blob: 518540a4a2a66a1ade20312d1d655ba6923e05b5 [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>
Linus Torvalds1da177e2005-04-16 15:20:36 -070039
40#include <asm/tlbflush.h>
41#include <asm/div64.h>
42
43#include <linux/swapops.h>
44
Nick Piggin0f8053a2006-03-22 00:08:33 -080045#include "internal.h"
46
Linus Torvalds1da177e2005-04-16 15:20:36 -070047struct scan_control {
Linus Torvalds1da177e2005-04-16 15:20:36 -070048 /* Incremented by the number of inactive pages that were scanned */
49 unsigned long nr_scanned;
50
Linus Torvalds1da177e2005-04-16 15:20:36 -070051 /* This context's GFP mask */
Al Viro6daa0e22005-10-21 03:18:50 -040052 gfp_t gfp_mask;
Linus Torvalds1da177e2005-04-16 15:20:36 -070053
54 int may_writepage;
55
Christoph Lameterf1fd1062006-01-18 17:42:30 -080056 /* Can pages be swapped as part of reclaim? */
57 int may_swap;
58
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
60 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
61 * In this context, it doesn't matter that we scan the
62 * whole list at once. */
63 int swap_cluster_max;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -070064
65 int swappiness;
Nick Piggin408d8542006-09-25 23:31:27 -070066
67 int all_unreclaimable;
Linus Torvalds1da177e2005-04-16 15:20:36 -070068};
69
70/*
71 * The list of shrinker callbacks used by to apply pressure to
72 * ageable caches.
73 */
74struct shrinker {
75 shrinker_t shrinker;
76 struct list_head list;
77 int seeks; /* seeks to recreate an obj */
78 long nr; /* objs pending delete */
79};
80
81#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
82
83#ifdef ARCH_HAS_PREFETCH
84#define prefetch_prev_lru_page(_page, _base, _field) \
85 do { \
86 if ((_page)->lru.prev != _base) { \
87 struct page *prev; \
88 \
89 prev = lru_to_page(&(_page->lru)); \
90 prefetch(&prev->_field); \
91 } \
92 } while (0)
93#else
94#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
95#endif
96
97#ifdef ARCH_HAS_PREFETCHW
98#define prefetchw_prev_lru_page(_page, _base, _field) \
99 do { \
100 if ((_page)->lru.prev != _base) { \
101 struct page *prev; \
102 \
103 prev = lru_to_page(&(_page->lru)); \
104 prefetchw(&prev->_field); \
105 } \
106 } while (0)
107#else
108#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
109#endif
110
111/*
112 * From 0 .. 100. Higher means more swappy.
113 */
114int vm_swappiness = 60;
Andrew Mortonbd1e22b2006-06-23 02:03:47 -0700115long vm_total_pages; /* The total number of pages which the VM controls */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116
117static LIST_HEAD(shrinker_list);
118static DECLARE_RWSEM(shrinker_rwsem);
119
120/*
121 * Add a shrinker callback to be called from the vm
122 */
123struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker)
124{
125 struct shrinker *shrinker;
126
127 shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL);
128 if (shrinker) {
129 shrinker->shrinker = theshrinker;
130 shrinker->seeks = seeks;
131 shrinker->nr = 0;
132 down_write(&shrinker_rwsem);
133 list_add_tail(&shrinker->list, &shrinker_list);
134 up_write(&shrinker_rwsem);
135 }
136 return shrinker;
137}
138EXPORT_SYMBOL(set_shrinker);
139
140/*
141 * Remove one
142 */
143void remove_shrinker(struct shrinker *shrinker)
144{
145 down_write(&shrinker_rwsem);
146 list_del(&shrinker->list);
147 up_write(&shrinker_rwsem);
148 kfree(shrinker);
149}
150EXPORT_SYMBOL(remove_shrinker);
151
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 *
161 * If the vm encounted mapped pages on the LRU it increase the pressure on
162 * 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;
Andrea Arcangeliea164d72005-11-28 13:44:15 -0800187 unsigned long max_pass = (*shrinker->shrinker)(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",
195 __FUNCTION__, shrinker->nr);
196 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
akpm@osdl.orgb15e0902005-06-21 17:14:35 -0700215 nr_before = (*shrinker->shrinker)(0, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216 shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask);
217 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);
286 if (page_mapping(page) == mapping) {
287 if (error == -ENOSPC)
288 set_bit(AS_ENOSPC, &mapping->flags);
289 else
290 set_bit(AS_EIO, &mapping->flags);
291 }
292 unlock_page(page);
293}
294
Christoph Lameter04e62a22006-06-23 02:03:38 -0700295/* possible outcome of pageout() */
296typedef enum {
297 /* failed to write page out, page is locked */
298 PAGE_KEEP,
299 /* move page to the active list, page is locked */
300 PAGE_ACTIVATE,
301 /* page has been sent to the disk successfully, page is unlocked */
302 PAGE_SUCCESS,
303 /* page is clean and locked */
304 PAGE_CLEAN,
305} pageout_t;
306
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307/*
Andrew Morton1742f192006-03-22 00:08:21 -0800308 * pageout is called by shrink_page_list() for each dirty page.
309 * Calls ->writepage().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310 */
Christoph Lameter04e62a22006-06-23 02:03:38 -0700311static pageout_t pageout(struct page *page, struct address_space *mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312{
313 /*
314 * If the page is dirty, only perform writeback if that write
315 * will be non-blocking. To prevent this allocation from being
316 * stalled by pagecache activity. But note that there may be
317 * stalls if we need to run get_block(). We could test
318 * PagePrivate for that.
319 *
320 * If this process is currently in generic_file_write() against
321 * this page's queue, we can perform writeback even if that
322 * will block.
323 *
324 * If the page is swapcache, write it back even if that would
325 * block, for some throttling. This happens by accident, because
326 * swap_backing_dev_info is bust: it doesn't reflect the
327 * congestion state of the swapdevs. Easy to fix, if needed.
328 * See swapfile.c:page_queue_congested().
329 */
330 if (!is_page_cache_freeable(page))
331 return PAGE_KEEP;
332 if (!mapping) {
333 /*
334 * Some data journaling orphaned pages can have
335 * page->mapping == NULL while being dirty with clean buffers.
336 */
akpm@osdl.org323aca62005-04-16 15:24:06 -0700337 if (PagePrivate(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338 if (try_to_free_buffers(page)) {
339 ClearPageDirty(page);
340 printk("%s: orphaned page\n", __FUNCTION__);
341 return PAGE_CLEAN;
342 }
343 }
344 return PAGE_KEEP;
345 }
346 if (mapping->a_ops->writepage == NULL)
347 return PAGE_ACTIVATE;
348 if (!may_write_to_queue(mapping->backing_dev_info))
349 return PAGE_KEEP;
350
351 if (clear_page_dirty_for_io(page)) {
352 int res;
353 struct writeback_control wbc = {
354 .sync_mode = WB_SYNC_NONE,
355 .nr_to_write = SWAP_CLUSTER_MAX,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700356 .range_start = 0,
357 .range_end = LLONG_MAX,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358 .nonblocking = 1,
359 .for_reclaim = 1,
360 };
361
362 SetPageReclaim(page);
363 res = mapping->a_ops->writepage(page, &wbc);
364 if (res < 0)
365 handle_write_error(mapping, page, res);
Zach Brown994fc28c2005-12-15 14:28:17 -0800366 if (res == AOP_WRITEPAGE_ACTIVATE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 ClearPageReclaim(page);
368 return PAGE_ACTIVATE;
369 }
370 if (!PageWriteback(page)) {
371 /* synchronous write or broken a_ops? */
372 ClearPageReclaim(page);
373 }
Andrew Mortone129b5c2006-09-27 01:50:00 -0700374 inc_zone_page_state(page, NR_VMSCAN_WRITE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375 return PAGE_SUCCESS;
376 }
377
378 return PAGE_CLEAN;
379}
380
Andrew Mortona649fd92006-10-17 00:09:36 -0700381/*
382 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
383 * someone else has a ref on the page, abort and return 0. If it was
384 * successfully detached, return 1. Assumes the caller has a single ref on
385 * this page.
386 */
Christoph Lameterb20a3502006-03-22 00:09:12 -0800387int remove_mapping(struct address_space *mapping, struct page *page)
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800388{
Nick Piggin28e4d962006-09-25 23:31:23 -0700389 BUG_ON(!PageLocked(page));
390 BUG_ON(mapping != page_mapping(page));
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800391
392 write_lock_irq(&mapping->tree_lock);
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800393 /*
Nick Piggin0fd0e6b2006-09-27 01:50:02 -0700394 * The non racy check for a busy page.
395 *
396 * Must be careful with the order of the tests. When someone has
397 * a ref to the page, it may be possible that they dirty it then
398 * drop the reference. So if PageDirty is tested before page_count
399 * here, then the following race may occur:
400 *
401 * get_user_pages(&page);
402 * [user mapping goes away]
403 * write_to(page);
404 * !PageDirty(page) [good]
405 * SetPageDirty(page);
406 * put_page(page);
407 * !page_count(page) [good, discard it]
408 *
409 * [oops, our write_to data is lost]
410 *
411 * Reversing the order of the tests ensures such a situation cannot
412 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
413 * load is not satisfied before that of page->_count.
414 *
415 * Note that if SetPageDirty is always performed via set_page_dirty,
416 * and thus under tree_lock, then this ordering is not required.
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800417 */
418 if (unlikely(page_count(page) != 2))
419 goto cannot_free;
420 smp_rmb();
421 if (unlikely(PageDirty(page)))
422 goto cannot_free;
423
424 if (PageSwapCache(page)) {
425 swp_entry_t swap = { .val = page_private(page) };
426 __delete_from_swap_cache(page);
427 write_unlock_irq(&mapping->tree_lock);
428 swap_free(swap);
429 __put_page(page); /* The pagecache ref */
430 return 1;
431 }
432
433 __remove_from_page_cache(page);
434 write_unlock_irq(&mapping->tree_lock);
435 __put_page(page);
436 return 1;
437
438cannot_free:
439 write_unlock_irq(&mapping->tree_lock);
440 return 0;
441}
442
Linus Torvalds1da177e2005-04-16 15:20:36 -0700443/*
Andrew Morton1742f192006-03-22 00:08:21 -0800444 * shrink_page_list() returns the number of reclaimed pages
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 */
Andrew Morton1742f192006-03-22 00:08:21 -0800446static unsigned long shrink_page_list(struct list_head *page_list,
447 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700448{
449 LIST_HEAD(ret_pages);
450 struct pagevec freed_pvec;
451 int pgactivate = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -0800452 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700453
454 cond_resched();
455
456 pagevec_init(&freed_pvec, 1);
457 while (!list_empty(page_list)) {
458 struct address_space *mapping;
459 struct page *page;
460 int may_enter_fs;
461 int referenced;
462
463 cond_resched();
464
465 page = lru_to_page(page_list);
466 list_del(&page->lru);
467
468 if (TestSetPageLocked(page))
469 goto keep;
470
Nick Piggin725d7042006-09-25 23:30:55 -0700471 VM_BUG_ON(PageActive(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700472
473 sc->nr_scanned++;
Christoph Lameter80e43422006-02-11 17:55:53 -0800474
475 if (!sc->may_swap && page_mapped(page))
476 goto keep_locked;
477
Linus Torvalds1da177e2005-04-16 15:20:36 -0700478 /* Double the slab pressure for mapped and swapcache pages */
479 if (page_mapped(page) || PageSwapCache(page))
480 sc->nr_scanned++;
481
482 if (PageWriteback(page))
483 goto keep_locked;
484
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800485 referenced = page_referenced(page, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700486 /* In active use or really unfreeable? Activate it. */
487 if (referenced && page_mapping_inuse(page))
488 goto activate_locked;
489
490#ifdef CONFIG_SWAP
491 /*
492 * Anonymous process memory has backing store?
493 * Try to allocate it some swap space here.
494 */
Christoph Lameter6e5ef1a2006-03-22 00:08:45 -0800495 if (PageAnon(page) && !PageSwapCache(page))
Christoph Lameter1480a542006-01-08 01:00:53 -0800496 if (!add_to_swap(page, GFP_ATOMIC))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700497 goto activate_locked;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700498#endif /* CONFIG_SWAP */
499
500 mapping = page_mapping(page);
501 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
502 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
503
504 /*
505 * The page is mapped into the page tables of one or more
506 * processes. Try to unmap it here.
507 */
508 if (page_mapped(page) && mapping) {
Christoph Lametera48d07a2006-02-01 03:05:38 -0800509 switch (try_to_unmap(page, 0)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510 case SWAP_FAIL:
511 goto activate_locked;
512 case SWAP_AGAIN:
513 goto keep_locked;
514 case SWAP_SUCCESS:
515 ; /* try to free the page below */
516 }
517 }
518
519 if (PageDirty(page)) {
520 if (referenced)
521 goto keep_locked;
522 if (!may_enter_fs)
523 goto keep_locked;
Christoph Lameter52a83632006-02-01 03:05:28 -0800524 if (!sc->may_writepage)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 goto keep_locked;
526
527 /* Page is dirty, try to write it out here */
528 switch(pageout(page, mapping)) {
529 case PAGE_KEEP:
530 goto keep_locked;
531 case PAGE_ACTIVATE:
532 goto activate_locked;
533 case PAGE_SUCCESS:
534 if (PageWriteback(page) || PageDirty(page))
535 goto keep;
536 /*
537 * A synchronous write - probably a ramdisk. Go
538 * ahead and try to reclaim the page.
539 */
540 if (TestSetPageLocked(page))
541 goto keep;
542 if (PageDirty(page) || PageWriteback(page))
543 goto keep_locked;
544 mapping = page_mapping(page);
545 case PAGE_CLEAN:
546 ; /* try to free the page below */
547 }
548 }
549
550 /*
551 * If the page has buffers, try to free the buffer mappings
552 * associated with this page. If we succeed we try to free
553 * the page as well.
554 *
555 * We do this even if the page is PageDirty().
556 * try_to_release_page() does not perform I/O, but it is
557 * possible for a page to have PageDirty set, but it is actually
558 * clean (all its buffers are clean). This happens if the
559 * buffers were written out directly, with submit_bh(). ext3
560 * will do this, as well as the blockdev mapping.
561 * try_to_release_page() will discover that cleanness and will
562 * drop the buffers and mark the page clean - it can be freed.
563 *
564 * Rarely, pages can have buffers and no ->mapping. These are
565 * the pages which were not successfully invalidated in
566 * truncate_complete_page(). We try to drop those buffers here
567 * and if that worked, and the page is no longer mapped into
568 * process address space (page_count == 1) it can be freed.
569 * Otherwise, leave the page on the LRU so it is swappable.
570 */
571 if (PagePrivate(page)) {
572 if (!try_to_release_page(page, sc->gfp_mask))
573 goto activate_locked;
574 if (!mapping && page_count(page) == 1)
575 goto free_it;
576 }
577
Nick Piggin28e4d962006-09-25 23:31:23 -0700578 if (!mapping || !remove_mapping(mapping, page))
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800579 goto keep_locked;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580
581free_it:
582 unlock_page(page);
Andrew Morton05ff5132006-03-22 00:08:20 -0800583 nr_reclaimed++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700584 if (!pagevec_add(&freed_pvec, page))
585 __pagevec_release_nonlru(&freed_pvec);
586 continue;
587
588activate_locked:
589 SetPageActive(page);
590 pgactivate++;
591keep_locked:
592 unlock_page(page);
593keep:
594 list_add(&page->lru, &ret_pages);
Nick Piggin725d7042006-09-25 23:30:55 -0700595 VM_BUG_ON(PageLRU(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700596 }
597 list_splice(&ret_pages, page_list);
598 if (pagevec_count(&freed_pvec))
599 __pagevec_release_nonlru(&freed_pvec);
Christoph Lameterf8891e52006-06-30 01:55:45 -0700600 count_vm_events(PGACTIVATE, pgactivate);
Andrew Morton05ff5132006-03-22 00:08:20 -0800601 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700602}
603
Christoph Lameter49d2e9c2006-01-08 01:00:48 -0800604/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700605 * zone->lru_lock is heavily contended. Some of the functions that
606 * shrink the lists perform better by taking out a batch of pages
607 * and working on them outside the LRU lock.
608 *
609 * For pagecache intensive workloads, this function is the hottest
610 * spot in the kernel (apart from copy_*_user functions).
611 *
612 * Appropriate locks must be held before calling this function.
613 *
614 * @nr_to_scan: The number of pages to look through on the list.
615 * @src: The LRU list to pull pages off.
616 * @dst: The temp list to put pages on to.
617 * @scanned: The number of pages that were scanned.
618 *
619 * returns how many pages were moved onto *@dst.
620 */
Andrew Morton69e05942006-03-22 00:08:19 -0800621static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
622 struct list_head *src, struct list_head *dst,
623 unsigned long *scanned)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700624{
Andrew Morton69e05942006-03-22 00:08:19 -0800625 unsigned long nr_taken = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700626 struct page *page;
Wu Fengguangc9b02d92006-03-22 00:08:23 -0800627 unsigned long scan;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700628
Wu Fengguangc9b02d92006-03-22 00:08:23 -0800629 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800630 struct list_head *target;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 page = lru_to_page(src);
632 prefetchw_prev_lru_page(page, src, flags);
633
Nick Piggin725d7042006-09-25 23:30:55 -0700634 VM_BUG_ON(!PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800635
Nick Piggin053837f2006-01-18 17:42:27 -0800636 list_del(&page->lru);
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800637 target = src;
638 if (likely(get_page_unless_zero(page))) {
Nick Piggin053837f2006-01-18 17:42:27 -0800639 /*
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800640 * Be careful not to clear PageLRU until after we're
641 * sure the page is not being freed elsewhere -- the
642 * page release code relies on it.
Nick Piggin053837f2006-01-18 17:42:27 -0800643 */
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800644 ClearPageLRU(page);
645 target = dst;
646 nr_taken++;
647 } /* else it is being freed elsewhere */
Nick Piggin46453a62006-03-22 00:07:58 -0800648
Nick Piggin7c8ee9a2006-03-22 00:08:03 -0800649 list_add(&page->lru, target);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700650 }
651
652 *scanned = scan;
653 return nr_taken;
654}
655
656/*
Andrew Morton1742f192006-03-22 00:08:21 -0800657 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
658 * of reclaimed pages
Linus Torvalds1da177e2005-04-16 15:20:36 -0700659 */
Andrew Morton1742f192006-03-22 00:08:21 -0800660static unsigned long shrink_inactive_list(unsigned long max_scan,
661 struct zone *zone, struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700662{
663 LIST_HEAD(page_list);
664 struct pagevec pvec;
Andrew Morton69e05942006-03-22 00:08:19 -0800665 unsigned long nr_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -0800666 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667
668 pagevec_init(&pvec, 1);
669
670 lru_add_drain();
671 spin_lock_irq(&zone->lru_lock);
Andrew Morton69e05942006-03-22 00:08:19 -0800672 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700673 struct page *page;
Andrew Morton69e05942006-03-22 00:08:19 -0800674 unsigned long nr_taken;
675 unsigned long nr_scan;
676 unsigned long nr_freed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700677
678 nr_taken = isolate_lru_pages(sc->swap_cluster_max,
679 &zone->inactive_list,
680 &page_list, &nr_scan);
681 zone->nr_inactive -= nr_taken;
682 zone->pages_scanned += nr_scan;
683 spin_unlock_irq(&zone->lru_lock);
684
Andrew Morton69e05942006-03-22 00:08:19 -0800685 nr_scanned += nr_scan;
Andrew Morton1742f192006-03-22 00:08:21 -0800686 nr_freed = shrink_page_list(&page_list, sc);
Andrew Morton05ff5132006-03-22 00:08:20 -0800687 nr_reclaimed += nr_freed;
Nick Piggina74609f2006-01-06 00:11:20 -0800688 local_irq_disable();
689 if (current_is_kswapd()) {
Christoph Lameterf8891e52006-06-30 01:55:45 -0700690 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
691 __count_vm_events(KSWAPD_STEAL, nr_freed);
Nick Piggina74609f2006-01-06 00:11:20 -0800692 } else
Christoph Lameterf8891e52006-06-30 01:55:45 -0700693 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
694 __count_vm_events(PGACTIVATE, nr_freed);
Nick Piggina74609f2006-01-06 00:11:20 -0800695
Wu Fengguangfb8d14e2006-03-22 00:08:28 -0800696 if (nr_taken == 0)
697 goto done;
698
Nick Piggina74609f2006-01-06 00:11:20 -0800699 spin_lock(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700700 /*
701 * Put back any unfreeable pages.
702 */
703 while (!list_empty(&page_list)) {
704 page = lru_to_page(&page_list);
Nick Piggin725d7042006-09-25 23:30:55 -0700705 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800706 SetPageLRU(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700707 list_del(&page->lru);
708 if (PageActive(page))
709 add_page_to_active_list(zone, page);
710 else
711 add_page_to_inactive_list(zone, page);
712 if (!pagevec_add(&pvec, page)) {
713 spin_unlock_irq(&zone->lru_lock);
714 __pagevec_release(&pvec);
715 spin_lock_irq(&zone->lru_lock);
716 }
717 }
Andrew Morton69e05942006-03-22 00:08:19 -0800718 } while (nr_scanned < max_scan);
Wu Fengguangfb8d14e2006-03-22 00:08:28 -0800719 spin_unlock(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720done:
Wu Fengguangfb8d14e2006-03-22 00:08:28 -0800721 local_irq_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700722 pagevec_release(&pvec);
Andrew Morton05ff5132006-03-22 00:08:20 -0800723 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724}
725
Martin Bligh3bb1a852006-10-28 10:38:24 -0700726/*
727 * We are about to scan this zone at a certain priority level. If that priority
728 * level is smaller (ie: more urgent) than the previous priority, then note
729 * that priority level within the zone. This is done so that when the next
730 * process comes in to scan this zone, it will immediately start out at this
731 * priority level rather than having to build up its own scanning priority.
732 * Here, this priority affects only the reclaim-mapped threshold.
733 */
734static inline void note_zone_scanning_priority(struct zone *zone, int priority)
735{
736 if (priority < zone->prev_priority)
737 zone->prev_priority = priority;
738}
739
Nick Piggin4ff1ffb2006-09-25 23:31:28 -0700740static inline int zone_is_near_oom(struct zone *zone)
741{
742 return zone->pages_scanned >= (zone->nr_active + zone->nr_inactive)*3;
743}
744
Linus Torvalds1da177e2005-04-16 15:20:36 -0700745/*
746 * This moves pages from the active list to the inactive list.
747 *
748 * We move them the other way if the page is referenced by one or more
749 * processes, from rmap.
750 *
751 * If the pages are mostly unmapped, the processing is fast and it is
752 * appropriate to hold zone->lru_lock across the whole operation. But if
753 * the pages are mapped, the processing is slow (page_referenced()) so we
754 * should drop zone->lru_lock around each page. It's impossible to balance
755 * this, so instead we remove the pages from the LRU while processing them.
756 * It is safe to rely on PG_active against the non-LRU pages in here because
757 * nobody will play with that bit on a non-LRU page.
758 *
759 * The downside is that we have to touch page->_count against each page.
760 * But we had to alter page->flags anyway.
761 */
Andrew Morton1742f192006-03-22 00:08:21 -0800762static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
Martin Blighbbdb3962006-10-28 10:38:25 -0700763 struct scan_control *sc, int priority)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700764{
Andrew Morton69e05942006-03-22 00:08:19 -0800765 unsigned long pgmoved;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700766 int pgdeactivate = 0;
Andrew Morton69e05942006-03-22 00:08:19 -0800767 unsigned long pgscanned;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700768 LIST_HEAD(l_hold); /* The pages which were snipped off */
769 LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */
770 LIST_HEAD(l_active); /* Pages to go onto the active_list */
771 struct page *page;
772 struct pagevec pvec;
773 int reclaim_mapped = 0;
Christoph Lameter2903fb12006-02-11 17:55:55 -0800774
Christoph Lameter6e5ef1a2006-03-22 00:08:45 -0800775 if (sc->may_swap) {
Christoph Lameter2903fb12006-02-11 17:55:55 -0800776 long mapped_ratio;
777 long distress;
778 long swap_tendency;
779
Nick Piggin4ff1ffb2006-09-25 23:31:28 -0700780 if (zone_is_near_oom(zone))
781 goto force_reclaim_mapped;
782
Christoph Lameter2903fb12006-02-11 17:55:55 -0800783 /*
784 * `distress' is a measure of how much trouble we're having
785 * reclaiming pages. 0 -> no problems. 100 -> great trouble.
786 */
Martin Blighbbdb3962006-10-28 10:38:25 -0700787 distress = 100 >> min(zone->prev_priority, priority);
Christoph Lameter2903fb12006-02-11 17:55:55 -0800788
789 /*
790 * The point of this algorithm is to decide when to start
791 * reclaiming mapped memory instead of just pagecache. Work out
792 * how much memory
793 * is mapped.
794 */
Christoph Lameterf3dbd342006-06-30 01:55:36 -0700795 mapped_ratio = ((global_page_state(NR_FILE_MAPPED) +
796 global_page_state(NR_ANON_PAGES)) * 100) /
Christoph Lameterbf02cf42006-06-30 01:55:36 -0700797 vm_total_pages;
Christoph Lameter2903fb12006-02-11 17:55:55 -0800798
799 /*
800 * Now decide how much we really want to unmap some pages. The
801 * mapped ratio is downgraded - just because there's a lot of
802 * mapped memory doesn't necessarily mean that page reclaim
803 * isn't succeeding.
804 *
805 * The distress ratio is important - we don't want to start
806 * going oom.
807 *
808 * A 100% value of vm_swappiness overrides this algorithm
809 * altogether.
810 */
Rafael J. Wysockid6277db2006-06-23 02:03:18 -0700811 swap_tendency = mapped_ratio / 2 + distress + sc->swappiness;
Christoph Lameter2903fb12006-02-11 17:55:55 -0800812
813 /*
814 * Now use this metric to decide whether to start moving mapped
815 * memory onto the inactive list.
816 */
817 if (swap_tendency >= 100)
Nick Piggin4ff1ffb2006-09-25 23:31:28 -0700818force_reclaim_mapped:
Christoph Lameter2903fb12006-02-11 17:55:55 -0800819 reclaim_mapped = 1;
820 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700821
822 lru_add_drain();
823 spin_lock_irq(&zone->lru_lock);
824 pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
825 &l_hold, &pgscanned);
826 zone->pages_scanned += pgscanned;
827 zone->nr_active -= pgmoved;
828 spin_unlock_irq(&zone->lru_lock);
829
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830 while (!list_empty(&l_hold)) {
831 cond_resched();
832 page = lru_to_page(&l_hold);
833 list_del(&page->lru);
834 if (page_mapped(page)) {
835 if (!reclaim_mapped ||
836 (total_swap_pages == 0 && PageAnon(page)) ||
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800837 page_referenced(page, 0)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700838 list_add(&page->lru, &l_active);
839 continue;
840 }
841 }
842 list_add(&page->lru, &l_inactive);
843 }
844
845 pagevec_init(&pvec, 1);
846 pgmoved = 0;
847 spin_lock_irq(&zone->lru_lock);
848 while (!list_empty(&l_inactive)) {
849 page = lru_to_page(&l_inactive);
850 prefetchw_prev_lru_page(page, &l_inactive, flags);
Nick Piggin725d7042006-09-25 23:30:55 -0700851 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800852 SetPageLRU(page);
Nick Piggin725d7042006-09-25 23:30:55 -0700853 VM_BUG_ON(!PageActive(page));
Nick Piggin4c84cac2006-03-22 00:08:00 -0800854 ClearPageActive(page);
855
Linus Torvalds1da177e2005-04-16 15:20:36 -0700856 list_move(&page->lru, &zone->inactive_list);
857 pgmoved++;
858 if (!pagevec_add(&pvec, page)) {
859 zone->nr_inactive += pgmoved;
860 spin_unlock_irq(&zone->lru_lock);
861 pgdeactivate += pgmoved;
862 pgmoved = 0;
863 if (buffer_heads_over_limit)
864 pagevec_strip(&pvec);
865 __pagevec_release(&pvec);
866 spin_lock_irq(&zone->lru_lock);
867 }
868 }
869 zone->nr_inactive += pgmoved;
870 pgdeactivate += pgmoved;
871 if (buffer_heads_over_limit) {
872 spin_unlock_irq(&zone->lru_lock);
873 pagevec_strip(&pvec);
874 spin_lock_irq(&zone->lru_lock);
875 }
876
877 pgmoved = 0;
878 while (!list_empty(&l_active)) {
879 page = lru_to_page(&l_active);
880 prefetchw_prev_lru_page(page, &l_active, flags);
Nick Piggin725d7042006-09-25 23:30:55 -0700881 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800882 SetPageLRU(page);
Nick Piggin725d7042006-09-25 23:30:55 -0700883 VM_BUG_ON(!PageActive(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700884 list_move(&page->lru, &zone->active_list);
885 pgmoved++;
886 if (!pagevec_add(&pvec, page)) {
887 zone->nr_active += pgmoved;
888 pgmoved = 0;
889 spin_unlock_irq(&zone->lru_lock);
890 __pagevec_release(&pvec);
891 spin_lock_irq(&zone->lru_lock);
892 }
893 }
894 zone->nr_active += pgmoved;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700895
Christoph Lameterf8891e52006-06-30 01:55:45 -0700896 __count_zone_vm_events(PGREFILL, zone, pgscanned);
897 __count_vm_events(PGDEACTIVATE, pgdeactivate);
898 spin_unlock_irq(&zone->lru_lock);
Nick Piggina74609f2006-01-06 00:11:20 -0800899
900 pagevec_release(&pvec);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700901}
902
903/*
904 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
905 */
Andrew Morton05ff5132006-03-22 00:08:20 -0800906static unsigned long shrink_zone(int priority, struct zone *zone,
907 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700908{
909 unsigned long nr_active;
910 unsigned long nr_inactive;
Christoph Lameter86959492006-03-22 00:08:18 -0800911 unsigned long nr_to_scan;
Andrew Morton05ff5132006-03-22 00:08:20 -0800912 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700913
Martin Hicks53e9a612005-09-03 15:54:51 -0700914 atomic_inc(&zone->reclaim_in_progress);
915
Linus Torvalds1da177e2005-04-16 15:20:36 -0700916 /*
917 * Add one to `nr_to_scan' just to make sure that the kernel will
918 * slowly sift through the active list.
919 */
Christoph Lameter86959492006-03-22 00:08:18 -0800920 zone->nr_scan_active += (zone->nr_active >> priority) + 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700921 nr_active = zone->nr_scan_active;
922 if (nr_active >= sc->swap_cluster_max)
923 zone->nr_scan_active = 0;
924 else
925 nr_active = 0;
926
Christoph Lameter86959492006-03-22 00:08:18 -0800927 zone->nr_scan_inactive += (zone->nr_inactive >> priority) + 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700928 nr_inactive = zone->nr_scan_inactive;
929 if (nr_inactive >= sc->swap_cluster_max)
930 zone->nr_scan_inactive = 0;
931 else
932 nr_inactive = 0;
933
Linus Torvalds1da177e2005-04-16 15:20:36 -0700934 while (nr_active || nr_inactive) {
935 if (nr_active) {
Christoph Lameter86959492006-03-22 00:08:18 -0800936 nr_to_scan = min(nr_active,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700937 (unsigned long)sc->swap_cluster_max);
Christoph Lameter86959492006-03-22 00:08:18 -0800938 nr_active -= nr_to_scan;
Martin Blighbbdb3962006-10-28 10:38:25 -0700939 shrink_active_list(nr_to_scan, zone, sc, priority);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700940 }
941
942 if (nr_inactive) {
Christoph Lameter86959492006-03-22 00:08:18 -0800943 nr_to_scan = min(nr_inactive,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700944 (unsigned long)sc->swap_cluster_max);
Christoph Lameter86959492006-03-22 00:08:18 -0800945 nr_inactive -= nr_to_scan;
Andrew Morton1742f192006-03-22 00:08:21 -0800946 nr_reclaimed += shrink_inactive_list(nr_to_scan, zone,
947 sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700948 }
949 }
950
951 throttle_vm_writeout();
Martin Hicks53e9a612005-09-03 15:54:51 -0700952
953 atomic_dec(&zone->reclaim_in_progress);
Andrew Morton05ff5132006-03-22 00:08:20 -0800954 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700955}
956
957/*
958 * This is the direct reclaim path, for page-allocating processes. We only
959 * try to reclaim pages from zones which will satisfy the caller's allocation
960 * request.
961 *
962 * We reclaim from a zone even if that zone is over pages_high. Because:
963 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
964 * allocation or
965 * b) The zones may be over pages_high but they must go *over* pages_high to
966 * satisfy the `incremental min' zone defense algorithm.
967 *
968 * Returns the number of reclaimed pages.
969 *
970 * If a zone is deemed to be full of pinned pages then just give it a light
971 * scan then give up on it.
972 */
Andrew Morton1742f192006-03-22 00:08:21 -0800973static unsigned long shrink_zones(int priority, struct zone **zones,
Andrew Morton05ff5132006-03-22 00:08:20 -0800974 struct scan_control *sc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700975{
Andrew Morton05ff5132006-03-22 00:08:20 -0800976 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700977 int i;
978
Nick Piggin408d8542006-09-25 23:31:27 -0700979 sc->all_unreclaimable = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700980 for (i = 0; zones[i] != NULL; i++) {
981 struct zone *zone = zones[i];
982
Con Kolivasf3fe6512006-01-06 00:11:15 -0800983 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700984 continue;
985
Paul Jackson9bf22292005-09-06 15:18:12 -0700986 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700987 continue;
988
Martin Bligh3bb1a852006-10-28 10:38:24 -0700989 note_zone_scanning_priority(zone, priority);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700990
Christoph Lameter86959492006-03-22 00:08:18 -0800991 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700992 continue; /* Let kswapd poll it */
993
Nick Piggin408d8542006-09-25 23:31:27 -0700994 sc->all_unreclaimable = 0;
995
Andrew Morton05ff5132006-03-22 00:08:20 -0800996 nr_reclaimed += shrink_zone(priority, zone, sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700997 }
Andrew Morton05ff5132006-03-22 00:08:20 -0800998 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700999}
1000
1001/*
1002 * This is the main entry point to direct page reclaim.
1003 *
1004 * If a full scan of the inactive list fails to free enough memory then we
1005 * are "out of memory" and something needs to be killed.
1006 *
1007 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1008 * high - the zone may be full of dirty or under-writeback pages, which this
1009 * caller can't do much about. We kick pdflush and take explicit naps in the
1010 * hope that some of these pages can be written. But if the allocating task
1011 * holds filesystem locks which prevent writeout this might not work, and the
1012 * allocation attempt will fail.
1013 */
Andrew Morton69e05942006-03-22 00:08:19 -08001014unsigned long try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001015{
1016 int priority;
1017 int ret = 0;
Andrew Morton69e05942006-03-22 00:08:19 -08001018 unsigned long total_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -08001019 unsigned long nr_reclaimed = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020 struct reclaim_state *reclaim_state = current->reclaim_state;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001021 unsigned long lru_pages = 0;
1022 int i;
Andrew Morton179e9632006-03-22 00:08:18 -08001023 struct scan_control sc = {
1024 .gfp_mask = gfp_mask,
1025 .may_writepage = !laptop_mode,
1026 .swap_cluster_max = SWAP_CLUSTER_MAX,
1027 .may_swap = 1,
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001028 .swappiness = vm_swappiness,
Andrew Morton179e9632006-03-22 00:08:18 -08001029 };
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030
Christoph Lameterf8891e52006-06-30 01:55:45 -07001031 count_vm_event(ALLOCSTALL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001032
1033 for (i = 0; zones[i] != NULL; i++) {
1034 struct zone *zone = zones[i];
1035
Paul Jackson9bf22292005-09-06 15:18:12 -07001036 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001037 continue;
1038
Linus Torvalds1da177e2005-04-16 15:20:36 -07001039 lru_pages += zone->nr_active + zone->nr_inactive;
1040 }
1041
1042 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043 sc.nr_scanned = 0;
Rik van Rielf7b7fd82005-11-28 13:44:07 -08001044 if (!priority)
1045 disable_swap_token();
Andrew Morton1742f192006-03-22 00:08:21 -08001046 nr_reclaimed += shrink_zones(priority, zones, &sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001047 shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
1048 if (reclaim_state) {
Andrew Morton05ff5132006-03-22 00:08:20 -08001049 nr_reclaimed += reclaim_state->reclaimed_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001050 reclaim_state->reclaimed_slab = 0;
1051 }
1052 total_scanned += sc.nr_scanned;
Andrew Morton05ff5132006-03-22 00:08:20 -08001053 if (nr_reclaimed >= sc.swap_cluster_max) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054 ret = 1;
1055 goto out;
1056 }
1057
1058 /*
1059 * Try to write back as many pages as we just scanned. This
1060 * tends to cause slow streaming writers to write data to the
1061 * disk smoothly, at the dirtying rate, which is nice. But
1062 * that's undesirable in laptop mode, where we *want* lumpy
1063 * writeout. So in laptop mode, write out the whole world.
1064 */
Andrew Morton179e9632006-03-22 00:08:18 -08001065 if (total_scanned > sc.swap_cluster_max +
1066 sc.swap_cluster_max / 2) {
Pekka J Enberg687a21c2005-06-28 20:44:55 -07001067 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001068 sc.may_writepage = 1;
1069 }
1070
1071 /* Take a nap, wait for some writeback to complete */
1072 if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
Andrew Morton3fcfab12006-10-19 23:28:16 -07001073 congestion_wait(WRITE, HZ/10);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001074 }
Nick Piggin408d8542006-09-25 23:31:27 -07001075 /* top priority shrink_caches still had more to do? don't OOM, then */
1076 if (!sc.all_unreclaimable)
1077 ret = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078out:
Martin Bligh3bb1a852006-10-28 10:38:24 -07001079 /*
1080 * Now that we've scanned all the zones at this priority level, note
1081 * that level within the zone so that the next thread which performs
1082 * scanning of this zone will immediately start out at this priority
1083 * level. This affects only the decision whether or not to bring
1084 * mapped pages onto the inactive list.
1085 */
1086 if (priority < 0)
1087 priority = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001088 for (i = 0; zones[i] != 0; i++) {
1089 struct zone *zone = zones[i];
1090
Paul Jackson9bf22292005-09-06 15:18:12 -07001091 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001092 continue;
1093
Martin Bligh3bb1a852006-10-28 10:38:24 -07001094 zone->prev_priority = priority;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001095 }
1096 return ret;
1097}
1098
1099/*
1100 * For kswapd, balance_pgdat() will work across all this node's zones until
1101 * they are all at pages_high.
1102 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103 * Returns the number of pages which were actually freed.
1104 *
1105 * There is special handling here for zones which are full of pinned pages.
1106 * This can happen if the pages are all mlocked, or if they are all used by
1107 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1108 * What we do is to detect the case where all pages in the zone have been
1109 * scanned twice and there has been zero successful reclaim. Mark the zone as
1110 * dead and from now on, only perform a short scan. Basically we're polling
1111 * the zone for when the problem goes away.
1112 *
1113 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1114 * zones which have free_pages > pages_high, but once a zone is found to have
1115 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1116 * of the number of free pages in the lower zones. This interoperates with
1117 * the page allocator fallback scheme to ensure that aging of pages is balanced
1118 * across the zones.
1119 */
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001120static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001122 int all_zones_ok;
1123 int priority;
1124 int i;
Andrew Morton69e05942006-03-22 00:08:19 -08001125 unsigned long total_scanned;
Andrew Morton05ff5132006-03-22 00:08:20 -08001126 unsigned long nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001127 struct reclaim_state *reclaim_state = current->reclaim_state;
Andrew Morton179e9632006-03-22 00:08:18 -08001128 struct scan_control sc = {
1129 .gfp_mask = GFP_KERNEL,
1130 .may_swap = 1,
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001131 .swap_cluster_max = SWAP_CLUSTER_MAX,
1132 .swappiness = vm_swappiness,
Andrew Morton179e9632006-03-22 00:08:18 -08001133 };
Martin Bligh3bb1a852006-10-28 10:38:24 -07001134 /*
1135 * temp_priority is used to remember the scanning priority at which
1136 * this zone was successfully refilled to free_pages == pages_high.
1137 */
1138 int temp_priority[MAX_NR_ZONES];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001139
1140loop_again:
1141 total_scanned = 0;
Andrew Morton05ff5132006-03-22 00:08:20 -08001142 nr_reclaimed = 0;
Christoph Lameterc0bbbc72006-06-11 15:22:26 -07001143 sc.may_writepage = !laptop_mode;
Christoph Lameterf8891e52006-06-30 01:55:45 -07001144 count_vm_event(PAGEOUTRUN);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145
Martin Bligh3bb1a852006-10-28 10:38:24 -07001146 for (i = 0; i < pgdat->nr_zones; i++)
1147 temp_priority[i] = DEF_PRIORITY;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001148
1149 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1150 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1151 unsigned long lru_pages = 0;
1152
Rik van Rielf7b7fd82005-11-28 13:44:07 -08001153 /* The swap token gets in the way of swapout... */
1154 if (!priority)
1155 disable_swap_token();
1156
Linus Torvalds1da177e2005-04-16 15:20:36 -07001157 all_zones_ok = 1;
1158
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001159 /*
1160 * Scan in the highmem->dma direction for the highest
1161 * zone which needs scanning
1162 */
1163 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1164 struct zone *zone = pgdat->node_zones + i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001165
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001166 if (!populated_zone(zone))
1167 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001168
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001169 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1170 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001171
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001172 if (!zone_watermark_ok(zone, order, zone->pages_high,
1173 0, 0)) {
1174 end_zone = i;
1175 goto scan;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001176 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001177 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001178 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001179scan:
1180 for (i = 0; i <= end_zone; i++) {
1181 struct zone *zone = pgdat->node_zones + i;
1182
1183 lru_pages += zone->nr_active + zone->nr_inactive;
1184 }
1185
1186 /*
1187 * Now scan the zone in the dma->highmem direction, stopping
1188 * at the last zone which needs scanning.
1189 *
1190 * We do this because the page allocator works in the opposite
1191 * direction. This prevents the page allocator from allocating
1192 * pages behind kswapd's direction of progress, which would
1193 * cause too much scanning of the lower zones.
1194 */
1195 for (i = 0; i <= end_zone; i++) {
1196 struct zone *zone = pgdat->node_zones + i;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001197 int nr_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001198
Con Kolivasf3fe6512006-01-06 00:11:15 -08001199 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001200 continue;
1201
1202 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1203 continue;
1204
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001205 if (!zone_watermark_ok(zone, order, zone->pages_high,
1206 end_zone, 0))
1207 all_zones_ok = 0;
Martin Bligh3bb1a852006-10-28 10:38:24 -07001208 temp_priority[i] = priority;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001209 sc.nr_scanned = 0;
Martin Bligh3bb1a852006-10-28 10:38:24 -07001210 note_zone_scanning_priority(zone, priority);
Andrew Morton05ff5132006-03-22 00:08:20 -08001211 nr_reclaimed += shrink_zone(priority, zone, &sc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001212 reclaim_state->reclaimed_slab = 0;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001213 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1214 lru_pages);
Andrew Morton05ff5132006-03-22 00:08:20 -08001215 nr_reclaimed += reclaim_state->reclaimed_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001216 total_scanned += sc.nr_scanned;
1217 if (zone->all_unreclaimable)
1218 continue;
akpm@osdl.orgb15e0902005-06-21 17:14:35 -07001219 if (nr_slab == 0 && zone->pages_scanned >=
Nick Piggin4ff1ffb2006-09-25 23:31:28 -07001220 (zone->nr_active + zone->nr_inactive) * 6)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001221 zone->all_unreclaimable = 1;
1222 /*
1223 * If we've done a decent amount of scanning and
1224 * the reclaim ratio is low, start doing writepage
1225 * even in laptop mode
1226 */
1227 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
Andrew Morton05ff5132006-03-22 00:08:20 -08001228 total_scanned > nr_reclaimed + nr_reclaimed / 2)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001229 sc.may_writepage = 1;
1230 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001231 if (all_zones_ok)
1232 break; /* kswapd: all done */
1233 /*
1234 * OK, kswapd is getting into trouble. Take a nap, then take
1235 * another pass across the zones.
1236 */
1237 if (total_scanned && priority < DEF_PRIORITY - 2)
Andrew Morton3fcfab12006-10-19 23:28:16 -07001238 congestion_wait(WRITE, HZ/10);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001239
1240 /*
1241 * We do this so kswapd doesn't build up large priorities for
1242 * example when it is freeing in parallel with allocators. It
1243 * matches the direct reclaim path behaviour in terms of impact
1244 * on zone->*_priority.
1245 */
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001246 if (nr_reclaimed >= SWAP_CLUSTER_MAX)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001247 break;
1248 }
1249out:
Martin Bligh3bb1a852006-10-28 10:38:24 -07001250 /*
1251 * Note within each zone the priority level at which this zone was
1252 * brought into a happy state. So that the next thread which scans this
1253 * zone will start out at that priority level.
1254 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001255 for (i = 0; i < pgdat->nr_zones; i++) {
1256 struct zone *zone = pgdat->node_zones + i;
1257
Martin Bligh3bb1a852006-10-28 10:38:24 -07001258 zone->prev_priority = temp_priority[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001259 }
1260 if (!all_zones_ok) {
1261 cond_resched();
1262 goto loop_again;
1263 }
1264
Andrew Morton05ff5132006-03-22 00:08:20 -08001265 return nr_reclaimed;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001266}
1267
1268/*
1269 * The background pageout daemon, started as a kernel thread
1270 * from the init process.
1271 *
1272 * This basically trickles out pages so that we have _some_
1273 * free memory available even if there is no other activity
1274 * that frees anything up. This is needed for things like routing
1275 * etc, where we otherwise might have all activity going on in
1276 * asynchronous contexts that cannot page things out.
1277 *
1278 * If there are applications that are active memory-allocators
1279 * (most normal use), this basically shouldn't matter.
1280 */
1281static int kswapd(void *p)
1282{
1283 unsigned long order;
1284 pg_data_t *pgdat = (pg_data_t*)p;
1285 struct task_struct *tsk = current;
1286 DEFINE_WAIT(wait);
1287 struct reclaim_state reclaim_state = {
1288 .reclaimed_slab = 0,
1289 };
1290 cpumask_t cpumask;
1291
Linus Torvalds1da177e2005-04-16 15:20:36 -07001292 cpumask = node_to_cpumask(pgdat->node_id);
1293 if (!cpus_empty(cpumask))
1294 set_cpus_allowed(tsk, cpumask);
1295 current->reclaim_state = &reclaim_state;
1296
1297 /*
1298 * Tell the memory management that we're a "memory allocator",
1299 * and that if we need more memory we should get access to it
1300 * regardless (see "__alloc_pages()"). "kswapd" should
1301 * never get caught in the normal page freeing logic.
1302 *
1303 * (Kswapd normally doesn't need memory anyway, but sometimes
1304 * you need a small amount of memory in order to be able to
1305 * page out something else, and this flag essentially protects
1306 * us from recursively trying to free more memory as we're
1307 * trying to free the first piece of memory in the first place).
1308 */
Christoph Lameter930d9152006-01-08 01:00:47 -08001309 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001310
1311 order = 0;
1312 for ( ; ; ) {
1313 unsigned long new_order;
Christoph Lameter3e1d1d22005-06-24 23:13:50 -07001314
1315 try_to_freeze();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001316
1317 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1318 new_order = pgdat->kswapd_max_order;
1319 pgdat->kswapd_max_order = 0;
1320 if (order < new_order) {
1321 /*
1322 * Don't sleep if someone wants a larger 'order'
1323 * allocation
1324 */
1325 order = new_order;
1326 } else {
1327 schedule();
1328 order = pgdat->kswapd_max_order;
1329 }
1330 finish_wait(&pgdat->kswapd_wait, &wait);
1331
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001332 balance_pgdat(pgdat, order);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001333 }
1334 return 0;
1335}
1336
1337/*
1338 * A zone is low on free memory, so wake its kswapd task to service it.
1339 */
1340void wakeup_kswapd(struct zone *zone, int order)
1341{
1342 pg_data_t *pgdat;
1343
Con Kolivasf3fe6512006-01-06 00:11:15 -08001344 if (!populated_zone(zone))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345 return;
1346
1347 pgdat = zone->zone_pgdat;
Rohit Seth7fb1d9f2005-11-13 16:06:43 -08001348 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349 return;
1350 if (pgdat->kswapd_max_order < order)
1351 pgdat->kswapd_max_order = order;
Paul Jackson9bf22292005-09-06 15:18:12 -07001352 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001354 if (!waitqueue_active(&pgdat->kswapd_wait))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001355 return;
Con Kolivas8d0986e2005-09-13 01:25:07 -07001356 wake_up_interruptible(&pgdat->kswapd_wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001357}
1358
1359#ifdef CONFIG_PM
1360/*
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001361 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1362 * from LRU lists system-wide, for given pass and priority, and returns the
1363 * number of reclaimed pages
1364 *
1365 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1366 */
1367static unsigned long shrink_all_zones(unsigned long nr_pages, int pass,
1368 int prio, struct scan_control *sc)
1369{
1370 struct zone *zone;
1371 unsigned long nr_to_scan, ret = 0;
1372
1373 for_each_zone(zone) {
1374
1375 if (!populated_zone(zone))
1376 continue;
1377
1378 if (zone->all_unreclaimable && prio != DEF_PRIORITY)
1379 continue;
1380
1381 /* For pass = 0 we don't shrink the active list */
1382 if (pass > 0) {
1383 zone->nr_scan_active += (zone->nr_active >> prio) + 1;
1384 if (zone->nr_scan_active >= nr_pages || pass > 3) {
1385 zone->nr_scan_active = 0;
1386 nr_to_scan = min(nr_pages, zone->nr_active);
Martin Blighbbdb3962006-10-28 10:38:25 -07001387 shrink_active_list(nr_to_scan, zone, sc, prio);
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001388 }
1389 }
1390
1391 zone->nr_scan_inactive += (zone->nr_inactive >> prio) + 1;
1392 if (zone->nr_scan_inactive >= nr_pages || pass > 3) {
1393 zone->nr_scan_inactive = 0;
1394 nr_to_scan = min(nr_pages, zone->nr_inactive);
1395 ret += shrink_inactive_list(nr_to_scan, zone, sc);
1396 if (ret >= nr_pages)
1397 return ret;
1398 }
1399 }
1400
1401 return ret;
1402}
1403
1404/*
1405 * Try to free `nr_pages' of memory, system-wide, and return the number of
1406 * freed pages.
1407 *
1408 * Rather than trying to age LRUs the aim is to preserve the overall
1409 * LRU order by reclaiming preferentially
1410 * inactive > active > active referenced > active mapped
Linus Torvalds1da177e2005-04-16 15:20:36 -07001411 */
Andrew Morton69e05942006-03-22 00:08:19 -08001412unsigned long shrink_all_memory(unsigned long nr_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001413{
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001414 unsigned long lru_pages, nr_slab;
Andrew Morton69e05942006-03-22 00:08:19 -08001415 unsigned long ret = 0;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001416 int pass;
1417 struct reclaim_state reclaim_state;
1418 struct zone *zone;
1419 struct scan_control sc = {
1420 .gfp_mask = GFP_KERNEL,
1421 .may_swap = 0,
1422 .swap_cluster_max = nr_pages,
1423 .may_writepage = 1,
1424 .swappiness = vm_swappiness,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001425 };
1426
1427 current->reclaim_state = &reclaim_state;
Andrew Morton69e05942006-03-22 00:08:19 -08001428
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001429 lru_pages = 0;
1430 for_each_zone(zone)
1431 lru_pages += zone->nr_active + zone->nr_inactive;
1432
Christoph Lameter972d1a72006-09-25 23:31:51 -07001433 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001434 /* If slab caches are huge, it's better to hit them first */
1435 while (nr_slab >= lru_pages) {
1436 reclaim_state.reclaimed_slab = 0;
1437 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
1438 if (!reclaim_state.reclaimed_slab)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001439 break;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001440
1441 ret += reclaim_state.reclaimed_slab;
1442 if (ret >= nr_pages)
1443 goto out;
1444
1445 nr_slab -= reclaim_state.reclaimed_slab;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001446 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001447
1448 /*
1449 * We try to shrink LRUs in 5 passes:
1450 * 0 = Reclaim from inactive_list only
1451 * 1 = Reclaim from active list but don't reclaim mapped
1452 * 2 = 2nd pass of type 1
1453 * 3 = Reclaim mapped (normal reclaim)
1454 * 4 = 2nd pass of type 3
1455 */
1456 for (pass = 0; pass < 5; pass++) {
1457 int prio;
1458
1459 /* Needed for shrinking slab caches later on */
1460 if (!lru_pages)
1461 for_each_zone(zone) {
1462 lru_pages += zone->nr_active;
1463 lru_pages += zone->nr_inactive;
1464 }
1465
1466 /* Force reclaiming mapped pages in the passes #3 and #4 */
1467 if (pass > 2) {
1468 sc.may_swap = 1;
1469 sc.swappiness = 100;
1470 }
1471
1472 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
1473 unsigned long nr_to_scan = nr_pages - ret;
1474
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001475 sc.nr_scanned = 0;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001476 ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
1477 if (ret >= nr_pages)
1478 goto out;
1479
1480 reclaim_state.reclaimed_slab = 0;
1481 shrink_slab(sc.nr_scanned, sc.gfp_mask, lru_pages);
1482 ret += reclaim_state.reclaimed_slab;
1483 if (ret >= nr_pages)
1484 goto out;
1485
1486 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
Andrew Morton3fcfab12006-10-19 23:28:16 -07001487 congestion_wait(WRITE, HZ / 10);
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001488 }
1489
1490 lru_pages = 0;
Rafael J. Wysocki248a0302006-03-22 00:09:04 -08001491 }
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001492
1493 /*
1494 * If ret = 0, we could not shrink LRUs, but there may be something
1495 * in slab caches
1496 */
1497 if (!ret)
1498 do {
1499 reclaim_state.reclaimed_slab = 0;
1500 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
1501 ret += reclaim_state.reclaimed_slab;
1502 } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
1503
1504out:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001505 current->reclaim_state = NULL;
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001506
Linus Torvalds1da177e2005-04-16 15:20:36 -07001507 return ret;
1508}
1509#endif
1510
1511#ifdef CONFIG_HOTPLUG_CPU
1512/* It's optimal to keep kswapds on the same CPUs as their memory, but
1513 not required for correctness. So if the last cpu in a node goes
1514 away, we get changed to run anywhere: as the first one comes back,
1515 restore their cpu bindings. */
Chandra Seetharaman9c7b2162006-06-27 02:54:07 -07001516static int __devinit cpu_callback(struct notifier_block *nfb,
Andrew Morton69e05942006-03-22 00:08:19 -08001517 unsigned long action, void *hcpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001518{
1519 pg_data_t *pgdat;
1520 cpumask_t mask;
1521
1522 if (action == CPU_ONLINE) {
KAMEZAWA Hiroyukiec936fc2006-03-27 01:15:59 -08001523 for_each_online_pgdat(pgdat) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524 mask = node_to_cpumask(pgdat->node_id);
1525 if (any_online_cpu(mask) != NR_CPUS)
1526 /* One of our CPUs online: restore mask */
1527 set_cpus_allowed(pgdat->kswapd, mask);
1528 }
1529 }
1530 return NOTIFY_OK;
1531}
1532#endif /* CONFIG_HOTPLUG_CPU */
1533
Yasunori Goto3218ae12006-06-27 02:53:33 -07001534/*
1535 * This kswapd start function will be called by init and node-hot-add.
1536 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
1537 */
1538int kswapd_run(int nid)
1539{
1540 pg_data_t *pgdat = NODE_DATA(nid);
1541 int ret = 0;
1542
1543 if (pgdat->kswapd)
1544 return 0;
1545
1546 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
1547 if (IS_ERR(pgdat->kswapd)) {
1548 /* failure at boot is fatal */
1549 BUG_ON(system_state == SYSTEM_BOOTING);
1550 printk("Failed to start kswapd on node %d\n",nid);
1551 ret = -1;
1552 }
1553 return ret;
1554}
1555
Linus Torvalds1da177e2005-04-16 15:20:36 -07001556static int __init kswapd_init(void)
1557{
Yasunori Goto3218ae12006-06-27 02:53:33 -07001558 int nid;
Andrew Morton69e05942006-03-22 00:08:19 -08001559
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560 swap_setup();
Yasunori Goto3218ae12006-06-27 02:53:33 -07001561 for_each_online_node(nid)
1562 kswapd_run(nid);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001563 hotcpu_notifier(cpu_callback, 0);
1564 return 0;
1565}
1566
1567module_init(kswapd_init)
Christoph Lameter9eeff232006-01-18 17:42:31 -08001568
1569#ifdef CONFIG_NUMA
1570/*
1571 * Zone reclaim mode
1572 *
1573 * If non-zero call zone_reclaim when the number of free pages falls below
1574 * the watermarks.
Christoph Lameter9eeff232006-01-18 17:42:31 -08001575 */
1576int zone_reclaim_mode __read_mostly;
1577
Christoph Lameter1b2ffb72006-02-01 03:05:34 -08001578#define RECLAIM_OFF 0
1579#define RECLAIM_ZONE (1<<0) /* Run shrink_cache on the zone */
1580#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
1581#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
1582
Christoph Lameter9eeff232006-01-18 17:42:31 -08001583/*
Christoph Lametera92f7122006-02-01 03:05:32 -08001584 * Priority for ZONE_RECLAIM. This determines the fraction of pages
1585 * of a node considered for each zone_reclaim. 4 scans 1/16th of
1586 * a zone.
1587 */
1588#define ZONE_RECLAIM_PRIORITY 4
1589
Christoph Lameter9eeff232006-01-18 17:42:31 -08001590/*
Christoph Lameter96146342006-07-03 00:24:13 -07001591 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
1592 * occur.
1593 */
1594int sysctl_min_unmapped_ratio = 1;
1595
1596/*
Christoph Lameter0ff38492006-09-25 23:31:52 -07001597 * If the number of slab pages in a zone grows beyond this percentage then
1598 * slab reclaim needs to occur.
1599 */
1600int sysctl_min_slab_ratio = 5;
1601
1602/*
Christoph Lameter9eeff232006-01-18 17:42:31 -08001603 * Try to free up some pages from this zone through reclaim.
1604 */
Andrew Morton179e9632006-03-22 00:08:18 -08001605static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
Christoph Lameter9eeff232006-01-18 17:42:31 -08001606{
Christoph Lameter7fb2d462006-03-22 00:08:22 -08001607 /* Minimum pages needed in order to stay on node */
Andrew Morton69e05942006-03-22 00:08:19 -08001608 const unsigned long nr_pages = 1 << order;
Christoph Lameter9eeff232006-01-18 17:42:31 -08001609 struct task_struct *p = current;
1610 struct reclaim_state reclaim_state;
Christoph Lameter86959492006-03-22 00:08:18 -08001611 int priority;
Andrew Morton05ff5132006-03-22 00:08:20 -08001612 unsigned long nr_reclaimed = 0;
Andrew Morton179e9632006-03-22 00:08:18 -08001613 struct scan_control sc = {
1614 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
1615 .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
Andrew Morton69e05942006-03-22 00:08:19 -08001616 .swap_cluster_max = max_t(unsigned long, nr_pages,
1617 SWAP_CLUSTER_MAX),
Andrew Morton179e9632006-03-22 00:08:18 -08001618 .gfp_mask = gfp_mask,
Rafael J. Wysockid6277db2006-06-23 02:03:18 -07001619 .swappiness = vm_swappiness,
Andrew Morton179e9632006-03-22 00:08:18 -08001620 };
Christoph Lameter83e33a42006-09-25 23:31:53 -07001621 unsigned long slab_reclaimable;
Christoph Lameter9eeff232006-01-18 17:42:31 -08001622
1623 disable_swap_token();
Christoph Lameter9eeff232006-01-18 17:42:31 -08001624 cond_resched();
Christoph Lameterd4f77962006-02-24 13:04:22 -08001625 /*
1626 * We need to be able to allocate from the reserves for RECLAIM_SWAP
1627 * and we also need to be able to write out pages for RECLAIM_WRITE
1628 * and RECLAIM_SWAP.
1629 */
1630 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
Christoph Lameter9eeff232006-01-18 17:42:31 -08001631 reclaim_state.reclaimed_slab = 0;
1632 p->reclaim_state = &reclaim_state;
Christoph Lameterc84db232006-02-01 03:05:29 -08001633
Christoph Lameter0ff38492006-09-25 23:31:52 -07001634 if (zone_page_state(zone, NR_FILE_PAGES) -
1635 zone_page_state(zone, NR_FILE_MAPPED) >
1636 zone->min_unmapped_pages) {
1637 /*
1638 * Free memory by calling shrink zone with increasing
1639 * priorities until we have enough memory freed.
1640 */
1641 priority = ZONE_RECLAIM_PRIORITY;
1642 do {
Martin Bligh3bb1a852006-10-28 10:38:24 -07001643 note_zone_scanning_priority(zone, priority);
Christoph Lameter0ff38492006-09-25 23:31:52 -07001644 nr_reclaimed += shrink_zone(priority, zone, &sc);
1645 priority--;
1646 } while (priority >= 0 && nr_reclaimed < nr_pages);
1647 }
Christoph Lameterc84db232006-02-01 03:05:29 -08001648
Christoph Lameter83e33a42006-09-25 23:31:53 -07001649 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
1650 if (slab_reclaimable > zone->min_slab_pages) {
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08001651 /*
Christoph Lameter7fb2d462006-03-22 00:08:22 -08001652 * shrink_slab() does not currently allow us to determine how
Christoph Lameter0ff38492006-09-25 23:31:52 -07001653 * many pages were freed in this zone. So we take the current
1654 * number of slab pages and shake the slab until it is reduced
1655 * by the same nr_pages that we used for reclaiming unmapped
1656 * pages.
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08001657 *
Christoph Lameter0ff38492006-09-25 23:31:52 -07001658 * Note that shrink_slab will free memory on all zones and may
1659 * take a long time.
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08001660 */
Christoph Lameter0ff38492006-09-25 23:31:52 -07001661 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
Christoph Lameter83e33a42006-09-25 23:31:53 -07001662 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
1663 slab_reclaimable - nr_pages)
Christoph Lameter0ff38492006-09-25 23:31:52 -07001664 ;
Christoph Lameter83e33a42006-09-25 23:31:53 -07001665
1666 /*
1667 * Update nr_reclaimed by the number of slab pages we
1668 * reclaimed from this zone.
1669 */
1670 nr_reclaimed += slab_reclaimable -
1671 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
Christoph Lameter2a16e3f2006-02-01 03:05:35 -08001672 }
1673
Christoph Lameter9eeff232006-01-18 17:42:31 -08001674 p->reclaim_state = NULL;
Christoph Lameterd4f77962006-02-24 13:04:22 -08001675 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
Andrew Morton05ff5132006-03-22 00:08:20 -08001676 return nr_reclaimed >= nr_pages;
Christoph Lameter9eeff232006-01-18 17:42:31 -08001677}
Andrew Morton179e9632006-03-22 00:08:18 -08001678
1679int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
1680{
1681 cpumask_t mask;
1682 int node_id;
1683
1684 /*
Christoph Lameter0ff38492006-09-25 23:31:52 -07001685 * Zone reclaim reclaims unmapped file backed pages and
1686 * slab pages if we are over the defined limits.
Christoph Lameter34aa1332006-06-30 01:55:37 -07001687 *
Christoph Lameter96146342006-07-03 00:24:13 -07001688 * A small portion of unmapped file backed pages is needed for
1689 * file I/O otherwise pages read by file I/O will be immediately
1690 * thrown out if the zone is overallocated. So we do not reclaim
1691 * if less than a specified percentage of the zone is used by
1692 * unmapped file backed pages.
Andrew Morton179e9632006-03-22 00:08:18 -08001693 */
Christoph Lameter34aa1332006-06-30 01:55:37 -07001694 if (zone_page_state(zone, NR_FILE_PAGES) -
Christoph Lameter0ff38492006-09-25 23:31:52 -07001695 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
1696 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
1697 <= zone->min_slab_pages)
Christoph Lameter96146342006-07-03 00:24:13 -07001698 return 0;
Andrew Morton179e9632006-03-22 00:08:18 -08001699
1700 /*
1701 * Avoid concurrent zone reclaims, do not reclaim in a zone that does
1702 * not have reclaimable pages and if we should not delay the allocation
1703 * then do not scan.
1704 */
1705 if (!(gfp_mask & __GFP_WAIT) ||
1706 zone->all_unreclaimable ||
1707 atomic_read(&zone->reclaim_in_progress) > 0 ||
1708 (current->flags & PF_MEMALLOC))
1709 return 0;
1710
1711 /*
1712 * Only run zone reclaim on the local zone or on zones that do not
1713 * have associated processors. This will favor the local processor
1714 * over remote processors and spread off node memory allocations
1715 * as wide as possible.
1716 */
Christoph Lameter89fa3022006-09-25 23:31:55 -07001717 node_id = zone_to_nid(zone);
Andrew Morton179e9632006-03-22 00:08:18 -08001718 mask = node_to_cpumask(node_id);
1719 if (!cpus_empty(mask) && node_id != numa_node_id())
1720 return 0;
1721 return __zone_reclaim(zone, gfp_mask, order);
1722}
Christoph Lameter9eeff232006-01-18 17:42:31 -08001723#endif