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Commit | Line | Data |
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1da177e4 LT |
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> | |
5a0e3ad6 | 16 | #include <linux/gfp.h> |
1da177e4 LT |
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> | |
70ddf637 | 22 | #include <linux/vmpressure.h> |
e129b5c2 | 23 | #include <linux/vmstat.h> |
1da177e4 LT |
24 | #include <linux/file.h> |
25 | #include <linux/writeback.h> | |
26 | #include <linux/blkdev.h> | |
27 | #include <linux/buffer_head.h> /* for try_to_release_page(), | |
28 | buffer_heads_over_limit */ | |
29 | #include <linux/mm_inline.h> | |
1da177e4 LT |
30 | #include <linux/backing-dev.h> |
31 | #include <linux/rmap.h> | |
32 | #include <linux/topology.h> | |
33 | #include <linux/cpu.h> | |
34 | #include <linux/cpuset.h> | |
3e7d3449 | 35 | #include <linux/compaction.h> |
1da177e4 LT |
36 | #include <linux/notifier.h> |
37 | #include <linux/rwsem.h> | |
248a0301 | 38 | #include <linux/delay.h> |
3218ae14 | 39 | #include <linux/kthread.h> |
7dfb7103 | 40 | #include <linux/freezer.h> |
66e1707b | 41 | #include <linux/memcontrol.h> |
873b4771 | 42 | #include <linux/delayacct.h> |
af936a16 | 43 | #include <linux/sysctl.h> |
929bea7c | 44 | #include <linux/oom.h> |
268bb0ce | 45 | #include <linux/prefetch.h> |
1da177e4 LT |
46 | |
47 | #include <asm/tlbflush.h> | |
48 | #include <asm/div64.h> | |
49 | ||
50 | #include <linux/swapops.h> | |
51 | ||
0f8053a5 NP |
52 | #include "internal.h" |
53 | ||
33906bc5 MG |
54 | #define CREATE_TRACE_POINTS |
55 | #include <trace/events/vmscan.h> | |
56 | ||
1da177e4 | 57 | struct scan_control { |
1da177e4 LT |
58 | /* Incremented by the number of inactive pages that were scanned */ |
59 | unsigned long nr_scanned; | |
60 | ||
a79311c1 RR |
61 | /* Number of pages freed so far during a call to shrink_zones() */ |
62 | unsigned long nr_reclaimed; | |
63 | ||
22fba335 KM |
64 | /* How many pages shrink_list() should reclaim */ |
65 | unsigned long nr_to_reclaim; | |
66 | ||
7b51755c KM |
67 | unsigned long hibernation_mode; |
68 | ||
1da177e4 | 69 | /* This context's GFP mask */ |
6daa0e28 | 70 | gfp_t gfp_mask; |
1da177e4 LT |
71 | |
72 | int may_writepage; | |
73 | ||
a6dc60f8 JW |
74 | /* Can mapped pages be reclaimed? */ |
75 | int may_unmap; | |
f1fd1067 | 76 | |
2e2e4259 KM |
77 | /* Can pages be swapped as part of reclaim? */ |
78 | int may_swap; | |
79 | ||
5ad333eb | 80 | int order; |
66e1707b | 81 | |
9e3b2f8c KK |
82 | /* Scan (total_size >> priority) pages at once */ |
83 | int priority; | |
84 | ||
f16015fb JW |
85 | /* |
86 | * The memory cgroup that hit its limit and as a result is the | |
87 | * primary target of this reclaim invocation. | |
88 | */ | |
89 | struct mem_cgroup *target_mem_cgroup; | |
66e1707b | 90 | |
327c0e96 KH |
91 | /* |
92 | * Nodemask of nodes allowed by the caller. If NULL, all nodes | |
93 | * are scanned. | |
94 | */ | |
95 | nodemask_t *nodemask; | |
1da177e4 LT |
96 | }; |
97 | ||
1da177e4 LT |
98 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) |
99 | ||
100 | #ifdef ARCH_HAS_PREFETCH | |
101 | #define prefetch_prev_lru_page(_page, _base, _field) \ | |
102 | do { \ | |
103 | if ((_page)->lru.prev != _base) { \ | |
104 | struct page *prev; \ | |
105 | \ | |
106 | prev = lru_to_page(&(_page->lru)); \ | |
107 | prefetch(&prev->_field); \ | |
108 | } \ | |
109 | } while (0) | |
110 | #else | |
111 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) | |
112 | #endif | |
113 | ||
114 | #ifdef ARCH_HAS_PREFETCHW | |
115 | #define prefetchw_prev_lru_page(_page, _base, _field) \ | |
116 | do { \ | |
117 | if ((_page)->lru.prev != _base) { \ | |
118 | struct page *prev; \ | |
119 | \ | |
120 | prev = lru_to_page(&(_page->lru)); \ | |
121 | prefetchw(&prev->_field); \ | |
122 | } \ | |
123 | } while (0) | |
124 | #else | |
125 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) | |
126 | #endif | |
127 | ||
128 | /* | |
129 | * From 0 .. 100. Higher means more swappy. | |
130 | */ | |
131 | int vm_swappiness = 60; | |
b21e0b90 | 132 | unsigned long vm_total_pages; /* The total number of pages which the VM controls */ |
1da177e4 LT |
133 | |
134 | static LIST_HEAD(shrinker_list); | |
135 | static DECLARE_RWSEM(shrinker_rwsem); | |
136 | ||
c255a458 | 137 | #ifdef CONFIG_MEMCG |
89b5fae5 JW |
138 | static bool global_reclaim(struct scan_control *sc) |
139 | { | |
f16015fb | 140 | return !sc->target_mem_cgroup; |
89b5fae5 | 141 | } |
3b38722e MH |
142 | |
143 | static bool mem_cgroup_should_soft_reclaim(struct scan_control *sc) | |
144 | { | |
e839b6a1 MH |
145 | struct mem_cgroup *root = sc->target_mem_cgroup; |
146 | return !mem_cgroup_disabled() && | |
147 | mem_cgroup_soft_reclaim_eligible(root, root) != SKIP_TREE; | |
3b38722e | 148 | } |
91a45470 | 149 | #else |
89b5fae5 JW |
150 | static bool global_reclaim(struct scan_control *sc) |
151 | { | |
152 | return true; | |
153 | } | |
3b38722e MH |
154 | |
155 | static bool mem_cgroup_should_soft_reclaim(struct scan_control *sc) | |
156 | { | |
157 | return false; | |
158 | } | |
91a45470 KH |
159 | #endif |
160 | ||
6e543d57 LD |
161 | unsigned long zone_reclaimable_pages(struct zone *zone) |
162 | { | |
163 | int nr; | |
164 | ||
165 | nr = zone_page_state(zone, NR_ACTIVE_FILE) + | |
166 | zone_page_state(zone, NR_INACTIVE_FILE); | |
167 | ||
168 | if (get_nr_swap_pages() > 0) | |
169 | nr += zone_page_state(zone, NR_ACTIVE_ANON) + | |
170 | zone_page_state(zone, NR_INACTIVE_ANON); | |
171 | ||
172 | return nr; | |
173 | } | |
174 | ||
175 | bool zone_reclaimable(struct zone *zone) | |
176 | { | |
177 | return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; | |
178 | } | |
179 | ||
4d7dcca2 | 180 | static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru) |
c9f299d9 | 181 | { |
c3c787e8 | 182 | if (!mem_cgroup_disabled()) |
4d7dcca2 | 183 | return mem_cgroup_get_lru_size(lruvec, lru); |
a3d8e054 | 184 | |
074291fe | 185 | return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru); |
c9f299d9 KM |
186 | } |
187 | ||
1da177e4 | 188 | /* |
1d3d4437 | 189 | * Add a shrinker callback to be called from the vm. |
1da177e4 | 190 | */ |
1d3d4437 | 191 | int register_shrinker(struct shrinker *shrinker) |
1da177e4 | 192 | { |
1d3d4437 GC |
193 | size_t size = sizeof(*shrinker->nr_deferred); |
194 | ||
195 | /* | |
196 | * If we only have one possible node in the system anyway, save | |
197 | * ourselves the trouble and disable NUMA aware behavior. This way we | |
198 | * will save memory and some small loop time later. | |
199 | */ | |
200 | if (nr_node_ids == 1) | |
201 | shrinker->flags &= ~SHRINKER_NUMA_AWARE; | |
202 | ||
203 | if (shrinker->flags & SHRINKER_NUMA_AWARE) | |
204 | size *= nr_node_ids; | |
205 | ||
206 | shrinker->nr_deferred = kzalloc(size, GFP_KERNEL); | |
207 | if (!shrinker->nr_deferred) | |
208 | return -ENOMEM; | |
209 | ||
8e1f936b RR |
210 | down_write(&shrinker_rwsem); |
211 | list_add_tail(&shrinker->list, &shrinker_list); | |
212 | up_write(&shrinker_rwsem); | |
1d3d4437 | 213 | return 0; |
1da177e4 | 214 | } |
8e1f936b | 215 | EXPORT_SYMBOL(register_shrinker); |
1da177e4 LT |
216 | |
217 | /* | |
218 | * Remove one | |
219 | */ | |
8e1f936b | 220 | void unregister_shrinker(struct shrinker *shrinker) |
1da177e4 LT |
221 | { |
222 | down_write(&shrinker_rwsem); | |
223 | list_del(&shrinker->list); | |
224 | up_write(&shrinker_rwsem); | |
1da177e4 | 225 | } |
8e1f936b | 226 | EXPORT_SYMBOL(unregister_shrinker); |
1da177e4 LT |
227 | |
228 | #define SHRINK_BATCH 128 | |
1d3d4437 GC |
229 | |
230 | static unsigned long | |
231 | shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker, | |
232 | unsigned long nr_pages_scanned, unsigned long lru_pages) | |
233 | { | |
234 | unsigned long freed = 0; | |
235 | unsigned long long delta; | |
236 | long total_scan; | |
237 | long max_pass; | |
238 | long nr; | |
239 | long new_nr; | |
240 | int nid = shrinkctl->nid; | |
241 | long batch_size = shrinker->batch ? shrinker->batch | |
242 | : SHRINK_BATCH; | |
243 | ||
a0b02131 | 244 | max_pass = shrinker->count_objects(shrinker, shrinkctl); |
1d3d4437 GC |
245 | if (max_pass == 0) |
246 | return 0; | |
247 | ||
248 | /* | |
249 | * copy the current shrinker scan count into a local variable | |
250 | * and zero it so that other concurrent shrinker invocations | |
251 | * don't also do this scanning work. | |
252 | */ | |
253 | nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0); | |
254 | ||
255 | total_scan = nr; | |
256 | delta = (4 * nr_pages_scanned) / shrinker->seeks; | |
257 | delta *= max_pass; | |
258 | do_div(delta, lru_pages + 1); | |
259 | total_scan += delta; | |
260 | if (total_scan < 0) { | |
261 | printk(KERN_ERR | |
262 | "shrink_slab: %pF negative objects to delete nr=%ld\n", | |
a0b02131 | 263 | shrinker->scan_objects, total_scan); |
1d3d4437 GC |
264 | total_scan = max_pass; |
265 | } | |
266 | ||
267 | /* | |
268 | * We need to avoid excessive windup on filesystem shrinkers | |
269 | * due to large numbers of GFP_NOFS allocations causing the | |
270 | * shrinkers to return -1 all the time. This results in a large | |
271 | * nr being built up so when a shrink that can do some work | |
272 | * comes along it empties the entire cache due to nr >>> | |
273 | * max_pass. This is bad for sustaining a working set in | |
274 | * memory. | |
275 | * | |
276 | * Hence only allow the shrinker to scan the entire cache when | |
277 | * a large delta change is calculated directly. | |
278 | */ | |
279 | if (delta < max_pass / 4) | |
280 | total_scan = min(total_scan, max_pass / 2); | |
281 | ||
282 | /* | |
283 | * Avoid risking looping forever due to too large nr value: | |
284 | * never try to free more than twice the estimate number of | |
285 | * freeable entries. | |
286 | */ | |
287 | if (total_scan > max_pass * 2) | |
288 | total_scan = max_pass * 2; | |
289 | ||
290 | trace_mm_shrink_slab_start(shrinker, shrinkctl, nr, | |
291 | nr_pages_scanned, lru_pages, | |
292 | max_pass, delta, total_scan); | |
293 | ||
294 | while (total_scan >= batch_size) { | |
a0b02131 | 295 | unsigned long ret; |
1d3d4437 | 296 | |
a0b02131 DC |
297 | shrinkctl->nr_to_scan = batch_size; |
298 | ret = shrinker->scan_objects(shrinker, shrinkctl); | |
299 | if (ret == SHRINK_STOP) | |
300 | break; | |
301 | freed += ret; | |
1d3d4437 GC |
302 | |
303 | count_vm_events(SLABS_SCANNED, batch_size); | |
304 | total_scan -= batch_size; | |
305 | ||
306 | cond_resched(); | |
307 | } | |
308 | ||
309 | /* | |
310 | * move the unused scan count back into the shrinker in a | |
311 | * manner that handles concurrent updates. If we exhausted the | |
312 | * scan, there is no need to do an update. | |
313 | */ | |
314 | if (total_scan > 0) | |
315 | new_nr = atomic_long_add_return(total_scan, | |
316 | &shrinker->nr_deferred[nid]); | |
317 | else | |
318 | new_nr = atomic_long_read(&shrinker->nr_deferred[nid]); | |
319 | ||
320 | trace_mm_shrink_slab_end(shrinker, freed, nr, new_nr); | |
321 | return freed; | |
1495f230 YH |
322 | } |
323 | ||
1da177e4 LT |
324 | /* |
325 | * Call the shrink functions to age shrinkable caches | |
326 | * | |
327 | * Here we assume it costs one seek to replace a lru page and that it also | |
328 | * takes a seek to recreate a cache object. With this in mind we age equal | |
329 | * percentages of the lru and ageable caches. This should balance the seeks | |
330 | * generated by these structures. | |
331 | * | |
183ff22b | 332 | * If the vm encountered mapped pages on the LRU it increase the pressure on |
1da177e4 LT |
333 | * slab to avoid swapping. |
334 | * | |
335 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. | |
336 | * | |
337 | * `lru_pages' represents the number of on-LRU pages in all the zones which | |
338 | * are eligible for the caller's allocation attempt. It is used for balancing | |
339 | * slab reclaim versus page reclaim. | |
b15e0905 | 340 | * |
341 | * Returns the number of slab objects which we shrunk. | |
1da177e4 | 342 | */ |
24f7c6b9 | 343 | unsigned long shrink_slab(struct shrink_control *shrinkctl, |
1495f230 | 344 | unsigned long nr_pages_scanned, |
a09ed5e0 | 345 | unsigned long lru_pages) |
1da177e4 LT |
346 | { |
347 | struct shrinker *shrinker; | |
24f7c6b9 | 348 | unsigned long freed = 0; |
1da177e4 | 349 | |
1495f230 YH |
350 | if (nr_pages_scanned == 0) |
351 | nr_pages_scanned = SWAP_CLUSTER_MAX; | |
1da177e4 | 352 | |
f06590bd | 353 | if (!down_read_trylock(&shrinker_rwsem)) { |
24f7c6b9 DC |
354 | /* |
355 | * If we would return 0, our callers would understand that we | |
356 | * have nothing else to shrink and give up trying. By returning | |
357 | * 1 we keep it going and assume we'll be able to shrink next | |
358 | * time. | |
359 | */ | |
360 | freed = 1; | |
f06590bd MK |
361 | goto out; |
362 | } | |
1da177e4 LT |
363 | |
364 | list_for_each_entry(shrinker, &shrinker_list, list) { | |
1d3d4437 GC |
365 | for_each_node_mask(shrinkctl->nid, shrinkctl->nodes_to_scan) { |
366 | if (!node_online(shrinkctl->nid)) | |
367 | continue; | |
1da177e4 | 368 | |
1d3d4437 GC |
369 | if (!(shrinker->flags & SHRINKER_NUMA_AWARE) && |
370 | (shrinkctl->nid != 0)) | |
1da177e4 | 371 | break; |
1da177e4 | 372 | |
1d3d4437 GC |
373 | freed += shrink_slab_node(shrinkctl, shrinker, |
374 | nr_pages_scanned, lru_pages); | |
1da177e4 | 375 | |
1da177e4 | 376 | } |
1da177e4 LT |
377 | } |
378 | up_read(&shrinker_rwsem); | |
f06590bd MK |
379 | out: |
380 | cond_resched(); | |
24f7c6b9 | 381 | return freed; |
1da177e4 LT |
382 | } |
383 | ||
1da177e4 LT |
384 | static inline int is_page_cache_freeable(struct page *page) |
385 | { | |
ceddc3a5 JW |
386 | /* |
387 | * A freeable page cache page is referenced only by the caller | |
388 | * that isolated the page, the page cache radix tree and | |
389 | * optional buffer heads at page->private. | |
390 | */ | |
edcf4748 | 391 | return page_count(page) - page_has_private(page) == 2; |
1da177e4 LT |
392 | } |
393 | ||
7d3579e8 KM |
394 | static int may_write_to_queue(struct backing_dev_info *bdi, |
395 | struct scan_control *sc) | |
1da177e4 | 396 | { |
930d9152 | 397 | if (current->flags & PF_SWAPWRITE) |
1da177e4 LT |
398 | return 1; |
399 | if (!bdi_write_congested(bdi)) | |
400 | return 1; | |
401 | if (bdi == current->backing_dev_info) | |
402 | return 1; | |
403 | return 0; | |
404 | } | |
405 | ||
406 | /* | |
407 | * We detected a synchronous write error writing a page out. Probably | |
408 | * -ENOSPC. We need to propagate that into the address_space for a subsequent | |
409 | * fsync(), msync() or close(). | |
410 | * | |
411 | * The tricky part is that after writepage we cannot touch the mapping: nothing | |
412 | * prevents it from being freed up. But we have a ref on the page and once | |
413 | * that page is locked, the mapping is pinned. | |
414 | * | |
415 | * We're allowed to run sleeping lock_page() here because we know the caller has | |
416 | * __GFP_FS. | |
417 | */ | |
418 | static void handle_write_error(struct address_space *mapping, | |
419 | struct page *page, int error) | |
420 | { | |
7eaceacc | 421 | lock_page(page); |
3e9f45bd GC |
422 | if (page_mapping(page) == mapping) |
423 | mapping_set_error(mapping, error); | |
1da177e4 LT |
424 | unlock_page(page); |
425 | } | |
426 | ||
04e62a29 CL |
427 | /* possible outcome of pageout() */ |
428 | typedef enum { | |
429 | /* failed to write page out, page is locked */ | |
430 | PAGE_KEEP, | |
431 | /* move page to the active list, page is locked */ | |
432 | PAGE_ACTIVATE, | |
433 | /* page has been sent to the disk successfully, page is unlocked */ | |
434 | PAGE_SUCCESS, | |
435 | /* page is clean and locked */ | |
436 | PAGE_CLEAN, | |
437 | } pageout_t; | |
438 | ||
1da177e4 | 439 | /* |
1742f19f AM |
440 | * pageout is called by shrink_page_list() for each dirty page. |
441 | * Calls ->writepage(). | |
1da177e4 | 442 | */ |
c661b078 | 443 | static pageout_t pageout(struct page *page, struct address_space *mapping, |
7d3579e8 | 444 | struct scan_control *sc) |
1da177e4 LT |
445 | { |
446 | /* | |
447 | * If the page is dirty, only perform writeback if that write | |
448 | * will be non-blocking. To prevent this allocation from being | |
449 | * stalled by pagecache activity. But note that there may be | |
450 | * stalls if we need to run get_block(). We could test | |
451 | * PagePrivate for that. | |
452 | * | |
6aceb53b | 453 | * If this process is currently in __generic_file_aio_write() against |
1da177e4 LT |
454 | * this page's queue, we can perform writeback even if that |
455 | * will block. | |
456 | * | |
457 | * If the page is swapcache, write it back even if that would | |
458 | * block, for some throttling. This happens by accident, because | |
459 | * swap_backing_dev_info is bust: it doesn't reflect the | |
460 | * congestion state of the swapdevs. Easy to fix, if needed. | |
1da177e4 LT |
461 | */ |
462 | if (!is_page_cache_freeable(page)) | |
463 | return PAGE_KEEP; | |
464 | if (!mapping) { | |
465 | /* | |
466 | * Some data journaling orphaned pages can have | |
467 | * page->mapping == NULL while being dirty with clean buffers. | |
468 | */ | |
266cf658 | 469 | if (page_has_private(page)) { |
1da177e4 LT |
470 | if (try_to_free_buffers(page)) { |
471 | ClearPageDirty(page); | |
d40cee24 | 472 | printk("%s: orphaned page\n", __func__); |
1da177e4 LT |
473 | return PAGE_CLEAN; |
474 | } | |
475 | } | |
476 | return PAGE_KEEP; | |
477 | } | |
478 | if (mapping->a_ops->writepage == NULL) | |
479 | return PAGE_ACTIVATE; | |
0e093d99 | 480 | if (!may_write_to_queue(mapping->backing_dev_info, sc)) |
1da177e4 LT |
481 | return PAGE_KEEP; |
482 | ||
483 | if (clear_page_dirty_for_io(page)) { | |
484 | int res; | |
485 | struct writeback_control wbc = { | |
486 | .sync_mode = WB_SYNC_NONE, | |
487 | .nr_to_write = SWAP_CLUSTER_MAX, | |
111ebb6e OH |
488 | .range_start = 0, |
489 | .range_end = LLONG_MAX, | |
1da177e4 LT |
490 | .for_reclaim = 1, |
491 | }; | |
492 | ||
493 | SetPageReclaim(page); | |
494 | res = mapping->a_ops->writepage(page, &wbc); | |
495 | if (res < 0) | |
496 | handle_write_error(mapping, page, res); | |
994fc28c | 497 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
1da177e4 LT |
498 | ClearPageReclaim(page); |
499 | return PAGE_ACTIVATE; | |
500 | } | |
c661b078 | 501 | |
1da177e4 LT |
502 | if (!PageWriteback(page)) { |
503 | /* synchronous write or broken a_ops? */ | |
504 | ClearPageReclaim(page); | |
505 | } | |
23b9da55 | 506 | trace_mm_vmscan_writepage(page, trace_reclaim_flags(page)); |
e129b5c2 | 507 | inc_zone_page_state(page, NR_VMSCAN_WRITE); |
1da177e4 LT |
508 | return PAGE_SUCCESS; |
509 | } | |
510 | ||
511 | return PAGE_CLEAN; | |
512 | } | |
513 | ||
a649fd92 | 514 | /* |
e286781d NP |
515 | * Same as remove_mapping, but if the page is removed from the mapping, it |
516 | * gets returned with a refcount of 0. | |
a649fd92 | 517 | */ |
e286781d | 518 | static int __remove_mapping(struct address_space *mapping, struct page *page) |
49d2e9cc | 519 | { |
28e4d965 NP |
520 | BUG_ON(!PageLocked(page)); |
521 | BUG_ON(mapping != page_mapping(page)); | |
49d2e9cc | 522 | |
19fd6231 | 523 | spin_lock_irq(&mapping->tree_lock); |
49d2e9cc | 524 | /* |
0fd0e6b0 NP |
525 | * The non racy check for a busy page. |
526 | * | |
527 | * Must be careful with the order of the tests. When someone has | |
528 | * a ref to the page, it may be possible that they dirty it then | |
529 | * drop the reference. So if PageDirty is tested before page_count | |
530 | * here, then the following race may occur: | |
531 | * | |
532 | * get_user_pages(&page); | |
533 | * [user mapping goes away] | |
534 | * write_to(page); | |
535 | * !PageDirty(page) [good] | |
536 | * SetPageDirty(page); | |
537 | * put_page(page); | |
538 | * !page_count(page) [good, discard it] | |
539 | * | |
540 | * [oops, our write_to data is lost] | |
541 | * | |
542 | * Reversing the order of the tests ensures such a situation cannot | |
543 | * escape unnoticed. The smp_rmb is needed to ensure the page->flags | |
544 | * load is not satisfied before that of page->_count. | |
545 | * | |
546 | * Note that if SetPageDirty is always performed via set_page_dirty, | |
547 | * and thus under tree_lock, then this ordering is not required. | |
49d2e9cc | 548 | */ |
e286781d | 549 | if (!page_freeze_refs(page, 2)) |
49d2e9cc | 550 | goto cannot_free; |
e286781d NP |
551 | /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ |
552 | if (unlikely(PageDirty(page))) { | |
553 | page_unfreeze_refs(page, 2); | |
49d2e9cc | 554 | goto cannot_free; |
e286781d | 555 | } |
49d2e9cc CL |
556 | |
557 | if (PageSwapCache(page)) { | |
558 | swp_entry_t swap = { .val = page_private(page) }; | |
559 | __delete_from_swap_cache(page); | |
19fd6231 | 560 | spin_unlock_irq(&mapping->tree_lock); |
cb4b86ba | 561 | swapcache_free(swap, page); |
e286781d | 562 | } else { |
6072d13c LT |
563 | void (*freepage)(struct page *); |
564 | ||
565 | freepage = mapping->a_ops->freepage; | |
566 | ||
e64a782f | 567 | __delete_from_page_cache(page); |
19fd6231 | 568 | spin_unlock_irq(&mapping->tree_lock); |
e767e056 | 569 | mem_cgroup_uncharge_cache_page(page); |
6072d13c LT |
570 | |
571 | if (freepage != NULL) | |
572 | freepage(page); | |
49d2e9cc CL |
573 | } |
574 | ||
49d2e9cc CL |
575 | return 1; |
576 | ||
577 | cannot_free: | |
19fd6231 | 578 | spin_unlock_irq(&mapping->tree_lock); |
49d2e9cc CL |
579 | return 0; |
580 | } | |
581 | ||
e286781d NP |
582 | /* |
583 | * Attempt to detach a locked page from its ->mapping. If it is dirty or if | |
584 | * someone else has a ref on the page, abort and return 0. If it was | |
585 | * successfully detached, return 1. Assumes the caller has a single ref on | |
586 | * this page. | |
587 | */ | |
588 | int remove_mapping(struct address_space *mapping, struct page *page) | |
589 | { | |
590 | if (__remove_mapping(mapping, page)) { | |
591 | /* | |
592 | * Unfreezing the refcount with 1 rather than 2 effectively | |
593 | * drops the pagecache ref for us without requiring another | |
594 | * atomic operation. | |
595 | */ | |
596 | page_unfreeze_refs(page, 1); | |
597 | return 1; | |
598 | } | |
599 | return 0; | |
600 | } | |
601 | ||
894bc310 LS |
602 | /** |
603 | * putback_lru_page - put previously isolated page onto appropriate LRU list | |
604 | * @page: page to be put back to appropriate lru list | |
605 | * | |
606 | * Add previously isolated @page to appropriate LRU list. | |
607 | * Page may still be unevictable for other reasons. | |
608 | * | |
609 | * lru_lock must not be held, interrupts must be enabled. | |
610 | */ | |
894bc310 LS |
611 | void putback_lru_page(struct page *page) |
612 | { | |
0ec3b74c | 613 | bool is_unevictable; |
bbfd28ee | 614 | int was_unevictable = PageUnevictable(page); |
894bc310 LS |
615 | |
616 | VM_BUG_ON(PageLRU(page)); | |
617 | ||
618 | redo: | |
619 | ClearPageUnevictable(page); | |
620 | ||
39b5f29a | 621 | if (page_evictable(page)) { |
894bc310 LS |
622 | /* |
623 | * For evictable pages, we can use the cache. | |
624 | * In event of a race, worst case is we end up with an | |
625 | * unevictable page on [in]active list. | |
626 | * We know how to handle that. | |
627 | */ | |
0ec3b74c | 628 | is_unevictable = false; |
c53954a0 | 629 | lru_cache_add(page); |
894bc310 LS |
630 | } else { |
631 | /* | |
632 | * Put unevictable pages directly on zone's unevictable | |
633 | * list. | |
634 | */ | |
0ec3b74c | 635 | is_unevictable = true; |
894bc310 | 636 | add_page_to_unevictable_list(page); |
6a7b9548 | 637 | /* |
21ee9f39 MK |
638 | * When racing with an mlock or AS_UNEVICTABLE clearing |
639 | * (page is unlocked) make sure that if the other thread | |
640 | * does not observe our setting of PG_lru and fails | |
24513264 | 641 | * isolation/check_move_unevictable_pages, |
21ee9f39 | 642 | * we see PG_mlocked/AS_UNEVICTABLE cleared below and move |
6a7b9548 JW |
643 | * the page back to the evictable list. |
644 | * | |
21ee9f39 | 645 | * The other side is TestClearPageMlocked() or shmem_lock(). |
6a7b9548 JW |
646 | */ |
647 | smp_mb(); | |
894bc310 | 648 | } |
894bc310 LS |
649 | |
650 | /* | |
651 | * page's status can change while we move it among lru. If an evictable | |
652 | * page is on unevictable list, it never be freed. To avoid that, | |
653 | * check after we added it to the list, again. | |
654 | */ | |
0ec3b74c | 655 | if (is_unevictable && page_evictable(page)) { |
894bc310 LS |
656 | if (!isolate_lru_page(page)) { |
657 | put_page(page); | |
658 | goto redo; | |
659 | } | |
660 | /* This means someone else dropped this page from LRU | |
661 | * So, it will be freed or putback to LRU again. There is | |
662 | * nothing to do here. | |
663 | */ | |
664 | } | |
665 | ||
0ec3b74c | 666 | if (was_unevictable && !is_unevictable) |
bbfd28ee | 667 | count_vm_event(UNEVICTABLE_PGRESCUED); |
0ec3b74c | 668 | else if (!was_unevictable && is_unevictable) |
bbfd28ee LS |
669 | count_vm_event(UNEVICTABLE_PGCULLED); |
670 | ||
894bc310 LS |
671 | put_page(page); /* drop ref from isolate */ |
672 | } | |
673 | ||
dfc8d636 JW |
674 | enum page_references { |
675 | PAGEREF_RECLAIM, | |
676 | PAGEREF_RECLAIM_CLEAN, | |
64574746 | 677 | PAGEREF_KEEP, |
dfc8d636 JW |
678 | PAGEREF_ACTIVATE, |
679 | }; | |
680 | ||
681 | static enum page_references page_check_references(struct page *page, | |
682 | struct scan_control *sc) | |
683 | { | |
64574746 | 684 | int referenced_ptes, referenced_page; |
dfc8d636 | 685 | unsigned long vm_flags; |
dfc8d636 | 686 | |
c3ac9a8a JW |
687 | referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup, |
688 | &vm_flags); | |
64574746 | 689 | referenced_page = TestClearPageReferenced(page); |
dfc8d636 | 690 | |
dfc8d636 JW |
691 | /* |
692 | * Mlock lost the isolation race with us. Let try_to_unmap() | |
693 | * move the page to the unevictable list. | |
694 | */ | |
695 | if (vm_flags & VM_LOCKED) | |
696 | return PAGEREF_RECLAIM; | |
697 | ||
64574746 | 698 | if (referenced_ptes) { |
e4898273 | 699 | if (PageSwapBacked(page)) |
64574746 JW |
700 | return PAGEREF_ACTIVATE; |
701 | /* | |
702 | * All mapped pages start out with page table | |
703 | * references from the instantiating fault, so we need | |
704 | * to look twice if a mapped file page is used more | |
705 | * than once. | |
706 | * | |
707 | * Mark it and spare it for another trip around the | |
708 | * inactive list. Another page table reference will | |
709 | * lead to its activation. | |
710 | * | |
711 | * Note: the mark is set for activated pages as well | |
712 | * so that recently deactivated but used pages are | |
713 | * quickly recovered. | |
714 | */ | |
715 | SetPageReferenced(page); | |
716 | ||
34dbc67a | 717 | if (referenced_page || referenced_ptes > 1) |
64574746 JW |
718 | return PAGEREF_ACTIVATE; |
719 | ||
c909e993 KK |
720 | /* |
721 | * Activate file-backed executable pages after first usage. | |
722 | */ | |
723 | if (vm_flags & VM_EXEC) | |
724 | return PAGEREF_ACTIVATE; | |
725 | ||
64574746 JW |
726 | return PAGEREF_KEEP; |
727 | } | |
dfc8d636 JW |
728 | |
729 | /* Reclaim if clean, defer dirty pages to writeback */ | |
2e30244a | 730 | if (referenced_page && !PageSwapBacked(page)) |
64574746 JW |
731 | return PAGEREF_RECLAIM_CLEAN; |
732 | ||
733 | return PAGEREF_RECLAIM; | |
dfc8d636 JW |
734 | } |
735 | ||
e2be15f6 MG |
736 | /* Check if a page is dirty or under writeback */ |
737 | static void page_check_dirty_writeback(struct page *page, | |
738 | bool *dirty, bool *writeback) | |
739 | { | |
b4597226 MG |
740 | struct address_space *mapping; |
741 | ||
e2be15f6 MG |
742 | /* |
743 | * Anonymous pages are not handled by flushers and must be written | |
744 | * from reclaim context. Do not stall reclaim based on them | |
745 | */ | |
746 | if (!page_is_file_cache(page)) { | |
747 | *dirty = false; | |
748 | *writeback = false; | |
749 | return; | |
750 | } | |
751 | ||
752 | /* By default assume that the page flags are accurate */ | |
753 | *dirty = PageDirty(page); | |
754 | *writeback = PageWriteback(page); | |
b4597226 MG |
755 | |
756 | /* Verify dirty/writeback state if the filesystem supports it */ | |
757 | if (!page_has_private(page)) | |
758 | return; | |
759 | ||
760 | mapping = page_mapping(page); | |
761 | if (mapping && mapping->a_ops->is_dirty_writeback) | |
762 | mapping->a_ops->is_dirty_writeback(page, dirty, writeback); | |
e2be15f6 MG |
763 | } |
764 | ||
1da177e4 | 765 | /* |
1742f19f | 766 | * shrink_page_list() returns the number of reclaimed pages |
1da177e4 | 767 | */ |
1742f19f | 768 | static unsigned long shrink_page_list(struct list_head *page_list, |
6a18adb3 | 769 | struct zone *zone, |
f84f6e2b | 770 | struct scan_control *sc, |
02c6de8d | 771 | enum ttu_flags ttu_flags, |
8e950282 | 772 | unsigned long *ret_nr_dirty, |
d43006d5 | 773 | unsigned long *ret_nr_unqueued_dirty, |
8e950282 | 774 | unsigned long *ret_nr_congested, |
02c6de8d | 775 | unsigned long *ret_nr_writeback, |
b1a6f21e | 776 | unsigned long *ret_nr_immediate, |
02c6de8d | 777 | bool force_reclaim) |
1da177e4 LT |
778 | { |
779 | LIST_HEAD(ret_pages); | |
abe4c3b5 | 780 | LIST_HEAD(free_pages); |
1da177e4 | 781 | int pgactivate = 0; |
d43006d5 | 782 | unsigned long nr_unqueued_dirty = 0; |
0e093d99 MG |
783 | unsigned long nr_dirty = 0; |
784 | unsigned long nr_congested = 0; | |
05ff5137 | 785 | unsigned long nr_reclaimed = 0; |
92df3a72 | 786 | unsigned long nr_writeback = 0; |
b1a6f21e | 787 | unsigned long nr_immediate = 0; |
1da177e4 LT |
788 | |
789 | cond_resched(); | |
790 | ||
69980e31 | 791 | mem_cgroup_uncharge_start(); |
1da177e4 LT |
792 | while (!list_empty(page_list)) { |
793 | struct address_space *mapping; | |
794 | struct page *page; | |
795 | int may_enter_fs; | |
02c6de8d | 796 | enum page_references references = PAGEREF_RECLAIM_CLEAN; |
e2be15f6 | 797 | bool dirty, writeback; |
1da177e4 LT |
798 | |
799 | cond_resched(); | |
800 | ||
801 | page = lru_to_page(page_list); | |
802 | list_del(&page->lru); | |
803 | ||
529ae9aa | 804 | if (!trylock_page(page)) |
1da177e4 LT |
805 | goto keep; |
806 | ||
725d704e | 807 | VM_BUG_ON(PageActive(page)); |
6a18adb3 | 808 | VM_BUG_ON(page_zone(page) != zone); |
1da177e4 LT |
809 | |
810 | sc->nr_scanned++; | |
80e43426 | 811 | |
39b5f29a | 812 | if (unlikely(!page_evictable(page))) |
b291f000 | 813 | goto cull_mlocked; |
894bc310 | 814 | |
a6dc60f8 | 815 | if (!sc->may_unmap && page_mapped(page)) |
80e43426 CL |
816 | goto keep_locked; |
817 | ||
1da177e4 LT |
818 | /* Double the slab pressure for mapped and swapcache pages */ |
819 | if (page_mapped(page) || PageSwapCache(page)) | |
820 | sc->nr_scanned++; | |
821 | ||
c661b078 AW |
822 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || |
823 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); | |
824 | ||
e2be15f6 MG |
825 | /* |
826 | * The number of dirty pages determines if a zone is marked | |
827 | * reclaim_congested which affects wait_iff_congested. kswapd | |
828 | * will stall and start writing pages if the tail of the LRU | |
829 | * is all dirty unqueued pages. | |
830 | */ | |
831 | page_check_dirty_writeback(page, &dirty, &writeback); | |
832 | if (dirty || writeback) | |
833 | nr_dirty++; | |
834 | ||
835 | if (dirty && !writeback) | |
836 | nr_unqueued_dirty++; | |
837 | ||
d04e8acd MG |
838 | /* |
839 | * Treat this page as congested if the underlying BDI is or if | |
840 | * pages are cycling through the LRU so quickly that the | |
841 | * pages marked for immediate reclaim are making it to the | |
842 | * end of the LRU a second time. | |
843 | */ | |
e2be15f6 | 844 | mapping = page_mapping(page); |
d04e8acd MG |
845 | if ((mapping && bdi_write_congested(mapping->backing_dev_info)) || |
846 | (writeback && PageReclaim(page))) | |
e2be15f6 MG |
847 | nr_congested++; |
848 | ||
283aba9f MG |
849 | /* |
850 | * If a page at the tail of the LRU is under writeback, there | |
851 | * are three cases to consider. | |
852 | * | |
853 | * 1) If reclaim is encountering an excessive number of pages | |
854 | * under writeback and this page is both under writeback and | |
855 | * PageReclaim then it indicates that pages are being queued | |
856 | * for IO but are being recycled through the LRU before the | |
857 | * IO can complete. Waiting on the page itself risks an | |
858 | * indefinite stall if it is impossible to writeback the | |
859 | * page due to IO error or disconnected storage so instead | |
b1a6f21e MG |
860 | * note that the LRU is being scanned too quickly and the |
861 | * caller can stall after page list has been processed. | |
283aba9f MG |
862 | * |
863 | * 2) Global reclaim encounters a page, memcg encounters a | |
864 | * page that is not marked for immediate reclaim or | |
865 | * the caller does not have __GFP_IO. In this case mark | |
866 | * the page for immediate reclaim and continue scanning. | |
867 | * | |
868 | * __GFP_IO is checked because a loop driver thread might | |
869 | * enter reclaim, and deadlock if it waits on a page for | |
870 | * which it is needed to do the write (loop masks off | |
871 | * __GFP_IO|__GFP_FS for this reason); but more thought | |
872 | * would probably show more reasons. | |
873 | * | |
874 | * Don't require __GFP_FS, since we're not going into the | |
875 | * FS, just waiting on its writeback completion. Worryingly, | |
876 | * ext4 gfs2 and xfs allocate pages with | |
877 | * grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing | |
878 | * may_enter_fs here is liable to OOM on them. | |
879 | * | |
880 | * 3) memcg encounters a page that is not already marked | |
881 | * PageReclaim. memcg does not have any dirty pages | |
882 | * throttling so we could easily OOM just because too many | |
883 | * pages are in writeback and there is nothing else to | |
884 | * reclaim. Wait for the writeback to complete. | |
885 | */ | |
c661b078 | 886 | if (PageWriteback(page)) { |
283aba9f MG |
887 | /* Case 1 above */ |
888 | if (current_is_kswapd() && | |
889 | PageReclaim(page) && | |
890 | zone_is_reclaim_writeback(zone)) { | |
b1a6f21e MG |
891 | nr_immediate++; |
892 | goto keep_locked; | |
283aba9f MG |
893 | |
894 | /* Case 2 above */ | |
895 | } else if (global_reclaim(sc) || | |
c3b94f44 HD |
896 | !PageReclaim(page) || !(sc->gfp_mask & __GFP_IO)) { |
897 | /* | |
898 | * This is slightly racy - end_page_writeback() | |
899 | * might have just cleared PageReclaim, then | |
900 | * setting PageReclaim here end up interpreted | |
901 | * as PageReadahead - but that does not matter | |
902 | * enough to care. What we do want is for this | |
903 | * page to have PageReclaim set next time memcg | |
904 | * reclaim reaches the tests above, so it will | |
905 | * then wait_on_page_writeback() to avoid OOM; | |
906 | * and it's also appropriate in global reclaim. | |
907 | */ | |
908 | SetPageReclaim(page); | |
e62e384e | 909 | nr_writeback++; |
283aba9f | 910 | |
c3b94f44 | 911 | goto keep_locked; |
283aba9f MG |
912 | |
913 | /* Case 3 above */ | |
914 | } else { | |
915 | wait_on_page_writeback(page); | |
e62e384e | 916 | } |
c661b078 | 917 | } |
1da177e4 | 918 | |
02c6de8d MK |
919 | if (!force_reclaim) |
920 | references = page_check_references(page, sc); | |
921 | ||
dfc8d636 JW |
922 | switch (references) { |
923 | case PAGEREF_ACTIVATE: | |
1da177e4 | 924 | goto activate_locked; |
64574746 JW |
925 | case PAGEREF_KEEP: |
926 | goto keep_locked; | |
dfc8d636 JW |
927 | case PAGEREF_RECLAIM: |
928 | case PAGEREF_RECLAIM_CLEAN: | |
929 | ; /* try to reclaim the page below */ | |
930 | } | |
1da177e4 | 931 | |
1da177e4 LT |
932 | /* |
933 | * Anonymous process memory has backing store? | |
934 | * Try to allocate it some swap space here. | |
935 | */ | |
b291f000 | 936 | if (PageAnon(page) && !PageSwapCache(page)) { |
63eb6b93 HD |
937 | if (!(sc->gfp_mask & __GFP_IO)) |
938 | goto keep_locked; | |
5bc7b8ac | 939 | if (!add_to_swap(page, page_list)) |
1da177e4 | 940 | goto activate_locked; |
63eb6b93 | 941 | may_enter_fs = 1; |
1da177e4 | 942 | |
e2be15f6 MG |
943 | /* Adding to swap updated mapping */ |
944 | mapping = page_mapping(page); | |
945 | } | |
1da177e4 LT |
946 | |
947 | /* | |
948 | * The page is mapped into the page tables of one or more | |
949 | * processes. Try to unmap it here. | |
950 | */ | |
951 | if (page_mapped(page) && mapping) { | |
02c6de8d | 952 | switch (try_to_unmap(page, ttu_flags)) { |
1da177e4 LT |
953 | case SWAP_FAIL: |
954 | goto activate_locked; | |
955 | case SWAP_AGAIN: | |
956 | goto keep_locked; | |
b291f000 NP |
957 | case SWAP_MLOCK: |
958 | goto cull_mlocked; | |
1da177e4 LT |
959 | case SWAP_SUCCESS: |
960 | ; /* try to free the page below */ | |
961 | } | |
962 | } | |
963 | ||
964 | if (PageDirty(page)) { | |
ee72886d MG |
965 | /* |
966 | * Only kswapd can writeback filesystem pages to | |
d43006d5 MG |
967 | * avoid risk of stack overflow but only writeback |
968 | * if many dirty pages have been encountered. | |
ee72886d | 969 | */ |
f84f6e2b | 970 | if (page_is_file_cache(page) && |
9e3b2f8c | 971 | (!current_is_kswapd() || |
d43006d5 | 972 | !zone_is_reclaim_dirty(zone))) { |
49ea7eb6 MG |
973 | /* |
974 | * Immediately reclaim when written back. | |
975 | * Similar in principal to deactivate_page() | |
976 | * except we already have the page isolated | |
977 | * and know it's dirty | |
978 | */ | |
979 | inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE); | |
980 | SetPageReclaim(page); | |
981 | ||
ee72886d MG |
982 | goto keep_locked; |
983 | } | |
984 | ||
dfc8d636 | 985 | if (references == PAGEREF_RECLAIM_CLEAN) |
1da177e4 | 986 | goto keep_locked; |
4dd4b920 | 987 | if (!may_enter_fs) |
1da177e4 | 988 | goto keep_locked; |
52a8363e | 989 | if (!sc->may_writepage) |
1da177e4 LT |
990 | goto keep_locked; |
991 | ||
992 | /* Page is dirty, try to write it out here */ | |
7d3579e8 | 993 | switch (pageout(page, mapping, sc)) { |
1da177e4 LT |
994 | case PAGE_KEEP: |
995 | goto keep_locked; | |
996 | case PAGE_ACTIVATE: | |
997 | goto activate_locked; | |
998 | case PAGE_SUCCESS: | |
7d3579e8 | 999 | if (PageWriteback(page)) |
41ac1999 | 1000 | goto keep; |
7d3579e8 | 1001 | if (PageDirty(page)) |
1da177e4 | 1002 | goto keep; |
7d3579e8 | 1003 | |
1da177e4 LT |
1004 | /* |
1005 | * A synchronous write - probably a ramdisk. Go | |
1006 | * ahead and try to reclaim the page. | |
1007 | */ | |
529ae9aa | 1008 | if (!trylock_page(page)) |
1da177e4 LT |
1009 | goto keep; |
1010 | if (PageDirty(page) || PageWriteback(page)) | |
1011 | goto keep_locked; | |
1012 | mapping = page_mapping(page); | |
1013 | case PAGE_CLEAN: | |
1014 | ; /* try to free the page below */ | |
1015 | } | |
1016 | } | |
1017 | ||
1018 | /* | |
1019 | * If the page has buffers, try to free the buffer mappings | |
1020 | * associated with this page. If we succeed we try to free | |
1021 | * the page as well. | |
1022 | * | |
1023 | * We do this even if the page is PageDirty(). | |
1024 | * try_to_release_page() does not perform I/O, but it is | |
1025 | * possible for a page to have PageDirty set, but it is actually | |
1026 | * clean (all its buffers are clean). This happens if the | |
1027 | * buffers were written out directly, with submit_bh(). ext3 | |
894bc310 | 1028 | * will do this, as well as the blockdev mapping. |
1da177e4 LT |
1029 | * try_to_release_page() will discover that cleanness and will |
1030 | * drop the buffers and mark the page clean - it can be freed. | |
1031 | * | |
1032 | * Rarely, pages can have buffers and no ->mapping. These are | |
1033 | * the pages which were not successfully invalidated in | |
1034 | * truncate_complete_page(). We try to drop those buffers here | |
1035 | * and if that worked, and the page is no longer mapped into | |
1036 | * process address space (page_count == 1) it can be freed. | |
1037 | * Otherwise, leave the page on the LRU so it is swappable. | |
1038 | */ | |
266cf658 | 1039 | if (page_has_private(page)) { |
1da177e4 LT |
1040 | if (!try_to_release_page(page, sc->gfp_mask)) |
1041 | goto activate_locked; | |
e286781d NP |
1042 | if (!mapping && page_count(page) == 1) { |
1043 | unlock_page(page); | |
1044 | if (put_page_testzero(page)) | |
1045 | goto free_it; | |
1046 | else { | |
1047 | /* | |
1048 | * rare race with speculative reference. | |
1049 | * the speculative reference will free | |
1050 | * this page shortly, so we may | |
1051 | * increment nr_reclaimed here (and | |
1052 | * leave it off the LRU). | |
1053 | */ | |
1054 | nr_reclaimed++; | |
1055 | continue; | |
1056 | } | |
1057 | } | |
1da177e4 LT |
1058 | } |
1059 | ||
e286781d | 1060 | if (!mapping || !__remove_mapping(mapping, page)) |
49d2e9cc | 1061 | goto keep_locked; |
1da177e4 | 1062 | |
a978d6f5 NP |
1063 | /* |
1064 | * At this point, we have no other references and there is | |
1065 | * no way to pick any more up (removed from LRU, removed | |
1066 | * from pagecache). Can use non-atomic bitops now (and | |
1067 | * we obviously don't have to worry about waking up a process | |
1068 | * waiting on the page lock, because there are no references. | |
1069 | */ | |
1070 | __clear_page_locked(page); | |
e286781d | 1071 | free_it: |
05ff5137 | 1072 | nr_reclaimed++; |
abe4c3b5 MG |
1073 | |
1074 | /* | |
1075 | * Is there need to periodically free_page_list? It would | |
1076 | * appear not as the counts should be low | |
1077 | */ | |
1078 | list_add(&page->lru, &free_pages); | |
1da177e4 LT |
1079 | continue; |
1080 | ||
b291f000 | 1081 | cull_mlocked: |
63d6c5ad HD |
1082 | if (PageSwapCache(page)) |
1083 | try_to_free_swap(page); | |
b291f000 NP |
1084 | unlock_page(page); |
1085 | putback_lru_page(page); | |
1086 | continue; | |
1087 | ||
1da177e4 | 1088 | activate_locked: |
68a22394 RR |
1089 | /* Not a candidate for swapping, so reclaim swap space. */ |
1090 | if (PageSwapCache(page) && vm_swap_full()) | |
a2c43eed | 1091 | try_to_free_swap(page); |
894bc310 | 1092 | VM_BUG_ON(PageActive(page)); |
1da177e4 LT |
1093 | SetPageActive(page); |
1094 | pgactivate++; | |
1095 | keep_locked: | |
1096 | unlock_page(page); | |
1097 | keep: | |
1098 | list_add(&page->lru, &ret_pages); | |
b291f000 | 1099 | VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); |
1da177e4 | 1100 | } |
abe4c3b5 | 1101 | |
cc59850e | 1102 | free_hot_cold_page_list(&free_pages, 1); |
abe4c3b5 | 1103 | |
1da177e4 | 1104 | list_splice(&ret_pages, page_list); |
f8891e5e | 1105 | count_vm_events(PGACTIVATE, pgactivate); |
69980e31 | 1106 | mem_cgroup_uncharge_end(); |
8e950282 MG |
1107 | *ret_nr_dirty += nr_dirty; |
1108 | *ret_nr_congested += nr_congested; | |
d43006d5 | 1109 | *ret_nr_unqueued_dirty += nr_unqueued_dirty; |
92df3a72 | 1110 | *ret_nr_writeback += nr_writeback; |
b1a6f21e | 1111 | *ret_nr_immediate += nr_immediate; |
05ff5137 | 1112 | return nr_reclaimed; |
1da177e4 LT |
1113 | } |
1114 | ||
02c6de8d MK |
1115 | unsigned long reclaim_clean_pages_from_list(struct zone *zone, |
1116 | struct list_head *page_list) | |
1117 | { | |
1118 | struct scan_control sc = { | |
1119 | .gfp_mask = GFP_KERNEL, | |
1120 | .priority = DEF_PRIORITY, | |
1121 | .may_unmap = 1, | |
1122 | }; | |
8e950282 | 1123 | unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5; |
02c6de8d MK |
1124 | struct page *page, *next; |
1125 | LIST_HEAD(clean_pages); | |
1126 | ||
1127 | list_for_each_entry_safe(page, next, page_list, lru) { | |
1128 | if (page_is_file_cache(page) && !PageDirty(page)) { | |
1129 | ClearPageActive(page); | |
1130 | list_move(&page->lru, &clean_pages); | |
1131 | } | |
1132 | } | |
1133 | ||
1134 | ret = shrink_page_list(&clean_pages, zone, &sc, | |
8e950282 MG |
1135 | TTU_UNMAP|TTU_IGNORE_ACCESS, |
1136 | &dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true); | |
02c6de8d MK |
1137 | list_splice(&clean_pages, page_list); |
1138 | __mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret); | |
1139 | return ret; | |
1140 | } | |
1141 | ||
5ad333eb AW |
1142 | /* |
1143 | * Attempt to remove the specified page from its LRU. Only take this page | |
1144 | * if it is of the appropriate PageActive status. Pages which are being | |
1145 | * freed elsewhere are also ignored. | |
1146 | * | |
1147 | * page: page to consider | |
1148 | * mode: one of the LRU isolation modes defined above | |
1149 | * | |
1150 | * returns 0 on success, -ve errno on failure. | |
1151 | */ | |
f3fd4a61 | 1152 | int __isolate_lru_page(struct page *page, isolate_mode_t mode) |
5ad333eb AW |
1153 | { |
1154 | int ret = -EINVAL; | |
1155 | ||
1156 | /* Only take pages on the LRU. */ | |
1157 | if (!PageLRU(page)) | |
1158 | return ret; | |
1159 | ||
e46a2879 MK |
1160 | /* Compaction should not handle unevictable pages but CMA can do so */ |
1161 | if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE)) | |
894bc310 LS |
1162 | return ret; |
1163 | ||
5ad333eb | 1164 | ret = -EBUSY; |
08e552c6 | 1165 | |
c8244935 MG |
1166 | /* |
1167 | * To minimise LRU disruption, the caller can indicate that it only | |
1168 | * wants to isolate pages it will be able to operate on without | |
1169 | * blocking - clean pages for the most part. | |
1170 | * | |
1171 | * ISOLATE_CLEAN means that only clean pages should be isolated. This | |
1172 | * is used by reclaim when it is cannot write to backing storage | |
1173 | * | |
1174 | * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages | |
1175 | * that it is possible to migrate without blocking | |
1176 | */ | |
1177 | if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) { | |
1178 | /* All the caller can do on PageWriteback is block */ | |
1179 | if (PageWriteback(page)) | |
1180 | return ret; | |
1181 | ||
1182 | if (PageDirty(page)) { | |
1183 | struct address_space *mapping; | |
1184 | ||
1185 | /* ISOLATE_CLEAN means only clean pages */ | |
1186 | if (mode & ISOLATE_CLEAN) | |
1187 | return ret; | |
1188 | ||
1189 | /* | |
1190 | * Only pages without mappings or that have a | |
1191 | * ->migratepage callback are possible to migrate | |
1192 | * without blocking | |
1193 | */ | |
1194 | mapping = page_mapping(page); | |
1195 | if (mapping && !mapping->a_ops->migratepage) | |
1196 | return ret; | |
1197 | } | |
1198 | } | |
39deaf85 | 1199 | |
f80c0673 MK |
1200 | if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) |
1201 | return ret; | |
1202 | ||
5ad333eb AW |
1203 | if (likely(get_page_unless_zero(page))) { |
1204 | /* | |
1205 | * Be careful not to clear PageLRU until after we're | |
1206 | * sure the page is not being freed elsewhere -- the | |
1207 | * page release code relies on it. | |
1208 | */ | |
1209 | ClearPageLRU(page); | |
1210 | ret = 0; | |
1211 | } | |
1212 | ||
1213 | return ret; | |
1214 | } | |
1215 | ||
1da177e4 LT |
1216 | /* |
1217 | * zone->lru_lock is heavily contended. Some of the functions that | |
1218 | * shrink the lists perform better by taking out a batch of pages | |
1219 | * and working on them outside the LRU lock. | |
1220 | * | |
1221 | * For pagecache intensive workloads, this function is the hottest | |
1222 | * spot in the kernel (apart from copy_*_user functions). | |
1223 | * | |
1224 | * Appropriate locks must be held before calling this function. | |
1225 | * | |
1226 | * @nr_to_scan: The number of pages to look through on the list. | |
5dc35979 | 1227 | * @lruvec: The LRU vector to pull pages from. |
1da177e4 | 1228 | * @dst: The temp list to put pages on to. |
f626012d | 1229 | * @nr_scanned: The number of pages that were scanned. |
fe2c2a10 | 1230 | * @sc: The scan_control struct for this reclaim session |
5ad333eb | 1231 | * @mode: One of the LRU isolation modes |
3cb99451 | 1232 | * @lru: LRU list id for isolating |
1da177e4 LT |
1233 | * |
1234 | * returns how many pages were moved onto *@dst. | |
1235 | */ | |
69e05944 | 1236 | static unsigned long isolate_lru_pages(unsigned long nr_to_scan, |
5dc35979 | 1237 | struct lruvec *lruvec, struct list_head *dst, |
fe2c2a10 | 1238 | unsigned long *nr_scanned, struct scan_control *sc, |
3cb99451 | 1239 | isolate_mode_t mode, enum lru_list lru) |
1da177e4 | 1240 | { |
75b00af7 | 1241 | struct list_head *src = &lruvec->lists[lru]; |
69e05944 | 1242 | unsigned long nr_taken = 0; |
c9b02d97 | 1243 | unsigned long scan; |
1da177e4 | 1244 | |
c9b02d97 | 1245 | for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { |
5ad333eb | 1246 | struct page *page; |
fa9add64 | 1247 | int nr_pages; |
5ad333eb | 1248 | |
1da177e4 LT |
1249 | page = lru_to_page(src); |
1250 | prefetchw_prev_lru_page(page, src, flags); | |
1251 | ||
725d704e | 1252 | VM_BUG_ON(!PageLRU(page)); |
8d438f96 | 1253 | |
f3fd4a61 | 1254 | switch (__isolate_lru_page(page, mode)) { |
5ad333eb | 1255 | case 0: |
fa9add64 HD |
1256 | nr_pages = hpage_nr_pages(page); |
1257 | mem_cgroup_update_lru_size(lruvec, lru, -nr_pages); | |
5ad333eb | 1258 | list_move(&page->lru, dst); |
fa9add64 | 1259 | nr_taken += nr_pages; |
5ad333eb AW |
1260 | break; |
1261 | ||
1262 | case -EBUSY: | |
1263 | /* else it is being freed elsewhere */ | |
1264 | list_move(&page->lru, src); | |
1265 | continue; | |
46453a6e | 1266 | |
5ad333eb AW |
1267 | default: |
1268 | BUG(); | |
1269 | } | |
1da177e4 LT |
1270 | } |
1271 | ||
f626012d | 1272 | *nr_scanned = scan; |
75b00af7 HD |
1273 | trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan, |
1274 | nr_taken, mode, is_file_lru(lru)); | |
1da177e4 LT |
1275 | return nr_taken; |
1276 | } | |
1277 | ||
62695a84 NP |
1278 | /** |
1279 | * isolate_lru_page - tries to isolate a page from its LRU list | |
1280 | * @page: page to isolate from its LRU list | |
1281 | * | |
1282 | * Isolates a @page from an LRU list, clears PageLRU and adjusts the | |
1283 | * vmstat statistic corresponding to whatever LRU list the page was on. | |
1284 | * | |
1285 | * Returns 0 if the page was removed from an LRU list. | |
1286 | * Returns -EBUSY if the page was not on an LRU list. | |
1287 | * | |
1288 | * The returned page will have PageLRU() cleared. If it was found on | |
894bc310 LS |
1289 | * the active list, it will have PageActive set. If it was found on |
1290 | * the unevictable list, it will have the PageUnevictable bit set. That flag | |
1291 | * may need to be cleared by the caller before letting the page go. | |
62695a84 NP |
1292 | * |
1293 | * The vmstat statistic corresponding to the list on which the page was | |
1294 | * found will be decremented. | |
1295 | * | |
1296 | * Restrictions: | |
1297 | * (1) Must be called with an elevated refcount on the page. This is a | |
1298 | * fundamentnal difference from isolate_lru_pages (which is called | |
1299 | * without a stable reference). | |
1300 | * (2) the lru_lock must not be held. | |
1301 | * (3) interrupts must be enabled. | |
1302 | */ | |
1303 | int isolate_lru_page(struct page *page) | |
1304 | { | |
1305 | int ret = -EBUSY; | |
1306 | ||
0c917313 KK |
1307 | VM_BUG_ON(!page_count(page)); |
1308 | ||
62695a84 NP |
1309 | if (PageLRU(page)) { |
1310 | struct zone *zone = page_zone(page); | |
fa9add64 | 1311 | struct lruvec *lruvec; |
62695a84 NP |
1312 | |
1313 | spin_lock_irq(&zone->lru_lock); | |
fa9add64 | 1314 | lruvec = mem_cgroup_page_lruvec(page, zone); |
0c917313 | 1315 | if (PageLRU(page)) { |
894bc310 | 1316 | int lru = page_lru(page); |
0c917313 | 1317 | get_page(page); |
62695a84 | 1318 | ClearPageLRU(page); |
fa9add64 HD |
1319 | del_page_from_lru_list(page, lruvec, lru); |
1320 | ret = 0; | |
62695a84 NP |
1321 | } |
1322 | spin_unlock_irq(&zone->lru_lock); | |
1323 | } | |
1324 | return ret; | |
1325 | } | |
1326 | ||
35cd7815 | 1327 | /* |
d37dd5dc FW |
1328 | * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and |
1329 | * then get resheduled. When there are massive number of tasks doing page | |
1330 | * allocation, such sleeping direct reclaimers may keep piling up on each CPU, | |
1331 | * the LRU list will go small and be scanned faster than necessary, leading to | |
1332 | * unnecessary swapping, thrashing and OOM. | |
35cd7815 RR |
1333 | */ |
1334 | static int too_many_isolated(struct zone *zone, int file, | |
1335 | struct scan_control *sc) | |
1336 | { | |
1337 | unsigned long inactive, isolated; | |
1338 | ||
1339 | if (current_is_kswapd()) | |
1340 | return 0; | |
1341 | ||
89b5fae5 | 1342 | if (!global_reclaim(sc)) |
35cd7815 RR |
1343 | return 0; |
1344 | ||
1345 | if (file) { | |
1346 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); | |
1347 | isolated = zone_page_state(zone, NR_ISOLATED_FILE); | |
1348 | } else { | |
1349 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); | |
1350 | isolated = zone_page_state(zone, NR_ISOLATED_ANON); | |
1351 | } | |
1352 | ||
3cf23841 FW |
1353 | /* |
1354 | * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they | |
1355 | * won't get blocked by normal direct-reclaimers, forming a circular | |
1356 | * deadlock. | |
1357 | */ | |
1358 | if ((sc->gfp_mask & GFP_IOFS) == GFP_IOFS) | |
1359 | inactive >>= 3; | |
1360 | ||
35cd7815 RR |
1361 | return isolated > inactive; |
1362 | } | |
1363 | ||
66635629 | 1364 | static noinline_for_stack void |
75b00af7 | 1365 | putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list) |
66635629 | 1366 | { |
27ac81d8 KK |
1367 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
1368 | struct zone *zone = lruvec_zone(lruvec); | |
3f79768f | 1369 | LIST_HEAD(pages_to_free); |
66635629 | 1370 | |
66635629 MG |
1371 | /* |
1372 | * Put back any unfreeable pages. | |
1373 | */ | |
66635629 | 1374 | while (!list_empty(page_list)) { |
3f79768f | 1375 | struct page *page = lru_to_page(page_list); |
66635629 | 1376 | int lru; |
3f79768f | 1377 | |
66635629 MG |
1378 | VM_BUG_ON(PageLRU(page)); |
1379 | list_del(&page->lru); | |
39b5f29a | 1380 | if (unlikely(!page_evictable(page))) { |
66635629 MG |
1381 | spin_unlock_irq(&zone->lru_lock); |
1382 | putback_lru_page(page); | |
1383 | spin_lock_irq(&zone->lru_lock); | |
1384 | continue; | |
1385 | } | |
fa9add64 HD |
1386 | |
1387 | lruvec = mem_cgroup_page_lruvec(page, zone); | |
1388 | ||
7a608572 | 1389 | SetPageLRU(page); |
66635629 | 1390 | lru = page_lru(page); |
fa9add64 HD |
1391 | add_page_to_lru_list(page, lruvec, lru); |
1392 | ||
66635629 MG |
1393 | if (is_active_lru(lru)) { |
1394 | int file = is_file_lru(lru); | |
9992af10 RR |
1395 | int numpages = hpage_nr_pages(page); |
1396 | reclaim_stat->recent_rotated[file] += numpages; | |
66635629 | 1397 | } |
2bcf8879 HD |
1398 | if (put_page_testzero(page)) { |
1399 | __ClearPageLRU(page); | |
1400 | __ClearPageActive(page); | |
fa9add64 | 1401 | del_page_from_lru_list(page, lruvec, lru); |
2bcf8879 HD |
1402 | |
1403 | if (unlikely(PageCompound(page))) { | |
1404 | spin_unlock_irq(&zone->lru_lock); | |
1405 | (*get_compound_page_dtor(page))(page); | |
1406 | spin_lock_irq(&zone->lru_lock); | |
1407 | } else | |
1408 | list_add(&page->lru, &pages_to_free); | |
66635629 MG |
1409 | } |
1410 | } | |
66635629 | 1411 | |
3f79768f HD |
1412 | /* |
1413 | * To save our caller's stack, now use input list for pages to free. | |
1414 | */ | |
1415 | list_splice(&pages_to_free, page_list); | |
66635629 MG |
1416 | } |
1417 | ||
1da177e4 | 1418 | /* |
1742f19f AM |
1419 | * shrink_inactive_list() is a helper for shrink_zone(). It returns the number |
1420 | * of reclaimed pages | |
1da177e4 | 1421 | */ |
66635629 | 1422 | static noinline_for_stack unsigned long |
1a93be0e | 1423 | shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, |
9e3b2f8c | 1424 | struct scan_control *sc, enum lru_list lru) |
1da177e4 LT |
1425 | { |
1426 | LIST_HEAD(page_list); | |
e247dbce | 1427 | unsigned long nr_scanned; |
05ff5137 | 1428 | unsigned long nr_reclaimed = 0; |
e247dbce | 1429 | unsigned long nr_taken; |
8e950282 MG |
1430 | unsigned long nr_dirty = 0; |
1431 | unsigned long nr_congested = 0; | |
e2be15f6 | 1432 | unsigned long nr_unqueued_dirty = 0; |
92df3a72 | 1433 | unsigned long nr_writeback = 0; |
b1a6f21e | 1434 | unsigned long nr_immediate = 0; |
f3fd4a61 | 1435 | isolate_mode_t isolate_mode = 0; |
3cb99451 | 1436 | int file = is_file_lru(lru); |
1a93be0e KK |
1437 | struct zone *zone = lruvec_zone(lruvec); |
1438 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; | |
78dc583d | 1439 | |
35cd7815 | 1440 | while (unlikely(too_many_isolated(zone, file, sc))) { |
58355c78 | 1441 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
35cd7815 RR |
1442 | |
1443 | /* We are about to die and free our memory. Return now. */ | |
1444 | if (fatal_signal_pending(current)) | |
1445 | return SWAP_CLUSTER_MAX; | |
1446 | } | |
1447 | ||
1da177e4 | 1448 | lru_add_drain(); |
f80c0673 MK |
1449 | |
1450 | if (!sc->may_unmap) | |
61317289 | 1451 | isolate_mode |= ISOLATE_UNMAPPED; |
f80c0673 | 1452 | if (!sc->may_writepage) |
61317289 | 1453 | isolate_mode |= ISOLATE_CLEAN; |
f80c0673 | 1454 | |
1da177e4 | 1455 | spin_lock_irq(&zone->lru_lock); |
b35ea17b | 1456 | |
5dc35979 KK |
1457 | nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list, |
1458 | &nr_scanned, sc, isolate_mode, lru); | |
95d918fc KK |
1459 | |
1460 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken); | |
1461 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); | |
1462 | ||
89b5fae5 | 1463 | if (global_reclaim(sc)) { |
e247dbce KM |
1464 | zone->pages_scanned += nr_scanned; |
1465 | if (current_is_kswapd()) | |
75b00af7 | 1466 | __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned); |
e247dbce | 1467 | else |
75b00af7 | 1468 | __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned); |
e247dbce | 1469 | } |
d563c050 | 1470 | spin_unlock_irq(&zone->lru_lock); |
b35ea17b | 1471 | |
d563c050 | 1472 | if (nr_taken == 0) |
66635629 | 1473 | return 0; |
5ad333eb | 1474 | |
02c6de8d | 1475 | nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP, |
8e950282 MG |
1476 | &nr_dirty, &nr_unqueued_dirty, &nr_congested, |
1477 | &nr_writeback, &nr_immediate, | |
1478 | false); | |
c661b078 | 1479 | |
3f79768f HD |
1480 | spin_lock_irq(&zone->lru_lock); |
1481 | ||
95d918fc | 1482 | reclaim_stat->recent_scanned[file] += nr_taken; |
d563c050 | 1483 | |
904249aa YH |
1484 | if (global_reclaim(sc)) { |
1485 | if (current_is_kswapd()) | |
1486 | __count_zone_vm_events(PGSTEAL_KSWAPD, zone, | |
1487 | nr_reclaimed); | |
1488 | else | |
1489 | __count_zone_vm_events(PGSTEAL_DIRECT, zone, | |
1490 | nr_reclaimed); | |
1491 | } | |
a74609fa | 1492 | |
27ac81d8 | 1493 | putback_inactive_pages(lruvec, &page_list); |
3f79768f | 1494 | |
95d918fc | 1495 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); |
3f79768f HD |
1496 | |
1497 | spin_unlock_irq(&zone->lru_lock); | |
1498 | ||
1499 | free_hot_cold_page_list(&page_list, 1); | |
e11da5b4 | 1500 | |
92df3a72 MG |
1501 | /* |
1502 | * If reclaim is isolating dirty pages under writeback, it implies | |
1503 | * that the long-lived page allocation rate is exceeding the page | |
1504 | * laundering rate. Either the global limits are not being effective | |
1505 | * at throttling processes due to the page distribution throughout | |
1506 | * zones or there is heavy usage of a slow backing device. The | |
1507 | * only option is to throttle from reclaim context which is not ideal | |
1508 | * as there is no guarantee the dirtying process is throttled in the | |
1509 | * same way balance_dirty_pages() manages. | |
1510 | * | |
8e950282 MG |
1511 | * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number |
1512 | * of pages under pages flagged for immediate reclaim and stall if any | |
1513 | * are encountered in the nr_immediate check below. | |
92df3a72 | 1514 | */ |
918fc718 | 1515 | if (nr_writeback && nr_writeback == nr_taken) |
283aba9f | 1516 | zone_set_flag(zone, ZONE_WRITEBACK); |
92df3a72 | 1517 | |
d43006d5 | 1518 | /* |
b1a6f21e MG |
1519 | * memcg will stall in page writeback so only consider forcibly |
1520 | * stalling for global reclaim | |
d43006d5 | 1521 | */ |
b1a6f21e | 1522 | if (global_reclaim(sc)) { |
8e950282 MG |
1523 | /* |
1524 | * Tag a zone as congested if all the dirty pages scanned were | |
1525 | * backed by a congested BDI and wait_iff_congested will stall. | |
1526 | */ | |
1527 | if (nr_dirty && nr_dirty == nr_congested) | |
1528 | zone_set_flag(zone, ZONE_CONGESTED); | |
1529 | ||
b1a6f21e MG |
1530 | /* |
1531 | * If dirty pages are scanned that are not queued for IO, it | |
1532 | * implies that flushers are not keeping up. In this case, flag | |
1533 | * the zone ZONE_TAIL_LRU_DIRTY and kswapd will start writing | |
1534 | * pages from reclaim context. It will forcibly stall in the | |
1535 | * next check. | |
1536 | */ | |
1537 | if (nr_unqueued_dirty == nr_taken) | |
1538 | zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY); | |
1539 | ||
1540 | /* | |
1541 | * In addition, if kswapd scans pages marked marked for | |
1542 | * immediate reclaim and under writeback (nr_immediate), it | |
1543 | * implies that pages are cycling through the LRU faster than | |
1544 | * they are written so also forcibly stall. | |
1545 | */ | |
1546 | if (nr_unqueued_dirty == nr_taken || nr_immediate) | |
1547 | congestion_wait(BLK_RW_ASYNC, HZ/10); | |
e2be15f6 | 1548 | } |
d43006d5 | 1549 | |
8e950282 MG |
1550 | /* |
1551 | * Stall direct reclaim for IO completions if underlying BDIs or zone | |
1552 | * is congested. Allow kswapd to continue until it starts encountering | |
1553 | * unqueued dirty pages or cycling through the LRU too quickly. | |
1554 | */ | |
1555 | if (!sc->hibernation_mode && !current_is_kswapd()) | |
1556 | wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10); | |
1557 | ||
e11da5b4 MG |
1558 | trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, |
1559 | zone_idx(zone), | |
1560 | nr_scanned, nr_reclaimed, | |
9e3b2f8c | 1561 | sc->priority, |
23b9da55 | 1562 | trace_shrink_flags(file)); |
05ff5137 | 1563 | return nr_reclaimed; |
1da177e4 LT |
1564 | } |
1565 | ||
1566 | /* | |
1567 | * This moves pages from the active list to the inactive list. | |
1568 | * | |
1569 | * We move them the other way if the page is referenced by one or more | |
1570 | * processes, from rmap. | |
1571 | * | |
1572 | * If the pages are mostly unmapped, the processing is fast and it is | |
1573 | * appropriate to hold zone->lru_lock across the whole operation. But if | |
1574 | * the pages are mapped, the processing is slow (page_referenced()) so we | |
1575 | * should drop zone->lru_lock around each page. It's impossible to balance | |
1576 | * this, so instead we remove the pages from the LRU while processing them. | |
1577 | * It is safe to rely on PG_active against the non-LRU pages in here because | |
1578 | * nobody will play with that bit on a non-LRU page. | |
1579 | * | |
1580 | * The downside is that we have to touch page->_count against each page. | |
1581 | * But we had to alter page->flags anyway. | |
1582 | */ | |
1cfb419b | 1583 | |
fa9add64 | 1584 | static void move_active_pages_to_lru(struct lruvec *lruvec, |
3eb4140f | 1585 | struct list_head *list, |
2bcf8879 | 1586 | struct list_head *pages_to_free, |
3eb4140f WF |
1587 | enum lru_list lru) |
1588 | { | |
fa9add64 | 1589 | struct zone *zone = lruvec_zone(lruvec); |
3eb4140f | 1590 | unsigned long pgmoved = 0; |
3eb4140f | 1591 | struct page *page; |
fa9add64 | 1592 | int nr_pages; |
3eb4140f | 1593 | |
3eb4140f WF |
1594 | while (!list_empty(list)) { |
1595 | page = lru_to_page(list); | |
fa9add64 | 1596 | lruvec = mem_cgroup_page_lruvec(page, zone); |
3eb4140f WF |
1597 | |
1598 | VM_BUG_ON(PageLRU(page)); | |
1599 | SetPageLRU(page); | |
1600 | ||
fa9add64 HD |
1601 | nr_pages = hpage_nr_pages(page); |
1602 | mem_cgroup_update_lru_size(lruvec, lru, nr_pages); | |
925b7673 | 1603 | list_move(&page->lru, &lruvec->lists[lru]); |
fa9add64 | 1604 | pgmoved += nr_pages; |
3eb4140f | 1605 | |
2bcf8879 HD |
1606 | if (put_page_testzero(page)) { |
1607 | __ClearPageLRU(page); | |
1608 | __ClearPageActive(page); | |
fa9add64 | 1609 | del_page_from_lru_list(page, lruvec, lru); |
2bcf8879 HD |
1610 | |
1611 | if (unlikely(PageCompound(page))) { | |
1612 | spin_unlock_irq(&zone->lru_lock); | |
1613 | (*get_compound_page_dtor(page))(page); | |
1614 | spin_lock_irq(&zone->lru_lock); | |
1615 | } else | |
1616 | list_add(&page->lru, pages_to_free); | |
3eb4140f WF |
1617 | } |
1618 | } | |
1619 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); | |
1620 | if (!is_active_lru(lru)) | |
1621 | __count_vm_events(PGDEACTIVATE, pgmoved); | |
1622 | } | |
1cfb419b | 1623 | |
f626012d | 1624 | static void shrink_active_list(unsigned long nr_to_scan, |
1a93be0e | 1625 | struct lruvec *lruvec, |
f16015fb | 1626 | struct scan_control *sc, |
9e3b2f8c | 1627 | enum lru_list lru) |
1da177e4 | 1628 | { |
44c241f1 | 1629 | unsigned long nr_taken; |
f626012d | 1630 | unsigned long nr_scanned; |
6fe6b7e3 | 1631 | unsigned long vm_flags; |
1da177e4 | 1632 | LIST_HEAD(l_hold); /* The pages which were snipped off */ |
8cab4754 | 1633 | LIST_HEAD(l_active); |
b69408e8 | 1634 | LIST_HEAD(l_inactive); |
1da177e4 | 1635 | struct page *page; |
1a93be0e | 1636 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
44c241f1 | 1637 | unsigned long nr_rotated = 0; |
f3fd4a61 | 1638 | isolate_mode_t isolate_mode = 0; |
3cb99451 | 1639 | int file = is_file_lru(lru); |
1a93be0e | 1640 | struct zone *zone = lruvec_zone(lruvec); |
1da177e4 LT |
1641 | |
1642 | lru_add_drain(); | |
f80c0673 MK |
1643 | |
1644 | if (!sc->may_unmap) | |
61317289 | 1645 | isolate_mode |= ISOLATE_UNMAPPED; |
f80c0673 | 1646 | if (!sc->may_writepage) |
61317289 | 1647 | isolate_mode |= ISOLATE_CLEAN; |
f80c0673 | 1648 | |
1da177e4 | 1649 | spin_lock_irq(&zone->lru_lock); |
925b7673 | 1650 | |
5dc35979 KK |
1651 | nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold, |
1652 | &nr_scanned, sc, isolate_mode, lru); | |
89b5fae5 | 1653 | if (global_reclaim(sc)) |
f626012d | 1654 | zone->pages_scanned += nr_scanned; |
89b5fae5 | 1655 | |
b7c46d15 | 1656 | reclaim_stat->recent_scanned[file] += nr_taken; |
1cfb419b | 1657 | |
f626012d | 1658 | __count_zone_vm_events(PGREFILL, zone, nr_scanned); |
3cb99451 | 1659 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken); |
a731286d | 1660 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); |
1da177e4 LT |
1661 | spin_unlock_irq(&zone->lru_lock); |
1662 | ||
1da177e4 LT |
1663 | while (!list_empty(&l_hold)) { |
1664 | cond_resched(); | |
1665 | page = lru_to_page(&l_hold); | |
1666 | list_del(&page->lru); | |
7e9cd484 | 1667 | |
39b5f29a | 1668 | if (unlikely(!page_evictable(page))) { |
894bc310 LS |
1669 | putback_lru_page(page); |
1670 | continue; | |
1671 | } | |
1672 | ||
cc715d99 MG |
1673 | if (unlikely(buffer_heads_over_limit)) { |
1674 | if (page_has_private(page) && trylock_page(page)) { | |
1675 | if (page_has_private(page)) | |
1676 | try_to_release_page(page, 0); | |
1677 | unlock_page(page); | |
1678 | } | |
1679 | } | |
1680 | ||
c3ac9a8a JW |
1681 | if (page_referenced(page, 0, sc->target_mem_cgroup, |
1682 | &vm_flags)) { | |
9992af10 | 1683 | nr_rotated += hpage_nr_pages(page); |
8cab4754 WF |
1684 | /* |
1685 | * Identify referenced, file-backed active pages and | |
1686 | * give them one more trip around the active list. So | |
1687 | * that executable code get better chances to stay in | |
1688 | * memory under moderate memory pressure. Anon pages | |
1689 | * are not likely to be evicted by use-once streaming | |
1690 | * IO, plus JVM can create lots of anon VM_EXEC pages, | |
1691 | * so we ignore them here. | |
1692 | */ | |
41e20983 | 1693 | if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { |
8cab4754 WF |
1694 | list_add(&page->lru, &l_active); |
1695 | continue; | |
1696 | } | |
1697 | } | |
7e9cd484 | 1698 | |
5205e56e | 1699 | ClearPageActive(page); /* we are de-activating */ |
1da177e4 LT |
1700 | list_add(&page->lru, &l_inactive); |
1701 | } | |
1702 | ||
b555749a | 1703 | /* |
8cab4754 | 1704 | * Move pages back to the lru list. |
b555749a | 1705 | */ |
2a1dc509 | 1706 | spin_lock_irq(&zone->lru_lock); |
556adecb | 1707 | /* |
8cab4754 WF |
1708 | * Count referenced pages from currently used mappings as rotated, |
1709 | * even though only some of them are actually re-activated. This | |
1710 | * helps balance scan pressure between file and anonymous pages in | |
1711 | * get_scan_ratio. | |
7e9cd484 | 1712 | */ |
b7c46d15 | 1713 | reclaim_stat->recent_rotated[file] += nr_rotated; |
556adecb | 1714 | |
fa9add64 HD |
1715 | move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru); |
1716 | move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE); | |
a731286d | 1717 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); |
f8891e5e | 1718 | spin_unlock_irq(&zone->lru_lock); |
2bcf8879 HD |
1719 | |
1720 | free_hot_cold_page_list(&l_hold, 1); | |
1da177e4 LT |
1721 | } |
1722 | ||
74e3f3c3 | 1723 | #ifdef CONFIG_SWAP |
14797e23 | 1724 | static int inactive_anon_is_low_global(struct zone *zone) |
f89eb90e KM |
1725 | { |
1726 | unsigned long active, inactive; | |
1727 | ||
1728 | active = zone_page_state(zone, NR_ACTIVE_ANON); | |
1729 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); | |
1730 | ||
1731 | if (inactive * zone->inactive_ratio < active) | |
1732 | return 1; | |
1733 | ||
1734 | return 0; | |
1735 | } | |
1736 | ||
14797e23 KM |
1737 | /** |
1738 | * inactive_anon_is_low - check if anonymous pages need to be deactivated | |
c56d5c7d | 1739 | * @lruvec: LRU vector to check |
14797e23 KM |
1740 | * |
1741 | * Returns true if the zone does not have enough inactive anon pages, | |
1742 | * meaning some active anon pages need to be deactivated. | |
1743 | */ | |
c56d5c7d | 1744 | static int inactive_anon_is_low(struct lruvec *lruvec) |
14797e23 | 1745 | { |
74e3f3c3 MK |
1746 | /* |
1747 | * If we don't have swap space, anonymous page deactivation | |
1748 | * is pointless. | |
1749 | */ | |
1750 | if (!total_swap_pages) | |
1751 | return 0; | |
1752 | ||
c3c787e8 | 1753 | if (!mem_cgroup_disabled()) |
c56d5c7d | 1754 | return mem_cgroup_inactive_anon_is_low(lruvec); |
f16015fb | 1755 | |
c56d5c7d | 1756 | return inactive_anon_is_low_global(lruvec_zone(lruvec)); |
14797e23 | 1757 | } |
74e3f3c3 | 1758 | #else |
c56d5c7d | 1759 | static inline int inactive_anon_is_low(struct lruvec *lruvec) |
74e3f3c3 MK |
1760 | { |
1761 | return 0; | |
1762 | } | |
1763 | #endif | |
14797e23 | 1764 | |
56e49d21 RR |
1765 | /** |
1766 | * inactive_file_is_low - check if file pages need to be deactivated | |
c56d5c7d | 1767 | * @lruvec: LRU vector to check |
56e49d21 RR |
1768 | * |
1769 | * When the system is doing streaming IO, memory pressure here | |
1770 | * ensures that active file pages get deactivated, until more | |
1771 | * than half of the file pages are on the inactive list. | |
1772 | * | |
1773 | * Once we get to that situation, protect the system's working | |
1774 | * set from being evicted by disabling active file page aging. | |
1775 | * | |
1776 | * This uses a different ratio than the anonymous pages, because | |
1777 | * the page cache uses a use-once replacement algorithm. | |
1778 | */ | |
c56d5c7d | 1779 | static int inactive_file_is_low(struct lruvec *lruvec) |
56e49d21 | 1780 | { |
e3790144 JW |
1781 | unsigned long inactive; |
1782 | unsigned long active; | |
1783 | ||
1784 | inactive = get_lru_size(lruvec, LRU_INACTIVE_FILE); | |
1785 | active = get_lru_size(lruvec, LRU_ACTIVE_FILE); | |
56e49d21 | 1786 | |
e3790144 | 1787 | return active > inactive; |
56e49d21 RR |
1788 | } |
1789 | ||
75b00af7 | 1790 | static int inactive_list_is_low(struct lruvec *lruvec, enum lru_list lru) |
b39415b2 | 1791 | { |
75b00af7 | 1792 | if (is_file_lru(lru)) |
c56d5c7d | 1793 | return inactive_file_is_low(lruvec); |
b39415b2 | 1794 | else |
c56d5c7d | 1795 | return inactive_anon_is_low(lruvec); |
b39415b2 RR |
1796 | } |
1797 | ||
4f98a2fe | 1798 | static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, |
1a93be0e | 1799 | struct lruvec *lruvec, struct scan_control *sc) |
b69408e8 | 1800 | { |
b39415b2 | 1801 | if (is_active_lru(lru)) { |
75b00af7 | 1802 | if (inactive_list_is_low(lruvec, lru)) |
1a93be0e | 1803 | shrink_active_list(nr_to_scan, lruvec, sc, lru); |
556adecb RR |
1804 | return 0; |
1805 | } | |
1806 | ||
1a93be0e | 1807 | return shrink_inactive_list(nr_to_scan, lruvec, sc, lru); |
4f98a2fe RR |
1808 | } |
1809 | ||
3d58ab5c | 1810 | static int vmscan_swappiness(struct scan_control *sc) |
1f4c025b | 1811 | { |
89b5fae5 | 1812 | if (global_reclaim(sc)) |
1f4c025b | 1813 | return vm_swappiness; |
3d58ab5c | 1814 | return mem_cgroup_swappiness(sc->target_mem_cgroup); |
1f4c025b KH |
1815 | } |
1816 | ||
9a265114 JW |
1817 | enum scan_balance { |
1818 | SCAN_EQUAL, | |
1819 | SCAN_FRACT, | |
1820 | SCAN_ANON, | |
1821 | SCAN_FILE, | |
1822 | }; | |
1823 | ||
4f98a2fe RR |
1824 | /* |
1825 | * Determine how aggressively the anon and file LRU lists should be | |
1826 | * scanned. The relative value of each set of LRU lists is determined | |
1827 | * by looking at the fraction of the pages scanned we did rotate back | |
1828 | * onto the active list instead of evict. | |
1829 | * | |
be7bd59d WL |
1830 | * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan |
1831 | * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan | |
4f98a2fe | 1832 | */ |
90126375 | 1833 | static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, |
9e3b2f8c | 1834 | unsigned long *nr) |
4f98a2fe | 1835 | { |
9a265114 JW |
1836 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
1837 | u64 fraction[2]; | |
1838 | u64 denominator = 0; /* gcc */ | |
1839 | struct zone *zone = lruvec_zone(lruvec); | |
4f98a2fe | 1840 | unsigned long anon_prio, file_prio; |
9a265114 JW |
1841 | enum scan_balance scan_balance; |
1842 | unsigned long anon, file, free; | |
1843 | bool force_scan = false; | |
4f98a2fe | 1844 | unsigned long ap, fp; |
4111304d | 1845 | enum lru_list lru; |
246e87a9 | 1846 | |
f11c0ca5 JW |
1847 | /* |
1848 | * If the zone or memcg is small, nr[l] can be 0. This | |
1849 | * results in no scanning on this priority and a potential | |
1850 | * priority drop. Global direct reclaim can go to the next | |
1851 | * zone and tends to have no problems. Global kswapd is for | |
1852 | * zone balancing and it needs to scan a minimum amount. When | |
1853 | * reclaiming for a memcg, a priority drop can cause high | |
1854 | * latencies, so it's better to scan a minimum amount there as | |
1855 | * well. | |
1856 | */ | |
6e543d57 | 1857 | if (current_is_kswapd() && !zone_reclaimable(zone)) |
a4d3e9e7 | 1858 | force_scan = true; |
89b5fae5 | 1859 | if (!global_reclaim(sc)) |
a4d3e9e7 | 1860 | force_scan = true; |
76a33fc3 SL |
1861 | |
1862 | /* If we have no swap space, do not bother scanning anon pages. */ | |
ec8acf20 | 1863 | if (!sc->may_swap || (get_nr_swap_pages() <= 0)) { |
9a265114 | 1864 | scan_balance = SCAN_FILE; |
76a33fc3 SL |
1865 | goto out; |
1866 | } | |
4f98a2fe | 1867 | |
10316b31 JW |
1868 | /* |
1869 | * Global reclaim will swap to prevent OOM even with no | |
1870 | * swappiness, but memcg users want to use this knob to | |
1871 | * disable swapping for individual groups completely when | |
1872 | * using the memory controller's swap limit feature would be | |
1873 | * too expensive. | |
1874 | */ | |
1875 | if (!global_reclaim(sc) && !vmscan_swappiness(sc)) { | |
9a265114 | 1876 | scan_balance = SCAN_FILE; |
10316b31 JW |
1877 | goto out; |
1878 | } | |
1879 | ||
1880 | /* | |
1881 | * Do not apply any pressure balancing cleverness when the | |
1882 | * system is close to OOM, scan both anon and file equally | |
1883 | * (unless the swappiness setting disagrees with swapping). | |
1884 | */ | |
1885 | if (!sc->priority && vmscan_swappiness(sc)) { | |
9a265114 | 1886 | scan_balance = SCAN_EQUAL; |
10316b31 JW |
1887 | goto out; |
1888 | } | |
1889 | ||
4d7dcca2 HD |
1890 | anon = get_lru_size(lruvec, LRU_ACTIVE_ANON) + |
1891 | get_lru_size(lruvec, LRU_INACTIVE_ANON); | |
1892 | file = get_lru_size(lruvec, LRU_ACTIVE_FILE) + | |
1893 | get_lru_size(lruvec, LRU_INACTIVE_FILE); | |
a4d3e9e7 | 1894 | |
11d16c25 JW |
1895 | /* |
1896 | * If it's foreseeable that reclaiming the file cache won't be | |
1897 | * enough to get the zone back into a desirable shape, we have | |
1898 | * to swap. Better start now and leave the - probably heavily | |
1899 | * thrashing - remaining file pages alone. | |
1900 | */ | |
89b5fae5 | 1901 | if (global_reclaim(sc)) { |
11d16c25 | 1902 | free = zone_page_state(zone, NR_FREE_PAGES); |
90126375 | 1903 | if (unlikely(file + free <= high_wmark_pages(zone))) { |
9a265114 | 1904 | scan_balance = SCAN_ANON; |
76a33fc3 | 1905 | goto out; |
eeee9a8c | 1906 | } |
4f98a2fe RR |
1907 | } |
1908 | ||
7c5bd705 JW |
1909 | /* |
1910 | * There is enough inactive page cache, do not reclaim | |
1911 | * anything from the anonymous working set right now. | |
1912 | */ | |
1913 | if (!inactive_file_is_low(lruvec)) { | |
9a265114 | 1914 | scan_balance = SCAN_FILE; |
7c5bd705 JW |
1915 | goto out; |
1916 | } | |
1917 | ||
9a265114 JW |
1918 | scan_balance = SCAN_FRACT; |
1919 | ||
58c37f6e KM |
1920 | /* |
1921 | * With swappiness at 100, anonymous and file have the same priority. | |
1922 | * This scanning priority is essentially the inverse of IO cost. | |
1923 | */ | |
3d58ab5c | 1924 | anon_prio = vmscan_swappiness(sc); |
75b00af7 | 1925 | file_prio = 200 - anon_prio; |
58c37f6e | 1926 | |
4f98a2fe RR |
1927 | /* |
1928 | * OK, so we have swap space and a fair amount of page cache | |
1929 | * pages. We use the recently rotated / recently scanned | |
1930 | * ratios to determine how valuable each cache is. | |
1931 | * | |
1932 | * Because workloads change over time (and to avoid overflow) | |
1933 | * we keep these statistics as a floating average, which ends | |
1934 | * up weighing recent references more than old ones. | |
1935 | * | |
1936 | * anon in [0], file in [1] | |
1937 | */ | |
90126375 | 1938 | spin_lock_irq(&zone->lru_lock); |
6e901571 | 1939 | if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { |
6e901571 KM |
1940 | reclaim_stat->recent_scanned[0] /= 2; |
1941 | reclaim_stat->recent_rotated[0] /= 2; | |
4f98a2fe RR |
1942 | } |
1943 | ||
6e901571 | 1944 | if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { |
6e901571 KM |
1945 | reclaim_stat->recent_scanned[1] /= 2; |
1946 | reclaim_stat->recent_rotated[1] /= 2; | |
4f98a2fe RR |
1947 | } |
1948 | ||
4f98a2fe | 1949 | /* |
00d8089c RR |
1950 | * The amount of pressure on anon vs file pages is inversely |
1951 | * proportional to the fraction of recently scanned pages on | |
1952 | * each list that were recently referenced and in active use. | |
4f98a2fe | 1953 | */ |
fe35004f | 1954 | ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1); |
6e901571 | 1955 | ap /= reclaim_stat->recent_rotated[0] + 1; |
4f98a2fe | 1956 | |
fe35004f | 1957 | fp = file_prio * (reclaim_stat->recent_scanned[1] + 1); |
6e901571 | 1958 | fp /= reclaim_stat->recent_rotated[1] + 1; |
90126375 | 1959 | spin_unlock_irq(&zone->lru_lock); |
4f98a2fe | 1960 | |
76a33fc3 SL |
1961 | fraction[0] = ap; |
1962 | fraction[1] = fp; | |
1963 | denominator = ap + fp + 1; | |
1964 | out: | |
4111304d HD |
1965 | for_each_evictable_lru(lru) { |
1966 | int file = is_file_lru(lru); | |
d778df51 | 1967 | unsigned long size; |
76a33fc3 | 1968 | unsigned long scan; |
6e08a369 | 1969 | |
d778df51 | 1970 | size = get_lru_size(lruvec, lru); |
10316b31 | 1971 | scan = size >> sc->priority; |
9a265114 | 1972 | |
10316b31 JW |
1973 | if (!scan && force_scan) |
1974 | scan = min(size, SWAP_CLUSTER_MAX); | |
9a265114 JW |
1975 | |
1976 | switch (scan_balance) { | |
1977 | case SCAN_EQUAL: | |
1978 | /* Scan lists relative to size */ | |
1979 | break; | |
1980 | case SCAN_FRACT: | |
1981 | /* | |
1982 | * Scan types proportional to swappiness and | |
1983 | * their relative recent reclaim efficiency. | |
1984 | */ | |
1985 | scan = div64_u64(scan * fraction[file], denominator); | |
1986 | break; | |
1987 | case SCAN_FILE: | |
1988 | case SCAN_ANON: | |
1989 | /* Scan one type exclusively */ | |
1990 | if ((scan_balance == SCAN_FILE) != file) | |
1991 | scan = 0; | |
1992 | break; | |
1993 | default: | |
1994 | /* Look ma, no brain */ | |
1995 | BUG(); | |
1996 | } | |
4111304d | 1997 | nr[lru] = scan; |
76a33fc3 | 1998 | } |
6e08a369 | 1999 | } |
4f98a2fe | 2000 | |
9b4f98cd JW |
2001 | /* |
2002 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. | |
2003 | */ | |
2004 | static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) | |
2005 | { | |
2006 | unsigned long nr[NR_LRU_LISTS]; | |
e82e0561 | 2007 | unsigned long targets[NR_LRU_LISTS]; |
9b4f98cd JW |
2008 | unsigned long nr_to_scan; |
2009 | enum lru_list lru; | |
2010 | unsigned long nr_reclaimed = 0; | |
2011 | unsigned long nr_to_reclaim = sc->nr_to_reclaim; | |
2012 | struct blk_plug plug; | |
e82e0561 | 2013 | bool scan_adjusted = false; |
9b4f98cd JW |
2014 | |
2015 | get_scan_count(lruvec, sc, nr); | |
2016 | ||
e82e0561 MG |
2017 | /* Record the original scan target for proportional adjustments later */ |
2018 | memcpy(targets, nr, sizeof(nr)); | |
2019 | ||
9b4f98cd JW |
2020 | blk_start_plug(&plug); |
2021 | while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || | |
2022 | nr[LRU_INACTIVE_FILE]) { | |
e82e0561 MG |
2023 | unsigned long nr_anon, nr_file, percentage; |
2024 | unsigned long nr_scanned; | |
2025 | ||
9b4f98cd JW |
2026 | for_each_evictable_lru(lru) { |
2027 | if (nr[lru]) { | |
2028 | nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX); | |
2029 | nr[lru] -= nr_to_scan; | |
2030 | ||
2031 | nr_reclaimed += shrink_list(lru, nr_to_scan, | |
2032 | lruvec, sc); | |
2033 | } | |
2034 | } | |
e82e0561 MG |
2035 | |
2036 | if (nr_reclaimed < nr_to_reclaim || scan_adjusted) | |
2037 | continue; | |
2038 | ||
9b4f98cd | 2039 | /* |
e82e0561 MG |
2040 | * For global direct reclaim, reclaim only the number of pages |
2041 | * requested. Less care is taken to scan proportionally as it | |
2042 | * is more important to minimise direct reclaim stall latency | |
2043 | * than it is to properly age the LRU lists. | |
9b4f98cd | 2044 | */ |
e82e0561 | 2045 | if (global_reclaim(sc) && !current_is_kswapd()) |
9b4f98cd | 2046 | break; |
e82e0561 MG |
2047 | |
2048 | /* | |
2049 | * For kswapd and memcg, reclaim at least the number of pages | |
2050 | * requested. Ensure that the anon and file LRUs shrink | |
2051 | * proportionally what was requested by get_scan_count(). We | |
2052 | * stop reclaiming one LRU and reduce the amount scanning | |
2053 | * proportional to the original scan target. | |
2054 | */ | |
2055 | nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE]; | |
2056 | nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON]; | |
2057 | ||
2058 | if (nr_file > nr_anon) { | |
2059 | unsigned long scan_target = targets[LRU_INACTIVE_ANON] + | |
2060 | targets[LRU_ACTIVE_ANON] + 1; | |
2061 | lru = LRU_BASE; | |
2062 | percentage = nr_anon * 100 / scan_target; | |
2063 | } else { | |
2064 | unsigned long scan_target = targets[LRU_INACTIVE_FILE] + | |
2065 | targets[LRU_ACTIVE_FILE] + 1; | |
2066 | lru = LRU_FILE; | |
2067 | percentage = nr_file * 100 / scan_target; | |
2068 | } | |
2069 | ||
2070 | /* Stop scanning the smaller of the LRU */ | |
2071 | nr[lru] = 0; | |
2072 | nr[lru + LRU_ACTIVE] = 0; | |
2073 | ||
2074 | /* | |
2075 | * Recalculate the other LRU scan count based on its original | |
2076 | * scan target and the percentage scanning already complete | |
2077 | */ | |
2078 | lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE; | |
2079 | nr_scanned = targets[lru] - nr[lru]; | |
2080 | nr[lru] = targets[lru] * (100 - percentage) / 100; | |
2081 | nr[lru] -= min(nr[lru], nr_scanned); | |
2082 | ||
2083 | lru += LRU_ACTIVE; | |
2084 | nr_scanned = targets[lru] - nr[lru]; | |
2085 | nr[lru] = targets[lru] * (100 - percentage) / 100; | |
2086 | nr[lru] -= min(nr[lru], nr_scanned); | |
2087 | ||
2088 | scan_adjusted = true; | |
9b4f98cd JW |
2089 | } |
2090 | blk_finish_plug(&plug); | |
2091 | sc->nr_reclaimed += nr_reclaimed; | |
2092 | ||
2093 | /* | |
2094 | * Even if we did not try to evict anon pages at all, we want to | |
2095 | * rebalance the anon lru active/inactive ratio. | |
2096 | */ | |
2097 | if (inactive_anon_is_low(lruvec)) | |
2098 | shrink_active_list(SWAP_CLUSTER_MAX, lruvec, | |
2099 | sc, LRU_ACTIVE_ANON); | |
2100 | ||
2101 | throttle_vm_writeout(sc->gfp_mask); | |
2102 | } | |
2103 | ||
23b9da55 | 2104 | /* Use reclaim/compaction for costly allocs or under memory pressure */ |
9e3b2f8c | 2105 | static bool in_reclaim_compaction(struct scan_control *sc) |
23b9da55 | 2106 | { |
d84da3f9 | 2107 | if (IS_ENABLED(CONFIG_COMPACTION) && sc->order && |
23b9da55 | 2108 | (sc->order > PAGE_ALLOC_COSTLY_ORDER || |
9e3b2f8c | 2109 | sc->priority < DEF_PRIORITY - 2)) |
23b9da55 MG |
2110 | return true; |
2111 | ||
2112 | return false; | |
2113 | } | |
2114 | ||
3e7d3449 | 2115 | /* |
23b9da55 MG |
2116 | * Reclaim/compaction is used for high-order allocation requests. It reclaims |
2117 | * order-0 pages before compacting the zone. should_continue_reclaim() returns | |
2118 | * true if more pages should be reclaimed such that when the page allocator | |
2119 | * calls try_to_compact_zone() that it will have enough free pages to succeed. | |
2120 | * It will give up earlier than that if there is difficulty reclaiming pages. | |
3e7d3449 | 2121 | */ |
9b4f98cd | 2122 | static inline bool should_continue_reclaim(struct zone *zone, |
3e7d3449 MG |
2123 | unsigned long nr_reclaimed, |
2124 | unsigned long nr_scanned, | |
2125 | struct scan_control *sc) | |
2126 | { | |
2127 | unsigned long pages_for_compaction; | |
2128 | unsigned long inactive_lru_pages; | |
2129 | ||
2130 | /* If not in reclaim/compaction mode, stop */ | |
9e3b2f8c | 2131 | if (!in_reclaim_compaction(sc)) |
3e7d3449 MG |
2132 | return false; |
2133 | ||
2876592f MG |
2134 | /* Consider stopping depending on scan and reclaim activity */ |
2135 | if (sc->gfp_mask & __GFP_REPEAT) { | |
2136 | /* | |
2137 | * For __GFP_REPEAT allocations, stop reclaiming if the | |
2138 | * full LRU list has been scanned and we are still failing | |
2139 | * to reclaim pages. This full LRU scan is potentially | |
2140 | * expensive but a __GFP_REPEAT caller really wants to succeed | |
2141 | */ | |
2142 | if (!nr_reclaimed && !nr_scanned) | |
2143 | return false; | |
2144 | } else { | |
2145 | /* | |
2146 | * For non-__GFP_REPEAT allocations which can presumably | |
2147 | * fail without consequence, stop if we failed to reclaim | |
2148 | * any pages from the last SWAP_CLUSTER_MAX number of | |
2149 | * pages that were scanned. This will return to the | |
2150 | * caller faster at the risk reclaim/compaction and | |
2151 | * the resulting allocation attempt fails | |
2152 | */ | |
2153 | if (!nr_reclaimed) | |
2154 | return false; | |
2155 | } | |
3e7d3449 MG |
2156 | |
2157 | /* | |
2158 | * If we have not reclaimed enough pages for compaction and the | |
2159 | * inactive lists are large enough, continue reclaiming | |
2160 | */ | |
2161 | pages_for_compaction = (2UL << sc->order); | |
9b4f98cd | 2162 | inactive_lru_pages = zone_page_state(zone, NR_INACTIVE_FILE); |
ec8acf20 | 2163 | if (get_nr_swap_pages() > 0) |
9b4f98cd | 2164 | inactive_lru_pages += zone_page_state(zone, NR_INACTIVE_ANON); |
3e7d3449 MG |
2165 | if (sc->nr_reclaimed < pages_for_compaction && |
2166 | inactive_lru_pages > pages_for_compaction) | |
2167 | return true; | |
2168 | ||
2169 | /* If compaction would go ahead or the allocation would succeed, stop */ | |
9b4f98cd | 2170 | switch (compaction_suitable(zone, sc->order)) { |
3e7d3449 MG |
2171 | case COMPACT_PARTIAL: |
2172 | case COMPACT_CONTINUE: | |
2173 | return false; | |
2174 | default: | |
2175 | return true; | |
2176 | } | |
2177 | } | |
2178 | ||
e975de99 | 2179 | static int |
3b38722e | 2180 | __shrink_zone(struct zone *zone, struct scan_control *sc, bool soft_reclaim) |
1da177e4 | 2181 | { |
f0fdc5e8 | 2182 | unsigned long nr_reclaimed, nr_scanned; |
e975de99 | 2183 | int groups_scanned = 0; |
1da177e4 | 2184 | |
9b4f98cd JW |
2185 | do { |
2186 | struct mem_cgroup *root = sc->target_mem_cgroup; | |
2187 | struct mem_cgroup_reclaim_cookie reclaim = { | |
2188 | .zone = zone, | |
2189 | .priority = sc->priority, | |
2190 | }; | |
de57780d MH |
2191 | struct mem_cgroup *memcg = NULL; |
2192 | mem_cgroup_iter_filter filter = (soft_reclaim) ? | |
2193 | mem_cgroup_soft_reclaim_eligible : NULL; | |
3e7d3449 | 2194 | |
9b4f98cd JW |
2195 | nr_reclaimed = sc->nr_reclaimed; |
2196 | nr_scanned = sc->nr_scanned; | |
1da177e4 | 2197 | |
de57780d | 2198 | while ((memcg = mem_cgroup_iter_cond(root, memcg, &reclaim, filter))) { |
9b4f98cd | 2199 | struct lruvec *lruvec; |
5660048c | 2200 | |
e975de99 | 2201 | groups_scanned++; |
9b4f98cd | 2202 | lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
f9be23d6 | 2203 | |
9b4f98cd | 2204 | shrink_lruvec(lruvec, sc); |
f16015fb | 2205 | |
9b4f98cd | 2206 | /* |
a394cb8e MH |
2207 | * Direct reclaim and kswapd have to scan all memory |
2208 | * cgroups to fulfill the overall scan target for the | |
9b4f98cd | 2209 | * zone. |
a394cb8e MH |
2210 | * |
2211 | * Limit reclaim, on the other hand, only cares about | |
2212 | * nr_to_reclaim pages to be reclaimed and it will | |
2213 | * retry with decreasing priority if one round over the | |
2214 | * whole hierarchy is not sufficient. | |
9b4f98cd | 2215 | */ |
a394cb8e MH |
2216 | if (!global_reclaim(sc) && |
2217 | sc->nr_reclaimed >= sc->nr_to_reclaim) { | |
9b4f98cd JW |
2218 | mem_cgroup_iter_break(root, memcg); |
2219 | break; | |
2220 | } | |
de57780d | 2221 | } |
70ddf637 AV |
2222 | |
2223 | vmpressure(sc->gfp_mask, sc->target_mem_cgroup, | |
2224 | sc->nr_scanned - nr_scanned, | |
2225 | sc->nr_reclaimed - nr_reclaimed); | |
2226 | ||
9b4f98cd JW |
2227 | } while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed, |
2228 | sc->nr_scanned - nr_scanned, sc)); | |
e975de99 MH |
2229 | |
2230 | return groups_scanned; | |
f16015fb JW |
2231 | } |
2232 | ||
3b38722e MH |
2233 | |
2234 | static void shrink_zone(struct zone *zone, struct scan_control *sc) | |
2235 | { | |
2236 | bool do_soft_reclaim = mem_cgroup_should_soft_reclaim(sc); | |
2237 | unsigned long nr_scanned = sc->nr_scanned; | |
e975de99 | 2238 | int scanned_groups; |
3b38722e | 2239 | |
e975de99 MH |
2240 | scanned_groups = __shrink_zone(zone, sc, do_soft_reclaim); |
2241 | /* | |
f894ffa8 AM |
2242 | * memcg iterator might race with other reclaimer or start from |
2243 | * a incomplete tree walk so the tree walk in __shrink_zone | |
2244 | * might have missed groups that are above the soft limit. Try | |
2245 | * another loop to catch up with others. Do it just once to | |
2246 | * prevent from reclaim latencies when other reclaimers always | |
2247 | * preempt this one. | |
e975de99 MH |
2248 | */ |
2249 | if (do_soft_reclaim && !scanned_groups) | |
2250 | __shrink_zone(zone, sc, do_soft_reclaim); | |
3b38722e MH |
2251 | |
2252 | /* | |
2253 | * No group is over the soft limit or those that are do not have | |
2254 | * pages in the zone we are reclaiming so we have to reclaim everybody | |
2255 | */ | |
2256 | if (do_soft_reclaim && (sc->nr_scanned == nr_scanned)) { | |
2257 | __shrink_zone(zone, sc, false); | |
2258 | return; | |
2259 | } | |
f16015fb JW |
2260 | } |
2261 | ||
fe4b1b24 MG |
2262 | /* Returns true if compaction should go ahead for a high-order request */ |
2263 | static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) | |
2264 | { | |
2265 | unsigned long balance_gap, watermark; | |
2266 | bool watermark_ok; | |
2267 | ||
2268 | /* Do not consider compaction for orders reclaim is meant to satisfy */ | |
2269 | if (sc->order <= PAGE_ALLOC_COSTLY_ORDER) | |
2270 | return false; | |
2271 | ||
2272 | /* | |
2273 | * Compaction takes time to run and there are potentially other | |
2274 | * callers using the pages just freed. Continue reclaiming until | |
2275 | * there is a buffer of free pages available to give compaction | |
2276 | * a reasonable chance of completing and allocating the page | |
2277 | */ | |
2278 | balance_gap = min(low_wmark_pages(zone), | |
b40da049 | 2279 | (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / |
fe4b1b24 MG |
2280 | KSWAPD_ZONE_BALANCE_GAP_RATIO); |
2281 | watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order); | |
2282 | watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0); | |
2283 | ||
2284 | /* | |
2285 | * If compaction is deferred, reclaim up to a point where | |
2286 | * compaction will have a chance of success when re-enabled | |
2287 | */ | |
aff62249 | 2288 | if (compaction_deferred(zone, sc->order)) |
fe4b1b24 MG |
2289 | return watermark_ok; |
2290 | ||
2291 | /* If compaction is not ready to start, keep reclaiming */ | |
2292 | if (!compaction_suitable(zone, sc->order)) | |
2293 | return false; | |
2294 | ||
2295 | return watermark_ok; | |
2296 | } | |
2297 | ||
1da177e4 LT |
2298 | /* |
2299 | * This is the direct reclaim path, for page-allocating processes. We only | |
2300 | * try to reclaim pages from zones which will satisfy the caller's allocation | |
2301 | * request. | |
2302 | * | |
41858966 MG |
2303 | * We reclaim from a zone even if that zone is over high_wmark_pages(zone). |
2304 | * Because: | |
1da177e4 LT |
2305 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order |
2306 | * allocation or | |
41858966 MG |
2307 | * b) The target zone may be at high_wmark_pages(zone) but the lower zones |
2308 | * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' | |
2309 | * zone defense algorithm. | |
1da177e4 | 2310 | * |
1da177e4 LT |
2311 | * If a zone is deemed to be full of pinned pages then just give it a light |
2312 | * scan then give up on it. | |
e0c23279 MG |
2313 | * |
2314 | * This function returns true if a zone is being reclaimed for a costly | |
fe4b1b24 | 2315 | * high-order allocation and compaction is ready to begin. This indicates to |
0cee34fd MG |
2316 | * the caller that it should consider retrying the allocation instead of |
2317 | * further reclaim. | |
1da177e4 | 2318 | */ |
9e3b2f8c | 2319 | static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) |
1da177e4 | 2320 | { |
dd1a239f | 2321 | struct zoneref *z; |
54a6eb5c | 2322 | struct zone *zone; |
0cee34fd | 2323 | bool aborted_reclaim = false; |
1cfb419b | 2324 | |
cc715d99 MG |
2325 | /* |
2326 | * If the number of buffer_heads in the machine exceeds the maximum | |
2327 | * allowed level, force direct reclaim to scan the highmem zone as | |
2328 | * highmem pages could be pinning lowmem pages storing buffer_heads | |
2329 | */ | |
2330 | if (buffer_heads_over_limit) | |
2331 | sc->gfp_mask |= __GFP_HIGHMEM; | |
2332 | ||
d4debc66 MG |
2333 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
2334 | gfp_zone(sc->gfp_mask), sc->nodemask) { | |
f3fe6512 | 2335 | if (!populated_zone(zone)) |
1da177e4 | 2336 | continue; |
1cfb419b KH |
2337 | /* |
2338 | * Take care memory controller reclaiming has small influence | |
2339 | * to global LRU. | |
2340 | */ | |
89b5fae5 | 2341 | if (global_reclaim(sc)) { |
1cfb419b KH |
2342 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2343 | continue; | |
6e543d57 LD |
2344 | if (sc->priority != DEF_PRIORITY && |
2345 | !zone_reclaimable(zone)) | |
1cfb419b | 2346 | continue; /* Let kswapd poll it */ |
d84da3f9 | 2347 | if (IS_ENABLED(CONFIG_COMPACTION)) { |
e0887c19 | 2348 | /* |
e0c23279 MG |
2349 | * If we already have plenty of memory free for |
2350 | * compaction in this zone, don't free any more. | |
2351 | * Even though compaction is invoked for any | |
2352 | * non-zero order, only frequent costly order | |
2353 | * reclamation is disruptive enough to become a | |
c7cfa37b CA |
2354 | * noticeable problem, like transparent huge |
2355 | * page allocations. | |
e0887c19 | 2356 | */ |
fe4b1b24 | 2357 | if (compaction_ready(zone, sc)) { |
0cee34fd | 2358 | aborted_reclaim = true; |
e0887c19 | 2359 | continue; |
e0c23279 | 2360 | } |
e0887c19 | 2361 | } |
ac34a1a3 | 2362 | /* need some check for avoid more shrink_zone() */ |
1cfb419b | 2363 | } |
408d8544 | 2364 | |
9e3b2f8c | 2365 | shrink_zone(zone, sc); |
1da177e4 | 2366 | } |
e0c23279 | 2367 | |
0cee34fd | 2368 | return aborted_reclaim; |
d1908362 MK |
2369 | } |
2370 | ||
929bea7c | 2371 | /* All zones in zonelist are unreclaimable? */ |
d1908362 MK |
2372 | static bool all_unreclaimable(struct zonelist *zonelist, |
2373 | struct scan_control *sc) | |
2374 | { | |
2375 | struct zoneref *z; | |
2376 | struct zone *zone; | |
d1908362 MK |
2377 | |
2378 | for_each_zone_zonelist_nodemask(zone, z, zonelist, | |
2379 | gfp_zone(sc->gfp_mask), sc->nodemask) { | |
2380 | if (!populated_zone(zone)) | |
2381 | continue; | |
2382 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) | |
2383 | continue; | |
6e543d57 | 2384 | if (zone_reclaimable(zone)) |
929bea7c | 2385 | return false; |
d1908362 MK |
2386 | } |
2387 | ||
929bea7c | 2388 | return true; |
1da177e4 | 2389 | } |
4f98a2fe | 2390 | |
1da177e4 LT |
2391 | /* |
2392 | * This is the main entry point to direct page reclaim. | |
2393 | * | |
2394 | * If a full scan of the inactive list fails to free enough memory then we | |
2395 | * are "out of memory" and something needs to be killed. | |
2396 | * | |
2397 | * If the caller is !__GFP_FS then the probability of a failure is reasonably | |
2398 | * high - the zone may be full of dirty or under-writeback pages, which this | |
5b0830cb JA |
2399 | * caller can't do much about. We kick the writeback threads and take explicit |
2400 | * naps in the hope that some of these pages can be written. But if the | |
2401 | * allocating task holds filesystem locks which prevent writeout this might not | |
2402 | * work, and the allocation attempt will fail. | |
a41f24ea NA |
2403 | * |
2404 | * returns: 0, if no pages reclaimed | |
2405 | * else, the number of pages reclaimed | |
1da177e4 | 2406 | */ |
dac1d27b | 2407 | static unsigned long do_try_to_free_pages(struct zonelist *zonelist, |
a09ed5e0 YH |
2408 | struct scan_control *sc, |
2409 | struct shrink_control *shrink) | |
1da177e4 | 2410 | { |
69e05944 | 2411 | unsigned long total_scanned = 0; |
1da177e4 | 2412 | struct reclaim_state *reclaim_state = current->reclaim_state; |
dd1a239f | 2413 | struct zoneref *z; |
54a6eb5c | 2414 | struct zone *zone; |
22fba335 | 2415 | unsigned long writeback_threshold; |
0cee34fd | 2416 | bool aborted_reclaim; |
1da177e4 | 2417 | |
873b4771 KK |
2418 | delayacct_freepages_start(); |
2419 | ||
89b5fae5 | 2420 | if (global_reclaim(sc)) |
1cfb419b | 2421 | count_vm_event(ALLOCSTALL); |
1da177e4 | 2422 | |
9e3b2f8c | 2423 | do { |
70ddf637 AV |
2424 | vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup, |
2425 | sc->priority); | |
66e1707b | 2426 | sc->nr_scanned = 0; |
9e3b2f8c | 2427 | aborted_reclaim = shrink_zones(zonelist, sc); |
e0c23279 | 2428 | |
66e1707b | 2429 | /* |
5a1c9cbc MG |
2430 | * Don't shrink slabs when reclaiming memory from over limit |
2431 | * cgroups but do shrink slab at least once when aborting | |
2432 | * reclaim for compaction to avoid unevenly scanning file/anon | |
2433 | * LRU pages over slab pages. | |
66e1707b | 2434 | */ |
89b5fae5 | 2435 | if (global_reclaim(sc)) { |
c6a8a8c5 | 2436 | unsigned long lru_pages = 0; |
0ce3d744 DC |
2437 | |
2438 | nodes_clear(shrink->nodes_to_scan); | |
d4debc66 MG |
2439 | for_each_zone_zonelist(zone, z, zonelist, |
2440 | gfp_zone(sc->gfp_mask)) { | |
c6a8a8c5 KM |
2441 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
2442 | continue; | |
2443 | ||
2444 | lru_pages += zone_reclaimable_pages(zone); | |
0ce3d744 DC |
2445 | node_set(zone_to_nid(zone), |
2446 | shrink->nodes_to_scan); | |
c6a8a8c5 KM |
2447 | } |
2448 | ||
1495f230 | 2449 | shrink_slab(shrink, sc->nr_scanned, lru_pages); |
91a45470 | 2450 | if (reclaim_state) { |
a79311c1 | 2451 | sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
91a45470 KH |
2452 | reclaim_state->reclaimed_slab = 0; |
2453 | } | |
1da177e4 | 2454 | } |
66e1707b | 2455 | total_scanned += sc->nr_scanned; |
bb21c7ce | 2456 | if (sc->nr_reclaimed >= sc->nr_to_reclaim) |
1da177e4 | 2457 | goto out; |
1da177e4 | 2458 | |
0e50ce3b MK |
2459 | /* |
2460 | * If we're getting trouble reclaiming, start doing | |
2461 | * writepage even in laptop mode. | |
2462 | */ | |
2463 | if (sc->priority < DEF_PRIORITY - 2) | |
2464 | sc->may_writepage = 1; | |
2465 | ||
1da177e4 LT |
2466 | /* |
2467 | * Try to write back as many pages as we just scanned. This | |
2468 | * tends to cause slow streaming writers to write data to the | |
2469 | * disk smoothly, at the dirtying rate, which is nice. But | |
2470 | * that's undesirable in laptop mode, where we *want* lumpy | |
2471 | * writeout. So in laptop mode, write out the whole world. | |
2472 | */ | |
22fba335 KM |
2473 | writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; |
2474 | if (total_scanned > writeback_threshold) { | |
0e175a18 CW |
2475 | wakeup_flusher_threads(laptop_mode ? 0 : total_scanned, |
2476 | WB_REASON_TRY_TO_FREE_PAGES); | |
66e1707b | 2477 | sc->may_writepage = 1; |
1da177e4 | 2478 | } |
5a1c9cbc | 2479 | } while (--sc->priority >= 0 && !aborted_reclaim); |
bb21c7ce | 2480 | |
1da177e4 | 2481 | out: |
873b4771 KK |
2482 | delayacct_freepages_end(); |
2483 | ||
bb21c7ce KM |
2484 | if (sc->nr_reclaimed) |
2485 | return sc->nr_reclaimed; | |
2486 | ||
929bea7c KM |
2487 | /* |
2488 | * As hibernation is going on, kswapd is freezed so that it can't mark | |
2489 | * the zone into all_unreclaimable. Thus bypassing all_unreclaimable | |
2490 | * check. | |
2491 | */ | |
2492 | if (oom_killer_disabled) | |
2493 | return 0; | |
2494 | ||
0cee34fd MG |
2495 | /* Aborted reclaim to try compaction? don't OOM, then */ |
2496 | if (aborted_reclaim) | |
7335084d MG |
2497 | return 1; |
2498 | ||
bb21c7ce | 2499 | /* top priority shrink_zones still had more to do? don't OOM, then */ |
89b5fae5 | 2500 | if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc)) |
bb21c7ce KM |
2501 | return 1; |
2502 | ||
2503 | return 0; | |
1da177e4 LT |
2504 | } |
2505 | ||
5515061d MG |
2506 | static bool pfmemalloc_watermark_ok(pg_data_t *pgdat) |
2507 | { | |
2508 | struct zone *zone; | |
2509 | unsigned long pfmemalloc_reserve = 0; | |
2510 | unsigned long free_pages = 0; | |
2511 | int i; | |
2512 | bool wmark_ok; | |
2513 | ||
2514 | for (i = 0; i <= ZONE_NORMAL; i++) { | |
2515 | zone = &pgdat->node_zones[i]; | |
2516 | pfmemalloc_reserve += min_wmark_pages(zone); | |
2517 | free_pages += zone_page_state(zone, NR_FREE_PAGES); | |
2518 | } | |
2519 | ||
2520 | wmark_ok = free_pages > pfmemalloc_reserve / 2; | |
2521 | ||
2522 | /* kswapd must be awake if processes are being throttled */ | |
2523 | if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) { | |
2524 | pgdat->classzone_idx = min(pgdat->classzone_idx, | |
2525 | (enum zone_type)ZONE_NORMAL); | |
2526 | wake_up_interruptible(&pgdat->kswapd_wait); | |
2527 | } | |
2528 | ||
2529 | return wmark_ok; | |
2530 | } | |
2531 | ||
2532 | /* | |
2533 | * Throttle direct reclaimers if backing storage is backed by the network | |
2534 | * and the PFMEMALLOC reserve for the preferred node is getting dangerously | |
2535 | * depleted. kswapd will continue to make progress and wake the processes | |
50694c28 MG |
2536 | * when the low watermark is reached. |
2537 | * | |
2538 | * Returns true if a fatal signal was delivered during throttling. If this | |
2539 | * happens, the page allocator should not consider triggering the OOM killer. | |
5515061d | 2540 | */ |
50694c28 | 2541 | static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist, |
5515061d MG |
2542 | nodemask_t *nodemask) |
2543 | { | |
2544 | struct zone *zone; | |
2545 | int high_zoneidx = gfp_zone(gfp_mask); | |
2546 | pg_data_t *pgdat; | |
2547 | ||
2548 | /* | |
2549 | * Kernel threads should not be throttled as they may be indirectly | |
2550 | * responsible for cleaning pages necessary for reclaim to make forward | |
2551 | * progress. kjournald for example may enter direct reclaim while | |
2552 | * committing a transaction where throttling it could forcing other | |
2553 | * processes to block on log_wait_commit(). | |
2554 | */ | |
2555 | if (current->flags & PF_KTHREAD) | |
50694c28 MG |
2556 | goto out; |
2557 | ||
2558 | /* | |
2559 | * If a fatal signal is pending, this process should not throttle. | |
2560 | * It should return quickly so it can exit and free its memory | |
2561 | */ | |
2562 | if (fatal_signal_pending(current)) | |
2563 | goto out; | |
5515061d MG |
2564 | |
2565 | /* Check if the pfmemalloc reserves are ok */ | |
2566 | first_zones_zonelist(zonelist, high_zoneidx, NULL, &zone); | |
2567 | pgdat = zone->zone_pgdat; | |
2568 | if (pfmemalloc_watermark_ok(pgdat)) | |
50694c28 | 2569 | goto out; |
5515061d | 2570 | |
68243e76 MG |
2571 | /* Account for the throttling */ |
2572 | count_vm_event(PGSCAN_DIRECT_THROTTLE); | |
2573 | ||
5515061d MG |
2574 | /* |
2575 | * If the caller cannot enter the filesystem, it's possible that it | |
2576 | * is due to the caller holding an FS lock or performing a journal | |
2577 | * transaction in the case of a filesystem like ext[3|4]. In this case, | |
2578 | * it is not safe to block on pfmemalloc_wait as kswapd could be | |
2579 | * blocked waiting on the same lock. Instead, throttle for up to a | |
2580 | * second before continuing. | |
2581 | */ | |
2582 | if (!(gfp_mask & __GFP_FS)) { | |
2583 | wait_event_interruptible_timeout(pgdat->pfmemalloc_wait, | |
2584 | pfmemalloc_watermark_ok(pgdat), HZ); | |
50694c28 MG |
2585 | |
2586 | goto check_pending; | |
5515061d MG |
2587 | } |
2588 | ||
2589 | /* Throttle until kswapd wakes the process */ | |
2590 | wait_event_killable(zone->zone_pgdat->pfmemalloc_wait, | |
2591 | pfmemalloc_watermark_ok(pgdat)); | |
50694c28 MG |
2592 | |
2593 | check_pending: | |
2594 | if (fatal_signal_pending(current)) | |
2595 | return true; | |
2596 | ||
2597 | out: | |
2598 | return false; | |
5515061d MG |
2599 | } |
2600 | ||
dac1d27b | 2601 | unsigned long try_to_free_pages(struct zonelist *zonelist, int order, |
327c0e96 | 2602 | gfp_t gfp_mask, nodemask_t *nodemask) |
66e1707b | 2603 | { |
33906bc5 | 2604 | unsigned long nr_reclaimed; |
66e1707b | 2605 | struct scan_control sc = { |
21caf2fc | 2606 | .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)), |
66e1707b | 2607 | .may_writepage = !laptop_mode, |
22fba335 | 2608 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
a6dc60f8 | 2609 | .may_unmap = 1, |
2e2e4259 | 2610 | .may_swap = 1, |
66e1707b | 2611 | .order = order, |
9e3b2f8c | 2612 | .priority = DEF_PRIORITY, |
f16015fb | 2613 | .target_mem_cgroup = NULL, |
327c0e96 | 2614 | .nodemask = nodemask, |
66e1707b | 2615 | }; |
a09ed5e0 YH |
2616 | struct shrink_control shrink = { |
2617 | .gfp_mask = sc.gfp_mask, | |
2618 | }; | |
66e1707b | 2619 | |
5515061d | 2620 | /* |
50694c28 MG |
2621 | * Do not enter reclaim if fatal signal was delivered while throttled. |
2622 | * 1 is returned so that the page allocator does not OOM kill at this | |
2623 | * point. | |
5515061d | 2624 | */ |
50694c28 | 2625 | if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask)) |
5515061d MG |
2626 | return 1; |
2627 | ||
33906bc5 MG |
2628 | trace_mm_vmscan_direct_reclaim_begin(order, |
2629 | sc.may_writepage, | |
2630 | gfp_mask); | |
2631 | ||
a09ed5e0 | 2632 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
33906bc5 MG |
2633 | |
2634 | trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); | |
2635 | ||
2636 | return nr_reclaimed; | |
66e1707b BS |
2637 | } |
2638 | ||
c255a458 | 2639 | #ifdef CONFIG_MEMCG |
66e1707b | 2640 | |
72835c86 | 2641 | unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg, |
4e416953 | 2642 | gfp_t gfp_mask, bool noswap, |
0ae5e89c YH |
2643 | struct zone *zone, |
2644 | unsigned long *nr_scanned) | |
4e416953 BS |
2645 | { |
2646 | struct scan_control sc = { | |
0ae5e89c | 2647 | .nr_scanned = 0, |
b8f5c566 | 2648 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
4e416953 BS |
2649 | .may_writepage = !laptop_mode, |
2650 | .may_unmap = 1, | |
2651 | .may_swap = !noswap, | |
4e416953 | 2652 | .order = 0, |
9e3b2f8c | 2653 | .priority = 0, |
72835c86 | 2654 | .target_mem_cgroup = memcg, |
4e416953 | 2655 | }; |
f9be23d6 | 2656 | struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
0ae5e89c | 2657 | |
4e416953 BS |
2658 | sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
2659 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); | |
bdce6d9e | 2660 | |
9e3b2f8c | 2661 | trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order, |
bdce6d9e KM |
2662 | sc.may_writepage, |
2663 | sc.gfp_mask); | |
2664 | ||
4e416953 BS |
2665 | /* |
2666 | * NOTE: Although we can get the priority field, using it | |
2667 | * here is not a good idea, since it limits the pages we can scan. | |
2668 | * if we don't reclaim here, the shrink_zone from balance_pgdat | |
2669 | * will pick up pages from other mem cgroup's as well. We hack | |
2670 | * the priority and make it zero. | |
2671 | */ | |
f9be23d6 | 2672 | shrink_lruvec(lruvec, &sc); |
bdce6d9e KM |
2673 | |
2674 | trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); | |
2675 | ||
0ae5e89c | 2676 | *nr_scanned = sc.nr_scanned; |
4e416953 BS |
2677 | return sc.nr_reclaimed; |
2678 | } | |
2679 | ||
72835c86 | 2680 | unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, |
a7885eb8 | 2681 | gfp_t gfp_mask, |
185efc0f | 2682 | bool noswap) |
66e1707b | 2683 | { |
4e416953 | 2684 | struct zonelist *zonelist; |
bdce6d9e | 2685 | unsigned long nr_reclaimed; |
889976db | 2686 | int nid; |
66e1707b | 2687 | struct scan_control sc = { |
66e1707b | 2688 | .may_writepage = !laptop_mode, |
a6dc60f8 | 2689 | .may_unmap = 1, |
2e2e4259 | 2690 | .may_swap = !noswap, |
22fba335 | 2691 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
66e1707b | 2692 | .order = 0, |
9e3b2f8c | 2693 | .priority = DEF_PRIORITY, |
72835c86 | 2694 | .target_mem_cgroup = memcg, |
327c0e96 | 2695 | .nodemask = NULL, /* we don't care the placement */ |
a09ed5e0 YH |
2696 | .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
2697 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), | |
2698 | }; | |
2699 | struct shrink_control shrink = { | |
2700 | .gfp_mask = sc.gfp_mask, | |
66e1707b | 2701 | }; |
66e1707b | 2702 | |
889976db YH |
2703 | /* |
2704 | * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't | |
2705 | * take care of from where we get pages. So the node where we start the | |
2706 | * scan does not need to be the current node. | |
2707 | */ | |
72835c86 | 2708 | nid = mem_cgroup_select_victim_node(memcg); |
889976db YH |
2709 | |
2710 | zonelist = NODE_DATA(nid)->node_zonelists; | |
bdce6d9e KM |
2711 | |
2712 | trace_mm_vmscan_memcg_reclaim_begin(0, | |
2713 | sc.may_writepage, | |
2714 | sc.gfp_mask); | |
2715 | ||
a09ed5e0 | 2716 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
bdce6d9e KM |
2717 | |
2718 | trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); | |
2719 | ||
2720 | return nr_reclaimed; | |
66e1707b BS |
2721 | } |
2722 | #endif | |
2723 | ||
9e3b2f8c | 2724 | static void age_active_anon(struct zone *zone, struct scan_control *sc) |
f16015fb | 2725 | { |
b95a2f2d | 2726 | struct mem_cgroup *memcg; |
f16015fb | 2727 | |
b95a2f2d JW |
2728 | if (!total_swap_pages) |
2729 | return; | |
2730 | ||
2731 | memcg = mem_cgroup_iter(NULL, NULL, NULL); | |
2732 | do { | |
c56d5c7d | 2733 | struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
b95a2f2d | 2734 | |
c56d5c7d | 2735 | if (inactive_anon_is_low(lruvec)) |
1a93be0e | 2736 | shrink_active_list(SWAP_CLUSTER_MAX, lruvec, |
9e3b2f8c | 2737 | sc, LRU_ACTIVE_ANON); |
b95a2f2d JW |
2738 | |
2739 | memcg = mem_cgroup_iter(NULL, memcg, NULL); | |
2740 | } while (memcg); | |
f16015fb JW |
2741 | } |
2742 | ||
60cefed4 JW |
2743 | static bool zone_balanced(struct zone *zone, int order, |
2744 | unsigned long balance_gap, int classzone_idx) | |
2745 | { | |
2746 | if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) + | |
2747 | balance_gap, classzone_idx, 0)) | |
2748 | return false; | |
2749 | ||
d84da3f9 KS |
2750 | if (IS_ENABLED(CONFIG_COMPACTION) && order && |
2751 | !compaction_suitable(zone, order)) | |
60cefed4 JW |
2752 | return false; |
2753 | ||
2754 | return true; | |
2755 | } | |
2756 | ||
1741c877 | 2757 | /* |
4ae0a48b ZC |
2758 | * pgdat_balanced() is used when checking if a node is balanced. |
2759 | * | |
2760 | * For order-0, all zones must be balanced! | |
2761 | * | |
2762 | * For high-order allocations only zones that meet watermarks and are in a | |
2763 | * zone allowed by the callers classzone_idx are added to balanced_pages. The | |
2764 | * total of balanced pages must be at least 25% of the zones allowed by | |
2765 | * classzone_idx for the node to be considered balanced. Forcing all zones to | |
2766 | * be balanced for high orders can cause excessive reclaim when there are | |
2767 | * imbalanced zones. | |
1741c877 MG |
2768 | * The choice of 25% is due to |
2769 | * o a 16M DMA zone that is balanced will not balance a zone on any | |
2770 | * reasonable sized machine | |
2771 | * o On all other machines, the top zone must be at least a reasonable | |
25985edc | 2772 | * percentage of the middle zones. For example, on 32-bit x86, highmem |
1741c877 MG |
2773 | * would need to be at least 256M for it to be balance a whole node. |
2774 | * Similarly, on x86-64 the Normal zone would need to be at least 1G | |
2775 | * to balance a node on its own. These seemed like reasonable ratios. | |
2776 | */ | |
4ae0a48b | 2777 | static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx) |
1741c877 | 2778 | { |
b40da049 | 2779 | unsigned long managed_pages = 0; |
4ae0a48b | 2780 | unsigned long balanced_pages = 0; |
1741c877 MG |
2781 | int i; |
2782 | ||
4ae0a48b ZC |
2783 | /* Check the watermark levels */ |
2784 | for (i = 0; i <= classzone_idx; i++) { | |
2785 | struct zone *zone = pgdat->node_zones + i; | |
1741c877 | 2786 | |
4ae0a48b ZC |
2787 | if (!populated_zone(zone)) |
2788 | continue; | |
2789 | ||
b40da049 | 2790 | managed_pages += zone->managed_pages; |
4ae0a48b ZC |
2791 | |
2792 | /* | |
2793 | * A special case here: | |
2794 | * | |
2795 | * balance_pgdat() skips over all_unreclaimable after | |
2796 | * DEF_PRIORITY. Effectively, it considers them balanced so | |
2797 | * they must be considered balanced here as well! | |
2798 | */ | |
6e543d57 | 2799 | if (!zone_reclaimable(zone)) { |
b40da049 | 2800 | balanced_pages += zone->managed_pages; |
4ae0a48b ZC |
2801 | continue; |
2802 | } | |
2803 | ||
2804 | if (zone_balanced(zone, order, 0, i)) | |
b40da049 | 2805 | balanced_pages += zone->managed_pages; |
4ae0a48b ZC |
2806 | else if (!order) |
2807 | return false; | |
2808 | } | |
2809 | ||
2810 | if (order) | |
b40da049 | 2811 | return balanced_pages >= (managed_pages >> 2); |
4ae0a48b ZC |
2812 | else |
2813 | return true; | |
1741c877 MG |
2814 | } |
2815 | ||
5515061d MG |
2816 | /* |
2817 | * Prepare kswapd for sleeping. This verifies that there are no processes | |
2818 | * waiting in throttle_direct_reclaim() and that watermarks have been met. | |
2819 | * | |
2820 | * Returns true if kswapd is ready to sleep | |
2821 | */ | |
2822 | static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining, | |
dc83edd9 | 2823 | int classzone_idx) |
f50de2d3 | 2824 | { |
f50de2d3 MG |
2825 | /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ |
2826 | if (remaining) | |
5515061d MG |
2827 | return false; |
2828 | ||
2829 | /* | |
2830 | * There is a potential race between when kswapd checks its watermarks | |
2831 | * and a process gets throttled. There is also a potential race if | |
2832 | * processes get throttled, kswapd wakes, a large process exits therby | |
2833 | * balancing the zones that causes kswapd to miss a wakeup. If kswapd | |
2834 | * is going to sleep, no process should be sleeping on pfmemalloc_wait | |
2835 | * so wake them now if necessary. If necessary, processes will wake | |
2836 | * kswapd and get throttled again | |
2837 | */ | |
2838 | if (waitqueue_active(&pgdat->pfmemalloc_wait)) { | |
2839 | wake_up(&pgdat->pfmemalloc_wait); | |
2840 | return false; | |
2841 | } | |
f50de2d3 | 2842 | |
4ae0a48b | 2843 | return pgdat_balanced(pgdat, order, classzone_idx); |
f50de2d3 MG |
2844 | } |
2845 | ||
75485363 MG |
2846 | /* |
2847 | * kswapd shrinks the zone by the number of pages required to reach | |
2848 | * the high watermark. | |
b8e83b94 MG |
2849 | * |
2850 | * Returns true if kswapd scanned at least the requested number of pages to | |
283aba9f MG |
2851 | * reclaim or if the lack of progress was due to pages under writeback. |
2852 | * This is used to determine if the scanning priority needs to be raised. | |
75485363 | 2853 | */ |
b8e83b94 | 2854 | static bool kswapd_shrink_zone(struct zone *zone, |
7c954f6d | 2855 | int classzone_idx, |
75485363 | 2856 | struct scan_control *sc, |
2ab44f43 MG |
2857 | unsigned long lru_pages, |
2858 | unsigned long *nr_attempted) | |
75485363 | 2859 | { |
7c954f6d MG |
2860 | int testorder = sc->order; |
2861 | unsigned long balance_gap; | |
75485363 MG |
2862 | struct reclaim_state *reclaim_state = current->reclaim_state; |
2863 | struct shrink_control shrink = { | |
2864 | .gfp_mask = sc->gfp_mask, | |
2865 | }; | |
7c954f6d | 2866 | bool lowmem_pressure; |
75485363 MG |
2867 | |
2868 | /* Reclaim above the high watermark. */ | |
2869 | sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone)); | |
7c954f6d MG |
2870 | |
2871 | /* | |
2872 | * Kswapd reclaims only single pages with compaction enabled. Trying | |
2873 | * too hard to reclaim until contiguous free pages have become | |
2874 | * available can hurt performance by evicting too much useful data | |
2875 | * from memory. Do not reclaim more than needed for compaction. | |
2876 | */ | |
2877 | if (IS_ENABLED(CONFIG_COMPACTION) && sc->order && | |
2878 | compaction_suitable(zone, sc->order) != | |
2879 | COMPACT_SKIPPED) | |
2880 | testorder = 0; | |
2881 | ||
2882 | /* | |
2883 | * We put equal pressure on every zone, unless one zone has way too | |
2884 | * many pages free already. The "too many pages" is defined as the | |
2885 | * high wmark plus a "gap" where the gap is either the low | |
2886 | * watermark or 1% of the zone, whichever is smaller. | |
2887 | */ | |
2888 | balance_gap = min(low_wmark_pages(zone), | |
2889 | (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / | |
2890 | KSWAPD_ZONE_BALANCE_GAP_RATIO); | |
2891 | ||
2892 | /* | |
2893 | * If there is no low memory pressure or the zone is balanced then no | |
2894 | * reclaim is necessary | |
2895 | */ | |
2896 | lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone)); | |
2897 | if (!lowmem_pressure && zone_balanced(zone, testorder, | |
2898 | balance_gap, classzone_idx)) | |
2899 | return true; | |
2900 | ||
75485363 | 2901 | shrink_zone(zone, sc); |
0ce3d744 DC |
2902 | nodes_clear(shrink.nodes_to_scan); |
2903 | node_set(zone_to_nid(zone), shrink.nodes_to_scan); | |
75485363 MG |
2904 | |
2905 | reclaim_state->reclaimed_slab = 0; | |
6e543d57 | 2906 | shrink_slab(&shrink, sc->nr_scanned, lru_pages); |
75485363 MG |
2907 | sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
2908 | ||
2ab44f43 MG |
2909 | /* Account for the number of pages attempted to reclaim */ |
2910 | *nr_attempted += sc->nr_to_reclaim; | |
2911 | ||
283aba9f MG |
2912 | zone_clear_flag(zone, ZONE_WRITEBACK); |
2913 | ||
7c954f6d MG |
2914 | /* |
2915 | * If a zone reaches its high watermark, consider it to be no longer | |
2916 | * congested. It's possible there are dirty pages backed by congested | |
2917 | * BDIs but as pressure is relieved, speculatively avoid congestion | |
2918 | * waits. | |
2919 | */ | |
6e543d57 | 2920 | if (zone_reclaimable(zone) && |
7c954f6d MG |
2921 | zone_balanced(zone, testorder, 0, classzone_idx)) { |
2922 | zone_clear_flag(zone, ZONE_CONGESTED); | |
2923 | zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY); | |
2924 | } | |
2925 | ||
b8e83b94 | 2926 | return sc->nr_scanned >= sc->nr_to_reclaim; |
75485363 MG |
2927 | } |
2928 | ||
1da177e4 LT |
2929 | /* |
2930 | * For kswapd, balance_pgdat() will work across all this node's zones until | |
41858966 | 2931 | * they are all at high_wmark_pages(zone). |
1da177e4 | 2932 | * |
0abdee2b | 2933 | * Returns the final order kswapd was reclaiming at |
1da177e4 LT |
2934 | * |
2935 | * There is special handling here for zones which are full of pinned pages. | |
2936 | * This can happen if the pages are all mlocked, or if they are all used by | |
2937 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. | |
2938 | * What we do is to detect the case where all pages in the zone have been | |
2939 | * scanned twice and there has been zero successful reclaim. Mark the zone as | |
2940 | * dead and from now on, only perform a short scan. Basically we're polling | |
2941 | * the zone for when the problem goes away. | |
2942 | * | |
2943 | * kswapd scans the zones in the highmem->normal->dma direction. It skips | |
41858966 MG |
2944 | * zones which have free_pages > high_wmark_pages(zone), but once a zone is |
2945 | * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the | |
2946 | * lower zones regardless of the number of free pages in the lower zones. This | |
2947 | * interoperates with the page allocator fallback scheme to ensure that aging | |
2948 | * of pages is balanced across the zones. | |
1da177e4 | 2949 | */ |
99504748 | 2950 | static unsigned long balance_pgdat(pg_data_t *pgdat, int order, |
dc83edd9 | 2951 | int *classzone_idx) |
1da177e4 | 2952 | { |
1da177e4 | 2953 | int i; |
99504748 | 2954 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ |
179e9639 AM |
2955 | struct scan_control sc = { |
2956 | .gfp_mask = GFP_KERNEL, | |
b8e83b94 | 2957 | .priority = DEF_PRIORITY, |
a6dc60f8 | 2958 | .may_unmap = 1, |
2e2e4259 | 2959 | .may_swap = 1, |
b8e83b94 | 2960 | .may_writepage = !laptop_mode, |
5ad333eb | 2961 | .order = order, |
f16015fb | 2962 | .target_mem_cgroup = NULL, |
179e9639 | 2963 | }; |
f8891e5e | 2964 | count_vm_event(PAGEOUTRUN); |
1da177e4 | 2965 | |
9e3b2f8c | 2966 | do { |
1da177e4 | 2967 | unsigned long lru_pages = 0; |
2ab44f43 | 2968 | unsigned long nr_attempted = 0; |
b8e83b94 | 2969 | bool raise_priority = true; |
2ab44f43 | 2970 | bool pgdat_needs_compaction = (order > 0); |
b8e83b94 MG |
2971 | |
2972 | sc.nr_reclaimed = 0; | |
1da177e4 | 2973 | |
d6277db4 RW |
2974 | /* |
2975 | * Scan in the highmem->dma direction for the highest | |
2976 | * zone which needs scanning | |
2977 | */ | |
2978 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { | |
2979 | struct zone *zone = pgdat->node_zones + i; | |
1da177e4 | 2980 | |
d6277db4 RW |
2981 | if (!populated_zone(zone)) |
2982 | continue; | |
1da177e4 | 2983 | |
6e543d57 LD |
2984 | if (sc.priority != DEF_PRIORITY && |
2985 | !zone_reclaimable(zone)) | |
d6277db4 | 2986 | continue; |
1da177e4 | 2987 | |
556adecb RR |
2988 | /* |
2989 | * Do some background aging of the anon list, to give | |
2990 | * pages a chance to be referenced before reclaiming. | |
2991 | */ | |
9e3b2f8c | 2992 | age_active_anon(zone, &sc); |
556adecb | 2993 | |
cc715d99 MG |
2994 | /* |
2995 | * If the number of buffer_heads in the machine | |
2996 | * exceeds the maximum allowed level and this node | |
2997 | * has a highmem zone, force kswapd to reclaim from | |
2998 | * it to relieve lowmem pressure. | |
2999 | */ | |
3000 | if (buffer_heads_over_limit && is_highmem_idx(i)) { | |
3001 | end_zone = i; | |
3002 | break; | |
3003 | } | |
3004 | ||
60cefed4 | 3005 | if (!zone_balanced(zone, order, 0, 0)) { |
d6277db4 | 3006 | end_zone = i; |
e1dbeda6 | 3007 | break; |
439423f6 | 3008 | } else { |
d43006d5 MG |
3009 | /* |
3010 | * If balanced, clear the dirty and congested | |
3011 | * flags | |
3012 | */ | |
439423f6 | 3013 | zone_clear_flag(zone, ZONE_CONGESTED); |
d43006d5 | 3014 | zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY); |
1da177e4 | 3015 | } |
1da177e4 | 3016 | } |
dafcb73e | 3017 | |
b8e83b94 | 3018 | if (i < 0) |
e1dbeda6 AM |
3019 | goto out; |
3020 | ||
1da177e4 LT |
3021 | for (i = 0; i <= end_zone; i++) { |
3022 | struct zone *zone = pgdat->node_zones + i; | |
3023 | ||
2ab44f43 MG |
3024 | if (!populated_zone(zone)) |
3025 | continue; | |
3026 | ||
adea02a1 | 3027 | lru_pages += zone_reclaimable_pages(zone); |
2ab44f43 MG |
3028 | |
3029 | /* | |
3030 | * If any zone is currently balanced then kswapd will | |
3031 | * not call compaction as it is expected that the | |
3032 | * necessary pages are already available. | |
3033 | */ | |
3034 | if (pgdat_needs_compaction && | |
3035 | zone_watermark_ok(zone, order, | |
3036 | low_wmark_pages(zone), | |
3037 | *classzone_idx, 0)) | |
3038 | pgdat_needs_compaction = false; | |
1da177e4 LT |
3039 | } |
3040 | ||
b7ea3c41 MG |
3041 | /* |
3042 | * If we're getting trouble reclaiming, start doing writepage | |
3043 | * even in laptop mode. | |
3044 | */ | |
3045 | if (sc.priority < DEF_PRIORITY - 2) | |
3046 | sc.may_writepage = 1; | |
3047 | ||
1da177e4 LT |
3048 | /* |
3049 | * Now scan the zone in the dma->highmem direction, stopping | |
3050 | * at the last zone which needs scanning. | |
3051 | * | |
3052 | * We do this because the page allocator works in the opposite | |
3053 | * direction. This prevents the page allocator from allocating | |
3054 | * pages behind kswapd's direction of progress, which would | |
3055 | * cause too much scanning of the lower zones. | |
3056 | */ | |
3057 | for (i = 0; i <= end_zone; i++) { | |
3058 | struct zone *zone = pgdat->node_zones + i; | |
3059 | ||
f3fe6512 | 3060 | if (!populated_zone(zone)) |
1da177e4 LT |
3061 | continue; |
3062 | ||
6e543d57 LD |
3063 | if (sc.priority != DEF_PRIORITY && |
3064 | !zone_reclaimable(zone)) | |
1da177e4 LT |
3065 | continue; |
3066 | ||
1da177e4 | 3067 | sc.nr_scanned = 0; |
4e416953 | 3068 | |
32a4330d | 3069 | /* |
7c954f6d MG |
3070 | * There should be no need to raise the scanning |
3071 | * priority if enough pages are already being scanned | |
3072 | * that that high watermark would be met at 100% | |
3073 | * efficiency. | |
fe2c2a10 | 3074 | */ |
7c954f6d MG |
3075 | if (kswapd_shrink_zone(zone, end_zone, &sc, |
3076 | lru_pages, &nr_attempted)) | |
3077 | raise_priority = false; | |
1da177e4 | 3078 | } |
5515061d MG |
3079 | |
3080 | /* | |
3081 | * If the low watermark is met there is no need for processes | |
3082 | * to be throttled on pfmemalloc_wait as they should not be | |
3083 | * able to safely make forward progress. Wake them | |
3084 | */ | |
3085 | if (waitqueue_active(&pgdat->pfmemalloc_wait) && | |
3086 | pfmemalloc_watermark_ok(pgdat)) | |
3087 | wake_up(&pgdat->pfmemalloc_wait); | |
3088 | ||
1da177e4 | 3089 | /* |
b8e83b94 MG |
3090 | * Fragmentation may mean that the system cannot be rebalanced |
3091 | * for high-order allocations in all zones. If twice the | |
3092 | * allocation size has been reclaimed and the zones are still | |
3093 | * not balanced then recheck the watermarks at order-0 to | |
3094 | * prevent kswapd reclaiming excessively. Assume that a | |
3095 | * process requested a high-order can direct reclaim/compact. | |
1da177e4 | 3096 | */ |
b8e83b94 MG |
3097 | if (order && sc.nr_reclaimed >= 2UL << order) |
3098 | order = sc.order = 0; | |
8357376d | 3099 | |
b8e83b94 MG |
3100 | /* Check if kswapd should be suspending */ |
3101 | if (try_to_freeze() || kthread_should_stop()) | |
3102 | break; | |
8357376d | 3103 | |
2ab44f43 MG |
3104 | /* |
3105 | * Compact if necessary and kswapd is reclaiming at least the | |
3106 | * high watermark number of pages as requsted | |
3107 | */ | |
3108 | if (pgdat_needs_compaction && sc.nr_reclaimed > nr_attempted) | |
3109 | compact_pgdat(pgdat, order); | |
3110 | ||
73ce02e9 | 3111 | /* |
b8e83b94 MG |
3112 | * Raise priority if scanning rate is too low or there was no |
3113 | * progress in reclaiming pages | |
73ce02e9 | 3114 | */ |
b8e83b94 MG |
3115 | if (raise_priority || !sc.nr_reclaimed) |
3116 | sc.priority--; | |
9aa41348 | 3117 | } while (sc.priority >= 1 && |
b8e83b94 | 3118 | !pgdat_balanced(pgdat, order, *classzone_idx)); |
1da177e4 | 3119 | |
b8e83b94 | 3120 | out: |
0abdee2b | 3121 | /* |
5515061d | 3122 | * Return the order we were reclaiming at so prepare_kswapd_sleep() |
0abdee2b MG |
3123 | * makes a decision on the order we were last reclaiming at. However, |
3124 | * if another caller entered the allocator slow path while kswapd | |
3125 | * was awake, order will remain at the higher level | |
3126 | */ | |
dc83edd9 | 3127 | *classzone_idx = end_zone; |
0abdee2b | 3128 | return order; |
1da177e4 LT |
3129 | } |
3130 | ||
dc83edd9 | 3131 | static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) |
f0bc0a60 KM |
3132 | { |
3133 | long remaining = 0; | |
3134 | DEFINE_WAIT(wait); | |
3135 | ||
3136 | if (freezing(current) || kthread_should_stop()) | |
3137 | return; | |
3138 | ||
3139 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); | |
3140 | ||
3141 | /* Try to sleep for a short interval */ | |
5515061d | 3142 | if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) { |
f0bc0a60 KM |
3143 | remaining = schedule_timeout(HZ/10); |
3144 | finish_wait(&pgdat->kswapd_wait, &wait); | |
3145 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); | |
3146 | } | |
3147 | ||
3148 | /* | |
3149 | * After a short sleep, check if it was a premature sleep. If not, then | |
3150 | * go fully to sleep until explicitly woken up. | |
3151 | */ | |
5515061d | 3152 | if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) { |
f0bc0a60 KM |
3153 | trace_mm_vmscan_kswapd_sleep(pgdat->node_id); |
3154 | ||
3155 | /* | |
3156 | * vmstat counters are not perfectly accurate and the estimated | |
3157 | * value for counters such as NR_FREE_PAGES can deviate from the | |
3158 | * true value by nr_online_cpus * threshold. To avoid the zone | |
3159 | * watermarks being breached while under pressure, we reduce the | |
3160 | * per-cpu vmstat threshold while kswapd is awake and restore | |
3161 | * them before going back to sleep. | |
3162 | */ | |
3163 | set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); | |
1c7e7f6c | 3164 | |
62997027 MG |
3165 | /* |
3166 | * Compaction records what page blocks it recently failed to | |
3167 | * isolate pages from and skips them in the future scanning. | |
3168 | * When kswapd is going to sleep, it is reasonable to assume | |
3169 | * that pages and compaction may succeed so reset the cache. | |
3170 | */ | |
3171 | reset_isolation_suitable(pgdat); | |
3172 | ||
1c7e7f6c AK |
3173 | if (!kthread_should_stop()) |
3174 | schedule(); | |
3175 | ||
f0bc0a60 KM |
3176 | set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); |
3177 | } else { | |
3178 | if (remaining) | |
3179 | count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); | |
3180 | else | |
3181 | count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); | |
3182 | } | |
3183 | finish_wait(&pgdat->kswapd_wait, &wait); | |
3184 | } | |
3185 | ||
1da177e4 LT |
3186 | /* |
3187 | * The background pageout daemon, started as a kernel thread | |
4f98a2fe | 3188 | * from the init process. |
1da177e4 LT |
3189 | * |
3190 | * This basically trickles out pages so that we have _some_ | |
3191 | * free memory available even if there is no other activity | |
3192 | * that frees anything up. This is needed for things like routing | |
3193 | * etc, where we otherwise might have all activity going on in | |
3194 | * asynchronous contexts that cannot page things out. | |
3195 | * | |
3196 | * If there are applications that are active memory-allocators | |
3197 | * (most normal use), this basically shouldn't matter. | |
3198 | */ | |
3199 | static int kswapd(void *p) | |
3200 | { | |
215ddd66 | 3201 | unsigned long order, new_order; |
d2ebd0f6 | 3202 | unsigned balanced_order; |
215ddd66 | 3203 | int classzone_idx, new_classzone_idx; |
d2ebd0f6 | 3204 | int balanced_classzone_idx; |
1da177e4 LT |
3205 | pg_data_t *pgdat = (pg_data_t*)p; |
3206 | struct task_struct *tsk = current; | |
f0bc0a60 | 3207 | |
1da177e4 LT |
3208 | struct reclaim_state reclaim_state = { |
3209 | .reclaimed_slab = 0, | |
3210 | }; | |
a70f7302 | 3211 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); |
1da177e4 | 3212 | |
cf40bd16 NP |
3213 | lockdep_set_current_reclaim_state(GFP_KERNEL); |
3214 | ||
174596a0 | 3215 | if (!cpumask_empty(cpumask)) |
c5f59f08 | 3216 | set_cpus_allowed_ptr(tsk, cpumask); |
1da177e4 LT |
3217 | current->reclaim_state = &reclaim_state; |
3218 | ||
3219 | /* | |
3220 | * Tell the memory management that we're a "memory allocator", | |
3221 | * and that if we need more memory we should get access to it | |
3222 | * regardless (see "__alloc_pages()"). "kswapd" should | |
3223 | * never get caught in the normal page freeing logic. | |
3224 | * | |
3225 | * (Kswapd normally doesn't need memory anyway, but sometimes | |
3226 | * you need a small amount of memory in order to be able to | |
3227 | * page out something else, and this flag essentially protects | |
3228 | * us from recursively trying to free more memory as we're | |
3229 | * trying to free the first piece of memory in the first place). | |
3230 | */ | |
930d9152 | 3231 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; |
83144186 | 3232 | set_freezable(); |
1da177e4 | 3233 | |
215ddd66 | 3234 | order = new_order = 0; |
d2ebd0f6 | 3235 | balanced_order = 0; |
215ddd66 | 3236 | classzone_idx = new_classzone_idx = pgdat->nr_zones - 1; |
d2ebd0f6 | 3237 | balanced_classzone_idx = classzone_idx; |
1da177e4 | 3238 | for ( ; ; ) { |
6f6313d4 | 3239 | bool ret; |
3e1d1d28 | 3240 | |
215ddd66 MG |
3241 | /* |
3242 | * If the last balance_pgdat was unsuccessful it's unlikely a | |
3243 | * new request of a similar or harder type will succeed soon | |
3244 | * so consider going to sleep on the basis we reclaimed at | |
3245 | */ | |
d2ebd0f6 AS |
3246 | if (balanced_classzone_idx >= new_classzone_idx && |
3247 | balanced_order == new_order) { | |
215ddd66 MG |
3248 | new_order = pgdat->kswapd_max_order; |
3249 | new_classzone_idx = pgdat->classzone_idx; | |
3250 | pgdat->kswapd_max_order = 0; | |
3251 | pgdat->classzone_idx = pgdat->nr_zones - 1; | |
3252 | } | |
3253 | ||
99504748 | 3254 | if (order < new_order || classzone_idx > new_classzone_idx) { |
1da177e4 LT |
3255 | /* |
3256 | * Don't sleep if someone wants a larger 'order' | |
99504748 | 3257 | * allocation or has tigher zone constraints |
1da177e4 LT |
3258 | */ |
3259 | order = new_order; | |
99504748 | 3260 | classzone_idx = new_classzone_idx; |
1da177e4 | 3261 | } else { |
d2ebd0f6 AS |
3262 | kswapd_try_to_sleep(pgdat, balanced_order, |
3263 | balanced_classzone_idx); | |
1da177e4 | 3264 | order = pgdat->kswapd_max_order; |
99504748 | 3265 | classzone_idx = pgdat->classzone_idx; |
f0dfcde0 AS |
3266 | new_order = order; |
3267 | new_classzone_idx = classzone_idx; | |
4d40502e | 3268 | pgdat->kswapd_max_order = 0; |
215ddd66 | 3269 | pgdat->classzone_idx = pgdat->nr_zones - 1; |
1da177e4 | 3270 | } |
1da177e4 | 3271 | |
8fe23e05 DR |
3272 | ret = try_to_freeze(); |
3273 | if (kthread_should_stop()) | |
3274 | break; | |
3275 | ||
3276 | /* | |
3277 | * We can speed up thawing tasks if we don't call balance_pgdat | |
3278 | * after returning from the refrigerator | |
3279 | */ | |
33906bc5 MG |
3280 | if (!ret) { |
3281 | trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); | |
d2ebd0f6 AS |
3282 | balanced_classzone_idx = classzone_idx; |
3283 | balanced_order = balance_pgdat(pgdat, order, | |
3284 | &balanced_classzone_idx); | |
33906bc5 | 3285 | } |
1da177e4 | 3286 | } |
b0a8cc58 TY |
3287 | |
3288 | current->reclaim_state = NULL; | |
1da177e4 LT |
3289 | return 0; |
3290 | } | |
3291 | ||
3292 | /* | |
3293 | * A zone is low on free memory, so wake its kswapd task to service it. | |
3294 | */ | |
99504748 | 3295 | void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) |
1da177e4 LT |
3296 | { |
3297 | pg_data_t *pgdat; | |
3298 | ||
f3fe6512 | 3299 | if (!populated_zone(zone)) |
1da177e4 LT |
3300 | return; |
3301 | ||
88f5acf8 | 3302 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
1da177e4 | 3303 | return; |
88f5acf8 | 3304 | pgdat = zone->zone_pgdat; |
99504748 | 3305 | if (pgdat->kswapd_max_order < order) { |
1da177e4 | 3306 | pgdat->kswapd_max_order = order; |
99504748 MG |
3307 | pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); |
3308 | } | |
8d0986e2 | 3309 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
1da177e4 | 3310 | return; |
892f795d | 3311 | if (zone_balanced(zone, order, 0, 0)) |
88f5acf8 MG |
3312 | return; |
3313 | ||
3314 | trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); | |
8d0986e2 | 3315 | wake_up_interruptible(&pgdat->kswapd_wait); |
1da177e4 LT |
3316 | } |
3317 | ||
adea02a1 WF |
3318 | /* |
3319 | * The reclaimable count would be mostly accurate. | |
3320 | * The less reclaimable pages may be | |
3321 | * - mlocked pages, which will be moved to unevictable list when encountered | |
3322 | * - mapped pages, which may require several travels to be reclaimed | |
3323 | * - dirty pages, which is not "instantly" reclaimable | |
3324 | */ | |
3325 | unsigned long global_reclaimable_pages(void) | |
4f98a2fe | 3326 | { |
adea02a1 WF |
3327 | int nr; |
3328 | ||
3329 | nr = global_page_state(NR_ACTIVE_FILE) + | |
3330 | global_page_state(NR_INACTIVE_FILE); | |
3331 | ||
ec8acf20 | 3332 | if (get_nr_swap_pages() > 0) |
adea02a1 WF |
3333 | nr += global_page_state(NR_ACTIVE_ANON) + |
3334 | global_page_state(NR_INACTIVE_ANON); | |
3335 | ||
3336 | return nr; | |
3337 | } | |
3338 | ||
c6f37f12 | 3339 | #ifdef CONFIG_HIBERNATION |
1da177e4 | 3340 | /* |
7b51755c | 3341 | * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of |
d6277db4 RW |
3342 | * freed pages. |
3343 | * | |
3344 | * Rather than trying to age LRUs the aim is to preserve the overall | |
3345 | * LRU order by reclaiming preferentially | |
3346 | * inactive > active > active referenced > active mapped | |
1da177e4 | 3347 | */ |
7b51755c | 3348 | unsigned long shrink_all_memory(unsigned long nr_to_reclaim) |
1da177e4 | 3349 | { |
d6277db4 | 3350 | struct reclaim_state reclaim_state; |
d6277db4 | 3351 | struct scan_control sc = { |
7b51755c KM |
3352 | .gfp_mask = GFP_HIGHUSER_MOVABLE, |
3353 | .may_swap = 1, | |
3354 | .may_unmap = 1, | |
d6277db4 | 3355 | .may_writepage = 1, |
7b51755c KM |
3356 | .nr_to_reclaim = nr_to_reclaim, |
3357 | .hibernation_mode = 1, | |
7b51755c | 3358 | .order = 0, |
9e3b2f8c | 3359 | .priority = DEF_PRIORITY, |
1da177e4 | 3360 | }; |
a09ed5e0 YH |
3361 | struct shrink_control shrink = { |
3362 | .gfp_mask = sc.gfp_mask, | |
3363 | }; | |
3364 | struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); | |
7b51755c KM |
3365 | struct task_struct *p = current; |
3366 | unsigned long nr_reclaimed; | |
1da177e4 | 3367 | |
7b51755c KM |
3368 | p->flags |= PF_MEMALLOC; |
3369 | lockdep_set_current_reclaim_state(sc.gfp_mask); | |
3370 | reclaim_state.reclaimed_slab = 0; | |
3371 | p->reclaim_state = &reclaim_state; | |
d6277db4 | 3372 | |
a09ed5e0 | 3373 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
d979677c | 3374 | |
7b51755c KM |
3375 | p->reclaim_state = NULL; |
3376 | lockdep_clear_current_reclaim_state(); | |
3377 | p->flags &= ~PF_MEMALLOC; | |
d6277db4 | 3378 | |
7b51755c | 3379 | return nr_reclaimed; |
1da177e4 | 3380 | } |
c6f37f12 | 3381 | #endif /* CONFIG_HIBERNATION */ |
1da177e4 | 3382 | |
1da177e4 LT |
3383 | /* It's optimal to keep kswapds on the same CPUs as their memory, but |
3384 | not required for correctness. So if the last cpu in a node goes | |
3385 | away, we get changed to run anywhere: as the first one comes back, | |
3386 | restore their cpu bindings. */ | |
fcb35a9b GKH |
3387 | static int cpu_callback(struct notifier_block *nfb, unsigned long action, |
3388 | void *hcpu) | |
1da177e4 | 3389 | { |
58c0a4a7 | 3390 | int nid; |
1da177e4 | 3391 | |
8bb78442 | 3392 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { |
48fb2e24 | 3393 | for_each_node_state(nid, N_MEMORY) { |
c5f59f08 | 3394 | pg_data_t *pgdat = NODE_DATA(nid); |
a70f7302 RR |
3395 | const struct cpumask *mask; |
3396 | ||
3397 | mask = cpumask_of_node(pgdat->node_id); | |
c5f59f08 | 3398 | |
3e597945 | 3399 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
1da177e4 | 3400 | /* One of our CPUs online: restore mask */ |
c5f59f08 | 3401 | set_cpus_allowed_ptr(pgdat->kswapd, mask); |
1da177e4 LT |
3402 | } |
3403 | } | |
3404 | return NOTIFY_OK; | |
3405 | } | |
1da177e4 | 3406 | |
3218ae14 YG |
3407 | /* |
3408 | * This kswapd start function will be called by init and node-hot-add. | |
3409 | * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. | |
3410 | */ | |
3411 | int kswapd_run(int nid) | |
3412 | { | |
3413 | pg_data_t *pgdat = NODE_DATA(nid); | |
3414 | int ret = 0; | |
3415 | ||
3416 | if (pgdat->kswapd) | |
3417 | return 0; | |
3418 | ||
3419 | pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); | |
3420 | if (IS_ERR(pgdat->kswapd)) { | |
3421 | /* failure at boot is fatal */ | |
3422 | BUG_ON(system_state == SYSTEM_BOOTING); | |
d5dc0ad9 GS |
3423 | pr_err("Failed to start kswapd on node %d\n", nid); |
3424 | ret = PTR_ERR(pgdat->kswapd); | |
d72515b8 | 3425 | pgdat->kswapd = NULL; |
3218ae14 YG |
3426 | } |
3427 | return ret; | |
3428 | } | |
3429 | ||
8fe23e05 | 3430 | /* |
d8adde17 JL |
3431 | * Called by memory hotplug when all memory in a node is offlined. Caller must |
3432 | * hold lock_memory_hotplug(). | |
8fe23e05 DR |
3433 | */ |
3434 | void kswapd_stop(int nid) | |
3435 | { | |
3436 | struct task_struct *kswapd = NODE_DATA(nid)->kswapd; | |
3437 | ||
d8adde17 | 3438 | if (kswapd) { |
8fe23e05 | 3439 | kthread_stop(kswapd); |
d8adde17 JL |
3440 | NODE_DATA(nid)->kswapd = NULL; |
3441 | } | |
8fe23e05 DR |
3442 | } |
3443 | ||
1da177e4 LT |
3444 | static int __init kswapd_init(void) |
3445 | { | |
3218ae14 | 3446 | int nid; |
69e05944 | 3447 | |
1da177e4 | 3448 | swap_setup(); |
48fb2e24 | 3449 | for_each_node_state(nid, N_MEMORY) |
3218ae14 | 3450 | kswapd_run(nid); |
1da177e4 LT |
3451 | hotcpu_notifier(cpu_callback, 0); |
3452 | return 0; | |
3453 | } | |
3454 | ||
3455 | module_init(kswapd_init) | |
9eeff239 CL |
3456 | |
3457 | #ifdef CONFIG_NUMA | |
3458 | /* | |
3459 | * Zone reclaim mode | |
3460 | * | |
3461 | * If non-zero call zone_reclaim when the number of free pages falls below | |
3462 | * the watermarks. | |
9eeff239 CL |
3463 | */ |
3464 | int zone_reclaim_mode __read_mostly; | |
3465 | ||
1b2ffb78 | 3466 | #define RECLAIM_OFF 0 |
7d03431c | 3467 | #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ |
1b2ffb78 CL |
3468 | #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ |
3469 | #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ | |
3470 | ||
a92f7126 CL |
3471 | /* |
3472 | * Priority for ZONE_RECLAIM. This determines the fraction of pages | |
3473 | * of a node considered for each zone_reclaim. 4 scans 1/16th of | |
3474 | * a zone. | |
3475 | */ | |
3476 | #define ZONE_RECLAIM_PRIORITY 4 | |
3477 | ||
9614634f CL |
3478 | /* |
3479 | * Percentage of pages in a zone that must be unmapped for zone_reclaim to | |
3480 | * occur. | |
3481 | */ | |
3482 | int sysctl_min_unmapped_ratio = 1; | |
3483 | ||
0ff38490 CL |
3484 | /* |
3485 | * If the number of slab pages in a zone grows beyond this percentage then | |
3486 | * slab reclaim needs to occur. | |
3487 | */ | |
3488 | int sysctl_min_slab_ratio = 5; | |
3489 | ||
90afa5de MG |
3490 | static inline unsigned long zone_unmapped_file_pages(struct zone *zone) |
3491 | { | |
3492 | unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); | |
3493 | unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + | |
3494 | zone_page_state(zone, NR_ACTIVE_FILE); | |
3495 | ||
3496 | /* | |
3497 | * It's possible for there to be more file mapped pages than | |
3498 | * accounted for by the pages on the file LRU lists because | |
3499 | * tmpfs pages accounted for as ANON can also be FILE_MAPPED | |
3500 | */ | |
3501 | return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; | |
3502 | } | |
3503 | ||
3504 | /* Work out how many page cache pages we can reclaim in this reclaim_mode */ | |
3505 | static long zone_pagecache_reclaimable(struct zone *zone) | |
3506 | { | |
3507 | long nr_pagecache_reclaimable; | |
3508 | long delta = 0; | |
3509 | ||
3510 | /* | |
3511 | * If RECLAIM_SWAP is set, then all file pages are considered | |
3512 | * potentially reclaimable. Otherwise, we have to worry about | |
3513 | * pages like swapcache and zone_unmapped_file_pages() provides | |
3514 | * a better estimate | |
3515 | */ | |
3516 | if (zone_reclaim_mode & RECLAIM_SWAP) | |
3517 | nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); | |
3518 | else | |
3519 | nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); | |
3520 | ||
3521 | /* If we can't clean pages, remove dirty pages from consideration */ | |
3522 | if (!(zone_reclaim_mode & RECLAIM_WRITE)) | |
3523 | delta += zone_page_state(zone, NR_FILE_DIRTY); | |
3524 | ||
3525 | /* Watch for any possible underflows due to delta */ | |
3526 | if (unlikely(delta > nr_pagecache_reclaimable)) | |
3527 | delta = nr_pagecache_reclaimable; | |
3528 | ||
3529 | return nr_pagecache_reclaimable - delta; | |
3530 | } | |
3531 | ||
9eeff239 CL |
3532 | /* |
3533 | * Try to free up some pages from this zone through reclaim. | |
3534 | */ | |
179e9639 | 3535 | static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
9eeff239 | 3536 | { |
7fb2d46d | 3537 | /* Minimum pages needed in order to stay on node */ |
69e05944 | 3538 | const unsigned long nr_pages = 1 << order; |
9eeff239 CL |
3539 | struct task_struct *p = current; |
3540 | struct reclaim_state reclaim_state; | |
179e9639 AM |
3541 | struct scan_control sc = { |
3542 | .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), | |
a6dc60f8 | 3543 | .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), |
2e2e4259 | 3544 | .may_swap = 1, |
62b726c1 | 3545 | .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), |
21caf2fc | 3546 | .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)), |
bd2f6199 | 3547 | .order = order, |
9e3b2f8c | 3548 | .priority = ZONE_RECLAIM_PRIORITY, |
179e9639 | 3549 | }; |
a09ed5e0 YH |
3550 | struct shrink_control shrink = { |
3551 | .gfp_mask = sc.gfp_mask, | |
3552 | }; | |
15748048 | 3553 | unsigned long nr_slab_pages0, nr_slab_pages1; |
9eeff239 | 3554 | |
9eeff239 | 3555 | cond_resched(); |
d4f7796e CL |
3556 | /* |
3557 | * We need to be able to allocate from the reserves for RECLAIM_SWAP | |
3558 | * and we also need to be able to write out pages for RECLAIM_WRITE | |
3559 | * and RECLAIM_SWAP. | |
3560 | */ | |
3561 | p->flags |= PF_MEMALLOC | PF_SWAPWRITE; | |
76ca542d | 3562 | lockdep_set_current_reclaim_state(gfp_mask); |
9eeff239 CL |
3563 | reclaim_state.reclaimed_slab = 0; |
3564 | p->reclaim_state = &reclaim_state; | |
c84db23c | 3565 | |
90afa5de | 3566 | if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { |
0ff38490 CL |
3567 | /* |
3568 | * Free memory by calling shrink zone with increasing | |
3569 | * priorities until we have enough memory freed. | |
3570 | */ | |
0ff38490 | 3571 | do { |
9e3b2f8c KK |
3572 | shrink_zone(zone, &sc); |
3573 | } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0); | |
0ff38490 | 3574 | } |
c84db23c | 3575 | |
15748048 KM |
3576 | nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
3577 | if (nr_slab_pages0 > zone->min_slab_pages) { | |
2a16e3f4 | 3578 | /* |
7fb2d46d | 3579 | * shrink_slab() does not currently allow us to determine how |
0ff38490 CL |
3580 | * many pages were freed in this zone. So we take the current |
3581 | * number of slab pages and shake the slab until it is reduced | |
3582 | * by the same nr_pages that we used for reclaiming unmapped | |
3583 | * pages. | |
2a16e3f4 | 3584 | */ |
0ce3d744 DC |
3585 | nodes_clear(shrink.nodes_to_scan); |
3586 | node_set(zone_to_nid(zone), shrink.nodes_to_scan); | |
4dc4b3d9 KM |
3587 | for (;;) { |
3588 | unsigned long lru_pages = zone_reclaimable_pages(zone); | |
3589 | ||
3590 | /* No reclaimable slab or very low memory pressure */ | |
1495f230 | 3591 | if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages)) |
4dc4b3d9 KM |
3592 | break; |
3593 | ||
3594 | /* Freed enough memory */ | |
3595 | nr_slab_pages1 = zone_page_state(zone, | |
3596 | NR_SLAB_RECLAIMABLE); | |
3597 | if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) | |
3598 | break; | |
3599 | } | |
83e33a47 CL |
3600 | |
3601 | /* | |
3602 | * Update nr_reclaimed by the number of slab pages we | |
3603 | * reclaimed from this zone. | |
3604 | */ | |
15748048 KM |
3605 | nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
3606 | if (nr_slab_pages1 < nr_slab_pages0) | |
3607 | sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; | |
2a16e3f4 CL |
3608 | } |
3609 | ||
9eeff239 | 3610 | p->reclaim_state = NULL; |
d4f7796e | 3611 | current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); |
76ca542d | 3612 | lockdep_clear_current_reclaim_state(); |
a79311c1 | 3613 | return sc.nr_reclaimed >= nr_pages; |
9eeff239 | 3614 | } |
179e9639 AM |
3615 | |
3616 | int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) | |
3617 | { | |
179e9639 | 3618 | int node_id; |
d773ed6b | 3619 | int ret; |
179e9639 AM |
3620 | |
3621 | /* | |
0ff38490 CL |
3622 | * Zone reclaim reclaims unmapped file backed pages and |
3623 | * slab pages if we are over the defined limits. | |
34aa1330 | 3624 | * |
9614634f CL |
3625 | * A small portion of unmapped file backed pages is needed for |
3626 | * file I/O otherwise pages read by file I/O will be immediately | |
3627 | * thrown out if the zone is overallocated. So we do not reclaim | |
3628 | * if less than a specified percentage of the zone is used by | |
3629 | * unmapped file backed pages. | |
179e9639 | 3630 | */ |
90afa5de MG |
3631 | if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && |
3632 | zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) | |
fa5e084e | 3633 | return ZONE_RECLAIM_FULL; |
179e9639 | 3634 | |
6e543d57 | 3635 | if (!zone_reclaimable(zone)) |
fa5e084e | 3636 | return ZONE_RECLAIM_FULL; |
d773ed6b | 3637 | |
179e9639 | 3638 | /* |
d773ed6b | 3639 | * Do not scan if the allocation should not be delayed. |
179e9639 | 3640 | */ |
d773ed6b | 3641 | if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) |
fa5e084e | 3642 | return ZONE_RECLAIM_NOSCAN; |
179e9639 AM |
3643 | |
3644 | /* | |
3645 | * Only run zone reclaim on the local zone or on zones that do not | |
3646 | * have associated processors. This will favor the local processor | |
3647 | * over remote processors and spread off node memory allocations | |
3648 | * as wide as possible. | |
3649 | */ | |
89fa3024 | 3650 | node_id = zone_to_nid(zone); |
37c0708d | 3651 | if (node_state(node_id, N_CPU) && node_id != numa_node_id()) |
fa5e084e | 3652 | return ZONE_RECLAIM_NOSCAN; |
d773ed6b DR |
3653 | |
3654 | if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) | |
fa5e084e MG |
3655 | return ZONE_RECLAIM_NOSCAN; |
3656 | ||
d773ed6b DR |
3657 | ret = __zone_reclaim(zone, gfp_mask, order); |
3658 | zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); | |
3659 | ||
24cf7251 MG |
3660 | if (!ret) |
3661 | count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); | |
3662 | ||
d773ed6b | 3663 | return ret; |
179e9639 | 3664 | } |
9eeff239 | 3665 | #endif |
894bc310 | 3666 | |
894bc310 LS |
3667 | /* |
3668 | * page_evictable - test whether a page is evictable | |
3669 | * @page: the page to test | |
894bc310 LS |
3670 | * |
3671 | * Test whether page is evictable--i.e., should be placed on active/inactive | |
39b5f29a | 3672 | * lists vs unevictable list. |
894bc310 LS |
3673 | * |
3674 | * Reasons page might not be evictable: | |
ba9ddf49 | 3675 | * (1) page's mapping marked unevictable |
b291f000 | 3676 | * (2) page is part of an mlocked VMA |
ba9ddf49 | 3677 | * |
894bc310 | 3678 | */ |
39b5f29a | 3679 | int page_evictable(struct page *page) |
894bc310 | 3680 | { |
39b5f29a | 3681 | return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page); |
894bc310 | 3682 | } |
89e004ea | 3683 | |
85046579 | 3684 | #ifdef CONFIG_SHMEM |
89e004ea | 3685 | /** |
24513264 HD |
3686 | * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list |
3687 | * @pages: array of pages to check | |
3688 | * @nr_pages: number of pages to check | |
89e004ea | 3689 | * |
24513264 | 3690 | * Checks pages for evictability and moves them to the appropriate lru list. |
85046579 HD |
3691 | * |
3692 | * This function is only used for SysV IPC SHM_UNLOCK. | |
89e004ea | 3693 | */ |
24513264 | 3694 | void check_move_unevictable_pages(struct page **pages, int nr_pages) |
89e004ea | 3695 | { |
925b7673 | 3696 | struct lruvec *lruvec; |
24513264 HD |
3697 | struct zone *zone = NULL; |
3698 | int pgscanned = 0; | |
3699 | int pgrescued = 0; | |
3700 | int i; | |
89e004ea | 3701 | |
24513264 HD |
3702 | for (i = 0; i < nr_pages; i++) { |
3703 | struct page *page = pages[i]; | |
3704 | struct zone *pagezone; | |
89e004ea | 3705 | |
24513264 HD |
3706 | pgscanned++; |
3707 | pagezone = page_zone(page); | |
3708 | if (pagezone != zone) { | |
3709 | if (zone) | |
3710 | spin_unlock_irq(&zone->lru_lock); | |
3711 | zone = pagezone; | |
3712 | spin_lock_irq(&zone->lru_lock); | |
3713 | } | |
fa9add64 | 3714 | lruvec = mem_cgroup_page_lruvec(page, zone); |
89e004ea | 3715 | |
24513264 HD |
3716 | if (!PageLRU(page) || !PageUnevictable(page)) |
3717 | continue; | |
89e004ea | 3718 | |
39b5f29a | 3719 | if (page_evictable(page)) { |
24513264 HD |
3720 | enum lru_list lru = page_lru_base_type(page); |
3721 | ||
3722 | VM_BUG_ON(PageActive(page)); | |
3723 | ClearPageUnevictable(page); | |
fa9add64 HD |
3724 | del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE); |
3725 | add_page_to_lru_list(page, lruvec, lru); | |
24513264 | 3726 | pgrescued++; |
89e004ea | 3727 | } |
24513264 | 3728 | } |
89e004ea | 3729 | |
24513264 HD |
3730 | if (zone) { |
3731 | __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued); | |
3732 | __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned); | |
3733 | spin_unlock_irq(&zone->lru_lock); | |
89e004ea | 3734 | } |
89e004ea | 3735 | } |
85046579 | 3736 | #endif /* CONFIG_SHMEM */ |
af936a16 | 3737 | |
264e56d8 | 3738 | static void warn_scan_unevictable_pages(void) |
af936a16 | 3739 | { |
264e56d8 | 3740 | printk_once(KERN_WARNING |
25bd91bd | 3741 | "%s: The scan_unevictable_pages sysctl/node-interface has been " |
264e56d8 | 3742 | "disabled for lack of a legitimate use case. If you have " |
25bd91bd KM |
3743 | "one, please send an email to linux-mm@kvack.org.\n", |
3744 | current->comm); | |
af936a16 LS |
3745 | } |
3746 | ||
3747 | /* | |
3748 | * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of | |
3749 | * all nodes' unevictable lists for evictable pages | |
3750 | */ | |
3751 | unsigned long scan_unevictable_pages; | |
3752 | ||
3753 | int scan_unevictable_handler(struct ctl_table *table, int write, | |
8d65af78 | 3754 | void __user *buffer, |
af936a16 LS |
3755 | size_t *length, loff_t *ppos) |
3756 | { | |
264e56d8 | 3757 | warn_scan_unevictable_pages(); |
8d65af78 | 3758 | proc_doulongvec_minmax(table, write, buffer, length, ppos); |
af936a16 LS |
3759 | scan_unevictable_pages = 0; |
3760 | return 0; | |
3761 | } | |
3762 | ||
e4455abb | 3763 | #ifdef CONFIG_NUMA |
af936a16 LS |
3764 | /* |
3765 | * per node 'scan_unevictable_pages' attribute. On demand re-scan of | |
3766 | * a specified node's per zone unevictable lists for evictable pages. | |
3767 | */ | |
3768 | ||
10fbcf4c KS |
3769 | static ssize_t read_scan_unevictable_node(struct device *dev, |
3770 | struct device_attribute *attr, | |
af936a16 LS |
3771 | char *buf) |
3772 | { | |
264e56d8 | 3773 | warn_scan_unevictable_pages(); |
af936a16 LS |
3774 | return sprintf(buf, "0\n"); /* always zero; should fit... */ |
3775 | } | |
3776 | ||
10fbcf4c KS |
3777 | static ssize_t write_scan_unevictable_node(struct device *dev, |
3778 | struct device_attribute *attr, | |
af936a16 LS |
3779 | const char *buf, size_t count) |
3780 | { | |
264e56d8 | 3781 | warn_scan_unevictable_pages(); |
af936a16 LS |
3782 | return 1; |
3783 | } | |
3784 | ||
3785 | ||
10fbcf4c | 3786 | static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, |
af936a16 LS |
3787 | read_scan_unevictable_node, |
3788 | write_scan_unevictable_node); | |
3789 | ||
3790 | int scan_unevictable_register_node(struct node *node) | |
3791 | { | |
10fbcf4c | 3792 | return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages); |
af936a16 LS |
3793 | } |
3794 | ||
3795 | void scan_unevictable_unregister_node(struct node *node) | |
3796 | { | |
10fbcf4c | 3797 | device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages); |
af936a16 | 3798 | } |
e4455abb | 3799 | #endif |