Root/
1 | /* |
2 | * linux/mm/vmscan.c |
3 | * |
4 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
5 | * |
6 | * Swap reorganised 29.12.95, Stephen Tweedie. |
7 | * kswapd added: 7.1.96 sct |
8 | * Removed kswapd_ctl limits, and swap out as many pages as needed |
9 | * to bring the system back to freepages.high: 2.4.97, Rik van Riel. |
10 | * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). |
11 | * Multiqueue VM started 5.8.00, Rik van Riel. |
12 | */ |
13 | |
14 | #include <linux/mm.h> |
15 | #include <linux/module.h> |
16 | #include <linux/gfp.h> |
17 | #include <linux/kernel_stat.h> |
18 | #include <linux/swap.h> |
19 | #include <linux/pagemap.h> |
20 | #include <linux/init.h> |
21 | #include <linux/highmem.h> |
22 | #include <linux/vmstat.h> |
23 | #include <linux/file.h> |
24 | #include <linux/writeback.h> |
25 | #include <linux/blkdev.h> |
26 | #include <linux/buffer_head.h> /* for try_to_release_page(), |
27 | buffer_heads_over_limit */ |
28 | #include <linux/mm_inline.h> |
29 | #include <linux/backing-dev.h> |
30 | #include <linux/rmap.h> |
31 | #include <linux/topology.h> |
32 | #include <linux/cpu.h> |
33 | #include <linux/cpuset.h> |
34 | #include <linux/compaction.h> |
35 | #include <linux/notifier.h> |
36 | #include <linux/rwsem.h> |
37 | #include <linux/delay.h> |
38 | #include <linux/kthread.h> |
39 | #include <linux/freezer.h> |
40 | #include <linux/memcontrol.h> |
41 | #include <linux/delayacct.h> |
42 | #include <linux/sysctl.h> |
43 | #include <linux/oom.h> |
44 | #include <linux/prefetch.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 | struct scan_control { |
57 | /* Incremented by the number of inactive pages that were scanned */ |
58 | unsigned long nr_scanned; |
59 | |
60 | /* Number of pages freed so far during a call to shrink_zones() */ |
61 | unsigned long nr_reclaimed; |
62 | |
63 | /* How many pages shrink_list() should reclaim */ |
64 | unsigned long nr_to_reclaim; |
65 | |
66 | unsigned long hibernation_mode; |
67 | |
68 | /* This context's GFP mask */ |
69 | gfp_t gfp_mask; |
70 | |
71 | int may_writepage; |
72 | |
73 | /* Can mapped pages be reclaimed? */ |
74 | int may_unmap; |
75 | |
76 | /* Can pages be swapped as part of reclaim? */ |
77 | int may_swap; |
78 | |
79 | int order; |
80 | |
81 | /* Scan (total_size >> priority) pages at once */ |
82 | int priority; |
83 | |
84 | /* |
85 | * The memory cgroup that hit its limit and as a result is the |
86 | * primary target of this reclaim invocation. |
87 | */ |
88 | struct mem_cgroup *target_mem_cgroup; |
89 | |
90 | /* |
91 | * Nodemask of nodes allowed by the caller. If NULL, all nodes |
92 | * are scanned. |
93 | */ |
94 | nodemask_t *nodemask; |
95 | }; |
96 | |
97 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) |
98 | |
99 | #ifdef ARCH_HAS_PREFETCH |
100 | #define prefetch_prev_lru_page(_page, _base, _field) \ |
101 | do { \ |
102 | if ((_page)->lru.prev != _base) { \ |
103 | struct page *prev; \ |
104 | \ |
105 | prev = lru_to_page(&(_page->lru)); \ |
106 | prefetch(&prev->_field); \ |
107 | } \ |
108 | } while (0) |
109 | #else |
110 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) |
111 | #endif |
112 | |
113 | #ifdef ARCH_HAS_PREFETCHW |
114 | #define prefetchw_prev_lru_page(_page, _base, _field) \ |
115 | do { \ |
116 | if ((_page)->lru.prev != _base) { \ |
117 | struct page *prev; \ |
118 | \ |
119 | prev = lru_to_page(&(_page->lru)); \ |
120 | prefetchw(&prev->_field); \ |
121 | } \ |
122 | } while (0) |
123 | #else |
124 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) |
125 | #endif |
126 | |
127 | /* |
128 | * From 0 .. 100. Higher means more swappy. |
129 | */ |
130 | int vm_swappiness = 60; |
131 | long vm_total_pages; /* The total number of pages which the VM controls */ |
132 | |
133 | static LIST_HEAD(shrinker_list); |
134 | static DECLARE_RWSEM(shrinker_rwsem); |
135 | |
136 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
137 | static bool global_reclaim(struct scan_control *sc) |
138 | { |
139 | return !sc->target_mem_cgroup; |
140 | } |
141 | #else |
142 | static bool global_reclaim(struct scan_control *sc) |
143 | { |
144 | return true; |
145 | } |
146 | #endif |
147 | |
148 | static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru) |
149 | { |
150 | if (!mem_cgroup_disabled()) |
151 | return mem_cgroup_get_lru_size(lruvec, lru); |
152 | |
153 | return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru); |
154 | } |
155 | |
156 | /* |
157 | * Add a shrinker callback to be called from the vm |
158 | */ |
159 | void register_shrinker(struct shrinker *shrinker) |
160 | { |
161 | atomic_long_set(&shrinker->nr_in_batch, 0); |
162 | down_write(&shrinker_rwsem); |
163 | list_add_tail(&shrinker->list, &shrinker_list); |
164 | up_write(&shrinker_rwsem); |
165 | } |
166 | EXPORT_SYMBOL(register_shrinker); |
167 | |
168 | /* |
169 | * Remove one |
170 | */ |
171 | void unregister_shrinker(struct shrinker *shrinker) |
172 | { |
173 | down_write(&shrinker_rwsem); |
174 | list_del(&shrinker->list); |
175 | up_write(&shrinker_rwsem); |
176 | } |
177 | EXPORT_SYMBOL(unregister_shrinker); |
178 | |
179 | static inline int do_shrinker_shrink(struct shrinker *shrinker, |
180 | struct shrink_control *sc, |
181 | unsigned long nr_to_scan) |
182 | { |
183 | sc->nr_to_scan = nr_to_scan; |
184 | return (*shrinker->shrink)(shrinker, sc); |
185 | } |
186 | |
187 | #define SHRINK_BATCH 128 |
188 | /* |
189 | * Call the shrink functions to age shrinkable caches |
190 | * |
191 | * Here we assume it costs one seek to replace a lru page and that it also |
192 | * takes a seek to recreate a cache object. With this in mind we age equal |
193 | * percentages of the lru and ageable caches. This should balance the seeks |
194 | * generated by these structures. |
195 | * |
196 | * If the vm encountered mapped pages on the LRU it increase the pressure on |
197 | * slab to avoid swapping. |
198 | * |
199 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. |
200 | * |
201 | * `lru_pages' represents the number of on-LRU pages in all the zones which |
202 | * are eligible for the caller's allocation attempt. It is used for balancing |
203 | * slab reclaim versus page reclaim. |
204 | * |
205 | * Returns the number of slab objects which we shrunk. |
206 | */ |
207 | unsigned long shrink_slab(struct shrink_control *shrink, |
208 | unsigned long nr_pages_scanned, |
209 | unsigned long lru_pages) |
210 | { |
211 | struct shrinker *shrinker; |
212 | unsigned long ret = 0; |
213 | |
214 | if (nr_pages_scanned == 0) |
215 | nr_pages_scanned = SWAP_CLUSTER_MAX; |
216 | |
217 | if (!down_read_trylock(&shrinker_rwsem)) { |
218 | /* Assume we'll be able to shrink next time */ |
219 | ret = 1; |
220 | goto out; |
221 | } |
222 | |
223 | list_for_each_entry(shrinker, &shrinker_list, list) { |
224 | unsigned long long delta; |
225 | long total_scan; |
226 | long max_pass; |
227 | int shrink_ret = 0; |
228 | long nr; |
229 | long new_nr; |
230 | long batch_size = shrinker->batch ? shrinker->batch |
231 | : SHRINK_BATCH; |
232 | |
233 | max_pass = do_shrinker_shrink(shrinker, shrink, 0); |
234 | if (max_pass <= 0) |
235 | continue; |
236 | |
237 | /* |
238 | * copy the current shrinker scan count into a local variable |
239 | * and zero it so that other concurrent shrinker invocations |
240 | * don't also do this scanning work. |
241 | */ |
242 | nr = atomic_long_xchg(&shrinker->nr_in_batch, 0); |
243 | |
244 | total_scan = nr; |
245 | delta = (4 * nr_pages_scanned) / shrinker->seeks; |
246 | delta *= max_pass; |
247 | do_div(delta, lru_pages + 1); |
248 | total_scan += delta; |
249 | if (total_scan < 0) { |
250 | printk(KERN_ERR "shrink_slab: %pF negative objects to " |
251 | "delete nr=%ld\n", |
252 | shrinker->shrink, total_scan); |
253 | total_scan = max_pass; |
254 | } |
255 | |
256 | /* |
257 | * We need to avoid excessive windup on filesystem shrinkers |
258 | * due to large numbers of GFP_NOFS allocations causing the |
259 | * shrinkers to return -1 all the time. This results in a large |
260 | * nr being built up so when a shrink that can do some work |
261 | * comes along it empties the entire cache due to nr >>> |
262 | * max_pass. This is bad for sustaining a working set in |
263 | * memory. |
264 | * |
265 | * Hence only allow the shrinker to scan the entire cache when |
266 | * a large delta change is calculated directly. |
267 | */ |
268 | if (delta < max_pass / 4) |
269 | total_scan = min(total_scan, max_pass / 2); |
270 | |
271 | /* |
272 | * Avoid risking looping forever due to too large nr value: |
273 | * never try to free more than twice the estimate number of |
274 | * freeable entries. |
275 | */ |
276 | if (total_scan > max_pass * 2) |
277 | total_scan = max_pass * 2; |
278 | |
279 | trace_mm_shrink_slab_start(shrinker, shrink, nr, |
280 | nr_pages_scanned, lru_pages, |
281 | max_pass, delta, total_scan); |
282 | |
283 | while (total_scan >= batch_size) { |
284 | int nr_before; |
285 | |
286 | nr_before = do_shrinker_shrink(shrinker, shrink, 0); |
287 | shrink_ret = do_shrinker_shrink(shrinker, shrink, |
288 | batch_size); |
289 | if (shrink_ret == -1) |
290 | break; |
291 | if (shrink_ret < nr_before) |
292 | ret += nr_before - shrink_ret; |
293 | count_vm_events(SLABS_SCANNED, batch_size); |
294 | total_scan -= batch_size; |
295 | |
296 | cond_resched(); |
297 | } |
298 | |
299 | /* |
300 | * move the unused scan count back into the shrinker in a |
301 | * manner that handles concurrent updates. If we exhausted the |
302 | * scan, there is no need to do an update. |
303 | */ |
304 | if (total_scan > 0) |
305 | new_nr = atomic_long_add_return(total_scan, |
306 | &shrinker->nr_in_batch); |
307 | else |
308 | new_nr = atomic_long_read(&shrinker->nr_in_batch); |
309 | |
310 | trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr); |
311 | } |
312 | up_read(&shrinker_rwsem); |
313 | out: |
314 | cond_resched(); |
315 | return ret; |
316 | } |
317 | |
318 | static inline int is_page_cache_freeable(struct page *page) |
319 | { |
320 | /* |
321 | * A freeable page cache page is referenced only by the caller |
322 | * that isolated the page, the page cache radix tree and |
323 | * optional buffer heads at page->private. |
324 | */ |
325 | return page_count(page) - page_has_private(page) == 2; |
326 | } |
327 | |
328 | static int may_write_to_queue(struct backing_dev_info *bdi, |
329 | struct scan_control *sc) |
330 | { |
331 | if (current->flags & PF_SWAPWRITE) |
332 | return 1; |
333 | if (!bdi_write_congested(bdi)) |
334 | return 1; |
335 | if (bdi == current->backing_dev_info) |
336 | return 1; |
337 | return 0; |
338 | } |
339 | |
340 | /* |
341 | * We detected a synchronous write error writing a page out. Probably |
342 | * -ENOSPC. We need to propagate that into the address_space for a subsequent |
343 | * fsync(), msync() or close(). |
344 | * |
345 | * The tricky part is that after writepage we cannot touch the mapping: nothing |
346 | * prevents it from being freed up. But we have a ref on the page and once |
347 | * that page is locked, the mapping is pinned. |
348 | * |
349 | * We're allowed to run sleeping lock_page() here because we know the caller has |
350 | * __GFP_FS. |
351 | */ |
352 | static void handle_write_error(struct address_space *mapping, |
353 | struct page *page, int error) |
354 | { |
355 | lock_page(page); |
356 | if (page_mapping(page) == mapping) |
357 | mapping_set_error(mapping, error); |
358 | unlock_page(page); |
359 | } |
360 | |
361 | /* possible outcome of pageout() */ |
362 | typedef enum { |
363 | /* failed to write page out, page is locked */ |
364 | PAGE_KEEP, |
365 | /* move page to the active list, page is locked */ |
366 | PAGE_ACTIVATE, |
367 | /* page has been sent to the disk successfully, page is unlocked */ |
368 | PAGE_SUCCESS, |
369 | /* page is clean and locked */ |
370 | PAGE_CLEAN, |
371 | } pageout_t; |
372 | |
373 | /* |
374 | * pageout is called by shrink_page_list() for each dirty page. |
375 | * Calls ->writepage(). |
376 | */ |
377 | static pageout_t pageout(struct page *page, struct address_space *mapping, |
378 | struct scan_control *sc) |
379 | { |
380 | /* |
381 | * If the page is dirty, only perform writeback if that write |
382 | * will be non-blocking. To prevent this allocation from being |
383 | * stalled by pagecache activity. But note that there may be |
384 | * stalls if we need to run get_block(). We could test |
385 | * PagePrivate for that. |
386 | * |
387 | * If this process is currently in __generic_file_aio_write() against |
388 | * this page's queue, we can perform writeback even if that |
389 | * will block. |
390 | * |
391 | * If the page is swapcache, write it back even if that would |
392 | * block, for some throttling. This happens by accident, because |
393 | * swap_backing_dev_info is bust: it doesn't reflect the |
394 | * congestion state of the swapdevs. Easy to fix, if needed. |
395 | */ |
396 | if (!is_page_cache_freeable(page)) |
397 | return PAGE_KEEP; |
398 | if (!mapping) { |
399 | /* |
400 | * Some data journaling orphaned pages can have |
401 | * page->mapping == NULL while being dirty with clean buffers. |
402 | */ |
403 | if (page_has_private(page)) { |
404 | if (try_to_free_buffers(page)) { |
405 | ClearPageDirty(page); |
406 | printk("%s: orphaned page\n", __func__); |
407 | return PAGE_CLEAN; |
408 | } |
409 | } |
410 | return PAGE_KEEP; |
411 | } |
412 | if (mapping->a_ops->writepage == NULL) |
413 | return PAGE_ACTIVATE; |
414 | if (!may_write_to_queue(mapping->backing_dev_info, sc)) |
415 | return PAGE_KEEP; |
416 | |
417 | if (clear_page_dirty_for_io(page)) { |
418 | int res; |
419 | struct writeback_control wbc = { |
420 | .sync_mode = WB_SYNC_NONE, |
421 | .nr_to_write = SWAP_CLUSTER_MAX, |
422 | .range_start = 0, |
423 | .range_end = LLONG_MAX, |
424 | .for_reclaim = 1, |
425 | }; |
426 | |
427 | SetPageReclaim(page); |
428 | res = mapping->a_ops->writepage(page, &wbc); |
429 | if (res < 0) |
430 | handle_write_error(mapping, page, res); |
431 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
432 | ClearPageReclaim(page); |
433 | return PAGE_ACTIVATE; |
434 | } |
435 | |
436 | if (!PageWriteback(page)) { |
437 | /* synchronous write or broken a_ops? */ |
438 | ClearPageReclaim(page); |
439 | } |
440 | trace_mm_vmscan_writepage(page, trace_reclaim_flags(page)); |
441 | inc_zone_page_state(page, NR_VMSCAN_WRITE); |
442 | return PAGE_SUCCESS; |
443 | } |
444 | |
445 | return PAGE_CLEAN; |
446 | } |
447 | |
448 | /* |
449 | * Same as remove_mapping, but if the page is removed from the mapping, it |
450 | * gets returned with a refcount of 0. |
451 | */ |
452 | static int __remove_mapping(struct address_space *mapping, struct page *page) |
453 | { |
454 | BUG_ON(!PageLocked(page)); |
455 | BUG_ON(mapping != page_mapping(page)); |
456 | |
457 | spin_lock_irq(&mapping->tree_lock); |
458 | /* |
459 | * The non racy check for a busy page. |
460 | * |
461 | * Must be careful with the order of the tests. When someone has |
462 | * a ref to the page, it may be possible that they dirty it then |
463 | * drop the reference. So if PageDirty is tested before page_count |
464 | * here, then the following race may occur: |
465 | * |
466 | * get_user_pages(&page); |
467 | * [user mapping goes away] |
468 | * write_to(page); |
469 | * !PageDirty(page) [good] |
470 | * SetPageDirty(page); |
471 | * put_page(page); |
472 | * !page_count(page) [good, discard it] |
473 | * |
474 | * [oops, our write_to data is lost] |
475 | * |
476 | * Reversing the order of the tests ensures such a situation cannot |
477 | * escape unnoticed. The smp_rmb is needed to ensure the page->flags |
478 | * load is not satisfied before that of page->_count. |
479 | * |
480 | * Note that if SetPageDirty is always performed via set_page_dirty, |
481 | * and thus under tree_lock, then this ordering is not required. |
482 | */ |
483 | if (!page_freeze_refs(page, 2)) |
484 | goto cannot_free; |
485 | /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ |
486 | if (unlikely(PageDirty(page))) { |
487 | page_unfreeze_refs(page, 2); |
488 | goto cannot_free; |
489 | } |
490 | |
491 | if (PageSwapCache(page)) { |
492 | swp_entry_t swap = { .val = page_private(page) }; |
493 | __delete_from_swap_cache(page); |
494 | spin_unlock_irq(&mapping->tree_lock); |
495 | swapcache_free(swap, page); |
496 | } else { |
497 | void (*freepage)(struct page *); |
498 | |
499 | freepage = mapping->a_ops->freepage; |
500 | |
501 | __delete_from_page_cache(page); |
502 | spin_unlock_irq(&mapping->tree_lock); |
503 | mem_cgroup_uncharge_cache_page(page); |
504 | |
505 | if (freepage != NULL) |
506 | freepage(page); |
507 | } |
508 | |
509 | return 1; |
510 | |
511 | cannot_free: |
512 | spin_unlock_irq(&mapping->tree_lock); |
513 | return 0; |
514 | } |
515 | |
516 | /* |
517 | * Attempt to detach a locked page from its ->mapping. If it is dirty or if |
518 | * someone else has a ref on the page, abort and return 0. If it was |
519 | * successfully detached, return 1. Assumes the caller has a single ref on |
520 | * this page. |
521 | */ |
522 | int remove_mapping(struct address_space *mapping, struct page *page) |
523 | { |
524 | if (__remove_mapping(mapping, page)) { |
525 | /* |
526 | * Unfreezing the refcount with 1 rather than 2 effectively |
527 | * drops the pagecache ref for us without requiring another |
528 | * atomic operation. |
529 | */ |
530 | page_unfreeze_refs(page, 1); |
531 | return 1; |
532 | } |
533 | return 0; |
534 | } |
535 | |
536 | /** |
537 | * putback_lru_page - put previously isolated page onto appropriate LRU list |
538 | * @page: page to be put back to appropriate lru list |
539 | * |
540 | * Add previously isolated @page to appropriate LRU list. |
541 | * Page may still be unevictable for other reasons. |
542 | * |
543 | * lru_lock must not be held, interrupts must be enabled. |
544 | */ |
545 | void putback_lru_page(struct page *page) |
546 | { |
547 | int lru; |
548 | int active = !!TestClearPageActive(page); |
549 | int was_unevictable = PageUnevictable(page); |
550 | |
551 | VM_BUG_ON(PageLRU(page)); |
552 | |
553 | redo: |
554 | ClearPageUnevictable(page); |
555 | |
556 | if (page_evictable(page, NULL)) { |
557 | /* |
558 | * For evictable pages, we can use the cache. |
559 | * In event of a race, worst case is we end up with an |
560 | * unevictable page on [in]active list. |
561 | * We know how to handle that. |
562 | */ |
563 | lru = active + page_lru_base_type(page); |
564 | lru_cache_add_lru(page, lru); |
565 | } else { |
566 | /* |
567 | * Put unevictable pages directly on zone's unevictable |
568 | * list. |
569 | */ |
570 | lru = LRU_UNEVICTABLE; |
571 | add_page_to_unevictable_list(page); |
572 | /* |
573 | * When racing with an mlock or AS_UNEVICTABLE clearing |
574 | * (page is unlocked) make sure that if the other thread |
575 | * does not observe our setting of PG_lru and fails |
576 | * isolation/check_move_unevictable_pages, |
577 | * we see PG_mlocked/AS_UNEVICTABLE cleared below and move |
578 | * the page back to the evictable list. |
579 | * |
580 | * The other side is TestClearPageMlocked() or shmem_lock(). |
581 | */ |
582 | smp_mb(); |
583 | } |
584 | |
585 | /* |
586 | * page's status can change while we move it among lru. If an evictable |
587 | * page is on unevictable list, it never be freed. To avoid that, |
588 | * check after we added it to the list, again. |
589 | */ |
590 | if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { |
591 | if (!isolate_lru_page(page)) { |
592 | put_page(page); |
593 | goto redo; |
594 | } |
595 | /* This means someone else dropped this page from LRU |
596 | * So, it will be freed or putback to LRU again. There is |
597 | * nothing to do here. |
598 | */ |
599 | } |
600 | |
601 | if (was_unevictable && lru != LRU_UNEVICTABLE) |
602 | count_vm_event(UNEVICTABLE_PGRESCUED); |
603 | else if (!was_unevictable && lru == LRU_UNEVICTABLE) |
604 | count_vm_event(UNEVICTABLE_PGCULLED); |
605 | |
606 | put_page(page); /* drop ref from isolate */ |
607 | } |
608 | |
609 | enum page_references { |
610 | PAGEREF_RECLAIM, |
611 | PAGEREF_RECLAIM_CLEAN, |
612 | PAGEREF_KEEP, |
613 | PAGEREF_ACTIVATE, |
614 | }; |
615 | |
616 | static enum page_references page_check_references(struct page *page, |
617 | struct scan_control *sc) |
618 | { |
619 | int referenced_ptes, referenced_page; |
620 | unsigned long vm_flags; |
621 | |
622 | referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup, |
623 | &vm_flags); |
624 | referenced_page = TestClearPageReferenced(page); |
625 | |
626 | /* |
627 | * Mlock lost the isolation race with us. Let try_to_unmap() |
628 | * move the page to the unevictable list. |
629 | */ |
630 | if (vm_flags & VM_LOCKED) |
631 | return PAGEREF_RECLAIM; |
632 | |
633 | if (referenced_ptes) { |
634 | if (PageSwapBacked(page)) |
635 | return PAGEREF_ACTIVATE; |
636 | /* |
637 | * All mapped pages start out with page table |
638 | * references from the instantiating fault, so we need |
639 | * to look twice if a mapped file page is used more |
640 | * than once. |
641 | * |
642 | * Mark it and spare it for another trip around the |
643 | * inactive list. Another page table reference will |
644 | * lead to its activation. |
645 | * |
646 | * Note: the mark is set for activated pages as well |
647 | * so that recently deactivated but used pages are |
648 | * quickly recovered. |
649 | */ |
650 | SetPageReferenced(page); |
651 | |
652 | if (referenced_page || referenced_ptes > 1) |
653 | return PAGEREF_ACTIVATE; |
654 | |
655 | /* |
656 | * Activate file-backed executable pages after first usage. |
657 | */ |
658 | if (vm_flags & VM_EXEC) |
659 | return PAGEREF_ACTIVATE; |
660 | |
661 | return PAGEREF_KEEP; |
662 | } |
663 | |
664 | /* Reclaim if clean, defer dirty pages to writeback */ |
665 | if (referenced_page && !PageSwapBacked(page)) |
666 | return PAGEREF_RECLAIM_CLEAN; |
667 | |
668 | return PAGEREF_RECLAIM; |
669 | } |
670 | |
671 | /* |
672 | * shrink_page_list() returns the number of reclaimed pages |
673 | */ |
674 | static unsigned long shrink_page_list(struct list_head *page_list, |
675 | struct zone *zone, |
676 | struct scan_control *sc, |
677 | unsigned long *ret_nr_dirty, |
678 | unsigned long *ret_nr_writeback) |
679 | { |
680 | LIST_HEAD(ret_pages); |
681 | LIST_HEAD(free_pages); |
682 | int pgactivate = 0; |
683 | unsigned long nr_dirty = 0; |
684 | unsigned long nr_congested = 0; |
685 | unsigned long nr_reclaimed = 0; |
686 | unsigned long nr_writeback = 0; |
687 | |
688 | cond_resched(); |
689 | |
690 | while (!list_empty(page_list)) { |
691 | enum page_references references; |
692 | struct address_space *mapping; |
693 | struct page *page; |
694 | int may_enter_fs; |
695 | |
696 | cond_resched(); |
697 | |
698 | page = lru_to_page(page_list); |
699 | list_del(&page->lru); |
700 | |
701 | if (!trylock_page(page)) |
702 | goto keep; |
703 | |
704 | VM_BUG_ON(PageActive(page)); |
705 | VM_BUG_ON(page_zone(page) != zone); |
706 | |
707 | sc->nr_scanned++; |
708 | |
709 | if (unlikely(!page_evictable(page, NULL))) |
710 | goto cull_mlocked; |
711 | |
712 | if (!sc->may_unmap && page_mapped(page)) |
713 | goto keep_locked; |
714 | |
715 | /* Double the slab pressure for mapped and swapcache pages */ |
716 | if (page_mapped(page) || PageSwapCache(page)) |
717 | sc->nr_scanned++; |
718 | |
719 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || |
720 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); |
721 | |
722 | if (PageWriteback(page)) { |
723 | nr_writeback++; |
724 | unlock_page(page); |
725 | goto keep; |
726 | } |
727 | |
728 | references = page_check_references(page, sc); |
729 | switch (references) { |
730 | case PAGEREF_ACTIVATE: |
731 | goto activate_locked; |
732 | case PAGEREF_KEEP: |
733 | goto keep_locked; |
734 | case PAGEREF_RECLAIM: |
735 | case PAGEREF_RECLAIM_CLEAN: |
736 | ; /* try to reclaim the page below */ |
737 | } |
738 | |
739 | /* |
740 | * Anonymous process memory has backing store? |
741 | * Try to allocate it some swap space here. |
742 | */ |
743 | if (PageAnon(page) && !PageSwapCache(page)) { |
744 | if (!(sc->gfp_mask & __GFP_IO)) |
745 | goto keep_locked; |
746 | if (!add_to_swap(page)) |
747 | goto activate_locked; |
748 | may_enter_fs = 1; |
749 | } |
750 | |
751 | mapping = page_mapping(page); |
752 | |
753 | /* |
754 | * The page is mapped into the page tables of one or more |
755 | * processes. Try to unmap it here. |
756 | */ |
757 | if (page_mapped(page) && mapping) { |
758 | switch (try_to_unmap(page, TTU_UNMAP)) { |
759 | case SWAP_FAIL: |
760 | goto activate_locked; |
761 | case SWAP_AGAIN: |
762 | goto keep_locked; |
763 | case SWAP_MLOCK: |
764 | goto cull_mlocked; |
765 | case SWAP_SUCCESS: |
766 | ; /* try to free the page below */ |
767 | } |
768 | } |
769 | |
770 | if (PageDirty(page)) { |
771 | nr_dirty++; |
772 | |
773 | /* |
774 | * Only kswapd can writeback filesystem pages to |
775 | * avoid risk of stack overflow but do not writeback |
776 | * unless under significant pressure. |
777 | */ |
778 | if (page_is_file_cache(page) && |
779 | (!current_is_kswapd() || |
780 | sc->priority >= DEF_PRIORITY - 2)) { |
781 | /* |
782 | * Immediately reclaim when written back. |
783 | * Similar in principal to deactivate_page() |
784 | * except we already have the page isolated |
785 | * and know it's dirty |
786 | */ |
787 | inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE); |
788 | SetPageReclaim(page); |
789 | |
790 | goto keep_locked; |
791 | } |
792 | |
793 | if (references == PAGEREF_RECLAIM_CLEAN) |
794 | goto keep_locked; |
795 | if (!may_enter_fs) |
796 | goto keep_locked; |
797 | if (!sc->may_writepage) |
798 | goto keep_locked; |
799 | |
800 | /* Page is dirty, try to write it out here */ |
801 | switch (pageout(page, mapping, sc)) { |
802 | case PAGE_KEEP: |
803 | nr_congested++; |
804 | goto keep_locked; |
805 | case PAGE_ACTIVATE: |
806 | goto activate_locked; |
807 | case PAGE_SUCCESS: |
808 | if (PageWriteback(page)) |
809 | goto keep; |
810 | if (PageDirty(page)) |
811 | goto keep; |
812 | |
813 | /* |
814 | * A synchronous write - probably a ramdisk. Go |
815 | * ahead and try to reclaim the page. |
816 | */ |
817 | if (!trylock_page(page)) |
818 | goto keep; |
819 | if (PageDirty(page) || PageWriteback(page)) |
820 | goto keep_locked; |
821 | mapping = page_mapping(page); |
822 | case PAGE_CLEAN: |
823 | ; /* try to free the page below */ |
824 | } |
825 | } |
826 | |
827 | /* |
828 | * If the page has buffers, try to free the buffer mappings |
829 | * associated with this page. If we succeed we try to free |
830 | * the page as well. |
831 | * |
832 | * We do this even if the page is PageDirty(). |
833 | * try_to_release_page() does not perform I/O, but it is |
834 | * possible for a page to have PageDirty set, but it is actually |
835 | * clean (all its buffers are clean). This happens if the |
836 | * buffers were written out directly, with submit_bh(). ext3 |
837 | * will do this, as well as the blockdev mapping. |
838 | * try_to_release_page() will discover that cleanness and will |
839 | * drop the buffers and mark the page clean - it can be freed. |
840 | * |
841 | * Rarely, pages can have buffers and no ->mapping. These are |
842 | * the pages which were not successfully invalidated in |
843 | * truncate_complete_page(). We try to drop those buffers here |
844 | * and if that worked, and the page is no longer mapped into |
845 | * process address space (page_count == 1) it can be freed. |
846 | * Otherwise, leave the page on the LRU so it is swappable. |
847 | */ |
848 | if (page_has_private(page)) { |
849 | if (!try_to_release_page(page, sc->gfp_mask)) |
850 | goto activate_locked; |
851 | if (!mapping && page_count(page) == 1) { |
852 | unlock_page(page); |
853 | if (put_page_testzero(page)) |
854 | goto free_it; |
855 | else { |
856 | /* |
857 | * rare race with speculative reference. |
858 | * the speculative reference will free |
859 | * this page shortly, so we may |
860 | * increment nr_reclaimed here (and |
861 | * leave it off the LRU). |
862 | */ |
863 | nr_reclaimed++; |
864 | continue; |
865 | } |
866 | } |
867 | } |
868 | |
869 | if (!mapping || !__remove_mapping(mapping, page)) |
870 | goto keep_locked; |
871 | |
872 | /* |
873 | * At this point, we have no other references and there is |
874 | * no way to pick any more up (removed from LRU, removed |
875 | * from pagecache). Can use non-atomic bitops now (and |
876 | * we obviously don't have to worry about waking up a process |
877 | * waiting on the page lock, because there are no references. |
878 | */ |
879 | __clear_page_locked(page); |
880 | free_it: |
881 | nr_reclaimed++; |
882 | |
883 | /* |
884 | * Is there need to periodically free_page_list? It would |
885 | * appear not as the counts should be low |
886 | */ |
887 | list_add(&page->lru, &free_pages); |
888 | continue; |
889 | |
890 | cull_mlocked: |
891 | if (PageSwapCache(page)) |
892 | try_to_free_swap(page); |
893 | unlock_page(page); |
894 | putback_lru_page(page); |
895 | continue; |
896 | |
897 | activate_locked: |
898 | /* Not a candidate for swapping, so reclaim swap space. */ |
899 | if (PageSwapCache(page) && vm_swap_full()) |
900 | try_to_free_swap(page); |
901 | VM_BUG_ON(PageActive(page)); |
902 | SetPageActive(page); |
903 | pgactivate++; |
904 | keep_locked: |
905 | unlock_page(page); |
906 | keep: |
907 | list_add(&page->lru, &ret_pages); |
908 | VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); |
909 | } |
910 | |
911 | /* |
912 | * Tag a zone as congested if all the dirty pages encountered were |
913 | * backed by a congested BDI. In this case, reclaimers should just |
914 | * back off and wait for congestion to clear because further reclaim |
915 | * will encounter the same problem |
916 | */ |
917 | if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc)) |
918 | zone_set_flag(zone, ZONE_CONGESTED); |
919 | |
920 | free_hot_cold_page_list(&free_pages, 1); |
921 | |
922 | list_splice(&ret_pages, page_list); |
923 | count_vm_events(PGACTIVATE, pgactivate); |
924 | *ret_nr_dirty += nr_dirty; |
925 | *ret_nr_writeback += nr_writeback; |
926 | return nr_reclaimed; |
927 | } |
928 | |
929 | /* |
930 | * Attempt to remove the specified page from its LRU. Only take this page |
931 | * if it is of the appropriate PageActive status. Pages which are being |
932 | * freed elsewhere are also ignored. |
933 | * |
934 | * page: page to consider |
935 | * mode: one of the LRU isolation modes defined above |
936 | * |
937 | * returns 0 on success, -ve errno on failure. |
938 | */ |
939 | int __isolate_lru_page(struct page *page, isolate_mode_t mode) |
940 | { |
941 | int ret = -EINVAL; |
942 | |
943 | /* Only take pages on the LRU. */ |
944 | if (!PageLRU(page)) |
945 | return ret; |
946 | |
947 | /* Do not give back unevictable pages for compaction */ |
948 | if (PageUnevictable(page)) |
949 | return ret; |
950 | |
951 | ret = -EBUSY; |
952 | |
953 | /* |
954 | * To minimise LRU disruption, the caller can indicate that it only |
955 | * wants to isolate pages it will be able to operate on without |
956 | * blocking - clean pages for the most part. |
957 | * |
958 | * ISOLATE_CLEAN means that only clean pages should be isolated. This |
959 | * is used by reclaim when it is cannot write to backing storage |
960 | * |
961 | * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages |
962 | * that it is possible to migrate without blocking |
963 | */ |
964 | if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) { |
965 | /* All the caller can do on PageWriteback is block */ |
966 | if (PageWriteback(page)) |
967 | return ret; |
968 | |
969 | if (PageDirty(page)) { |
970 | struct address_space *mapping; |
971 | |
972 | /* ISOLATE_CLEAN means only clean pages */ |
973 | if (mode & ISOLATE_CLEAN) |
974 | return ret; |
975 | |
976 | /* |
977 | * Only pages without mappings or that have a |
978 | * ->migratepage callback are possible to migrate |
979 | * without blocking |
980 | */ |
981 | mapping = page_mapping(page); |
982 | if (mapping && !mapping->a_ops->migratepage) |
983 | return ret; |
984 | } |
985 | } |
986 | |
987 | if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) |
988 | return ret; |
989 | |
990 | if (likely(get_page_unless_zero(page))) { |
991 | /* |
992 | * Be careful not to clear PageLRU until after we're |
993 | * sure the page is not being freed elsewhere -- the |
994 | * page release code relies on it. |
995 | */ |
996 | ClearPageLRU(page); |
997 | ret = 0; |
998 | } |
999 | |
1000 | return ret; |
1001 | } |
1002 | |
1003 | /* |
1004 | * zone->lru_lock is heavily contended. Some of the functions that |
1005 | * shrink the lists perform better by taking out a batch of pages |
1006 | * and working on them outside the LRU lock. |
1007 | * |
1008 | * For pagecache intensive workloads, this function is the hottest |
1009 | * spot in the kernel (apart from copy_*_user functions). |
1010 | * |
1011 | * Appropriate locks must be held before calling this function. |
1012 | * |
1013 | * @nr_to_scan: The number of pages to look through on the list. |
1014 | * @lruvec: The LRU vector to pull pages from. |
1015 | * @dst: The temp list to put pages on to. |
1016 | * @nr_scanned: The number of pages that were scanned. |
1017 | * @sc: The scan_control struct for this reclaim session |
1018 | * @mode: One of the LRU isolation modes |
1019 | * @lru: LRU list id for isolating |
1020 | * |
1021 | * returns how many pages were moved onto *@dst. |
1022 | */ |
1023 | static unsigned long isolate_lru_pages(unsigned long nr_to_scan, |
1024 | struct lruvec *lruvec, struct list_head *dst, |
1025 | unsigned long *nr_scanned, struct scan_control *sc, |
1026 | isolate_mode_t mode, enum lru_list lru) |
1027 | { |
1028 | struct list_head *src = &lruvec->lists[lru]; |
1029 | unsigned long nr_taken = 0; |
1030 | unsigned long scan; |
1031 | |
1032 | for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { |
1033 | struct page *page; |
1034 | int nr_pages; |
1035 | |
1036 | page = lru_to_page(src); |
1037 | prefetchw_prev_lru_page(page, src, flags); |
1038 | |
1039 | VM_BUG_ON(!PageLRU(page)); |
1040 | |
1041 | switch (__isolate_lru_page(page, mode)) { |
1042 | case 0: |
1043 | nr_pages = hpage_nr_pages(page); |
1044 | mem_cgroup_update_lru_size(lruvec, lru, -nr_pages); |
1045 | list_move(&page->lru, dst); |
1046 | nr_taken += nr_pages; |
1047 | break; |
1048 | |
1049 | case -EBUSY: |
1050 | /* else it is being freed elsewhere */ |
1051 | list_move(&page->lru, src); |
1052 | continue; |
1053 | |
1054 | default: |
1055 | BUG(); |
1056 | } |
1057 | } |
1058 | |
1059 | *nr_scanned = scan; |
1060 | trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan, |
1061 | nr_taken, mode, is_file_lru(lru)); |
1062 | return nr_taken; |
1063 | } |
1064 | |
1065 | /** |
1066 | * isolate_lru_page - tries to isolate a page from its LRU list |
1067 | * @page: page to isolate from its LRU list |
1068 | * |
1069 | * Isolates a @page from an LRU list, clears PageLRU and adjusts the |
1070 | * vmstat statistic corresponding to whatever LRU list the page was on. |
1071 | * |
1072 | * Returns 0 if the page was removed from an LRU list. |
1073 | * Returns -EBUSY if the page was not on an LRU list. |
1074 | * |
1075 | * The returned page will have PageLRU() cleared. If it was found on |
1076 | * the active list, it will have PageActive set. If it was found on |
1077 | * the unevictable list, it will have the PageUnevictable bit set. That flag |
1078 | * may need to be cleared by the caller before letting the page go. |
1079 | * |
1080 | * The vmstat statistic corresponding to the list on which the page was |
1081 | * found will be decremented. |
1082 | * |
1083 | * Restrictions: |
1084 | * (1) Must be called with an elevated refcount on the page. This is a |
1085 | * fundamentnal difference from isolate_lru_pages (which is called |
1086 | * without a stable reference). |
1087 | * (2) the lru_lock must not be held. |
1088 | * (3) interrupts must be enabled. |
1089 | */ |
1090 | int isolate_lru_page(struct page *page) |
1091 | { |
1092 | int ret = -EBUSY; |
1093 | |
1094 | VM_BUG_ON(!page_count(page)); |
1095 | |
1096 | if (PageLRU(page)) { |
1097 | struct zone *zone = page_zone(page); |
1098 | struct lruvec *lruvec; |
1099 | |
1100 | spin_lock_irq(&zone->lru_lock); |
1101 | lruvec = mem_cgroup_page_lruvec(page, zone); |
1102 | if (PageLRU(page)) { |
1103 | int lru = page_lru(page); |
1104 | get_page(page); |
1105 | ClearPageLRU(page); |
1106 | del_page_from_lru_list(page, lruvec, lru); |
1107 | ret = 0; |
1108 | } |
1109 | spin_unlock_irq(&zone->lru_lock); |
1110 | } |
1111 | return ret; |
1112 | } |
1113 | |
1114 | /* |
1115 | * Are there way too many processes in the direct reclaim path already? |
1116 | */ |
1117 | static int too_many_isolated(struct zone *zone, int file, |
1118 | struct scan_control *sc) |
1119 | { |
1120 | unsigned long inactive, isolated; |
1121 | |
1122 | if (current_is_kswapd()) |
1123 | return 0; |
1124 | |
1125 | if (!global_reclaim(sc)) |
1126 | return 0; |
1127 | |
1128 | if (file) { |
1129 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); |
1130 | isolated = zone_page_state(zone, NR_ISOLATED_FILE); |
1131 | } else { |
1132 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
1133 | isolated = zone_page_state(zone, NR_ISOLATED_ANON); |
1134 | } |
1135 | |
1136 | return isolated > inactive; |
1137 | } |
1138 | |
1139 | static noinline_for_stack void |
1140 | putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list) |
1141 | { |
1142 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
1143 | struct zone *zone = lruvec_zone(lruvec); |
1144 | LIST_HEAD(pages_to_free); |
1145 | |
1146 | /* |
1147 | * Put back any unfreeable pages. |
1148 | */ |
1149 | while (!list_empty(page_list)) { |
1150 | struct page *page = lru_to_page(page_list); |
1151 | int lru; |
1152 | |
1153 | VM_BUG_ON(PageLRU(page)); |
1154 | list_del(&page->lru); |
1155 | if (unlikely(!page_evictable(page, NULL))) { |
1156 | spin_unlock_irq(&zone->lru_lock); |
1157 | putback_lru_page(page); |
1158 | spin_lock_irq(&zone->lru_lock); |
1159 | continue; |
1160 | } |
1161 | |
1162 | lruvec = mem_cgroup_page_lruvec(page, zone); |
1163 | |
1164 | SetPageLRU(page); |
1165 | lru = page_lru(page); |
1166 | add_page_to_lru_list(page, lruvec, lru); |
1167 | |
1168 | if (is_active_lru(lru)) { |
1169 | int file = is_file_lru(lru); |
1170 | int numpages = hpage_nr_pages(page); |
1171 | reclaim_stat->recent_rotated[file] += numpages; |
1172 | } |
1173 | if (put_page_testzero(page)) { |
1174 | __ClearPageLRU(page); |
1175 | __ClearPageActive(page); |
1176 | del_page_from_lru_list(page, lruvec, lru); |
1177 | |
1178 | if (unlikely(PageCompound(page))) { |
1179 | spin_unlock_irq(&zone->lru_lock); |
1180 | (*get_compound_page_dtor(page))(page); |
1181 | spin_lock_irq(&zone->lru_lock); |
1182 | } else |
1183 | list_add(&page->lru, &pages_to_free); |
1184 | } |
1185 | } |
1186 | |
1187 | /* |
1188 | * To save our caller's stack, now use input list for pages to free. |
1189 | */ |
1190 | list_splice(&pages_to_free, page_list); |
1191 | } |
1192 | |
1193 | /* |
1194 | * shrink_inactive_list() is a helper for shrink_zone(). It returns the number |
1195 | * of reclaimed pages |
1196 | */ |
1197 | static noinline_for_stack unsigned long |
1198 | shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, |
1199 | struct scan_control *sc, enum lru_list lru) |
1200 | { |
1201 | LIST_HEAD(page_list); |
1202 | unsigned long nr_scanned; |
1203 | unsigned long nr_reclaimed = 0; |
1204 | unsigned long nr_taken; |
1205 | unsigned long nr_dirty = 0; |
1206 | unsigned long nr_writeback = 0; |
1207 | isolate_mode_t isolate_mode = 0; |
1208 | int file = is_file_lru(lru); |
1209 | struct zone *zone = lruvec_zone(lruvec); |
1210 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
1211 | |
1212 | while (unlikely(too_many_isolated(zone, file, sc))) { |
1213 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
1214 | |
1215 | /* We are about to die and free our memory. Return now. */ |
1216 | if (fatal_signal_pending(current)) |
1217 | return SWAP_CLUSTER_MAX; |
1218 | } |
1219 | |
1220 | lru_add_drain(); |
1221 | |
1222 | if (!sc->may_unmap) |
1223 | isolate_mode |= ISOLATE_UNMAPPED; |
1224 | if (!sc->may_writepage) |
1225 | isolate_mode |= ISOLATE_CLEAN; |
1226 | |
1227 | spin_lock_irq(&zone->lru_lock); |
1228 | |
1229 | nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list, |
1230 | &nr_scanned, sc, isolate_mode, lru); |
1231 | |
1232 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken); |
1233 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); |
1234 | |
1235 | if (global_reclaim(sc)) { |
1236 | zone->pages_scanned += nr_scanned; |
1237 | if (current_is_kswapd()) |
1238 | __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned); |
1239 | else |
1240 | __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned); |
1241 | } |
1242 | spin_unlock_irq(&zone->lru_lock); |
1243 | |
1244 | if (nr_taken == 0) |
1245 | return 0; |
1246 | |
1247 | nr_reclaimed = shrink_page_list(&page_list, zone, sc, |
1248 | &nr_dirty, &nr_writeback); |
1249 | |
1250 | spin_lock_irq(&zone->lru_lock); |
1251 | |
1252 | reclaim_stat->recent_scanned[file] += nr_taken; |
1253 | |
1254 | if (global_reclaim(sc)) { |
1255 | if (current_is_kswapd()) |
1256 | __count_zone_vm_events(PGSTEAL_KSWAPD, zone, |
1257 | nr_reclaimed); |
1258 | else |
1259 | __count_zone_vm_events(PGSTEAL_DIRECT, zone, |
1260 | nr_reclaimed); |
1261 | } |
1262 | |
1263 | putback_inactive_pages(lruvec, &page_list); |
1264 | |
1265 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); |
1266 | |
1267 | spin_unlock_irq(&zone->lru_lock); |
1268 | |
1269 | free_hot_cold_page_list(&page_list, 1); |
1270 | |
1271 | /* |
1272 | * If reclaim is isolating dirty pages under writeback, it implies |
1273 | * that the long-lived page allocation rate is exceeding the page |
1274 | * laundering rate. Either the global limits are not being effective |
1275 | * at throttling processes due to the page distribution throughout |
1276 | * zones or there is heavy usage of a slow backing device. The |
1277 | * only option is to throttle from reclaim context which is not ideal |
1278 | * as there is no guarantee the dirtying process is throttled in the |
1279 | * same way balance_dirty_pages() manages. |
1280 | * |
1281 | * This scales the number of dirty pages that must be under writeback |
1282 | * before throttling depending on priority. It is a simple backoff |
1283 | * function that has the most effect in the range DEF_PRIORITY to |
1284 | * DEF_PRIORITY-2 which is the priority reclaim is considered to be |
1285 | * in trouble and reclaim is considered to be in trouble. |
1286 | * |
1287 | * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle |
1288 | * DEF_PRIORITY-1 50% must be PageWriteback |
1289 | * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble |
1290 | * ... |
1291 | * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any |
1292 | * isolated page is PageWriteback |
1293 | */ |
1294 | if (nr_writeback && nr_writeback >= |
1295 | (nr_taken >> (DEF_PRIORITY - sc->priority))) |
1296 | wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10); |
1297 | |
1298 | trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, |
1299 | zone_idx(zone), |
1300 | nr_scanned, nr_reclaimed, |
1301 | sc->priority, |
1302 | trace_shrink_flags(file)); |
1303 | return nr_reclaimed; |
1304 | } |
1305 | |
1306 | /* |
1307 | * This moves pages from the active list to the inactive list. |
1308 | * |
1309 | * We move them the other way if the page is referenced by one or more |
1310 | * processes, from rmap. |
1311 | * |
1312 | * If the pages are mostly unmapped, the processing is fast and it is |
1313 | * appropriate to hold zone->lru_lock across the whole operation. But if |
1314 | * the pages are mapped, the processing is slow (page_referenced()) so we |
1315 | * should drop zone->lru_lock around each page. It's impossible to balance |
1316 | * this, so instead we remove the pages from the LRU while processing them. |
1317 | * It is safe to rely on PG_active against the non-LRU pages in here because |
1318 | * nobody will play with that bit on a non-LRU page. |
1319 | * |
1320 | * The downside is that we have to touch page->_count against each page. |
1321 | * But we had to alter page->flags anyway. |
1322 | */ |
1323 | |
1324 | static void move_active_pages_to_lru(struct lruvec *lruvec, |
1325 | struct list_head *list, |
1326 | struct list_head *pages_to_free, |
1327 | enum lru_list lru) |
1328 | { |
1329 | struct zone *zone = lruvec_zone(lruvec); |
1330 | unsigned long pgmoved = 0; |
1331 | struct page *page; |
1332 | int nr_pages; |
1333 | |
1334 | while (!list_empty(list)) { |
1335 | page = lru_to_page(list); |
1336 | lruvec = mem_cgroup_page_lruvec(page, zone); |
1337 | |
1338 | VM_BUG_ON(PageLRU(page)); |
1339 | SetPageLRU(page); |
1340 | |
1341 | nr_pages = hpage_nr_pages(page); |
1342 | mem_cgroup_update_lru_size(lruvec, lru, nr_pages); |
1343 | list_move(&page->lru, &lruvec->lists[lru]); |
1344 | pgmoved += nr_pages; |
1345 | |
1346 | if (put_page_testzero(page)) { |
1347 | __ClearPageLRU(page); |
1348 | __ClearPageActive(page); |
1349 | del_page_from_lru_list(page, lruvec, lru); |
1350 | |
1351 | if (unlikely(PageCompound(page))) { |
1352 | spin_unlock_irq(&zone->lru_lock); |
1353 | (*get_compound_page_dtor(page))(page); |
1354 | spin_lock_irq(&zone->lru_lock); |
1355 | } else |
1356 | list_add(&page->lru, pages_to_free); |
1357 | } |
1358 | } |
1359 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); |
1360 | if (!is_active_lru(lru)) |
1361 | __count_vm_events(PGDEACTIVATE, pgmoved); |
1362 | } |
1363 | |
1364 | static void shrink_active_list(unsigned long nr_to_scan, |
1365 | struct lruvec *lruvec, |
1366 | struct scan_control *sc, |
1367 | enum lru_list lru) |
1368 | { |
1369 | unsigned long nr_taken; |
1370 | unsigned long nr_scanned; |
1371 | unsigned long vm_flags; |
1372 | LIST_HEAD(l_hold); /* The pages which were snipped off */ |
1373 | LIST_HEAD(l_active); |
1374 | LIST_HEAD(l_inactive); |
1375 | struct page *page; |
1376 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
1377 | unsigned long nr_rotated = 0; |
1378 | isolate_mode_t isolate_mode = 0; |
1379 | int file = is_file_lru(lru); |
1380 | struct zone *zone = lruvec_zone(lruvec); |
1381 | |
1382 | lru_add_drain(); |
1383 | |
1384 | if (!sc->may_unmap) |
1385 | isolate_mode |= ISOLATE_UNMAPPED; |
1386 | if (!sc->may_writepage) |
1387 | isolate_mode |= ISOLATE_CLEAN; |
1388 | |
1389 | spin_lock_irq(&zone->lru_lock); |
1390 | |
1391 | nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold, |
1392 | &nr_scanned, sc, isolate_mode, lru); |
1393 | if (global_reclaim(sc)) |
1394 | zone->pages_scanned += nr_scanned; |
1395 | |
1396 | reclaim_stat->recent_scanned[file] += nr_taken; |
1397 | |
1398 | __count_zone_vm_events(PGREFILL, zone, nr_scanned); |
1399 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken); |
1400 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); |
1401 | spin_unlock_irq(&zone->lru_lock); |
1402 | |
1403 | while (!list_empty(&l_hold)) { |
1404 | cond_resched(); |
1405 | page = lru_to_page(&l_hold); |
1406 | list_del(&page->lru); |
1407 | |
1408 | if (unlikely(!page_evictable(page, NULL))) { |
1409 | putback_lru_page(page); |
1410 | continue; |
1411 | } |
1412 | |
1413 | if (unlikely(buffer_heads_over_limit)) { |
1414 | if (page_has_private(page) && trylock_page(page)) { |
1415 | if (page_has_private(page)) |
1416 | try_to_release_page(page, 0); |
1417 | unlock_page(page); |
1418 | } |
1419 | } |
1420 | |
1421 | if (page_referenced(page, 0, sc->target_mem_cgroup, |
1422 | &vm_flags)) { |
1423 | nr_rotated += hpage_nr_pages(page); |
1424 | /* |
1425 | * Identify referenced, file-backed active pages and |
1426 | * give them one more trip around the active list. So |
1427 | * that executable code get better chances to stay in |
1428 | * memory under moderate memory pressure. Anon pages |
1429 | * are not likely to be evicted by use-once streaming |
1430 | * IO, plus JVM can create lots of anon VM_EXEC pages, |
1431 | * so we ignore them here. |
1432 | */ |
1433 | if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { |
1434 | list_add(&page->lru, &l_active); |
1435 | continue; |
1436 | } |
1437 | } |
1438 | |
1439 | ClearPageActive(page); /* we are de-activating */ |
1440 | list_add(&page->lru, &l_inactive); |
1441 | } |
1442 | |
1443 | /* |
1444 | * Move pages back to the lru list. |
1445 | */ |
1446 | spin_lock_irq(&zone->lru_lock); |
1447 | /* |
1448 | * Count referenced pages from currently used mappings as rotated, |
1449 | * even though only some of them are actually re-activated. This |
1450 | * helps balance scan pressure between file and anonymous pages in |
1451 | * get_scan_ratio. |
1452 | */ |
1453 | reclaim_stat->recent_rotated[file] += nr_rotated; |
1454 | |
1455 | move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru); |
1456 | move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE); |
1457 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); |
1458 | spin_unlock_irq(&zone->lru_lock); |
1459 | |
1460 | free_hot_cold_page_list(&l_hold, 1); |
1461 | } |
1462 | |
1463 | #ifdef CONFIG_SWAP |
1464 | static int inactive_anon_is_low_global(struct zone *zone) |
1465 | { |
1466 | unsigned long active, inactive; |
1467 | |
1468 | active = zone_page_state(zone, NR_ACTIVE_ANON); |
1469 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
1470 | |
1471 | if (inactive * zone->inactive_ratio < active) |
1472 | return 1; |
1473 | |
1474 | return 0; |
1475 | } |
1476 | |
1477 | /** |
1478 | * inactive_anon_is_low - check if anonymous pages need to be deactivated |
1479 | * @lruvec: LRU vector to check |
1480 | * |
1481 | * Returns true if the zone does not have enough inactive anon pages, |
1482 | * meaning some active anon pages need to be deactivated. |
1483 | */ |
1484 | static int inactive_anon_is_low(struct lruvec *lruvec) |
1485 | { |
1486 | /* |
1487 | * If we don't have swap space, anonymous page deactivation |
1488 | * is pointless. |
1489 | */ |
1490 | if (!total_swap_pages) |
1491 | return 0; |
1492 | |
1493 | if (!mem_cgroup_disabled()) |
1494 | return mem_cgroup_inactive_anon_is_low(lruvec); |
1495 | |
1496 | return inactive_anon_is_low_global(lruvec_zone(lruvec)); |
1497 | } |
1498 | #else |
1499 | static inline int inactive_anon_is_low(struct lruvec *lruvec) |
1500 | { |
1501 | return 0; |
1502 | } |
1503 | #endif |
1504 | |
1505 | static int inactive_file_is_low_global(struct zone *zone) |
1506 | { |
1507 | unsigned long active, inactive; |
1508 | |
1509 | active = zone_page_state(zone, NR_ACTIVE_FILE); |
1510 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); |
1511 | |
1512 | return (active > inactive); |
1513 | } |
1514 | |
1515 | /** |
1516 | * inactive_file_is_low - check if file pages need to be deactivated |
1517 | * @lruvec: LRU vector to check |
1518 | * |
1519 | * When the system is doing streaming IO, memory pressure here |
1520 | * ensures that active file pages get deactivated, until more |
1521 | * than half of the file pages are on the inactive list. |
1522 | * |
1523 | * Once we get to that situation, protect the system's working |
1524 | * set from being evicted by disabling active file page aging. |
1525 | * |
1526 | * This uses a different ratio than the anonymous pages, because |
1527 | * the page cache uses a use-once replacement algorithm. |
1528 | */ |
1529 | static int inactive_file_is_low(struct lruvec *lruvec) |
1530 | { |
1531 | if (!mem_cgroup_disabled()) |
1532 | return mem_cgroup_inactive_file_is_low(lruvec); |
1533 | |
1534 | return inactive_file_is_low_global(lruvec_zone(lruvec)); |
1535 | } |
1536 | |
1537 | static int inactive_list_is_low(struct lruvec *lruvec, enum lru_list lru) |
1538 | { |
1539 | if (is_file_lru(lru)) |
1540 | return inactive_file_is_low(lruvec); |
1541 | else |
1542 | return inactive_anon_is_low(lruvec); |
1543 | } |
1544 | |
1545 | static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, |
1546 | struct lruvec *lruvec, struct scan_control *sc) |
1547 | { |
1548 | if (is_active_lru(lru)) { |
1549 | if (inactive_list_is_low(lruvec, lru)) |
1550 | shrink_active_list(nr_to_scan, lruvec, sc, lru); |
1551 | return 0; |
1552 | } |
1553 | |
1554 | return shrink_inactive_list(nr_to_scan, lruvec, sc, lru); |
1555 | } |
1556 | |
1557 | static int vmscan_swappiness(struct scan_control *sc) |
1558 | { |
1559 | if (global_reclaim(sc)) |
1560 | return vm_swappiness; |
1561 | return mem_cgroup_swappiness(sc->target_mem_cgroup); |
1562 | } |
1563 | |
1564 | /* |
1565 | * Determine how aggressively the anon and file LRU lists should be |
1566 | * scanned. The relative value of each set of LRU lists is determined |
1567 | * by looking at the fraction of the pages scanned we did rotate back |
1568 | * onto the active list instead of evict. |
1569 | * |
1570 | * nr[0] = anon pages to scan; nr[1] = file pages to scan |
1571 | */ |
1572 | static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, |
1573 | unsigned long *nr) |
1574 | { |
1575 | unsigned long anon, file, free; |
1576 | unsigned long anon_prio, file_prio; |
1577 | unsigned long ap, fp; |
1578 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
1579 | u64 fraction[2], denominator; |
1580 | enum lru_list lru; |
1581 | int noswap = 0; |
1582 | bool force_scan = false; |
1583 | struct zone *zone = lruvec_zone(lruvec); |
1584 | |
1585 | /* |
1586 | * If the zone or memcg is small, nr[l] can be 0. This |
1587 | * results in no scanning on this priority and a potential |
1588 | * priority drop. Global direct reclaim can go to the next |
1589 | * zone and tends to have no problems. Global kswapd is for |
1590 | * zone balancing and it needs to scan a minimum amount. When |
1591 | * reclaiming for a memcg, a priority drop can cause high |
1592 | * latencies, so it's better to scan a minimum amount there as |
1593 | * well. |
1594 | */ |
1595 | if (current_is_kswapd() && zone->all_unreclaimable) |
1596 | force_scan = true; |
1597 | if (!global_reclaim(sc)) |
1598 | force_scan = true; |
1599 | |
1600 | /* If we have no swap space, do not bother scanning anon pages. */ |
1601 | if (!sc->may_swap || (nr_swap_pages <= 0)) { |
1602 | noswap = 1; |
1603 | fraction[0] = 0; |
1604 | fraction[1] = 1; |
1605 | denominator = 1; |
1606 | goto out; |
1607 | } |
1608 | |
1609 | anon = get_lru_size(lruvec, LRU_ACTIVE_ANON) + |
1610 | get_lru_size(lruvec, LRU_INACTIVE_ANON); |
1611 | file = get_lru_size(lruvec, LRU_ACTIVE_FILE) + |
1612 | get_lru_size(lruvec, LRU_INACTIVE_FILE); |
1613 | |
1614 | if (global_reclaim(sc)) { |
1615 | free = zone_page_state(zone, NR_FREE_PAGES); |
1616 | /* If we have very few page cache pages, |
1617 | force-scan anon pages. */ |
1618 | if (unlikely(file + free <= high_wmark_pages(zone))) { |
1619 | fraction[0] = 1; |
1620 | fraction[1] = 0; |
1621 | denominator = 1; |
1622 | goto out; |
1623 | } |
1624 | } |
1625 | |
1626 | /* |
1627 | * With swappiness at 100, anonymous and file have the same priority. |
1628 | * This scanning priority is essentially the inverse of IO cost. |
1629 | */ |
1630 | anon_prio = vmscan_swappiness(sc); |
1631 | file_prio = 200 - anon_prio; |
1632 | |
1633 | /* |
1634 | * OK, so we have swap space and a fair amount of page cache |
1635 | * pages. We use the recently rotated / recently scanned |
1636 | * ratios to determine how valuable each cache is. |
1637 | * |
1638 | * Because workloads change over time (and to avoid overflow) |
1639 | * we keep these statistics as a floating average, which ends |
1640 | * up weighing recent references more than old ones. |
1641 | * |
1642 | * anon in [0], file in [1] |
1643 | */ |
1644 | spin_lock_irq(&zone->lru_lock); |
1645 | if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { |
1646 | reclaim_stat->recent_scanned[0] /= 2; |
1647 | reclaim_stat->recent_rotated[0] /= 2; |
1648 | } |
1649 | |
1650 | if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { |
1651 | reclaim_stat->recent_scanned[1] /= 2; |
1652 | reclaim_stat->recent_rotated[1] /= 2; |
1653 | } |
1654 | |
1655 | /* |
1656 | * The amount of pressure on anon vs file pages is inversely |
1657 | * proportional to the fraction of recently scanned pages on |
1658 | * each list that were recently referenced and in active use. |
1659 | */ |
1660 | ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1); |
1661 | ap /= reclaim_stat->recent_rotated[0] + 1; |
1662 | |
1663 | fp = file_prio * (reclaim_stat->recent_scanned[1] + 1); |
1664 | fp /= reclaim_stat->recent_rotated[1] + 1; |
1665 | spin_unlock_irq(&zone->lru_lock); |
1666 | |
1667 | fraction[0] = ap; |
1668 | fraction[1] = fp; |
1669 | denominator = ap + fp + 1; |
1670 | out: |
1671 | for_each_evictable_lru(lru) { |
1672 | int file = is_file_lru(lru); |
1673 | unsigned long scan; |
1674 | |
1675 | scan = get_lru_size(lruvec, lru); |
1676 | if (sc->priority || noswap || !vmscan_swappiness(sc)) { |
1677 | scan >>= sc->priority; |
1678 | if (!scan && force_scan) |
1679 | scan = SWAP_CLUSTER_MAX; |
1680 | scan = div64_u64(scan * fraction[file], denominator); |
1681 | } |
1682 | nr[lru] = scan; |
1683 | } |
1684 | } |
1685 | |
1686 | /* Use reclaim/compaction for costly allocs or under memory pressure */ |
1687 | static bool in_reclaim_compaction(struct scan_control *sc) |
1688 | { |
1689 | if (COMPACTION_BUILD && sc->order && |
1690 | (sc->order > PAGE_ALLOC_COSTLY_ORDER || |
1691 | sc->priority < DEF_PRIORITY - 2)) |
1692 | return true; |
1693 | |
1694 | return false; |
1695 | } |
1696 | |
1697 | /* |
1698 | * Reclaim/compaction is used for high-order allocation requests. It reclaims |
1699 | * order-0 pages before compacting the zone. should_continue_reclaim() returns |
1700 | * true if more pages should be reclaimed such that when the page allocator |
1701 | * calls try_to_compact_zone() that it will have enough free pages to succeed. |
1702 | * It will give up earlier than that if there is difficulty reclaiming pages. |
1703 | */ |
1704 | static inline bool should_continue_reclaim(struct lruvec *lruvec, |
1705 | unsigned long nr_reclaimed, |
1706 | unsigned long nr_scanned, |
1707 | struct scan_control *sc) |
1708 | { |
1709 | unsigned long pages_for_compaction; |
1710 | unsigned long inactive_lru_pages; |
1711 | |
1712 | /* If not in reclaim/compaction mode, stop */ |
1713 | if (!in_reclaim_compaction(sc)) |
1714 | return false; |
1715 | |
1716 | /* Consider stopping depending on scan and reclaim activity */ |
1717 | if (sc->gfp_mask & __GFP_REPEAT) { |
1718 | /* |
1719 | * For __GFP_REPEAT allocations, stop reclaiming if the |
1720 | * full LRU list has been scanned and we are still failing |
1721 | * to reclaim pages. This full LRU scan is potentially |
1722 | * expensive but a __GFP_REPEAT caller really wants to succeed |
1723 | */ |
1724 | if (!nr_reclaimed && !nr_scanned) |
1725 | return false; |
1726 | } else { |
1727 | /* |
1728 | * For non-__GFP_REPEAT allocations which can presumably |
1729 | * fail without consequence, stop if we failed to reclaim |
1730 | * any pages from the last SWAP_CLUSTER_MAX number of |
1731 | * pages that were scanned. This will return to the |
1732 | * caller faster at the risk reclaim/compaction and |
1733 | * the resulting allocation attempt fails |
1734 | */ |
1735 | if (!nr_reclaimed) |
1736 | return false; |
1737 | } |
1738 | |
1739 | /* |
1740 | * If we have not reclaimed enough pages for compaction and the |
1741 | * inactive lists are large enough, continue reclaiming |
1742 | */ |
1743 | pages_for_compaction = (2UL << sc->order); |
1744 | inactive_lru_pages = get_lru_size(lruvec, LRU_INACTIVE_FILE); |
1745 | if (nr_swap_pages > 0) |
1746 | inactive_lru_pages += get_lru_size(lruvec, LRU_INACTIVE_ANON); |
1747 | if (sc->nr_reclaimed < pages_for_compaction && |
1748 | inactive_lru_pages > pages_for_compaction) |
1749 | return true; |
1750 | |
1751 | /* If compaction would go ahead or the allocation would succeed, stop */ |
1752 | switch (compaction_suitable(lruvec_zone(lruvec), sc->order)) { |
1753 | case COMPACT_PARTIAL: |
1754 | case COMPACT_CONTINUE: |
1755 | return false; |
1756 | default: |
1757 | return true; |
1758 | } |
1759 | } |
1760 | |
1761 | /* |
1762 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. |
1763 | */ |
1764 | static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) |
1765 | { |
1766 | unsigned long nr[NR_LRU_LISTS]; |
1767 | unsigned long nr_to_scan; |
1768 | enum lru_list lru; |
1769 | unsigned long nr_reclaimed, nr_scanned; |
1770 | unsigned long nr_to_reclaim = sc->nr_to_reclaim; |
1771 | struct blk_plug plug; |
1772 | |
1773 | restart: |
1774 | nr_reclaimed = 0; |
1775 | nr_scanned = sc->nr_scanned; |
1776 | get_scan_count(lruvec, sc, nr); |
1777 | |
1778 | blk_start_plug(&plug); |
1779 | while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || |
1780 | nr[LRU_INACTIVE_FILE]) { |
1781 | for_each_evictable_lru(lru) { |
1782 | if (nr[lru]) { |
1783 | nr_to_scan = min_t(unsigned long, |
1784 | nr[lru], SWAP_CLUSTER_MAX); |
1785 | nr[lru] -= nr_to_scan; |
1786 | |
1787 | nr_reclaimed += shrink_list(lru, nr_to_scan, |
1788 | lruvec, sc); |
1789 | } |
1790 | } |
1791 | /* |
1792 | * On large memory systems, scan >> priority can become |
1793 | * really large. This is fine for the starting priority; |
1794 | * we want to put equal scanning pressure on each zone. |
1795 | * However, if the VM has a harder time of freeing pages, |
1796 | * with multiple processes reclaiming pages, the total |
1797 | * freeing target can get unreasonably large. |
1798 | */ |
1799 | if (nr_reclaimed >= nr_to_reclaim && |
1800 | sc->priority < DEF_PRIORITY) |
1801 | break; |
1802 | } |
1803 | blk_finish_plug(&plug); |
1804 | sc->nr_reclaimed += nr_reclaimed; |
1805 | |
1806 | /* |
1807 | * Even if we did not try to evict anon pages at all, we want to |
1808 | * rebalance the anon lru active/inactive ratio. |
1809 | */ |
1810 | if (inactive_anon_is_low(lruvec)) |
1811 | shrink_active_list(SWAP_CLUSTER_MAX, lruvec, |
1812 | sc, LRU_ACTIVE_ANON); |
1813 | |
1814 | /* reclaim/compaction might need reclaim to continue */ |
1815 | if (should_continue_reclaim(lruvec, nr_reclaimed, |
1816 | sc->nr_scanned - nr_scanned, sc)) |
1817 | goto restart; |
1818 | |
1819 | throttle_vm_writeout(sc->gfp_mask); |
1820 | } |
1821 | |
1822 | static void shrink_zone(struct zone *zone, struct scan_control *sc) |
1823 | { |
1824 | struct mem_cgroup *root = sc->target_mem_cgroup; |
1825 | struct mem_cgroup_reclaim_cookie reclaim = { |
1826 | .zone = zone, |
1827 | .priority = sc->priority, |
1828 | }; |
1829 | struct mem_cgroup *memcg; |
1830 | |
1831 | memcg = mem_cgroup_iter(root, NULL, &reclaim); |
1832 | do { |
1833 | struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
1834 | |
1835 | shrink_lruvec(lruvec, sc); |
1836 | |
1837 | /* |
1838 | * Limit reclaim has historically picked one memcg and |
1839 | * scanned it with decreasing priority levels until |
1840 | * nr_to_reclaim had been reclaimed. This priority |
1841 | * cycle is thus over after a single memcg. |
1842 | * |
1843 | * Direct reclaim and kswapd, on the other hand, have |
1844 | * to scan all memory cgroups to fulfill the overall |
1845 | * scan target for the zone. |
1846 | */ |
1847 | if (!global_reclaim(sc)) { |
1848 | mem_cgroup_iter_break(root, memcg); |
1849 | break; |
1850 | } |
1851 | memcg = mem_cgroup_iter(root, memcg, &reclaim); |
1852 | } while (memcg); |
1853 | } |
1854 | |
1855 | /* Returns true if compaction should go ahead for a high-order request */ |
1856 | static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) |
1857 | { |
1858 | unsigned long balance_gap, watermark; |
1859 | bool watermark_ok; |
1860 | |
1861 | /* Do not consider compaction for orders reclaim is meant to satisfy */ |
1862 | if (sc->order <= PAGE_ALLOC_COSTLY_ORDER) |
1863 | return false; |
1864 | |
1865 | /* |
1866 | * Compaction takes time to run and there are potentially other |
1867 | * callers using the pages just freed. Continue reclaiming until |
1868 | * there is a buffer of free pages available to give compaction |
1869 | * a reasonable chance of completing and allocating the page |
1870 | */ |
1871 | balance_gap = min(low_wmark_pages(zone), |
1872 | (zone->present_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / |
1873 | KSWAPD_ZONE_BALANCE_GAP_RATIO); |
1874 | watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order); |
1875 | watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0); |
1876 | |
1877 | /* |
1878 | * If compaction is deferred, reclaim up to a point where |
1879 | * compaction will have a chance of success when re-enabled |
1880 | */ |
1881 | if (compaction_deferred(zone, sc->order)) |
1882 | return watermark_ok; |
1883 | |
1884 | /* If compaction is not ready to start, keep reclaiming */ |
1885 | if (!compaction_suitable(zone, sc->order)) |
1886 | return false; |
1887 | |
1888 | return watermark_ok; |
1889 | } |
1890 | |
1891 | /* |
1892 | * This is the direct reclaim path, for page-allocating processes. We only |
1893 | * try to reclaim pages from zones which will satisfy the caller's allocation |
1894 | * request. |
1895 | * |
1896 | * We reclaim from a zone even if that zone is over high_wmark_pages(zone). |
1897 | * Because: |
1898 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order |
1899 | * allocation or |
1900 | * b) The target zone may be at high_wmark_pages(zone) but the lower zones |
1901 | * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' |
1902 | * zone defense algorithm. |
1903 | * |
1904 | * If a zone is deemed to be full of pinned pages then just give it a light |
1905 | * scan then give up on it. |
1906 | * |
1907 | * This function returns true if a zone is being reclaimed for a costly |
1908 | * high-order allocation and compaction is ready to begin. This indicates to |
1909 | * the caller that it should consider retrying the allocation instead of |
1910 | * further reclaim. |
1911 | */ |
1912 | static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) |
1913 | { |
1914 | struct zoneref *z; |
1915 | struct zone *zone; |
1916 | unsigned long nr_soft_reclaimed; |
1917 | unsigned long nr_soft_scanned; |
1918 | bool aborted_reclaim = false; |
1919 | |
1920 | /* |
1921 | * If the number of buffer_heads in the machine exceeds the maximum |
1922 | * allowed level, force direct reclaim to scan the highmem zone as |
1923 | * highmem pages could be pinning lowmem pages storing buffer_heads |
1924 | */ |
1925 | if (buffer_heads_over_limit) |
1926 | sc->gfp_mask |= __GFP_HIGHMEM; |
1927 | |
1928 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
1929 | gfp_zone(sc->gfp_mask), sc->nodemask) { |
1930 | if (!populated_zone(zone)) |
1931 | continue; |
1932 | /* |
1933 | * Take care memory controller reclaiming has small influence |
1934 | * to global LRU. |
1935 | */ |
1936 | if (global_reclaim(sc)) { |
1937 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
1938 | continue; |
1939 | if (zone->all_unreclaimable && |
1940 | sc->priority != DEF_PRIORITY) |
1941 | continue; /* Let kswapd poll it */ |
1942 | if (COMPACTION_BUILD) { |
1943 | /* |
1944 | * If we already have plenty of memory free for |
1945 | * compaction in this zone, don't free any more. |
1946 | * Even though compaction is invoked for any |
1947 | * non-zero order, only frequent costly order |
1948 | * reclamation is disruptive enough to become a |
1949 | * noticeable problem, like transparent huge |
1950 | * page allocations. |
1951 | */ |
1952 | if (compaction_ready(zone, sc)) { |
1953 | aborted_reclaim = true; |
1954 | continue; |
1955 | } |
1956 | } |
1957 | /* |
1958 | * This steals pages from memory cgroups over softlimit |
1959 | * and returns the number of reclaimed pages and |
1960 | * scanned pages. This works for global memory pressure |
1961 | * and balancing, not for a memcg's limit. |
1962 | */ |
1963 | nr_soft_scanned = 0; |
1964 | nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, |
1965 | sc->order, sc->gfp_mask, |
1966 | &nr_soft_scanned); |
1967 | sc->nr_reclaimed += nr_soft_reclaimed; |
1968 | sc->nr_scanned += nr_soft_scanned; |
1969 | /* need some check for avoid more shrink_zone() */ |
1970 | } |
1971 | |
1972 | shrink_zone(zone, sc); |
1973 | } |
1974 | |
1975 | return aborted_reclaim; |
1976 | } |
1977 | |
1978 | static bool zone_reclaimable(struct zone *zone) |
1979 | { |
1980 | return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; |
1981 | } |
1982 | |
1983 | /* All zones in zonelist are unreclaimable? */ |
1984 | static bool all_unreclaimable(struct zonelist *zonelist, |
1985 | struct scan_control *sc) |
1986 | { |
1987 | struct zoneref *z; |
1988 | struct zone *zone; |
1989 | |
1990 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
1991 | gfp_zone(sc->gfp_mask), sc->nodemask) { |
1992 | if (!populated_zone(zone)) |
1993 | continue; |
1994 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
1995 | continue; |
1996 | if (!zone->all_unreclaimable) |
1997 | return false; |
1998 | } |
1999 | |
2000 | return true; |
2001 | } |
2002 | |
2003 | /* |
2004 | * This is the main entry point to direct page reclaim. |
2005 | * |
2006 | * If a full scan of the inactive list fails to free enough memory then we |
2007 | * are "out of memory" and something needs to be killed. |
2008 | * |
2009 | * If the caller is !__GFP_FS then the probability of a failure is reasonably |
2010 | * high - the zone may be full of dirty or under-writeback pages, which this |
2011 | * caller can't do much about. We kick the writeback threads and take explicit |
2012 | * naps in the hope that some of these pages can be written. But if the |
2013 | * allocating task holds filesystem locks which prevent writeout this might not |
2014 | * work, and the allocation attempt will fail. |
2015 | * |
2016 | * returns: 0, if no pages reclaimed |
2017 | * else, the number of pages reclaimed |
2018 | */ |
2019 | static unsigned long do_try_to_free_pages(struct zonelist *zonelist, |
2020 | struct scan_control *sc, |
2021 | struct shrink_control *shrink) |
2022 | { |
2023 | unsigned long total_scanned = 0; |
2024 | struct reclaim_state *reclaim_state = current->reclaim_state; |
2025 | struct zoneref *z; |
2026 | struct zone *zone; |
2027 | unsigned long writeback_threshold; |
2028 | bool aborted_reclaim; |
2029 | |
2030 | delayacct_freepages_start(); |
2031 | |
2032 | if (global_reclaim(sc)) |
2033 | count_vm_event(ALLOCSTALL); |
2034 | |
2035 | do { |
2036 | sc->nr_scanned = 0; |
2037 | aborted_reclaim = shrink_zones(zonelist, sc); |
2038 | |
2039 | /* |
2040 | * Don't shrink slabs when reclaiming memory from |
2041 | * over limit cgroups |
2042 | */ |
2043 | if (global_reclaim(sc)) { |
2044 | unsigned long lru_pages = 0; |
2045 | for_each_zone_zonelist(zone, z, zonelist, |
2046 | gfp_zone(sc->gfp_mask)) { |
2047 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2048 | continue; |
2049 | |
2050 | lru_pages += zone_reclaimable_pages(zone); |
2051 | } |
2052 | |
2053 | shrink_slab(shrink, sc->nr_scanned, lru_pages); |
2054 | if (reclaim_state) { |
2055 | sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
2056 | reclaim_state->reclaimed_slab = 0; |
2057 | } |
2058 | } |
2059 | total_scanned += sc->nr_scanned; |
2060 | if (sc->nr_reclaimed >= sc->nr_to_reclaim) |
2061 | goto out; |
2062 | |
2063 | /* |
2064 | * Try to write back as many pages as we just scanned. This |
2065 | * tends to cause slow streaming writers to write data to the |
2066 | * disk smoothly, at the dirtying rate, which is nice. But |
2067 | * that's undesirable in laptop mode, where we *want* lumpy |
2068 | * writeout. So in laptop mode, write out the whole world. |
2069 | */ |
2070 | writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; |
2071 | if (total_scanned > writeback_threshold) { |
2072 | wakeup_flusher_threads(laptop_mode ? 0 : total_scanned, |
2073 | WB_REASON_TRY_TO_FREE_PAGES); |
2074 | sc->may_writepage = 1; |
2075 | } |
2076 | |
2077 | /* Take a nap, wait for some writeback to complete */ |
2078 | if (!sc->hibernation_mode && sc->nr_scanned && |
2079 | sc->priority < DEF_PRIORITY - 2) { |
2080 | struct zone *preferred_zone; |
2081 | |
2082 | first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), |
2083 | &cpuset_current_mems_allowed, |
2084 | &preferred_zone); |
2085 | wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); |
2086 | } |
2087 | } while (--sc->priority >= 0); |
2088 | |
2089 | out: |
2090 | delayacct_freepages_end(); |
2091 | |
2092 | if (sc->nr_reclaimed) |
2093 | return sc->nr_reclaimed; |
2094 | |
2095 | /* |
2096 | * As hibernation is going on, kswapd is freezed so that it can't mark |
2097 | * the zone into all_unreclaimable. Thus bypassing all_unreclaimable |
2098 | * check. |
2099 | */ |
2100 | if (oom_killer_disabled) |
2101 | return 0; |
2102 | |
2103 | /* Aborted reclaim to try compaction? don't OOM, then */ |
2104 | if (aborted_reclaim) |
2105 | return 1; |
2106 | |
2107 | /* top priority shrink_zones still had more to do? don't OOM, then */ |
2108 | if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc)) |
2109 | return 1; |
2110 | |
2111 | return 0; |
2112 | } |
2113 | |
2114 | unsigned long try_to_free_pages(struct zonelist *zonelist, int order, |
2115 | gfp_t gfp_mask, nodemask_t *nodemask) |
2116 | { |
2117 | unsigned long nr_reclaimed; |
2118 | struct scan_control sc = { |
2119 | .gfp_mask = gfp_mask, |
2120 | .may_writepage = !laptop_mode, |
2121 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2122 | .may_unmap = 1, |
2123 | .may_swap = 1, |
2124 | .order = order, |
2125 | .priority = DEF_PRIORITY, |
2126 | .target_mem_cgroup = NULL, |
2127 | .nodemask = nodemask, |
2128 | }; |
2129 | struct shrink_control shrink = { |
2130 | .gfp_mask = sc.gfp_mask, |
2131 | }; |
2132 | |
2133 | trace_mm_vmscan_direct_reclaim_begin(order, |
2134 | sc.may_writepage, |
2135 | gfp_mask); |
2136 | |
2137 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
2138 | |
2139 | trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); |
2140 | |
2141 | return nr_reclaimed; |
2142 | } |
2143 | |
2144 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
2145 | |
2146 | unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg, |
2147 | gfp_t gfp_mask, bool noswap, |
2148 | struct zone *zone, |
2149 | unsigned long *nr_scanned) |
2150 | { |
2151 | struct scan_control sc = { |
2152 | .nr_scanned = 0, |
2153 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2154 | .may_writepage = !laptop_mode, |
2155 | .may_unmap = 1, |
2156 | .may_swap = !noswap, |
2157 | .order = 0, |
2158 | .priority = 0, |
2159 | .target_mem_cgroup = memcg, |
2160 | }; |
2161 | struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
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(sc.order, |
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_lruvec(lruvec, &sc); |
2178 | |
2179 | trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); |
2180 | |
2181 | *nr_scanned = sc.nr_scanned; |
2182 | return sc.nr_reclaimed; |
2183 | } |
2184 | |
2185 | unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, |
2186 | gfp_t gfp_mask, |
2187 | bool noswap) |
2188 | { |
2189 | struct zonelist *zonelist; |
2190 | unsigned long nr_reclaimed; |
2191 | int nid; |
2192 | struct scan_control sc = { |
2193 | .may_writepage = !laptop_mode, |
2194 | .may_unmap = 1, |
2195 | .may_swap = !noswap, |
2196 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
2197 | .order = 0, |
2198 | .priority = DEF_PRIORITY, |
2199 | .target_mem_cgroup = memcg, |
2200 | .nodemask = NULL, /* we don't care the placement */ |
2201 | .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
2202 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), |
2203 | }; |
2204 | struct shrink_control shrink = { |
2205 | .gfp_mask = sc.gfp_mask, |
2206 | }; |
2207 | |
2208 | /* |
2209 | * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't |
2210 | * take care of from where we get pages. So the node where we start the |
2211 | * scan does not need to be the current node. |
2212 | */ |
2213 | nid = mem_cgroup_select_victim_node(memcg); |
2214 | |
2215 | zonelist = NODE_DATA(nid)->node_zonelists; |
2216 | |
2217 | trace_mm_vmscan_memcg_reclaim_begin(0, |
2218 | sc.may_writepage, |
2219 | sc.gfp_mask); |
2220 | |
2221 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
2222 | |
2223 | trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); |
2224 | |
2225 | return nr_reclaimed; |
2226 | } |
2227 | #endif |
2228 | |
2229 | static void age_active_anon(struct zone *zone, struct scan_control *sc) |
2230 | { |
2231 | struct mem_cgroup *memcg; |
2232 | |
2233 | if (!total_swap_pages) |
2234 | return; |
2235 | |
2236 | memcg = mem_cgroup_iter(NULL, NULL, NULL); |
2237 | do { |
2238 | struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
2239 | |
2240 | if (inactive_anon_is_low(lruvec)) |
2241 | shrink_active_list(SWAP_CLUSTER_MAX, lruvec, |
2242 | sc, LRU_ACTIVE_ANON); |
2243 | |
2244 | memcg = mem_cgroup_iter(NULL, memcg, NULL); |
2245 | } while (memcg); |
2246 | } |
2247 | |
2248 | /* |
2249 | * pgdat_balanced is used when checking if a node is balanced for high-order |
2250 | * allocations. Only zones that meet watermarks and are in a zone allowed |
2251 | * by the callers classzone_idx are added to balanced_pages. The total of |
2252 | * balanced pages must be at least 25% of the zones allowed by classzone_idx |
2253 | * for the node to be considered balanced. Forcing all zones to be balanced |
2254 | * for high orders can cause excessive reclaim when there are imbalanced zones. |
2255 | * The choice of 25% is due to |
2256 | * o a 16M DMA zone that is balanced will not balance a zone on any |
2257 | * reasonable sized machine |
2258 | * o On all other machines, the top zone must be at least a reasonable |
2259 | * percentage of the middle zones. For example, on 32-bit x86, highmem |
2260 | * would need to be at least 256M for it to be balance a whole node. |
2261 | * Similarly, on x86-64 the Normal zone would need to be at least 1G |
2262 | * to balance a node on its own. These seemed like reasonable ratios. |
2263 | */ |
2264 | static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, |
2265 | int classzone_idx) |
2266 | { |
2267 | unsigned long present_pages = 0; |
2268 | int i; |
2269 | |
2270 | for (i = 0; i <= classzone_idx; i++) |
2271 | present_pages += pgdat->node_zones[i].present_pages; |
2272 | |
2273 | /* A special case here: if zone has no page, we think it's balanced */ |
2274 | return balanced_pages >= (present_pages >> 2); |
2275 | } |
2276 | |
2277 | /* is kswapd sleeping prematurely? */ |
2278 | static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, |
2279 | int classzone_idx) |
2280 | { |
2281 | int i; |
2282 | unsigned long balanced = 0; |
2283 | bool all_zones_ok = true; |
2284 | |
2285 | /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ |
2286 | if (remaining) |
2287 | return true; |
2288 | |
2289 | /* Check the watermark levels */ |
2290 | for (i = 0; i <= classzone_idx; i++) { |
2291 | struct zone *zone = pgdat->node_zones + i; |
2292 | |
2293 | if (!populated_zone(zone)) |
2294 | continue; |
2295 | |
2296 | /* |
2297 | * balance_pgdat() skips over all_unreclaimable after |
2298 | * DEF_PRIORITY. Effectively, it considers them balanced so |
2299 | * they must be considered balanced here as well if kswapd |
2300 | * is to sleep |
2301 | */ |
2302 | if (zone->all_unreclaimable) { |
2303 | balanced += zone->present_pages; |
2304 | continue; |
2305 | } |
2306 | |
2307 | if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), |
2308 | i, 0)) |
2309 | all_zones_ok = false; |
2310 | else |
2311 | balanced += zone->present_pages; |
2312 | } |
2313 | |
2314 | /* |
2315 | * For high-order requests, the balanced zones must contain at least |
2316 | * 25% of the nodes pages for kswapd to sleep. For order-0, all zones |
2317 | * must be balanced |
2318 | */ |
2319 | if (order) |
2320 | return !pgdat_balanced(pgdat, balanced, classzone_idx); |
2321 | else |
2322 | return !all_zones_ok; |
2323 | } |
2324 | |
2325 | /* |
2326 | * For kswapd, balance_pgdat() will work across all this node's zones until |
2327 | * they are all at high_wmark_pages(zone). |
2328 | * |
2329 | * Returns the final order kswapd was reclaiming at |
2330 | * |
2331 | * There is special handling here for zones which are full of pinned pages. |
2332 | * This can happen if the pages are all mlocked, or if they are all used by |
2333 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. |
2334 | * What we do is to detect the case where all pages in the zone have been |
2335 | * scanned twice and there has been zero successful reclaim. Mark the zone as |
2336 | * dead and from now on, only perform a short scan. Basically we're polling |
2337 | * the zone for when the problem goes away. |
2338 | * |
2339 | * kswapd scans the zones in the highmem->normal->dma direction. It skips |
2340 | * zones which have free_pages > high_wmark_pages(zone), but once a zone is |
2341 | * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the |
2342 | * lower zones regardless of the number of free pages in the lower zones. This |
2343 | * interoperates with the page allocator fallback scheme to ensure that aging |
2344 | * of pages is balanced across the zones. |
2345 | */ |
2346 | static unsigned long balance_pgdat(pg_data_t *pgdat, int order, |
2347 | int *classzone_idx) |
2348 | { |
2349 | int all_zones_ok; |
2350 | unsigned long balanced; |
2351 | int i; |
2352 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ |
2353 | unsigned long total_scanned; |
2354 | struct reclaim_state *reclaim_state = current->reclaim_state; |
2355 | unsigned long nr_soft_reclaimed; |
2356 | unsigned long nr_soft_scanned; |
2357 | struct scan_control sc = { |
2358 | .gfp_mask = GFP_KERNEL, |
2359 | .may_unmap = 1, |
2360 | .may_swap = 1, |
2361 | /* |
2362 | * kswapd doesn't want to be bailed out while reclaim. because |
2363 | * we want to put equal scanning pressure on each zone. |
2364 | */ |
2365 | .nr_to_reclaim = ULONG_MAX, |
2366 | .order = order, |
2367 | .target_mem_cgroup = NULL, |
2368 | }; |
2369 | struct shrink_control shrink = { |
2370 | .gfp_mask = sc.gfp_mask, |
2371 | }; |
2372 | loop_again: |
2373 | total_scanned = 0; |
2374 | sc.priority = DEF_PRIORITY; |
2375 | sc.nr_reclaimed = 0; |
2376 | sc.may_writepage = !laptop_mode; |
2377 | count_vm_event(PAGEOUTRUN); |
2378 | |
2379 | do { |
2380 | unsigned long lru_pages = 0; |
2381 | int has_under_min_watermark_zone = 0; |
2382 | |
2383 | all_zones_ok = 1; |
2384 | balanced = 0; |
2385 | |
2386 | /* |
2387 | * Scan in the highmem->dma direction for the highest |
2388 | * zone which needs scanning |
2389 | */ |
2390 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { |
2391 | struct zone *zone = pgdat->node_zones + i; |
2392 | |
2393 | if (!populated_zone(zone)) |
2394 | continue; |
2395 | |
2396 | if (zone->all_unreclaimable && |
2397 | sc.priority != DEF_PRIORITY) |
2398 | continue; |
2399 | |
2400 | /* |
2401 | * Do some background aging of the anon list, to give |
2402 | * pages a chance to be referenced before reclaiming. |
2403 | */ |
2404 | age_active_anon(zone, &sc); |
2405 | |
2406 | /* |
2407 | * If the number of buffer_heads in the machine |
2408 | * exceeds the maximum allowed level and this node |
2409 | * has a highmem zone, force kswapd to reclaim from |
2410 | * it to relieve lowmem pressure. |
2411 | */ |
2412 | if (buffer_heads_over_limit && is_highmem_idx(i)) { |
2413 | end_zone = i; |
2414 | break; |
2415 | } |
2416 | |
2417 | if (!zone_watermark_ok_safe(zone, order, |
2418 | high_wmark_pages(zone), 0, 0)) { |
2419 | end_zone = i; |
2420 | break; |
2421 | } else { |
2422 | /* If balanced, clear the congested flag */ |
2423 | zone_clear_flag(zone, ZONE_CONGESTED); |
2424 | } |
2425 | } |
2426 | if (i < 0) |
2427 | goto out; |
2428 | |
2429 | for (i = 0; i <= end_zone; i++) { |
2430 | struct zone *zone = pgdat->node_zones + i; |
2431 | |
2432 | lru_pages += zone_reclaimable_pages(zone); |
2433 | } |
2434 | |
2435 | /* |
2436 | * Now scan the zone in the dma->highmem direction, stopping |
2437 | * at the last zone which needs scanning. |
2438 | * |
2439 | * We do this because the page allocator works in the opposite |
2440 | * direction. This prevents the page allocator from allocating |
2441 | * pages behind kswapd's direction of progress, which would |
2442 | * cause too much scanning of the lower zones. |
2443 | */ |
2444 | for (i = 0; i <= end_zone; i++) { |
2445 | struct zone *zone = pgdat->node_zones + i; |
2446 | int nr_slab, testorder; |
2447 | unsigned long balance_gap; |
2448 | |
2449 | if (!populated_zone(zone)) |
2450 | continue; |
2451 | |
2452 | if (zone->all_unreclaimable && |
2453 | sc.priority != DEF_PRIORITY) |
2454 | continue; |
2455 | |
2456 | sc.nr_scanned = 0; |
2457 | |
2458 | nr_soft_scanned = 0; |
2459 | /* |
2460 | * Call soft limit reclaim before calling shrink_zone. |
2461 | */ |
2462 | nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, |
2463 | order, sc.gfp_mask, |
2464 | &nr_soft_scanned); |
2465 | sc.nr_reclaimed += nr_soft_reclaimed; |
2466 | total_scanned += nr_soft_scanned; |
2467 | |
2468 | /* |
2469 | * We put equal pressure on every zone, unless |
2470 | * one zone has way too many pages free |
2471 | * already. The "too many pages" is defined |
2472 | * as the high wmark plus a "gap" where the |
2473 | * gap is either the low watermark or 1% |
2474 | * of the zone, whichever is smaller. |
2475 | */ |
2476 | balance_gap = min(low_wmark_pages(zone), |
2477 | (zone->present_pages + |
2478 | KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / |
2479 | KSWAPD_ZONE_BALANCE_GAP_RATIO); |
2480 | /* |
2481 | * Kswapd reclaims only single pages with compaction |
2482 | * enabled. Trying too hard to reclaim until contiguous |
2483 | * free pages have become available can hurt performance |
2484 | * by evicting too much useful data from memory. |
2485 | * Do not reclaim more than needed for compaction. |
2486 | */ |
2487 | testorder = order; |
2488 | if (COMPACTION_BUILD && order && |
2489 | compaction_suitable(zone, order) != |
2490 | COMPACT_SKIPPED) |
2491 | testorder = 0; |
2492 | |
2493 | if ((buffer_heads_over_limit && is_highmem_idx(i)) || |
2494 | !zone_watermark_ok_safe(zone, testorder, |
2495 | high_wmark_pages(zone) + balance_gap, |
2496 | end_zone, 0)) { |
2497 | shrink_zone(zone, &sc); |
2498 | |
2499 | reclaim_state->reclaimed_slab = 0; |
2500 | nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages); |
2501 | sc.nr_reclaimed += reclaim_state->reclaimed_slab; |
2502 | total_scanned += sc.nr_scanned; |
2503 | |
2504 | if (nr_slab == 0 && !zone_reclaimable(zone)) |
2505 | zone->all_unreclaimable = 1; |
2506 | } |
2507 | |
2508 | /* |
2509 | * If we've done a decent amount of scanning and |
2510 | * the reclaim ratio is low, start doing writepage |
2511 | * even in laptop mode |
2512 | */ |
2513 | if (total_scanned > SWAP_CLUSTER_MAX * 2 && |
2514 | total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) |
2515 | sc.may_writepage = 1; |
2516 | |
2517 | if (zone->all_unreclaimable) { |
2518 | if (end_zone && end_zone == i) |
2519 | end_zone--; |
2520 | continue; |
2521 | } |
2522 | |
2523 | if (!zone_watermark_ok_safe(zone, testorder, |
2524 | high_wmark_pages(zone), end_zone, 0)) { |
2525 | all_zones_ok = 0; |
2526 | /* |
2527 | * We are still under min water mark. This |
2528 | * means that we have a GFP_ATOMIC allocation |
2529 | * failure risk. Hurry up! |
2530 | */ |
2531 | if (!zone_watermark_ok_safe(zone, order, |
2532 | min_wmark_pages(zone), end_zone, 0)) |
2533 | has_under_min_watermark_zone = 1; |
2534 | } else { |
2535 | /* |
2536 | * If a zone reaches its high watermark, |
2537 | * consider it to be no longer congested. It's |
2538 | * possible there are dirty pages backed by |
2539 | * congested BDIs but as pressure is relieved, |
2540 | * spectulatively avoid congestion waits |
2541 | */ |
2542 | zone_clear_flag(zone, ZONE_CONGESTED); |
2543 | if (i <= *classzone_idx) |
2544 | balanced += zone->present_pages; |
2545 | } |
2546 | |
2547 | } |
2548 | if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) |
2549 | break; /* kswapd: all done */ |
2550 | /* |
2551 | * OK, kswapd is getting into trouble. Take a nap, then take |
2552 | * another pass across the zones. |
2553 | */ |
2554 | if (total_scanned && (sc.priority < DEF_PRIORITY - 2)) { |
2555 | if (has_under_min_watermark_zone) |
2556 | count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); |
2557 | else |
2558 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
2559 | } |
2560 | |
2561 | /* |
2562 | * We do this so kswapd doesn't build up large priorities for |
2563 | * example when it is freeing in parallel with allocators. It |
2564 | * matches the direct reclaim path behaviour in terms of impact |
2565 | * on zone->*_priority. |
2566 | */ |
2567 | if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) |
2568 | break; |
2569 | } while (--sc.priority >= 0); |
2570 | out: |
2571 | |
2572 | /* |
2573 | * order-0: All zones must meet high watermark for a balanced node |
2574 | * high-order: Balanced zones must make up at least 25% of the node |
2575 | * for the node to be balanced |
2576 | */ |
2577 | if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { |
2578 | cond_resched(); |
2579 | |
2580 | try_to_freeze(); |
2581 | |
2582 | /* |
2583 | * Fragmentation may mean that the system cannot be |
2584 | * rebalanced for high-order allocations in all zones. |
2585 | * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, |
2586 | * it means the zones have been fully scanned and are still |
2587 | * not balanced. For high-order allocations, there is |
2588 | * little point trying all over again as kswapd may |
2589 | * infinite loop. |
2590 | * |
2591 | * Instead, recheck all watermarks at order-0 as they |
2592 | * are the most important. If watermarks are ok, kswapd will go |
2593 | * back to sleep. High-order users can still perform direct |
2594 | * reclaim if they wish. |
2595 | */ |
2596 | if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) |
2597 | order = sc.order = 0; |
2598 | |
2599 | goto loop_again; |
2600 | } |
2601 | |
2602 | /* |
2603 | * If kswapd was reclaiming at a higher order, it has the option of |
2604 | * sleeping without all zones being balanced. Before it does, it must |
2605 | * ensure that the watermarks for order-0 on *all* zones are met and |
2606 | * that the congestion flags are cleared. The congestion flag must |
2607 | * be cleared as kswapd is the only mechanism that clears the flag |
2608 | * and it is potentially going to sleep here. |
2609 | */ |
2610 | if (order) { |
2611 | int zones_need_compaction = 1; |
2612 | |
2613 | for (i = 0; i <= end_zone; i++) { |
2614 | struct zone *zone = pgdat->node_zones + i; |
2615 | |
2616 | if (!populated_zone(zone)) |
2617 | continue; |
2618 | |
2619 | if (zone->all_unreclaimable && |
2620 | sc.priority != DEF_PRIORITY) |
2621 | continue; |
2622 | |
2623 | /* Would compaction fail due to lack of free memory? */ |
2624 | if (COMPACTION_BUILD && |
2625 | compaction_suitable(zone, order) == COMPACT_SKIPPED) |
2626 | goto loop_again; |
2627 | |
2628 | /* Confirm the zone is balanced for order-0 */ |
2629 | if (!zone_watermark_ok(zone, 0, |
2630 | high_wmark_pages(zone), 0, 0)) { |
2631 | order = sc.order = 0; |
2632 | goto loop_again; |
2633 | } |
2634 | |
2635 | /* Check if the memory needs to be defragmented. */ |
2636 | if (zone_watermark_ok(zone, order, |
2637 | low_wmark_pages(zone), *classzone_idx, 0)) |
2638 | zones_need_compaction = 0; |
2639 | |
2640 | /* If balanced, clear the congested flag */ |
2641 | zone_clear_flag(zone, ZONE_CONGESTED); |
2642 | } |
2643 | |
2644 | if (zones_need_compaction) |
2645 | compact_pgdat(pgdat, order); |
2646 | } |
2647 | |
2648 | /* |
2649 | * Return the order we were reclaiming at so sleeping_prematurely() |
2650 | * makes a decision on the order we were last reclaiming at. However, |
2651 | * if another caller entered the allocator slow path while kswapd |
2652 | * was awake, order will remain at the higher level |
2653 | */ |
2654 | *classzone_idx = end_zone; |
2655 | return order; |
2656 | } |
2657 | |
2658 | static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) |
2659 | { |
2660 | long remaining = 0; |
2661 | DEFINE_WAIT(wait); |
2662 | |
2663 | if (freezing(current) || kthread_should_stop()) |
2664 | return; |
2665 | |
2666 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
2667 | |
2668 | /* Try to sleep for a short interval */ |
2669 | if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { |
2670 | remaining = schedule_timeout(HZ/10); |
2671 | finish_wait(&pgdat->kswapd_wait, &wait); |
2672 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
2673 | } |
2674 | |
2675 | /* |
2676 | * After a short sleep, check if it was a premature sleep. If not, then |
2677 | * go fully to sleep until explicitly woken up. |
2678 | */ |
2679 | if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { |
2680 | trace_mm_vmscan_kswapd_sleep(pgdat->node_id); |
2681 | |
2682 | /* |
2683 | * vmstat counters are not perfectly accurate and the estimated |
2684 | * value for counters such as NR_FREE_PAGES can deviate from the |
2685 | * true value by nr_online_cpus * threshold. To avoid the zone |
2686 | * watermarks being breached while under pressure, we reduce the |
2687 | * per-cpu vmstat threshold while kswapd is awake and restore |
2688 | * them before going back to sleep. |
2689 | */ |
2690 | set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); |
2691 | |
2692 | if (!kthread_should_stop()) |
2693 | schedule(); |
2694 | |
2695 | set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); |
2696 | } else { |
2697 | if (remaining) |
2698 | count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); |
2699 | else |
2700 | count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); |
2701 | } |
2702 | finish_wait(&pgdat->kswapd_wait, &wait); |
2703 | } |
2704 | |
2705 | /* |
2706 | * The background pageout daemon, started as a kernel thread |
2707 | * from the init process. |
2708 | * |
2709 | * This basically trickles out pages so that we have _some_ |
2710 | * free memory available even if there is no other activity |
2711 | * that frees anything up. This is needed for things like routing |
2712 | * etc, where we otherwise might have all activity going on in |
2713 | * asynchronous contexts that cannot page things out. |
2714 | * |
2715 | * If there are applications that are active memory-allocators |
2716 | * (most normal use), this basically shouldn't matter. |
2717 | */ |
2718 | static int kswapd(void *p) |
2719 | { |
2720 | unsigned long order, new_order; |
2721 | unsigned balanced_order; |
2722 | int classzone_idx, new_classzone_idx; |
2723 | int balanced_classzone_idx; |
2724 | pg_data_t *pgdat = (pg_data_t*)p; |
2725 | struct task_struct *tsk = current; |
2726 | |
2727 | struct reclaim_state reclaim_state = { |
2728 | .reclaimed_slab = 0, |
2729 | }; |
2730 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); |
2731 | |
2732 | lockdep_set_current_reclaim_state(GFP_KERNEL); |
2733 | |
2734 | if (!cpumask_empty(cpumask)) |
2735 | set_cpus_allowed_ptr(tsk, cpumask); |
2736 | current->reclaim_state = &reclaim_state; |
2737 | |
2738 | /* |
2739 | * Tell the memory management that we're a "memory allocator", |
2740 | * and that if we need more memory we should get access to it |
2741 | * regardless (see "__alloc_pages()"). "kswapd" should |
2742 | * never get caught in the normal page freeing logic. |
2743 | * |
2744 | * (Kswapd normally doesn't need memory anyway, but sometimes |
2745 | * you need a small amount of memory in order to be able to |
2746 | * page out something else, and this flag essentially protects |
2747 | * us from recursively trying to free more memory as we're |
2748 | * trying to free the first piece of memory in the first place). |
2749 | */ |
2750 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; |
2751 | set_freezable(); |
2752 | |
2753 | order = new_order = 0; |
2754 | balanced_order = 0; |
2755 | classzone_idx = new_classzone_idx = pgdat->nr_zones - 1; |
2756 | balanced_classzone_idx = classzone_idx; |
2757 | for ( ; ; ) { |
2758 | int ret; |
2759 | |
2760 | /* |
2761 | * If the last balance_pgdat was unsuccessful it's unlikely a |
2762 | * new request of a similar or harder type will succeed soon |
2763 | * so consider going to sleep on the basis we reclaimed at |
2764 | */ |
2765 | if (balanced_classzone_idx >= new_classzone_idx && |
2766 | balanced_order == new_order) { |
2767 | new_order = pgdat->kswapd_max_order; |
2768 | new_classzone_idx = pgdat->classzone_idx; |
2769 | pgdat->kswapd_max_order = 0; |
2770 | pgdat->classzone_idx = pgdat->nr_zones - 1; |
2771 | } |
2772 | |
2773 | if (order < new_order || classzone_idx > new_classzone_idx) { |
2774 | /* |
2775 | * Don't sleep if someone wants a larger 'order' |
2776 | * allocation or has tigher zone constraints |
2777 | */ |
2778 | order = new_order; |
2779 | classzone_idx = new_classzone_idx; |
2780 | } else { |
2781 | kswapd_try_to_sleep(pgdat, balanced_order, |
2782 | balanced_classzone_idx); |
2783 | order = pgdat->kswapd_max_order; |
2784 | classzone_idx = pgdat->classzone_idx; |
2785 | new_order = order; |
2786 | new_classzone_idx = classzone_idx; |
2787 | pgdat->kswapd_max_order = 0; |
2788 | pgdat->classzone_idx = pgdat->nr_zones - 1; |
2789 | } |
2790 | |
2791 | ret = try_to_freeze(); |
2792 | if (kthread_should_stop()) |
2793 | break; |
2794 | |
2795 | /* |
2796 | * We can speed up thawing tasks if we don't call balance_pgdat |
2797 | * after returning from the refrigerator |
2798 | */ |
2799 | if (!ret) { |
2800 | trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); |
2801 | balanced_classzone_idx = classzone_idx; |
2802 | balanced_order = balance_pgdat(pgdat, order, |
2803 | &balanced_classzone_idx); |
2804 | } |
2805 | } |
2806 | return 0; |
2807 | } |
2808 | |
2809 | /* |
2810 | * A zone is low on free memory, so wake its kswapd task to service it. |
2811 | */ |
2812 | void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) |
2813 | { |
2814 | pg_data_t *pgdat; |
2815 | |
2816 | if (!populated_zone(zone)) |
2817 | return; |
2818 | |
2819 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2820 | return; |
2821 | pgdat = zone->zone_pgdat; |
2822 | if (pgdat->kswapd_max_order < order) { |
2823 | pgdat->kswapd_max_order = order; |
2824 | pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); |
2825 | } |
2826 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
2827 | return; |
2828 | if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) |
2829 | return; |
2830 | |
2831 | trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); |
2832 | wake_up_interruptible(&pgdat->kswapd_wait); |
2833 | } |
2834 | |
2835 | /* |
2836 | * The reclaimable count would be mostly accurate. |
2837 | * The less reclaimable pages may be |
2838 | * - mlocked pages, which will be moved to unevictable list when encountered |
2839 | * - mapped pages, which may require several travels to be reclaimed |
2840 | * - dirty pages, which is not "instantly" reclaimable |
2841 | */ |
2842 | unsigned long global_reclaimable_pages(void) |
2843 | { |
2844 | int nr; |
2845 | |
2846 | nr = global_page_state(NR_ACTIVE_FILE) + |
2847 | global_page_state(NR_INACTIVE_FILE); |
2848 | |
2849 | if (nr_swap_pages > 0) |
2850 | nr += global_page_state(NR_ACTIVE_ANON) + |
2851 | global_page_state(NR_INACTIVE_ANON); |
2852 | |
2853 | return nr; |
2854 | } |
2855 | |
2856 | unsigned long zone_reclaimable_pages(struct zone *zone) |
2857 | { |
2858 | int nr; |
2859 | |
2860 | nr = zone_page_state(zone, NR_ACTIVE_FILE) + |
2861 | zone_page_state(zone, NR_INACTIVE_FILE); |
2862 | |
2863 | if (nr_swap_pages > 0) |
2864 | nr += zone_page_state(zone, NR_ACTIVE_ANON) + |
2865 | zone_page_state(zone, NR_INACTIVE_ANON); |
2866 | |
2867 | return nr; |
2868 | } |
2869 | |
2870 | #ifdef CONFIG_HIBERNATION |
2871 | /* |
2872 | * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of |
2873 | * freed pages. |
2874 | * |
2875 | * Rather than trying to age LRUs the aim is to preserve the overall |
2876 | * LRU order by reclaiming preferentially |
2877 | * inactive > active > active referenced > active mapped |
2878 | */ |
2879 | unsigned long shrink_all_memory(unsigned long nr_to_reclaim) |
2880 | { |
2881 | struct reclaim_state reclaim_state; |
2882 | struct scan_control sc = { |
2883 | .gfp_mask = GFP_HIGHUSER_MOVABLE, |
2884 | .may_swap = 1, |
2885 | .may_unmap = 1, |
2886 | .may_writepage = 1, |
2887 | .nr_to_reclaim = nr_to_reclaim, |
2888 | .hibernation_mode = 1, |
2889 | .order = 0, |
2890 | .priority = DEF_PRIORITY, |
2891 | }; |
2892 | struct shrink_control shrink = { |
2893 | .gfp_mask = sc.gfp_mask, |
2894 | }; |
2895 | struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); |
2896 | struct task_struct *p = current; |
2897 | unsigned long nr_reclaimed; |
2898 | |
2899 | p->flags |= PF_MEMALLOC; |
2900 | lockdep_set_current_reclaim_state(sc.gfp_mask); |
2901 | reclaim_state.reclaimed_slab = 0; |
2902 | p->reclaim_state = &reclaim_state; |
2903 | |
2904 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
2905 | |
2906 | p->reclaim_state = NULL; |
2907 | lockdep_clear_current_reclaim_state(); |
2908 | p->flags &= ~PF_MEMALLOC; |
2909 | |
2910 | return nr_reclaimed; |
2911 | } |
2912 | #endif /* CONFIG_HIBERNATION */ |
2913 | |
2914 | /* It's optimal to keep kswapds on the same CPUs as their memory, but |
2915 | not required for correctness. So if the last cpu in a node goes |
2916 | away, we get changed to run anywhere: as the first one comes back, |
2917 | restore their cpu bindings. */ |
2918 | static int __devinit cpu_callback(struct notifier_block *nfb, |
2919 | unsigned long action, void *hcpu) |
2920 | { |
2921 | int nid; |
2922 | |
2923 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { |
2924 | for_each_node_state(nid, N_HIGH_MEMORY) { |
2925 | pg_data_t *pgdat = NODE_DATA(nid); |
2926 | const struct cpumask *mask; |
2927 | |
2928 | mask = cpumask_of_node(pgdat->node_id); |
2929 | |
2930 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
2931 | /* One of our CPUs online: restore mask */ |
2932 | set_cpus_allowed_ptr(pgdat->kswapd, mask); |
2933 | } |
2934 | } |
2935 | return NOTIFY_OK; |
2936 | } |
2937 | |
2938 | /* |
2939 | * This kswapd start function will be called by init and node-hot-add. |
2940 | * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. |
2941 | */ |
2942 | int kswapd_run(int nid) |
2943 | { |
2944 | pg_data_t *pgdat = NODE_DATA(nid); |
2945 | int ret = 0; |
2946 | |
2947 | if (pgdat->kswapd) |
2948 | return 0; |
2949 | |
2950 | pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); |
2951 | if (IS_ERR(pgdat->kswapd)) { |
2952 | /* failure at boot is fatal */ |
2953 | BUG_ON(system_state == SYSTEM_BOOTING); |
2954 | printk("Failed to start kswapd on node %d\n",nid); |
2955 | ret = -1; |
2956 | } |
2957 | return ret; |
2958 | } |
2959 | |
2960 | /* |
2961 | * Called by memory hotplug when all memory in a node is offlined. Caller must |
2962 | * hold lock_memory_hotplug(). |
2963 | */ |
2964 | void kswapd_stop(int nid) |
2965 | { |
2966 | struct task_struct *kswapd = NODE_DATA(nid)->kswapd; |
2967 | |
2968 | if (kswapd) { |
2969 | kthread_stop(kswapd); |
2970 | NODE_DATA(nid)->kswapd = NULL; |
2971 | } |
2972 | } |
2973 | |
2974 | static int __init kswapd_init(void) |
2975 | { |
2976 | int nid; |
2977 | |
2978 | swap_setup(); |
2979 | for_each_node_state(nid, N_HIGH_MEMORY) |
2980 | kswapd_run(nid); |
2981 | hotcpu_notifier(cpu_callback, 0); |
2982 | return 0; |
2983 | } |
2984 | |
2985 | module_init(kswapd_init) |
2986 | |
2987 | #ifdef CONFIG_NUMA |
2988 | /* |
2989 | * Zone reclaim mode |
2990 | * |
2991 | * If non-zero call zone_reclaim when the number of free pages falls below |
2992 | * the watermarks. |
2993 | */ |
2994 | int zone_reclaim_mode __read_mostly; |
2995 | |
2996 | #define RECLAIM_OFF 0 |
2997 | #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ |
2998 | #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ |
2999 | #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ |
3000 | |
3001 | /* |
3002 | * Priority for ZONE_RECLAIM. This determines the fraction of pages |
3003 | * of a node considered for each zone_reclaim. 4 scans 1/16th of |
3004 | * a zone. |
3005 | */ |
3006 | #define ZONE_RECLAIM_PRIORITY 4 |
3007 | |
3008 | /* |
3009 | * Percentage of pages in a zone that must be unmapped for zone_reclaim to |
3010 | * occur. |
3011 | */ |
3012 | int sysctl_min_unmapped_ratio = 1; |
3013 | |
3014 | /* |
3015 | * If the number of slab pages in a zone grows beyond this percentage then |
3016 | * slab reclaim needs to occur. |
3017 | */ |
3018 | int sysctl_min_slab_ratio = 5; |
3019 | |
3020 | static inline unsigned long zone_unmapped_file_pages(struct zone *zone) |
3021 | { |
3022 | unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); |
3023 | unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + |
3024 | zone_page_state(zone, NR_ACTIVE_FILE); |
3025 | |
3026 | /* |
3027 | * It's possible for there to be more file mapped pages than |
3028 | * accounted for by the pages on the file LRU lists because |
3029 | * tmpfs pages accounted for as ANON can also be FILE_MAPPED |
3030 | */ |
3031 | return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; |
3032 | } |
3033 | |
3034 | /* Work out how many page cache pages we can reclaim in this reclaim_mode */ |
3035 | static long zone_pagecache_reclaimable(struct zone *zone) |
3036 | { |
3037 | long nr_pagecache_reclaimable; |
3038 | long delta = 0; |
3039 | |
3040 | /* |
3041 | * If RECLAIM_SWAP is set, then all file pages are considered |
3042 | * potentially reclaimable. Otherwise, we have to worry about |
3043 | * pages like swapcache and zone_unmapped_file_pages() provides |
3044 | * a better estimate |
3045 | */ |
3046 | if (zone_reclaim_mode & RECLAIM_SWAP) |
3047 | nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); |
3048 | else |
3049 | nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); |
3050 | |
3051 | /* If we can't clean pages, remove dirty pages from consideration */ |
3052 | if (!(zone_reclaim_mode & RECLAIM_WRITE)) |
3053 | delta += zone_page_state(zone, NR_FILE_DIRTY); |
3054 | |
3055 | /* Watch for any possible underflows due to delta */ |
3056 | if (unlikely(delta > nr_pagecache_reclaimable)) |
3057 | delta = nr_pagecache_reclaimable; |
3058 | |
3059 | return nr_pagecache_reclaimable - delta; |
3060 | } |
3061 | |
3062 | /* |
3063 | * Try to free up some pages from this zone through reclaim. |
3064 | */ |
3065 | static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
3066 | { |
3067 | /* Minimum pages needed in order to stay on node */ |
3068 | const unsigned long nr_pages = 1 << order; |
3069 | struct task_struct *p = current; |
3070 | struct reclaim_state reclaim_state; |
3071 | struct scan_control sc = { |
3072 | .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), |
3073 | .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), |
3074 | .may_swap = 1, |
3075 | .nr_to_reclaim = max_t(unsigned long, nr_pages, |
3076 | SWAP_CLUSTER_MAX), |
3077 | .gfp_mask = gfp_mask, |
3078 | .order = order, |
3079 | .priority = ZONE_RECLAIM_PRIORITY, |
3080 | }; |
3081 | struct shrink_control shrink = { |
3082 | .gfp_mask = sc.gfp_mask, |
3083 | }; |
3084 | unsigned long nr_slab_pages0, nr_slab_pages1; |
3085 | |
3086 | cond_resched(); |
3087 | /* |
3088 | * We need to be able to allocate from the reserves for RECLAIM_SWAP |
3089 | * and we also need to be able to write out pages for RECLAIM_WRITE |
3090 | * and RECLAIM_SWAP. |
3091 | */ |
3092 | p->flags |= PF_MEMALLOC | PF_SWAPWRITE; |
3093 | lockdep_set_current_reclaim_state(gfp_mask); |
3094 | reclaim_state.reclaimed_slab = 0; |
3095 | p->reclaim_state = &reclaim_state; |
3096 | |
3097 | if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { |
3098 | /* |
3099 | * Free memory by calling shrink zone with increasing |
3100 | * priorities until we have enough memory freed. |
3101 | */ |
3102 | do { |
3103 | shrink_zone(zone, &sc); |
3104 | } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0); |
3105 | } |
3106 | |
3107 | nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
3108 | if (nr_slab_pages0 > zone->min_slab_pages) { |
3109 | /* |
3110 | * shrink_slab() does not currently allow us to determine how |
3111 | * many pages were freed in this zone. So we take the current |
3112 | * number of slab pages and shake the slab until it is reduced |
3113 | * by the same nr_pages that we used for reclaiming unmapped |
3114 | * pages. |
3115 | * |
3116 | * Note that shrink_slab will free memory on all zones and may |
3117 | * take a long time. |
3118 | */ |
3119 | for (;;) { |
3120 | unsigned long lru_pages = zone_reclaimable_pages(zone); |
3121 | |
3122 | /* No reclaimable slab or very low memory pressure */ |
3123 | if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages)) |
3124 | break; |
3125 | |
3126 | /* Freed enough memory */ |
3127 | nr_slab_pages1 = zone_page_state(zone, |
3128 | NR_SLAB_RECLAIMABLE); |
3129 | if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) |
3130 | break; |
3131 | } |
3132 | |
3133 | /* |
3134 | * Update nr_reclaimed by the number of slab pages we |
3135 | * reclaimed from this zone. |
3136 | */ |
3137 | nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
3138 | if (nr_slab_pages1 < nr_slab_pages0) |
3139 | sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; |
3140 | } |
3141 | |
3142 | p->reclaim_state = NULL; |
3143 | current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); |
3144 | lockdep_clear_current_reclaim_state(); |
3145 | return sc.nr_reclaimed >= nr_pages; |
3146 | } |
3147 | |
3148 | int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
3149 | { |
3150 | int node_id; |
3151 | int ret; |
3152 | |
3153 | /* |
3154 | * Zone reclaim reclaims unmapped file backed pages and |
3155 | * slab pages if we are over the defined limits. |
3156 | * |
3157 | * A small portion of unmapped file backed pages is needed for |
3158 | * file I/O otherwise pages read by file I/O will be immediately |
3159 | * thrown out if the zone is overallocated. So we do not reclaim |
3160 | * if less than a specified percentage of the zone is used by |
3161 | * unmapped file backed pages. |
3162 | */ |
3163 | if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && |
3164 | zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) |
3165 | return ZONE_RECLAIM_FULL; |
3166 | |
3167 | if (zone->all_unreclaimable) |
3168 | return ZONE_RECLAIM_FULL; |
3169 | |
3170 | /* |
3171 | * Do not scan if the allocation should not be delayed. |
3172 | */ |
3173 | if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) |
3174 | return ZONE_RECLAIM_NOSCAN; |
3175 | |
3176 | /* |
3177 | * Only run zone reclaim on the local zone or on zones that do not |
3178 | * have associated processors. This will favor the local processor |
3179 | * over remote processors and spread off node memory allocations |
3180 | * as wide as possible. |
3181 | */ |
3182 | node_id = zone_to_nid(zone); |
3183 | if (node_state(node_id, N_CPU) && node_id != numa_node_id()) |
3184 | return ZONE_RECLAIM_NOSCAN; |
3185 | |
3186 | if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) |
3187 | return ZONE_RECLAIM_NOSCAN; |
3188 | |
3189 | ret = __zone_reclaim(zone, gfp_mask, order); |
3190 | zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); |
3191 | |
3192 | if (!ret) |
3193 | count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); |
3194 | |
3195 | return ret; |
3196 | } |
3197 | #endif |
3198 | |
3199 | /* |
3200 | * page_evictable - test whether a page is evictable |
3201 | * @page: the page to test |
3202 | * @vma: the VMA in which the page is or will be mapped, may be NULL |
3203 | * |
3204 | * Test whether page is evictable--i.e., should be placed on active/inactive |
3205 | * lists vs unevictable list. The vma argument is !NULL when called from the |
3206 | * fault path to determine how to instantate a new page. |
3207 | * |
3208 | * Reasons page might not be evictable: |
3209 | * (1) page's mapping marked unevictable |
3210 | * (2) page is part of an mlocked VMA |
3211 | * |
3212 | */ |
3213 | int page_evictable(struct page *page, struct vm_area_struct *vma) |
3214 | { |
3215 | |
3216 | if (mapping_unevictable(page_mapping(page))) |
3217 | return 0; |
3218 | |
3219 | if (PageMlocked(page) || (vma && mlocked_vma_newpage(vma, page))) |
3220 | return 0; |
3221 | |
3222 | return 1; |
3223 | } |
3224 | |
3225 | #ifdef CONFIG_SHMEM |
3226 | /** |
3227 | * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list |
3228 | * @pages: array of pages to check |
3229 | * @nr_pages: number of pages to check |
3230 | * |
3231 | * Checks pages for evictability and moves them to the appropriate lru list. |
3232 | * |
3233 | * This function is only used for SysV IPC SHM_UNLOCK. |
3234 | */ |
3235 | void check_move_unevictable_pages(struct page **pages, int nr_pages) |
3236 | { |
3237 | struct lruvec *lruvec; |
3238 | struct zone *zone = NULL; |
3239 | int pgscanned = 0; |
3240 | int pgrescued = 0; |
3241 | int i; |
3242 | |
3243 | for (i = 0; i < nr_pages; i++) { |
3244 | struct page *page = pages[i]; |
3245 | struct zone *pagezone; |
3246 | |
3247 | pgscanned++; |
3248 | pagezone = page_zone(page); |
3249 | if (pagezone != zone) { |
3250 | if (zone) |
3251 | spin_unlock_irq(&zone->lru_lock); |
3252 | zone = pagezone; |
3253 | spin_lock_irq(&zone->lru_lock); |
3254 | } |
3255 | lruvec = mem_cgroup_page_lruvec(page, zone); |
3256 | |
3257 | if (!PageLRU(page) || !PageUnevictable(page)) |
3258 | continue; |
3259 | |
3260 | if (page_evictable(page, NULL)) { |
3261 | enum lru_list lru = page_lru_base_type(page); |
3262 | |
3263 | VM_BUG_ON(PageActive(page)); |
3264 | ClearPageUnevictable(page); |
3265 | del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE); |
3266 | add_page_to_lru_list(page, lruvec, lru); |
3267 | pgrescued++; |
3268 | } |
3269 | } |
3270 | |
3271 | if (zone) { |
3272 | __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued); |
3273 | __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned); |
3274 | spin_unlock_irq(&zone->lru_lock); |
3275 | } |
3276 | } |
3277 | #endif /* CONFIG_SHMEM */ |
3278 | |
3279 | static void warn_scan_unevictable_pages(void) |
3280 | { |
3281 | printk_once(KERN_WARNING |
3282 | "%s: The scan_unevictable_pages sysctl/node-interface has been " |
3283 | "disabled for lack of a legitimate use case. If you have " |
3284 | "one, please send an email to linux-mm@kvack.org.\n", |
3285 | current->comm); |
3286 | } |
3287 | |
3288 | /* |
3289 | * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of |
3290 | * all nodes' unevictable lists for evictable pages |
3291 | */ |
3292 | unsigned long scan_unevictable_pages; |
3293 | |
3294 | int scan_unevictable_handler(struct ctl_table *table, int write, |
3295 | void __user *buffer, |
3296 | size_t *length, loff_t *ppos) |
3297 | { |
3298 | warn_scan_unevictable_pages(); |
3299 | proc_doulongvec_minmax(table, write, buffer, length, ppos); |
3300 | scan_unevictable_pages = 0; |
3301 | return 0; |
3302 | } |
3303 | |
3304 | #ifdef CONFIG_NUMA |
3305 | /* |
3306 | * per node 'scan_unevictable_pages' attribute. On demand re-scan of |
3307 | * a specified node's per zone unevictable lists for evictable pages. |
3308 | */ |
3309 | |
3310 | static ssize_t read_scan_unevictable_node(struct device *dev, |
3311 | struct device_attribute *attr, |
3312 | char *buf) |
3313 | { |
3314 | warn_scan_unevictable_pages(); |
3315 | return sprintf(buf, "0\n"); /* always zero; should fit... */ |
3316 | } |
3317 | |
3318 | static ssize_t write_scan_unevictable_node(struct device *dev, |
3319 | struct device_attribute *attr, |
3320 | const char *buf, size_t count) |
3321 | { |
3322 | warn_scan_unevictable_pages(); |
3323 | return 1; |
3324 | } |
3325 | |
3326 | |
3327 | static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, |
3328 | read_scan_unevictable_node, |
3329 | write_scan_unevictable_node); |
3330 | |
3331 | int scan_unevictable_register_node(struct node *node) |
3332 | { |
3333 | return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages); |
3334 | } |
3335 | |
3336 | void scan_unevictable_unregister_node(struct node *node) |
3337 | { |
3338 | device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages); |
3339 | } |
3340 | #endif |
3341 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9