blob: f83a7ed5c6c43ef6fb80d95777affedd9e43b51b [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/mm/vmscan.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 *
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
12 */
13
14#include <linux/mm.h>
15#include <linux/module.h>
16#include <linux/slab.h>
17#include <linux/kernel_stat.h>
18#include <linux/swap.h>
19#include <linux/pagemap.h>
20#include <linux/init.h>
21#include <linux/highmem.h>
Andrew Mortone129b5c2006-09-27 01:50:00 -070022#include <linux/vmstat.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070023#include <linux/file.h>
24#include <linux/writeback.h>
25#include <linux/blkdev.h>
26#include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28#include <linux/mm_inline.h>
29#include <linux/pagevec.h>
30#include <linux/backing-dev.h>
31#include <linux/rmap.h>
32#include <linux/topology.h>
33#include <linux/cpu.h>
34#include <linux/cpuset.h>
35#include <linux/notifier.h>
36#include <linux/rwsem.h>
Rafael J. Wysocki248a0302006-03-22 00:09:04 -080037#include <linux/delay.h>
Yasunori Goto3218ae12006-06-27 02:53:33 -070038#include <linux/kthread.h>
Nigel Cunningham7dfb7102006-12-06 20:34:23 -080039#include <linux/freezer.h>
Balbir Singh66e17072008-02-07 00:13:56 -080040#include <linux/memcontrol.h>
Keika Kobayashi873b4772008-07-25 01:48:52 -070041#include <linux/delayacct.h>
Lee Schermerhornaf936a12008-10-18 20:26:53 -070042#include <linux/sysctl.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070043
44#include <asm/tlbflush.h>
45#include <asm/div64.h>
46
47#include <linux/swapops.h>
48
Nick Piggin0f8053a2006-03-22 00:08:33 -080049#include "internal.h"
50
Linus Torvalds1da177e2005-04-16 15:20:36 -070051struct scan_control {
Linus Torvalds1da177e2005-04-16 15:20:36 -070052 /* Incremented by the number of inactive pages that were scanned */
53 unsigned long nr_scanned;
54
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 /* This context's GFP mask */
Al Viro6daa0e22005-10-21 03:18:50 -040056 gfp_t gfp_mask;
Linus Torvalds1da177e2005-04-16 15:20:36 -070057
58 int may_writepage;
59
Christoph Lameterf1fd1062006-01-18 17:42:30 -080060 /* Can pages be swapped as part of reclaim? */
61 int may_swap;
62
Linus Torvalds1da177e2005-04-16 15:20:36 -070063 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
64 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
65 * In this context, it doesn't matter that we scan the
66 * whole list at once. */
67 int swap_cluster_max;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -070068
69 int swappiness;
Nick Piggin408d8542006-09-25 23:31:27 -070070
71 int all_unreclaimable;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -070072
73 int order;
Balbir Singh66e17072008-02-07 00:13:56 -080074
75 /* Which cgroup do we reclaim from */
76 struct mem_cgroup *mem_cgroup;
77
78 /* Pluggable isolate pages callback */
79 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
80 unsigned long *scanned, int order, int mode,
81 struct zone *z, struct mem_cgroup *mem_cont,
Rik van Riel4f98a2f2008-10-18 20:26:32 -070082 int active, int file);
Linus Torvalds1da177e2005-04-16 15:20:36 -070083};
84
Linus Torvalds1da177e2005-04-16 15:20:36 -070085#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
86
87#ifdef ARCH_HAS_PREFETCH
88#define prefetch_prev_lru_page(_page, _base, _field) \
89 do { \
90 if ((_page)->lru.prev != _base) { \
91 struct page *prev; \
92 \
93 prev = lru_to_page(&(_page->lru)); \
94 prefetch(&prev->_field); \
95 } \
96 } while (0)
97#else
98#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
99#endif
100
101#ifdef ARCH_HAS_PREFETCHW
102#define prefetchw_prev_lru_page(_page, _base, _field) \
103 do { \
104 if ((_page)->lru.prev != _base) { \
105 struct page *prev; \
106 \
107 prev = lru_to_page(&(_page->lru)); \
108 prefetchw(&prev->_field); \
109 } \
110 } while (0)
111#else
112#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
113#endif
114
115/*
116 * From 0 .. 100. Higher means more swappy.
117 */
118int vm_swappiness = 60;
Andrew Mortonbd1e22b2006-06-23 02:03:47 -0700119long vm_total_pages; /* The total number of pages which the VM controls */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120
121static LIST_HEAD(shrinker_list);
122static DECLARE_RWSEM(shrinker_rwsem);
123
Balbir Singh00f0b822008-03-04 14:28:39 -0800124#ifdef CONFIG_CGROUP_MEM_RES_CTLR
KAMEZAWA Hiroyuki91a45472008-02-07 00:14:29 -0800125#define scan_global_lru(sc) (!(sc)->mem_cgroup)
126#else
127#define scan_global_lru(sc) (1)
128#endif
129
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130/*
131 * Add a shrinker callback to be called from the vm
132 */
Rusty Russell8e1f9362007-07-17 04:03:17 -0700133void register_shrinker(struct shrinker *shrinker)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134{
Rusty Russell8e1f9362007-07-17 04:03:17 -0700135 shrinker->nr = 0;
136 down_write(&shrinker_rwsem);
137 list_add_tail(&shrinker->list, &shrinker_list);
138 up_write(&shrinker_rwsem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700139}
Rusty Russell8e1f9362007-07-17 04:03:17 -0700140EXPORT_SYMBOL(register_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141
142/*
143 * Remove one
144 */
Rusty Russell8e1f9362007-07-17 04:03:17 -0700145void unregister_shrinker(struct shrinker *shrinker)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146{
147 down_write(&shrinker_rwsem);
148 list_del(&shrinker->list);
149 up_write(&shrinker_rwsem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150}
Rusty Russell8e1f9362007-07-17 04:03:17 -0700151EXPORT_SYMBOL(unregister_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700152
153#define SHRINK_BATCH 128
154/*
155 * Call the shrink functions to age shrinkable caches
156 *
157 * Here we assume it costs one seek to replace a lru page and that it also
158 * takes a seek to recreate a cache object. With this in mind we age equal
159 * percentages of the lru and ageable caches. This should balance the seeks
160 * generated by these structures.
161 *
Simon Arlott183ff222007-10-20 01:27:18 +0200162 * If the vm encountered mapped pages on the LRU it increase the pressure on
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163 * slab to avoid swapping.
164 *
165 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
166 *
167 * `lru_pages' represents the number of on-LRU pages in all the zones which
168 * are eligible for the caller's allocation attempt. It is used for balancing
169 * slab reclaim versus page reclaim.
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700170 *
171 * Returns the number of slab objects which we shrunk.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 */
Andrew Morton69e05942006-03-22 00:08:19 -0800173unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
174 unsigned long lru_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175{
176 struct shrinker *shrinker;
Andrew Morton69e05942006-03-22 00:08:19 -0800177 unsigned long ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178
179 if (scanned == 0)
180 scanned = SWAP_CLUSTER_MAX;
181
182 if (!down_read_trylock(&shrinker_rwsem))
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700183 return 1; /* Assume we'll be able to shrink next time */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700184
185 list_for_each_entry(shrinker, &shrinker_list, list) {
186 unsigned long long delta;
187 unsigned long total_scan;
Rusty Russell8e1f9362007-07-17 04:03:17 -0700188 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189
190 delta = (4 * scanned) / shrinker->seeks;
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800191 delta *= max_pass;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192 do_div(delta, lru_pages + 1);
193 shrinker->nr += delta;
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800194 if (shrinker->nr < 0) {
195 printk(KERN_ERR "%s: nr=%ld\n",
Harvey Harrisond40cee22008-04-30 00:55:07 -0700196 __func__, shrinker->nr);
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800197 shrinker->nr = max_pass;
198 }
199
200 /*
201 * Avoid risking looping forever due to too large nr value:
202 * never try to free more than twice the estimate number of
203 * freeable entries.
204 */
205 if (shrinker->nr > max_pass * 2)
206 shrinker->nr = max_pass * 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207
208 total_scan = shrinker->nr;
209 shrinker->nr = 0;
210
211 while (total_scan >= SHRINK_BATCH) {
212 long this_scan = SHRINK_BATCH;
213 int shrink_ret;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700214 int nr_before;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700215
Rusty Russell8e1f9362007-07-17 04:03:17 -0700216 nr_before = (*shrinker->shrink)(0, gfp_mask);
217 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218 if (shrink_ret == -1)
219 break;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700220 if (shrink_ret < nr_before)
221 ret += nr_before - shrink_ret;
Christoph Lameterf8891e52006-06-30 01:55:45 -0700222 count_vm_events(SLABS_SCANNED, this_scan);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700223 total_scan -= this_scan;
224
225 cond_resched();
226 }
227
228 shrinker->nr += total_scan;
229 }
230 up_read(&shrinker_rwsem);
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700231 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700232}
233
234/* Called without lock on whether page is mapped, so answer is unstable */
235static inline int page_mapping_inuse(struct page *page)
236{
237 struct address_space *mapping;
238
239 /* Page is in somebody's page tables. */
240 if (page_mapped(page))
241 return 1;
242
243 /* Be more reluctant to reclaim swapcache than pagecache */
244 if (PageSwapCache(page))
245 return 1;
246
247 mapping = page_mapping(page);
248 if (!mapping)
249 return 0;
250
251 /* File is mmap'd by somebody? */
252 return mapping_mapped(mapping);
253}
254
255static inline int is_page_cache_freeable(struct page *page)
256{
257 return page_count(page) - !!PagePrivate(page) == 2;
258}
259
260static int may_write_to_queue(struct backing_dev_info *bdi)
261{
Christoph Lameter930d9152006-01-08 01:00:47 -0800262 if (current->flags & PF_SWAPWRITE)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263 return 1;
264 if (!bdi_write_congested(bdi))
265 return 1;
266 if (bdi == current->backing_dev_info)
267 return 1;
268 return 0;
269}
270
271/*
272 * We detected a synchronous write error writing a page out. Probably
273 * -ENOSPC. We need to propagate that into the address_space for a subsequent
274 * fsync(), msync() or close().
275 *
276 * The tricky part is that after writepage we cannot touch the mapping: nothing
277 * prevents it from being freed up. But we have a ref on the page and once
278 * that page is locked, the mapping is pinned.
279 *
280 * We're allowed to run sleeping lock_page() here because we know the caller has
281 * __GFP_FS.
282 */
283static void handle_write_error(struct address_space *mapping,
284 struct page *page, int error)
285{
286 lock_page(page);
Guillaume Chazarain3e9f45b2007-05-08 00:23:25 -0700287 if (page_mapping(page) == mapping)
288 mapping_set_error(mapping, error);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700289 unlock_page(page);
290}
291
Andy Whitcroftc661b072007-08-22 14:01:26 -0700292/* Request for sync pageout. */
293enum pageout_io {
294 PAGEOUT_IO_ASYNC,
295 PAGEOUT_IO_SYNC,
296};
297
Christoph Lameter04e62a22006-06-23 02:03:38 -0700298/* possible outcome of pageout() */
299typedef enum {
300 /* failed to write page out, page is locked */
301 PAGE_KEEP,
302 /* move page to the active list, page is locked */
303 PAGE_ACTIVATE,
304 /* page has been sent to the disk successfully, page is unlocked */
305 PAGE_SUCCESS,
306 /* page is clean and locked */
307 PAGE_CLEAN,
308} pageout_t;
309
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310/*
Andrew Morton1742f192006-03-22 00:08:21 -0800311 * pageout is called by shrink_page_list() for each dirty page.
312 * Calls ->writepage().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700313 */
Andy Whitcroftc661b072007-08-22 14:01:26 -0700314static pageout_t pageout(struct page *page, struct address_space *mapping,
315 enum pageout_io sync_writeback)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316{
317 /*
318 * If the page is dirty, only perform writeback if that write
319 * will be non-blocking. To prevent this allocation from being
320 * stalled by pagecache activity. But note that there may be
321 * stalls if we need to run get_block(). We could test
322 * PagePrivate for that.
323 *
324 * If this process is currently in generic_file_write() against
325 * this page's queue, we can perform writeback even if that
326 * will block.
327 *
328 * If the page is swapcache, write it back even if that would
329 * block, for some throttling. This happens by accident, because
330 * swap_backing_dev_info is bust: it doesn't reflect the
331 * congestion state of the swapdevs. Easy to fix, if needed.
332 * See swapfile.c:page_queue_congested().
333 */
334 if (!is_page_cache_freeable(page))
335 return PAGE_KEEP;
336 if (!mapping) {
337 /*
338 * Some data journaling orphaned pages can have
339 * page->mapping == NULL while being dirty with clean buffers.
340 */
akpm@osdl.org323aca62005-04-16 15:24:06 -0700341 if (PagePrivate(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342 if (try_to_free_buffers(page)) {
343 ClearPageDirty(page);
Harvey Harrisond40cee22008-04-30 00:55:07 -0700344 printk("%s: orphaned page\n", __func__);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700345 return PAGE_CLEAN;
346 }
347 }
348 return PAGE_KEEP;
349 }
350 if (mapping->a_ops->writepage == NULL)
351 return PAGE_ACTIVATE;
352 if (!may_write_to_queue(mapping->backing_dev_info))
353 return PAGE_KEEP;
354
355 if (clear_page_dirty_for_io(page)) {
356 int res;
357 struct writeback_control wbc = {
358 .sync_mode = WB_SYNC_NONE,
359 .nr_to_write = SWAP_CLUSTER_MAX,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700360 .range_start = 0,
361 .range_end = LLONG_MAX,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362 .nonblocking = 1,
363 .for_reclaim = 1,
364 };
365
366 SetPageReclaim(page);
367 res = mapping->a_ops->writepage(page, &wbc);
368 if (res < 0)
369 handle_write_error(mapping, page, res);
Zach Brown994fc28c2005-12-15 14:28:17 -0800370 if (res == AOP_WRITEPAGE_ACTIVATE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700371 ClearPageReclaim(page);
372 return PAGE_ACTIVATE;
373 }
Andy Whitcroftc661b072007-08-22 14:01:26 -0700374
375 /*
376 * Wait on writeback if requested to. This happens when
377 * direct reclaiming a large contiguous area and the
378 * first attempt to free a range of pages fails.
379 */
380 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
381 wait_on_page_writeback(page);
382
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383 if (!PageWriteback(page)) {
384 /* synchronous write or broken a_ops? */
385 ClearPageReclaim(page);
386 }
Andrew Mortone129b5c2006-09-27 01:50:00 -0700387 inc_zone_page_state(page, NR_VMSCAN_WRITE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700388 return PAGE_SUCCESS;
389 }
390
391 return PAGE_CLEAN;
392}
393
Andrew Mortona649fd92006-10-17 00:09:36 -0700394/*
Nick Piggine2867812008-07-25 19:45:30 -0700395 * Same as remove_mapping, but if the page is removed from the mapping, it
396 * gets returned with a refcount of 0.
Andrew Mortona649fd92006-10-17 00:09:36 -0700397 */
Nick Piggine2867812008-07-25 19:45:30 -0700398static int __remove_mapping(struct address_space *mapping, struct page *page)
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800399{
Nick Piggin28e4d962006-09-25 23:31:23 -0700400 BUG_ON(!PageLocked(page));
401 BUG_ON(mapping != page_mapping(page));
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800402
Nick Piggin19fd6232008-07-25 19:45:32 -0700403 spin_lock_irq(&mapping->tree_lock);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800404 /*
Nick Piggin0fd0e6b2006-09-27 01:50:02 -0700405 * The non racy check for a busy page.
406 *
407 * Must be careful with the order of the tests. When someone has
408 * a ref to the page, it may be possible that they dirty it then
409 * drop the reference. So if PageDirty is tested before page_count
410 * here, then the following race may occur:
411 *
412 * get_user_pages(&page);
413 * [user mapping goes away]
414 * write_to(page);
415 * !PageDirty(page) [good]
416 * SetPageDirty(page);
417 * put_page(page);
418 * !page_count(page) [good, discard it]
419 *
420 * [oops, our write_to data is lost]
421 *
422 * Reversing the order of the tests ensures such a situation cannot
423 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
424 * load is not satisfied before that of page->_count.
425 *
426 * Note that if SetPageDirty is always performed via set_page_dirty,
427 * and thus under tree_lock, then this ordering is not required.
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800428 */
Nick Piggine2867812008-07-25 19:45:30 -0700429 if (!page_freeze_refs(page, 2))
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800430 goto cannot_free;
Nick Piggine2867812008-07-25 19:45:30 -0700431 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
432 if (unlikely(PageDirty(page))) {
433 page_unfreeze_refs(page, 2);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800434 goto cannot_free;
Nick Piggine2867812008-07-25 19:45:30 -0700435 }
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800436
437 if (PageSwapCache(page)) {
438 swp_entry_t swap = { .val = page_private(page) };
439 __delete_from_swap_cache(page);
Nick Piggin19fd6232008-07-25 19:45:32 -0700440 spin_unlock_irq(&mapping->tree_lock);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800441 swap_free(swap);
Nick Piggine2867812008-07-25 19:45:30 -0700442 } else {
443 __remove_from_page_cache(page);
Nick Piggin19fd6232008-07-25 19:45:32 -0700444 spin_unlock_irq(&mapping->tree_lock);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800445 }
446
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800447 return 1;
448
449cannot_free:
Nick Piggin19fd6232008-07-25 19:45:32 -0700450 spin_unlock_irq(&mapping->tree_lock);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800451 return 0;
452}
453
Linus Torvalds1da177e2005-04-16 15:20:36 -0700454/*
Nick Piggine2867812008-07-25 19:45:30 -0700455 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
456 * someone else has a ref on the page, abort and return 0. If it was
457 * successfully detached, return 1. Assumes the caller has a single ref on
458 * this page.
459 */
460int remove_mapping(struct address_space *mapping, struct page *page)
461{
462 if (__remove_mapping(mapping, page)) {
463 /*
464 * Unfreezing the refcount with 1 rather than 2 effectively
465 * drops the pagecache ref for us without requiring another
466 * atomic operation.
467 */
468 page_unfreeze_refs(page, 1);
469 return 1;
470 }
471 return 0;
472}
473
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700474/**
475 * putback_lru_page - put previously isolated page onto appropriate LRU list
476 * @page: page to be put back to appropriate lru list
477 *
478 * Add previously isolated @page to appropriate LRU list.
479 * Page may still be unevictable for other reasons.
480 *
481 * lru_lock must not be held, interrupts must be enabled.
482 */
483#ifdef CONFIG_UNEVICTABLE_LRU
484void putback_lru_page(struct page *page)
485{
486 int lru;
487 int active = !!TestClearPageActive(page);
Lee Schermerhornbbfd28e2008-10-18 20:26:40 -0700488 int was_unevictable = PageUnevictable(page);
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700489
490 VM_BUG_ON(PageLRU(page));
491
492redo:
493 ClearPageUnevictable(page);
494
495 if (page_evictable(page, NULL)) {
496 /*
497 * For evictable pages, we can use the cache.
498 * In event of a race, worst case is we end up with an
499 * unevictable page on [in]active list.
500 * We know how to handle that.
501 */
502 lru = active + page_is_file_cache(page);
503 lru_cache_add_lru(page, lru);
504 } else {
505 /*
506 * Put unevictable pages directly on zone's unevictable
507 * list.
508 */
509 lru = LRU_UNEVICTABLE;
510 add_page_to_unevictable_list(page);
511 }
512 mem_cgroup_move_lists(page, lru);
513
514 /*
515 * page's status can change while we move it among lru. If an evictable
516 * page is on unevictable list, it never be freed. To avoid that,
517 * check after we added it to the list, again.
518 */
519 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
520 if (!isolate_lru_page(page)) {
521 put_page(page);
522 goto redo;
523 }
524 /* This means someone else dropped this page from LRU
525 * So, it will be freed or putback to LRU again. There is
526 * nothing to do here.
527 */
528 }
529
Lee Schermerhornbbfd28e2008-10-18 20:26:40 -0700530 if (was_unevictable && lru != LRU_UNEVICTABLE)
531 count_vm_event(UNEVICTABLE_PGRESCUED);
532 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
533 count_vm_event(UNEVICTABLE_PGCULLED);
534
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700535 put_page(page); /* drop ref from isolate */
536}
537
538#else /* CONFIG_UNEVICTABLE_LRU */
539
540void putback_lru_page(struct page *page)
541{
542 int lru;
543 VM_BUG_ON(PageLRU(page));
544
545 lru = !!TestClearPageActive(page) + page_is_file_cache(page);
546 lru_cache_add_lru(page, lru);
547 mem_cgroup_move_lists(page, lru);
548 put_page(page);
549}
550#endif /* CONFIG_UNEVICTABLE_LRU */
551
552
Nick Piggine2867812008-07-25 19:45:30 -0700553/*
Andrew Morton1742f192006-03-22 00:08:21 -0800554 * shrink_page_list() returns the number of reclaimed pages
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555 */
Andrew Morton1742f192006-03-22 00:08:21 -0800556static unsigned long shrink_page_list(struct list_head *page_list,
Andy Whitcroftc661b072007-08-22 14:01:26 -0700557 struct scan_control *sc,
558 enum pageout_io sync_writeback)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700559{
560 LIST_HEAD(ret_pages);
561 struct pagevec freed_pvec;
562 int pgactivate = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -0800563 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700564
565 cond_resched();
566
567 pagevec_init(&freed_pvec, 1);
568 while (!list_empty(page_list)) {
569 struct address_space *mapping;
570 struct page *page;
571 int may_enter_fs;
572 int referenced;
573
574 cond_resched();
575
576 page = lru_to_page(page_list);
577 list_del(&page->lru);
578
Nick Piggin529ae9a2008-08-02 12:01:03 +0200579 if (!trylock_page(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580 goto keep;
581
Nick Piggin725d7042006-09-25 23:30:55 -0700582 VM_BUG_ON(PageActive(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700583
584 sc->nr_scanned++;
Christoph Lameter80e43422006-02-11 17:55:53 -0800585
Nick Pigginb291f002008-10-18 20:26:44 -0700586 if (unlikely(!page_evictable(page, NULL)))
587 goto cull_mlocked;
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700588
Christoph Lameter80e43422006-02-11 17:55:53 -0800589 if (!sc->may_swap && page_mapped(page))
590 goto keep_locked;
591
Linus Torvalds1da177e2005-04-16 15:20:36 -0700592 /* Double the slab pressure for mapped and swapcache pages */
593 if (page_mapped(page) || PageSwapCache(page))
594 sc->nr_scanned++;
595
Andy Whitcroftc661b072007-08-22 14:01:26 -0700596 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
597 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
598
599 if (PageWriteback(page)) {
600 /*
601 * Synchronous reclaim is performed in two passes,
602 * first an asynchronous pass over the list to
603 * start parallel writeback, and a second synchronous
604 * pass to wait for the IO to complete. Wait here
605 * for any page for which writeback has already
606 * started.
607 */
608 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
609 wait_on_page_writeback(page);
Andrew Morton4dd4b922008-03-24 12:29:52 -0700610 else
Andy Whitcroftc661b072007-08-22 14:01:26 -0700611 goto keep_locked;
612 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700613
Balbir Singhbed71612008-02-07 00:14:01 -0800614 referenced = page_referenced(page, 1, sc->mem_cgroup);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700615 /* In active use or really unfreeable? Activate it. */
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700616 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
617 referenced && page_mapping_inuse(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700618 goto activate_locked;
619
620#ifdef CONFIG_SWAP
621 /*
622 * Anonymous process memory has backing store?
623 * Try to allocate it some swap space here.
624 */
Nick Pigginb291f002008-10-18 20:26:44 -0700625 if (PageAnon(page) && !PageSwapCache(page)) {
Hugh Dickins63eb6b92008-11-19 15:36:37 -0800626 if (!(sc->gfp_mask & __GFP_IO))
627 goto keep_locked;
Nick Pigginb291f002008-10-18 20:26:44 -0700628 switch (try_to_munlock(page)) {
629 case SWAP_FAIL: /* shouldn't happen */
630 case SWAP_AGAIN:
631 goto keep_locked;
632 case SWAP_MLOCK:
633 goto cull_mlocked;
634 case SWAP_SUCCESS:
635 ; /* fall thru'; add to swap cache */
636 }
Christoph Lameter1480a542006-01-08 01:00:53 -0800637 if (!add_to_swap(page, GFP_ATOMIC))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700638 goto activate_locked;
Hugh Dickins63eb6b92008-11-19 15:36:37 -0800639 may_enter_fs = 1;
Nick Pigginb291f002008-10-18 20:26:44 -0700640 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700641#endif /* CONFIG_SWAP */
642
643 mapping = page_mapping(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700644
645 /*
646 * The page is mapped into the page tables of one or more
647 * processes. Try to unmap it here.
648 */
649 if (page_mapped(page) && mapping) {
Christoph Lametera48d07a2006-02-01 03:05:38 -0800650 switch (try_to_unmap(page, 0)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651 case SWAP_FAIL:
652 goto activate_locked;
653 case SWAP_AGAIN:
654 goto keep_locked;
Nick Pigginb291f002008-10-18 20:26:44 -0700655 case SWAP_MLOCK:
656 goto cull_mlocked;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700657 case SWAP_SUCCESS:
658 ; /* try to free the page below */
659 }
660 }
661
662 if (PageDirty(page)) {
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700663 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700664 goto keep_locked;
Andrew Morton4dd4b922008-03-24 12:29:52 -0700665 if (!may_enter_fs)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700666 goto keep_locked;
Christoph Lameter52a83632006-02-01 03:05:28 -0800667 if (!sc->may_writepage)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700668 goto keep_locked;
669
670 /* Page is dirty, try to write it out here */
Andy Whitcroftc661b072007-08-22 14:01:26 -0700671 switch (pageout(page, mapping, sync_writeback)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700672 case PAGE_KEEP:
673 goto keep_locked;
674 case PAGE_ACTIVATE:
675 goto activate_locked;
676 case PAGE_SUCCESS:
Andrew Morton4dd4b922008-03-24 12:29:52 -0700677 if (PageWriteback(page) || PageDirty(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700678 goto keep;
679 /*
680 * A synchronous write - probably a ramdisk. Go
681 * ahead and try to reclaim the page.
682 */
Nick Piggin529ae9a2008-08-02 12:01:03 +0200683 if (!trylock_page(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700684 goto keep;
685 if (PageDirty(page) || PageWriteback(page))
686 goto keep_locked;
687 mapping = page_mapping(page);
688 case PAGE_CLEAN:
689 ; /* try to free the page below */
690 }
691 }
692
693 /*
694 * If the page has buffers, try to free the buffer mappings
695 * associated with this page. If we succeed we try to free
696 * the page as well.
697 *
698 * We do this even if the page is PageDirty().
699 * try_to_release_page() does not perform I/O, but it is
700 * possible for a page to have PageDirty set, but it is actually
701 * clean (all its buffers are clean). This happens if the
702 * buffers were written out directly, with submit_bh(). ext3
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700703 * will do this, as well as the blockdev mapping.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700704 * try_to_release_page() will discover that cleanness and will
705 * drop the buffers and mark the page clean - it can be freed.
706 *
707 * Rarely, pages can have buffers and no ->mapping. These are
708 * the pages which were not successfully invalidated in
709 * truncate_complete_page(). We try to drop those buffers here
710 * and if that worked, and the page is no longer mapped into
711 * process address space (page_count == 1) it can be freed.
712 * Otherwise, leave the page on the LRU so it is swappable.
713 */
714 if (PagePrivate(page)) {
715 if (!try_to_release_page(page, sc->gfp_mask))
716 goto activate_locked;
Nick Piggine2867812008-07-25 19:45:30 -0700717 if (!mapping && page_count(page) == 1) {
718 unlock_page(page);
719 if (put_page_testzero(page))
720 goto free_it;
721 else {
722 /*
723 * rare race with speculative reference.
724 * the speculative reference will free
725 * this page shortly, so we may
726 * increment nr_reclaimed here (and
727 * leave it off the LRU).
728 */
729 nr_reclaimed++;
730 continue;
731 }
732 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700733 }
734
Nick Piggine2867812008-07-25 19:45:30 -0700735 if (!mapping || !__remove_mapping(mapping, page))
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800736 goto keep_locked;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737
Nick Piggina978d6f2008-10-18 20:26:58 -0700738 /*
739 * At this point, we have no other references and there is
740 * no way to pick any more up (removed from LRU, removed
741 * from pagecache). Can use non-atomic bitops now (and
742 * we obviously don't have to worry about waking up a process
743 * waiting on the page lock, because there are no references.
744 */
745 __clear_page_locked(page);
Nick Piggine2867812008-07-25 19:45:30 -0700746free_it:
Andrew Morton05ff5132006-03-22 00:08:20 -0800747 nr_reclaimed++;
Nick Piggine2867812008-07-25 19:45:30 -0700748 if (!pagevec_add(&freed_pvec, page)) {
749 __pagevec_free(&freed_pvec);
750 pagevec_reinit(&freed_pvec);
751 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700752 continue;
753
Nick Pigginb291f002008-10-18 20:26:44 -0700754cull_mlocked:
755 unlock_page(page);
756 putback_lru_page(page);
757 continue;
758
Linus Torvalds1da177e2005-04-16 15:20:36 -0700759activate_locked:
Rik van Riel68a223942008-10-18 20:26:23 -0700760 /* Not a candidate for swapping, so reclaim swap space. */
761 if (PageSwapCache(page) && vm_swap_full())
762 remove_exclusive_swap_page_ref(page);
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700763 VM_BUG_ON(PageActive(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700764 SetPageActive(page);
765 pgactivate++;
766keep_locked:
767 unlock_page(page);
768keep:
769 list_add(&page->lru, &ret_pages);
Nick Pigginb291f002008-10-18 20:26:44 -0700770 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700771 }
772 list_splice(&ret_pages, page_list);
773 if (pagevec_count(&freed_pvec))
Nick Piggine2867812008-07-25 19:45:30 -0700774 __pagevec_free(&freed_pvec);
Christoph Lameterf8891e52006-06-30 01:55:45 -0700775 count_vm_events(PGACTIVATE, pgactivate);
Andrew Morton05ff5132006-03-22 00:08:20 -0800776 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700777}
778
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700779/* LRU Isolation modes. */
780#define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
781#define ISOLATE_ACTIVE 1 /* Isolate active pages. */
782#define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
783
784/*
785 * Attempt to remove the specified page from its LRU. Only take this page
786 * if it is of the appropriate PageActive status. Pages which are being
787 * freed elsewhere are also ignored.
788 *
789 * page: page to consider
790 * mode: one of the LRU isolation modes defined above
791 *
792 * returns 0 on success, -ve errno on failure.
793 */
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700794int __isolate_lru_page(struct page *page, int mode, int file)
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700795{
796 int ret = -EINVAL;
797
798 /* Only take pages on the LRU. */
799 if (!PageLRU(page))
800 return ret;
801
802 /*
803 * When checking the active state, we need to be sure we are
804 * dealing with comparible boolean values. Take the logical not
805 * of each.
806 */
807 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
808 return ret;
809
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700810 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
811 return ret;
812
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700813 /*
814 * When this function is being called for lumpy reclaim, we
815 * initially look into all LRU pages, active, inactive and
816 * unevictable; only give shrink_page_list evictable pages.
817 */
818 if (PageUnevictable(page))
819 return ret;
820
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700821 ret = -EBUSY;
822 if (likely(get_page_unless_zero(page))) {
823 /*
824 * Be careful not to clear PageLRU until after we're
825 * sure the page is not being freed elsewhere -- the
826 * page release code relies on it.
827 */
828 ClearPageLRU(page);
829 ret = 0;
830 }
831
832 return ret;
833}
834
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800835/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700836 * zone->lru_lock is heavily contended. Some of the functions that
837 * shrink the lists perform better by taking out a batch of pages
838 * and working on them outside the LRU lock.
839 *
840 * For pagecache intensive workloads, this function is the hottest
841 * spot in the kernel (apart from copy_*_user functions).
842 *
843 * Appropriate locks must be held before calling this function.
844 *
845 * @nr_to_scan: The number of pages to look through on the list.
846 * @src: The LRU list to pull pages off.
847 * @dst: The temp list to put pages on to.
848 * @scanned: The number of pages that were scanned.
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700849 * @order: The caller's attempted allocation order
850 * @mode: One of the LRU isolation modes
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700851 * @file: True [1] if isolating file [!anon] pages
Linus Torvalds1da177e2005-04-16 15:20:36 -0700852 *
853 * returns how many pages were moved onto *@dst.
854 */
Andrew Morton69e05942006-03-22 00:08:19 -0800855static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
856 struct list_head *src, struct list_head *dst,
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700857 unsigned long *scanned, int order, int mode, int file)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700858{
Andrew Morton69e05942006-03-22 00:08:19 -0800859 unsigned long nr_taken = 0;
Wu Fengguangc9b02d92006-03-22 00:08:23 -0800860 unsigned long scan;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700861
Wu Fengguangc9b02d92006-03-22 00:08:23 -0800862 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700863 struct page *page;
864 unsigned long pfn;
865 unsigned long end_pfn;
866 unsigned long page_pfn;
867 int zone_id;
868
Linus Torvalds1da177e2005-04-16 15:20:36 -0700869 page = lru_to_page(src);
870 prefetchw_prev_lru_page(page, src, flags);
871
Nick Piggin725d7042006-09-25 23:30:55 -0700872 VM_BUG_ON(!PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800873
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700874 switch (__isolate_lru_page(page, mode, file)) {
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700875 case 0:
876 list_move(&page->lru, dst);
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800877 nr_taken++;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700878 break;
Nick Piggin46453a62006-03-22 00:07:58 -0800879
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700880 case -EBUSY:
881 /* else it is being freed elsewhere */
882 list_move(&page->lru, src);
883 continue;
884
885 default:
886 BUG();
887 }
888
889 if (!order)
890 continue;
891
892 /*
893 * Attempt to take all pages in the order aligned region
894 * surrounding the tag page. Only take those pages of
895 * the same active state as that tag page. We may safely
896 * round the target page pfn down to the requested order
897 * as the mem_map is guarenteed valid out to MAX_ORDER,
898 * where that page is in a different zone we will detect
899 * it from its zone id and abort this block scan.
900 */
901 zone_id = page_zone_id(page);
902 page_pfn = page_to_pfn(page);
903 pfn = page_pfn & ~((1 << order) - 1);
904 end_pfn = pfn + (1 << order);
905 for (; pfn < end_pfn; pfn++) {
906 struct page *cursor_page;
907
908 /* The target page is in the block, ignore it. */
909 if (unlikely(pfn == page_pfn))
910 continue;
911
912 /* Avoid holes within the zone. */
913 if (unlikely(!pfn_valid_within(pfn)))
914 break;
915
916 cursor_page = pfn_to_page(pfn);
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700917
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700918 /* Check that we have not crossed a zone boundary. */
919 if (unlikely(page_zone_id(cursor_page) != zone_id))
920 continue;
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700921 switch (__isolate_lru_page(cursor_page, mode, file)) {
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700922 case 0:
923 list_move(&cursor_page->lru, dst);
924 nr_taken++;
925 scan++;
926 break;
927
928 case -EBUSY:
929 /* else it is being freed elsewhere */
930 list_move(&cursor_page->lru, src);
931 default:
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700932 break; /* ! on LRU or wrong list */
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700933 }
934 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700935 }
936
937 *scanned = scan;
938 return nr_taken;
939}
940
Balbir Singh66e17072008-02-07 00:13:56 -0800941static unsigned long isolate_pages_global(unsigned long nr,
942 struct list_head *dst,
943 unsigned long *scanned, int order,
944 int mode, struct zone *z,
945 struct mem_cgroup *mem_cont,
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700946 int active, int file)
Balbir Singh66e17072008-02-07 00:13:56 -0800947{
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700948 int lru = LRU_BASE;
Balbir Singh66e17072008-02-07 00:13:56 -0800949 if (active)
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700950 lru += LRU_ACTIVE;
951 if (file)
952 lru += LRU_FILE;
953 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
954 mode, !!file);
Balbir Singh66e17072008-02-07 00:13:56 -0800955}
956
Linus Torvalds1da177e2005-04-16 15:20:36 -0700957/*
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700958 * clear_active_flags() is a helper for shrink_active_list(), clearing
959 * any active bits from the pages in the list.
960 */
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700961static unsigned long clear_active_flags(struct list_head *page_list,
962 unsigned int *count)
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700963{
964 int nr_active = 0;
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700965 int lru;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700966 struct page *page;
967
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700968 list_for_each_entry(page, page_list, lru) {
969 lru = page_is_file_cache(page);
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700970 if (PageActive(page)) {
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700971 lru += LRU_ACTIVE;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700972 ClearPageActive(page);
973 nr_active++;
974 }
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700975 count[lru]++;
976 }
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700977
978 return nr_active;
979}
980
Nick Piggin62695a82008-10-18 20:26:09 -0700981/**
982 * isolate_lru_page - tries to isolate a page from its LRU list
983 * @page: page to isolate from its LRU list
984 *
985 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
986 * vmstat statistic corresponding to whatever LRU list the page was on.
987 *
988 * Returns 0 if the page was removed from an LRU list.
989 * Returns -EBUSY if the page was not on an LRU list.
990 *
991 * The returned page will have PageLRU() cleared. If it was found on
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700992 * the active list, it will have PageActive set. If it was found on
993 * the unevictable list, it will have the PageUnevictable bit set. That flag
994 * may need to be cleared by the caller before letting the page go.
Nick Piggin62695a82008-10-18 20:26:09 -0700995 *
996 * The vmstat statistic corresponding to the list on which the page was
997 * found will be decremented.
998 *
999 * Restrictions:
1000 * (1) Must be called with an elevated refcount on the page. This is a
1001 * fundamentnal difference from isolate_lru_pages (which is called
1002 * without a stable reference).
1003 * (2) the lru_lock must not be held.
1004 * (3) interrupts must be enabled.
1005 */
1006int isolate_lru_page(struct page *page)
1007{
1008 int ret = -EBUSY;
1009
1010 if (PageLRU(page)) {
1011 struct zone *zone = page_zone(page);
1012
1013 spin_lock_irq(&zone->lru_lock);
1014 if (PageLRU(page) && get_page_unless_zero(page)) {
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001015 int lru = page_lru(page);
Nick Piggin62695a82008-10-18 20:26:09 -07001016 ret = 0;
1017 ClearPageLRU(page);
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001018
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001019 del_page_from_lru_list(zone, page, lru);
Nick Piggin62695a82008-10-18 20:26:09 -07001020 }
1021 spin_unlock_irq(&zone->lru_lock);
1022 }
1023 return ret;
1024}
1025
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001026/*
Andrew Morton1742f192006-03-22 00:08:21 -08001027 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1028 * of reclaimed pages
Linus Torvalds1da177e2005-04-16 15:20:36 -07001029 */
Andrew Morton1742f192006-03-22 00:08:21 -08001030static unsigned long shrink_inactive_list(unsigned long max_scan,
Rik van Riel33c120e2008-10-18 20:26:36 -07001031 struct zone *zone, struct scan_control *sc,
1032 int priority, int file)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033{
1034 LIST_HEAD(page_list);
1035 struct pagevec pvec;
Andrew Morton69e05942006-03-22 00:08:19 -08001036 unsigned long nr_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -08001037 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038
1039 pagevec_init(&pvec, 1);
1040
1041 lru_add_drain();
1042 spin_lock_irq(&zone->lru_lock);
Andrew Morton69e05942006-03-22 00:08:19 -08001043 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001044 struct page *page;
Andrew Morton69e05942006-03-22 00:08:19 -08001045 unsigned long nr_taken;
1046 unsigned long nr_scan;
1047 unsigned long nr_freed;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001048 unsigned long nr_active;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001049 unsigned int count[NR_LRU_LISTS] = { 0, };
Rik van Riel33c120e2008-10-18 20:26:36 -07001050 int mode = ISOLATE_INACTIVE;
1051
1052 /*
1053 * If we need a large contiguous chunk of memory, or have
1054 * trouble getting a small set of contiguous pages, we
1055 * will reclaim both active and inactive pages.
1056 *
1057 * We use the same threshold as pageout congestion_wait below.
1058 */
1059 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1060 mode = ISOLATE_BOTH;
1061 else if (sc->order && priority < DEF_PRIORITY - 2)
1062 mode = ISOLATE_BOTH;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001063
Balbir Singh66e17072008-02-07 00:13:56 -08001064 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001065 &page_list, &nr_scan, sc->order, mode,
1066 zone, sc->mem_cgroup, 0, file);
1067 nr_active = clear_active_flags(&page_list, count);
Andy Whitcrofte9187bd2007-08-22 14:01:25 -07001068 __count_vm_events(PGDEACTIVATE, nr_active);
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001069
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001070 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1071 -count[LRU_ACTIVE_FILE]);
1072 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1073 -count[LRU_INACTIVE_FILE]);
1074 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1075 -count[LRU_ACTIVE_ANON]);
1076 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1077 -count[LRU_INACTIVE_ANON]);
1078
1079 if (scan_global_lru(sc)) {
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001080 zone->pages_scanned += nr_scan;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001081 zone->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1082 zone->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1083 zone->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1084 zone->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1085 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086 spin_unlock_irq(&zone->lru_lock);
1087
Andrew Morton69e05942006-03-22 00:08:19 -08001088 nr_scanned += nr_scan;
Andy Whitcroftc661b072007-08-22 14:01:26 -07001089 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1090
1091 /*
1092 * If we are direct reclaiming for contiguous pages and we do
1093 * not reclaim everything in the list, try again and wait
1094 * for IO to complete. This will stall high-order allocations
1095 * but that should be acceptable to the caller
1096 */
1097 if (nr_freed < nr_taken && !current_is_kswapd() &&
1098 sc->order > PAGE_ALLOC_COSTLY_ORDER) {
1099 congestion_wait(WRITE, HZ/10);
1100
1101 /*
1102 * The attempt at page out may have made some
1103 * of the pages active, mark them inactive again.
1104 */
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001105 nr_active = clear_active_flags(&page_list, count);
Andy Whitcroftc661b072007-08-22 14:01:26 -07001106 count_vm_events(PGDEACTIVATE, nr_active);
1107
1108 nr_freed += shrink_page_list(&page_list, sc,
1109 PAGEOUT_IO_SYNC);
1110 }
1111
Andrew Morton05ff5132006-03-22 00:08:20 -08001112 nr_reclaimed += nr_freed;
Nick Piggina74609f2006-01-06 00:11:20 -08001113 local_irq_disable();
1114 if (current_is_kswapd()) {
Christoph Lameterf8891e52006-06-30 01:55:45 -07001115 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
1116 __count_vm_events(KSWAPD_STEAL, nr_freed);
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001117 } else if (scan_global_lru(sc))
Christoph Lameterf8891e52006-06-30 01:55:45 -07001118 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001119
Shantanu Goel918d3f92006-12-29 16:48:59 -08001120 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
Nick Piggina74609f2006-01-06 00:11:20 -08001121
Wu Fengguangfb8d14e2006-03-22 00:08:28 -08001122 if (nr_taken == 0)
1123 goto done;
1124
Nick Piggina74609f2006-01-06 00:11:20 -08001125 spin_lock(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001126 /*
1127 * Put back any unfreeable pages.
1128 */
1129 while (!list_empty(&page_list)) {
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001130 int lru;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001131 page = lru_to_page(&page_list);
Nick Piggin725d7042006-09-25 23:30:55 -07001132 VM_BUG_ON(PageLRU(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001133 list_del(&page->lru);
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001134 if (unlikely(!page_evictable(page, NULL))) {
1135 spin_unlock_irq(&zone->lru_lock);
1136 putback_lru_page(page);
1137 spin_lock_irq(&zone->lru_lock);
1138 continue;
1139 }
1140 SetPageLRU(page);
1141 lru = page_lru(page);
1142 add_page_to_lru_list(zone, page, lru);
1143 mem_cgroup_move_lists(page, lru);
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001144 if (PageActive(page) && scan_global_lru(sc)) {
1145 int file = !!page_is_file_cache(page);
1146 zone->recent_rotated[file]++;
1147 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001148 if (!pagevec_add(&pvec, page)) {
1149 spin_unlock_irq(&zone->lru_lock);
1150 __pagevec_release(&pvec);
1151 spin_lock_irq(&zone->lru_lock);
1152 }
1153 }
Andrew Morton69e05942006-03-22 00:08:19 -08001154 } while (nr_scanned < max_scan);
Wu Fengguangfb8d14e2006-03-22 00:08:28 -08001155 spin_unlock(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001156done:
Wu Fengguangfb8d14e2006-03-22 00:08:28 -08001157 local_irq_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 pagevec_release(&pvec);
Andrew Morton05ff5132006-03-22 00:08:20 -08001159 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001160}
1161
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001162/*
1163 * We are about to scan this zone at a certain priority level. If that priority
1164 * level is smaller (ie: more urgent) than the previous priority, then note
1165 * that priority level within the zone. This is done so that when the next
1166 * process comes in to scan this zone, it will immediately start out at this
1167 * priority level rather than having to build up its own scanning priority.
1168 * Here, this priority affects only the reclaim-mapped threshold.
1169 */
1170static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1171{
1172 if (priority < zone->prev_priority)
1173 zone->prev_priority = priority;
1174}
1175
Nick Piggin4ff1ffb2006-09-25 23:31:28 -07001176static inline int zone_is_near_oom(struct zone *zone)
1177{
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001178 return zone->pages_scanned >= (zone_lru_pages(zone) * 3);
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001179}
1180
1181/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001182 * This moves pages from the active list to the inactive list.
1183 *
1184 * We move them the other way if the page is referenced by one or more
1185 * processes, from rmap.
1186 *
1187 * If the pages are mostly unmapped, the processing is fast and it is
1188 * appropriate to hold zone->lru_lock across the whole operation. But if
1189 * the pages are mapped, the processing is slow (page_referenced()) so we
1190 * should drop zone->lru_lock around each page. It's impossible to balance
1191 * this, so instead we remove the pages from the LRU while processing them.
1192 * It is safe to rely on PG_active against the non-LRU pages in here because
1193 * nobody will play with that bit on a non-LRU page.
1194 *
1195 * The downside is that we have to touch page->_count against each page.
1196 * But we had to alter page->flags anyway.
1197 */
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001198
1199
Andrew Morton1742f192006-03-22 00:08:21 -08001200static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001201 struct scan_control *sc, int priority, int file)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001202{
Andrew Morton69e05942006-03-22 00:08:19 -08001203 unsigned long pgmoved;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001204 int pgdeactivate = 0;
Andrew Morton69e05942006-03-22 00:08:19 -08001205 unsigned long pgscanned;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001206 LIST_HEAD(l_hold); /* The pages which were snipped off */
Christoph Lameterb69408e2008-10-18 20:26:14 -07001207 LIST_HEAD(l_inactive);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001208 struct page *page;
1209 struct pagevec pvec;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001210 enum lru_list lru;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001211
1212 lru_add_drain();
1213 spin_lock_irq(&zone->lru_lock);
Balbir Singh66e17072008-02-07 00:13:56 -08001214 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1215 ISOLATE_ACTIVE, zone,
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001216 sc->mem_cgroup, 1, file);
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001217 /*
1218 * zone->pages_scanned is used for detect zone's oom
1219 * mem_cgroup remembers nr_scan by itself.
1220 */
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001221 if (scan_global_lru(sc)) {
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001222 zone->pages_scanned += pgscanned;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001223 zone->recent_scanned[!!file] += pgmoved;
1224 }
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001225
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001226 if (file)
1227 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1228 else
1229 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001230 spin_unlock_irq(&zone->lru_lock);
1231
Rik van Riel556adec2008-10-18 20:26:34 -07001232 pgmoved = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001233 while (!list_empty(&l_hold)) {
1234 cond_resched();
1235 page = lru_to_page(&l_hold);
1236 list_del(&page->lru);
Rik van Riel7e9cd482008-10-18 20:26:35 -07001237
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001238 if (unlikely(!page_evictable(page, NULL))) {
1239 putback_lru_page(page);
1240 continue;
1241 }
1242
Rik van Riel7e9cd482008-10-18 20:26:35 -07001243 /* page_referenced clears PageReferenced */
1244 if (page_mapping_inuse(page) &&
1245 page_referenced(page, 0, sc->mem_cgroup))
1246 pgmoved++;
1247
Linus Torvalds1da177e2005-04-16 15:20:36 -07001248 list_add(&page->lru, &l_inactive);
1249 }
1250
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001251 /*
Rik van Riel7e9cd482008-10-18 20:26:35 -07001252 * Count referenced pages from currently used mappings as
1253 * rotated, even though they are moved to the inactive list.
1254 * This helps balance scan pressure between file and anonymous
1255 * pages in get_scan_ratio.
1256 */
Rik van Riel556adec2008-10-18 20:26:34 -07001257 zone->recent_rotated[!!file] += pgmoved;
1258
1259 /*
Rik van Riel7e9cd482008-10-18 20:26:35 -07001260 * Move the pages to the [file or anon] inactive list.
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001261 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001262 pagevec_init(&pvec, 1);
Rik van Riel7e9cd482008-10-18 20:26:35 -07001263
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264 pgmoved = 0;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001265 lru = LRU_BASE + file * LRU_FILE;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001266 spin_lock_irq(&zone->lru_lock);
1267 while (!list_empty(&l_inactive)) {
1268 page = lru_to_page(&l_inactive);
1269 prefetchw_prev_lru_page(page, &l_inactive, flags);
Nick Piggin725d7042006-09-25 23:30:55 -07001270 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -08001271 SetPageLRU(page);
Nick Piggin725d7042006-09-25 23:30:55 -07001272 VM_BUG_ON(!PageActive(page));
Nick Piggin4c84cac2006-03-22 00:08:00 -08001273 ClearPageActive(page);
1274
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001275 list_move(&page->lru, &zone->lru[lru].list);
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001276 mem_cgroup_move_lists(page, lru);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001277 pgmoved++;
1278 if (!pagevec_add(&pvec, page)) {
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001279 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001280 spin_unlock_irq(&zone->lru_lock);
1281 pgdeactivate += pgmoved;
1282 pgmoved = 0;
1283 if (buffer_heads_over_limit)
1284 pagevec_strip(&pvec);
1285 __pagevec_release(&pvec);
1286 spin_lock_irq(&zone->lru_lock);
1287 }
1288 }
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001289 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001290 pgdeactivate += pgmoved;
1291 if (buffer_heads_over_limit) {
1292 spin_unlock_irq(&zone->lru_lock);
1293 pagevec_strip(&pvec);
1294 spin_lock_irq(&zone->lru_lock);
1295 }
Christoph Lameterf8891e52006-06-30 01:55:45 -07001296 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1297 __count_vm_events(PGDEACTIVATE, pgdeactivate);
1298 spin_unlock_irq(&zone->lru_lock);
Rik van Riel68a223942008-10-18 20:26:23 -07001299 if (vm_swap_full())
1300 pagevec_swap_free(&pvec);
Nick Piggina74609f2006-01-06 00:11:20 -08001301
1302 pagevec_release(&pvec);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001303}
1304
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001305static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
Christoph Lameterb69408e2008-10-18 20:26:14 -07001306 struct zone *zone, struct scan_control *sc, int priority)
1307{
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001308 int file = is_file_lru(lru);
1309
Rik van Riel556adec2008-10-18 20:26:34 -07001310 if (lru == LRU_ACTIVE_FILE) {
1311 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1312 return 0;
1313 }
1314
1315 if (lru == LRU_ACTIVE_ANON &&
1316 (!scan_global_lru(sc) || inactive_anon_is_low(zone))) {
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001317 shrink_active_list(nr_to_scan, zone, sc, priority, file);
Christoph Lameterb69408e2008-10-18 20:26:14 -07001318 return 0;
1319 }
Rik van Riel33c120e2008-10-18 20:26:36 -07001320 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
Christoph Lameterb69408e2008-10-18 20:26:14 -07001321}
1322
Linus Torvalds1da177e2005-04-16 15:20:36 -07001323/*
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001324 * Determine how aggressively the anon and file LRU lists should be
1325 * scanned. The relative value of each set of LRU lists is determined
1326 * by looking at the fraction of the pages scanned we did rotate back
1327 * onto the active list instead of evict.
1328 *
1329 * percent[0] specifies how much pressure to put on ram/swap backed
1330 * memory, while percent[1] determines pressure on the file LRUs.
1331 */
1332static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1333 unsigned long *percent)
1334{
1335 unsigned long anon, file, free;
1336 unsigned long anon_prio, file_prio;
1337 unsigned long ap, fp;
1338
1339 anon = zone_page_state(zone, NR_ACTIVE_ANON) +
1340 zone_page_state(zone, NR_INACTIVE_ANON);
1341 file = zone_page_state(zone, NR_ACTIVE_FILE) +
1342 zone_page_state(zone, NR_INACTIVE_FILE);
1343 free = zone_page_state(zone, NR_FREE_PAGES);
1344
1345 /* If we have no swap space, do not bother scanning anon pages. */
1346 if (nr_swap_pages <= 0) {
1347 percent[0] = 0;
1348 percent[1] = 100;
1349 return;
1350 }
1351
1352 /* If we have very few page cache pages, force-scan anon pages. */
1353 if (unlikely(file + free <= zone->pages_high)) {
1354 percent[0] = 100;
1355 percent[1] = 0;
1356 return;
1357 }
1358
1359 /*
1360 * OK, so we have swap space and a fair amount of page cache
1361 * pages. We use the recently rotated / recently scanned
1362 * ratios to determine how valuable each cache is.
1363 *
1364 * Because workloads change over time (and to avoid overflow)
1365 * we keep these statistics as a floating average, which ends
1366 * up weighing recent references more than old ones.
1367 *
1368 * anon in [0], file in [1]
1369 */
1370 if (unlikely(zone->recent_scanned[0] > anon / 4)) {
1371 spin_lock_irq(&zone->lru_lock);
1372 zone->recent_scanned[0] /= 2;
1373 zone->recent_rotated[0] /= 2;
1374 spin_unlock_irq(&zone->lru_lock);
1375 }
1376
1377 if (unlikely(zone->recent_scanned[1] > file / 4)) {
1378 spin_lock_irq(&zone->lru_lock);
1379 zone->recent_scanned[1] /= 2;
1380 zone->recent_rotated[1] /= 2;
1381 spin_unlock_irq(&zone->lru_lock);
1382 }
1383
1384 /*
1385 * With swappiness at 100, anonymous and file have the same priority.
1386 * This scanning priority is essentially the inverse of IO cost.
1387 */
1388 anon_prio = sc->swappiness;
1389 file_prio = 200 - sc->swappiness;
1390
1391 /*
1392 * anon recent_rotated[0]
1393 * %anon = 100 * ----------- / ----------------- * IO cost
1394 * anon + file rotate_sum
1395 */
1396 ap = (anon_prio + 1) * (zone->recent_scanned[0] + 1);
1397 ap /= zone->recent_rotated[0] + 1;
1398
1399 fp = (file_prio + 1) * (zone->recent_scanned[1] + 1);
1400 fp /= zone->recent_rotated[1] + 1;
1401
1402 /* Normalize to percentages */
1403 percent[0] = 100 * ap / (ap + fp + 1);
1404 percent[1] = 100 - percent[0];
1405}
1406
1407
1408/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001409 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1410 */
Andrew Morton05ff5132006-03-22 00:08:20 -08001411static unsigned long shrink_zone(int priority, struct zone *zone,
1412 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001413{
Christoph Lameterb69408e2008-10-18 20:26:14 -07001414 unsigned long nr[NR_LRU_LISTS];
Christoph Lameter86959492006-03-22 00:08:18 -08001415 unsigned long nr_to_scan;
Andrew Morton05ff5132006-03-22 00:08:20 -08001416 unsigned long nr_reclaimed = 0;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001417 unsigned long percent[2]; /* anon @ 0; file @ 1 */
Christoph Lameterb69408e2008-10-18 20:26:14 -07001418 enum lru_list l;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001419
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001420 get_scan_ratio(zone, sc, percent);
1421
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001422 for_each_evictable_lru(l) {
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001423 if (scan_global_lru(sc)) {
1424 int file = is_file_lru(l);
1425 int scan;
Johannes Weinere0f79b82008-10-18 20:26:55 -07001426
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001427 scan = zone_page_state(zone, NR_LRU_BASE + l);
1428 if (priority) {
1429 scan >>= priority;
1430 scan = (scan * percent[file]) / 100;
1431 }
Johannes Weinere0f79b82008-10-18 20:26:55 -07001432 zone->lru[l].nr_scan += scan;
Christoph Lameterb69408e2008-10-18 20:26:14 -07001433 nr[l] = zone->lru[l].nr_scan;
1434 if (nr[l] >= sc->swap_cluster_max)
1435 zone->lru[l].nr_scan = 0;
1436 else
1437 nr[l] = 0;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001438 } else {
1439 /*
1440 * This reclaim occurs not because zone memory shortage
1441 * but because memory controller hits its limit.
1442 * Don't modify zone reclaim related data.
1443 */
1444 nr[l] = mem_cgroup_calc_reclaim(sc->mem_cgroup, zone,
1445 priority, l);
Christoph Lameterb69408e2008-10-18 20:26:14 -07001446 }
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001447 }
1448
Rik van Riel556adec2008-10-18 20:26:34 -07001449 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1450 nr[LRU_INACTIVE_FILE]) {
Lee Schermerhorn894bc312008-10-18 20:26:39 -07001451 for_each_evictable_lru(l) {
Christoph Lameterb69408e2008-10-18 20:26:14 -07001452 if (nr[l]) {
1453 nr_to_scan = min(nr[l],
Linus Torvalds1da177e2005-04-16 15:20:36 -07001454 (unsigned long)sc->swap_cluster_max);
Christoph Lameterb69408e2008-10-18 20:26:14 -07001455 nr[l] -= nr_to_scan;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001456
Christoph Lameterb69408e2008-10-18 20:26:14 -07001457 nr_reclaimed += shrink_list(l, nr_to_scan,
1458 zone, sc, priority);
1459 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001460 }
1461 }
1462
Rik van Riel556adec2008-10-18 20:26:34 -07001463 /*
1464 * Even if we did not try to evict anon pages at all, we want to
1465 * rebalance the anon lru active/inactive ratio.
1466 */
1467 if (!scan_global_lru(sc) || inactive_anon_is_low(zone))
1468 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1469 else if (!scan_global_lru(sc))
1470 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1471
Andrew Morton232ea4d2007-02-28 20:13:21 -08001472 throttle_vm_writeout(sc->gfp_mask);
Andrew Morton05ff5132006-03-22 00:08:20 -08001473 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001474}
1475
1476/*
1477 * This is the direct reclaim path, for page-allocating processes. We only
1478 * try to reclaim pages from zones which will satisfy the caller's allocation
1479 * request.
1480 *
1481 * We reclaim from a zone even if that zone is over pages_high. Because:
1482 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1483 * allocation or
1484 * b) The zones may be over pages_high but they must go *over* pages_high to
1485 * satisfy the `incremental min' zone defense algorithm.
1486 *
1487 * Returns the number of reclaimed pages.
1488 *
1489 * If a zone is deemed to be full of pinned pages then just give it a light
1490 * scan then give up on it.
1491 */
Mel Gormandac1d272008-04-28 02:12:12 -07001492static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
Andrew Morton05ff5132006-03-22 00:08:20 -08001493 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001494{
Mel Gorman54a6eb52008-04-28 02:12:16 -07001495 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
Andrew Morton05ff5132006-03-22 00:08:20 -08001496 unsigned long nr_reclaimed = 0;
Mel Gormandd1a2392008-04-28 02:12:17 -07001497 struct zoneref *z;
Mel Gorman54a6eb52008-04-28 02:12:16 -07001498 struct zone *zone;
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001499
Nick Piggin408d8542006-09-25 23:31:27 -07001500 sc->all_unreclaimable = 1;
Mel Gorman54a6eb52008-04-28 02:12:16 -07001501 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
Con Kolivasf3fe6512006-01-06 00:11:15 -08001502 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503 continue;
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001504 /*
1505 * Take care memory controller reclaiming has small influence
1506 * to global LRU.
1507 */
1508 if (scan_global_lru(sc)) {
1509 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1510 continue;
1511 note_zone_scanning_priority(zone, priority);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001512
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001513 if (zone_is_all_unreclaimable(zone) &&
1514 priority != DEF_PRIORITY)
1515 continue; /* Let kswapd poll it */
1516 sc->all_unreclaimable = 0;
1517 } else {
1518 /*
1519 * Ignore cpuset limitation here. We just want to reduce
1520 * # of used pages by us regardless of memory shortage.
1521 */
1522 sc->all_unreclaimable = 0;
1523 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1524 priority);
1525 }
Nick Piggin408d8542006-09-25 23:31:27 -07001526
Andrew Morton05ff5132006-03-22 00:08:20 -08001527 nr_reclaimed += shrink_zone(priority, zone, sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001528 }
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001529
Andrew Morton05ff5132006-03-22 00:08:20 -08001530 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001531}
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001532
Linus Torvalds1da177e2005-04-16 15:20:36 -07001533/*
1534 * This is the main entry point to direct page reclaim.
1535 *
1536 * If a full scan of the inactive list fails to free enough memory then we
1537 * are "out of memory" and something needs to be killed.
1538 *
1539 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1540 * high - the zone may be full of dirty or under-writeback pages, which this
1541 * caller can't do much about. We kick pdflush and take explicit naps in the
1542 * hope that some of these pages can be written. But if the allocating task
1543 * holds filesystem locks which prevent writeout this might not work, and the
1544 * allocation attempt will fail.
Nishanth Aravamudana41f24e2008-04-29 00:58:25 -07001545 *
1546 * returns: 0, if no pages reclaimed
1547 * else, the number of pages reclaimed
Linus Torvalds1da177e2005-04-16 15:20:36 -07001548 */
Mel Gormandac1d272008-04-28 02:12:12 -07001549static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
Mel Gormandd1a2392008-04-28 02:12:17 -07001550 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001551{
1552 int priority;
kosaki.motohiro@jp.fujitsu.comc700be32008-06-12 15:21:27 -07001553 unsigned long ret = 0;
Andrew Morton69e05942006-03-22 00:08:19 -08001554 unsigned long total_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -08001555 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001556 struct reclaim_state *reclaim_state = current->reclaim_state;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001557 unsigned long lru_pages = 0;
Mel Gormandd1a2392008-04-28 02:12:17 -07001558 struct zoneref *z;
Mel Gorman54a6eb52008-04-28 02:12:16 -07001559 struct zone *zone;
Mel Gormandd1a2392008-04-28 02:12:17 -07001560 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001561
Keika Kobayashi873b4772008-07-25 01:48:52 -07001562 delayacct_freepages_start();
1563
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001564 if (scan_global_lru(sc))
1565 count_vm_event(ALLOCSTALL);
1566 /*
1567 * mem_cgroup will not do shrink_slab.
1568 */
1569 if (scan_global_lru(sc)) {
Mel Gorman54a6eb52008-04-28 02:12:16 -07001570 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001571
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001572 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1573 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001574
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001575 lru_pages += zone_lru_pages(zone);
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001576 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001577 }
1578
1579 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
Balbir Singh66e17072008-02-07 00:13:56 -08001580 sc->nr_scanned = 0;
Rik van Rielf7b7fd82005-11-28 13:44:07 -08001581 if (!priority)
1582 disable_swap_token();
Mel Gormandac1d272008-04-28 02:12:12 -07001583 nr_reclaimed += shrink_zones(priority, zonelist, sc);
Balbir Singh66e17072008-02-07 00:13:56 -08001584 /*
1585 * Don't shrink slabs when reclaiming memory from
1586 * over limit cgroups
1587 */
KAMEZAWA Hiroyuki91a45472008-02-07 00:14:29 -08001588 if (scan_global_lru(sc)) {
Mel Gormandd1a2392008-04-28 02:12:17 -07001589 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
KAMEZAWA Hiroyuki91a45472008-02-07 00:14:29 -08001590 if (reclaim_state) {
1591 nr_reclaimed += reclaim_state->reclaimed_slab;
1592 reclaim_state->reclaimed_slab = 0;
1593 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001594 }
Balbir Singh66e17072008-02-07 00:13:56 -08001595 total_scanned += sc->nr_scanned;
1596 if (nr_reclaimed >= sc->swap_cluster_max) {
Nishanth Aravamudana41f24e2008-04-29 00:58:25 -07001597 ret = nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001598 goto out;
1599 }
1600
1601 /*
1602 * Try to write back as many pages as we just scanned. This
1603 * tends to cause slow streaming writers to write data to the
1604 * disk smoothly, at the dirtying rate, which is nice. But
1605 * that's undesirable in laptop mode, where we *want* lumpy
1606 * writeout. So in laptop mode, write out the whole world.
1607 */
Balbir Singh66e17072008-02-07 00:13:56 -08001608 if (total_scanned > sc->swap_cluster_max +
1609 sc->swap_cluster_max / 2) {
Pekka J Enberg687a21c2005-06-28 20:44:55 -07001610 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
Balbir Singh66e17072008-02-07 00:13:56 -08001611 sc->may_writepage = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001612 }
1613
1614 /* Take a nap, wait for some writeback to complete */
Andrew Morton4dd4b922008-03-24 12:29:52 -07001615 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
Andrew Morton3fcfab12006-10-19 23:28:16 -07001616 congestion_wait(WRITE, HZ/10);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001617 }
Fernando Luis Vazquez Cao87547ee2008-07-29 22:33:42 -07001618 /* top priority shrink_zones still had more to do? don't OOM, then */
KAMEZAWA Hiroyuki91a45472008-02-07 00:14:29 -08001619 if (!sc->all_unreclaimable && scan_global_lru(sc))
Nishanth Aravamudana41f24e2008-04-29 00:58:25 -07001620 ret = nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001621out:
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001622 /*
1623 * Now that we've scanned all the zones at this priority level, note
1624 * that level within the zone so that the next thread which performs
1625 * scanning of this zone will immediately start out at this priority
1626 * level. This affects only the decision whether or not to bring
1627 * mapped pages onto the inactive list.
1628 */
1629 if (priority < 0)
1630 priority = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001631
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001632 if (scan_global_lru(sc)) {
Mel Gorman54a6eb52008-04-28 02:12:16 -07001633 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001634
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001635 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1636 continue;
1637
1638 zone->prev_priority = priority;
1639 }
1640 } else
1641 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1642
Keika Kobayashi873b4772008-07-25 01:48:52 -07001643 delayacct_freepages_end();
1644
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645 return ret;
1646}
1647
Mel Gormandac1d272008-04-28 02:12:12 -07001648unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1649 gfp_t gfp_mask)
Balbir Singh66e17072008-02-07 00:13:56 -08001650{
1651 struct scan_control sc = {
1652 .gfp_mask = gfp_mask,
1653 .may_writepage = !laptop_mode,
1654 .swap_cluster_max = SWAP_CLUSTER_MAX,
1655 .may_swap = 1,
1656 .swappiness = vm_swappiness,
1657 .order = order,
1658 .mem_cgroup = NULL,
1659 .isolate_pages = isolate_pages_global,
1660 };
1661
Mel Gormandd1a2392008-04-28 02:12:17 -07001662 return do_try_to_free_pages(zonelist, &sc);
Balbir Singh66e17072008-02-07 00:13:56 -08001663}
1664
Balbir Singh00f0b822008-03-04 14:28:39 -08001665#ifdef CONFIG_CGROUP_MEM_RES_CTLR
Balbir Singh66e17072008-02-07 00:13:56 -08001666
Balbir Singhe1a1cd52008-02-07 00:14:02 -08001667unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1668 gfp_t gfp_mask)
Balbir Singh66e17072008-02-07 00:13:56 -08001669{
1670 struct scan_control sc = {
Balbir Singh66e17072008-02-07 00:13:56 -08001671 .may_writepage = !laptop_mode,
1672 .may_swap = 1,
1673 .swap_cluster_max = SWAP_CLUSTER_MAX,
1674 .swappiness = vm_swappiness,
1675 .order = 0,
1676 .mem_cgroup = mem_cont,
1677 .isolate_pages = mem_cgroup_isolate_pages,
1678 };
Mel Gormandac1d272008-04-28 02:12:12 -07001679 struct zonelist *zonelist;
Balbir Singh66e17072008-02-07 00:13:56 -08001680
Mel Gormandd1a2392008-04-28 02:12:17 -07001681 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1682 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1683 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1684 return do_try_to_free_pages(zonelist, &sc);
Balbir Singh66e17072008-02-07 00:13:56 -08001685}
1686#endif
1687
Linus Torvalds1da177e2005-04-16 15:20:36 -07001688/*
1689 * For kswapd, balance_pgdat() will work across all this node's zones until
1690 * they are all at pages_high.
1691 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001692 * Returns the number of pages which were actually freed.
1693 *
1694 * There is special handling here for zones which are full of pinned pages.
1695 * This can happen if the pages are all mlocked, or if they are all used by
1696 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1697 * What we do is to detect the case where all pages in the zone have been
1698 * scanned twice and there has been zero successful reclaim. Mark the zone as
1699 * dead and from now on, only perform a short scan. Basically we're polling
1700 * the zone for when the problem goes away.
1701 *
1702 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1703 * zones which have free_pages > pages_high, but once a zone is found to have
1704 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1705 * of the number of free pages in the lower zones. This interoperates with
1706 * the page allocator fallback scheme to ensure that aging of pages is balanced
1707 * across the zones.
1708 */
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001709static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001710{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001711 int all_zones_ok;
1712 int priority;
1713 int i;
Andrew Morton69e05942006-03-22 00:08:19 -08001714 unsigned long total_scanned;
Andrew Morton05ff5132006-03-22 00:08:20 -08001715 unsigned long nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001716 struct reclaim_state *reclaim_state = current->reclaim_state;
Andrew Morton179e9632006-03-22 00:08:18 -08001717 struct scan_control sc = {
1718 .gfp_mask = GFP_KERNEL,
1719 .may_swap = 1,
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001720 .swap_cluster_max = SWAP_CLUSTER_MAX,
1721 .swappiness = vm_swappiness,
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001722 .order = order,
Balbir Singh66e17072008-02-07 00:13:56 -08001723 .mem_cgroup = NULL,
1724 .isolate_pages = isolate_pages_global,
Andrew Morton179e9632006-03-22 00:08:18 -08001725 };
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001726 /*
1727 * temp_priority is used to remember the scanning priority at which
1728 * this zone was successfully refilled to free_pages == pages_high.
1729 */
1730 int temp_priority[MAX_NR_ZONES];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731
1732loop_again:
1733 total_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -08001734 nr_reclaimed = 0;
Christoph Lameterc0bbbc72006-06-11 15:22:26 -07001735 sc.may_writepage = !laptop_mode;
Christoph Lameterf8891e52006-06-30 01:55:45 -07001736 count_vm_event(PAGEOUTRUN);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001737
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001738 for (i = 0; i < pgdat->nr_zones; i++)
1739 temp_priority[i] = DEF_PRIORITY;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001740
1741 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1742 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1743 unsigned long lru_pages = 0;
1744
Rik van Rielf7b7fd82005-11-28 13:44:07 -08001745 /* The swap token gets in the way of swapout... */
1746 if (!priority)
1747 disable_swap_token();
1748
Linus Torvalds1da177e2005-04-16 15:20:36 -07001749 all_zones_ok = 1;
1750
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001751 /*
1752 * Scan in the highmem->dma direction for the highest
1753 * zone which needs scanning
1754 */
1755 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1756 struct zone *zone = pgdat->node_zones + i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001757
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001758 if (!populated_zone(zone))
1759 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001760
David Rientjese815af92007-10-16 23:25:54 -07001761 if (zone_is_all_unreclaimable(zone) &&
1762 priority != DEF_PRIORITY)
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001763 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001764
Rik van Riel556adec2008-10-18 20:26:34 -07001765 /*
1766 * Do some background aging of the anon list, to give
1767 * pages a chance to be referenced before reclaiming.
1768 */
1769 if (inactive_anon_is_low(zone))
1770 shrink_active_list(SWAP_CLUSTER_MAX, zone,
1771 &sc, priority, 0);
1772
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001773 if (!zone_watermark_ok(zone, order, zone->pages_high,
1774 0, 0)) {
1775 end_zone = i;
Andrew Mortone1dbeda2006-12-06 20:32:01 -08001776 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001777 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001778 }
Andrew Mortone1dbeda2006-12-06 20:32:01 -08001779 if (i < 0)
1780 goto out;
1781
Linus Torvalds1da177e2005-04-16 15:20:36 -07001782 for (i = 0; i <= end_zone; i++) {
1783 struct zone *zone = pgdat->node_zones + i;
1784
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001785 lru_pages += zone_lru_pages(zone);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001786 }
1787
1788 /*
1789 * Now scan the zone in the dma->highmem direction, stopping
1790 * at the last zone which needs scanning.
1791 *
1792 * We do this because the page allocator works in the opposite
1793 * direction. This prevents the page allocator from allocating
1794 * pages behind kswapd's direction of progress, which would
1795 * cause too much scanning of the lower zones.
1796 */
1797 for (i = 0; i <= end_zone; i++) {
1798 struct zone *zone = pgdat->node_zones + i;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001799 int nr_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001800
Con Kolivasf3fe6512006-01-06 00:11:15 -08001801 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001802 continue;
1803
David Rientjese815af92007-10-16 23:25:54 -07001804 if (zone_is_all_unreclaimable(zone) &&
1805 priority != DEF_PRIORITY)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001806 continue;
1807
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001808 if (!zone_watermark_ok(zone, order, zone->pages_high,
1809 end_zone, 0))
1810 all_zones_ok = 0;
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001811 temp_priority[i] = priority;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001812 sc.nr_scanned = 0;
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001813 note_zone_scanning_priority(zone, priority);
Rik van Riel32a43302007-10-16 01:24:50 -07001814 /*
1815 * We put equal pressure on every zone, unless one
1816 * zone has way too many pages free already.
1817 */
1818 if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
1819 end_zone, 0))
1820 nr_reclaimed += shrink_zone(priority, zone, &sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001821 reclaim_state->reclaimed_slab = 0;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001822 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1823 lru_pages);
Andrew Morton05ff5132006-03-22 00:08:20 -08001824 nr_reclaimed += reclaim_state->reclaimed_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001825 total_scanned += sc.nr_scanned;
David Rientjese815af92007-10-16 23:25:54 -07001826 if (zone_is_all_unreclaimable(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001827 continue;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001828 if (nr_slab == 0 && zone->pages_scanned >=
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001829 (zone_lru_pages(zone) * 6))
David Rientjese815af92007-10-16 23:25:54 -07001830 zone_set_flag(zone,
1831 ZONE_ALL_UNRECLAIMABLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001832 /*
1833 * If we've done a decent amount of scanning and
1834 * the reclaim ratio is low, start doing writepage
1835 * even in laptop mode
1836 */
1837 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
Andrew Morton05ff5132006-03-22 00:08:20 -08001838 total_scanned > nr_reclaimed + nr_reclaimed / 2)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001839 sc.may_writepage = 1;
1840 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001841 if (all_zones_ok)
1842 break; /* kswapd: all done */
1843 /*
1844 * OK, kswapd is getting into trouble. Take a nap, then take
1845 * another pass across the zones.
1846 */
Andrew Morton4dd4b922008-03-24 12:29:52 -07001847 if (total_scanned && priority < DEF_PRIORITY - 2)
Andrew Morton3fcfab12006-10-19 23:28:16 -07001848 congestion_wait(WRITE, HZ/10);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001849
1850 /*
1851 * We do this so kswapd doesn't build up large priorities for
1852 * example when it is freeing in parallel with allocators. It
1853 * matches the direct reclaim path behaviour in terms of impact
1854 * on zone->*_priority.
1855 */
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001856 if (nr_reclaimed >= SWAP_CLUSTER_MAX)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001857 break;
1858 }
1859out:
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001860 /*
1861 * Note within each zone the priority level at which this zone was
1862 * brought into a happy state. So that the next thread which scans this
1863 * zone will start out at that priority level.
1864 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001865 for (i = 0; i < pgdat->nr_zones; i++) {
1866 struct zone *zone = pgdat->node_zones + i;
1867
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001868 zone->prev_priority = temp_priority[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001869 }
1870 if (!all_zones_ok) {
1871 cond_resched();
Rafael J. Wysocki83573762006-12-06 20:34:18 -08001872
1873 try_to_freeze();
1874
Linus Torvalds1da177e2005-04-16 15:20:36 -07001875 goto loop_again;
1876 }
1877
Andrew Morton05ff5132006-03-22 00:08:20 -08001878 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001879}
1880
1881/*
1882 * The background pageout daemon, started as a kernel thread
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001883 * from the init process.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001884 *
1885 * This basically trickles out pages so that we have _some_
1886 * free memory available even if there is no other activity
1887 * that frees anything up. This is needed for things like routing
1888 * etc, where we otherwise might have all activity going on in
1889 * asynchronous contexts that cannot page things out.
1890 *
1891 * If there are applications that are active memory-allocators
1892 * (most normal use), this basically shouldn't matter.
1893 */
1894static int kswapd(void *p)
1895{
1896 unsigned long order;
1897 pg_data_t *pgdat = (pg_data_t*)p;
1898 struct task_struct *tsk = current;
1899 DEFINE_WAIT(wait);
1900 struct reclaim_state reclaim_state = {
1901 .reclaimed_slab = 0,
1902 };
Mike Travisc5f59f02008-04-04 18:11:10 -07001903 node_to_cpumask_ptr(cpumask, pgdat->node_id);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001904
Mike Travisc5f59f02008-04-04 18:11:10 -07001905 if (!cpus_empty(*cpumask))
1906 set_cpus_allowed_ptr(tsk, cpumask);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001907 current->reclaim_state = &reclaim_state;
1908
1909 /*
1910 * Tell the memory management that we're a "memory allocator",
1911 * and that if we need more memory we should get access to it
1912 * regardless (see "__alloc_pages()"). "kswapd" should
1913 * never get caught in the normal page freeing logic.
1914 *
1915 * (Kswapd normally doesn't need memory anyway, but sometimes
1916 * you need a small amount of memory in order to be able to
1917 * page out something else, and this flag essentially protects
1918 * us from recursively trying to free more memory as we're
1919 * trying to free the first piece of memory in the first place).
1920 */
Christoph Lameter930d9152006-01-08 01:00:47 -08001921 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
Rafael J. Wysocki83144182007-07-17 04:03:35 -07001922 set_freezable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001923
1924 order = 0;
1925 for ( ; ; ) {
1926 unsigned long new_order;
Christoph Lameter3e1d1d22005-06-24 23:13:50 -07001927
Linus Torvalds1da177e2005-04-16 15:20:36 -07001928 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1929 new_order = pgdat->kswapd_max_order;
1930 pgdat->kswapd_max_order = 0;
1931 if (order < new_order) {
1932 /*
1933 * Don't sleep if someone wants a larger 'order'
1934 * allocation
1935 */
1936 order = new_order;
1937 } else {
Rafael J. Wysockib1296cc2007-05-06 14:50:48 -07001938 if (!freezing(current))
1939 schedule();
1940
Linus Torvalds1da177e2005-04-16 15:20:36 -07001941 order = pgdat->kswapd_max_order;
1942 }
1943 finish_wait(&pgdat->kswapd_wait, &wait);
1944
Rafael J. Wysockib1296cc2007-05-06 14:50:48 -07001945 if (!try_to_freeze()) {
1946 /* We can speed up thawing tasks if we don't call
1947 * balance_pgdat after returning from the refrigerator
1948 */
1949 balance_pgdat(pgdat, order);
1950 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001951 }
1952 return 0;
1953}
1954
1955/*
1956 * A zone is low on free memory, so wake its kswapd task to service it.
1957 */
1958void wakeup_kswapd(struct zone *zone, int order)
1959{
1960 pg_data_t *pgdat;
1961
Con Kolivasf3fe6512006-01-06 00:11:15 -08001962 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001963 return;
1964
1965 pgdat = zone->zone_pgdat;
Rohit Seth7fb1d9f2005-11-13 16:06:43 -08001966 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001967 return;
1968 if (pgdat->kswapd_max_order < order)
1969 pgdat->kswapd_max_order = order;
Paul Jackson02a0e532006-12-13 00:34:25 -08001970 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001971 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001972 if (!waitqueue_active(&pgdat->kswapd_wait))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001973 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001974 wake_up_interruptible(&pgdat->kswapd_wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001975}
1976
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001977unsigned long global_lru_pages(void)
1978{
1979 return global_page_state(NR_ACTIVE_ANON)
1980 + global_page_state(NR_ACTIVE_FILE)
1981 + global_page_state(NR_INACTIVE_ANON)
1982 + global_page_state(NR_INACTIVE_FILE);
1983}
1984
Linus Torvalds1da177e2005-04-16 15:20:36 -07001985#ifdef CONFIG_PM
1986/*
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001987 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1988 * from LRU lists system-wide, for given pass and priority, and returns the
1989 * number of reclaimed pages
1990 *
1991 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1992 */
Nigel Cunninghame07aa052006-12-22 01:07:21 -08001993static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
1994 int pass, struct scan_control *sc)
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001995{
1996 struct zone *zone;
1997 unsigned long nr_to_scan, ret = 0;
Christoph Lameterb69408e2008-10-18 20:26:14 -07001998 enum lru_list l;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001999
2000 for_each_zone(zone) {
2001
2002 if (!populated_zone(zone))
2003 continue;
2004
David Rientjese815af92007-10-16 23:25:54 -07002005 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002006 continue;
2007
Lee Schermerhorn894bc312008-10-18 20:26:39 -07002008 for_each_evictable_lru(l) {
2009 /* For pass = 0, we don't shrink the active list */
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002010 if (pass == 0 &&
2011 (l == LRU_ACTIVE || l == LRU_ACTIVE_FILE))
Christoph Lameterb69408e2008-10-18 20:26:14 -07002012 continue;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002013
Christoph Lameterb69408e2008-10-18 20:26:14 -07002014 zone->lru[l].nr_scan +=
2015 (zone_page_state(zone, NR_LRU_BASE + l)
2016 >> prio) + 1;
2017 if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
2018 zone->lru[l].nr_scan = 0;
2019 nr_to_scan = min(nr_pages,
2020 zone_page_state(zone,
2021 NR_LRU_BASE + l));
2022 ret += shrink_list(l, nr_to_scan, zone,
2023 sc, prio);
2024 if (ret >= nr_pages)
2025 return ret;
2026 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002027 }
2028 }
2029
2030 return ret;
2031}
2032
2033/*
2034 * Try to free `nr_pages' of memory, system-wide, and return the number of
2035 * freed pages.
2036 *
2037 * Rather than trying to age LRUs the aim is to preserve the overall
2038 * LRU order by reclaiming preferentially
2039 * inactive > active > active referenced > active mapped
Linus Torvalds1da177e2005-04-16 15:20:36 -07002040 */
Andrew Morton69e05942006-03-22 00:08:19 -08002041unsigned long shrink_all_memory(unsigned long nr_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002042{
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002043 unsigned long lru_pages, nr_slab;
Andrew Morton69e05942006-03-22 00:08:19 -08002044 unsigned long ret = 0;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002045 int pass;
2046 struct reclaim_state reclaim_state;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002047 struct scan_control sc = {
2048 .gfp_mask = GFP_KERNEL,
2049 .may_swap = 0,
2050 .swap_cluster_max = nr_pages,
2051 .may_writepage = 1,
2052 .swappiness = vm_swappiness,
Balbir Singh66e17072008-02-07 00:13:56 -08002053 .isolate_pages = isolate_pages_global,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002054 };
2055
2056 current->reclaim_state = &reclaim_state;
Andrew Morton69e05942006-03-22 00:08:19 -08002057
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002058 lru_pages = global_lru_pages();
Christoph Lameter972d1a72006-09-25 23:31:51 -07002059 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002060 /* If slab caches are huge, it's better to hit them first */
2061 while (nr_slab >= lru_pages) {
2062 reclaim_state.reclaimed_slab = 0;
2063 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
2064 if (!reclaim_state.reclaimed_slab)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002065 break;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002066
2067 ret += reclaim_state.reclaimed_slab;
2068 if (ret >= nr_pages)
2069 goto out;
2070
2071 nr_slab -= reclaim_state.reclaimed_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002072 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002073
2074 /*
2075 * We try to shrink LRUs in 5 passes:
2076 * 0 = Reclaim from inactive_list only
2077 * 1 = Reclaim from active list but don't reclaim mapped
2078 * 2 = 2nd pass of type 1
2079 * 3 = Reclaim mapped (normal reclaim)
2080 * 4 = 2nd pass of type 3
2081 */
2082 for (pass = 0; pass < 5; pass++) {
2083 int prio;
2084
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002085 /* Force reclaiming mapped pages in the passes #3 and #4 */
2086 if (pass > 2) {
2087 sc.may_swap = 1;
2088 sc.swappiness = 100;
2089 }
2090
2091 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2092 unsigned long nr_to_scan = nr_pages - ret;
2093
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002094 sc.nr_scanned = 0;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002095 ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
2096 if (ret >= nr_pages)
2097 goto out;
2098
2099 reclaim_state.reclaimed_slab = 0;
Andrew Morton76395d32007-01-05 16:37:05 -08002100 shrink_slab(sc.nr_scanned, sc.gfp_mask,
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002101 global_lru_pages());
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002102 ret += reclaim_state.reclaimed_slab;
2103 if (ret >= nr_pages)
2104 goto out;
2105
2106 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
Andrew Morton3fcfab12006-10-19 23:28:16 -07002107 congestion_wait(WRITE, HZ / 10);
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002108 }
Rafael J. Wysocki248a0302006-03-22 00:09:04 -08002109 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002110
2111 /*
2112 * If ret = 0, we could not shrink LRUs, but there may be something
2113 * in slab caches
2114 */
Andrew Morton76395d32007-01-05 16:37:05 -08002115 if (!ret) {
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002116 do {
2117 reclaim_state.reclaimed_slab = 0;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07002118 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002119 ret += reclaim_state.reclaimed_slab;
2120 } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
Andrew Morton76395d32007-01-05 16:37:05 -08002121 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002122
2123out:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002124 current->reclaim_state = NULL;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002125
Linus Torvalds1da177e2005-04-16 15:20:36 -07002126 return ret;
2127}
2128#endif
2129
Linus Torvalds1da177e2005-04-16 15:20:36 -07002130/* It's optimal to keep kswapds on the same CPUs as their memory, but
2131 not required for correctness. So if the last cpu in a node goes
2132 away, we get changed to run anywhere: as the first one comes back,
2133 restore their cpu bindings. */
Chandra Seetharaman9c7b2162006-06-27 02:54:07 -07002134static int __devinit cpu_callback(struct notifier_block *nfb,
Andrew Morton69e05942006-03-22 00:08:19 -08002135 unsigned long action, void *hcpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002136{
Yasunori Goto58c0a4a2007-10-16 01:25:40 -07002137 int nid;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002138
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07002139 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
Yasunori Goto58c0a4a2007-10-16 01:25:40 -07002140 for_each_node_state(nid, N_HIGH_MEMORY) {
Mike Travisc5f59f02008-04-04 18:11:10 -07002141 pg_data_t *pgdat = NODE_DATA(nid);
2142 node_to_cpumask_ptr(mask, pgdat->node_id);
2143
2144 if (any_online_cpu(*mask) < nr_cpu_ids)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002145 /* One of our CPUs online: restore mask */
Mike Travisc5f59f02008-04-04 18:11:10 -07002146 set_cpus_allowed_ptr(pgdat->kswapd, mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002147 }
2148 }
2149 return NOTIFY_OK;
2150}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151
Yasunori Goto3218ae12006-06-27 02:53:33 -07002152/*
2153 * This kswapd start function will be called by init and node-hot-add.
2154 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2155 */
2156int kswapd_run(int nid)
2157{
2158 pg_data_t *pgdat = NODE_DATA(nid);
2159 int ret = 0;
2160
2161 if (pgdat->kswapd)
2162 return 0;
2163
2164 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2165 if (IS_ERR(pgdat->kswapd)) {
2166 /* failure at boot is fatal */
2167 BUG_ON(system_state == SYSTEM_BOOTING);
2168 printk("Failed to start kswapd on node %d\n",nid);
2169 ret = -1;
2170 }
2171 return ret;
2172}
2173
Linus Torvalds1da177e2005-04-16 15:20:36 -07002174static int __init kswapd_init(void)
2175{
Yasunori Goto3218ae12006-06-27 02:53:33 -07002176 int nid;
Andrew Morton69e05942006-03-22 00:08:19 -08002177
Linus Torvalds1da177e2005-04-16 15:20:36 -07002178 swap_setup();
Christoph Lameter9422ffb2007-10-16 01:25:31 -07002179 for_each_node_state(nid, N_HIGH_MEMORY)
Yasunori Goto3218ae12006-06-27 02:53:33 -07002180 kswapd_run(nid);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002181 hotcpu_notifier(cpu_callback, 0);
2182 return 0;
2183}
2184
2185module_init(kswapd_init)
Christoph Lameter9eeff232006-01-18 17:42:31 -08002186
2187#ifdef CONFIG_NUMA
2188/*
2189 * Zone reclaim mode
2190 *
2191 * If non-zero call zone_reclaim when the number of free pages falls below
2192 * the watermarks.
Christoph Lameter9eeff232006-01-18 17:42:31 -08002193 */
2194int zone_reclaim_mode __read_mostly;
2195
Christoph Lameter1b2ffb72006-02-01 03:05:34 -08002196#define RECLAIM_OFF 0
Fernando Luis Vazquez Cao7d034312008-07-29 22:33:41 -07002197#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
Christoph Lameter1b2ffb72006-02-01 03:05:34 -08002198#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2199#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2200
Christoph Lameter9eeff232006-01-18 17:42:31 -08002201/*
Christoph Lametera92f7122006-02-01 03:05:32 -08002202 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2203 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2204 * a zone.
2205 */
2206#define ZONE_RECLAIM_PRIORITY 4
2207
Christoph Lameter9eeff232006-01-18 17:42:31 -08002208/*
Christoph Lameter96146342006-07-03 00:24:13 -07002209 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2210 * occur.
2211 */
2212int sysctl_min_unmapped_ratio = 1;
2213
2214/*
Christoph Lameter0ff38492006-09-25 23:31:52 -07002215 * If the number of slab pages in a zone grows beyond this percentage then
2216 * slab reclaim needs to occur.
2217 */
2218int sysctl_min_slab_ratio = 5;
2219
2220/*
Christoph Lameter9eeff232006-01-18 17:42:31 -08002221 * Try to free up some pages from this zone through reclaim.
2222 */
Andrew Morton179e9632006-03-22 00:08:18 -08002223static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
Christoph Lameter9eeff232006-01-18 17:42:31 -08002224{
Christoph Lameter7fb2d462006-03-22 00:08:22 -08002225 /* Minimum pages needed in order to stay on node */
Andrew Morton69e05942006-03-22 00:08:19 -08002226 const unsigned long nr_pages = 1 << order;
Christoph Lameter9eeff232006-01-18 17:42:31 -08002227 struct task_struct *p = current;
2228 struct reclaim_state reclaim_state;
Christoph Lameter86959492006-03-22 00:08:18 -08002229 int priority;
Andrew Morton05ff5132006-03-22 00:08:20 -08002230 unsigned long nr_reclaimed = 0;
Andrew Morton179e9632006-03-22 00:08:18 -08002231 struct scan_control sc = {
2232 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2233 .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
Andrew Morton69e05942006-03-22 00:08:19 -08002234 .swap_cluster_max = max_t(unsigned long, nr_pages,
2235 SWAP_CLUSTER_MAX),
Andrew Morton179e9632006-03-22 00:08:18 -08002236 .gfp_mask = gfp_mask,
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002237 .swappiness = vm_swappiness,
Balbir Singh66e17072008-02-07 00:13:56 -08002238 .isolate_pages = isolate_pages_global,
Andrew Morton179e9632006-03-22 00:08:18 -08002239 };
Christoph Lameter83e33a42006-09-25 23:31:53 -07002240 unsigned long slab_reclaimable;
Christoph Lameter9eeff232006-01-18 17:42:31 -08002241
2242 disable_swap_token();
Christoph Lameter9eeff232006-01-18 17:42:31 -08002243 cond_resched();
Christoph Lameterd4f77962006-02-24 13:04:22 -08002244 /*
2245 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2246 * and we also need to be able to write out pages for RECLAIM_WRITE
2247 * and RECLAIM_SWAP.
2248 */
2249 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
Christoph Lameter9eeff232006-01-18 17:42:31 -08002250 reclaim_state.reclaimed_slab = 0;
2251 p->reclaim_state = &reclaim_state;
Christoph Lameterc84db232006-02-01 03:05:29 -08002252
Christoph Lameter0ff38492006-09-25 23:31:52 -07002253 if (zone_page_state(zone, NR_FILE_PAGES) -
2254 zone_page_state(zone, NR_FILE_MAPPED) >
2255 zone->min_unmapped_pages) {
2256 /*
2257 * Free memory by calling shrink zone with increasing
2258 * priorities until we have enough memory freed.
2259 */
2260 priority = ZONE_RECLAIM_PRIORITY;
2261 do {
Martin Bligh3bb1a8522006-10-28 10:38:24 -07002262 note_zone_scanning_priority(zone, priority);
Christoph Lameter0ff38492006-09-25 23:31:52 -07002263 nr_reclaimed += shrink_zone(priority, zone, &sc);
2264 priority--;
2265 } while (priority >= 0 && nr_reclaimed < nr_pages);
2266 }
Christoph Lameterc84db232006-02-01 03:05:29 -08002267
Christoph Lameter83e33a42006-09-25 23:31:53 -07002268 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2269 if (slab_reclaimable > zone->min_slab_pages) {
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08002270 /*
Christoph Lameter7fb2d462006-03-22 00:08:22 -08002271 * shrink_slab() does not currently allow us to determine how
Christoph Lameter0ff38492006-09-25 23:31:52 -07002272 * many pages were freed in this zone. So we take the current
2273 * number of slab pages and shake the slab until it is reduced
2274 * by the same nr_pages that we used for reclaiming unmapped
2275 * pages.
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08002276 *
Christoph Lameter0ff38492006-09-25 23:31:52 -07002277 * Note that shrink_slab will free memory on all zones and may
2278 * take a long time.
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08002279 */
Christoph Lameter0ff38492006-09-25 23:31:52 -07002280 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
Christoph Lameter83e33a42006-09-25 23:31:53 -07002281 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2282 slab_reclaimable - nr_pages)
Christoph Lameter0ff38492006-09-25 23:31:52 -07002283 ;
Christoph Lameter83e33a42006-09-25 23:31:53 -07002284
2285 /*
2286 * Update nr_reclaimed by the number of slab pages we
2287 * reclaimed from this zone.
2288 */
2289 nr_reclaimed += slab_reclaimable -
2290 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08002291 }
2292
Christoph Lameter9eeff232006-01-18 17:42:31 -08002293 p->reclaim_state = NULL;
Christoph Lameterd4f77962006-02-24 13:04:22 -08002294 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
Andrew Morton05ff5132006-03-22 00:08:20 -08002295 return nr_reclaimed >= nr_pages;
Christoph Lameter9eeff232006-01-18 17:42:31 -08002296}
Andrew Morton179e9632006-03-22 00:08:18 -08002297
2298int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2299{
Andrew Morton179e9632006-03-22 00:08:18 -08002300 int node_id;
David Rientjesd773ed62007-10-16 23:26:01 -07002301 int ret;
Andrew Morton179e9632006-03-22 00:08:18 -08002302
2303 /*
Christoph Lameter0ff38492006-09-25 23:31:52 -07002304 * Zone reclaim reclaims unmapped file backed pages and
2305 * slab pages if we are over the defined limits.
Christoph Lameter34aa1332006-06-30 01:55:37 -07002306 *
Christoph Lameter96146342006-07-03 00:24:13 -07002307 * A small portion of unmapped file backed pages is needed for
2308 * file I/O otherwise pages read by file I/O will be immediately
2309 * thrown out if the zone is overallocated. So we do not reclaim
2310 * if less than a specified percentage of the zone is used by
2311 * unmapped file backed pages.
Andrew Morton179e9632006-03-22 00:08:18 -08002312 */
Christoph Lameter34aa1332006-06-30 01:55:37 -07002313 if (zone_page_state(zone, NR_FILE_PAGES) -
Christoph Lameter0ff38492006-09-25 23:31:52 -07002314 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
2315 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
2316 <= zone->min_slab_pages)
Christoph Lameter96146342006-07-03 00:24:13 -07002317 return 0;
Andrew Morton179e9632006-03-22 00:08:18 -08002318
David Rientjesd773ed62007-10-16 23:26:01 -07002319 if (zone_is_all_unreclaimable(zone))
2320 return 0;
2321
Andrew Morton179e9632006-03-22 00:08:18 -08002322 /*
David Rientjesd773ed62007-10-16 23:26:01 -07002323 * Do not scan if the allocation should not be delayed.
Andrew Morton179e9632006-03-22 00:08:18 -08002324 */
David Rientjesd773ed62007-10-16 23:26:01 -07002325 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
Andrew Morton179e9632006-03-22 00:08:18 -08002326 return 0;
2327
2328 /*
2329 * Only run zone reclaim on the local zone or on zones that do not
2330 * have associated processors. This will favor the local processor
2331 * over remote processors and spread off node memory allocations
2332 * as wide as possible.
2333 */
Christoph Lameter89fa3022006-09-25 23:31:55 -07002334 node_id = zone_to_nid(zone);
Christoph Lameter37c07082007-10-16 01:25:36 -07002335 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
Andrew Morton179e9632006-03-22 00:08:18 -08002336 return 0;
David Rientjesd773ed62007-10-16 23:26:01 -07002337
2338 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2339 return 0;
2340 ret = __zone_reclaim(zone, gfp_mask, order);
2341 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2342
2343 return ret;
Andrew Morton179e9632006-03-22 00:08:18 -08002344}
Christoph Lameter9eeff232006-01-18 17:42:31 -08002345#endif
Lee Schermerhorn894bc312008-10-18 20:26:39 -07002346
2347#ifdef CONFIG_UNEVICTABLE_LRU
2348/*
2349 * page_evictable - test whether a page is evictable
2350 * @page: the page to test
2351 * @vma: the VMA in which the page is or will be mapped, may be NULL
2352 *
2353 * Test whether page is evictable--i.e., should be placed on active/inactive
Nick Pigginb291f002008-10-18 20:26:44 -07002354 * lists vs unevictable list. The vma argument is !NULL when called from the
2355 * fault path to determine how to instantate a new page.
Lee Schermerhorn894bc312008-10-18 20:26:39 -07002356 *
2357 * Reasons page might not be evictable:
Lee Schermerhornba9ddf42008-10-18 20:26:42 -07002358 * (1) page's mapping marked unevictable
Nick Pigginb291f002008-10-18 20:26:44 -07002359 * (2) page is part of an mlocked VMA
Lee Schermerhornba9ddf42008-10-18 20:26:42 -07002360 *
Lee Schermerhorn894bc312008-10-18 20:26:39 -07002361 */
2362int page_evictable(struct page *page, struct vm_area_struct *vma)
2363{
2364
Lee Schermerhornba9ddf42008-10-18 20:26:42 -07002365 if (mapping_unevictable(page_mapping(page)))
2366 return 0;
2367
Nick Pigginb291f002008-10-18 20:26:44 -07002368 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2369 return 0;
Lee Schermerhorn894bc312008-10-18 20:26:39 -07002370
2371 return 1;
2372}
Lee Schermerhorn89e004ea2008-10-18 20:26:43 -07002373
2374/**
2375 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2376 * @page: page to check evictability and move to appropriate lru list
2377 * @zone: zone page is in
2378 *
2379 * Checks a page for evictability and moves the page to the appropriate
2380 * zone lru list.
2381 *
2382 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2383 * have PageUnevictable set.
2384 */
2385static void check_move_unevictable_page(struct page *page, struct zone *zone)
2386{
2387 VM_BUG_ON(PageActive(page));
2388
2389retry:
2390 ClearPageUnevictable(page);
2391 if (page_evictable(page, NULL)) {
2392 enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
Lee Schermerhornaf936a12008-10-18 20:26:53 -07002393
Lee Schermerhorn89e004ea2008-10-18 20:26:43 -07002394 __dec_zone_state(zone, NR_UNEVICTABLE);
2395 list_move(&page->lru, &zone->lru[l].list);
2396 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2397 __count_vm_event(UNEVICTABLE_PGRESCUED);
2398 } else {
2399 /*
2400 * rotate unevictable list
2401 */
2402 SetPageUnevictable(page);
2403 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2404 if (page_evictable(page, NULL))
2405 goto retry;
2406 }
2407}
2408
2409/**
2410 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2411 * @mapping: struct address_space to scan for evictable pages
2412 *
2413 * Scan all pages in mapping. Check unevictable pages for
2414 * evictability and move them to the appropriate zone lru list.
2415 */
2416void scan_mapping_unevictable_pages(struct address_space *mapping)
2417{
2418 pgoff_t next = 0;
2419 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2420 PAGE_CACHE_SHIFT;
2421 struct zone *zone;
2422 struct pagevec pvec;
2423
2424 if (mapping->nrpages == 0)
2425 return;
2426
2427 pagevec_init(&pvec, 0);
2428 while (next < end &&
2429 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2430 int i;
2431 int pg_scanned = 0;
2432
2433 zone = NULL;
2434
2435 for (i = 0; i < pagevec_count(&pvec); i++) {
2436 struct page *page = pvec.pages[i];
2437 pgoff_t page_index = page->index;
2438 struct zone *pagezone = page_zone(page);
2439
2440 pg_scanned++;
2441 if (page_index > next)
2442 next = page_index;
2443 next++;
2444
2445 if (pagezone != zone) {
2446 if (zone)
2447 spin_unlock_irq(&zone->lru_lock);
2448 zone = pagezone;
2449 spin_lock_irq(&zone->lru_lock);
2450 }
2451
2452 if (PageLRU(page) && PageUnevictable(page))
2453 check_move_unevictable_page(page, zone);
2454 }
2455 if (zone)
2456 spin_unlock_irq(&zone->lru_lock);
2457 pagevec_release(&pvec);
2458
2459 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2460 }
2461
2462}
Lee Schermerhornaf936a12008-10-18 20:26:53 -07002463
2464/**
2465 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2466 * @zone - zone of which to scan the unevictable list
2467 *
2468 * Scan @zone's unevictable LRU lists to check for pages that have become
2469 * evictable. Move those that have to @zone's inactive list where they
2470 * become candidates for reclaim, unless shrink_inactive_zone() decides
2471 * to reactivate them. Pages that are still unevictable are rotated
2472 * back onto @zone's unevictable list.
2473 */
2474#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2475void scan_zone_unevictable_pages(struct zone *zone)
2476{
2477 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2478 unsigned long scan;
2479 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2480
2481 while (nr_to_scan > 0) {
2482 unsigned long batch_size = min(nr_to_scan,
2483 SCAN_UNEVICTABLE_BATCH_SIZE);
2484
2485 spin_lock_irq(&zone->lru_lock);
2486 for (scan = 0; scan < batch_size; scan++) {
2487 struct page *page = lru_to_page(l_unevictable);
2488
2489 if (!trylock_page(page))
2490 continue;
2491
2492 prefetchw_prev_lru_page(page, l_unevictable, flags);
2493
2494 if (likely(PageLRU(page) && PageUnevictable(page)))
2495 check_move_unevictable_page(page, zone);
2496
2497 unlock_page(page);
2498 }
2499 spin_unlock_irq(&zone->lru_lock);
2500
2501 nr_to_scan -= batch_size;
2502 }
2503}
2504
2505
2506/**
2507 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2508 *
2509 * A really big hammer: scan all zones' unevictable LRU lists to check for
2510 * pages that have become evictable. Move those back to the zones'
2511 * inactive list where they become candidates for reclaim.
2512 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2513 * and we add swap to the system. As such, it runs in the context of a task
2514 * that has possibly/probably made some previously unevictable pages
2515 * evictable.
2516 */
2517void scan_all_zones_unevictable_pages(void)
2518{
2519 struct zone *zone;
2520
2521 for_each_zone(zone) {
2522 scan_zone_unevictable_pages(zone);
2523 }
2524}
2525
2526/*
2527 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2528 * all nodes' unevictable lists for evictable pages
2529 */
2530unsigned long scan_unevictable_pages;
2531
2532int scan_unevictable_handler(struct ctl_table *table, int write,
2533 struct file *file, void __user *buffer,
2534 size_t *length, loff_t *ppos)
2535{
2536 proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
2537
2538 if (write && *(unsigned long *)table->data)
2539 scan_all_zones_unevictable_pages();
2540
2541 scan_unevictable_pages = 0;
2542 return 0;
2543}
2544
2545/*
2546 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2547 * a specified node's per zone unevictable lists for evictable pages.
2548 */
2549
2550static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2551 struct sysdev_attribute *attr,
2552 char *buf)
2553{
2554 return sprintf(buf, "0\n"); /* always zero; should fit... */
2555}
2556
2557static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2558 struct sysdev_attribute *attr,
2559 const char *buf, size_t count)
2560{
2561 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2562 struct zone *zone;
2563 unsigned long res;
2564 unsigned long req = strict_strtoul(buf, 10, &res);
2565
2566 if (!req)
2567 return 1; /* zero is no-op */
2568
2569 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2570 if (!populated_zone(zone))
2571 continue;
2572 scan_zone_unevictable_pages(zone);
2573 }
2574 return 1;
2575}
2576
2577
2578static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2579 read_scan_unevictable_node,
2580 write_scan_unevictable_node);
2581
2582int scan_unevictable_register_node(struct node *node)
2583{
2584 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2585}
2586
2587void scan_unevictable_unregister_node(struct node *node)
2588{
2589 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
2590}
2591
Lee Schermerhorn894bc312008-10-18 20:26:39 -07002592#endif