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Source at commit b05a5adf03613de371c77c3235f7d970d7cd0c71 created 13 years 1 month ago. By Lars-Peter Clausen, NAND: Optimize reading the eec data for the JZ4740 (evil hack) | |
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1 | /* |
2 | * linux/mm/vmscan.c |
3 | * |
4 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
5 | * |
6 | * Swap reorganised 29.12.95, Stephen Tweedie. |
7 | * kswapd added: 7.1.96 sct |
8 | * Removed kswapd_ctl limits, and swap out as many pages as needed |
9 | * to bring the system back to freepages.high: 2.4.97, Rik van Riel. |
10 | * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). |
11 | * Multiqueue VM started 5.8.00, Rik van Riel. |
12 | */ |
13 | |
14 | #include <linux/mm.h> |
15 | #include <linux/module.h> |
16 | #include <linux/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 | #include <linux/oom.h> |
45 | |
46 | #include <asm/tlbflush.h> |
47 | #include <asm/div64.h> |
48 | |
49 | #include <linux/swapops.h> |
50 | |
51 | #include "internal.h" |
52 | |
53 | #define CREATE_TRACE_POINTS |
54 | #include <trace/events/vmscan.h> |
55 | |
56 | /* |
57 | * reclaim_mode determines how the inactive list is shrunk |
58 | * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages |
59 | * RECLAIM_MODE_ASYNC: Do not block |
60 | * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback |
61 | * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference |
62 | * page from the LRU and reclaim all pages within a |
63 | * naturally aligned range |
64 | * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of |
65 | * order-0 pages and then compact the zone |
66 | */ |
67 | typedef unsigned __bitwise__ reclaim_mode_t; |
68 | #define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u) |
69 | #define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u) |
70 | #define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u) |
71 | #define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u) |
72 | #define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u) |
73 | |
74 | struct scan_control { |
75 | /* Incremented by the number of inactive pages that were scanned */ |
76 | unsigned long nr_scanned; |
77 | |
78 | /* Number of pages freed so far during a call to shrink_zones() */ |
79 | unsigned long nr_reclaimed; |
80 | |
81 | /* How many pages shrink_list() should reclaim */ |
82 | unsigned long nr_to_reclaim; |
83 | |
84 | unsigned long hibernation_mode; |
85 | |
86 | /* This context's GFP mask */ |
87 | gfp_t gfp_mask; |
88 | |
89 | int may_writepage; |
90 | |
91 | /* Can mapped pages be reclaimed? */ |
92 | int may_unmap; |
93 | |
94 | /* Can pages be swapped as part of reclaim? */ |
95 | int may_swap; |
96 | |
97 | int swappiness; |
98 | |
99 | int order; |
100 | |
101 | /* |
102 | * Intend to reclaim enough continuous memory rather than reclaim |
103 | * enough amount of memory. i.e, mode for high order allocation. |
104 | */ |
105 | reclaim_mode_t reclaim_mode; |
106 | |
107 | /* Which cgroup do we reclaim from */ |
108 | struct mem_cgroup *mem_cgroup; |
109 | |
110 | /* |
111 | * Nodemask of nodes allowed by the caller. If NULL, all nodes |
112 | * are scanned. |
113 | */ |
114 | nodemask_t *nodemask; |
115 | }; |
116 | |
117 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) |
118 | |
119 | #ifdef ARCH_HAS_PREFETCH |
120 | #define prefetch_prev_lru_page(_page, _base, _field) \ |
121 | do { \ |
122 | if ((_page)->lru.prev != _base) { \ |
123 | struct page *prev; \ |
124 | \ |
125 | prev = lru_to_page(&(_page->lru)); \ |
126 | prefetch(&prev->_field); \ |
127 | } \ |
128 | } while (0) |
129 | #else |
130 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) |
131 | #endif |
132 | |
133 | #ifdef ARCH_HAS_PREFETCHW |
134 | #define prefetchw_prev_lru_page(_page, _base, _field) \ |
135 | do { \ |
136 | if ((_page)->lru.prev != _base) { \ |
137 | struct page *prev; \ |
138 | \ |
139 | prev = lru_to_page(&(_page->lru)); \ |
140 | prefetchw(&prev->_field); \ |
141 | } \ |
142 | } while (0) |
143 | #else |
144 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) |
145 | #endif |
146 | |
147 | /* |
148 | * From 0 .. 100. Higher means more swappy. |
149 | */ |
150 | int vm_swappiness = 60; |
151 | long vm_total_pages; /* The total number of pages which the VM controls */ |
152 | |
153 | static LIST_HEAD(shrinker_list); |
154 | static DECLARE_RWSEM(shrinker_rwsem); |
155 | |
156 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
157 | #define scanning_global_lru(sc) (!(sc)->mem_cgroup) |
158 | #else |
159 | #define scanning_global_lru(sc) (1) |
160 | #endif |
161 | |
162 | static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, |
163 | struct scan_control *sc) |
164 | { |
165 | if (!scanning_global_lru(sc)) |
166 | return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); |
167 | |
168 | return &zone->reclaim_stat; |
169 | } |
170 | |
171 | static unsigned long zone_nr_lru_pages(struct zone *zone, |
172 | struct scan_control *sc, enum lru_list lru) |
173 | { |
174 | if (!scanning_global_lru(sc)) |
175 | return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru); |
176 | |
177 | return zone_page_state(zone, NR_LRU_BASE + lru); |
178 | } |
179 | |
180 | |
181 | /* |
182 | * Add a shrinker callback to be called from the vm |
183 | */ |
184 | void register_shrinker(struct shrinker *shrinker) |
185 | { |
186 | shrinker->nr = 0; |
187 | down_write(&shrinker_rwsem); |
188 | list_add_tail(&shrinker->list, &shrinker_list); |
189 | up_write(&shrinker_rwsem); |
190 | } |
191 | EXPORT_SYMBOL(register_shrinker); |
192 | |
193 | /* |
194 | * Remove one |
195 | */ |
196 | void unregister_shrinker(struct shrinker *shrinker) |
197 | { |
198 | down_write(&shrinker_rwsem); |
199 | list_del(&shrinker->list); |
200 | up_write(&shrinker_rwsem); |
201 | } |
202 | EXPORT_SYMBOL(unregister_shrinker); |
203 | |
204 | #define SHRINK_BATCH 128 |
205 | /* |
206 | * Call the shrink functions to age shrinkable caches |
207 | * |
208 | * Here we assume it costs one seek to replace a lru page and that it also |
209 | * takes a seek to recreate a cache object. With this in mind we age equal |
210 | * percentages of the lru and ageable caches. This should balance the seeks |
211 | * generated by these structures. |
212 | * |
213 | * If the vm encountered mapped pages on the LRU it increase the pressure on |
214 | * slab to avoid swapping. |
215 | * |
216 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. |
217 | * |
218 | * `lru_pages' represents the number of on-LRU pages in all the zones which |
219 | * are eligible for the caller's allocation attempt. It is used for balancing |
220 | * slab reclaim versus page reclaim. |
221 | * |
222 | * Returns the number of slab objects which we shrunk. |
223 | */ |
224 | unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, |
225 | unsigned long lru_pages) |
226 | { |
227 | struct shrinker *shrinker; |
228 | unsigned long ret = 0; |
229 | |
230 | if (scanned == 0) |
231 | scanned = SWAP_CLUSTER_MAX; |
232 | |
233 | if (!down_read_trylock(&shrinker_rwsem)) |
234 | return 1; /* Assume we'll be able to shrink next time */ |
235 | |
236 | list_for_each_entry(shrinker, &shrinker_list, list) { |
237 | unsigned long long delta; |
238 | unsigned long total_scan; |
239 | unsigned long max_pass; |
240 | |
241 | max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask); |
242 | delta = (4 * scanned) / shrinker->seeks; |
243 | delta *= max_pass; |
244 | do_div(delta, lru_pages + 1); |
245 | shrinker->nr += delta; |
246 | if (shrinker->nr < 0) { |
247 | printk(KERN_ERR "shrink_slab: %pF negative objects to " |
248 | "delete nr=%ld\n", |
249 | shrinker->shrink, shrinker->nr); |
250 | shrinker->nr = max_pass; |
251 | } |
252 | |
253 | /* |
254 | * Avoid risking looping forever due to too large nr value: |
255 | * never try to free more than twice the estimate number of |
256 | * freeable entries. |
257 | */ |
258 | if (shrinker->nr > max_pass * 2) |
259 | shrinker->nr = max_pass * 2; |
260 | |
261 | total_scan = shrinker->nr; |
262 | shrinker->nr = 0; |
263 | |
264 | while (total_scan >= SHRINK_BATCH) { |
265 | long this_scan = SHRINK_BATCH; |
266 | int shrink_ret; |
267 | int nr_before; |
268 | |
269 | nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask); |
270 | shrink_ret = (*shrinker->shrink)(shrinker, this_scan, |
271 | gfp_mask); |
272 | if (shrink_ret == -1) |
273 | break; |
274 | if (shrink_ret < nr_before) |
275 | ret += nr_before - shrink_ret; |
276 | count_vm_events(SLABS_SCANNED, this_scan); |
277 | total_scan -= this_scan; |
278 | |
279 | cond_resched(); |
280 | } |
281 | |
282 | shrinker->nr += total_scan; |
283 | } |
284 | up_read(&shrinker_rwsem); |
285 | return ret; |
286 | } |
287 | |
288 | static void set_reclaim_mode(int priority, struct scan_control *sc, |
289 | bool sync) |
290 | { |
291 | reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; |
292 | |
293 | /* |
294 | * Initially assume we are entering either lumpy reclaim or |
295 | * reclaim/compaction.Depending on the order, we will either set the |
296 | * sync mode or just reclaim order-0 pages later. |
297 | */ |
298 | if (COMPACTION_BUILD) |
299 | sc->reclaim_mode = RECLAIM_MODE_COMPACTION; |
300 | else |
301 | sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; |
302 | |
303 | /* |
304 | * Avoid using lumpy reclaim or reclaim/compaction if possible by |
305 | * restricting when its set to either costly allocations or when |
306 | * under memory pressure |
307 | */ |
308 | if (sc->order > PAGE_ALLOC_COSTLY_ORDER) |
309 | sc->reclaim_mode |= syncmode; |
310 | else if (sc->order && priority < DEF_PRIORITY - 2) |
311 | sc->reclaim_mode |= syncmode; |
312 | else |
313 | sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; |
314 | } |
315 | |
316 | static void reset_reclaim_mode(struct scan_control *sc) |
317 | { |
318 | sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; |
319 | } |
320 | |
321 | static inline int is_page_cache_freeable(struct page *page) |
322 | { |
323 | /* |
324 | * A freeable page cache page is referenced only by the caller |
325 | * that isolated the page, the page cache radix tree and |
326 | * optional buffer heads at page->private. |
327 | */ |
328 | return page_count(page) - page_has_private(page) == 2; |
329 | } |
330 | |
331 | static int may_write_to_queue(struct backing_dev_info *bdi, |
332 | struct scan_control *sc) |
333 | { |
334 | if (current->flags & PF_SWAPWRITE) |
335 | return 1; |
336 | if (!bdi_write_congested(bdi)) |
337 | return 1; |
338 | if (bdi == current->backing_dev_info) |
339 | return 1; |
340 | |
341 | /* lumpy reclaim for hugepage often need a lot of write */ |
342 | if (sc->order > PAGE_ALLOC_COSTLY_ORDER) |
343 | return 1; |
344 | return 0; |
345 | } |
346 | |
347 | /* |
348 | * We detected a synchronous write error writing a page out. Probably |
349 | * -ENOSPC. We need to propagate that into the address_space for a subsequent |
350 | * fsync(), msync() or close(). |
351 | * |
352 | * The tricky part is that after writepage we cannot touch the mapping: nothing |
353 | * prevents it from being freed up. But we have a ref on the page and once |
354 | * that page is locked, the mapping is pinned. |
355 | * |
356 | * We're allowed to run sleeping lock_page() here because we know the caller has |
357 | * __GFP_FS. |
358 | */ |
359 | static void handle_write_error(struct address_space *mapping, |
360 | struct page *page, int error) |
361 | { |
362 | lock_page(page); |
363 | if (page_mapping(page) == mapping) |
364 | mapping_set_error(mapping, error); |
365 | unlock_page(page); |
366 | } |
367 | |
368 | /* possible outcome of pageout() */ |
369 | typedef enum { |
370 | /* failed to write page out, page is locked */ |
371 | PAGE_KEEP, |
372 | /* move page to the active list, page is locked */ |
373 | PAGE_ACTIVATE, |
374 | /* page has been sent to the disk successfully, page is unlocked */ |
375 | PAGE_SUCCESS, |
376 | /* page is clean and locked */ |
377 | PAGE_CLEAN, |
378 | } pageout_t; |
379 | |
380 | /* |
381 | * pageout is called by shrink_page_list() for each dirty page. |
382 | * Calls ->writepage(). |
383 | */ |
384 | static pageout_t pageout(struct page *page, struct address_space *mapping, |
385 | struct scan_control *sc) |
386 | { |
387 | /* |
388 | * If the page is dirty, only perform writeback if that write |
389 | * will be non-blocking. To prevent this allocation from being |
390 | * stalled by pagecache activity. But note that there may be |
391 | * stalls if we need to run get_block(). We could test |
392 | * PagePrivate for that. |
393 | * |
394 | * If this process is currently in __generic_file_aio_write() against |
395 | * this page's queue, we can perform writeback even if that |
396 | * will block. |
397 | * |
398 | * If the page is swapcache, write it back even if that would |
399 | * block, for some throttling. This happens by accident, because |
400 | * swap_backing_dev_info is bust: it doesn't reflect the |
401 | * congestion state of the swapdevs. Easy to fix, if needed. |
402 | */ |
403 | if (!is_page_cache_freeable(page)) |
404 | return PAGE_KEEP; |
405 | if (!mapping) { |
406 | /* |
407 | * Some data journaling orphaned pages can have |
408 | * page->mapping == NULL while being dirty with clean buffers. |
409 | */ |
410 | if (page_has_private(page)) { |
411 | if (try_to_free_buffers(page)) { |
412 | ClearPageDirty(page); |
413 | printk("%s: orphaned page\n", __func__); |
414 | return PAGE_CLEAN; |
415 | } |
416 | } |
417 | return PAGE_KEEP; |
418 | } |
419 | if (mapping->a_ops->writepage == NULL) |
420 | return PAGE_ACTIVATE; |
421 | if (!may_write_to_queue(mapping->backing_dev_info, sc)) |
422 | return PAGE_KEEP; |
423 | |
424 | if (clear_page_dirty_for_io(page)) { |
425 | int res; |
426 | struct writeback_control wbc = { |
427 | .sync_mode = WB_SYNC_NONE, |
428 | .nr_to_write = SWAP_CLUSTER_MAX, |
429 | .range_start = 0, |
430 | .range_end = LLONG_MAX, |
431 | .for_reclaim = 1, |
432 | }; |
433 | |
434 | SetPageReclaim(page); |
435 | res = mapping->a_ops->writepage(page, &wbc); |
436 | if (res < 0) |
437 | handle_write_error(mapping, page, res); |
438 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
439 | ClearPageReclaim(page); |
440 | return PAGE_ACTIVATE; |
441 | } |
442 | |
443 | /* |
444 | * Wait on writeback if requested to. This happens when |
445 | * direct reclaiming a large contiguous area and the |
446 | * first attempt to free a range of pages fails. |
447 | */ |
448 | if (PageWriteback(page) && |
449 | (sc->reclaim_mode & RECLAIM_MODE_SYNC)) |
450 | wait_on_page_writeback(page); |
451 | |
452 | if (!PageWriteback(page)) { |
453 | /* synchronous write or broken a_ops? */ |
454 | ClearPageReclaim(page); |
455 | } |
456 | trace_mm_vmscan_writepage(page, |
457 | trace_reclaim_flags(page, sc->reclaim_mode)); |
458 | inc_zone_page_state(page, NR_VMSCAN_WRITE); |
459 | return PAGE_SUCCESS; |
460 | } |
461 | |
462 | return PAGE_CLEAN; |
463 | } |
464 | |
465 | /* |
466 | * Same as remove_mapping, but if the page is removed from the mapping, it |
467 | * gets returned with a refcount of 0. |
468 | */ |
469 | static int __remove_mapping(struct address_space *mapping, struct page *page) |
470 | { |
471 | BUG_ON(!PageLocked(page)); |
472 | BUG_ON(mapping != page_mapping(page)); |
473 | |
474 | spin_lock_irq(&mapping->tree_lock); |
475 | /* |
476 | * The non racy check for a busy page. |
477 | * |
478 | * Must be careful with the order of the tests. When someone has |
479 | * a ref to the page, it may be possible that they dirty it then |
480 | * drop the reference. So if PageDirty is tested before page_count |
481 | * here, then the following race may occur: |
482 | * |
483 | * get_user_pages(&page); |
484 | * [user mapping goes away] |
485 | * write_to(page); |
486 | * !PageDirty(page) [good] |
487 | * SetPageDirty(page); |
488 | * put_page(page); |
489 | * !page_count(page) [good, discard it] |
490 | * |
491 | * [oops, our write_to data is lost] |
492 | * |
493 | * Reversing the order of the tests ensures such a situation cannot |
494 | * escape unnoticed. The smp_rmb is needed to ensure the page->flags |
495 | * load is not satisfied before that of page->_count. |
496 | * |
497 | * Note that if SetPageDirty is always performed via set_page_dirty, |
498 | * and thus under tree_lock, then this ordering is not required. |
499 | */ |
500 | if (!page_freeze_refs(page, 2)) |
501 | goto cannot_free; |
502 | /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ |
503 | if (unlikely(PageDirty(page))) { |
504 | page_unfreeze_refs(page, 2); |
505 | goto cannot_free; |
506 | } |
507 | |
508 | if (PageSwapCache(page)) { |
509 | swp_entry_t swap = { .val = page_private(page) }; |
510 | __delete_from_swap_cache(page); |
511 | spin_unlock_irq(&mapping->tree_lock); |
512 | swapcache_free(swap, page); |
513 | } else { |
514 | void (*freepage)(struct page *); |
515 | |
516 | freepage = mapping->a_ops->freepage; |
517 | |
518 | __delete_from_page_cache(page); |
519 | spin_unlock_irq(&mapping->tree_lock); |
520 | mem_cgroup_uncharge_cache_page(page); |
521 | |
522 | if (freepage != NULL) |
523 | freepage(page); |
524 | } |
525 | |
526 | return 1; |
527 | |
528 | cannot_free: |
529 | spin_unlock_irq(&mapping->tree_lock); |
530 | return 0; |
531 | } |
532 | |
533 | /* |
534 | * Attempt to detach a locked page from its ->mapping. If it is dirty or if |
535 | * someone else has a ref on the page, abort and return 0. If it was |
536 | * successfully detached, return 1. Assumes the caller has a single ref on |
537 | * this page. |
538 | */ |
539 | int remove_mapping(struct address_space *mapping, struct page *page) |
540 | { |
541 | if (__remove_mapping(mapping, page)) { |
542 | /* |
543 | * Unfreezing the refcount with 1 rather than 2 effectively |
544 | * drops the pagecache ref for us without requiring another |
545 | * atomic operation. |
546 | */ |
547 | page_unfreeze_refs(page, 1); |
548 | return 1; |
549 | } |
550 | return 0; |
551 | } |
552 | |
553 | /** |
554 | * putback_lru_page - put previously isolated page onto appropriate LRU list |
555 | * @page: page to be put back to appropriate lru list |
556 | * |
557 | * Add previously isolated @page to appropriate LRU list. |
558 | * Page may still be unevictable for other reasons. |
559 | * |
560 | * lru_lock must not be held, interrupts must be enabled. |
561 | */ |
562 | void putback_lru_page(struct page *page) |
563 | { |
564 | int lru; |
565 | int active = !!TestClearPageActive(page); |
566 | int was_unevictable = PageUnevictable(page); |
567 | |
568 | VM_BUG_ON(PageLRU(page)); |
569 | |
570 | redo: |
571 | ClearPageUnevictable(page); |
572 | |
573 | if (page_evictable(page, NULL)) { |
574 | /* |
575 | * For evictable pages, we can use the cache. |
576 | * In event of a race, worst case is we end up with an |
577 | * unevictable page on [in]active list. |
578 | * We know how to handle that. |
579 | */ |
580 | lru = active + page_lru_base_type(page); |
581 | lru_cache_add_lru(page, lru); |
582 | } else { |
583 | /* |
584 | * Put unevictable pages directly on zone's unevictable |
585 | * list. |
586 | */ |
587 | lru = LRU_UNEVICTABLE; |
588 | add_page_to_unevictable_list(page); |
589 | /* |
590 | * When racing with an mlock clearing (page is |
591 | * unlocked), make sure that if the other thread does |
592 | * not observe our setting of PG_lru and fails |
593 | * isolation, we see PG_mlocked cleared below and move |
594 | * the page back to the evictable list. |
595 | * |
596 | * The other side is TestClearPageMlocked(). |
597 | */ |
598 | smp_mb(); |
599 | } |
600 | |
601 | /* |
602 | * page's status can change while we move it among lru. If an evictable |
603 | * page is on unevictable list, it never be freed. To avoid that, |
604 | * check after we added it to the list, again. |
605 | */ |
606 | if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { |
607 | if (!isolate_lru_page(page)) { |
608 | put_page(page); |
609 | goto redo; |
610 | } |
611 | /* This means someone else dropped this page from LRU |
612 | * So, it will be freed or putback to LRU again. There is |
613 | * nothing to do here. |
614 | */ |
615 | } |
616 | |
617 | if (was_unevictable && lru != LRU_UNEVICTABLE) |
618 | count_vm_event(UNEVICTABLE_PGRESCUED); |
619 | else if (!was_unevictable && lru == LRU_UNEVICTABLE) |
620 | count_vm_event(UNEVICTABLE_PGCULLED); |
621 | |
622 | put_page(page); /* drop ref from isolate */ |
623 | } |
624 | |
625 | enum page_references { |
626 | PAGEREF_RECLAIM, |
627 | PAGEREF_RECLAIM_CLEAN, |
628 | PAGEREF_KEEP, |
629 | PAGEREF_ACTIVATE, |
630 | }; |
631 | |
632 | static enum page_references page_check_references(struct page *page, |
633 | struct scan_control *sc) |
634 | { |
635 | int referenced_ptes, referenced_page; |
636 | unsigned long vm_flags; |
637 | |
638 | referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags); |
639 | referenced_page = TestClearPageReferenced(page); |
640 | |
641 | /* Lumpy reclaim - ignore references */ |
642 | if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) |
643 | return PAGEREF_RECLAIM; |
644 | |
645 | /* |
646 | * Mlock lost the isolation race with us. Let try_to_unmap() |
647 | * move the page to the unevictable list. |
648 | */ |
649 | if (vm_flags & VM_LOCKED) |
650 | return PAGEREF_RECLAIM; |
651 | |
652 | if (referenced_ptes) { |
653 | if (PageAnon(page)) |
654 | return PAGEREF_ACTIVATE; |
655 | /* |
656 | * All mapped pages start out with page table |
657 | * references from the instantiating fault, so we need |
658 | * to look twice if a mapped file page is used more |
659 | * than once. |
660 | * |
661 | * Mark it and spare it for another trip around the |
662 | * inactive list. Another page table reference will |
663 | * lead to its activation. |
664 | * |
665 | * Note: the mark is set for activated pages as well |
666 | * so that recently deactivated but used pages are |
667 | * quickly recovered. |
668 | */ |
669 | SetPageReferenced(page); |
670 | |
671 | if (referenced_page) |
672 | return PAGEREF_ACTIVATE; |
673 | |
674 | return PAGEREF_KEEP; |
675 | } |
676 | |
677 | /* Reclaim if clean, defer dirty pages to writeback */ |
678 | if (referenced_page && !PageSwapBacked(page)) |
679 | return PAGEREF_RECLAIM_CLEAN; |
680 | |
681 | return PAGEREF_RECLAIM; |
682 | } |
683 | |
684 | static noinline_for_stack void free_page_list(struct list_head *free_pages) |
685 | { |
686 | struct pagevec freed_pvec; |
687 | struct page *page, *tmp; |
688 | |
689 | pagevec_init(&freed_pvec, 1); |
690 | |
691 | list_for_each_entry_safe(page, tmp, free_pages, lru) { |
692 | list_del(&page->lru); |
693 | if (!pagevec_add(&freed_pvec, page)) { |
694 | __pagevec_free(&freed_pvec); |
695 | pagevec_reinit(&freed_pvec); |
696 | } |
697 | } |
698 | |
699 | pagevec_free(&freed_pvec); |
700 | } |
701 | |
702 | /* |
703 | * shrink_page_list() returns the number of reclaimed pages |
704 | */ |
705 | static unsigned long shrink_page_list(struct list_head *page_list, |
706 | struct zone *zone, |
707 | struct scan_control *sc) |
708 | { |
709 | LIST_HEAD(ret_pages); |
710 | LIST_HEAD(free_pages); |
711 | int pgactivate = 0; |
712 | unsigned long nr_dirty = 0; |
713 | unsigned long nr_congested = 0; |
714 | unsigned long nr_reclaimed = 0; |
715 | |
716 | cond_resched(); |
717 | |
718 | while (!list_empty(page_list)) { |
719 | enum page_references references; |
720 | struct address_space *mapping; |
721 | struct page *page; |
722 | int may_enter_fs; |
723 | |
724 | cond_resched(); |
725 | |
726 | page = lru_to_page(page_list); |
727 | list_del(&page->lru); |
728 | |
729 | if (!trylock_page(page)) |
730 | goto keep; |
731 | |
732 | VM_BUG_ON(PageActive(page)); |
733 | VM_BUG_ON(page_zone(page) != zone); |
734 | |
735 | sc->nr_scanned++; |
736 | |
737 | if (unlikely(!page_evictable(page, NULL))) |
738 | goto cull_mlocked; |
739 | |
740 | if (!sc->may_unmap && page_mapped(page)) |
741 | goto keep_locked; |
742 | |
743 | /* Double the slab pressure for mapped and swapcache pages */ |
744 | if (page_mapped(page) || PageSwapCache(page)) |
745 | sc->nr_scanned++; |
746 | |
747 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || |
748 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); |
749 | |
750 | if (PageWriteback(page)) { |
751 | /* |
752 | * Synchronous reclaim is performed in two passes, |
753 | * first an asynchronous pass over the list to |
754 | * start parallel writeback, and a second synchronous |
755 | * pass to wait for the IO to complete. Wait here |
756 | * for any page for which writeback has already |
757 | * started. |
758 | */ |
759 | if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && |
760 | may_enter_fs) |
761 | wait_on_page_writeback(page); |
762 | else { |
763 | unlock_page(page); |
764 | goto keep_lumpy; |
765 | } |
766 | } |
767 | |
768 | references = page_check_references(page, sc); |
769 | switch (references) { |
770 | case PAGEREF_ACTIVATE: |
771 | goto activate_locked; |
772 | case PAGEREF_KEEP: |
773 | goto keep_locked; |
774 | case PAGEREF_RECLAIM: |
775 | case PAGEREF_RECLAIM_CLEAN: |
776 | ; /* try to reclaim the page below */ |
777 | } |
778 | |
779 | /* |
780 | * Anonymous process memory has backing store? |
781 | * Try to allocate it some swap space here. |
782 | */ |
783 | if (PageAnon(page) && !PageSwapCache(page)) { |
784 | if (!(sc->gfp_mask & __GFP_IO)) |
785 | goto keep_locked; |
786 | if (!add_to_swap(page)) |
787 | goto activate_locked; |
788 | may_enter_fs = 1; |
789 | } |
790 | |
791 | mapping = page_mapping(page); |
792 | |
793 | /* |
794 | * The page is mapped into the page tables of one or more |
795 | * processes. Try to unmap it here. |
796 | */ |
797 | if (page_mapped(page) && mapping) { |
798 | switch (try_to_unmap(page, TTU_UNMAP)) { |
799 | case SWAP_FAIL: |
800 | goto activate_locked; |
801 | case SWAP_AGAIN: |
802 | goto keep_locked; |
803 | case SWAP_MLOCK: |
804 | goto cull_mlocked; |
805 | case SWAP_SUCCESS: |
806 | ; /* try to free the page below */ |
807 | } |
808 | } |
809 | |
810 | if (PageDirty(page)) { |
811 | nr_dirty++; |
812 | |
813 | if (references == PAGEREF_RECLAIM_CLEAN) |
814 | goto keep_locked; |
815 | if (!may_enter_fs) |
816 | goto keep_locked; |
817 | if (!sc->may_writepage) |
818 | goto keep_locked; |
819 | |
820 | /* Page is dirty, try to write it out here */ |
821 | switch (pageout(page, mapping, sc)) { |
822 | case PAGE_KEEP: |
823 | nr_congested++; |
824 | goto keep_locked; |
825 | case PAGE_ACTIVATE: |
826 | goto activate_locked; |
827 | case PAGE_SUCCESS: |
828 | if (PageWriteback(page)) |
829 | goto keep_lumpy; |
830 | if (PageDirty(page)) |
831 | goto keep; |
832 | |
833 | /* |
834 | * A synchronous write - probably a ramdisk. Go |
835 | * ahead and try to reclaim the page. |
836 | */ |
837 | if (!trylock_page(page)) |
838 | goto keep; |
839 | if (PageDirty(page) || PageWriteback(page)) |
840 | goto keep_locked; |
841 | mapping = page_mapping(page); |
842 | case PAGE_CLEAN: |
843 | ; /* try to free the page below */ |
844 | } |
845 | } |
846 | |
847 | /* |
848 | * If the page has buffers, try to free the buffer mappings |
849 | * associated with this page. If we succeed we try to free |
850 | * the page as well. |
851 | * |
852 | * We do this even if the page is PageDirty(). |
853 | * try_to_release_page() does not perform I/O, but it is |
854 | * possible for a page to have PageDirty set, but it is actually |
855 | * clean (all its buffers are clean). This happens if the |
856 | * buffers were written out directly, with submit_bh(). ext3 |
857 | * will do this, as well as the blockdev mapping. |
858 | * try_to_release_page() will discover that cleanness and will |
859 | * drop the buffers and mark the page clean - it can be freed. |
860 | * |
861 | * Rarely, pages can have buffers and no ->mapping. These are |
862 | * the pages which were not successfully invalidated in |
863 | * truncate_complete_page(). We try to drop those buffers here |
864 | * and if that worked, and the page is no longer mapped into |
865 | * process address space (page_count == 1) it can be freed. |
866 | * Otherwise, leave the page on the LRU so it is swappable. |
867 | */ |
868 | if (page_has_private(page)) { |
869 | if (!try_to_release_page(page, sc->gfp_mask)) |
870 | goto activate_locked; |
871 | if (!mapping && page_count(page) == 1) { |
872 | unlock_page(page); |
873 | if (put_page_testzero(page)) |
874 | goto free_it; |
875 | else { |
876 | /* |
877 | * rare race with speculative reference. |
878 | * the speculative reference will free |
879 | * this page shortly, so we may |
880 | * increment nr_reclaimed here (and |
881 | * leave it off the LRU). |
882 | */ |
883 | nr_reclaimed++; |
884 | continue; |
885 | } |
886 | } |
887 | } |
888 | |
889 | if (!mapping || !__remove_mapping(mapping, page)) |
890 | goto keep_locked; |
891 | |
892 | /* |
893 | * At this point, we have no other references and there is |
894 | * no way to pick any more up (removed from LRU, removed |
895 | * from pagecache). Can use non-atomic bitops now (and |
896 | * we obviously don't have to worry about waking up a process |
897 | * waiting on the page lock, because there are no references. |
898 | */ |
899 | __clear_page_locked(page); |
900 | free_it: |
901 | nr_reclaimed++; |
902 | |
903 | /* |
904 | * Is there need to periodically free_page_list? It would |
905 | * appear not as the counts should be low |
906 | */ |
907 | list_add(&page->lru, &free_pages); |
908 | continue; |
909 | |
910 | cull_mlocked: |
911 | if (PageSwapCache(page)) |
912 | try_to_free_swap(page); |
913 | unlock_page(page); |
914 | putback_lru_page(page); |
915 | reset_reclaim_mode(sc); |
916 | continue; |
917 | |
918 | activate_locked: |
919 | /* Not a candidate for swapping, so reclaim swap space. */ |
920 | if (PageSwapCache(page) && vm_swap_full()) |
921 | try_to_free_swap(page); |
922 | VM_BUG_ON(PageActive(page)); |
923 | SetPageActive(page); |
924 | pgactivate++; |
925 | keep_locked: |
926 | unlock_page(page); |
927 | keep: |
928 | reset_reclaim_mode(sc); |
929 | keep_lumpy: |
930 | list_add(&page->lru, &ret_pages); |
931 | VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); |
932 | } |
933 | |
934 | /* |
935 | * Tag a zone as congested if all the dirty pages encountered were |
936 | * backed by a congested BDI. In this case, reclaimers should just |
937 | * back off and wait for congestion to clear because further reclaim |
938 | * will encounter the same problem |
939 | */ |
940 | if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc)) |
941 | zone_set_flag(zone, ZONE_CONGESTED); |
942 | |
943 | free_page_list(&free_pages); |
944 | |
945 | list_splice(&ret_pages, page_list); |
946 | count_vm_events(PGACTIVATE, pgactivate); |
947 | return nr_reclaimed; |
948 | } |
949 | |
950 | /* |
951 | * Attempt to remove the specified page from its LRU. Only take this page |
952 | * if it is of the appropriate PageActive status. Pages which are being |
953 | * freed elsewhere are also ignored. |
954 | * |
955 | * page: page to consider |
956 | * mode: one of the LRU isolation modes defined above |
957 | * |
958 | * returns 0 on success, -ve errno on failure. |
959 | */ |
960 | int __isolate_lru_page(struct page *page, int mode, int file) |
961 | { |
962 | int ret = -EINVAL; |
963 | |
964 | /* Only take pages on the LRU. */ |
965 | if (!PageLRU(page)) |
966 | return ret; |
967 | |
968 | /* |
969 | * When checking the active state, we need to be sure we are |
970 | * dealing with comparible boolean values. Take the logical not |
971 | * of each. |
972 | */ |
973 | if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) |
974 | return ret; |
975 | |
976 | if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) |
977 | return ret; |
978 | |
979 | /* |
980 | * When this function is being called for lumpy reclaim, we |
981 | * initially look into all LRU pages, active, inactive and |
982 | * unevictable; only give shrink_page_list evictable pages. |
983 | */ |
984 | if (PageUnevictable(page)) |
985 | return ret; |
986 | |
987 | ret = -EBUSY; |
988 | |
989 | if (likely(get_page_unless_zero(page))) { |
990 | /* |
991 | * Be careful not to clear PageLRU until after we're |
992 | * sure the page is not being freed elsewhere -- the |
993 | * page release code relies on it. |
994 | */ |
995 | ClearPageLRU(page); |
996 | ret = 0; |
997 | } |
998 | |
999 | return ret; |
1000 | } |
1001 | |
1002 | /* |
1003 | * zone->lru_lock is heavily contended. Some of the functions that |
1004 | * shrink the lists perform better by taking out a batch of pages |
1005 | * and working on them outside the LRU lock. |
1006 | * |
1007 | * For pagecache intensive workloads, this function is the hottest |
1008 | * spot in the kernel (apart from copy_*_user functions). |
1009 | * |
1010 | * Appropriate locks must be held before calling this function. |
1011 | * |
1012 | * @nr_to_scan: The number of pages to look through on the list. |
1013 | * @src: The LRU list to pull pages off. |
1014 | * @dst: The temp list to put pages on to. |
1015 | * @scanned: The number of pages that were scanned. |
1016 | * @order: The caller's attempted allocation order |
1017 | * @mode: One of the LRU isolation modes |
1018 | * @file: True [1] if isolating file [!anon] pages |
1019 | * |
1020 | * returns how many pages were moved onto *@dst. |
1021 | */ |
1022 | static unsigned long isolate_lru_pages(unsigned long nr_to_scan, |
1023 | struct list_head *src, struct list_head *dst, |
1024 | unsigned long *scanned, int order, int mode, int file) |
1025 | { |
1026 | unsigned long nr_taken = 0; |
1027 | unsigned long nr_lumpy_taken = 0; |
1028 | unsigned long nr_lumpy_dirty = 0; |
1029 | unsigned long nr_lumpy_failed = 0; |
1030 | unsigned long scan; |
1031 | |
1032 | for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { |
1033 | struct page *page; |
1034 | unsigned long pfn; |
1035 | unsigned long end_pfn; |
1036 | unsigned long page_pfn; |
1037 | int zone_id; |
1038 | |
1039 | page = lru_to_page(src); |
1040 | prefetchw_prev_lru_page(page, src, flags); |
1041 | |
1042 | VM_BUG_ON(!PageLRU(page)); |
1043 | |
1044 | switch (__isolate_lru_page(page, mode, file)) { |
1045 | case 0: |
1046 | list_move(&page->lru, dst); |
1047 | mem_cgroup_del_lru(page); |
1048 | nr_taken += hpage_nr_pages(page); |
1049 | break; |
1050 | |
1051 | case -EBUSY: |
1052 | /* else it is being freed elsewhere */ |
1053 | list_move(&page->lru, src); |
1054 | mem_cgroup_rotate_lru_list(page, page_lru(page)); |
1055 | continue; |
1056 | |
1057 | default: |
1058 | BUG(); |
1059 | } |
1060 | |
1061 | if (!order) |
1062 | continue; |
1063 | |
1064 | /* |
1065 | * Attempt to take all pages in the order aligned region |
1066 | * surrounding the tag page. Only take those pages of |
1067 | * the same active state as that tag page. We may safely |
1068 | * round the target page pfn down to the requested order |
1069 | * as the mem_map is guaranteed valid out to MAX_ORDER, |
1070 | * where that page is in a different zone we will detect |
1071 | * it from its zone id and abort this block scan. |
1072 | */ |
1073 | zone_id = page_zone_id(page); |
1074 | page_pfn = page_to_pfn(page); |
1075 | pfn = page_pfn & ~((1 << order) - 1); |
1076 | end_pfn = pfn + (1 << order); |
1077 | for (; pfn < end_pfn; pfn++) { |
1078 | struct page *cursor_page; |
1079 | |
1080 | /* The target page is in the block, ignore it. */ |
1081 | if (unlikely(pfn == page_pfn)) |
1082 | continue; |
1083 | |
1084 | /* Avoid holes within the zone. */ |
1085 | if (unlikely(!pfn_valid_within(pfn))) |
1086 | break; |
1087 | |
1088 | cursor_page = pfn_to_page(pfn); |
1089 | |
1090 | /* Check that we have not crossed a zone boundary. */ |
1091 | if (unlikely(page_zone_id(cursor_page) != zone_id)) |
1092 | break; |
1093 | |
1094 | /* |
1095 | * If we don't have enough swap space, reclaiming of |
1096 | * anon page which don't already have a swap slot is |
1097 | * pointless. |
1098 | */ |
1099 | if (nr_swap_pages <= 0 && PageAnon(cursor_page) && |
1100 | !PageSwapCache(cursor_page)) |
1101 | break; |
1102 | |
1103 | if (__isolate_lru_page(cursor_page, mode, file) == 0) { |
1104 | list_move(&cursor_page->lru, dst); |
1105 | mem_cgroup_del_lru(cursor_page); |
1106 | nr_taken += hpage_nr_pages(page); |
1107 | nr_lumpy_taken++; |
1108 | if (PageDirty(cursor_page)) |
1109 | nr_lumpy_dirty++; |
1110 | scan++; |
1111 | } else { |
1112 | /* the page is freed already. */ |
1113 | if (!page_count(cursor_page)) |
1114 | continue; |
1115 | break; |
1116 | } |
1117 | } |
1118 | |
1119 | /* If we break out of the loop above, lumpy reclaim failed */ |
1120 | if (pfn < end_pfn) |
1121 | nr_lumpy_failed++; |
1122 | } |
1123 | |
1124 | *scanned = scan; |
1125 | |
1126 | trace_mm_vmscan_lru_isolate(order, |
1127 | nr_to_scan, scan, |
1128 | nr_taken, |
1129 | nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, |
1130 | mode); |
1131 | return nr_taken; |
1132 | } |
1133 | |
1134 | static unsigned long isolate_pages_global(unsigned long nr, |
1135 | struct list_head *dst, |
1136 | unsigned long *scanned, int order, |
1137 | int mode, struct zone *z, |
1138 | int active, int file) |
1139 | { |
1140 | int lru = LRU_BASE; |
1141 | if (active) |
1142 | lru += LRU_ACTIVE; |
1143 | if (file) |
1144 | lru += LRU_FILE; |
1145 | return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, |
1146 | mode, file); |
1147 | } |
1148 | |
1149 | /* |
1150 | * clear_active_flags() is a helper for shrink_active_list(), clearing |
1151 | * any active bits from the pages in the list. |
1152 | */ |
1153 | static unsigned long clear_active_flags(struct list_head *page_list, |
1154 | unsigned int *count) |
1155 | { |
1156 | int nr_active = 0; |
1157 | int lru; |
1158 | struct page *page; |
1159 | |
1160 | list_for_each_entry(page, page_list, lru) { |
1161 | int numpages = hpage_nr_pages(page); |
1162 | lru = page_lru_base_type(page); |
1163 | if (PageActive(page)) { |
1164 | lru += LRU_ACTIVE; |
1165 | ClearPageActive(page); |
1166 | nr_active += numpages; |
1167 | } |
1168 | if (count) |
1169 | count[lru] += numpages; |
1170 | } |
1171 | |
1172 | return nr_active; |
1173 | } |
1174 | |
1175 | /** |
1176 | * isolate_lru_page - tries to isolate a page from its LRU list |
1177 | * @page: page to isolate from its LRU list |
1178 | * |
1179 | * Isolates a @page from an LRU list, clears PageLRU and adjusts the |
1180 | * vmstat statistic corresponding to whatever LRU list the page was on. |
1181 | * |
1182 | * Returns 0 if the page was removed from an LRU list. |
1183 | * Returns -EBUSY if the page was not on an LRU list. |
1184 | * |
1185 | * The returned page will have PageLRU() cleared. If it was found on |
1186 | * the active list, it will have PageActive set. If it was found on |
1187 | * the unevictable list, it will have the PageUnevictable bit set. That flag |
1188 | * may need to be cleared by the caller before letting the page go. |
1189 | * |
1190 | * The vmstat statistic corresponding to the list on which the page was |
1191 | * found will be decremented. |
1192 | * |
1193 | * Restrictions: |
1194 | * (1) Must be called with an elevated refcount on the page. This is a |
1195 | * fundamentnal difference from isolate_lru_pages (which is called |
1196 | * without a stable reference). |
1197 | * (2) the lru_lock must not be held. |
1198 | * (3) interrupts must be enabled. |
1199 | */ |
1200 | int isolate_lru_page(struct page *page) |
1201 | { |
1202 | int ret = -EBUSY; |
1203 | |
1204 | if (PageLRU(page)) { |
1205 | struct zone *zone = page_zone(page); |
1206 | |
1207 | spin_lock_irq(&zone->lru_lock); |
1208 | if (PageLRU(page) && get_page_unless_zero(page)) { |
1209 | int lru = page_lru(page); |
1210 | ret = 0; |
1211 | ClearPageLRU(page); |
1212 | |
1213 | del_page_from_lru_list(zone, page, lru); |
1214 | } |
1215 | spin_unlock_irq(&zone->lru_lock); |
1216 | } |
1217 | return ret; |
1218 | } |
1219 | |
1220 | /* |
1221 | * Are there way too many processes in the direct reclaim path already? |
1222 | */ |
1223 | static int too_many_isolated(struct zone *zone, int file, |
1224 | struct scan_control *sc) |
1225 | { |
1226 | unsigned long inactive, isolated; |
1227 | |
1228 | if (current_is_kswapd()) |
1229 | return 0; |
1230 | |
1231 | if (!scanning_global_lru(sc)) |
1232 | return 0; |
1233 | |
1234 | if (file) { |
1235 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); |
1236 | isolated = zone_page_state(zone, NR_ISOLATED_FILE); |
1237 | } else { |
1238 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
1239 | isolated = zone_page_state(zone, NR_ISOLATED_ANON); |
1240 | } |
1241 | |
1242 | return isolated > inactive; |
1243 | } |
1244 | |
1245 | /* |
1246 | * TODO: Try merging with migrations version of putback_lru_pages |
1247 | */ |
1248 | static noinline_for_stack void |
1249 | putback_lru_pages(struct zone *zone, struct scan_control *sc, |
1250 | unsigned long nr_anon, unsigned long nr_file, |
1251 | struct list_head *page_list) |
1252 | { |
1253 | struct page *page; |
1254 | struct pagevec pvec; |
1255 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
1256 | |
1257 | pagevec_init(&pvec, 1); |
1258 | |
1259 | /* |
1260 | * Put back any unfreeable pages. |
1261 | */ |
1262 | spin_lock(&zone->lru_lock); |
1263 | while (!list_empty(page_list)) { |
1264 | int lru; |
1265 | page = lru_to_page(page_list); |
1266 | VM_BUG_ON(PageLRU(page)); |
1267 | list_del(&page->lru); |
1268 | if (unlikely(!page_evictable(page, NULL))) { |
1269 | spin_unlock_irq(&zone->lru_lock); |
1270 | putback_lru_page(page); |
1271 | spin_lock_irq(&zone->lru_lock); |
1272 | continue; |
1273 | } |
1274 | SetPageLRU(page); |
1275 | lru = page_lru(page); |
1276 | add_page_to_lru_list(zone, page, lru); |
1277 | if (is_active_lru(lru)) { |
1278 | int file = is_file_lru(lru); |
1279 | int numpages = hpage_nr_pages(page); |
1280 | reclaim_stat->recent_rotated[file] += numpages; |
1281 | } |
1282 | if (!pagevec_add(&pvec, page)) { |
1283 | spin_unlock_irq(&zone->lru_lock); |
1284 | __pagevec_release(&pvec); |
1285 | spin_lock_irq(&zone->lru_lock); |
1286 | } |
1287 | } |
1288 | __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); |
1289 | __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); |
1290 | |
1291 | spin_unlock_irq(&zone->lru_lock); |
1292 | pagevec_release(&pvec); |
1293 | } |
1294 | |
1295 | static noinline_for_stack void update_isolated_counts(struct zone *zone, |
1296 | struct scan_control *sc, |
1297 | unsigned long *nr_anon, |
1298 | unsigned long *nr_file, |
1299 | struct list_head *isolated_list) |
1300 | { |
1301 | unsigned long nr_active; |
1302 | unsigned int count[NR_LRU_LISTS] = { 0, }; |
1303 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
1304 | |
1305 | nr_active = clear_active_flags(isolated_list, count); |
1306 | __count_vm_events(PGDEACTIVATE, nr_active); |
1307 | |
1308 | __mod_zone_page_state(zone, NR_ACTIVE_FILE, |
1309 | -count[LRU_ACTIVE_FILE]); |
1310 | __mod_zone_page_state(zone, NR_INACTIVE_FILE, |
1311 | -count[LRU_INACTIVE_FILE]); |
1312 | __mod_zone_page_state(zone, NR_ACTIVE_ANON, |
1313 | -count[LRU_ACTIVE_ANON]); |
1314 | __mod_zone_page_state(zone, NR_INACTIVE_ANON, |
1315 | -count[LRU_INACTIVE_ANON]); |
1316 | |
1317 | *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; |
1318 | *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; |
1319 | __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); |
1320 | __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); |
1321 | |
1322 | reclaim_stat->recent_scanned[0] += *nr_anon; |
1323 | reclaim_stat->recent_scanned[1] += *nr_file; |
1324 | } |
1325 | |
1326 | /* |
1327 | * Returns true if the caller should wait to clean dirty/writeback pages. |
1328 | * |
1329 | * If we are direct reclaiming for contiguous pages and we do not reclaim |
1330 | * everything in the list, try again and wait for writeback IO to complete. |
1331 | * This will stall high-order allocations noticeably. Only do that when really |
1332 | * need to free the pages under high memory pressure. |
1333 | */ |
1334 | static inline bool should_reclaim_stall(unsigned long nr_taken, |
1335 | unsigned long nr_freed, |
1336 | int priority, |
1337 | struct scan_control *sc) |
1338 | { |
1339 | int lumpy_stall_priority; |
1340 | |
1341 | /* kswapd should not stall on sync IO */ |
1342 | if (current_is_kswapd()) |
1343 | return false; |
1344 | |
1345 | /* Only stall on lumpy reclaim */ |
1346 | if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) |
1347 | return false; |
1348 | |
1349 | /* If we have relaimed everything on the isolated list, no stall */ |
1350 | if (nr_freed == nr_taken) |
1351 | return false; |
1352 | |
1353 | /* |
1354 | * For high-order allocations, there are two stall thresholds. |
1355 | * High-cost allocations stall immediately where as lower |
1356 | * order allocations such as stacks require the scanning |
1357 | * priority to be much higher before stalling. |
1358 | */ |
1359 | if (sc->order > PAGE_ALLOC_COSTLY_ORDER) |
1360 | lumpy_stall_priority = DEF_PRIORITY; |
1361 | else |
1362 | lumpy_stall_priority = DEF_PRIORITY / 3; |
1363 | |
1364 | return priority <= lumpy_stall_priority; |
1365 | } |
1366 | |
1367 | /* |
1368 | * shrink_inactive_list() is a helper for shrink_zone(). It returns the number |
1369 | * of reclaimed pages |
1370 | */ |
1371 | static noinline_for_stack unsigned long |
1372 | shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, |
1373 | struct scan_control *sc, int priority, int file) |
1374 | { |
1375 | LIST_HEAD(page_list); |
1376 | unsigned long nr_scanned; |
1377 | unsigned long nr_reclaimed = 0; |
1378 | unsigned long nr_taken; |
1379 | unsigned long nr_anon; |
1380 | unsigned long nr_file; |
1381 | |
1382 | while (unlikely(too_many_isolated(zone, file, sc))) { |
1383 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
1384 | |
1385 | /* We are about to die and free our memory. Return now. */ |
1386 | if (fatal_signal_pending(current)) |
1387 | return SWAP_CLUSTER_MAX; |
1388 | } |
1389 | |
1390 | set_reclaim_mode(priority, sc, false); |
1391 | lru_add_drain(); |
1392 | spin_lock_irq(&zone->lru_lock); |
1393 | |
1394 | if (scanning_global_lru(sc)) { |
1395 | nr_taken = isolate_pages_global(nr_to_scan, |
1396 | &page_list, &nr_scanned, sc->order, |
1397 | sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? |
1398 | ISOLATE_BOTH : ISOLATE_INACTIVE, |
1399 | zone, 0, file); |
1400 | zone->pages_scanned += nr_scanned; |
1401 | if (current_is_kswapd()) |
1402 | __count_zone_vm_events(PGSCAN_KSWAPD, zone, |
1403 | nr_scanned); |
1404 | else |
1405 | __count_zone_vm_events(PGSCAN_DIRECT, zone, |
1406 | nr_scanned); |
1407 | } else { |
1408 | nr_taken = mem_cgroup_isolate_pages(nr_to_scan, |
1409 | &page_list, &nr_scanned, sc->order, |
1410 | sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? |
1411 | ISOLATE_BOTH : ISOLATE_INACTIVE, |
1412 | zone, sc->mem_cgroup, |
1413 | 0, file); |
1414 | /* |
1415 | * mem_cgroup_isolate_pages() keeps track of |
1416 | * scanned pages on its own. |
1417 | */ |
1418 | } |
1419 | |
1420 | if (nr_taken == 0) { |
1421 | spin_unlock_irq(&zone->lru_lock); |
1422 | return 0; |
1423 | } |
1424 | |
1425 | update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list); |
1426 | |
1427 | spin_unlock_irq(&zone->lru_lock); |
1428 | |
1429 | nr_reclaimed = shrink_page_list(&page_list, zone, sc); |
1430 | |
1431 | /* Check if we should syncronously wait for writeback */ |
1432 | if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { |
1433 | set_reclaim_mode(priority, sc, true); |
1434 | nr_reclaimed += shrink_page_list(&page_list, zone, sc); |
1435 | } |
1436 | |
1437 | local_irq_disable(); |
1438 | if (current_is_kswapd()) |
1439 | __count_vm_events(KSWAPD_STEAL, nr_reclaimed); |
1440 | __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); |
1441 | |
1442 | putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); |
1443 | |
1444 | trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, |
1445 | zone_idx(zone), |
1446 | nr_scanned, nr_reclaimed, |
1447 | priority, |
1448 | trace_shrink_flags(file, sc->reclaim_mode)); |
1449 | return nr_reclaimed; |
1450 | } |
1451 | |
1452 | /* |
1453 | * This moves pages from the active list to the inactive list. |
1454 | * |
1455 | * We move them the other way if the page is referenced by one or more |
1456 | * processes, from rmap. |
1457 | * |
1458 | * If the pages are mostly unmapped, the processing is fast and it is |
1459 | * appropriate to hold zone->lru_lock across the whole operation. But if |
1460 | * the pages are mapped, the processing is slow (page_referenced()) so we |
1461 | * should drop zone->lru_lock around each page. It's impossible to balance |
1462 | * this, so instead we remove the pages from the LRU while processing them. |
1463 | * It is safe to rely on PG_active against the non-LRU pages in here because |
1464 | * nobody will play with that bit on a non-LRU page. |
1465 | * |
1466 | * The downside is that we have to touch page->_count against each page. |
1467 | * But we had to alter page->flags anyway. |
1468 | */ |
1469 | |
1470 | static void move_active_pages_to_lru(struct zone *zone, |
1471 | struct list_head *list, |
1472 | enum lru_list lru) |
1473 | { |
1474 | unsigned long pgmoved = 0; |
1475 | struct pagevec pvec; |
1476 | struct page *page; |
1477 | |
1478 | pagevec_init(&pvec, 1); |
1479 | |
1480 | while (!list_empty(list)) { |
1481 | page = lru_to_page(list); |
1482 | |
1483 | VM_BUG_ON(PageLRU(page)); |
1484 | SetPageLRU(page); |
1485 | |
1486 | list_move(&page->lru, &zone->lru[lru].list); |
1487 | mem_cgroup_add_lru_list(page, lru); |
1488 | pgmoved += hpage_nr_pages(page); |
1489 | |
1490 | if (!pagevec_add(&pvec, page) || list_empty(list)) { |
1491 | spin_unlock_irq(&zone->lru_lock); |
1492 | if (buffer_heads_over_limit) |
1493 | pagevec_strip(&pvec); |
1494 | __pagevec_release(&pvec); |
1495 | spin_lock_irq(&zone->lru_lock); |
1496 | } |
1497 | } |
1498 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); |
1499 | if (!is_active_lru(lru)) |
1500 | __count_vm_events(PGDEACTIVATE, pgmoved); |
1501 | } |
1502 | |
1503 | static void shrink_active_list(unsigned long nr_pages, struct zone *zone, |
1504 | struct scan_control *sc, int priority, int file) |
1505 | { |
1506 | unsigned long nr_taken; |
1507 | unsigned long pgscanned; |
1508 | unsigned long vm_flags; |
1509 | LIST_HEAD(l_hold); /* The pages which were snipped off */ |
1510 | LIST_HEAD(l_active); |
1511 | LIST_HEAD(l_inactive); |
1512 | struct page *page; |
1513 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
1514 | unsigned long nr_rotated = 0; |
1515 | |
1516 | lru_add_drain(); |
1517 | spin_lock_irq(&zone->lru_lock); |
1518 | if (scanning_global_lru(sc)) { |
1519 | nr_taken = isolate_pages_global(nr_pages, &l_hold, |
1520 | &pgscanned, sc->order, |
1521 | ISOLATE_ACTIVE, zone, |
1522 | 1, file); |
1523 | zone->pages_scanned += pgscanned; |
1524 | } else { |
1525 | nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold, |
1526 | &pgscanned, sc->order, |
1527 | ISOLATE_ACTIVE, zone, |
1528 | sc->mem_cgroup, 1, file); |
1529 | /* |
1530 | * mem_cgroup_isolate_pages() keeps track of |
1531 | * scanned pages on its own. |
1532 | */ |
1533 | } |
1534 | |
1535 | reclaim_stat->recent_scanned[file] += nr_taken; |
1536 | |
1537 | __count_zone_vm_events(PGREFILL, zone, pgscanned); |
1538 | if (file) |
1539 | __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); |
1540 | else |
1541 | __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); |
1542 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); |
1543 | spin_unlock_irq(&zone->lru_lock); |
1544 | |
1545 | while (!list_empty(&l_hold)) { |
1546 | cond_resched(); |
1547 | page = lru_to_page(&l_hold); |
1548 | list_del(&page->lru); |
1549 | |
1550 | if (unlikely(!page_evictable(page, NULL))) { |
1551 | putback_lru_page(page); |
1552 | continue; |
1553 | } |
1554 | |
1555 | if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { |
1556 | nr_rotated += hpage_nr_pages(page); |
1557 | /* |
1558 | * Identify referenced, file-backed active pages and |
1559 | * give them one more trip around the active list. So |
1560 | * that executable code get better chances to stay in |
1561 | * memory under moderate memory pressure. Anon pages |
1562 | * are not likely to be evicted by use-once streaming |
1563 | * IO, plus JVM can create lots of anon VM_EXEC pages, |
1564 | * so we ignore them here. |
1565 | */ |
1566 | if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { |
1567 | list_add(&page->lru, &l_active); |
1568 | continue; |
1569 | } |
1570 | } |
1571 | |
1572 | ClearPageActive(page); /* we are de-activating */ |
1573 | list_add(&page->lru, &l_inactive); |
1574 | } |
1575 | |
1576 | /* |
1577 | * Move pages back to the lru list. |
1578 | */ |
1579 | spin_lock_irq(&zone->lru_lock); |
1580 | /* |
1581 | * Count referenced pages from currently used mappings as rotated, |
1582 | * even though only some of them are actually re-activated. This |
1583 | * helps balance scan pressure between file and anonymous pages in |
1584 | * get_scan_ratio. |
1585 | */ |
1586 | reclaim_stat->recent_rotated[file] += nr_rotated; |
1587 | |
1588 | move_active_pages_to_lru(zone, &l_active, |
1589 | LRU_ACTIVE + file * LRU_FILE); |
1590 | move_active_pages_to_lru(zone, &l_inactive, |
1591 | LRU_BASE + file * LRU_FILE); |
1592 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); |
1593 | spin_unlock_irq(&zone->lru_lock); |
1594 | } |
1595 | |
1596 | #ifdef CONFIG_SWAP |
1597 | static int inactive_anon_is_low_global(struct zone *zone) |
1598 | { |
1599 | unsigned long active, inactive; |
1600 | |
1601 | active = zone_page_state(zone, NR_ACTIVE_ANON); |
1602 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
1603 | |
1604 | if (inactive * zone->inactive_ratio < active) |
1605 | return 1; |
1606 | |
1607 | return 0; |
1608 | } |
1609 | |
1610 | /** |
1611 | * inactive_anon_is_low - check if anonymous pages need to be deactivated |
1612 | * @zone: zone to check |
1613 | * @sc: scan control of this context |
1614 | * |
1615 | * Returns true if the zone does not have enough inactive anon pages, |
1616 | * meaning some active anon pages need to be deactivated. |
1617 | */ |
1618 | static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) |
1619 | { |
1620 | int low; |
1621 | |
1622 | /* |
1623 | * If we don't have swap space, anonymous page deactivation |
1624 | * is pointless. |
1625 | */ |
1626 | if (!total_swap_pages) |
1627 | return 0; |
1628 | |
1629 | if (scanning_global_lru(sc)) |
1630 | low = inactive_anon_is_low_global(zone); |
1631 | else |
1632 | low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); |
1633 | return low; |
1634 | } |
1635 | #else |
1636 | static inline int inactive_anon_is_low(struct zone *zone, |
1637 | struct scan_control *sc) |
1638 | { |
1639 | return 0; |
1640 | } |
1641 | #endif |
1642 | |
1643 | static int inactive_file_is_low_global(struct zone *zone) |
1644 | { |
1645 | unsigned long active, inactive; |
1646 | |
1647 | active = zone_page_state(zone, NR_ACTIVE_FILE); |
1648 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); |
1649 | |
1650 | return (active > inactive); |
1651 | } |
1652 | |
1653 | /** |
1654 | * inactive_file_is_low - check if file pages need to be deactivated |
1655 | * @zone: zone to check |
1656 | * @sc: scan control of this context |
1657 | * |
1658 | * When the system is doing streaming IO, memory pressure here |
1659 | * ensures that active file pages get deactivated, until more |
1660 | * than half of the file pages are on the inactive list. |
1661 | * |
1662 | * Once we get to that situation, protect the system's working |
1663 | * set from being evicted by disabling active file page aging. |
1664 | * |
1665 | * This uses a different ratio than the anonymous pages, because |
1666 | * the page cache uses a use-once replacement algorithm. |
1667 | */ |
1668 | static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) |
1669 | { |
1670 | int low; |
1671 | |
1672 | if (scanning_global_lru(sc)) |
1673 | low = inactive_file_is_low_global(zone); |
1674 | else |
1675 | low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); |
1676 | return low; |
1677 | } |
1678 | |
1679 | static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, |
1680 | int file) |
1681 | { |
1682 | if (file) |
1683 | return inactive_file_is_low(zone, sc); |
1684 | else |
1685 | return inactive_anon_is_low(zone, sc); |
1686 | } |
1687 | |
1688 | static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, |
1689 | struct zone *zone, struct scan_control *sc, int priority) |
1690 | { |
1691 | int file = is_file_lru(lru); |
1692 | |
1693 | if (is_active_lru(lru)) { |
1694 | if (inactive_list_is_low(zone, sc, file)) |
1695 | shrink_active_list(nr_to_scan, zone, sc, priority, file); |
1696 | return 0; |
1697 | } |
1698 | |
1699 | return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); |
1700 | } |
1701 | |
1702 | /* |
1703 | * Smallish @nr_to_scan's are deposited in @nr_saved_scan, |
1704 | * until we collected @swap_cluster_max pages to scan. |
1705 | */ |
1706 | static unsigned long nr_scan_try_batch(unsigned long nr_to_scan, |
1707 | unsigned long *nr_saved_scan) |
1708 | { |
1709 | unsigned long nr; |
1710 | |
1711 | *nr_saved_scan += nr_to_scan; |
1712 | nr = *nr_saved_scan; |
1713 | |
1714 | if (nr >= SWAP_CLUSTER_MAX) |
1715 | *nr_saved_scan = 0; |
1716 | else |
1717 | nr = 0; |
1718 | |
1719 | return nr; |
1720 | } |
1721 | |
1722 | /* |
1723 | * Determine how aggressively the anon and file LRU lists should be |
1724 | * scanned. The relative value of each set of LRU lists is determined |
1725 | * by looking at the fraction of the pages scanned we did rotate back |
1726 | * onto the active list instead of evict. |
1727 | * |
1728 | * nr[0] = anon pages to scan; nr[1] = file pages to scan |
1729 | */ |
1730 | static void get_scan_count(struct zone *zone, struct scan_control *sc, |
1731 | unsigned long *nr, int priority) |
1732 | { |
1733 | unsigned long anon, file, free; |
1734 | unsigned long anon_prio, file_prio; |
1735 | unsigned long ap, fp; |
1736 | struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
1737 | u64 fraction[2], denominator; |
1738 | enum lru_list l; |
1739 | int noswap = 0; |
1740 | |
1741 | /* If we have no swap space, do not bother scanning anon pages. */ |
1742 | if (!sc->may_swap || (nr_swap_pages <= 0)) { |
1743 | noswap = 1; |
1744 | fraction[0] = 0; |
1745 | fraction[1] = 1; |
1746 | denominator = 1; |
1747 | goto out; |
1748 | } |
1749 | |
1750 | anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + |
1751 | zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); |
1752 | file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + |
1753 | zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); |
1754 | |
1755 | if (scanning_global_lru(sc)) { |
1756 | free = zone_page_state(zone, NR_FREE_PAGES); |
1757 | /* If we have very few page cache pages, |
1758 | force-scan anon pages. */ |
1759 | if (unlikely(file + free <= high_wmark_pages(zone))) { |
1760 | fraction[0] = 1; |
1761 | fraction[1] = 0; |
1762 | denominator = 1; |
1763 | goto out; |
1764 | } |
1765 | } |
1766 | |
1767 | /* |
1768 | * With swappiness at 100, anonymous and file have the same priority. |
1769 | * This scanning priority is essentially the inverse of IO cost. |
1770 | */ |
1771 | anon_prio = sc->swappiness; |
1772 | file_prio = 200 - sc->swappiness; |
1773 | |
1774 | /* |
1775 | * OK, so we have swap space and a fair amount of page cache |
1776 | * pages. We use the recently rotated / recently scanned |
1777 | * ratios to determine how valuable each cache is. |
1778 | * |
1779 | * Because workloads change over time (and to avoid overflow) |
1780 | * we keep these statistics as a floating average, which ends |
1781 | * up weighing recent references more than old ones. |
1782 | * |
1783 | * anon in [0], file in [1] |
1784 | */ |
1785 | spin_lock_irq(&zone->lru_lock); |
1786 | if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { |
1787 | reclaim_stat->recent_scanned[0] /= 2; |
1788 | reclaim_stat->recent_rotated[0] /= 2; |
1789 | } |
1790 | |
1791 | if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { |
1792 | reclaim_stat->recent_scanned[1] /= 2; |
1793 | reclaim_stat->recent_rotated[1] /= 2; |
1794 | } |
1795 | |
1796 | /* |
1797 | * The amount of pressure on anon vs file pages is inversely |
1798 | * proportional to the fraction of recently scanned pages on |
1799 | * each list that were recently referenced and in active use. |
1800 | */ |
1801 | ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); |
1802 | ap /= reclaim_stat->recent_rotated[0] + 1; |
1803 | |
1804 | fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); |
1805 | fp /= reclaim_stat->recent_rotated[1] + 1; |
1806 | spin_unlock_irq(&zone->lru_lock); |
1807 | |
1808 | fraction[0] = ap; |
1809 | fraction[1] = fp; |
1810 | denominator = ap + fp + 1; |
1811 | out: |
1812 | for_each_evictable_lru(l) { |
1813 | int file = is_file_lru(l); |
1814 | unsigned long scan; |
1815 | |
1816 | scan = zone_nr_lru_pages(zone, sc, l); |
1817 | if (priority || noswap) { |
1818 | scan >>= priority; |
1819 | scan = div64_u64(scan * fraction[file], denominator); |
1820 | } |
1821 | nr[l] = nr_scan_try_batch(scan, |
1822 | &reclaim_stat->nr_saved_scan[l]); |
1823 | } |
1824 | } |
1825 | |
1826 | /* |
1827 | * Reclaim/compaction depends on a number of pages being freed. To avoid |
1828 | * disruption to the system, a small number of order-0 pages continue to be |
1829 | * rotated and reclaimed in the normal fashion. However, by the time we get |
1830 | * back to the allocator and call try_to_compact_zone(), we ensure that |
1831 | * there are enough free pages for it to be likely successful |
1832 | */ |
1833 | static inline bool should_continue_reclaim(struct zone *zone, |
1834 | unsigned long nr_reclaimed, |
1835 | unsigned long nr_scanned, |
1836 | struct scan_control *sc) |
1837 | { |
1838 | unsigned long pages_for_compaction; |
1839 | unsigned long inactive_lru_pages; |
1840 | |
1841 | /* If not in reclaim/compaction mode, stop */ |
1842 | if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) |
1843 | return false; |
1844 | |
1845 | /* Consider stopping depending on scan and reclaim activity */ |
1846 | if (sc->gfp_mask & __GFP_REPEAT) { |
1847 | /* |
1848 | * For __GFP_REPEAT allocations, stop reclaiming if the |
1849 | * full LRU list has been scanned and we are still failing |
1850 | * to reclaim pages. This full LRU scan is potentially |
1851 | * expensive but a __GFP_REPEAT caller really wants to succeed |
1852 | */ |
1853 | if (!nr_reclaimed && !nr_scanned) |
1854 | return false; |
1855 | } else { |
1856 | /* |
1857 | * For non-__GFP_REPEAT allocations which can presumably |
1858 | * fail without consequence, stop if we failed to reclaim |
1859 | * any pages from the last SWAP_CLUSTER_MAX number of |
1860 | * pages that were scanned. This will return to the |
1861 | * caller faster at the risk reclaim/compaction and |
1862 | * the resulting allocation attempt fails |
1863 | */ |
1864 | if (!nr_reclaimed) |
1865 | return false; |
1866 | } |
1867 | |
1868 | /* |
1869 | * If we have not reclaimed enough pages for compaction and the |
1870 | * inactive lists are large enough, continue reclaiming |
1871 | */ |
1872 | pages_for_compaction = (2UL << sc->order); |
1873 | inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) + |
1874 | zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); |
1875 | if (sc->nr_reclaimed < pages_for_compaction && |
1876 | inactive_lru_pages > pages_for_compaction) |
1877 | return true; |
1878 | |
1879 | /* If compaction would go ahead or the allocation would succeed, stop */ |
1880 | switch (compaction_suitable(zone, sc->order)) { |
1881 | case COMPACT_PARTIAL: |
1882 | case COMPACT_CONTINUE: |
1883 | return false; |
1884 | default: |
1885 | return true; |
1886 | } |
1887 | } |
1888 | |
1889 | /* |
1890 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. |
1891 | */ |
1892 | static void shrink_zone(int priority, struct zone *zone, |
1893 | struct scan_control *sc) |
1894 | { |
1895 | unsigned long nr[NR_LRU_LISTS]; |
1896 | unsigned long nr_to_scan; |
1897 | enum lru_list l; |
1898 | unsigned long nr_reclaimed, nr_scanned; |
1899 | unsigned long nr_to_reclaim = sc->nr_to_reclaim; |
1900 | |
1901 | restart: |
1902 | nr_reclaimed = 0; |
1903 | nr_scanned = sc->nr_scanned; |
1904 | get_scan_count(zone, sc, nr, priority); |
1905 | |
1906 | while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || |
1907 | nr[LRU_INACTIVE_FILE]) { |
1908 | for_each_evictable_lru(l) { |
1909 | if (nr[l]) { |
1910 | nr_to_scan = min_t(unsigned long, |
1911 | nr[l], SWAP_CLUSTER_MAX); |
1912 | nr[l] -= nr_to_scan; |
1913 | |
1914 | nr_reclaimed += shrink_list(l, nr_to_scan, |
1915 | zone, sc, priority); |
1916 | } |
1917 | } |
1918 | /* |
1919 | * On large memory systems, scan >> priority can become |
1920 | * really large. This is fine for the starting priority; |
1921 | * we want to put equal scanning pressure on each zone. |
1922 | * However, if the VM has a harder time of freeing pages, |
1923 | * with multiple processes reclaiming pages, the total |
1924 | * freeing target can get unreasonably large. |
1925 | */ |
1926 | if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) |
1927 | break; |
1928 | } |
1929 | sc->nr_reclaimed += nr_reclaimed; |
1930 | |
1931 | /* |
1932 | * Even if we did not try to evict anon pages at all, we want to |
1933 | * rebalance the anon lru active/inactive ratio. |
1934 | */ |
1935 | if (inactive_anon_is_low(zone, sc)) |
1936 | shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); |
1937 | |
1938 | /* reclaim/compaction might need reclaim to continue */ |
1939 | if (should_continue_reclaim(zone, nr_reclaimed, |
1940 | sc->nr_scanned - nr_scanned, sc)) |
1941 | goto restart; |
1942 | |
1943 | throttle_vm_writeout(sc->gfp_mask); |
1944 | } |
1945 | |
1946 | /* |
1947 | * This is the direct reclaim path, for page-allocating processes. We only |
1948 | * try to reclaim pages from zones which will satisfy the caller's allocation |
1949 | * request. |
1950 | * |
1951 | * We reclaim from a zone even if that zone is over high_wmark_pages(zone). |
1952 | * Because: |
1953 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order |
1954 | * allocation or |
1955 | * b) The target zone may be at high_wmark_pages(zone) but the lower zones |
1956 | * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' |
1957 | * zone defense algorithm. |
1958 | * |
1959 | * If a zone is deemed to be full of pinned pages then just give it a light |
1960 | * scan then give up on it. |
1961 | */ |
1962 | static void shrink_zones(int priority, struct zonelist *zonelist, |
1963 | struct scan_control *sc) |
1964 | { |
1965 | struct zoneref *z; |
1966 | struct zone *zone; |
1967 | |
1968 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
1969 | gfp_zone(sc->gfp_mask), sc->nodemask) { |
1970 | if (!populated_zone(zone)) |
1971 | continue; |
1972 | /* |
1973 | * Take care memory controller reclaiming has small influence |
1974 | * to global LRU. |
1975 | */ |
1976 | if (scanning_global_lru(sc)) { |
1977 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
1978 | continue; |
1979 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
1980 | continue; /* Let kswapd poll it */ |
1981 | } |
1982 | |
1983 | shrink_zone(priority, zone, sc); |
1984 | } |
1985 | } |
1986 | |
1987 | static bool zone_reclaimable(struct zone *zone) |
1988 | { |
1989 | return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; |
1990 | } |
1991 | |
1992 | /* All zones in zonelist are unreclaimable? */ |
1993 | static bool all_unreclaimable(struct zonelist *zonelist, |
1994 | struct scan_control *sc) |
1995 | { |
1996 | struct zoneref *z; |
1997 | struct zone *zone; |
1998 | |
1999 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
2000 | gfp_zone(sc->gfp_mask), sc->nodemask) { |
2001 | if (!populated_zone(zone)) |
2002 | continue; |
2003 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2004 | continue; |
2005 | if (!zone->all_unreclaimable) |
2006 | return false; |
2007 | } |
2008 | |
2009 | return true; |
2010 | } |
2011 | |
2012 | /* |
2013 | * This is the main entry point to direct page reclaim. |
2014 | * |
2015 | * If a full scan of the inactive list fails to free enough memory then we |
2016 | * are "out of memory" and something needs to be killed. |
2017 | * |
2018 | * If the caller is !__GFP_FS then the probability of a failure is reasonably |
2019 | * high - the zone may be full of dirty or under-writeback pages, which this |
2020 | * caller can't do much about. We kick the writeback threads and take explicit |
2021 | * naps in the hope that some of these pages can be written. But if the |
2022 | * allocating task holds filesystem locks which prevent writeout this might not |
2023 | * work, and the allocation attempt will fail. |
2024 | * |
2025 | * returns: 0, if no pages reclaimed |
2026 | * else, the number of pages reclaimed |
2027 | */ |
2028 | static unsigned long do_try_to_free_pages(struct zonelist *zonelist, |
2029 | struct scan_control *sc) |
2030 | { |
2031 | int priority; |
2032 | unsigned long total_scanned = 0; |
2033 | struct reclaim_state *reclaim_state = current->reclaim_state; |
2034 | struct zoneref *z; |
2035 | struct zone *zone; |
2036 | unsigned long writeback_threshold; |
2037 | |
2038 | get_mems_allowed(); |
2039 | delayacct_freepages_start(); |
2040 | |
2041 | if (scanning_global_lru(sc)) |
2042 | count_vm_event(ALLOCSTALL); |
2043 | |
2044 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
2045 | sc->nr_scanned = 0; |
2046 | if (!priority) |
2047 | disable_swap_token(); |
2048 | shrink_zones(priority, zonelist, sc); |
2049 | /* |
2050 | * Don't shrink slabs when reclaiming memory from |
2051 | * over limit cgroups |
2052 | */ |
2053 | if (scanning_global_lru(sc)) { |
2054 | unsigned long lru_pages = 0; |
2055 | for_each_zone_zonelist(zone, z, zonelist, |
2056 | gfp_zone(sc->gfp_mask)) { |
2057 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2058 | continue; |
2059 | |
2060 | lru_pages += zone_reclaimable_pages(zone); |
2061 | } |
2062 | |
2063 | shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages); |
2064 | if (reclaim_state) { |
2065 | sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
2066 | reclaim_state->reclaimed_slab = 0; |
2067 | } |
2068 | } |
2069 | total_scanned += sc->nr_scanned; |
2070 | if (sc->nr_reclaimed >= sc->nr_to_reclaim) |
2071 | goto out; |
2072 | |
2073 | /* |
2074 | * Try to write back as many pages as we just scanned. This |
2075 | * tends to cause slow streaming writers to write data to the |
2076 | * disk smoothly, at the dirtying rate, which is nice. But |
2077 | * that's undesirable in laptop mode, where we *want* lumpy |
2078 | * writeout. So in laptop mode, write out the whole world. |
2079 | */ |
2080 | writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; |
2081 | if (total_scanned > writeback_threshold) { |
2082 | wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); |
2083 | sc->may_writepage = 1; |
2084 | } |
2085 | |
2086 | /* Take a nap, wait for some writeback to complete */ |
2087 | if (!sc->hibernation_mode && sc->nr_scanned && |
2088 | priority < DEF_PRIORITY - 2) { |
2089 | struct zone *preferred_zone; |
2090 | |
2091 | first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), |
2092 | &cpuset_current_mems_allowed, |
2093 | &preferred_zone); |
2094 | wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); |
2095 | } |
2096 | } |
2097 | |
2098 | out: |
2099 | delayacct_freepages_end(); |
2100 | put_mems_allowed(); |
2101 | |
2102 | if (sc->nr_reclaimed) |
2103 | return sc->nr_reclaimed; |
2104 | |
2105 | /* |
2106 | * As hibernation is going on, kswapd is freezed so that it can't mark |
2107 | * the zone into all_unreclaimable. Thus bypassing all_unreclaimable |
2108 | * check. |
2109 | */ |
2110 | if (oom_killer_disabled) |
2111 | return 0; |
2112 | |
2113 | /* top priority shrink_zones still had more to do? don't OOM, then */ |
2114 | if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) |
2115 | return 1; |
2116 | |
2117 | return 0; |
2118 | } |
2119 | |
2120 | unsigned long try_to_free_pages(struct zonelist *zonelist, int order, |
2121 | gfp_t gfp_mask, nodemask_t *nodemask) |
2122 | { |
2123 | unsigned long nr_reclaimed; |
2124 | struct scan_control sc = { |
2125 | .gfp_mask = gfp_mask, |
2126 | .may_writepage = !laptop_mode, |
2127 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2128 | .may_unmap = 1, |
2129 | .may_swap = 1, |
2130 | .swappiness = vm_swappiness, |
2131 | .order = order, |
2132 | .mem_cgroup = NULL, |
2133 | .nodemask = nodemask, |
2134 | }; |
2135 | |
2136 | trace_mm_vmscan_direct_reclaim_begin(order, |
2137 | sc.may_writepage, |
2138 | gfp_mask); |
2139 | |
2140 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc); |
2141 | |
2142 | trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); |
2143 | |
2144 | return nr_reclaimed; |
2145 | } |
2146 | |
2147 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
2148 | |
2149 | unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, |
2150 | gfp_t gfp_mask, bool noswap, |
2151 | unsigned int swappiness, |
2152 | struct zone *zone) |
2153 | { |
2154 | struct scan_control sc = { |
2155 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2156 | .may_writepage = !laptop_mode, |
2157 | .may_unmap = 1, |
2158 | .may_swap = !noswap, |
2159 | .swappiness = swappiness, |
2160 | .order = 0, |
2161 | .mem_cgroup = mem, |
2162 | }; |
2163 | sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
2164 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); |
2165 | |
2166 | trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, |
2167 | sc.may_writepage, |
2168 | sc.gfp_mask); |
2169 | |
2170 | /* |
2171 | * NOTE: Although we can get the priority field, using it |
2172 | * here is not a good idea, since it limits the pages we can scan. |
2173 | * if we don't reclaim here, the shrink_zone from balance_pgdat |
2174 | * will pick up pages from other mem cgroup's as well. We hack |
2175 | * the priority and make it zero. |
2176 | */ |
2177 | shrink_zone(0, zone, &sc); |
2178 | |
2179 | trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); |
2180 | |
2181 | return sc.nr_reclaimed; |
2182 | } |
2183 | |
2184 | unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, |
2185 | gfp_t gfp_mask, |
2186 | bool noswap, |
2187 | unsigned int swappiness) |
2188 | { |
2189 | struct zonelist *zonelist; |
2190 | unsigned long nr_reclaimed; |
2191 | struct scan_control sc = { |
2192 | .may_writepage = !laptop_mode, |
2193 | .may_unmap = 1, |
2194 | .may_swap = !noswap, |
2195 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2196 | .swappiness = swappiness, |
2197 | .order = 0, |
2198 | .mem_cgroup = mem_cont, |
2199 | .nodemask = NULL, /* we don't care the placement */ |
2200 | }; |
2201 | |
2202 | sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
2203 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); |
2204 | zonelist = NODE_DATA(numa_node_id())->node_zonelists; |
2205 | |
2206 | trace_mm_vmscan_memcg_reclaim_begin(0, |
2207 | sc.may_writepage, |
2208 | sc.gfp_mask); |
2209 | |
2210 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc); |
2211 | |
2212 | trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); |
2213 | |
2214 | return nr_reclaimed; |
2215 | } |
2216 | #endif |
2217 | |
2218 | /* |
2219 | * pgdat_balanced is used when checking if a node is balanced for high-order |
2220 | * allocations. Only zones that meet watermarks and are in a zone allowed |
2221 | * by the callers classzone_idx are added to balanced_pages. The total of |
2222 | * balanced pages must be at least 25% of the zones allowed by classzone_idx |
2223 | * for the node to be considered balanced. Forcing all zones to be balanced |
2224 | * for high orders can cause excessive reclaim when there are imbalanced zones. |
2225 | * The choice of 25% is due to |
2226 | * o a 16M DMA zone that is balanced will not balance a zone on any |
2227 | * reasonable sized machine |
2228 | * o On all other machines, the top zone must be at least a reasonable |
2229 | * percentage of the middle zones. For example, on 32-bit x86, highmem |
2230 | * would need to be at least 256M for it to be balance a whole node. |
2231 | * Similarly, on x86-64 the Normal zone would need to be at least 1G |
2232 | * to balance a node on its own. These seemed like reasonable ratios. |
2233 | */ |
2234 | static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, |
2235 | int classzone_idx) |
2236 | { |
2237 | unsigned long present_pages = 0; |
2238 | int i; |
2239 | |
2240 | for (i = 0; i <= classzone_idx; i++) |
2241 | present_pages += pgdat->node_zones[i].present_pages; |
2242 | |
2243 | return balanced_pages > (present_pages >> 2); |
2244 | } |
2245 | |
2246 | /* is kswapd sleeping prematurely? */ |
2247 | static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, |
2248 | int classzone_idx) |
2249 | { |
2250 | int i; |
2251 | unsigned long balanced = 0; |
2252 | bool all_zones_ok = true; |
2253 | |
2254 | /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ |
2255 | if (remaining) |
2256 | return true; |
2257 | |
2258 | /* Check the watermark levels */ |
2259 | for (i = 0; i < pgdat->nr_zones; i++) { |
2260 | struct zone *zone = pgdat->node_zones + i; |
2261 | |
2262 | if (!populated_zone(zone)) |
2263 | continue; |
2264 | |
2265 | /* |
2266 | * balance_pgdat() skips over all_unreclaimable after |
2267 | * DEF_PRIORITY. Effectively, it considers them balanced so |
2268 | * they must be considered balanced here as well if kswapd |
2269 | * is to sleep |
2270 | */ |
2271 | if (zone->all_unreclaimable) { |
2272 | balanced += zone->present_pages; |
2273 | continue; |
2274 | } |
2275 | |
2276 | if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), |
2277 | classzone_idx, 0)) |
2278 | all_zones_ok = false; |
2279 | else |
2280 | balanced += zone->present_pages; |
2281 | } |
2282 | |
2283 | /* |
2284 | * For high-order requests, the balanced zones must contain at least |
2285 | * 25% of the nodes pages for kswapd to sleep. For order-0, all zones |
2286 | * must be balanced |
2287 | */ |
2288 | if (order) |
2289 | return pgdat_balanced(pgdat, balanced, classzone_idx); |
2290 | else |
2291 | return !all_zones_ok; |
2292 | } |
2293 | |
2294 | /* |
2295 | * For kswapd, balance_pgdat() will work across all this node's zones until |
2296 | * they are all at high_wmark_pages(zone). |
2297 | * |
2298 | * Returns the final order kswapd was reclaiming at |
2299 | * |
2300 | * There is special handling here for zones which are full of pinned pages. |
2301 | * This can happen if the pages are all mlocked, or if they are all used by |
2302 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. |
2303 | * What we do is to detect the case where all pages in the zone have been |
2304 | * scanned twice and there has been zero successful reclaim. Mark the zone as |
2305 | * dead and from now on, only perform a short scan. Basically we're polling |
2306 | * the zone for when the problem goes away. |
2307 | * |
2308 | * kswapd scans the zones in the highmem->normal->dma direction. It skips |
2309 | * zones which have free_pages > high_wmark_pages(zone), but once a zone is |
2310 | * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the |
2311 | * lower zones regardless of the number of free pages in the lower zones. This |
2312 | * interoperates with the page allocator fallback scheme to ensure that aging |
2313 | * of pages is balanced across the zones. |
2314 | */ |
2315 | static unsigned long balance_pgdat(pg_data_t *pgdat, int order, |
2316 | int *classzone_idx) |
2317 | { |
2318 | int all_zones_ok; |
2319 | unsigned long balanced; |
2320 | int priority; |
2321 | int i; |
2322 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ |
2323 | unsigned long total_scanned; |
2324 | struct reclaim_state *reclaim_state = current->reclaim_state; |
2325 | struct scan_control sc = { |
2326 | .gfp_mask = GFP_KERNEL, |
2327 | .may_unmap = 1, |
2328 | .may_swap = 1, |
2329 | /* |
2330 | * kswapd doesn't want to be bailed out while reclaim. because |
2331 | * we want to put equal scanning pressure on each zone. |
2332 | */ |
2333 | .nr_to_reclaim = ULONG_MAX, |
2334 | .swappiness = vm_swappiness, |
2335 | .order = order, |
2336 | .mem_cgroup = NULL, |
2337 | }; |
2338 | loop_again: |
2339 | total_scanned = 0; |
2340 | sc.nr_reclaimed = 0; |
2341 | sc.may_writepage = !laptop_mode; |
2342 | count_vm_event(PAGEOUTRUN); |
2343 | |
2344 | for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
2345 | unsigned long lru_pages = 0; |
2346 | int has_under_min_watermark_zone = 0; |
2347 | |
2348 | /* The swap token gets in the way of swapout... */ |
2349 | if (!priority) |
2350 | disable_swap_token(); |
2351 | |
2352 | all_zones_ok = 1; |
2353 | balanced = 0; |
2354 | |
2355 | /* |
2356 | * Scan in the highmem->dma direction for the highest |
2357 | * zone which needs scanning |
2358 | */ |
2359 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { |
2360 | struct zone *zone = pgdat->node_zones + i; |
2361 | |
2362 | if (!populated_zone(zone)) |
2363 | continue; |
2364 | |
2365 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
2366 | continue; |
2367 | |
2368 | /* |
2369 | * Do some background aging of the anon list, to give |
2370 | * pages a chance to be referenced before reclaiming. |
2371 | */ |
2372 | if (inactive_anon_is_low(zone, &sc)) |
2373 | shrink_active_list(SWAP_CLUSTER_MAX, zone, |
2374 | &sc, priority, 0); |
2375 | |
2376 | if (!zone_watermark_ok_safe(zone, order, |
2377 | high_wmark_pages(zone), 0, 0)) { |
2378 | end_zone = i; |
2379 | *classzone_idx = i; |
2380 | break; |
2381 | } |
2382 | } |
2383 | if (i < 0) |
2384 | goto out; |
2385 | |
2386 | for (i = 0; i <= end_zone; i++) { |
2387 | struct zone *zone = pgdat->node_zones + i; |
2388 | |
2389 | lru_pages += zone_reclaimable_pages(zone); |
2390 | } |
2391 | |
2392 | /* |
2393 | * Now scan the zone in the dma->highmem direction, stopping |
2394 | * at the last zone which needs scanning. |
2395 | * |
2396 | * We do this because the page allocator works in the opposite |
2397 | * direction. This prevents the page allocator from allocating |
2398 | * pages behind kswapd's direction of progress, which would |
2399 | * cause too much scanning of the lower zones. |
2400 | */ |
2401 | for (i = 0; i <= end_zone; i++) { |
2402 | struct zone *zone = pgdat->node_zones + i; |
2403 | int nr_slab; |
2404 | unsigned long balance_gap; |
2405 | |
2406 | if (!populated_zone(zone)) |
2407 | continue; |
2408 | |
2409 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
2410 | continue; |
2411 | |
2412 | sc.nr_scanned = 0; |
2413 | |
2414 | /* |
2415 | * Call soft limit reclaim before calling shrink_zone. |
2416 | * For now we ignore the return value |
2417 | */ |
2418 | mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask); |
2419 | |
2420 | /* |
2421 | * We put equal pressure on every zone, unless |
2422 | * one zone has way too many pages free |
2423 | * already. The "too many pages" is defined |
2424 | * as the high wmark plus a "gap" where the |
2425 | * gap is either the low watermark or 1% |
2426 | * of the zone, whichever is smaller. |
2427 | */ |
2428 | balance_gap = min(low_wmark_pages(zone), |
2429 | (zone->present_pages + |
2430 | KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / |
2431 | KSWAPD_ZONE_BALANCE_GAP_RATIO); |
2432 | if (!zone_watermark_ok_safe(zone, order, |
2433 | high_wmark_pages(zone) + balance_gap, |
2434 | end_zone, 0)) |
2435 | shrink_zone(priority, zone, &sc); |
2436 | reclaim_state->reclaimed_slab = 0; |
2437 | nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, |
2438 | lru_pages); |
2439 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; |
2440 | total_scanned += sc.nr_scanned; |
2441 | |
2442 | if (zone->all_unreclaimable) |
2443 | continue; |
2444 | if (nr_slab == 0 && |
2445 | !zone_reclaimable(zone)) |
2446 | zone->all_unreclaimable = 1; |
2447 | /* |
2448 | * If we've done a decent amount of scanning and |
2449 | * the reclaim ratio is low, start doing writepage |
2450 | * even in laptop mode |
2451 | */ |
2452 | if (total_scanned > SWAP_CLUSTER_MAX * 2 && |
2453 | total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) |
2454 | sc.may_writepage = 1; |
2455 | |
2456 | if (!zone_watermark_ok_safe(zone, order, |
2457 | high_wmark_pages(zone), end_zone, 0)) { |
2458 | all_zones_ok = 0; |
2459 | /* |
2460 | * We are still under min water mark. This |
2461 | * means that we have a GFP_ATOMIC allocation |
2462 | * failure risk. Hurry up! |
2463 | */ |
2464 | if (!zone_watermark_ok_safe(zone, order, |
2465 | min_wmark_pages(zone), end_zone, 0)) |
2466 | has_under_min_watermark_zone = 1; |
2467 | } else { |
2468 | /* |
2469 | * If a zone reaches its high watermark, |
2470 | * consider it to be no longer congested. It's |
2471 | * possible there are dirty pages backed by |
2472 | * congested BDIs but as pressure is relieved, |
2473 | * spectulatively avoid congestion waits |
2474 | */ |
2475 | zone_clear_flag(zone, ZONE_CONGESTED); |
2476 | if (i <= *classzone_idx) |
2477 | balanced += zone->present_pages; |
2478 | } |
2479 | |
2480 | } |
2481 | if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) |
2482 | break; /* kswapd: all done */ |
2483 | /* |
2484 | * OK, kswapd is getting into trouble. Take a nap, then take |
2485 | * another pass across the zones. |
2486 | */ |
2487 | if (total_scanned && (priority < DEF_PRIORITY - 2)) { |
2488 | if (has_under_min_watermark_zone) |
2489 | count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); |
2490 | else |
2491 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
2492 | } |
2493 | |
2494 | /* |
2495 | * We do this so kswapd doesn't build up large priorities for |
2496 | * example when it is freeing in parallel with allocators. It |
2497 | * matches the direct reclaim path behaviour in terms of impact |
2498 | * on zone->*_priority. |
2499 | */ |
2500 | if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) |
2501 | break; |
2502 | } |
2503 | out: |
2504 | |
2505 | /* |
2506 | * order-0: All zones must meet high watermark for a balanced node |
2507 | * high-order: Balanced zones must make up at least 25% of the node |
2508 | * for the node to be balanced |
2509 | */ |
2510 | if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { |
2511 | cond_resched(); |
2512 | |
2513 | try_to_freeze(); |
2514 | |
2515 | /* |
2516 | * Fragmentation may mean that the system cannot be |
2517 | * rebalanced for high-order allocations in all zones. |
2518 | * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, |
2519 | * it means the zones have been fully scanned and are still |
2520 | * not balanced. For high-order allocations, there is |
2521 | * little point trying all over again as kswapd may |
2522 | * infinite loop. |
2523 | * |
2524 | * Instead, recheck all watermarks at order-0 as they |
2525 | * are the most important. If watermarks are ok, kswapd will go |
2526 | * back to sleep. High-order users can still perform direct |
2527 | * reclaim if they wish. |
2528 | */ |
2529 | if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) |
2530 | order = sc.order = 0; |
2531 | |
2532 | goto loop_again; |
2533 | } |
2534 | |
2535 | /* |
2536 | * If kswapd was reclaiming at a higher order, it has the option of |
2537 | * sleeping without all zones being balanced. Before it does, it must |
2538 | * ensure that the watermarks for order-0 on *all* zones are met and |
2539 | * that the congestion flags are cleared. The congestion flag must |
2540 | * be cleared as kswapd is the only mechanism that clears the flag |
2541 | * and it is potentially going to sleep here. |
2542 | */ |
2543 | if (order) { |
2544 | for (i = 0; i <= end_zone; i++) { |
2545 | struct zone *zone = pgdat->node_zones + i; |
2546 | |
2547 | if (!populated_zone(zone)) |
2548 | continue; |
2549 | |
2550 | if (zone->all_unreclaimable && priority != DEF_PRIORITY) |
2551 | continue; |
2552 | |
2553 | /* Confirm the zone is balanced for order-0 */ |
2554 | if (!zone_watermark_ok(zone, 0, |
2555 | high_wmark_pages(zone), 0, 0)) { |
2556 | order = sc.order = 0; |
2557 | goto loop_again; |
2558 | } |
2559 | |
2560 | /* If balanced, clear the congested flag */ |
2561 | zone_clear_flag(zone, ZONE_CONGESTED); |
2562 | } |
2563 | } |
2564 | |
2565 | /* |
2566 | * Return the order we were reclaiming at so sleeping_prematurely() |
2567 | * makes a decision on the order we were last reclaiming at. However, |
2568 | * if another caller entered the allocator slow path while kswapd |
2569 | * was awake, order will remain at the higher level |
2570 | */ |
2571 | *classzone_idx = end_zone; |
2572 | return order; |
2573 | } |
2574 | |
2575 | static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) |
2576 | { |
2577 | long remaining = 0; |
2578 | DEFINE_WAIT(wait); |
2579 | |
2580 | if (freezing(current) || kthread_should_stop()) |
2581 | return; |
2582 | |
2583 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
2584 | |
2585 | /* Try to sleep for a short interval */ |
2586 | if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { |
2587 | remaining = schedule_timeout(HZ/10); |
2588 | finish_wait(&pgdat->kswapd_wait, &wait); |
2589 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
2590 | } |
2591 | |
2592 | /* |
2593 | * After a short sleep, check if it was a premature sleep. If not, then |
2594 | * go fully to sleep until explicitly woken up. |
2595 | */ |
2596 | if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { |
2597 | trace_mm_vmscan_kswapd_sleep(pgdat->node_id); |
2598 | |
2599 | /* |
2600 | * vmstat counters are not perfectly accurate and the estimated |
2601 | * value for counters such as NR_FREE_PAGES can deviate from the |
2602 | * true value by nr_online_cpus * threshold. To avoid the zone |
2603 | * watermarks being breached while under pressure, we reduce the |
2604 | * per-cpu vmstat threshold while kswapd is awake and restore |
2605 | * them before going back to sleep. |
2606 | */ |
2607 | set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); |
2608 | schedule(); |
2609 | set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); |
2610 | } else { |
2611 | if (remaining) |
2612 | count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); |
2613 | else |
2614 | count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); |
2615 | } |
2616 | finish_wait(&pgdat->kswapd_wait, &wait); |
2617 | } |
2618 | |
2619 | /* |
2620 | * The background pageout daemon, started as a kernel thread |
2621 | * from the init process. |
2622 | * |
2623 | * This basically trickles out pages so that we have _some_ |
2624 | * free memory available even if there is no other activity |
2625 | * that frees anything up. This is needed for things like routing |
2626 | * etc, where we otherwise might have all activity going on in |
2627 | * asynchronous contexts that cannot page things out. |
2628 | * |
2629 | * If there are applications that are active memory-allocators |
2630 | * (most normal use), this basically shouldn't matter. |
2631 | */ |
2632 | static int kswapd(void *p) |
2633 | { |
2634 | unsigned long order; |
2635 | int classzone_idx; |
2636 | pg_data_t *pgdat = (pg_data_t*)p; |
2637 | struct task_struct *tsk = current; |
2638 | |
2639 | struct reclaim_state reclaim_state = { |
2640 | .reclaimed_slab = 0, |
2641 | }; |
2642 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); |
2643 | |
2644 | lockdep_set_current_reclaim_state(GFP_KERNEL); |
2645 | |
2646 | if (!cpumask_empty(cpumask)) |
2647 | set_cpus_allowed_ptr(tsk, cpumask); |
2648 | current->reclaim_state = &reclaim_state; |
2649 | |
2650 | /* |
2651 | * Tell the memory management that we're a "memory allocator", |
2652 | * and that if we need more memory we should get access to it |
2653 | * regardless (see "__alloc_pages()"). "kswapd" should |
2654 | * never get caught in the normal page freeing logic. |
2655 | * |
2656 | * (Kswapd normally doesn't need memory anyway, but sometimes |
2657 | * you need a small amount of memory in order to be able to |
2658 | * page out something else, and this flag essentially protects |
2659 | * us from recursively trying to free more memory as we're |
2660 | * trying to free the first piece of memory in the first place). |
2661 | */ |
2662 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; |
2663 | set_freezable(); |
2664 | |
2665 | order = 0; |
2666 | classzone_idx = MAX_NR_ZONES - 1; |
2667 | for ( ; ; ) { |
2668 | unsigned long new_order; |
2669 | int new_classzone_idx; |
2670 | int ret; |
2671 | |
2672 | new_order = pgdat->kswapd_max_order; |
2673 | new_classzone_idx = pgdat->classzone_idx; |
2674 | pgdat->kswapd_max_order = 0; |
2675 | pgdat->classzone_idx = MAX_NR_ZONES - 1; |
2676 | if (order < new_order || classzone_idx > new_classzone_idx) { |
2677 | /* |
2678 | * Don't sleep if someone wants a larger 'order' |
2679 | * allocation or has tigher zone constraints |
2680 | */ |
2681 | order = new_order; |
2682 | classzone_idx = new_classzone_idx; |
2683 | } else { |
2684 | kswapd_try_to_sleep(pgdat, order, classzone_idx); |
2685 | order = pgdat->kswapd_max_order; |
2686 | classzone_idx = pgdat->classzone_idx; |
2687 | pgdat->kswapd_max_order = 0; |
2688 | pgdat->classzone_idx = MAX_NR_ZONES - 1; |
2689 | } |
2690 | |
2691 | ret = try_to_freeze(); |
2692 | if (kthread_should_stop()) |
2693 | break; |
2694 | |
2695 | /* |
2696 | * We can speed up thawing tasks if we don't call balance_pgdat |
2697 | * after returning from the refrigerator |
2698 | */ |
2699 | if (!ret) { |
2700 | trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); |
2701 | order = balance_pgdat(pgdat, order, &classzone_idx); |
2702 | } |
2703 | } |
2704 | return 0; |
2705 | } |
2706 | |
2707 | /* |
2708 | * A zone is low on free memory, so wake its kswapd task to service it. |
2709 | */ |
2710 | void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) |
2711 | { |
2712 | pg_data_t *pgdat; |
2713 | |
2714 | if (!populated_zone(zone)) |
2715 | return; |
2716 | |
2717 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2718 | return; |
2719 | pgdat = zone->zone_pgdat; |
2720 | if (pgdat->kswapd_max_order < order) { |
2721 | pgdat->kswapd_max_order = order; |
2722 | pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); |
2723 | } |
2724 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
2725 | return; |
2726 | if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) |
2727 | return; |
2728 | |
2729 | trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); |
2730 | wake_up_interruptible(&pgdat->kswapd_wait); |
2731 | } |
2732 | |
2733 | /* |
2734 | * The reclaimable count would be mostly accurate. |
2735 | * The less reclaimable pages may be |
2736 | * - mlocked pages, which will be moved to unevictable list when encountered |
2737 | * - mapped pages, which may require several travels to be reclaimed |
2738 | * - dirty pages, which is not "instantly" reclaimable |
2739 | */ |
2740 | unsigned long global_reclaimable_pages(void) |
2741 | { |
2742 | int nr; |
2743 | |
2744 | nr = global_page_state(NR_ACTIVE_FILE) + |
2745 | global_page_state(NR_INACTIVE_FILE); |
2746 | |
2747 | if (nr_swap_pages > 0) |
2748 | nr += global_page_state(NR_ACTIVE_ANON) + |
2749 | global_page_state(NR_INACTIVE_ANON); |
2750 | |
2751 | return nr; |
2752 | } |
2753 | |
2754 | unsigned long zone_reclaimable_pages(struct zone *zone) |
2755 | { |
2756 | int nr; |
2757 | |
2758 | nr = zone_page_state(zone, NR_ACTIVE_FILE) + |
2759 | zone_page_state(zone, NR_INACTIVE_FILE); |
2760 | |
2761 | if (nr_swap_pages > 0) |
2762 | nr += zone_page_state(zone, NR_ACTIVE_ANON) + |
2763 | zone_page_state(zone, NR_INACTIVE_ANON); |
2764 | |
2765 | return nr; |
2766 | } |
2767 | |
2768 | #ifdef CONFIG_HIBERNATION |
2769 | /* |
2770 | * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of |
2771 | * freed pages. |
2772 | * |
2773 | * Rather than trying to age LRUs the aim is to preserve the overall |
2774 | * LRU order by reclaiming preferentially |
2775 | * inactive > active > active referenced > active mapped |
2776 | */ |
2777 | unsigned long shrink_all_memory(unsigned long nr_to_reclaim) |
2778 | { |
2779 | struct reclaim_state reclaim_state; |
2780 | struct scan_control sc = { |
2781 | .gfp_mask = GFP_HIGHUSER_MOVABLE, |
2782 | .may_swap = 1, |
2783 | .may_unmap = 1, |
2784 | .may_writepage = 1, |
2785 | .nr_to_reclaim = nr_to_reclaim, |
2786 | .hibernation_mode = 1, |
2787 | .swappiness = vm_swappiness, |
2788 | .order = 0, |
2789 | }; |
2790 | struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); |
2791 | struct task_struct *p = current; |
2792 | unsigned long nr_reclaimed; |
2793 | |
2794 | p->flags |= PF_MEMALLOC; |
2795 | lockdep_set_current_reclaim_state(sc.gfp_mask); |
2796 | reclaim_state.reclaimed_slab = 0; |
2797 | p->reclaim_state = &reclaim_state; |
2798 | |
2799 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc); |
2800 | |
2801 | p->reclaim_state = NULL; |
2802 | lockdep_clear_current_reclaim_state(); |
2803 | p->flags &= ~PF_MEMALLOC; |
2804 | |
2805 | return nr_reclaimed; |
2806 | } |
2807 | #endif /* CONFIG_HIBERNATION */ |
2808 | |
2809 | /* It's optimal to keep kswapds on the same CPUs as their memory, but |
2810 | not required for correctness. So if the last cpu in a node goes |
2811 | away, we get changed to run anywhere: as the first one comes back, |
2812 | restore their cpu bindings. */ |
2813 | static int __devinit cpu_callback(struct notifier_block *nfb, |
2814 | unsigned long action, void *hcpu) |
2815 | { |
2816 | int nid; |
2817 | |
2818 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { |
2819 | for_each_node_state(nid, N_HIGH_MEMORY) { |
2820 | pg_data_t *pgdat = NODE_DATA(nid); |
2821 | const struct cpumask *mask; |
2822 | |
2823 | mask = cpumask_of_node(pgdat->node_id); |
2824 | |
2825 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
2826 | /* One of our CPUs online: restore mask */ |
2827 | set_cpus_allowed_ptr(pgdat->kswapd, mask); |
2828 | } |
2829 | } |
2830 | return NOTIFY_OK; |
2831 | } |
2832 | |
2833 | /* |
2834 | * This kswapd start function will be called by init and node-hot-add. |
2835 | * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. |
2836 | */ |
2837 | int kswapd_run(int nid) |
2838 | { |
2839 | pg_data_t *pgdat = NODE_DATA(nid); |
2840 | int ret = 0; |
2841 | |
2842 | if (pgdat->kswapd) |
2843 | return 0; |
2844 | |
2845 | pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); |
2846 | if (IS_ERR(pgdat->kswapd)) { |
2847 | /* failure at boot is fatal */ |
2848 | BUG_ON(system_state == SYSTEM_BOOTING); |
2849 | printk("Failed to start kswapd on node %d\n",nid); |
2850 | ret = -1; |
2851 | } |
2852 | return ret; |
2853 | } |
2854 | |
2855 | /* |
2856 | * Called by memory hotplug when all memory in a node is offlined. |
2857 | */ |
2858 | void kswapd_stop(int nid) |
2859 | { |
2860 | struct task_struct *kswapd = NODE_DATA(nid)->kswapd; |
2861 | |
2862 | if (kswapd) |
2863 | kthread_stop(kswapd); |
2864 | } |
2865 | |
2866 | static int __init kswapd_init(void) |
2867 | { |
2868 | int nid; |
2869 | |
2870 | swap_setup(); |
2871 | for_each_node_state(nid, N_HIGH_MEMORY) |
2872 | kswapd_run(nid); |
2873 | hotcpu_notifier(cpu_callback, 0); |
2874 | return 0; |
2875 | } |
2876 | |
2877 | module_init(kswapd_init) |
2878 | |
2879 | #ifdef CONFIG_NUMA |
2880 | /* |
2881 | * Zone reclaim mode |
2882 | * |
2883 | * If non-zero call zone_reclaim when the number of free pages falls below |
2884 | * the watermarks. |
2885 | */ |
2886 | int zone_reclaim_mode __read_mostly; |
2887 | |
2888 | #define RECLAIM_OFF 0 |
2889 | #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ |
2890 | #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ |
2891 | #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ |
2892 | |
2893 | /* |
2894 | * Priority for ZONE_RECLAIM. This determines the fraction of pages |
2895 | * of a node considered for each zone_reclaim. 4 scans 1/16th of |
2896 | * a zone. |
2897 | */ |
2898 | #define ZONE_RECLAIM_PRIORITY 4 |
2899 | |
2900 | /* |
2901 | * Percentage of pages in a zone that must be unmapped for zone_reclaim to |
2902 | * occur. |
2903 | */ |
2904 | int sysctl_min_unmapped_ratio = 1; |
2905 | |
2906 | /* |
2907 | * If the number of slab pages in a zone grows beyond this percentage then |
2908 | * slab reclaim needs to occur. |
2909 | */ |
2910 | int sysctl_min_slab_ratio = 5; |
2911 | |
2912 | static inline unsigned long zone_unmapped_file_pages(struct zone *zone) |
2913 | { |
2914 | unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); |
2915 | unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + |
2916 | zone_page_state(zone, NR_ACTIVE_FILE); |
2917 | |
2918 | /* |
2919 | * It's possible for there to be more file mapped pages than |
2920 | * accounted for by the pages on the file LRU lists because |
2921 | * tmpfs pages accounted for as ANON can also be FILE_MAPPED |
2922 | */ |
2923 | return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; |
2924 | } |
2925 | |
2926 | /* Work out how many page cache pages we can reclaim in this reclaim_mode */ |
2927 | static long zone_pagecache_reclaimable(struct zone *zone) |
2928 | { |
2929 | long nr_pagecache_reclaimable; |
2930 | long delta = 0; |
2931 | |
2932 | /* |
2933 | * If RECLAIM_SWAP is set, then all file pages are considered |
2934 | * potentially reclaimable. Otherwise, we have to worry about |
2935 | * pages like swapcache and zone_unmapped_file_pages() provides |
2936 | * a better estimate |
2937 | */ |
2938 | if (zone_reclaim_mode & RECLAIM_SWAP) |
2939 | nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); |
2940 | else |
2941 | nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); |
2942 | |
2943 | /* If we can't clean pages, remove dirty pages from consideration */ |
2944 | if (!(zone_reclaim_mode & RECLAIM_WRITE)) |
2945 | delta += zone_page_state(zone, NR_FILE_DIRTY); |
2946 | |
2947 | /* Watch for any possible underflows due to delta */ |
2948 | if (unlikely(delta > nr_pagecache_reclaimable)) |
2949 | delta = nr_pagecache_reclaimable; |
2950 | |
2951 | return nr_pagecache_reclaimable - delta; |
2952 | } |
2953 | |
2954 | /* |
2955 | * Try to free up some pages from this zone through reclaim. |
2956 | */ |
2957 | static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
2958 | { |
2959 | /* Minimum pages needed in order to stay on node */ |
2960 | const unsigned long nr_pages = 1 << order; |
2961 | struct task_struct *p = current; |
2962 | struct reclaim_state reclaim_state; |
2963 | int priority; |
2964 | struct scan_control sc = { |
2965 | .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), |
2966 | .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), |
2967 | .may_swap = 1, |
2968 | .nr_to_reclaim = max_t(unsigned long, nr_pages, |
2969 | SWAP_CLUSTER_MAX), |
2970 | .gfp_mask = gfp_mask, |
2971 | .swappiness = vm_swappiness, |
2972 | .order = order, |
2973 | }; |
2974 | unsigned long nr_slab_pages0, nr_slab_pages1; |
2975 | |
2976 | cond_resched(); |
2977 | /* |
2978 | * We need to be able to allocate from the reserves for RECLAIM_SWAP |
2979 | * and we also need to be able to write out pages for RECLAIM_WRITE |
2980 | * and RECLAIM_SWAP. |
2981 | */ |
2982 | p->flags |= PF_MEMALLOC | PF_SWAPWRITE; |
2983 | lockdep_set_current_reclaim_state(gfp_mask); |
2984 | reclaim_state.reclaimed_slab = 0; |
2985 | p->reclaim_state = &reclaim_state; |
2986 | |
2987 | if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { |
2988 | /* |
2989 | * Free memory by calling shrink zone with increasing |
2990 | * priorities until we have enough memory freed. |
2991 | */ |
2992 | priority = ZONE_RECLAIM_PRIORITY; |
2993 | do { |
2994 | shrink_zone(priority, zone, &sc); |
2995 | priority--; |
2996 | } while (priority >= 0 && sc.nr_reclaimed < nr_pages); |
2997 | } |
2998 | |
2999 | nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
3000 | if (nr_slab_pages0 > zone->min_slab_pages) { |
3001 | /* |
3002 | * shrink_slab() does not currently allow us to determine how |
3003 | * many pages were freed in this zone. So we take the current |
3004 | * number of slab pages and shake the slab until it is reduced |
3005 | * by the same nr_pages that we used for reclaiming unmapped |
3006 | * pages. |
3007 | * |
3008 | * Note that shrink_slab will free memory on all zones and may |
3009 | * take a long time. |
3010 | */ |
3011 | for (;;) { |
3012 | unsigned long lru_pages = zone_reclaimable_pages(zone); |
3013 | |
3014 | /* No reclaimable slab or very low memory pressure */ |
3015 | if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages)) |
3016 | break; |
3017 | |
3018 | /* Freed enough memory */ |
3019 | nr_slab_pages1 = zone_page_state(zone, |
3020 | NR_SLAB_RECLAIMABLE); |
3021 | if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) |
3022 | break; |
3023 | } |
3024 | |
3025 | /* |
3026 | * Update nr_reclaimed by the number of slab pages we |
3027 | * reclaimed from this zone. |
3028 | */ |
3029 | nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
3030 | if (nr_slab_pages1 < nr_slab_pages0) |
3031 | sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; |
3032 | } |
3033 | |
3034 | p->reclaim_state = NULL; |
3035 | current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); |
3036 | lockdep_clear_current_reclaim_state(); |
3037 | return sc.nr_reclaimed >= nr_pages; |
3038 | } |
3039 | |
3040 | int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
3041 | { |
3042 | int node_id; |
3043 | int ret; |
3044 | |
3045 | /* |
3046 | * Zone reclaim reclaims unmapped file backed pages and |
3047 | * slab pages if we are over the defined limits. |
3048 | * |
3049 | * A small portion of unmapped file backed pages is needed for |
3050 | * file I/O otherwise pages read by file I/O will be immediately |
3051 | * thrown out if the zone is overallocated. So we do not reclaim |
3052 | * if less than a specified percentage of the zone is used by |
3053 | * unmapped file backed pages. |
3054 | */ |
3055 | if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && |
3056 | zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) |
3057 | return ZONE_RECLAIM_FULL; |
3058 | |
3059 | if (zone->all_unreclaimable) |
3060 | return ZONE_RECLAIM_FULL; |
3061 | |
3062 | /* |
3063 | * Do not scan if the allocation should not be delayed. |
3064 | */ |
3065 | if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) |
3066 | return ZONE_RECLAIM_NOSCAN; |
3067 | |
3068 | /* |
3069 | * Only run zone reclaim on the local zone or on zones that do not |
3070 | * have associated processors. This will favor the local processor |
3071 | * over remote processors and spread off node memory allocations |
3072 | * as wide as possible. |
3073 | */ |
3074 | node_id = zone_to_nid(zone); |
3075 | if (node_state(node_id, N_CPU) && node_id != numa_node_id()) |
3076 | return ZONE_RECLAIM_NOSCAN; |
3077 | |
3078 | if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) |
3079 | return ZONE_RECLAIM_NOSCAN; |
3080 | |
3081 | ret = __zone_reclaim(zone, gfp_mask, order); |
3082 | zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); |
3083 | |
3084 | if (!ret) |
3085 | count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); |
3086 | |
3087 | return ret; |
3088 | } |
3089 | #endif |
3090 | |
3091 | /* |
3092 | * page_evictable - test whether a page is evictable |
3093 | * @page: the page to test |
3094 | * @vma: the VMA in which the page is or will be mapped, may be NULL |
3095 | * |
3096 | * Test whether page is evictable--i.e., should be placed on active/inactive |
3097 | * lists vs unevictable list. The vma argument is !NULL when called from the |
3098 | * fault path to determine how to instantate a new page. |
3099 | * |
3100 | * Reasons page might not be evictable: |
3101 | * (1) page's mapping marked unevictable |
3102 | * (2) page is part of an mlocked VMA |
3103 | * |
3104 | */ |
3105 | int page_evictable(struct page *page, struct vm_area_struct *vma) |
3106 | { |
3107 | |
3108 | if (mapping_unevictable(page_mapping(page))) |
3109 | return 0; |
3110 | |
3111 | if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) |
3112 | return 0; |
3113 | |
3114 | return 1; |
3115 | } |
3116 | |
3117 | /** |
3118 | * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list |
3119 | * @page: page to check evictability and move to appropriate lru list |
3120 | * @zone: zone page is in |
3121 | * |
3122 | * Checks a page for evictability and moves the page to the appropriate |
3123 | * zone lru list. |
3124 | * |
3125 | * Restrictions: zone->lru_lock must be held, page must be on LRU and must |
3126 | * have PageUnevictable set. |
3127 | */ |
3128 | static void check_move_unevictable_page(struct page *page, struct zone *zone) |
3129 | { |
3130 | VM_BUG_ON(PageActive(page)); |
3131 | |
3132 | retry: |
3133 | ClearPageUnevictable(page); |
3134 | if (page_evictable(page, NULL)) { |
3135 | enum lru_list l = page_lru_base_type(page); |
3136 | |
3137 | __dec_zone_state(zone, NR_UNEVICTABLE); |
3138 | list_move(&page->lru, &zone->lru[l].list); |
3139 | mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); |
3140 | __inc_zone_state(zone, NR_INACTIVE_ANON + l); |
3141 | __count_vm_event(UNEVICTABLE_PGRESCUED); |
3142 | } else { |
3143 | /* |
3144 | * rotate unevictable list |
3145 | */ |
3146 | SetPageUnevictable(page); |
3147 | list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); |
3148 | mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); |
3149 | if (page_evictable(page, NULL)) |
3150 | goto retry; |
3151 | } |
3152 | } |
3153 | |
3154 | /** |
3155 | * scan_mapping_unevictable_pages - scan an address space for evictable pages |
3156 | * @mapping: struct address_space to scan for evictable pages |
3157 | * |
3158 | * Scan all pages in mapping. Check unevictable pages for |
3159 | * evictability and move them to the appropriate zone lru list. |
3160 | */ |
3161 | void scan_mapping_unevictable_pages(struct address_space *mapping) |
3162 | { |
3163 | pgoff_t next = 0; |
3164 | pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> |
3165 | PAGE_CACHE_SHIFT; |
3166 | struct zone *zone; |
3167 | struct pagevec pvec; |
3168 | |
3169 | if (mapping->nrpages == 0) |
3170 | return; |
3171 | |
3172 | pagevec_init(&pvec, 0); |
3173 | while (next < end && |
3174 | pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { |
3175 | int i; |
3176 | int pg_scanned = 0; |
3177 | |
3178 | zone = NULL; |
3179 | |
3180 | for (i = 0; i < pagevec_count(&pvec); i++) { |
3181 | struct page *page = pvec.pages[i]; |
3182 | pgoff_t page_index = page->index; |
3183 | struct zone *pagezone = page_zone(page); |
3184 | |
3185 | pg_scanned++; |
3186 | if (page_index > next) |
3187 | next = page_index; |
3188 | next++; |
3189 | |
3190 | if (pagezone != zone) { |
3191 | if (zone) |
3192 | spin_unlock_irq(&zone->lru_lock); |
3193 | zone = pagezone; |
3194 | spin_lock_irq(&zone->lru_lock); |
3195 | } |
3196 | |
3197 | if (PageLRU(page) && PageUnevictable(page)) |
3198 | check_move_unevictable_page(page, zone); |
3199 | } |
3200 | if (zone) |
3201 | spin_unlock_irq(&zone->lru_lock); |
3202 | pagevec_release(&pvec); |
3203 | |
3204 | count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); |
3205 | } |
3206 | |
3207 | } |
3208 | |
3209 | /** |
3210 | * scan_zone_unevictable_pages - check unevictable list for evictable pages |
3211 | * @zone - zone of which to scan the unevictable list |
3212 | * |
3213 | * Scan @zone's unevictable LRU lists to check for pages that have become |
3214 | * evictable. Move those that have to @zone's inactive list where they |
3215 | * become candidates for reclaim, unless shrink_inactive_zone() decides |
3216 | * to reactivate them. Pages that are still unevictable are rotated |
3217 | * back onto @zone's unevictable list. |
3218 | */ |
3219 | #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ |
3220 | static void scan_zone_unevictable_pages(struct zone *zone) |
3221 | { |
3222 | struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; |
3223 | unsigned long scan; |
3224 | unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); |
3225 | |
3226 | while (nr_to_scan > 0) { |
3227 | unsigned long batch_size = min(nr_to_scan, |
3228 | SCAN_UNEVICTABLE_BATCH_SIZE); |
3229 | |
3230 | spin_lock_irq(&zone->lru_lock); |
3231 | for (scan = 0; scan < batch_size; scan++) { |
3232 | struct page *page = lru_to_page(l_unevictable); |
3233 | |
3234 | if (!trylock_page(page)) |
3235 | continue; |
3236 | |
3237 | prefetchw_prev_lru_page(page, l_unevictable, flags); |
3238 | |
3239 | if (likely(PageLRU(page) && PageUnevictable(page))) |
3240 | check_move_unevictable_page(page, zone); |
3241 | |
3242 | unlock_page(page); |
3243 | } |
3244 | spin_unlock_irq(&zone->lru_lock); |
3245 | |
3246 | nr_to_scan -= batch_size; |
3247 | } |
3248 | } |
3249 | |
3250 | |
3251 | /** |
3252 | * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages |
3253 | * |
3254 | * A really big hammer: scan all zones' unevictable LRU lists to check for |
3255 | * pages that have become evictable. Move those back to the zones' |
3256 | * inactive list where they become candidates for reclaim. |
3257 | * This occurs when, e.g., we have unswappable pages on the unevictable lists, |
3258 | * and we add swap to the system. As such, it runs in the context of a task |
3259 | * that has possibly/probably made some previously unevictable pages |
3260 | * evictable. |
3261 | */ |
3262 | static void scan_all_zones_unevictable_pages(void) |
3263 | { |
3264 | struct zone *zone; |
3265 | |
3266 | for_each_zone(zone) { |
3267 | scan_zone_unevictable_pages(zone); |
3268 | } |
3269 | } |
3270 | |
3271 | /* |
3272 | * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of |
3273 | * all nodes' unevictable lists for evictable pages |
3274 | */ |
3275 | unsigned long scan_unevictable_pages; |
3276 | |
3277 | int scan_unevictable_handler(struct ctl_table *table, int write, |
3278 | void __user *buffer, |
3279 | size_t *length, loff_t *ppos) |
3280 | { |
3281 | proc_doulongvec_minmax(table, write, buffer, length, ppos); |
3282 | |
3283 | if (write && *(unsigned long *)table->data) |
3284 | scan_all_zones_unevictable_pages(); |
3285 | |
3286 | scan_unevictable_pages = 0; |
3287 | return 0; |
3288 | } |
3289 | |
3290 | #ifdef CONFIG_NUMA |
3291 | /* |
3292 | * per node 'scan_unevictable_pages' attribute. On demand re-scan of |
3293 | * a specified node's per zone unevictable lists for evictable pages. |
3294 | */ |
3295 | |
3296 | static ssize_t read_scan_unevictable_node(struct sys_device *dev, |
3297 | struct sysdev_attribute *attr, |
3298 | char *buf) |
3299 | { |
3300 | return sprintf(buf, "0\n"); /* always zero; should fit... */ |
3301 | } |
3302 | |
3303 | static ssize_t write_scan_unevictable_node(struct sys_device *dev, |
3304 | struct sysdev_attribute *attr, |
3305 | const char *buf, size_t count) |
3306 | { |
3307 | struct zone *node_zones = NODE_DATA(dev->id)->node_zones; |
3308 | struct zone *zone; |
3309 | unsigned long res; |
3310 | unsigned long req = strict_strtoul(buf, 10, &res); |
3311 | |
3312 | if (!req) |
3313 | return 1; /* zero is no-op */ |
3314 | |
3315 | for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { |
3316 | if (!populated_zone(zone)) |
3317 | continue; |
3318 | scan_zone_unevictable_pages(zone); |
3319 | } |
3320 | return 1; |
3321 | } |
3322 | |
3323 | |
3324 | static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, |
3325 | read_scan_unevictable_node, |
3326 | write_scan_unevictable_node); |
3327 | |
3328 | int scan_unevictable_register_node(struct node *node) |
3329 | { |
3330 | return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); |
3331 | } |
3332 | |
3333 | void scan_unevictable_unregister_node(struct node *node) |
3334 | { |
3335 | sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); |
3336 | } |
3337 | #endif |
3338 |
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