigned long nr_taken, |
1334 | unsigned long nr_freed, |
1335 | int priority, |
1336 | struct scan_control *sc) |
1337 | { |
1338 | int lumpy_stall_priority; |
1339 | |
1340 | /* kswapd should not stall on sync IO */ |
1341 | if (current_is_kswapd()) |
1342 | return false; |
1343 | |
1344 | /* Only stall on lumpy reclaim */ |
1345 | if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) |
1346 | return false; |
1347 | |
1348 | /* If we have relaimed everything on the isolated list, no stall */ |
1349 | if (nr_freed == nr_taken) |
1350 | return false; |
1351 | |
1352 | /* |
1353 | * For high-order allocations, there are two stall thresholds. |
1354 | * High-cost allocations stall immediately where as lower |
1355 | * order allocations such as stacks require the scanning |
1356 | * priority to be much higher before stalling. |
1357 | */ |
1358 | if (sc->order > PAGE_ALLOC_COSTLY_ORDER) |
1359 | lumpy_stall_priority = DEF_PRIORITY; |
1360 | else |
1361 | lumpy_stall_priority = DEF_PRIORITY / 3; |
1362 | |
1363 | return priority <= lumpy_stall_priority; |
1364 | } |
1365 | |
1366 | /* |
1367 | * shrink_inactive_list() is a helper for shrink_zone(). It returns the number |
1368 | * of reclaimed pages |
1369 | */ |
1370 | static noinline_for_stack unsigned long |
1371 | shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, |
1372 | struct scan_control *sc, int priority, int file) |
1373 | { |
1374 | LIST_HEAD(page_list); |
1375 | unsigned long nr_scanned; |
1376 | unsigned long nr_reclaimed = 0; |
1377 | unsigned long nr_taken; |
1378 | unsigned long nr_anon; |
1379 | unsigned long nr_file; |
1380 | |
1381 | while (unlikely(too_many_isolated(zone, file, sc))) { |
1382 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
1383 | |
1384 | /* We are about to die and free our memory. Return now. */ |
1385 | if (fatal_signal_pending(current)) |
1386 | return SWAP_CLUSTER_MAX; |
1387 | } |
1388 | |
1389 | set_reclaim_mode(priority, sc, false); |
1390 | lru_add_drain(); |
1391 | spin_lock_irq(&zone->lru_lock); |
1392 | |
1393 | if (scanning_global_lru(sc)) { |
1394 | nr_taken = isolate_pages_global(nr_to_scan, |
1395 | &page_list, &nr_scanned, sc->order, |
1396 | sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? |
1397 | ISOLATE_BOTH : ISOLATE_INACTIVE, |
1398 | zone, 0, file); |
1399 | zone->pages_scanned += nr_scanned; |
1400 | if (current_is_kswapd()) |
1401 | __count_zone_vm_events(PGSCAN_KSWAPD, zone, |
1402 | nr_scanned); |
1403 | else |
1404 | __count_zone_vm_events(PGSCAN_DIRECT, zone, |
1405 | nr_scanned); |
1406 | } else { |
1407 | nr_taken = mem_cgroup_isolate_pages(nr_to_scan, |
1408 | &page_list, &nr_scanned, sc->order, |
1409 | sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? |
1410 | ISOLATE_BOTH : ISOLATE_INACTIVE, |
1411 | zone, sc->mem_cgroup, |
1412 | 0, file); |
1413 | /* |
1414 | * mem_cgroup_isolate_pages() keeps track of |
1415 | * scanned pages on its own. |
1416 | */ |
1417 | } |
1418 | |
1419 | if (nr_taken == 0) { |
1420 | spin_unlock_irq(&zone->lru_lock); |
1421 | return 0; |
1422 | } |
1423 | |
1424 | update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list); |
1425 | |
1426 | spin_unlock_irq(&zone->lru_lock); |
1427 | |
1428 | nr_reclaimed = shrink_page_list(&page_list, zone, sc); |
1429 | |
1430 | /* Check if we should syncronously wait for writeback */ |
1431 | if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { |
1432 | set_reclaim_mode(priority, sc, true); |
1433 | nr_reclaimed += shrink_page_list(&page_list, zone, sc); |
1434 | } |
1435 | |
1436 | local_irq_disable(); |
1437 | if (current_is_kswapd()) |
1438 | __count_vm_events(KSWAPD_STEAL, nr_reclaimed); |
1439 | __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); |
1440 | |
1441 | putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); |
1442 | |
1443 | trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, |
1444 | zone_idx(zone), |
1445 | nr_scanned, nr_reclaimed, |
1446 | priority, |
1447 | trace_shrink_flags(file, sc->reclaim_mode)); |
1448 | return nr_reclaimed; |
1449 | } |
1450 | |
1451 | /* |
1452 | * This moves pages from the active list to the inactive list. |
1453 | * |
1454 | * We move them the other way if the page is referenced by one or more |
1455 | * processes, from rmap. |
1456 | * |
1457 | * If the pages are mostly unmapped, the processing is fast and it is |
1458 | * appropriate to hold zone->lru_lock across the whole operation. But if |
1459 | * the pages are mapped, the processing is slow (page_referenced()) so we |
1460 | * should drop zone->lru_lock around each page. It's impossible to balance |
1461 | * this, so instead we remove the pages from the LRU while processing them. |
1462 | * It is safe to rely on PG_active against the non-LRU pages in here because |
1463 | * nobody will play with that bit on a non-LRU page. |
1464 | * |
1465 | * The downside is that we have to touch page->_count against each page. |
1466 | * But we had to alter page->flags anyway. |
1467 | */ |
1468 | |
1469 | static void move_active_pages_to_lru(struct zone *zone, |
1470 | struct list_head *list, |
1471 | enum lru_list lru) |
1472 | { |
1473 | unsigned long pgmoved = 0; |
1474 | struct pagevec pvec; |
1475 | struct page *page; |
1476 | |
1477 | pagevec_init(&pvec, 1); |
1478 | |
1479 | while (!list_empty(list)) { |
1480 | page = lru_to_page(list); |
1481 | |
1482 | VM_BUG_ON(PageLRU(page)); |
1483 | SetPageLRU(page); |
1484 | |
1485 | list_move(&page->lru, &zone->lru[lru].list); |
1486 | mem_cgroup_add_lru_list(page, lru); |
1487 | pgmoved += hpage_nr_pages(page); |
1488 | |
1489 | if (!pagevec_add(&pvec, page) || list_empty(list)) { |
1490 | spin_unlock_irq(&zone->lru_lock); |
1491 | if (buffer_heads_over_limit) |
1492 | pagevec_strip(&pvec); |
1493 | __pagevec_release(&pvec); |
1494 | spin_lock_irq(&zone->lru_lock); |
1495 | } |
1496 | } |
1497 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); |
1498 | if (!is_active_lru(lru)) |
1499 | __count_vm_events(PGDEACTIVATE, pgmoved); |
1500 | } |
1501 | |
1502 | static void shrink_active_list(unsigned long nr_pages, struct zone *zone, |
1503 | struct scan_control *sc, int priority, int file) |
1504 | { |
1505 | unsigned long nr_taken; |
1506 | unsigned long pgscanned; |
1507 | unsigned long vm_flags; |
1508 | LIST_HEAD(l_hold); /* The pages which were snipped off */ |
1509 | LIST_HEAD(l_active); |
1510 | LIST_HEAD(l_inactive); |
1511 | struct page *page; |
1512 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
1513 | unsigned long nr_rotated = 0; |
1514 | |
1515 | lru_add_drain(); |
1516 | spin_lock_irq(&zone->lru_lock); |
1517 | if (scanning_global_lru(sc)) { |
1518 | nr_taken = isolate_pages_global(nr_pages, &l_hold, |
1519 | &pgscanned, sc->order, |
1520 | ISOLATE_ACTIVE, zone, |
1521 | 1, file); |
1522 | zone->pages_scanned += pgscanned; |
1523 | } else { |
1524 | nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold, |
1525 | &pgscanned, sc->order, |
1526 | ISOLATE_ACTIVE, zone, |
1527 | sc->mem_cgroup, 1, file); |
1528 | /* |
1529 | * mem_cgroup_isolate_pages() keeps track of |
1530 | * scanned pages on its own. |
1531 | */ |
1532 | } |
1533 | |
1534 | reclaim_stat->recent_scanned[file] += nr_taken; |
1535 | |
1536 | __count_zone_vm_events(PGREFILL, zone, pgscanned); |
1537 | if (file) |
1538 | __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); |
1539 | else |
1540 | __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); |
1541 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); |
1542 | spin_unlock_irq(&zone->lru_lock); |
1543 | |
1544 | while (!list_empty(&l_hold)) { |
1545 | cond_resched(); |
1546 | page = lru_to_page(&l_hold); |
1547 | list_del(&page->lru); |
1548 | |
1549 | if (unlikely(!page_evictable(page, NULL))) { |
1550 | putback_lru_page(page); |
1551 | continue; |
1552 | } |
1553 | |
1554 | if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { |
1555 | nr_rotated += hpage_nr_pages(page); |
1556 | /* |
1557 | * Identify referenced, file-backed active pages and |
1558 | * give them one more trip around the active list. So |
1559 | * that executable code get better chances to stay in |
1560 | * memory under moderate memory pressure. Anon pages |
1561 | * are not likely to be evicted by use-once streaming |
1562 | * IO, plus JVM can create lots of anon VM_EXEC pages, |
1563 | * so we ignore them here. |
1564 | */ |
1565 | if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { |
1566 | list_add(&page->lru, &l_active); |
1567 | continue; |
1568 | } |
1569 | } |
1570 | |
1571 | ClearPageActive(page); /* we are de-activating */ |
1572 | list_add(&page->lru, &l_inactive); |
1573 | } |
1574 | |
1575 | /* |
1576 | * Move pages back to the lru list. |
1577 | */ |
1578 | spin_lock_irq(&zone->lru_lock); |
1579 | /* |
1580 | * Count referenced pages from currently used mappings as rotated, |
1581 | * even though only some of them are actually re-activated. This |
1582 | * helps balance scan pressure between file and anonymous pages in |
1583 | * get_scan_ratio. |
1584 | */ |
1585 | reclaim_stat->recent_rotated[file] += nr_rotated; |
1586 | |
1587 | move_active_pages_to_lru(zone, &l_active, |
1588 | LRU_ACTIVE + file * LRU_FILE); |
1589 | move_active_pages_to_lru(zone, &l_inactive, |
1590 | LRU_BASE + file * LRU_FILE); |
1591 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); |
1592 | spin_unlock_irq(&zone->lru_lock); |
1593 | } |
1594 | |
1595 | #ifdef CONFIG_SWAP |
1596 | static int inactive_anon_is_low_global(struct zone *zone) |
1597 | { |
1598 | unsigned long active, inactive; |
1599 | |
1600 | active = zone_page_state(zone, NR_ACTIVE_ANON); |
1601 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
1602 | |
1603 | if (inactive * zone->inactive_ratio < active) |
1604 | return 1; |
1605 | |
1606 | return 0; |
1607 | } |
1608 | |
1609 | /** |
1610 | * inactive_anon_is_low - check if anonymous pages need to be deactivated |
1611 | * @zone: zone to check |
1612 | * @sc: scan control of this context |
1613 | * |
1614 | * Returns true if the zone does not have enough inactive anon pages, |
1615 | * meaning some active anon pages need to be deactivated. |
1616 | */ |
1617 | static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) |
1618 | { |
1619 | int low; |
1620 | |
1621 | /* |
1622 | * If we don't have swap space, anonymous page deactivation |
1623 | * is pointless. |
1624 | */ |
1625 | if (!total_swap_pages) |
1626 | return 0; |
1627 | |
1628 | if (scanning_global_lru(sc)) |
1629 | low = inactive_anon_is_low_global(zone); |
1630 | else |
1631 | low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); |
1632 | return low; |
1633 | } |
1634 | #else |
1635 | static inline int inactive_anon_is_low(struct zone *zone, |
1636 | struct scan_control *sc) |
1637 | { |
1638 | return 0; |
1639 | } |
1640 | #endif |
1641 | |
1642 | static int inactive_file_is_low_global(struct zone *zone) |
1643 | { |
1644 | unsigned long active, inactive; |
1645 | |
1646 | active = zone_page_state(zone, NR_ACTIVE_FILE); |
1647 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); |
1648 | |
1649 | return (active > inactive); |
1650 | } |
1651 | |
1652 | /** |
1653 | * inactive_file_is_low - check if file pages need to be deactivated |
1654 | * @zone: zone to check |
1655 | * @sc: scan control of this context |
1656 | * |
1657 | * When the system is doing streaming IO, memory pressure here |
1658 | * ensures that active file pages get deactivated, until more |
1659 | * than half of the file pages are on the inactive list. |
1660 | * |
1661 | * Once we get to that situation, protect the system's working |
1662 | * set from being evicted by disabling active file page aging. |
1663 | * |
1664 | * This uses a different ratio than the anonymous pages, because |
1665 | * the page cache uses a use-once replacement algorithm. |
1666 | */ |
1667 | static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) |
1668 | { |
1669 | int low; |
1670 | |
1671 | if (scanning_global_lru(sc)) |
1672 | low = inactive_file_is_low_global(zone); |
1673 | else |
1674 | low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); |
1675 | return low; |
1676 | } |
1677 | |
1678 | static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, |
1679 | int file) |
1680 | { |
1681 | if (file) |
1682 | return inactive_file_is_low(zone, sc); |
1683 | else |
1684 | return inactive_anon_is_low(zone, sc); |
1685 | } |
1686 | |
1687 | static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, |
1688 | struct zone *zone, struct scan_control *sc, int priority) |
1689 | { |
1690 | int file = is_file_lru(lru); |
1691 | |
1692 | if (is_active_lru(lru)) { |
1693 | if (inactive_list_is_low(zone, sc, file)) |
1694 | shrink_active_list(nr_to_scan, zone, sc, priority, file); |
1695 | return 0; |
1696 | } |
1697 | |
1698 | return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); |
1699 | } |
1700 | |
1701 | /* |
1702 | * Smallish @nr_to_scan's are deposited in @nr_saved_scan, |
1703 | * until we collected @swap_cluster_max pages to scan. |
1704 | */ |
1705 | static unsigned long nr_scan_try_batch(unsigned long nr_to_scan, |
1706 | unsigned long *nr_saved_scan) |
1707 | { |
1708 | unsigned long nr; |
1709 | |
1710 | *nr_saved_scan += nr_to_scan; |
1711 | nr = *nr_saved_scan; |
1712 | |
1713 | if (nr >= SWAP_CLUSTER_MAX) |
1714 | *nr_saved_scan = 0; |
1715 | else |
1716 | nr = 0; |
1717 | |
1718 | return nr; |
1719 | } |
1720 | |
1721 | /* |
1722 | * Determine how aggressively the anon and file LRU lists should be |
1723 | * scanned. The relative value of each set of LRU lists is determined |
1724 | * by looking at the fraction of the pages scanned we did rotate back |
1725 | * onto the active list instead of evict. |
1726 | * |
1727 | * nr[0] = anon pages to scan; nr[1] = file pages to scan |
1728 | */ |
1729 | static void get_scan_count(struct zone *zone, struct scan_control *sc, |
1730 | unsigned long *nr, int priority) |
1731 | { |
1732 | unsigned long anon, file, free; |
1733 | unsigned long anon_prio, file_prio; |
1734 | unsigned long ap, fp; |
1735 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
1736 | u64 fraction[2], denominator; |
1737 | enum lru_list l; |
1738 | int noswap = 0; |
1739 | |
1740 | /* If we have no swap space, do not bother scanning anon pages. */ |
1741 | if (!sc->may_swap || (nr_swap_pages <= 0)) { |
1742 | noswap = 1; |
1743 | fraction[0] = 0; |
1744 | fraction[1] = 1; |
1745 | denominator = 1; |
1746 | goto out; |
1747 | } |
1748 | |
1749 | anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + |
1750 | zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); |
1751 | file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + |
1752 | zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); |
1753 | |
1754 | if (scanning_global_lru(sc)) { |
1755 | free = zone_page_state(zone, NR_FREE_PAGES); |
1756 | /* If we have very few page cache pages, |
1757 | force-scan anon pages. */ |
1758 | if (unlikely(file + free <= high_wmark_pages(zone))) { |
1759 | fraction[0] = 1; |
1760 | fraction[1] = 0; |
1761 | denominator = 1; |
1762 | goto out; |
1763 | } |
1764 | } |
1765 | |
1766 | /* |
1767 | * With swappiness at 100, anonymous and file have the same priority. |
1768 | * This scanning priority is essentially the inverse of IO cost. |
1769 | */ |
1770 | anon_prio = sc->swappiness; |
1771 | file_prio = 200 - sc->swappiness; |
1772 | |
1773 | /* |
1774 | * OK, so we have swap space and a fair amount of page cache |
1775 | * pages. We use the recently rotated / recently scanned |
1776 | * ratios to determine how valuable each cache is. |
1777 | * |
1778 | * Because workloads change over time (and to avoid overflow) |
1779 | * we keep these statistics as a floating average, which ends |
1780 | * up weighing recent references more than old ones. |
1781 | * |
1782 | * anon in [0], file in [1] |
1783 | */ |
1784 | spin_lock_irq(&zone->lru_lock); |
1785 | if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { |
1786 | reclaim_stat->recent_scanned[0] /= 2; |
1787 | reclaim_stat->recent_rotated[0] /= 2; |
1788 | } |
1789 | |
1790 | if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { |
1791 | reclaim_stat->recent_scanned[1] /= 2; |
1792 | reclaim_stat->recent_rotated[1] /= 2; |
1793 | } |
1794 | |
1795 | /* |
1796 | * The amount of pressure on anon vs file pages is inversely |
1797 | * proportional to the fraction of recently scanned pages on |
1798 | * each list that were recently referenced and in active use. |
1799 | */ |
1800 | ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); |
1801 | ap /= reclaim_stat->recent_rotated[0] + 1; |
1802 | |
1803 | fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); |
1804 | fp /= reclaim_stat->recent_rotated[1] + 1; |
1805 | spin_unlock_irq(&zone->lru_lock); |
1806 | |
1807 | fraction[0] = ap; |
1808 | fraction[1] = fp; |
1809 | denominator = ap + fp + 1; |
1810 | out: |
1811 | for_each_evictable_lru(l) { |
1812 | int file = is_file_lru(l); |
1813 | unsigned long scan; |
1814 | |
1815 | scan = zone_nr_lru_pages(zone, sc, l); |
1816 | if (priority || noswap) { |
1817 | scan >>= priority; |
1818 | scan = div64_u64(scan * fraction[file], denominator); |
1819 | } |
1820 | nr[l] = nr_scan_try_batch(scan, |
1821 | &reclaim_stat->nr_saved_scan[l]); |
1822 | } |
1823 | } |
1824 | |
1825 | /* |
1826 | * Reclaim/compaction depends on a number of pages being freed. To avoid |
1827 | * disruption to the system, a small number of order-0 pages continue to be |
1828 | * rotated and reclaimed in the normal fashion. However, by the time we get |
1829 | * back to the allocator and call try_to_compact_zone(), we ensure that |
1830 | * there are enough free pages for it to be likely successful |
1831 | */ |
1832 | static inline bool should_continue_reclaim(struct zone *zone, |
1833 | unsigned long nr_reclaimed, |
1834 | unsigned long nr_scanned, |
1835 | struct scan_control *sc) |
1836 | { |
1837 | unsigned long pages_for_compaction; |
1838 | unsigned long inactive_lru_pages; |
1839 | |
1840 | /* If not in reclaim/compaction mode, stop */ |
1841 | if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) |
1842 | return false; |
1843 | |
1844 | /* Consider stopping depending on scan and reclaim activity */ |
1845 | if (sc->gfp_mask & __GFP_REPEAT) { |
1846 | /* |
1847 | * For __GFP_REPEAT allocations, stop reclaiming if the |
1848 | * full LRU list has been scanned and we are still failing |
1849 | * to reclaim pages. This full LRU scan is potentially |
1850 | * expensive but a __GFP_REPEAT caller really wants to succeed |
1851 | */ |
1852 | if (!nr_reclaimed && !nr_scanned) |
1853 | return false; |
1854 | } else { |
1855 | /* |
1856 | * For non-__GFP_REPEAT allocations which can presumably |
1857 | * fail without consequence, stop if we failed to reclaim |
1858 | * any pages from the last SWAP_CLUSTER_MAX number of |
1859 | * pages that were scanned. This will return to the |
1860 | * caller faster at the risk reclaim/compaction and |
1861 | * the resulting allocation attempt fails |
1862 | */ |
1863 | if (!nr_reclaimed) |
1864 | return false; |
1865 | } |
1866 | |
1867 | /* |
1868 | * If we have not reclaimed enough pages for compaction and the |
1869 | * inactive lists are large enough, continue reclaiming |
1870 | */ |
1871 | pages_for_compaction = (2UL << sc->order); |
1872 | inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) + |
1873 | zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); |
1874 | if (sc->nr_reclaimed < pages_for_compaction && |
1875 | inactive_lru_pages > pages_for_compaction) |
1876 | return true; |
1877 | |
1878 | /* If compaction would go ahead or the allocation would succeed, stop */ |
1879 | switch (compaction_suitable(zone, sc->order)) { |
1880 | case COMPACT_PARTIAL: |
1881 | case COMPACT_CONTINUE: |
1882 | return false; |
1883 | default: |
1884 | return true; |
1885 | } |
1886 | } |
1887 | |
1888 | /* |
1889 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. |
1890 | */ |
1891 | static void shrink_zone(int priority, struct zone *zone, |
1892 | struct scan_control *sc) |
1893 | { |
1894 | unsigned long nr[NR_LRU_LISTS]; |
1895 | unsigned long nr_to_scan; |
1896 | enum lru_list l; |
1897 | unsigned long nr_reclaimed, nr_scanned; |
1898 | unsigned long nr_to_reclaim = sc->nr_to_reclaim; |
1899 | |
1900 | restart: |
1901 | nr_reclaimed = 0; |
1902 | nr_scanned = sc->nr_scanned; |
1903 | get_scan_count(zone, sc, nr, priority); |
1904 | |
1905 | while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || |
1906 | nr[LRU_INACTIVE_FILE]) { |
1907 | for_each_evictable_lru(l) { |
1908 | if (nr[l]) { |
1909 | nr_to_scan = min_t(unsigned long, |
1910 | nr[l], SWAP_CLUSTER_MAX); |
1911 | nr[l] -= nr_to_scan; |
1912 | |
1913 | nr_reclaimed += shrink_list(l, nr_to_scan, |
1914 | zone, sc, priority); |
1915 | } |
1916 | } |
1917 | /* |
1918 | * On large memory systems, scan >> priority can become |
1919 | * really large. This is fine for the starting priority; |
1920 | * we want to put equal scanning pressure on each zone. |
1921 | * However, if the VM has a harder time of freeing pages, |
1922 | * with multiple processes reclaiming pages, the total |
1923 | * freeing target can get unreasonably large. |
1924 | */ |
1925 | if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) |
1926 | break; |
1927 | } |
1928 | sc->nr_reclaimed += nr_reclaimed; |
1929 | |
1930 | /* |
1931 | * Even if we did not try to evict anon pages at all, we want to |
1932 | * rebalance the anon lru active/inactive ratio. |
1933 | */ |
1934 | if (inactive_anon_is_low(zone, sc)) |
1935 | shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); |
1936 | |
1937 | /* reclaim/compaction might need reclaim to continue */ |
1938 | if (should_continue_reclaim(zone, nr_reclaimed, |
1939 | sc->nr_scanned - nr_scanned, sc)) |
1940 | goto restart; |
1941 | |
1942 | throttle_vm_writeout(sc->gfp_mask); |
1943 | } |
1944 | |
1945 | /* |
1946 | * This is the direct reclaim path, for page-allocating processes. We only |
1947 | * try to reclaim pages from zones which will satisfy the caller's allocation |
1948 | * request. |
1949 | * |
1950 | * We reclaim from a zone even if that zone is over high_wmark_pages(zone). |
1951 | * Because: |
1952 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order |
1953 | * allocation or |
1954 | * b) The target zone may be at high_wmark_pages(zone) but the lower zones |
1955 | * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' |
1956 | * zone defense algorithm. |
1957 | * |
1958 | * If a zone is deemed to be full of pinned pages then just give it a light |
1959 | * scan then give up on it. |
1960 | */ |
1961 | static void shrink_zones(int priority, struct zonelist *zonelist, |
1962 | struct scan_control *sc) |
1963 | { |
1964 | struct zoneref *z; |
1965 | struct zone *zone; |
1966 | |
1967 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
1968 | gfp_zone(sc->gfp_mask), sc->nodemask) { |
1969 | if (!populated_zone(zone)) |
1970 | continue; |
1971 | /* |
1972 | * Take care memory controller reclaiming has small influence |
1973 | * to global LRU. |
1974 | */ |
1975 | if (scanning_global_lru(sc)) { |
1976 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
1977 | continue; |
1978 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
1979 | continue; /* Let kswapd poll it */ |
1980 | } |
1981 | |
1982 | shrink_zone(priority, zone, sc); |
1983 | } |
1984 | } |
1985 | |
1986 | static bool zone_reclaimable(struct zone *zone) |
1987 | { |
1988 | return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; |
1989 | } |
1990 | |
1991 | /* |
1992 | * As hibernation is going on, kswapd is freezed so that it can't mark |
1993 | * the zone into all_unreclaimable. It can't handle OOM during hibernation. |
1994 | * So let's check zone's unreclaimable in direct reclaim as well as kswapd. |
1995 | */ |
1996 | static bool all_unreclaimable(struct zonelist *zonelist, |
1997 | struct scan_control *sc) |
1998 | { |
1999 | struct zoneref *z; |
2000 | struct zone *zone; |
2001 | bool all_unreclaimable = true; |
2002 | |
2003 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
2004 | gfp_zone(sc->gfp_mask), sc->nodemask) { |
2005 | if (!populated_zone(zone)) |
2006 | continue; |
2007 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2008 | continue; |
2009 | if (zone_reclaimable(zone)) { |
2010 | all_unreclaimable = false; |
2011 | break; |
2012 | } |
2013 | } |
2014 | |
2015 | return all_unreclaimable; |
2016 | } |
2017 | |
2018 | /* |
2019 | * This is the main entry point to direct page reclaim. |
2020 | * |
2021 | * If a full scan of the inactive list fails to free enough memory then we |
2022 | * are "out of memory" and something needs to be killed. |
2023 | * |
2024 | * If the caller is !__GFP_FS then the probability of a failure is reasonably |
2025 | * high - the zone may be full of dirty or under-writeback pages, which this |
2026 | * caller can't do much about. We kick the writeback threads and take explicit |
2027 | * naps in the hope that some of these pages can be written. But if the |
2028 | * allocating task holds filesystem locks which prevent writeout this might not |
2029 | * work, and the allocation attempt will fail. |
2030 | * |
2031 | * returns: 0, if no pages reclaimed |
2032 | * else, the number of pages reclaimed |
2033 | */ |
2034 | static unsigned long do_try_to_free_pages(struct zonelist *zonelist, |
2035 | struct scan_control *sc) |
2036 | { |
2037 | int priority; |
2038 | unsigned long total_scanned = 0; |
2039 | struct reclaim_state *reclaim_state = current->reclaim_state; |
2040 | struct zoneref *z; |
2041 | struct zone *zone; |
2042 | unsigned long writeback_threshold; |
2043 | |
2044 | get_mems_allowed(); |
2045 | delayacct_freepages_start(); |
2046 | |
2047 | if (scanning_global_lru(sc)) |
2048 | count_vm_event(ALLOCSTALL); |
2049 | |
2050 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
2051 | sc->nr_scanned = 0; |
2052 | if (!priority) |
2053 | disable_swap_token(); |
2054 | shrink_zones(priority, zonelist, sc); |
2055 | /* |
2056 | * Don't shrink slabs when reclaiming memory from |
2057 | * over limit cgroups |
2058 | */ |
2059 | if (scanning_global_lru(sc)) { |
2060 | unsigned long lru_pages = 0; |
2061 | for_each_zone_zonelist(zone, z, zonelist, |
2062 | gfp_zone(sc->gfp_mask)) { |
2063 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2064 | continue; |
2065 | |
2066 | lru_pages += zone_reclaimable_pages(zone); |
2067 | } |
2068 | |
2069 | shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages); |
2070 | if (reclaim_state) { |
2071 | sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
2072 | reclaim_state->reclaimed_slab = 0; |
2073 | } |
2074 | } |
2075 | total_scanned += sc->nr_scanned; |
2076 | if (sc->nr_reclaimed >= sc->nr_to_reclaim) |
2077 | goto out; |
2078 | |
2079 | /* |
2080 | * Try to write back as many pages as we just scanned. This |
2081 | * tends to cause slow streaming writers to write data to the |
2082 | * disk smoothly, at the dirtying rate, which is nice. But |
2083 | * that's undesirable in laptop mode, where we *want* lumpy |
2084 | * writeout. So in laptop mode, write out the whole world. |
2085 | */ |
2086 | writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; |
2087 | if (total_scanned > writeback_threshold) { |
2088 | wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); |
2089 | sc->may_writepage = 1; |
2090 | } |
2091 | |
2092 | /* Take a nap, wait for some writeback to complete */ |
2093 | if (!sc->hibernation_mode && sc->nr_scanned && |
2094 | priority < DEF_PRIORITY - 2) { |
2095 | struct zone *preferred_zone; |
2096 | |
2097 | first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), |
2098 | &cpuset_current_mems_allowed, |
2099 | &preferred_zone); |
2100 | wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); |
2101 | } |
2102 | } |
2103 | |
2104 | out: |
2105 | delayacct_freepages_end(); |
2106 | put_mems_allowed(); |
2107 | |
2108 | if (sc->nr_reclaimed) |
2109 | return sc->nr_reclaimed; |
2110 | |
2111 | /* top priority shrink_zones still had more to do? don't OOM, then */ |
2112 | if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) |
2113 | return 1; |
2114 | |
2115 | return 0; |
2116 | } |
2117 | |
2118 | unsigned long try_to_free_pages(struct zonelist *zonelist, int order, |
2119 | gfp_t gfp_mask, nodemask_t *nodemask) |
2120 | { |
2121 | unsigned long nr_reclaimed; |
2122 | struct scan_control sc = { |
2123 | .gfp_mask = gfp_mask, |
2124 | .may_writepage = !laptop_mode, |
2125 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2126 | .may_unmap = 1, |
2127 | .may_swap = 1, |
2128 | .swappiness = vm_swappiness, |
2129 | .order = order, |
2130 | .mem_cgroup = NULL, |
2131 | .nodemask = nodemask, |
2132 | }; |
2133 | |
2134 | trace_mm_vmscan_direct_reclaim_begin(order, |
2135 | sc.may_writepage, |
2136 | gfp_mask); |
2137 | |
2138 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc); |
2139 | |
2140 | trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); |
2141 | |
2142 | return nr_reclaimed; |
2143 | } |
2144 | |
2145 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
2146 | |
2147 | unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, |
2148 | gfp_t gfp_mask, bool noswap, |
2149 | unsigned int swappiness, |
2150 | struct zone *zone) |
2151 | { |
2152 | struct scan_control sc = { |
2153 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2154 | .may_writepage = !laptop_mode, |
2155 | .may_unmap = 1, |
2156 | .may_swap = !noswap, |
2157 | .swappiness = swappiness, |
2158 | .order = 0, |
2159 | .mem_cgroup = mem, |
2160 | }; |
2161 | sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
2162 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); |
2163 | |
2164 | trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, |
2165 | sc.may_writepage, |
2166 | sc.gfp_mask); |
2167 | |
2168 | /* |
2169 | * NOTE: Although we can get the priority field, using it |
2170 | * here is not a good idea, since it limits the pages we can scan. |
2171 | * if we don't reclaim here, the shrink_zone from balance_pgdat |
2172 | * will pick up pages from other mem cgroup's as well. We hack |
2173 | * the priority and make it zero. |
2174 | */ |
2175 | shrink_zone(0, zone, &sc); |
2176 | |
2177 | trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); |
2178 | |
2179 | return sc.nr_reclaimed; |
2180 | } |
2181 | |
2182 | unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, |
2183 | gfp_t gfp_mask, |
2184 | bool noswap, |
2185 | unsigned int swappiness) |
2186 | { |
2187 | struct zonelist *zonelist; |
2188 | unsigned long nr_reclaimed; |
2189 | struct scan_control sc = { |
2190 | .may_writepage = !laptop_mode, |
2191 | .may_unmap = 1, |
2192 | .may_swap = !noswap, |
2193 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2194 | .swappiness = swappiness, |
2195 | .order = 0, |
2196 | .mem_cgroup = mem_cont, |
2197 | .nodemask = NULL, /* we don't care the placement */ |
2198 | }; |
2199 | |
2200 | sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
2201 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); |
2202 | zonelist = NODE_DATA(numa_node_id())->node_zonelists; |
2203 | |
2204 | trace_mm_vmscan_memcg_reclaim_begin(0, |
2205 | sc.may_writepage, |
2206 | sc.gfp_mask); |
2207 | |
2208 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc); |
2209 | |
2210 | trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); |
2211 | |
2212 | return nr_reclaimed; |
2213 | } |
2214 | #endif |
2215 | |
2216 | /* |
2217 | * pgdat_balanced is used when checking if a node is balanced for high-order |
2218 | * allocations. Only zones that meet watermarks and are in a zone allowed |
2219 | * by the callers classzone_idx are added to balanced_pages. The total of |
2220 | * balanced pages must be at least 25% of the zones allowed by classzone_idx |
2221 | * for the node to be considered balanced. Forcing all zones to be balanced |
2222 | * for high orders can cause excessive reclaim when there are imbalanced zones. |
2223 | * The choice of 25% is due to |
2224 | * o a 16M DMA zone that is balanced will not balance a zone on any |
2225 | * reasonable sized machine |
2226 | * o On all other machines, the top zone must be at least a reasonable |
2227 | * precentage of the middle zones. For example, on 32-bit x86, highmem |
2228 | * would need to be at least 256M for it to be balance a whole node. |
2229 | * Similarly, on x86-64 the Normal zone would need to be at least 1G |
2230 | * to balance a node on its own. These seemed like reasonable ratios. |
2231 | */ |
2232 | static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, |
2233 | int classzone_idx) |
2234 | { |
2235 | unsigned long present_pages = 0; |
2236 | int i; |
2237 | |
2238 | for (i = 0; i <= classzone_idx; i++) |
2239 | present_pages += pgdat->node_zones[i].present_pages; |
2240 | |
2241 | return balanced_pages > (present_pages >> 2); |
2242 | } |
2243 | |
2244 | /* is kswapd sleeping prematurely? */ |
2245 | static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, |
2246 | int classzone_idx) |
2247 | { |
2248 | int i; |
2249 | unsigned long balanced = 0; |
2250 | bool all_zones_ok = true; |
2251 | |
2252 | /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ |
2253 | if (remaining) |
2254 | return true; |
2255 | |
2256 | /* Check the watermark levels */ |
2257 | for (i = 0; i < pgdat->nr_zones; i++) { |
2258 | struct zone *zone = pgdat->node_zones + i; |
2259 | |
2260 | if (!populated_zone(zone)) |
2261 | continue; |
2262 | |
2263 | /* |
2264 | * balance_pgdat() skips over all_unreclaimable after |
2265 | * DEF_PRIORITY. Effectively, it considers them balanced so |
2266 | * they must be considered balanced here as well if kswapd |
2267 | * is to sleep |
2268 | */ |
2269 | if (zone->all_unreclaimable) { |
2270 | balanced += zone->present_pages; |
2271 | continue; |
2272 | } |
2273 | |
2274 | if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), |
2275 | classzone_idx, 0)) |
2276 | all_zones_ok = false; |
2277 | else |
2278 | balanced += zone->present_pages; |
2279 | } |
2280 | |
2281 | /* |
2282 | * For high-order requests, the balanced zones must contain at least |
2283 | * 25% of the nodes pages for kswapd to sleep. For order-0, all zones |
2284 | * must be balanced |
2285 | */ |
2286 | if (order) |
2287 | return pgdat_balanced(pgdat, balanced, classzone_idx); |
2288 | else |
2289 | return !all_zones_ok; |
2290 | } |
2291 | |
2292 | /* |
2293 | * For kswapd, balance_pgdat() will work across all this node's zones until |
2294 | * they are all at high_wmark_pages(zone). |
2295 | * |
2296 | * Returns the final order kswapd was reclaiming at |
2297 | * |
2298 | * There is special handling here for zones which are full of pinned pages. |
2299 | * This can happen if the pages are all mlocked, or if they are all used by |
2300 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. |
2301 | * What we do is to detect the case where all pages in the zone have been |
2302 | * scanned twice and there has been zero successful reclaim. Mark the zone as |
2303 | * dead and from now on, only perform a short scan. Basically we're polling |
2304 | * the zone for when the problem goes away. |
2305 | * |
2306 | * kswapd scans the zones in the highmem->normal->dma direction. It skips |
2307 | * zones which have free_pages > high_wmark_pages(zone), but once a zone is |
2308 | * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the |
2309 | * lower zones regardless of the number of free pages in the lower zones. This |
2310 | * interoperates with the page allocator fallback scheme to ensure that aging |
2311 | * of pages is balanced across the zones. |
2312 | */ |
2313 | static unsigned long balance_pgdat(pg_data_t *pgdat, int order, |
2314 | int *classzone_idx) |
2315 | { |
2316 | int all_zones_ok; |
2317 | unsigned long balanced; |
2318 | int priority; |
2319 | int i; |
2320 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ |
2321 | unsigned long total_scanned; |
2322 | struct reclaim_state *reclaim_state = current->reclaim_state; |
2323 | struct scan_control sc = { |
2324 | .gfp_mask = GFP_KERNEL, |
2325 | .may_unmap = 1, |
2326 | .may_swap = 1, |
2327 | /* |
2328 | * kswapd doesn't want to be bailed out while reclaim. because |
2329 | * we want to put equal scanning pressure on each zone. |
2330 | */ |
2331 | .nr_to_reclaim = ULONG_MAX, |
2332 | .swappiness = vm_swappiness, |
2333 | .order = order, |
2334 | .mem_cgroup = NULL, |
2335 | }; |
2336 | loop_again: |
2337 | total_scanned = 0; |
2338 | sc.nr_reclaimed = 0; |
2339 | sc.may_writepage = !laptop_mode; |
2340 | count_vm_event(PAGEOUTRUN); |
2341 | |
2342 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
2343 | unsigned long lru_pages = 0; |
2344 | int has_under_min_watermark_zone = 0; |
2345 | |
2346 | /* The swap token gets in the way of swapout... */ |
2347 | if (!priority) |
2348 | disable_swap_token(); |
2349 | |
2350 | all_zones_ok = 1; |
2351 | balanced = 0; |
2352 | |
2353 | /* |
2354 | * Scan in the highmem->dma direction for the highest |
2355 | * zone which needs scanning |
2356 | */ |
2357 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { |
2358 | struct zone *zone = pgdat->node_zones + i; |
2359 | |
2360 | if (!populated_zone(zone)) |
2361 | continue; |
2362 | |
2363 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
2364 | continue; |
2365 | |
2366 | /* |
2367 | * Do some background aging of the anon list, to give |
2368 | * pages a chance to be referenced before reclaiming. |
2369 | */ |
2370 | if (inactive_anon_is_low(zone, &sc)) |
2371 | shrink_active_list(SWAP_CLUSTER_MAX, zone, |
2372 | &sc, priority, 0); |
2373 | |
2374 | if (!zone_watermark_ok_safe(zone, order, |
2375 | high_wmark_pages(zone), 0, 0)) { |
2376 | end_zone = i; |
2377 | *classzone_idx = i; |
2378 | break; |
2379 | } |
2380 | } |
2381 | if (i < 0) |
2382 | goto out; |
2383 | |
2384 | for (i = 0; i <= end_zone; i++) { |
2385 | struct zone *zone = pgdat->node_zones + i; |
2386 | |
2387 | lru_pages += zone_reclaimable_pages(zone); |
2388 | } |
2389 | |
2390 | /* |
2391 | * Now scan the zone in the dma->highmem direction, stopping |
2392 | * at the last zone which needs scanning. |
2393 | * |
2394 | * We do this because the page allocator works in the opposite |
2395 | * direction. This prevents the page allocator from allocating |
2396 | * pages behind kswapd's direction of progress, which would |
2397 | * cause too much scanning of the lower zones. |
2398 | */ |
2399 | for (i = 0; i <= end_zone; i++) { |
2400 | int compaction; |
2401 | struct zone *zone = pgdat->node_zones + i; |
2402 | int nr_slab; |
2403 | |
2404 | if (!populated_zone(zone)) |
2405 | continue; |
2406 | |
2407 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
2408 | continue; |
2409 | |
2410 | sc.nr_scanned = 0; |
2411 | |
2412 | /* |
2413 | * Call soft limit reclaim before calling shrink_zone. |
2414 | * For now we ignore the return value |
2415 | */ |
2416 | mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask); |
2417 | |
2418 | /* |
2419 | * We put equal pressure on every zone, unless one |
2420 | * zone has way too many pages free already. |
2421 | */ |
2422 | if (!zone_watermark_ok_safe(zone, order, |
2423 | 8*high_wmark_pages(zone), end_zone, 0)) |
2424 | shrink_zone(priority, zone, &sc); |
2425 | reclaim_state->reclaimed_slab = 0; |
2426 | nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, |
2427 | lru_pages); |
2428 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; |
2429 | total_scanned += sc.nr_scanned; |
2430 | |
2431 | compaction = 0; |
2432 | if (order && |
2433 | zone_watermark_ok(zone, 0, |
2434 | high_wmark_pages(zone), |
2435 | end_zone, 0) && |
2436 | !zone_watermark_ok(zone, order, |
2437 | high_wmark_pages(zone), |
2438 | end_zone, 0)) { |
2439 | compact_zone_order(zone, |
2440 | order, |
2441 | sc.gfp_mask, false, |
2442 | COMPACT_MODE_KSWAPD); |
2443 | compaction = 1; |
2444 | } |
2445 | |
2446 | if (zone->all_unreclaimable) |
2447 | continue; |
2448 | if (!compaction && nr_slab == 0 && |
2449 | !zone_reclaimable(zone)) |
2450 | zone->all_unreclaimable = 1; |
2451 | /* |
2452 | * If we've done a decent amount of scanning and |
2453 | * the reclaim ratio is low, start doing writepage |
2454 | * even in laptop mode |
2455 | */ |
2456 | if (total_scanned > SWAP_CLUSTER_MAX * 2 && |
2457 | total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) |
2458 | sc.may_writepage = 1; |
2459 | |
2460 | if (!zone_watermark_ok_safe(zone, order, |
2461 | high_wmark_pages(zone), end_zone, 0)) { |
2462 | all_zones_ok = 0; |
2463 | /* |
2464 | * We are still under min water mark. This |
2465 | * means that we have a GFP_ATOMIC allocation |
2466 | * failure risk. Hurry up! |
2467 | */ |
2468 | if (!zone_watermark_ok_safe(zone, order, |
2469 | min_wmark_pages(zone), end_zone, 0)) |
2470 | has_under_min_watermark_zone = 1; |
2471 | } else { |
2472 | /* |
2473 | * If a zone reaches its high watermark, |
2474 | * consider it to be no longer congested. It's |
2475 | * possible there are dirty pages backed by |
2476 | * congested BDIs but as pressure is relieved, |
2477 | * spectulatively avoid congestion waits |
2478 | */ |
2479 | zone_clear_flag(zone, ZONE_CONGESTED); |
2480 | if (i <= *classzone_idx) |
2481 | balanced += zone->present_pages; |
2482 | } |
2483 | |
2484 | } |
2485 | if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) |
2486 | break; /* kswapd: all done */ |
2487 | /* |
2488 | * OK, kswapd is getting into trouble. Take a nap, then take |
2489 | * another pass across the zones. |
2490 | */ |
2491 | if (total_scanned && (priority < DEF_PRIORITY - 2)) { |
2492 | if (has_under_min_watermark_zone) |
2493 | count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); |
2494 | else |
2495 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
2496 | } |
2497 | |
2498 | /* |
2499 | * We do this so kswapd doesn't build up large priorities for |
2500 | * example when it is freeing in parallel with allocators. It |
2501 | * matches the direct reclaim path behaviour in terms of impact |
2502 | * on zone->*_priority. |
2503 | */ |
2504 | if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) |
2505 | break; |
2506 | } |
2507 | out: |
2508 | |
2509 | /* |
2510 | * order-0: All zones must meet high watermark for a balanced node |
2511 | * high-order: Balanced zones must make up at least 25% of the node |
2512 | * for the node to be balanced |
2513 | */ |
2514 | if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { |
2515 | cond_resched(); |
2516 | |
2517 | try_to_freeze(); |
2518 | |
2519 | /* |
2520 | * Fragmentation may mean that the system cannot be |
2521 | * rebalanced for high-order allocations in all zones. |
2522 | * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, |
2523 | * it means the zones have been fully scanned and are still |
2524 | * not balanced. For high-order allocations, there is |
2525 | * little point trying all over again as kswapd may |
2526 | * infinite loop. |
2527 | * |
2528 | * Instead, recheck all watermarks at order-0 as they |
2529 | * are the most important. If watermarks are ok, kswapd will go |
2530 | * back to sleep. High-order users can still perform direct |
2531 | * reclaim if they wish. |
2532 | */ |
2533 | if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) |
2534 | order = sc.order = 0; |
2535 | |
2536 | goto loop_again; |
2537 | } |
2538 | |
2539 | /* |
2540 | * If kswapd was reclaiming at a higher order, it has the option of |
2541 | * sleeping without all zones being balanced. Before it does, it must |
2542 | * ensure that the watermarks for order-0 on *all* zones are met and |
2543 | * that the congestion flags are cleared. The congestion flag must |
2544 | * be cleared as kswapd is the only mechanism that clears the flag |
2545 | * and it is potentially going to sleep here. |
2546 | */ |
2547 | if (order) { |
2548 | for (i = 0; i <= end_zone; i++) { |
2549 | struct zone *zone = pgdat->node_zones + i; |
2550 | |
2551 | if (!populated_zone(zone)) |
2552 | continue; |
2553 | |
2554 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
2555 | continue; |
2556 | |
2557 | /* Confirm the zone is balanced for order-0 */ |
2558 | if (!zone_watermark_ok(zone, 0, |
2559 | high_wmark_pages(zone), 0, 0)) { |
2560 | order = sc.order = 0; |
2561 | goto loop_again; |
2562 | } |
2563 | |
2564 | /* If balanced, clear the congested flag */ |
2565 | zone_clear_flag(zone, ZONE_CONGESTED); |
2566 | } |
2567 | } |
2568 | |
2569 | /* |
2570 | * Return the order we were reclaiming at so sleeping_prematurely() |
2571 | * makes a decision on the order we were last reclaiming at. However, |
2572 | * if another caller entered the allocator slow path while kswapd |
2573 | * was awake, order will remain at the higher level |
2574 | */ |
2575 | *classzone_idx = end_zone; |
2576 | return order; |
2577 | } |
2578 | |
2579 | static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) |
2580 | { |
2581 | long remaining = 0; |
2582 | DEFINE_WAIT(wait); |
2583 | |
2584 | if (freezing(current) || kthread_should_stop()) |
2585 | return; |
2586 | |
2587 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
2588 | |
2589 | /* Try to sleep for a short interval */ |
2590 | if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { |
2591 | remaining = schedule_timeout(HZ/10); |
2592 | finish_wait(&pgdat->kswapd_wait, &wait); |
2593 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
2594 | } |
2595 | |
2596 | /* |
2597 | * After a short sleep, check if it was a premature sleep. If not, then |
2598 | * go fully to sleep until explicitly woken up. |
2599 | */ |
2600 | if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { |
2601 | trace_mm_vmscan_kswapd_sleep(pgdat->node_id); |
2602 | |
2603 | /* |
2604 | * vmstat counters are not perfectly accurate and the estimated |
2605 | * value for counters such as NR_FREE_PAGES can deviate from the |
2606 | * true value by nr_online_cpus * threshold. To avoid the zone |
2607 | * watermarks being breached while under pressure, we reduce the |
2608 | * per-cpu vmstat threshold while kswapd is awake and restore |
2609 | * them before going back to sleep. |
2610 | */ |
2611 | set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); |
2612 | schedule(); |
2613 | set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); |
2614 | } else { |
2615 | if (remaining) |
2616 | count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); |
2617 | else |
2618 | count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); |
2619 | } |
2620 | finish_wait(&pgdat->kswapd_wait, &wait); |
2621 | } |
2622 | |
2623 | /* |
2624 | * The background pageout daemon, started as a kernel thread |
2625 | * from the init process. |
2626 | * |
2627 | * This basically trickles out pages so that we have _some_ |
2628 | * free memory available even if there is no other activity |
2629 | * that frees anything up. This is needed for things like routing |
2630 | * etc, where we otherwise might have all activity going on in |
2631 | * asynchronous contexts that cannot page things out. |
2632 | * |
2633 | * If there are applications that are active memory-allocators |
2634 | * (most normal use), this basically shouldn't matter. |
2635 | */ |
2636 | static int kswapd(void *p) |
2637 | { |
2638 | unsigned long order; |
2639 | int classzone_idx; |
2640 | pg_data_t *pgdat = (pg_data_t*)p; |
2641 | struct task_struct *tsk = current; |
2642 | |
2643 | struct reclaim_state reclaim_state = { |
2644 | .reclaimed_slab = 0, |
2645 | }; |
2646 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); |
2647 | |
2648 | lockdep_set_current_reclaim_state(GFP_KERNEL); |
2649 | |
2650 | if (!cpumask_empty(cpumask)) |
2651 | set_cpus_allowed_ptr(tsk, cpumask); |
2652 | current->reclaim_state = &reclaim_state; |
2653 | |
2654 | /* |
2655 | * Tell the memory management that we're a "memory allocator", |
2656 | * and that if we need more memory we should get access to it |
2657 | * regardless (see "__alloc_pages()"). "kswapd" should |
2658 | * never get caught in the normal page freeing logic. |
2659 | * |
2660 | * (Kswapd normally doesn't need memory anyway, but sometimes |
2661 | * you need a small amount of memory in order to be able to |
2662 | * page out something else, and this flag essentially protects |
2663 | * us from recursively trying to free more memory as we're |
2664 | * trying to free the first piece of memory in the first place). |
2665 | */ |
2666 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; |
2667 | set_freezable(); |
2668 | |
2669 | order = 0; |
2670 | classzone_idx = MAX_NR_ZONES - 1; |
2671 | for ( ; ; ) { |
2672 | unsigned long new_order; |
2673 | int new_classzone_idx; |
2674 | int ret; |
2675 | |
2676 | new_order = pgdat->kswapd_max_order; |
2677 | new_classzone_idx = pgdat->classzone_idx; |
2678 | pgdat->kswapd_max_order = 0; |
2679 | pgdat->classzone_idx = MAX_NR_ZONES - 1; |
2680 | if (order < new_order || classzone_idx > new_classzone_idx) { |
2681 | /* |
2682 | * Don't sleep if someone wants a larger 'order' |
2683 | * allocation or has tigher zone constraints |
2684 | */ |
2685 | order = new_order; |
2686 | classzone_idx = new_classzone_idx; |
2687 | } else { |
2688 | kswapd_try_to_sleep(pgdat, order, classzone_idx); |
2689 | order = pgdat->kswapd_max_order; |
2690 | classzone_idx = pgdat->classzone_idx; |
2691 | pgdat->kswapd_max_order = 0; |
2692 | pgdat->classzone_idx = MAX_NR_ZONES - 1; |
2693 | } |
2694 | |
2695 | ret = try_to_freeze(); |
2696 | if (kthread_should_stop()) |
2697 | break; |
2698 | |
2699 | /* |
2700 | * We can speed up thawing tasks if we don't call balance_pgdat |
2701 | * after returning from the refrigerator |
2702 | */ |
2703 | if (!ret) { |
2704 | trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); |
2705 | order = balance_pgdat(pgdat, order, &classzone_idx); |
2706 | } |
2707 | } |
2708 | return 0; |
2709 | } |
2710 | |
2711 | /* |
2712 | * A zone is low on free memory, so wake its kswapd task to service it. |
2713 | */ |
2714 | void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) |
2715 | { |
2716 | pg_data_t *pgdat; |
2717 | |
2718 | if (!populated_zone(zone)) |
2719 | return; |
2720 | |
2721 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2722 | return; |
2723 | pgdat = zone->zone_pgdat; |
2724 | if (pgdat->kswapd_max_order < order) { |
2725 | pgdat->kswapd_max_order = order; |
2726 | pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); |
2727 | } |
2728 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
2729 | return; |
2730 | if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) |
2731 | return; |
2732 | |
2733 | trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); |
2734 | wake_up_interruptible(&pgdat->kswapd_wait); |
2735 | } |
2736 | |
2737 | /* |
2738 | * The reclaimable count would be mostly accurate. |
2739 | * The less reclaimable pages may be |
2740 | * - mlocked pages, which will be moved to unevictable list when encountered |
2741 | * - mapped pages, which may require several travels to be reclaimed |
2742 | * - dirty pages, which is not "instantly" reclaimable |
2743 | */ |
2744 | unsigned long global_reclaimable_pages(void) |
2745 | { |
2746 | int nr; |
2747 | |
2748 | nr = global_page_state(NR_ACTIVE_FILE) + |
2749 | global_page_state(NR_INACTIVE_FILE); |
2750 | |
2751 | if (nr_swap_pages > 0) |
2752 | nr += global_page_state(NR_ACTIVE_ANON) + |
2753 | global_page_state(NR_INACTIVE_ANON); |
2754 | |
2755 | return nr; |
2756 | } |
2757 | |
2758 | unsigned long zone_reclaimable_pages(struct zone *zone) |
2759 | { |
2760 | int nr; |
2761 | |
2762 | nr = zone_page_state(zone, NR_ACTIVE_FILE) + |
2763 | zone_page_state(zone, NR_INACTIVE_FILE); |
2764 | |
2765 | if (nr_swap_pages > 0) |
2766 | nr += zone_page_state(zone, NR_ACTIVE_ANON) + |
2767 | zone_page_state(zone, NR_INACTIVE_ANON); |
2768 | |
2769 | return nr; |
2770 | } |
2771 | |
2772 | #ifdef CONFIG_HIBERNATION |
2773 | /* |
2774 | * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of |
2775 | * freed pages. |
2776 | * |
2777 | * Rather than trying to age LRUs the aim is to preserve the overall |
2778 | * LRU order by reclaiming preferentially |
2779 | * inactive > active > active referenced > active mapped |
2780 | */ |
2781 | unsigned long shrink_all_memory(unsigned long nr_to_reclaim) |
2782 | { |
2783 | struct reclaim_state reclaim_state; |
2784 | struct scan_control sc = { |
2785 | .gfp_mask = GFP_HIGHUSER_MOVABLE, |
2786 | .may_swap = 1, |
2787 | .may_unmap = 1, |
2788 | .may_writepage = 1, |
2789 | .nr_to_reclaim = nr_to_reclaim, |
2790 | .hibernation_mode = 1, |
2791 | .swappiness = vm_swappiness, |
2792 | .order = 0, |
2793 | }; |
2794 | struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); |
2795 | struct task_struct *p = current; |
2796 | unsigned long nr_reclaimed; |
2797 | |
2798 | p->flags |= PF_MEMALLOC; |
2799 | lockdep_set_current_reclaim_state(sc.gfp_mask); |
2800 | reclaim_state.reclaimed_slab = 0; |
2801 | p->reclaim_state = &reclaim_state; |
2802 | |
2803 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc); |
2804 | |
2805 | p->reclaim_state = NULL; |
2806 | lockdep_clear_current_reclaim_state(); |
2807 | p->flags &= ~PF_MEMALLOC; |
2808 | |
2809 | return nr_reclaimed; |
2810 | } |
2811 | #endif /* CONFIG_HIBERNATION */ |
2812 | |
2813 | /* It's optimal to keep kswapds on the same CPUs as their memory, but |
2814 | not required for correctness. So if the last cpu in a node goes |
2815 | away, we get changed to run anywhere: as the first one comes back, |
2816 | restore their cpu bindings. */ |
2817 | static int __devinit cpu_callback(struct notifier_block *nfb, |
2818 | unsigned long action, void *hcpu) |
2819 | { |
2820 | int nid; |
2821 | |
2822 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { |
2823 | for_each_node_state(nid, N_HIGH_MEMORY) { |
2824 | pg_data_t *pgdat = NODE_DATA(nid); |
2825 | const struct cpumask *mask; |
2826 | |
2827 | mask = cpumask_of_node(pgdat->node_id); |
2828 | |
2829 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
2830 | /* One of our CPUs online: restore mask */ |
2831 | set_cpus_allowed_ptr(pgdat->kswapd, mask); |
2832 | } |
2833 | } |
2834 | return NOTIFY_OK; |
2835 | } |
2836 | |
2837 | /* |
2838 | * This kswapd start function will be called by init and node-hot-add. |
2839 | * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. |
2840 | */ |
2841 | int kswapd_run(int nid) |
2842 | { |
2843 | pg_data_t *pgdat = NODE_DATA(nid); |
2844 | int ret = 0; |
2845 | |
2846 | if (pgdat->kswapd) |
2847 | return 0; |
2848 | |
2849 | pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); |
2850 | if (IS_ERR(pgdat->kswapd)) { |
2851 | /* failure at boot is fatal */ |
2852 | BUG_ON(system_state == SYSTEM_BOOTING); |
2853 | printk("Failed to start kswapd on node %d\n",nid); |
2854 | ret = -1; |
2855 | } |
2856 | return ret; |
2857 | } |
2858 | |
2859 | /* |
2860 | * Called by memory hotplug when all memory in a node is offlined. |
2861 | */ |
2862 | void kswapd_stop(int nid) |
2863 | { |
2864 | struct task_struct *kswapd = NODE_DATA(nid)->kswapd; |
2865 | |
2866 | if (kswapd) |
2867 | kthread_stop(kswapd); |
2868 | } |
2869 | |
2870 | static int __init kswapd_init(void) |
2871 | { |
2872 | int nid; |
2873 | |
2874 | swap_setup(); |
2875 | for_each_node_state(nid, N_HIGH_MEMORY) |
2876 | kswapd_run(nid); |
2877 | hotcpu_notifier(cpu_callback, 0); |
2878 | return 0; |
2879 | } |
2880 | |
2881 | module_init(kswapd_init) |
2882 | |
2883 | #ifdef CONFIG_NUMA |
2884 | /* |
2885 | * Zone reclaim mode |
2886 | * |
2887 | * If non-zero call zone_reclaim when the number of free pages falls below |
2888 | * the watermarks. |
2889 | */ |
2890 | int zone_reclaim_mode __read_mostly; |
2891 | |
2892 | #define RECLAIM_OFF 0 |
2893 | #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ |
2894 | #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ |
2895 | #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ |
2896 | |
2897 | /* |
2898 | * Priority for ZONE_RECLAIM. This determines the fraction of pages |
2899 | * of a node considered for each zone_reclaim. 4 scans 1/16th of |
2900 | * a zone. |
2901 | */ |
2902 | #define ZONE_RECLAIM_PRIORITY 4 |
2903 | |
2904 | /* |
2905 | * Percentage of pages in a zone that must be unmapped for zone_reclaim to |
2906 | * occur. |
2907 | */ |
2908 | int sysctl_min_unmapped_ratio = 1; |
2909 | |
2910 | /* |
2911 | * If the number of slab pages in a zone grows beyond this percentage then |
2912 | * slab reclaim needs to occur. |
2913 | */ |
2914 | int sysctl_min_slab_ratio = 5; |
2915 | |
2916 | static inline unsigned long zone_unmapped_file_pages(struct zone *zone) |
2917 | { |
2918 | unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); |
2919 | unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + |
2920 | zone_page_state(zone, NR_ACTIVE_FILE); |
2921 | |
2922 | /* |
2923 | * It's possible for there to be more file mapped pages than |
2924 | * accounted for by the pages on the file LRU lists because |
2925 | * tmpfs pages accounted for as ANON can also be FILE_MAPPED |
2926 | */ |
2927 | return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; |
2928 | } |
2929 | |
2930 | /* Work out how many page cache pages we can reclaim in this reclaim_mode */ |
2931 | static long zone_pagecache_reclaimable(struct zone *zone) |
2932 | { |
2933 | long nr_pagecache_reclaimable; |
2934 | long delta = 0; |
2935 | |
2936 | /* |
2937 | * If RECLAIM_SWAP is set, then all file pages are considered |
2938 | * potentially reclaimable. Otherwise, we have to worry about |
2939 | * pages like swapcache and zone_unmapped_file_pages() provides |
2940 | * a better estimate |
2941 | */ |
2942 | if (zone_reclaim_mode & RECLAIM_SWAP) |
2943 | nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); |
2944 | else |
2945 | nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); |
2946 | |
2947 | /* If we can't clean pages, remove dirty pages from consideration */ |
2948 | if (!(zone_reclaim_mode & RECLAIM_WRITE)) |
2949 | delta += zone_page_state(zone, NR_FILE_DIRTY); |
2950 | |
2951 | /* Watch for any possible underflows due to delta */ |
2952 | if (unlikely(delta > nr_pagecache_reclaimable)) |
2953 | delta = nr_pagecache_reclaimable; |
2954 | |
2955 | return nr_pagecache_reclaimable - delta; |
2956 | } |
2957 | |
2958 | /* |
2959 | * Try to free up some pages from this zone through reclaim. |
2960 | */ |
2961 | static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
2962 | { |
2963 | /* Minimum pages needed in order to stay on node */ |
2964 | const unsigned long nr_pages = 1 << order; |
2965 | struct task_struct *p = current; |
2966 | struct reclaim_state reclaim_state; |
2967 | int priority; |
2968 | struct scan_control sc = { |
2969 | .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), |
2970 | .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), |
2971 | .may_swap = 1, |
2972 | .nr_to_reclaim = max_t(unsigned long, nr_pages, |
2973 | SWAP_CLUSTER_MAX), |
2974 | .gfp_mask = gfp_mask, |
2975 | .swappiness = vm_swappiness, |
2976 | .order = order, |
2977 | }; |
2978 | unsigned long nr_slab_pages0, nr_slab_pages1; |
2979 | |
2980 | cond_resched(); |
2981 | /* |
2982 | * We need to be able to allocate from the reserves for RECLAIM_SWAP |
2983 | * and we also need to be able to write out pages for RECLAIM_WRITE |
2984 | * and RECLAIM_SWAP. |
2985 | */ |
2986 | p->flags |= PF_MEMALLOC | PF_SWAPWRITE; |
2987 | lockdep_set_current_reclaim_state(gfp_mask); |
2988 | reclaim_state.reclaimed_slab = 0; |
2989 | p->reclaim_state = &reclaim_state; |
2990 | |
2991 | if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { |
2992 | /* |
2993 | * Free memory by calling shrink zone with increasing |
2994 | * priorities until we have enough memory freed. |
2995 | */ |
2996 | priority = ZONE_RECLAIM_PRIORITY; |
2997 | do { |
2998 | shrink_zone(priority, zone, &sc); |
2999 | priority--; |
3000 | } while (priority >= 0 && sc.nr_reclaimed < nr_pages); |
3001 | } |
3002 | |
3003 | nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
3004 | if (nr_slab_pages0 > zone->min_slab_pages) { |
3005 | /* |
3006 | * shrink_slab() does not currently allow us to determine how |
3007 | * many pages were freed in this zone. So we take the current |
3008 | * number of slab pages and shake the slab until it is reduced |
3009 | * by the same nr_pages that we used for reclaiming unmapped |
3010 | * pages. |
3011 | * |
3012 | * Note that shrink_slab will free memory on all zones and may |
3013 | * take a long time. |
3014 | */ |
3015 | for (;;) { |
3016 | unsigned long lru_pages = zone_reclaimable_pages(zone); |
3017 | |
3018 | /* No reclaimable slab or very low memory pressure */ |
3019 | if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages)) |
3020 | break; |
3021 | |
3022 | /* Freed enough memory */ |
3023 | nr_slab_pages1 = zone_page_state(zone, |
3024 | NR_SLAB_RECLAIMABLE); |
3025 | if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) |
3026 | break; |
3027 | } |
3028 | |
3029 | /* |
3030 | * Update nr_reclaimed by the number of slab pages we |
3031 | * reclaimed from this zone. |
3032 | */ |
3033 | nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
3034 | if (nr_slab_pages1 < nr_slab_pages0) |
3035 | sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; |
3036 | } |
3037 | |
3038 | p->reclaim_state = NULL; |
3039 | current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); |
3040 | lockdep_clear_current_reclaim_state(); |
3041 | return sc.nr_reclaimed >= nr_pages; |
3042 | } |
3043 | |
3044 | int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
3045 | { |
3046 | int node_id; |
3047 | int ret; |
3048 | |
3049 | /* |
3050 | * Zone reclaim reclaims unmapped file backed pages and |
3051 | * slab pages if we are over the defined limits. |
3052 | * |
3053 | * A small portion of unmapped file backed pages is needed for |
3054 | * file I/O otherwise pages read by file I/O will be immediately |
3055 | * thrown out if the zone is overallocated. So we do not reclaim |
3056 | * if less than a specified percentage of the zone is used by |
3057 | * unmapped file backed pages. |
3058 | */ |
3059 | if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && |
3060 | zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) |
3061 | return ZONE_RECLAIM_FULL; |
3062 | |
3063 | if (zone->all_unreclaimable) |
3064 | return ZONE_RECLAIM_FULL; |
3065 | |
3066 | /* |
3067 | * Do not scan if the allocation should not be delayed. |
3068 | */ |
3069 | if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) |
3070 | return ZONE_RECLAIM_NOSCAN; |
3071 | |
3072 | /* |
3073 | * Only run zone reclaim on the local zone or on zones that do not |
3074 | * have associated processors. This will favor the local processor |
3075 | * over remote processors and spread off node memory allocations |
3076 | * as wide as possible. |
3077 | */ |
3078 | node_id = zone_to_nid(zone); |
3079 | if (node_state(node_id, N_CPU) && node_id != numa_node_id()) |
3080 | return ZONE_RECLAIM_NOSCAN; |
3081 | |
3082 | if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) |
3083 | return ZONE_RECLAIM_NOSCAN; |
3084 | |
3085 | ret = __zone_reclaim(zone, gfp_mask, order); |
3086 | zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); |
3087 | |
3088 | if (!ret) |
3089 | count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); |
3090 | |
3091 | return ret; |
3092 | } |
3093 | #endif |
3094 | |
3095 | /* |
3096 | * page_evictable - test whether a page is evictable |
3097 | * @page: the page to test |
3098 | * @vma: the VMA in which the page is or will be mapped, may be NULL |
3099 | * |
3100 | * Test whether page is evictable--i.e., should be placed on active/inactive |
3101 | * lists vs unevictable list. The vma argument is !NULL when called from the |
3102 | * fault path to determine how to instantate a new page. |
3103 | * |
3104 | * Reasons page might not be evictable: |
3105 | * (1) page's mapping marked unevictable |
3106 | * (2) page is part of an mlocked VMA |
3107 | * |
3108 | */ |
3109 | int page_evictable(struct page *page, struct vm_area_struct *vma) |
3110 | { |
3111 | |
3112 | if (mapping_unevictable(page_mapping(page))) |
3113 | return 0; |
3114 | |
3115 | if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) |
3116 | return 0; |
3117 | |
3118 | return 1; |
3119 | } |
3120 | |
3121 | /** |
3122 | * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list |
3123 | * @page: page to check evictability and move to appropriate lru list |
3124 | * @zone: zone page is in |
3125 | * |
3126 | * Checks a page for evictability and moves the page to the appropriate |
3127 | * zone lru list. |
3128 | * |
3129 | * Restrictions: zone->lru_lock must be held, page must be on LRU and must |
3130 | * have PageUnevictable set. |
3131 | */ |
3132 | static void check_move_unevictable_page(struct page *page, struct zone *zone) |
3133 | { |
3134 | VM_BUG_ON(PageActive(page)); |
3135 | |
3136 | retry: |
3137 | ClearPageUnevictable(page); |
3138 | if (page_evictable(page, NULL)) { |
3139 | enum lru_list l = page_lru_base_type(page); |
3140 | |
3141 | __dec_zone_state(zone, NR_UNEVICTABLE); |
3142 | list_move(&page->lru, &zone->lru[l].list); |
3143 | mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); |
3144 | __inc_zone_state(zone, NR_INACTIVE_ANON + l); |
3145 | __count_vm_event(UNEVICTABLE_PGRESCUED); |
3146 | } else { |
3147 | /* |
3148 | * rotate unevictable list |
3149 | */ |
3150 | SetPageUnevictable(page); |
3151 | list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); |
3152 | mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); |
3153 | if (page_evictable(page, NULL)) |
3154 | goto retry; |
3155 | } |
3156 | } |
3157 | |
3158 | /** |
3159 | * scan_mapping_unevictable_pages - scan an address space for evictable pages |
3160 | * @mapping: struct address_space to scan for evictable pages |
3161 | * |
3162 | * Scan all pages in mapping. Check unevictable pages for |
3163 | * evictability and move them to the appropriate zone lru list. |
3164 | */ |
3165 | void scan_mapping_unevictable_pages(struct address_space *mapping) |
3166 | { |
3167 | pgoff_t next = 0; |
3168 | pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> |
3169 | PAGE_CACHE_SHIFT; |
3170 | struct zone *zone; |
3171 | struct pagevec pvec; |
3172 | |
3173 | if (mapping->nrpages == 0) |
3174 | return; |
3175 | |
3176 | pagevec_init(&pvec, 0); |
3177 | while (next < end && |
3178 | pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { |
3179 | int i; |
3180 | int pg_scanned = 0; |
3181 | |
3182 | zone = NULL; |
3183 | |
3184 | for (i = 0; i < pagevec_count(&pvec); i++) { |
3185 | struct page *page = pvec.pages[i]; |
3186 | pgoff_t page_index = page->index; |
3187 | struct zone *pagezone = page_zone(page); |
3188 | |
3189 | pg_scanned++; |
3190 | if (page_index > next) |
3191 | next = page_index; |
3192 | next++; |
3193 | |
3194 | if (pagezone != zone) { |
3195 | if (zone) |
3196 | spin_unlock_irq(&zone->lru_lock); |
3197 | zone = pagezone; |
3198 | spin_lock_irq(&zone->lru_lock); |
3199 | } |
3200 | |
3201 | if (PageLRU(page) && PageUnevictable(page)) |
3202 | check_move_unevictable_page(page, zone); |
3203 | } |
3204 | if (zone) |
3205 | spin_unlock_irq(&zone->lru_lock); |
3206 | pagevec_release(&pvec); |
3207 | |
3208 | count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); |
3209 | } |
3210 | |
3211 | } |
3212 | |
3213 | /** |
3214 | * scan_zone_unevictable_pages - check unevictable list for evictable pages |
3215 | * @zone - zone of which to scan the unevictable list |
3216 | * |
3217 | * Scan @zone's unevictable LRU lists to check for pages that have become |
3218 | * evictable. Move those that have to @zone's inactive list where they |
3219 | * become candidates for reclaim, unless shrink_inactive_zone() decides |
3220 | * to reactivate them. Pages that are still unevictable are rotated |
3221 | * back onto @zone's unevictable list. |
3222 | */ |
3223 | #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ |
3224 | static void scan_zone_unevictable_pages(struct zone *zone) |
3225 | { |
3226 | struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; |
3227 | unsigned long scan; |
3228 | unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); |
3229 | |
3230 | while (nr_to_scan > 0) { |
3231 | unsigned long batch_size = min(nr_to_scan, |
3232 | SCAN_UNEVICTABLE_BATCH_SIZE); |
3233 | |
3234 | spin_lock_irq(&zone->lru_lock); |
3235 | for (scan = 0; scan < batch_size; scan++) { |
3236 | struct page *page = lru_to_page(l_unevictable); |
3237 | |
3238 | if (!trylock_page(page)) |
3239 | continue; |
3240 | |
3241 | prefetchw_prev_lru_page(page, l_unevictable, flags); |
3242 | |
3243 | if (likely(PageLRU(page) && PageUnevictable(page))) |
3244 | check_move_unevictable_page(page, zone); |
3245 | |
3246 | unlock_page(page); |
3247 | } |
3248 | spin_unlock_irq(&zone->lru_lock); |
3249 | |
3250 | nr_to_scan -= batch_size; |
3251 | } |
3252 | } |
3253 | |
3254 | |
3255 | /** |
3256 | * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages |
3257 | * |
3258 | * A really big hammer: scan all zones' unevictable LRU lists to check for |
3259 | * pages that have become evictable. Move those back to the zones' |
3260 | * inactive list where they become candidates for reclaim. |
3261 | * This occurs when, e.g., we have unswappable pages on the unevictable lists, |
3262 | * and we add swap to the system. As such, it runs in the context of a task |
3263 | * that has possibly/probably made some previously unevictable pages |
3264 | * evictable. |
3265 | */ |
3266 | static void scan_all_zones_unevictable_pages(void) |
3267 | { |
3268 | struct zone *zone; |
3269 | |
3270 | for_each_zone(zone) { |
3271 | scan_zone_unevictable_pages(zone); |
3272 | } |
3273 | } |
3274 | |
3275 | /* |
3276 | * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of |
3277 | * all nodes' unevictable lists for evictable pages |
3278 | */ |
3279 | unsigned long scan_unevictable_pages; |
3280 | |
3281 | int scan_unevictable_handler(struct ctl_table *table, int write, |
3282 | void __user *buffer, |
3283 | size_t *length, loff_t *ppos) |
3284 | { |
3285 | proc_doulongvec_minmax(table, write, buffer, length, ppos); |
3286 | |
3287 | if (write && *(unsigned long *)table->data) |
3288 | scan_all_zones_unevictable_pages(); |
3289 | |
3290 | scan_unevictable_pages = 0; |
3291 | return 0; |
3292 | } |
3293 | |
3294 | #ifdef CONFIG_NUMA |
3295 | /* |
3296 | * per node 'scan_unevictable_pages' attribute. On demand re-scan of |
3297 | * a specified node's per zone unevictable lists for evictable pages. |
3298 | */ |
3299 | |
3300 | static ssize_t read_scan_unevictable_node(struct sys_device *dev, |
3301 | struct sysdev_attribute *attr, |
3302 | char *buf) |
3303 | { |
3304 | return sprintf(buf, "0\n"); /* always zero; should fit... */ |
3305 | } |
3306 | |
3307 | static ssize_t write_scan_unevictable_node(struct sys_device *dev, |
3308 | struct sysdev_attribute *attr, |
3309 | const char *buf, size_t count) |
3310 | { |
3311 | struct zone *node_zones = NODE_DATA(dev->id)->node_zones; |
3312 | struct zone *zone; |
3313 | unsigned long res; |
3314 | unsigned long req = strict_strtoul(buf, 10, &res); |
3315 | |
3316 | if (!req) |
3317 | return 1; /* zero is no-op */ |
3318 | |
3319 | for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { |
3320 | if (!populated_zone(zone)) |
3321 | continue; |
3322 | scan_zone_unevictable_pages(zone); |
3323 | } |
3324 | return 1; |
3325 | } |
3326 | |
3327 | |
3328 | static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, |
3329 | read_scan_unevictable_node, |
3330 | write_scan_unevictable_node); |
3331 | |
3332 | int scan_unevictable_register_node(struct node *node) |
3333 | { |
3334 | return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); |
3335 | } |
3336 | |
3337 | void scan_unevictable_unregister_node(struct node *node) |
3338 | { |
3339 | sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); |
3340 | } |
3341 | #endif |
3342 |
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