blob: a8347b677e74a0e5602766c2d4932e3105129213 [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>
Linus Torvalds1da177e2005-04-16 15:20:36 -070042
43#include <asm/tlbflush.h>
44#include <asm/div64.h>
45
46#include <linux/swapops.h>
47
Nick Piggin0f8053a2006-03-22 00:08:33 -080048#include "internal.h"
49
Linus Torvalds1da177e2005-04-16 15:20:36 -070050struct scan_control {
Linus Torvalds1da177e2005-04-16 15:20:36 -070051 /* Incremented by the number of inactive pages that were scanned */
52 unsigned long nr_scanned;
53
Linus Torvalds1da177e2005-04-16 15:20:36 -070054 /* This context's GFP mask */
Al Viro6daa0e22005-10-21 03:18:50 -040055 gfp_t gfp_mask;
Linus Torvalds1da177e2005-04-16 15:20:36 -070056
57 int may_writepage;
58
Christoph Lameterf1fd1062006-01-18 17:42:30 -080059 /* Can pages be swapped as part of reclaim? */
60 int may_swap;
61
Linus Torvalds1da177e2005-04-16 15:20:36 -070062 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
63 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
64 * In this context, it doesn't matter that we scan the
65 * whole list at once. */
66 int swap_cluster_max;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -070067
68 int swappiness;
Nick Piggin408d8542006-09-25 23:31:27 -070069
70 int all_unreclaimable;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -070071
72 int order;
Balbir Singh66e17072008-02-07 00:13:56 -080073
74 /* Which cgroup do we reclaim from */
75 struct mem_cgroup *mem_cgroup;
76
77 /* Pluggable isolate pages callback */
78 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
79 unsigned long *scanned, int order, int mode,
80 struct zone *z, struct mem_cgroup *mem_cont,
Rik van Riel4f98a2f2008-10-18 20:26:32 -070081 int active, int file);
Linus Torvalds1da177e2005-04-16 15:20:36 -070082};
83
Linus Torvalds1da177e2005-04-16 15:20:36 -070084#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
85
86#ifdef ARCH_HAS_PREFETCH
87#define prefetch_prev_lru_page(_page, _base, _field) \
88 do { \
89 if ((_page)->lru.prev != _base) { \
90 struct page *prev; \
91 \
92 prev = lru_to_page(&(_page->lru)); \
93 prefetch(&prev->_field); \
94 } \
95 } while (0)
96#else
97#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
98#endif
99
100#ifdef ARCH_HAS_PREFETCHW
101#define prefetchw_prev_lru_page(_page, _base, _field) \
102 do { \
103 if ((_page)->lru.prev != _base) { \
104 struct page *prev; \
105 \
106 prev = lru_to_page(&(_page->lru)); \
107 prefetchw(&prev->_field); \
108 } \
109 } while (0)
110#else
111#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
112#endif
113
114/*
115 * From 0 .. 100. Higher means more swappy.
116 */
117int vm_swappiness = 60;
Andrew Mortonbd1e22b2006-06-23 02:03:47 -0700118long vm_total_pages; /* The total number of pages which the VM controls */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119
120static LIST_HEAD(shrinker_list);
121static DECLARE_RWSEM(shrinker_rwsem);
122
Balbir Singh00f0b822008-03-04 14:28:39 -0800123#ifdef CONFIG_CGROUP_MEM_RES_CTLR
KAMEZAWA Hiroyuki91a45472008-02-07 00:14:29 -0800124#define scan_global_lru(sc) (!(sc)->mem_cgroup)
125#else
126#define scan_global_lru(sc) (1)
127#endif
128
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129/*
130 * Add a shrinker callback to be called from the vm
131 */
Rusty Russell8e1f9362007-07-17 04:03:17 -0700132void register_shrinker(struct shrinker *shrinker)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133{
Rusty Russell8e1f9362007-07-17 04:03:17 -0700134 shrinker->nr = 0;
135 down_write(&shrinker_rwsem);
136 list_add_tail(&shrinker->list, &shrinker_list);
137 up_write(&shrinker_rwsem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138}
Rusty Russell8e1f9362007-07-17 04:03:17 -0700139EXPORT_SYMBOL(register_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140
141/*
142 * Remove one
143 */
Rusty Russell8e1f9362007-07-17 04:03:17 -0700144void unregister_shrinker(struct shrinker *shrinker)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145{
146 down_write(&shrinker_rwsem);
147 list_del(&shrinker->list);
148 up_write(&shrinker_rwsem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149}
Rusty Russell8e1f9362007-07-17 04:03:17 -0700150EXPORT_SYMBOL(unregister_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151
152#define SHRINK_BATCH 128
153/*
154 * Call the shrink functions to age shrinkable caches
155 *
156 * Here we assume it costs one seek to replace a lru page and that it also
157 * takes a seek to recreate a cache object. With this in mind we age equal
158 * percentages of the lru and ageable caches. This should balance the seeks
159 * generated by these structures.
160 *
Simon Arlott183ff222007-10-20 01:27:18 +0200161 * If the vm encountered mapped pages on the LRU it increase the pressure on
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162 * slab to avoid swapping.
163 *
164 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
165 *
166 * `lru_pages' represents the number of on-LRU pages in all the zones which
167 * are eligible for the caller's allocation attempt. It is used for balancing
168 * slab reclaim versus page reclaim.
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700169 *
170 * Returns the number of slab objects which we shrunk.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171 */
Andrew Morton69e05942006-03-22 00:08:19 -0800172unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
173 unsigned long lru_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174{
175 struct shrinker *shrinker;
Andrew Morton69e05942006-03-22 00:08:19 -0800176 unsigned long ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177
178 if (scanned == 0)
179 scanned = SWAP_CLUSTER_MAX;
180
181 if (!down_read_trylock(&shrinker_rwsem))
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700182 return 1; /* Assume we'll be able to shrink next time */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183
184 list_for_each_entry(shrinker, &shrinker_list, list) {
185 unsigned long long delta;
186 unsigned long total_scan;
Rusty Russell8e1f9362007-07-17 04:03:17 -0700187 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188
189 delta = (4 * scanned) / shrinker->seeks;
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800190 delta *= max_pass;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191 do_div(delta, lru_pages + 1);
192 shrinker->nr += delta;
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800193 if (shrinker->nr < 0) {
194 printk(KERN_ERR "%s: nr=%ld\n",
Harvey Harrisond40cee22008-04-30 00:55:07 -0700195 __func__, shrinker->nr);
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800196 shrinker->nr = max_pass;
197 }
198
199 /*
200 * Avoid risking looping forever due to too large nr value:
201 * never try to free more than twice the estimate number of
202 * freeable entries.
203 */
204 if (shrinker->nr > max_pass * 2)
205 shrinker->nr = max_pass * 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206
207 total_scan = shrinker->nr;
208 shrinker->nr = 0;
209
210 while (total_scan >= SHRINK_BATCH) {
211 long this_scan = SHRINK_BATCH;
212 int shrink_ret;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700213 int nr_before;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214
Rusty Russell8e1f9362007-07-17 04:03:17 -0700215 nr_before = (*shrinker->shrink)(0, gfp_mask);
216 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700217 if (shrink_ret == -1)
218 break;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700219 if (shrink_ret < nr_before)
220 ret += nr_before - shrink_ret;
Christoph Lameterf8891e52006-06-30 01:55:45 -0700221 count_vm_events(SLABS_SCANNED, this_scan);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222 total_scan -= this_scan;
223
224 cond_resched();
225 }
226
227 shrinker->nr += total_scan;
228 }
229 up_read(&shrinker_rwsem);
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700230 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231}
232
233/* Called without lock on whether page is mapped, so answer is unstable */
234static inline int page_mapping_inuse(struct page *page)
235{
236 struct address_space *mapping;
237
238 /* Page is in somebody's page tables. */
239 if (page_mapped(page))
240 return 1;
241
242 /* Be more reluctant to reclaim swapcache than pagecache */
243 if (PageSwapCache(page))
244 return 1;
245
246 mapping = page_mapping(page);
247 if (!mapping)
248 return 0;
249
250 /* File is mmap'd by somebody? */
251 return mapping_mapped(mapping);
252}
253
254static inline int is_page_cache_freeable(struct page *page)
255{
256 return page_count(page) - !!PagePrivate(page) == 2;
257}
258
259static int may_write_to_queue(struct backing_dev_info *bdi)
260{
Christoph Lameter930d9152006-01-08 01:00:47 -0800261 if (current->flags & PF_SWAPWRITE)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262 return 1;
263 if (!bdi_write_congested(bdi))
264 return 1;
265 if (bdi == current->backing_dev_info)
266 return 1;
267 return 0;
268}
269
270/*
271 * We detected a synchronous write error writing a page out. Probably
272 * -ENOSPC. We need to propagate that into the address_space for a subsequent
273 * fsync(), msync() or close().
274 *
275 * The tricky part is that after writepage we cannot touch the mapping: nothing
276 * prevents it from being freed up. But we have a ref on the page and once
277 * that page is locked, the mapping is pinned.
278 *
279 * We're allowed to run sleeping lock_page() here because we know the caller has
280 * __GFP_FS.
281 */
282static void handle_write_error(struct address_space *mapping,
283 struct page *page, int error)
284{
285 lock_page(page);
Guillaume Chazarain3e9f45b2007-05-08 00:23:25 -0700286 if (page_mapping(page) == mapping)
287 mapping_set_error(mapping, error);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700288 unlock_page(page);
289}
290
Andy Whitcroftc661b072007-08-22 14:01:26 -0700291/* Request for sync pageout. */
292enum pageout_io {
293 PAGEOUT_IO_ASYNC,
294 PAGEOUT_IO_SYNC,
295};
296
Christoph Lameter04e62a22006-06-23 02:03:38 -0700297/* possible outcome of pageout() */
298typedef enum {
299 /* failed to write page out, page is locked */
300 PAGE_KEEP,
301 /* move page to the active list, page is locked */
302 PAGE_ACTIVATE,
303 /* page has been sent to the disk successfully, page is unlocked */
304 PAGE_SUCCESS,
305 /* page is clean and locked */
306 PAGE_CLEAN,
307} pageout_t;
308
Linus Torvalds1da177e2005-04-16 15:20:36 -0700309/*
Andrew Morton1742f192006-03-22 00:08:21 -0800310 * pageout is called by shrink_page_list() for each dirty page.
311 * Calls ->writepage().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312 */
Andy Whitcroftc661b072007-08-22 14:01:26 -0700313static pageout_t pageout(struct page *page, struct address_space *mapping,
314 enum pageout_io sync_writeback)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700315{
316 /*
317 * If the page is dirty, only perform writeback if that write
318 * will be non-blocking. To prevent this allocation from being
319 * stalled by pagecache activity. But note that there may be
320 * stalls if we need to run get_block(). We could test
321 * PagePrivate for that.
322 *
323 * If this process is currently in generic_file_write() against
324 * this page's queue, we can perform writeback even if that
325 * will block.
326 *
327 * If the page is swapcache, write it back even if that would
328 * block, for some throttling. This happens by accident, because
329 * swap_backing_dev_info is bust: it doesn't reflect the
330 * congestion state of the swapdevs. Easy to fix, if needed.
331 * See swapfile.c:page_queue_congested().
332 */
333 if (!is_page_cache_freeable(page))
334 return PAGE_KEEP;
335 if (!mapping) {
336 /*
337 * Some data journaling orphaned pages can have
338 * page->mapping == NULL while being dirty with clean buffers.
339 */
akpm@osdl.org323aca62005-04-16 15:24:06 -0700340 if (PagePrivate(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341 if (try_to_free_buffers(page)) {
342 ClearPageDirty(page);
Harvey Harrisond40cee22008-04-30 00:55:07 -0700343 printk("%s: orphaned page\n", __func__);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344 return PAGE_CLEAN;
345 }
346 }
347 return PAGE_KEEP;
348 }
349 if (mapping->a_ops->writepage == NULL)
350 return PAGE_ACTIVATE;
351 if (!may_write_to_queue(mapping->backing_dev_info))
352 return PAGE_KEEP;
353
354 if (clear_page_dirty_for_io(page)) {
355 int res;
356 struct writeback_control wbc = {
357 .sync_mode = WB_SYNC_NONE,
358 .nr_to_write = SWAP_CLUSTER_MAX,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700359 .range_start = 0,
360 .range_end = LLONG_MAX,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700361 .nonblocking = 1,
362 .for_reclaim = 1,
363 };
364
365 SetPageReclaim(page);
366 res = mapping->a_ops->writepage(page, &wbc);
367 if (res < 0)
368 handle_write_error(mapping, page, res);
Zach Brown994fc28c2005-12-15 14:28:17 -0800369 if (res == AOP_WRITEPAGE_ACTIVATE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700370 ClearPageReclaim(page);
371 return PAGE_ACTIVATE;
372 }
Andy Whitcroftc661b072007-08-22 14:01:26 -0700373
374 /*
375 * Wait on writeback if requested to. This happens when
376 * direct reclaiming a large contiguous area and the
377 * first attempt to free a range of pages fails.
378 */
379 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
380 wait_on_page_writeback(page);
381
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382 if (!PageWriteback(page)) {
383 /* synchronous write or broken a_ops? */
384 ClearPageReclaim(page);
385 }
Andrew Mortone129b5c2006-09-27 01:50:00 -0700386 inc_zone_page_state(page, NR_VMSCAN_WRITE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387 return PAGE_SUCCESS;
388 }
389
390 return PAGE_CLEAN;
391}
392
Andrew Mortona649fd92006-10-17 00:09:36 -0700393/*
Nick Piggine2867812008-07-25 19:45:30 -0700394 * Same as remove_mapping, but if the page is removed from the mapping, it
395 * gets returned with a refcount of 0.
Andrew Mortona649fd92006-10-17 00:09:36 -0700396 */
Nick Piggine2867812008-07-25 19:45:30 -0700397static int __remove_mapping(struct address_space *mapping, struct page *page)
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800398{
Nick Piggin28e4d962006-09-25 23:31:23 -0700399 BUG_ON(!PageLocked(page));
400 BUG_ON(mapping != page_mapping(page));
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800401
Nick Piggin19fd6232008-07-25 19:45:32 -0700402 spin_lock_irq(&mapping->tree_lock);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800403 /*
Nick Piggin0fd0e6b2006-09-27 01:50:02 -0700404 * The non racy check for a busy page.
405 *
406 * Must be careful with the order of the tests. When someone has
407 * a ref to the page, it may be possible that they dirty it then
408 * drop the reference. So if PageDirty is tested before page_count
409 * here, then the following race may occur:
410 *
411 * get_user_pages(&page);
412 * [user mapping goes away]
413 * write_to(page);
414 * !PageDirty(page) [good]
415 * SetPageDirty(page);
416 * put_page(page);
417 * !page_count(page) [good, discard it]
418 *
419 * [oops, our write_to data is lost]
420 *
421 * Reversing the order of the tests ensures such a situation cannot
422 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
423 * load is not satisfied before that of page->_count.
424 *
425 * Note that if SetPageDirty is always performed via set_page_dirty,
426 * and thus under tree_lock, then this ordering is not required.
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800427 */
Nick Piggine2867812008-07-25 19:45:30 -0700428 if (!page_freeze_refs(page, 2))
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800429 goto cannot_free;
Nick Piggine2867812008-07-25 19:45:30 -0700430 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
431 if (unlikely(PageDirty(page))) {
432 page_unfreeze_refs(page, 2);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800433 goto cannot_free;
Nick Piggine2867812008-07-25 19:45:30 -0700434 }
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800435
436 if (PageSwapCache(page)) {
437 swp_entry_t swap = { .val = page_private(page) };
438 __delete_from_swap_cache(page);
Nick Piggin19fd6232008-07-25 19:45:32 -0700439 spin_unlock_irq(&mapping->tree_lock);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800440 swap_free(swap);
Nick Piggine2867812008-07-25 19:45:30 -0700441 } else {
442 __remove_from_page_cache(page);
Nick Piggin19fd6232008-07-25 19:45:32 -0700443 spin_unlock_irq(&mapping->tree_lock);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800444 }
445
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800446 return 1;
447
448cannot_free:
Nick Piggin19fd6232008-07-25 19:45:32 -0700449 spin_unlock_irq(&mapping->tree_lock);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800450 return 0;
451}
452
Linus Torvalds1da177e2005-04-16 15:20:36 -0700453/*
Nick Piggine2867812008-07-25 19:45:30 -0700454 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
455 * someone else has a ref on the page, abort and return 0. If it was
456 * successfully detached, return 1. Assumes the caller has a single ref on
457 * this page.
458 */
459int remove_mapping(struct address_space *mapping, struct page *page)
460{
461 if (__remove_mapping(mapping, page)) {
462 /*
463 * Unfreezing the refcount with 1 rather than 2 effectively
464 * drops the pagecache ref for us without requiring another
465 * atomic operation.
466 */
467 page_unfreeze_refs(page, 1);
468 return 1;
469 }
470 return 0;
471}
472
473/*
Andrew Morton1742f192006-03-22 00:08:21 -0800474 * shrink_page_list() returns the number of reclaimed pages
Linus Torvalds1da177e2005-04-16 15:20:36 -0700475 */
Andrew Morton1742f192006-03-22 00:08:21 -0800476static unsigned long shrink_page_list(struct list_head *page_list,
Andy Whitcroftc661b072007-08-22 14:01:26 -0700477 struct scan_control *sc,
478 enum pageout_io sync_writeback)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700479{
480 LIST_HEAD(ret_pages);
481 struct pagevec freed_pvec;
482 int pgactivate = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -0800483 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700484
485 cond_resched();
486
487 pagevec_init(&freed_pvec, 1);
488 while (!list_empty(page_list)) {
489 struct address_space *mapping;
490 struct page *page;
491 int may_enter_fs;
492 int referenced;
493
494 cond_resched();
495
496 page = lru_to_page(page_list);
497 list_del(&page->lru);
498
Nick Piggin529ae9a2008-08-02 12:01:03 +0200499 if (!trylock_page(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700500 goto keep;
501
Nick Piggin725d7042006-09-25 23:30:55 -0700502 VM_BUG_ON(PageActive(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700503
504 sc->nr_scanned++;
Christoph Lameter80e43422006-02-11 17:55:53 -0800505
506 if (!sc->may_swap && page_mapped(page))
507 goto keep_locked;
508
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509 /* Double the slab pressure for mapped and swapcache pages */
510 if (page_mapped(page) || PageSwapCache(page))
511 sc->nr_scanned++;
512
Andy Whitcroftc661b072007-08-22 14:01:26 -0700513 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
514 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
515
516 if (PageWriteback(page)) {
517 /*
518 * Synchronous reclaim is performed in two passes,
519 * first an asynchronous pass over the list to
520 * start parallel writeback, and a second synchronous
521 * pass to wait for the IO to complete. Wait here
522 * for any page for which writeback has already
523 * started.
524 */
525 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
526 wait_on_page_writeback(page);
Andrew Morton4dd4b922008-03-24 12:29:52 -0700527 else
Andy Whitcroftc661b072007-08-22 14:01:26 -0700528 goto keep_locked;
529 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530
Balbir Singhbed71612008-02-07 00:14:01 -0800531 referenced = page_referenced(page, 1, sc->mem_cgroup);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700532 /* In active use or really unfreeable? Activate it. */
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700533 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
534 referenced && page_mapping_inuse(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700535 goto activate_locked;
536
537#ifdef CONFIG_SWAP
538 /*
539 * Anonymous process memory has backing store?
540 * Try to allocate it some swap space here.
541 */
Christoph Lameter6e5ef1a2006-03-22 00:08:45 -0800542 if (PageAnon(page) && !PageSwapCache(page))
Christoph Lameter1480a542006-01-08 01:00:53 -0800543 if (!add_to_swap(page, GFP_ATOMIC))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700544 goto activate_locked;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545#endif /* CONFIG_SWAP */
546
547 mapping = page_mapping(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700548
549 /*
550 * The page is mapped into the page tables of one or more
551 * processes. Try to unmap it here.
552 */
553 if (page_mapped(page) && mapping) {
Christoph Lametera48d07a2006-02-01 03:05:38 -0800554 switch (try_to_unmap(page, 0)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555 case SWAP_FAIL:
556 goto activate_locked;
557 case SWAP_AGAIN:
558 goto keep_locked;
559 case SWAP_SUCCESS:
560 ; /* try to free the page below */
561 }
562 }
563
564 if (PageDirty(page)) {
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700565 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566 goto keep_locked;
Andrew Morton4dd4b922008-03-24 12:29:52 -0700567 if (!may_enter_fs)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700568 goto keep_locked;
Christoph Lameter52a83632006-02-01 03:05:28 -0800569 if (!sc->may_writepage)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700570 goto keep_locked;
571
572 /* Page is dirty, try to write it out here */
Andy Whitcroftc661b072007-08-22 14:01:26 -0700573 switch (pageout(page, mapping, sync_writeback)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700574 case PAGE_KEEP:
575 goto keep_locked;
576 case PAGE_ACTIVATE:
577 goto activate_locked;
578 case PAGE_SUCCESS:
Andrew Morton4dd4b922008-03-24 12:29:52 -0700579 if (PageWriteback(page) || PageDirty(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580 goto keep;
581 /*
582 * A synchronous write - probably a ramdisk. Go
583 * ahead and try to reclaim the page.
584 */
Nick Piggin529ae9a2008-08-02 12:01:03 +0200585 if (!trylock_page(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700586 goto keep;
587 if (PageDirty(page) || PageWriteback(page))
588 goto keep_locked;
589 mapping = page_mapping(page);
590 case PAGE_CLEAN:
591 ; /* try to free the page below */
592 }
593 }
594
595 /*
596 * If the page has buffers, try to free the buffer mappings
597 * associated with this page. If we succeed we try to free
598 * the page as well.
599 *
600 * We do this even if the page is PageDirty().
601 * try_to_release_page() does not perform I/O, but it is
602 * possible for a page to have PageDirty set, but it is actually
603 * clean (all its buffers are clean). This happens if the
604 * buffers were written out directly, with submit_bh(). ext3
605 * will do this, as well as the blockdev mapping.
606 * try_to_release_page() will discover that cleanness and will
607 * drop the buffers and mark the page clean - it can be freed.
608 *
609 * Rarely, pages can have buffers and no ->mapping. These are
610 * the pages which were not successfully invalidated in
611 * truncate_complete_page(). We try to drop those buffers here
612 * and if that worked, and the page is no longer mapped into
613 * process address space (page_count == 1) it can be freed.
614 * Otherwise, leave the page on the LRU so it is swappable.
615 */
616 if (PagePrivate(page)) {
617 if (!try_to_release_page(page, sc->gfp_mask))
618 goto activate_locked;
Nick Piggine2867812008-07-25 19:45:30 -0700619 if (!mapping && page_count(page) == 1) {
620 unlock_page(page);
621 if (put_page_testzero(page))
622 goto free_it;
623 else {
624 /*
625 * rare race with speculative reference.
626 * the speculative reference will free
627 * this page shortly, so we may
628 * increment nr_reclaimed here (and
629 * leave it off the LRU).
630 */
631 nr_reclaimed++;
632 continue;
633 }
634 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700635 }
636
Nick Piggine2867812008-07-25 19:45:30 -0700637 if (!mapping || !__remove_mapping(mapping, page))
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800638 goto keep_locked;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700639
Linus Torvalds1da177e2005-04-16 15:20:36 -0700640 unlock_page(page);
Nick Piggine2867812008-07-25 19:45:30 -0700641free_it:
Andrew Morton05ff5132006-03-22 00:08:20 -0800642 nr_reclaimed++;
Nick Piggine2867812008-07-25 19:45:30 -0700643 if (!pagevec_add(&freed_pvec, page)) {
644 __pagevec_free(&freed_pvec);
645 pagevec_reinit(&freed_pvec);
646 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700647 continue;
648
649activate_locked:
Rik van Riel68a223942008-10-18 20:26:23 -0700650 /* Not a candidate for swapping, so reclaim swap space. */
651 if (PageSwapCache(page) && vm_swap_full())
652 remove_exclusive_swap_page_ref(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700653 SetPageActive(page);
654 pgactivate++;
655keep_locked:
656 unlock_page(page);
657keep:
658 list_add(&page->lru, &ret_pages);
Nick Piggin725d7042006-09-25 23:30:55 -0700659 VM_BUG_ON(PageLRU(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700660 }
661 list_splice(&ret_pages, page_list);
662 if (pagevec_count(&freed_pvec))
Nick Piggine2867812008-07-25 19:45:30 -0700663 __pagevec_free(&freed_pvec);
Christoph Lameterf8891e52006-06-30 01:55:45 -0700664 count_vm_events(PGACTIVATE, pgactivate);
Andrew Morton05ff5132006-03-22 00:08:20 -0800665 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700666}
667
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700668/* LRU Isolation modes. */
669#define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
670#define ISOLATE_ACTIVE 1 /* Isolate active pages. */
671#define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
672
673/*
674 * Attempt to remove the specified page from its LRU. Only take this page
675 * if it is of the appropriate PageActive status. Pages which are being
676 * freed elsewhere are also ignored.
677 *
678 * page: page to consider
679 * mode: one of the LRU isolation modes defined above
680 *
681 * returns 0 on success, -ve errno on failure.
682 */
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700683int __isolate_lru_page(struct page *page, int mode, int file)
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700684{
685 int ret = -EINVAL;
686
687 /* Only take pages on the LRU. */
688 if (!PageLRU(page))
689 return ret;
690
691 /*
692 * When checking the active state, we need to be sure we are
693 * dealing with comparible boolean values. Take the logical not
694 * of each.
695 */
696 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
697 return ret;
698
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700699 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
700 return ret;
701
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700702 ret = -EBUSY;
703 if (likely(get_page_unless_zero(page))) {
704 /*
705 * Be careful not to clear PageLRU until after we're
706 * sure the page is not being freed elsewhere -- the
707 * page release code relies on it.
708 */
709 ClearPageLRU(page);
710 ret = 0;
711 }
712
713 return ret;
714}
715
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800716/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700717 * zone->lru_lock is heavily contended. Some of the functions that
718 * shrink the lists perform better by taking out a batch of pages
719 * and working on them outside the LRU lock.
720 *
721 * For pagecache intensive workloads, this function is the hottest
722 * spot in the kernel (apart from copy_*_user functions).
723 *
724 * Appropriate locks must be held before calling this function.
725 *
726 * @nr_to_scan: The number of pages to look through on the list.
727 * @src: The LRU list to pull pages off.
728 * @dst: The temp list to put pages on to.
729 * @scanned: The number of pages that were scanned.
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700730 * @order: The caller's attempted allocation order
731 * @mode: One of the LRU isolation modes
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700732 * @file: True [1] if isolating file [!anon] pages
Linus Torvalds1da177e2005-04-16 15:20:36 -0700733 *
734 * returns how many pages were moved onto *@dst.
735 */
Andrew Morton69e05942006-03-22 00:08:19 -0800736static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
737 struct list_head *src, struct list_head *dst,
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700738 unsigned long *scanned, int order, int mode, int file)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700739{
Andrew Morton69e05942006-03-22 00:08:19 -0800740 unsigned long nr_taken = 0;
Wu Fengguangc9b02d92006-03-22 00:08:23 -0800741 unsigned long scan;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700742
Wu Fengguangc9b02d92006-03-22 00:08:23 -0800743 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700744 struct page *page;
745 unsigned long pfn;
746 unsigned long end_pfn;
747 unsigned long page_pfn;
748 int zone_id;
749
Linus Torvalds1da177e2005-04-16 15:20:36 -0700750 page = lru_to_page(src);
751 prefetchw_prev_lru_page(page, src, flags);
752
Nick Piggin725d7042006-09-25 23:30:55 -0700753 VM_BUG_ON(!PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800754
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700755 switch (__isolate_lru_page(page, mode, file)) {
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700756 case 0:
757 list_move(&page->lru, dst);
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800758 nr_taken++;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700759 break;
Nick Piggin46453a62006-03-22 00:07:58 -0800760
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700761 case -EBUSY:
762 /* else it is being freed elsewhere */
763 list_move(&page->lru, src);
764 continue;
765
766 default:
767 BUG();
768 }
769
770 if (!order)
771 continue;
772
773 /*
774 * Attempt to take all pages in the order aligned region
775 * surrounding the tag page. Only take those pages of
776 * the same active state as that tag page. We may safely
777 * round the target page pfn down to the requested order
778 * as the mem_map is guarenteed valid out to MAX_ORDER,
779 * where that page is in a different zone we will detect
780 * it from its zone id and abort this block scan.
781 */
782 zone_id = page_zone_id(page);
783 page_pfn = page_to_pfn(page);
784 pfn = page_pfn & ~((1 << order) - 1);
785 end_pfn = pfn + (1 << order);
786 for (; pfn < end_pfn; pfn++) {
787 struct page *cursor_page;
788
789 /* The target page is in the block, ignore it. */
790 if (unlikely(pfn == page_pfn))
791 continue;
792
793 /* Avoid holes within the zone. */
794 if (unlikely(!pfn_valid_within(pfn)))
795 break;
796
797 cursor_page = pfn_to_page(pfn);
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700798
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700799 /* Check that we have not crossed a zone boundary. */
800 if (unlikely(page_zone_id(cursor_page) != zone_id))
801 continue;
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700802 switch (__isolate_lru_page(cursor_page, mode, file)) {
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700803 case 0:
804 list_move(&cursor_page->lru, dst);
805 nr_taken++;
806 scan++;
807 break;
808
809 case -EBUSY:
810 /* else it is being freed elsewhere */
811 list_move(&cursor_page->lru, src);
812 default:
813 break;
814 }
815 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700816 }
817
818 *scanned = scan;
819 return nr_taken;
820}
821
Balbir Singh66e17072008-02-07 00:13:56 -0800822static unsigned long isolate_pages_global(unsigned long nr,
823 struct list_head *dst,
824 unsigned long *scanned, int order,
825 int mode, struct zone *z,
826 struct mem_cgroup *mem_cont,
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700827 int active, int file)
Balbir Singh66e17072008-02-07 00:13:56 -0800828{
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700829 int lru = LRU_BASE;
Balbir Singh66e17072008-02-07 00:13:56 -0800830 if (active)
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700831 lru += LRU_ACTIVE;
832 if (file)
833 lru += LRU_FILE;
834 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
835 mode, !!file);
Balbir Singh66e17072008-02-07 00:13:56 -0800836}
837
Linus Torvalds1da177e2005-04-16 15:20:36 -0700838/*
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700839 * clear_active_flags() is a helper for shrink_active_list(), clearing
840 * any active bits from the pages in the list.
841 */
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700842static unsigned long clear_active_flags(struct list_head *page_list,
843 unsigned int *count)
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700844{
845 int nr_active = 0;
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700846 int lru;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700847 struct page *page;
848
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700849 list_for_each_entry(page, page_list, lru) {
850 lru = page_is_file_cache(page);
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700851 if (PageActive(page)) {
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700852 lru += LRU_ACTIVE;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700853 ClearPageActive(page);
854 nr_active++;
855 }
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700856 count[lru]++;
857 }
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700858
859 return nr_active;
860}
861
Nick Piggin62695a82008-10-18 20:26:09 -0700862/**
863 * isolate_lru_page - tries to isolate a page from its LRU list
864 * @page: page to isolate from its LRU list
865 *
866 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
867 * vmstat statistic corresponding to whatever LRU list the page was on.
868 *
869 * Returns 0 if the page was removed from an LRU list.
870 * Returns -EBUSY if the page was not on an LRU list.
871 *
872 * The returned page will have PageLRU() cleared. If it was found on
873 * the active list, it will have PageActive set. That flag may need
874 * to be cleared by the caller before letting the page go.
875 *
876 * The vmstat statistic corresponding to the list on which the page was
877 * found will be decremented.
878 *
879 * Restrictions:
880 * (1) Must be called with an elevated refcount on the page. This is a
881 * fundamentnal difference from isolate_lru_pages (which is called
882 * without a stable reference).
883 * (2) the lru_lock must not be held.
884 * (3) interrupts must be enabled.
885 */
886int isolate_lru_page(struct page *page)
887{
888 int ret = -EBUSY;
889
890 if (PageLRU(page)) {
891 struct zone *zone = page_zone(page);
892
893 spin_lock_irq(&zone->lru_lock);
894 if (PageLRU(page) && get_page_unless_zero(page)) {
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700895 int lru = LRU_BASE;
Nick Piggin62695a82008-10-18 20:26:09 -0700896 ret = 0;
897 ClearPageLRU(page);
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700898
899 lru += page_is_file_cache(page) + !!PageActive(page);
900 del_page_from_lru_list(zone, page, lru);
Nick Piggin62695a82008-10-18 20:26:09 -0700901 }
902 spin_unlock_irq(&zone->lru_lock);
903 }
904 return ret;
905}
906
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700907/*
Andrew Morton1742f192006-03-22 00:08:21 -0800908 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
909 * of reclaimed pages
Linus Torvalds1da177e2005-04-16 15:20:36 -0700910 */
Andrew Morton1742f192006-03-22 00:08:21 -0800911static unsigned long shrink_inactive_list(unsigned long max_scan,
Rik van Riel33c120e2008-10-18 20:26:36 -0700912 struct zone *zone, struct scan_control *sc,
913 int priority, int file)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700914{
915 LIST_HEAD(page_list);
916 struct pagevec pvec;
Andrew Morton69e05942006-03-22 00:08:19 -0800917 unsigned long nr_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -0800918 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700919
920 pagevec_init(&pvec, 1);
921
922 lru_add_drain();
923 spin_lock_irq(&zone->lru_lock);
Andrew Morton69e05942006-03-22 00:08:19 -0800924 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700925 struct page *page;
Andrew Morton69e05942006-03-22 00:08:19 -0800926 unsigned long nr_taken;
927 unsigned long nr_scan;
928 unsigned long nr_freed;
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700929 unsigned long nr_active;
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700930 unsigned int count[NR_LRU_LISTS] = { 0, };
Rik van Riel33c120e2008-10-18 20:26:36 -0700931 int mode = ISOLATE_INACTIVE;
932
933 /*
934 * If we need a large contiguous chunk of memory, or have
935 * trouble getting a small set of contiguous pages, we
936 * will reclaim both active and inactive pages.
937 *
938 * We use the same threshold as pageout congestion_wait below.
939 */
940 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
941 mode = ISOLATE_BOTH;
942 else if (sc->order && priority < DEF_PRIORITY - 2)
943 mode = ISOLATE_BOTH;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700944
Balbir Singh66e17072008-02-07 00:13:56 -0800945 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700946 &page_list, &nr_scan, sc->order, mode,
947 zone, sc->mem_cgroup, 0, file);
948 nr_active = clear_active_flags(&page_list, count);
Andy Whitcrofte9187bd2007-08-22 14:01:25 -0700949 __count_vm_events(PGDEACTIVATE, nr_active);
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700950
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700951 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
952 -count[LRU_ACTIVE_FILE]);
953 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
954 -count[LRU_INACTIVE_FILE]);
955 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
956 -count[LRU_ACTIVE_ANON]);
957 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
958 -count[LRU_INACTIVE_ANON]);
959
960 if (scan_global_lru(sc)) {
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -0800961 zone->pages_scanned += nr_scan;
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700962 zone->recent_scanned[0] += count[LRU_INACTIVE_ANON];
963 zone->recent_scanned[0] += count[LRU_ACTIVE_ANON];
964 zone->recent_scanned[1] += count[LRU_INACTIVE_FILE];
965 zone->recent_scanned[1] += count[LRU_ACTIVE_FILE];
966 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700967 spin_unlock_irq(&zone->lru_lock);
968
Andrew Morton69e05942006-03-22 00:08:19 -0800969 nr_scanned += nr_scan;
Andy Whitcroftc661b072007-08-22 14:01:26 -0700970 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
971
972 /*
973 * If we are direct reclaiming for contiguous pages and we do
974 * not reclaim everything in the list, try again and wait
975 * for IO to complete. This will stall high-order allocations
976 * but that should be acceptable to the caller
977 */
978 if (nr_freed < nr_taken && !current_is_kswapd() &&
979 sc->order > PAGE_ALLOC_COSTLY_ORDER) {
980 congestion_wait(WRITE, HZ/10);
981
982 /*
983 * The attempt at page out may have made some
984 * of the pages active, mark them inactive again.
985 */
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700986 nr_active = clear_active_flags(&page_list, count);
Andy Whitcroftc661b072007-08-22 14:01:26 -0700987 count_vm_events(PGDEACTIVATE, nr_active);
988
989 nr_freed += shrink_page_list(&page_list, sc,
990 PAGEOUT_IO_SYNC);
991 }
992
Andrew Morton05ff5132006-03-22 00:08:20 -0800993 nr_reclaimed += nr_freed;
Nick Piggina74609f2006-01-06 00:11:20 -0800994 local_irq_disable();
995 if (current_is_kswapd()) {
Christoph Lameterf8891e52006-06-30 01:55:45 -0700996 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
997 __count_vm_events(KSWAPD_STEAL, nr_freed);
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -0800998 } else if (scan_global_lru(sc))
Christoph Lameterf8891e52006-06-30 01:55:45 -0700999 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001000
Shantanu Goel918d3f92006-12-29 16:48:59 -08001001 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
Nick Piggina74609f2006-01-06 00:11:20 -08001002
Wu Fengguangfb8d14e2006-03-22 00:08:28 -08001003 if (nr_taken == 0)
1004 goto done;
1005
Nick Piggina74609f2006-01-06 00:11:20 -08001006 spin_lock(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001007 /*
1008 * Put back any unfreeable pages.
1009 */
1010 while (!list_empty(&page_list)) {
1011 page = lru_to_page(&page_list);
Nick Piggin725d7042006-09-25 23:30:55 -07001012 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -08001013 SetPageLRU(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014 list_del(&page->lru);
Christoph Lameterb69408e2008-10-18 20:26:14 -07001015 add_page_to_lru_list(zone, page, page_lru(page));
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001016 if (PageActive(page) && scan_global_lru(sc)) {
1017 int file = !!page_is_file_cache(page);
1018 zone->recent_rotated[file]++;
1019 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020 if (!pagevec_add(&pvec, page)) {
1021 spin_unlock_irq(&zone->lru_lock);
1022 __pagevec_release(&pvec);
1023 spin_lock_irq(&zone->lru_lock);
1024 }
1025 }
Andrew Morton69e05942006-03-22 00:08:19 -08001026 } while (nr_scanned < max_scan);
Wu Fengguangfb8d14e2006-03-22 00:08:28 -08001027 spin_unlock(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001028done:
Wu Fengguangfb8d14e2006-03-22 00:08:28 -08001029 local_irq_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030 pagevec_release(&pvec);
Andrew Morton05ff5132006-03-22 00:08:20 -08001031 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001032}
1033
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001034/*
1035 * We are about to scan this zone at a certain priority level. If that priority
1036 * level is smaller (ie: more urgent) than the previous priority, then note
1037 * that priority level within the zone. This is done so that when the next
1038 * process comes in to scan this zone, it will immediately start out at this
1039 * priority level rather than having to build up its own scanning priority.
1040 * Here, this priority affects only the reclaim-mapped threshold.
1041 */
1042static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1043{
1044 if (priority < zone->prev_priority)
1045 zone->prev_priority = priority;
1046}
1047
Nick Piggin4ff1ffb2006-09-25 23:31:28 -07001048static inline int zone_is_near_oom(struct zone *zone)
1049{
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001050 return zone->pages_scanned >= (zone_lru_pages(zone) * 3);
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001051}
1052
1053/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054 * This moves pages from the active list to the inactive list.
1055 *
1056 * We move them the other way if the page is referenced by one or more
1057 * processes, from rmap.
1058 *
1059 * If the pages are mostly unmapped, the processing is fast and it is
1060 * appropriate to hold zone->lru_lock across the whole operation. But if
1061 * the pages are mapped, the processing is slow (page_referenced()) so we
1062 * should drop zone->lru_lock around each page. It's impossible to balance
1063 * this, so instead we remove the pages from the LRU while processing them.
1064 * It is safe to rely on PG_active against the non-LRU pages in here because
1065 * nobody will play with that bit on a non-LRU page.
1066 *
1067 * The downside is that we have to touch page->_count against each page.
1068 * But we had to alter page->flags anyway.
1069 */
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001070
1071
Andrew Morton1742f192006-03-22 00:08:21 -08001072static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001073 struct scan_control *sc, int priority, int file)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001074{
Andrew Morton69e05942006-03-22 00:08:19 -08001075 unsigned long pgmoved;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001076 int pgdeactivate = 0;
Andrew Morton69e05942006-03-22 00:08:19 -08001077 unsigned long pgscanned;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078 LIST_HEAD(l_hold); /* The pages which were snipped off */
Christoph Lameterb69408e2008-10-18 20:26:14 -07001079 LIST_HEAD(l_inactive);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001080 struct page *page;
1081 struct pagevec pvec;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001082 enum lru_list lru;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001083
1084 lru_add_drain();
1085 spin_lock_irq(&zone->lru_lock);
Balbir Singh66e17072008-02-07 00:13:56 -08001086 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1087 ISOLATE_ACTIVE, zone,
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001088 sc->mem_cgroup, 1, file);
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001089 /*
1090 * zone->pages_scanned is used for detect zone's oom
1091 * mem_cgroup remembers nr_scan by itself.
1092 */
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001093 if (scan_global_lru(sc)) {
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001094 zone->pages_scanned += pgscanned;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001095 zone->recent_scanned[!!file] += pgmoved;
1096 }
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001097
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001098 if (file)
1099 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1100 else
1101 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001102 spin_unlock_irq(&zone->lru_lock);
1103
Rik van Riel556adec2008-10-18 20:26:34 -07001104 pgmoved = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001105 while (!list_empty(&l_hold)) {
1106 cond_resched();
1107 page = lru_to_page(&l_hold);
1108 list_del(&page->lru);
Rik van Riel7e9cd482008-10-18 20:26:35 -07001109
1110 /* page_referenced clears PageReferenced */
1111 if (page_mapping_inuse(page) &&
1112 page_referenced(page, 0, sc->mem_cgroup))
1113 pgmoved++;
1114
Linus Torvalds1da177e2005-04-16 15:20:36 -07001115 list_add(&page->lru, &l_inactive);
1116 }
1117
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001118 /*
Rik van Riel7e9cd482008-10-18 20:26:35 -07001119 * Count referenced pages from currently used mappings as
1120 * rotated, even though they are moved to the inactive list.
1121 * This helps balance scan pressure between file and anonymous
1122 * pages in get_scan_ratio.
1123 */
Rik van Riel556adec2008-10-18 20:26:34 -07001124 zone->recent_rotated[!!file] += pgmoved;
1125
1126 /*
Rik van Riel7e9cd482008-10-18 20:26:35 -07001127 * Move the pages to the [file or anon] inactive list.
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001128 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001129 pagevec_init(&pvec, 1);
Rik van Riel7e9cd482008-10-18 20:26:35 -07001130
Linus Torvalds1da177e2005-04-16 15:20:36 -07001131 pgmoved = 0;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001132 lru = LRU_BASE + file * LRU_FILE;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001133 spin_lock_irq(&zone->lru_lock);
1134 while (!list_empty(&l_inactive)) {
1135 page = lru_to_page(&l_inactive);
1136 prefetchw_prev_lru_page(page, &l_inactive, flags);
Nick Piggin725d7042006-09-25 23:30:55 -07001137 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -08001138 SetPageLRU(page);
Nick Piggin725d7042006-09-25 23:30:55 -07001139 VM_BUG_ON(!PageActive(page));
Nick Piggin4c84cac2006-03-22 00:08:00 -08001140 ClearPageActive(page);
1141
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001142 list_move(&page->lru, &zone->lru[lru].list);
Hugh Dickins427d5412008-03-04 14:29:03 -08001143 mem_cgroup_move_lists(page, false);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001144 pgmoved++;
1145 if (!pagevec_add(&pvec, page)) {
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001146 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001147 spin_unlock_irq(&zone->lru_lock);
1148 pgdeactivate += pgmoved;
1149 pgmoved = 0;
1150 if (buffer_heads_over_limit)
1151 pagevec_strip(&pvec);
1152 __pagevec_release(&pvec);
1153 spin_lock_irq(&zone->lru_lock);
1154 }
1155 }
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001156 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001157 pgdeactivate += pgmoved;
1158 if (buffer_heads_over_limit) {
1159 spin_unlock_irq(&zone->lru_lock);
1160 pagevec_strip(&pvec);
1161 spin_lock_irq(&zone->lru_lock);
1162 }
Christoph Lameterf8891e52006-06-30 01:55:45 -07001163 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1164 __count_vm_events(PGDEACTIVATE, pgdeactivate);
1165 spin_unlock_irq(&zone->lru_lock);
Rik van Riel68a223942008-10-18 20:26:23 -07001166 if (vm_swap_full())
1167 pagevec_swap_free(&pvec);
Nick Piggina74609f2006-01-06 00:11:20 -08001168
1169 pagevec_release(&pvec);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001170}
1171
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001172static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
Christoph Lameterb69408e2008-10-18 20:26:14 -07001173 struct zone *zone, struct scan_control *sc, int priority)
1174{
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001175 int file = is_file_lru(lru);
1176
Rik van Riel556adec2008-10-18 20:26:34 -07001177 if (lru == LRU_ACTIVE_FILE) {
1178 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1179 return 0;
1180 }
1181
1182 if (lru == LRU_ACTIVE_ANON &&
1183 (!scan_global_lru(sc) || inactive_anon_is_low(zone))) {
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001184 shrink_active_list(nr_to_scan, zone, sc, priority, file);
Christoph Lameterb69408e2008-10-18 20:26:14 -07001185 return 0;
1186 }
Rik van Riel33c120e2008-10-18 20:26:36 -07001187 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
Christoph Lameterb69408e2008-10-18 20:26:14 -07001188}
1189
Linus Torvalds1da177e2005-04-16 15:20:36 -07001190/*
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001191 * Determine how aggressively the anon and file LRU lists should be
1192 * scanned. The relative value of each set of LRU lists is determined
1193 * by looking at the fraction of the pages scanned we did rotate back
1194 * onto the active list instead of evict.
1195 *
1196 * percent[0] specifies how much pressure to put on ram/swap backed
1197 * memory, while percent[1] determines pressure on the file LRUs.
1198 */
1199static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1200 unsigned long *percent)
1201{
1202 unsigned long anon, file, free;
1203 unsigned long anon_prio, file_prio;
1204 unsigned long ap, fp;
1205
1206 anon = zone_page_state(zone, NR_ACTIVE_ANON) +
1207 zone_page_state(zone, NR_INACTIVE_ANON);
1208 file = zone_page_state(zone, NR_ACTIVE_FILE) +
1209 zone_page_state(zone, NR_INACTIVE_FILE);
1210 free = zone_page_state(zone, NR_FREE_PAGES);
1211
1212 /* If we have no swap space, do not bother scanning anon pages. */
1213 if (nr_swap_pages <= 0) {
1214 percent[0] = 0;
1215 percent[1] = 100;
1216 return;
1217 }
1218
1219 /* If we have very few page cache pages, force-scan anon pages. */
1220 if (unlikely(file + free <= zone->pages_high)) {
1221 percent[0] = 100;
1222 percent[1] = 0;
1223 return;
1224 }
1225
1226 /*
1227 * OK, so we have swap space and a fair amount of page cache
1228 * pages. We use the recently rotated / recently scanned
1229 * ratios to determine how valuable each cache is.
1230 *
1231 * Because workloads change over time (and to avoid overflow)
1232 * we keep these statistics as a floating average, which ends
1233 * up weighing recent references more than old ones.
1234 *
1235 * anon in [0], file in [1]
1236 */
1237 if (unlikely(zone->recent_scanned[0] > anon / 4)) {
1238 spin_lock_irq(&zone->lru_lock);
1239 zone->recent_scanned[0] /= 2;
1240 zone->recent_rotated[0] /= 2;
1241 spin_unlock_irq(&zone->lru_lock);
1242 }
1243
1244 if (unlikely(zone->recent_scanned[1] > file / 4)) {
1245 spin_lock_irq(&zone->lru_lock);
1246 zone->recent_scanned[1] /= 2;
1247 zone->recent_rotated[1] /= 2;
1248 spin_unlock_irq(&zone->lru_lock);
1249 }
1250
1251 /*
1252 * With swappiness at 100, anonymous and file have the same priority.
1253 * This scanning priority is essentially the inverse of IO cost.
1254 */
1255 anon_prio = sc->swappiness;
1256 file_prio = 200 - sc->swappiness;
1257
1258 /*
1259 * anon recent_rotated[0]
1260 * %anon = 100 * ----------- / ----------------- * IO cost
1261 * anon + file rotate_sum
1262 */
1263 ap = (anon_prio + 1) * (zone->recent_scanned[0] + 1);
1264 ap /= zone->recent_rotated[0] + 1;
1265
1266 fp = (file_prio + 1) * (zone->recent_scanned[1] + 1);
1267 fp /= zone->recent_rotated[1] + 1;
1268
1269 /* Normalize to percentages */
1270 percent[0] = 100 * ap / (ap + fp + 1);
1271 percent[1] = 100 - percent[0];
1272}
1273
1274
1275/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001276 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1277 */
Andrew Morton05ff5132006-03-22 00:08:20 -08001278static unsigned long shrink_zone(int priority, struct zone *zone,
1279 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001280{
Christoph Lameterb69408e2008-10-18 20:26:14 -07001281 unsigned long nr[NR_LRU_LISTS];
Christoph Lameter86959492006-03-22 00:08:18 -08001282 unsigned long nr_to_scan;
Andrew Morton05ff5132006-03-22 00:08:20 -08001283 unsigned long nr_reclaimed = 0;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001284 unsigned long percent[2]; /* anon @ 0; file @ 1 */
Christoph Lameterb69408e2008-10-18 20:26:14 -07001285 enum lru_list l;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001286
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001287 get_scan_ratio(zone, sc, percent);
1288
1289 for_each_lru(l) {
1290 if (scan_global_lru(sc)) {
1291 int file = is_file_lru(l);
1292 int scan;
1293 /*
1294 * Add one to nr_to_scan just to make sure that the
1295 * kernel will slowly sift through each list.
1296 */
1297 scan = zone_page_state(zone, NR_LRU_BASE + l);
1298 if (priority) {
1299 scan >>= priority;
1300 scan = (scan * percent[file]) / 100;
1301 }
1302 zone->lru[l].nr_scan += scan + 1;
Christoph Lameterb69408e2008-10-18 20:26:14 -07001303 nr[l] = zone->lru[l].nr_scan;
1304 if (nr[l] >= sc->swap_cluster_max)
1305 zone->lru[l].nr_scan = 0;
1306 else
1307 nr[l] = 0;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001308 } else {
1309 /*
1310 * This reclaim occurs not because zone memory shortage
1311 * but because memory controller hits its limit.
1312 * Don't modify zone reclaim related data.
1313 */
1314 nr[l] = mem_cgroup_calc_reclaim(sc->mem_cgroup, zone,
1315 priority, l);
Christoph Lameterb69408e2008-10-18 20:26:14 -07001316 }
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001317 }
1318
Rik van Riel556adec2008-10-18 20:26:34 -07001319 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1320 nr[LRU_INACTIVE_FILE]) {
Christoph Lameterb69408e2008-10-18 20:26:14 -07001321 for_each_lru(l) {
1322 if (nr[l]) {
1323 nr_to_scan = min(nr[l],
Linus Torvalds1da177e2005-04-16 15:20:36 -07001324 (unsigned long)sc->swap_cluster_max);
Christoph Lameterb69408e2008-10-18 20:26:14 -07001325 nr[l] -= nr_to_scan;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001326
Christoph Lameterb69408e2008-10-18 20:26:14 -07001327 nr_reclaimed += shrink_list(l, nr_to_scan,
1328 zone, sc, priority);
1329 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001330 }
1331 }
1332
Rik van Riel556adec2008-10-18 20:26:34 -07001333 /*
1334 * Even if we did not try to evict anon pages at all, we want to
1335 * rebalance the anon lru active/inactive ratio.
1336 */
1337 if (!scan_global_lru(sc) || inactive_anon_is_low(zone))
1338 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1339 else if (!scan_global_lru(sc))
1340 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1341
Andrew Morton232ea4d2007-02-28 20:13:21 -08001342 throttle_vm_writeout(sc->gfp_mask);
Andrew Morton05ff5132006-03-22 00:08:20 -08001343 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344}
1345
1346/*
1347 * This is the direct reclaim path, for page-allocating processes. We only
1348 * try to reclaim pages from zones which will satisfy the caller's allocation
1349 * request.
1350 *
1351 * We reclaim from a zone even if that zone is over pages_high. Because:
1352 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1353 * allocation or
1354 * b) The zones may be over pages_high but they must go *over* pages_high to
1355 * satisfy the `incremental min' zone defense algorithm.
1356 *
1357 * Returns the number of reclaimed pages.
1358 *
1359 * If a zone is deemed to be full of pinned pages then just give it a light
1360 * scan then give up on it.
1361 */
Mel Gormandac1d272008-04-28 02:12:12 -07001362static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
Andrew Morton05ff5132006-03-22 00:08:20 -08001363 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001364{
Mel Gorman54a6eb52008-04-28 02:12:16 -07001365 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
Andrew Morton05ff5132006-03-22 00:08:20 -08001366 unsigned long nr_reclaimed = 0;
Mel Gormandd1a2392008-04-28 02:12:17 -07001367 struct zoneref *z;
Mel Gorman54a6eb52008-04-28 02:12:16 -07001368 struct zone *zone;
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001369
Nick Piggin408d8542006-09-25 23:31:27 -07001370 sc->all_unreclaimable = 1;
Mel Gorman54a6eb52008-04-28 02:12:16 -07001371 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
Con Kolivasf3fe6512006-01-06 00:11:15 -08001372 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001373 continue;
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001374 /*
1375 * Take care memory controller reclaiming has small influence
1376 * to global LRU.
1377 */
1378 if (scan_global_lru(sc)) {
1379 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1380 continue;
1381 note_zone_scanning_priority(zone, priority);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001382
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001383 if (zone_is_all_unreclaimable(zone) &&
1384 priority != DEF_PRIORITY)
1385 continue; /* Let kswapd poll it */
1386 sc->all_unreclaimable = 0;
1387 } else {
1388 /*
1389 * Ignore cpuset limitation here. We just want to reduce
1390 * # of used pages by us regardless of memory shortage.
1391 */
1392 sc->all_unreclaimable = 0;
1393 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1394 priority);
1395 }
Nick Piggin408d8542006-09-25 23:31:27 -07001396
Andrew Morton05ff5132006-03-22 00:08:20 -08001397 nr_reclaimed += shrink_zone(priority, zone, sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001398 }
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001399
Andrew Morton05ff5132006-03-22 00:08:20 -08001400 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001401}
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001402
Linus Torvalds1da177e2005-04-16 15:20:36 -07001403/*
1404 * This is the main entry point to direct page reclaim.
1405 *
1406 * If a full scan of the inactive list fails to free enough memory then we
1407 * are "out of memory" and something needs to be killed.
1408 *
1409 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1410 * high - the zone may be full of dirty or under-writeback pages, which this
1411 * caller can't do much about. We kick pdflush and take explicit naps in the
1412 * hope that some of these pages can be written. But if the allocating task
1413 * holds filesystem locks which prevent writeout this might not work, and the
1414 * allocation attempt will fail.
Nishanth Aravamudana41f24e2008-04-29 00:58:25 -07001415 *
1416 * returns: 0, if no pages reclaimed
1417 * else, the number of pages reclaimed
Linus Torvalds1da177e2005-04-16 15:20:36 -07001418 */
Mel Gormandac1d272008-04-28 02:12:12 -07001419static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
Mel Gormandd1a2392008-04-28 02:12:17 -07001420 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421{
1422 int priority;
kosaki.motohiro@jp.fujitsu.comc700be32008-06-12 15:21:27 -07001423 unsigned long ret = 0;
Andrew Morton69e05942006-03-22 00:08:19 -08001424 unsigned long total_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -08001425 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001426 struct reclaim_state *reclaim_state = current->reclaim_state;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001427 unsigned long lru_pages = 0;
Mel Gormandd1a2392008-04-28 02:12:17 -07001428 struct zoneref *z;
Mel Gorman54a6eb52008-04-28 02:12:16 -07001429 struct zone *zone;
Mel Gormandd1a2392008-04-28 02:12:17 -07001430 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001431
Keika Kobayashi873b4772008-07-25 01:48:52 -07001432 delayacct_freepages_start();
1433
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001434 if (scan_global_lru(sc))
1435 count_vm_event(ALLOCSTALL);
1436 /*
1437 * mem_cgroup will not do shrink_slab.
1438 */
1439 if (scan_global_lru(sc)) {
Mel Gorman54a6eb52008-04-28 02:12:16 -07001440 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001441
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001442 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1443 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001444
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001445 lru_pages += zone_lru_pages(zone);
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001446 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001447 }
1448
1449 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
Balbir Singh66e17072008-02-07 00:13:56 -08001450 sc->nr_scanned = 0;
Rik van Rielf7b7fd82005-11-28 13:44:07 -08001451 if (!priority)
1452 disable_swap_token();
Mel Gormandac1d272008-04-28 02:12:12 -07001453 nr_reclaimed += shrink_zones(priority, zonelist, sc);
Balbir Singh66e17072008-02-07 00:13:56 -08001454 /*
1455 * Don't shrink slabs when reclaiming memory from
1456 * over limit cgroups
1457 */
KAMEZAWA Hiroyuki91a45472008-02-07 00:14:29 -08001458 if (scan_global_lru(sc)) {
Mel Gormandd1a2392008-04-28 02:12:17 -07001459 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
KAMEZAWA Hiroyuki91a45472008-02-07 00:14:29 -08001460 if (reclaim_state) {
1461 nr_reclaimed += reclaim_state->reclaimed_slab;
1462 reclaim_state->reclaimed_slab = 0;
1463 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464 }
Balbir Singh66e17072008-02-07 00:13:56 -08001465 total_scanned += sc->nr_scanned;
1466 if (nr_reclaimed >= sc->swap_cluster_max) {
Nishanth Aravamudana41f24e2008-04-29 00:58:25 -07001467 ret = nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001468 goto out;
1469 }
1470
1471 /*
1472 * Try to write back as many pages as we just scanned. This
1473 * tends to cause slow streaming writers to write data to the
1474 * disk smoothly, at the dirtying rate, which is nice. But
1475 * that's undesirable in laptop mode, where we *want* lumpy
1476 * writeout. So in laptop mode, write out the whole world.
1477 */
Balbir Singh66e17072008-02-07 00:13:56 -08001478 if (total_scanned > sc->swap_cluster_max +
1479 sc->swap_cluster_max / 2) {
Pekka J Enberg687a21c2005-06-28 20:44:55 -07001480 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
Balbir Singh66e17072008-02-07 00:13:56 -08001481 sc->may_writepage = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001482 }
1483
1484 /* Take a nap, wait for some writeback to complete */
Andrew Morton4dd4b922008-03-24 12:29:52 -07001485 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
Andrew Morton3fcfab12006-10-19 23:28:16 -07001486 congestion_wait(WRITE, HZ/10);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001487 }
Fernando Luis Vazquez Cao87547ee2008-07-29 22:33:42 -07001488 /* top priority shrink_zones still had more to do? don't OOM, then */
KAMEZAWA Hiroyuki91a45472008-02-07 00:14:29 -08001489 if (!sc->all_unreclaimable && scan_global_lru(sc))
Nishanth Aravamudana41f24e2008-04-29 00:58:25 -07001490 ret = nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001491out:
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001492 /*
1493 * Now that we've scanned all the zones at this priority level, note
1494 * that level within the zone so that the next thread which performs
1495 * scanning of this zone will immediately start out at this priority
1496 * level. This affects only the decision whether or not to bring
1497 * mapped pages onto the inactive list.
1498 */
1499 if (priority < 0)
1500 priority = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001501
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001502 if (scan_global_lru(sc)) {
Mel Gorman54a6eb52008-04-28 02:12:16 -07001503 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001504
KAMEZAWA Hiroyuki1cfb4192008-02-07 00:14:37 -08001505 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1506 continue;
1507
1508 zone->prev_priority = priority;
1509 }
1510 } else
1511 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1512
Keika Kobayashi873b4772008-07-25 01:48:52 -07001513 delayacct_freepages_end();
1514
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515 return ret;
1516}
1517
Mel Gormandac1d272008-04-28 02:12:12 -07001518unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1519 gfp_t gfp_mask)
Balbir Singh66e17072008-02-07 00:13:56 -08001520{
1521 struct scan_control sc = {
1522 .gfp_mask = gfp_mask,
1523 .may_writepage = !laptop_mode,
1524 .swap_cluster_max = SWAP_CLUSTER_MAX,
1525 .may_swap = 1,
1526 .swappiness = vm_swappiness,
1527 .order = order,
1528 .mem_cgroup = NULL,
1529 .isolate_pages = isolate_pages_global,
1530 };
1531
Mel Gormandd1a2392008-04-28 02:12:17 -07001532 return do_try_to_free_pages(zonelist, &sc);
Balbir Singh66e17072008-02-07 00:13:56 -08001533}
1534
Balbir Singh00f0b822008-03-04 14:28:39 -08001535#ifdef CONFIG_CGROUP_MEM_RES_CTLR
Balbir Singh66e17072008-02-07 00:13:56 -08001536
Balbir Singhe1a1cd52008-02-07 00:14:02 -08001537unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1538 gfp_t gfp_mask)
Balbir Singh66e17072008-02-07 00:13:56 -08001539{
1540 struct scan_control sc = {
Balbir Singh66e17072008-02-07 00:13:56 -08001541 .may_writepage = !laptop_mode,
1542 .may_swap = 1,
1543 .swap_cluster_max = SWAP_CLUSTER_MAX,
1544 .swappiness = vm_swappiness,
1545 .order = 0,
1546 .mem_cgroup = mem_cont,
1547 .isolate_pages = mem_cgroup_isolate_pages,
1548 };
Mel Gormandac1d272008-04-28 02:12:12 -07001549 struct zonelist *zonelist;
Balbir Singh66e17072008-02-07 00:13:56 -08001550
Mel Gormandd1a2392008-04-28 02:12:17 -07001551 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1552 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1553 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1554 return do_try_to_free_pages(zonelist, &sc);
Balbir Singh66e17072008-02-07 00:13:56 -08001555}
1556#endif
1557
Linus Torvalds1da177e2005-04-16 15:20:36 -07001558/*
1559 * For kswapd, balance_pgdat() will work across all this node's zones until
1560 * they are all at pages_high.
1561 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001562 * Returns the number of pages which were actually freed.
1563 *
1564 * There is special handling here for zones which are full of pinned pages.
1565 * This can happen if the pages are all mlocked, or if they are all used by
1566 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1567 * What we do is to detect the case where all pages in the zone have been
1568 * scanned twice and there has been zero successful reclaim. Mark the zone as
1569 * dead and from now on, only perform a short scan. Basically we're polling
1570 * the zone for when the problem goes away.
1571 *
1572 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1573 * zones which have free_pages > pages_high, but once a zone is found to have
1574 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1575 * of the number of free pages in the lower zones. This interoperates with
1576 * the page allocator fallback scheme to ensure that aging of pages is balanced
1577 * across the zones.
1578 */
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001579static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001580{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001581 int all_zones_ok;
1582 int priority;
1583 int i;
Andrew Morton69e05942006-03-22 00:08:19 -08001584 unsigned long total_scanned;
Andrew Morton05ff5132006-03-22 00:08:20 -08001585 unsigned long nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001586 struct reclaim_state *reclaim_state = current->reclaim_state;
Andrew Morton179e9632006-03-22 00:08:18 -08001587 struct scan_control sc = {
1588 .gfp_mask = GFP_KERNEL,
1589 .may_swap = 1,
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001590 .swap_cluster_max = SWAP_CLUSTER_MAX,
1591 .swappiness = vm_swappiness,
Andy Whitcroft5ad333e2007-07-17 04:03:16 -07001592 .order = order,
Balbir Singh66e17072008-02-07 00:13:56 -08001593 .mem_cgroup = NULL,
1594 .isolate_pages = isolate_pages_global,
Andrew Morton179e9632006-03-22 00:08:18 -08001595 };
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001596 /*
1597 * temp_priority is used to remember the scanning priority at which
1598 * this zone was successfully refilled to free_pages == pages_high.
1599 */
1600 int temp_priority[MAX_NR_ZONES];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001601
1602loop_again:
1603 total_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -08001604 nr_reclaimed = 0;
Christoph Lameterc0bbbc72006-06-11 15:22:26 -07001605 sc.may_writepage = !laptop_mode;
Christoph Lameterf8891e52006-06-30 01:55:45 -07001606 count_vm_event(PAGEOUTRUN);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001607
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001608 for (i = 0; i < pgdat->nr_zones; i++)
1609 temp_priority[i] = DEF_PRIORITY;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001610
1611 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1612 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1613 unsigned long lru_pages = 0;
1614
Rik van Rielf7b7fd82005-11-28 13:44:07 -08001615 /* The swap token gets in the way of swapout... */
1616 if (!priority)
1617 disable_swap_token();
1618
Linus Torvalds1da177e2005-04-16 15:20:36 -07001619 all_zones_ok = 1;
1620
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001621 /*
1622 * Scan in the highmem->dma direction for the highest
1623 * zone which needs scanning
1624 */
1625 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1626 struct zone *zone = pgdat->node_zones + i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001627
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001628 if (!populated_zone(zone))
1629 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001630
David Rientjese815af92007-10-16 23:25:54 -07001631 if (zone_is_all_unreclaimable(zone) &&
1632 priority != DEF_PRIORITY)
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001633 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001634
Rik van Riel556adec2008-10-18 20:26:34 -07001635 /*
1636 * Do some background aging of the anon list, to give
1637 * pages a chance to be referenced before reclaiming.
1638 */
1639 if (inactive_anon_is_low(zone))
1640 shrink_active_list(SWAP_CLUSTER_MAX, zone,
1641 &sc, priority, 0);
1642
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001643 if (!zone_watermark_ok(zone, order, zone->pages_high,
1644 0, 0)) {
1645 end_zone = i;
Andrew Mortone1dbeda2006-12-06 20:32:01 -08001646 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001647 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001648 }
Andrew Mortone1dbeda2006-12-06 20:32:01 -08001649 if (i < 0)
1650 goto out;
1651
Linus Torvalds1da177e2005-04-16 15:20:36 -07001652 for (i = 0; i <= end_zone; i++) {
1653 struct zone *zone = pgdat->node_zones + i;
1654
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001655 lru_pages += zone_lru_pages(zone);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001656 }
1657
1658 /*
1659 * Now scan the zone in the dma->highmem direction, stopping
1660 * at the last zone which needs scanning.
1661 *
1662 * We do this because the page allocator works in the opposite
1663 * direction. This prevents the page allocator from allocating
1664 * pages behind kswapd's direction of progress, which would
1665 * cause too much scanning of the lower zones.
1666 */
1667 for (i = 0; i <= end_zone; i++) {
1668 struct zone *zone = pgdat->node_zones + i;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001669 int nr_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001670
Con Kolivasf3fe6512006-01-06 00:11:15 -08001671 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001672 continue;
1673
David Rientjese815af92007-10-16 23:25:54 -07001674 if (zone_is_all_unreclaimable(zone) &&
1675 priority != DEF_PRIORITY)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001676 continue;
1677
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001678 if (!zone_watermark_ok(zone, order, zone->pages_high,
1679 end_zone, 0))
1680 all_zones_ok = 0;
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001681 temp_priority[i] = priority;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001682 sc.nr_scanned = 0;
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001683 note_zone_scanning_priority(zone, priority);
Rik van Riel32a43302007-10-16 01:24:50 -07001684 /*
1685 * We put equal pressure on every zone, unless one
1686 * zone has way too many pages free already.
1687 */
1688 if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
1689 end_zone, 0))
1690 nr_reclaimed += shrink_zone(priority, zone, &sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001691 reclaim_state->reclaimed_slab = 0;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001692 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1693 lru_pages);
Andrew Morton05ff5132006-03-22 00:08:20 -08001694 nr_reclaimed += reclaim_state->reclaimed_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001695 total_scanned += sc.nr_scanned;
David Rientjese815af92007-10-16 23:25:54 -07001696 if (zone_is_all_unreclaimable(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001697 continue;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001698 if (nr_slab == 0 && zone->pages_scanned >=
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001699 (zone_lru_pages(zone) * 6))
David Rientjese815af92007-10-16 23:25:54 -07001700 zone_set_flag(zone,
1701 ZONE_ALL_UNRECLAIMABLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001702 /*
1703 * If we've done a decent amount of scanning and
1704 * the reclaim ratio is low, start doing writepage
1705 * even in laptop mode
1706 */
1707 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
Andrew Morton05ff5132006-03-22 00:08:20 -08001708 total_scanned > nr_reclaimed + nr_reclaimed / 2)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001709 sc.may_writepage = 1;
1710 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001711 if (all_zones_ok)
1712 break; /* kswapd: all done */
1713 /*
1714 * OK, kswapd is getting into trouble. Take a nap, then take
1715 * another pass across the zones.
1716 */
Andrew Morton4dd4b922008-03-24 12:29:52 -07001717 if (total_scanned && priority < DEF_PRIORITY - 2)
Andrew Morton3fcfab12006-10-19 23:28:16 -07001718 congestion_wait(WRITE, HZ/10);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001719
1720 /*
1721 * We do this so kswapd doesn't build up large priorities for
1722 * example when it is freeing in parallel with allocators. It
1723 * matches the direct reclaim path behaviour in terms of impact
1724 * on zone->*_priority.
1725 */
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001726 if (nr_reclaimed >= SWAP_CLUSTER_MAX)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001727 break;
1728 }
1729out:
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001730 /*
1731 * Note within each zone the priority level at which this zone was
1732 * brought into a happy state. So that the next thread which scans this
1733 * zone will start out at that priority level.
1734 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001735 for (i = 0; i < pgdat->nr_zones; i++) {
1736 struct zone *zone = pgdat->node_zones + i;
1737
Martin Bligh3bb1a8522006-10-28 10:38:24 -07001738 zone->prev_priority = temp_priority[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001739 }
1740 if (!all_zones_ok) {
1741 cond_resched();
Rafael J. Wysocki83573762006-12-06 20:34:18 -08001742
1743 try_to_freeze();
1744
Linus Torvalds1da177e2005-04-16 15:20:36 -07001745 goto loop_again;
1746 }
1747
Andrew Morton05ff5132006-03-22 00:08:20 -08001748 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001749}
1750
1751/*
1752 * The background pageout daemon, started as a kernel thread
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001753 * from the init process.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001754 *
1755 * This basically trickles out pages so that we have _some_
1756 * free memory available even if there is no other activity
1757 * that frees anything up. This is needed for things like routing
1758 * etc, where we otherwise might have all activity going on in
1759 * asynchronous contexts that cannot page things out.
1760 *
1761 * If there are applications that are active memory-allocators
1762 * (most normal use), this basically shouldn't matter.
1763 */
1764static int kswapd(void *p)
1765{
1766 unsigned long order;
1767 pg_data_t *pgdat = (pg_data_t*)p;
1768 struct task_struct *tsk = current;
1769 DEFINE_WAIT(wait);
1770 struct reclaim_state reclaim_state = {
1771 .reclaimed_slab = 0,
1772 };
Mike Travisc5f59f02008-04-04 18:11:10 -07001773 node_to_cpumask_ptr(cpumask, pgdat->node_id);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001774
Mike Travisc5f59f02008-04-04 18:11:10 -07001775 if (!cpus_empty(*cpumask))
1776 set_cpus_allowed_ptr(tsk, cpumask);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001777 current->reclaim_state = &reclaim_state;
1778
1779 /*
1780 * Tell the memory management that we're a "memory allocator",
1781 * and that if we need more memory we should get access to it
1782 * regardless (see "__alloc_pages()"). "kswapd" should
1783 * never get caught in the normal page freeing logic.
1784 *
1785 * (Kswapd normally doesn't need memory anyway, but sometimes
1786 * you need a small amount of memory in order to be able to
1787 * page out something else, and this flag essentially protects
1788 * us from recursively trying to free more memory as we're
1789 * trying to free the first piece of memory in the first place).
1790 */
Christoph Lameter930d9152006-01-08 01:00:47 -08001791 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
Rafael J. Wysocki83144182007-07-17 04:03:35 -07001792 set_freezable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001793
1794 order = 0;
1795 for ( ; ; ) {
1796 unsigned long new_order;
Christoph Lameter3e1d1d22005-06-24 23:13:50 -07001797
Linus Torvalds1da177e2005-04-16 15:20:36 -07001798 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1799 new_order = pgdat->kswapd_max_order;
1800 pgdat->kswapd_max_order = 0;
1801 if (order < new_order) {
1802 /*
1803 * Don't sleep if someone wants a larger 'order'
1804 * allocation
1805 */
1806 order = new_order;
1807 } else {
Rafael J. Wysockib1296cc2007-05-06 14:50:48 -07001808 if (!freezing(current))
1809 schedule();
1810
Linus Torvalds1da177e2005-04-16 15:20:36 -07001811 order = pgdat->kswapd_max_order;
1812 }
1813 finish_wait(&pgdat->kswapd_wait, &wait);
1814
Rafael J. Wysockib1296cc2007-05-06 14:50:48 -07001815 if (!try_to_freeze()) {
1816 /* We can speed up thawing tasks if we don't call
1817 * balance_pgdat after returning from the refrigerator
1818 */
1819 balance_pgdat(pgdat, order);
1820 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001821 }
1822 return 0;
1823}
1824
1825/*
1826 * A zone is low on free memory, so wake its kswapd task to service it.
1827 */
1828void wakeup_kswapd(struct zone *zone, int order)
1829{
1830 pg_data_t *pgdat;
1831
Con Kolivasf3fe6512006-01-06 00:11:15 -08001832 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001833 return;
1834
1835 pgdat = zone->zone_pgdat;
Rohit Seth7fb1d9f2005-11-13 16:06:43 -08001836 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001837 return;
1838 if (pgdat->kswapd_max_order < order)
1839 pgdat->kswapd_max_order = order;
Paul Jackson02a0e532006-12-13 00:34:25 -08001840 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001841 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001842 if (!waitqueue_active(&pgdat->kswapd_wait))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001843 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001844 wake_up_interruptible(&pgdat->kswapd_wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845}
1846
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001847unsigned long global_lru_pages(void)
1848{
1849 return global_page_state(NR_ACTIVE_ANON)
1850 + global_page_state(NR_ACTIVE_FILE)
1851 + global_page_state(NR_INACTIVE_ANON)
1852 + global_page_state(NR_INACTIVE_FILE);
1853}
1854
Linus Torvalds1da177e2005-04-16 15:20:36 -07001855#ifdef CONFIG_PM
1856/*
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001857 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1858 * from LRU lists system-wide, for given pass and priority, and returns the
1859 * number of reclaimed pages
1860 *
1861 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1862 */
Nigel Cunninghame07aa052006-12-22 01:07:21 -08001863static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
1864 int pass, struct scan_control *sc)
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001865{
1866 struct zone *zone;
1867 unsigned long nr_to_scan, ret = 0;
Christoph Lameterb69408e2008-10-18 20:26:14 -07001868 enum lru_list l;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001869
1870 for_each_zone(zone) {
1871
1872 if (!populated_zone(zone))
1873 continue;
1874
David Rientjese815af92007-10-16 23:25:54 -07001875 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001876 continue;
1877
Christoph Lameterb69408e2008-10-18 20:26:14 -07001878 for_each_lru(l) {
1879 /* For pass = 0 we don't shrink the active list */
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001880 if (pass == 0 &&
1881 (l == LRU_ACTIVE || l == LRU_ACTIVE_FILE))
Christoph Lameterb69408e2008-10-18 20:26:14 -07001882 continue;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001883
Christoph Lameterb69408e2008-10-18 20:26:14 -07001884 zone->lru[l].nr_scan +=
1885 (zone_page_state(zone, NR_LRU_BASE + l)
1886 >> prio) + 1;
1887 if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
1888 zone->lru[l].nr_scan = 0;
1889 nr_to_scan = min(nr_pages,
1890 zone_page_state(zone,
1891 NR_LRU_BASE + l));
1892 ret += shrink_list(l, nr_to_scan, zone,
1893 sc, prio);
1894 if (ret >= nr_pages)
1895 return ret;
1896 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001897 }
1898 }
1899
1900 return ret;
1901}
1902
1903/*
1904 * Try to free `nr_pages' of memory, system-wide, and return the number of
1905 * freed pages.
1906 *
1907 * Rather than trying to age LRUs the aim is to preserve the overall
1908 * LRU order by reclaiming preferentially
1909 * inactive > active > active referenced > active mapped
Linus Torvalds1da177e2005-04-16 15:20:36 -07001910 */
Andrew Morton69e05942006-03-22 00:08:19 -08001911unsigned long shrink_all_memory(unsigned long nr_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001912{
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001913 unsigned long lru_pages, nr_slab;
Andrew Morton69e05942006-03-22 00:08:19 -08001914 unsigned long ret = 0;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001915 int pass;
1916 struct reclaim_state reclaim_state;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001917 struct scan_control sc = {
1918 .gfp_mask = GFP_KERNEL,
1919 .may_swap = 0,
1920 .swap_cluster_max = nr_pages,
1921 .may_writepage = 1,
1922 .swappiness = vm_swappiness,
Balbir Singh66e17072008-02-07 00:13:56 -08001923 .isolate_pages = isolate_pages_global,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001924 };
1925
1926 current->reclaim_state = &reclaim_state;
Andrew Morton69e05942006-03-22 00:08:19 -08001927
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001928 lru_pages = global_lru_pages();
Christoph Lameter972d1a72006-09-25 23:31:51 -07001929 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001930 /* If slab caches are huge, it's better to hit them first */
1931 while (nr_slab >= lru_pages) {
1932 reclaim_state.reclaimed_slab = 0;
1933 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
1934 if (!reclaim_state.reclaimed_slab)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001935 break;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001936
1937 ret += reclaim_state.reclaimed_slab;
1938 if (ret >= nr_pages)
1939 goto out;
1940
1941 nr_slab -= reclaim_state.reclaimed_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001942 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001943
1944 /*
1945 * We try to shrink LRUs in 5 passes:
1946 * 0 = Reclaim from inactive_list only
1947 * 1 = Reclaim from active list but don't reclaim mapped
1948 * 2 = 2nd pass of type 1
1949 * 3 = Reclaim mapped (normal reclaim)
1950 * 4 = 2nd pass of type 3
1951 */
1952 for (pass = 0; pass < 5; pass++) {
1953 int prio;
1954
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001955 /* Force reclaiming mapped pages in the passes #3 and #4 */
1956 if (pass > 2) {
1957 sc.may_swap = 1;
1958 sc.swappiness = 100;
1959 }
1960
1961 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
1962 unsigned long nr_to_scan = nr_pages - ret;
1963
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001964 sc.nr_scanned = 0;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001965 ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
1966 if (ret >= nr_pages)
1967 goto out;
1968
1969 reclaim_state.reclaimed_slab = 0;
Andrew Morton76395d32007-01-05 16:37:05 -08001970 shrink_slab(sc.nr_scanned, sc.gfp_mask,
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001971 global_lru_pages());
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001972 ret += reclaim_state.reclaimed_slab;
1973 if (ret >= nr_pages)
1974 goto out;
1975
1976 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
Andrew Morton3fcfab12006-10-19 23:28:16 -07001977 congestion_wait(WRITE, HZ / 10);
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001978 }
Rafael J. Wysocki248a0302006-03-22 00:09:04 -08001979 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001980
1981 /*
1982 * If ret = 0, we could not shrink LRUs, but there may be something
1983 * in slab caches
1984 */
Andrew Morton76395d32007-01-05 16:37:05 -08001985 if (!ret) {
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001986 do {
1987 reclaim_state.reclaimed_slab = 0;
Rik van Riel4f98a2f2008-10-18 20:26:32 -07001988 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001989 ret += reclaim_state.reclaimed_slab;
1990 } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
Andrew Morton76395d32007-01-05 16:37:05 -08001991 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001992
1993out:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001994 current->reclaim_state = NULL;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001995
Linus Torvalds1da177e2005-04-16 15:20:36 -07001996 return ret;
1997}
1998#endif
1999
Linus Torvalds1da177e2005-04-16 15:20:36 -07002000/* It's optimal to keep kswapds on the same CPUs as their memory, but
2001 not required for correctness. So if the last cpu in a node goes
2002 away, we get changed to run anywhere: as the first one comes back,
2003 restore their cpu bindings. */
Chandra Seetharaman9c7b2162006-06-27 02:54:07 -07002004static int __devinit cpu_callback(struct notifier_block *nfb,
Andrew Morton69e05942006-03-22 00:08:19 -08002005 unsigned long action, void *hcpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002006{
Yasunori Goto58c0a4a2007-10-16 01:25:40 -07002007 int nid;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002008
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07002009 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
Yasunori Goto58c0a4a2007-10-16 01:25:40 -07002010 for_each_node_state(nid, N_HIGH_MEMORY) {
Mike Travisc5f59f02008-04-04 18:11:10 -07002011 pg_data_t *pgdat = NODE_DATA(nid);
2012 node_to_cpumask_ptr(mask, pgdat->node_id);
2013
2014 if (any_online_cpu(*mask) < nr_cpu_ids)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002015 /* One of our CPUs online: restore mask */
Mike Travisc5f59f02008-04-04 18:11:10 -07002016 set_cpus_allowed_ptr(pgdat->kswapd, mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002017 }
2018 }
2019 return NOTIFY_OK;
2020}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002021
Yasunori Goto3218ae12006-06-27 02:53:33 -07002022/*
2023 * This kswapd start function will be called by init and node-hot-add.
2024 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2025 */
2026int kswapd_run(int nid)
2027{
2028 pg_data_t *pgdat = NODE_DATA(nid);
2029 int ret = 0;
2030
2031 if (pgdat->kswapd)
2032 return 0;
2033
2034 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2035 if (IS_ERR(pgdat->kswapd)) {
2036 /* failure at boot is fatal */
2037 BUG_ON(system_state == SYSTEM_BOOTING);
2038 printk("Failed to start kswapd on node %d\n",nid);
2039 ret = -1;
2040 }
2041 return ret;
2042}
2043
Linus Torvalds1da177e2005-04-16 15:20:36 -07002044static int __init kswapd_init(void)
2045{
Yasunori Goto3218ae12006-06-27 02:53:33 -07002046 int nid;
Andrew Morton69e05942006-03-22 00:08:19 -08002047
Linus Torvalds1da177e2005-04-16 15:20:36 -07002048 swap_setup();
Christoph Lameter9422ffb2007-10-16 01:25:31 -07002049 for_each_node_state(nid, N_HIGH_MEMORY)
Yasunori Goto3218ae12006-06-27 02:53:33 -07002050 kswapd_run(nid);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002051 hotcpu_notifier(cpu_callback, 0);
2052 return 0;
2053}
2054
2055module_init(kswapd_init)
Christoph Lameter9eeff232006-01-18 17:42:31 -08002056
2057#ifdef CONFIG_NUMA
2058/*
2059 * Zone reclaim mode
2060 *
2061 * If non-zero call zone_reclaim when the number of free pages falls below
2062 * the watermarks.
Christoph Lameter9eeff232006-01-18 17:42:31 -08002063 */
2064int zone_reclaim_mode __read_mostly;
2065
Christoph Lameter1b2ffb72006-02-01 03:05:34 -08002066#define RECLAIM_OFF 0
Fernando Luis Vazquez Cao7d034312008-07-29 22:33:41 -07002067#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
Christoph Lameter1b2ffb72006-02-01 03:05:34 -08002068#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2069#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2070
Christoph Lameter9eeff232006-01-18 17:42:31 -08002071/*
Christoph Lametera92f7122006-02-01 03:05:32 -08002072 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2073 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2074 * a zone.
2075 */
2076#define ZONE_RECLAIM_PRIORITY 4
2077
Christoph Lameter9eeff232006-01-18 17:42:31 -08002078/*
Christoph Lameter96146342006-07-03 00:24:13 -07002079 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2080 * occur.
2081 */
2082int sysctl_min_unmapped_ratio = 1;
2083
2084/*
Christoph Lameter0ff38492006-09-25 23:31:52 -07002085 * If the number of slab pages in a zone grows beyond this percentage then
2086 * slab reclaim needs to occur.
2087 */
2088int sysctl_min_slab_ratio = 5;
2089
2090/*
Christoph Lameter9eeff232006-01-18 17:42:31 -08002091 * Try to free up some pages from this zone through reclaim.
2092 */
Andrew Morton179e9632006-03-22 00:08:18 -08002093static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
Christoph Lameter9eeff232006-01-18 17:42:31 -08002094{
Christoph Lameter7fb2d462006-03-22 00:08:22 -08002095 /* Minimum pages needed in order to stay on node */
Andrew Morton69e05942006-03-22 00:08:19 -08002096 const unsigned long nr_pages = 1 << order;
Christoph Lameter9eeff232006-01-18 17:42:31 -08002097 struct task_struct *p = current;
2098 struct reclaim_state reclaim_state;
Christoph Lameter86959492006-03-22 00:08:18 -08002099 int priority;
Andrew Morton05ff5132006-03-22 00:08:20 -08002100 unsigned long nr_reclaimed = 0;
Andrew Morton179e9632006-03-22 00:08:18 -08002101 struct scan_control sc = {
2102 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2103 .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
Andrew Morton69e05942006-03-22 00:08:19 -08002104 .swap_cluster_max = max_t(unsigned long, nr_pages,
2105 SWAP_CLUSTER_MAX),
Andrew Morton179e9632006-03-22 00:08:18 -08002106 .gfp_mask = gfp_mask,
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07002107 .swappiness = vm_swappiness,
Balbir Singh66e17072008-02-07 00:13:56 -08002108 .isolate_pages = isolate_pages_global,
Andrew Morton179e9632006-03-22 00:08:18 -08002109 };
Christoph Lameter83e33a42006-09-25 23:31:53 -07002110 unsigned long slab_reclaimable;
Christoph Lameter9eeff232006-01-18 17:42:31 -08002111
2112 disable_swap_token();
Christoph Lameter9eeff232006-01-18 17:42:31 -08002113 cond_resched();
Christoph Lameterd4f77962006-02-24 13:04:22 -08002114 /*
2115 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2116 * and we also need to be able to write out pages for RECLAIM_WRITE
2117 * and RECLAIM_SWAP.
2118 */
2119 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
Christoph Lameter9eeff232006-01-18 17:42:31 -08002120 reclaim_state.reclaimed_slab = 0;
2121 p->reclaim_state = &reclaim_state;
Christoph Lameterc84db232006-02-01 03:05:29 -08002122
Christoph Lameter0ff38492006-09-25 23:31:52 -07002123 if (zone_page_state(zone, NR_FILE_PAGES) -
2124 zone_page_state(zone, NR_FILE_MAPPED) >
2125 zone->min_unmapped_pages) {
2126 /*
2127 * Free memory by calling shrink zone with increasing
2128 * priorities until we have enough memory freed.
2129 */
2130 priority = ZONE_RECLAIM_PRIORITY;
2131 do {
Martin Bligh3bb1a8522006-10-28 10:38:24 -07002132 note_zone_scanning_priority(zone, priority);
Christoph Lameter0ff38492006-09-25 23:31:52 -07002133 nr_reclaimed += shrink_zone(priority, zone, &sc);
2134 priority--;
2135 } while (priority >= 0 && nr_reclaimed < nr_pages);
2136 }
Christoph Lameterc84db232006-02-01 03:05:29 -08002137
Christoph Lameter83e33a42006-09-25 23:31:53 -07002138 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2139 if (slab_reclaimable > zone->min_slab_pages) {
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08002140 /*
Christoph Lameter7fb2d462006-03-22 00:08:22 -08002141 * shrink_slab() does not currently allow us to determine how
Christoph Lameter0ff38492006-09-25 23:31:52 -07002142 * many pages were freed in this zone. So we take the current
2143 * number of slab pages and shake the slab until it is reduced
2144 * by the same nr_pages that we used for reclaiming unmapped
2145 * pages.
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08002146 *
Christoph Lameter0ff38492006-09-25 23:31:52 -07002147 * Note that shrink_slab will free memory on all zones and may
2148 * take a long time.
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08002149 */
Christoph Lameter0ff38492006-09-25 23:31:52 -07002150 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
Christoph Lameter83e33a42006-09-25 23:31:53 -07002151 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2152 slab_reclaimable - nr_pages)
Christoph Lameter0ff38492006-09-25 23:31:52 -07002153 ;
Christoph Lameter83e33a42006-09-25 23:31:53 -07002154
2155 /*
2156 * Update nr_reclaimed by the number of slab pages we
2157 * reclaimed from this zone.
2158 */
2159 nr_reclaimed += slab_reclaimable -
2160 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08002161 }
2162
Christoph Lameter9eeff232006-01-18 17:42:31 -08002163 p->reclaim_state = NULL;
Christoph Lameterd4f77962006-02-24 13:04:22 -08002164 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
Andrew Morton05ff5132006-03-22 00:08:20 -08002165 return nr_reclaimed >= nr_pages;
Christoph Lameter9eeff232006-01-18 17:42:31 -08002166}
Andrew Morton179e9632006-03-22 00:08:18 -08002167
2168int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2169{
Andrew Morton179e9632006-03-22 00:08:18 -08002170 int node_id;
David Rientjesd773ed62007-10-16 23:26:01 -07002171 int ret;
Andrew Morton179e9632006-03-22 00:08:18 -08002172
2173 /*
Christoph Lameter0ff38492006-09-25 23:31:52 -07002174 * Zone reclaim reclaims unmapped file backed pages and
2175 * slab pages if we are over the defined limits.
Christoph Lameter34aa1332006-06-30 01:55:37 -07002176 *
Christoph Lameter96146342006-07-03 00:24:13 -07002177 * A small portion of unmapped file backed pages is needed for
2178 * file I/O otherwise pages read by file I/O will be immediately
2179 * thrown out if the zone is overallocated. So we do not reclaim
2180 * if less than a specified percentage of the zone is used by
2181 * unmapped file backed pages.
Andrew Morton179e9632006-03-22 00:08:18 -08002182 */
Christoph Lameter34aa1332006-06-30 01:55:37 -07002183 if (zone_page_state(zone, NR_FILE_PAGES) -
Christoph Lameter0ff38492006-09-25 23:31:52 -07002184 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
2185 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
2186 <= zone->min_slab_pages)
Christoph Lameter96146342006-07-03 00:24:13 -07002187 return 0;
Andrew Morton179e9632006-03-22 00:08:18 -08002188
David Rientjesd773ed62007-10-16 23:26:01 -07002189 if (zone_is_all_unreclaimable(zone))
2190 return 0;
2191
Andrew Morton179e9632006-03-22 00:08:18 -08002192 /*
David Rientjesd773ed62007-10-16 23:26:01 -07002193 * Do not scan if the allocation should not be delayed.
Andrew Morton179e9632006-03-22 00:08:18 -08002194 */
David Rientjesd773ed62007-10-16 23:26:01 -07002195 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
Andrew Morton179e9632006-03-22 00:08:18 -08002196 return 0;
2197
2198 /*
2199 * Only run zone reclaim on the local zone or on zones that do not
2200 * have associated processors. This will favor the local processor
2201 * over remote processors and spread off node memory allocations
2202 * as wide as possible.
2203 */
Christoph Lameter89fa3022006-09-25 23:31:55 -07002204 node_id = zone_to_nid(zone);
Christoph Lameter37c07082007-10-16 01:25:36 -07002205 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
Andrew Morton179e9632006-03-22 00:08:18 -08002206 return 0;
David Rientjesd773ed62007-10-16 23:26:01 -07002207
2208 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2209 return 0;
2210 ret = __zone_reclaim(zone, gfp_mask, order);
2211 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2212
2213 return ret;
Andrew Morton179e9632006-03-22 00:08:18 -08002214}
Christoph Lameter9eeff232006-01-18 17:42:31 -08002215#endif