blob: 91e194445a5eae53ee3ae97e3f616cdcb7d442d0 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/mm/swap.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 */
6
7/*
Simon Arlott183ff222007-10-20 01:27:18 +02008 * This file contains the default values for the operation of the
Linus Torvalds1da177e2005-04-16 15:20:36 -07009 * Linux VM subsystem. Fine-tuning documentation can be found in
10 * Documentation/sysctl/vm.txt.
11 * Started 18.12.91
12 * Swap aging added 23.2.95, Stephen Tweedie.
13 * Buffermem limits added 12.3.98, Rik van Riel.
14 */
15
16#include <linux/mm.h>
17#include <linux/sched.h>
18#include <linux/kernel_stat.h>
19#include <linux/swap.h>
20#include <linux/mman.h>
21#include <linux/pagemap.h>
22#include <linux/pagevec.h>
23#include <linux/init.h>
24#include <linux/module.h>
25#include <linux/mm_inline.h>
26#include <linux/buffer_head.h> /* for try_to_release_page() */
Linus Torvalds1da177e2005-04-16 15:20:36 -070027#include <linux/percpu_counter.h>
28#include <linux/percpu.h>
29#include <linux/cpu.h>
30#include <linux/notifier.h>
Peter Zijlstrae0bf68d2007-10-16 23:25:46 -070031#include <linux/backing-dev.h>
Balbir Singh66e17072008-02-07 00:13:56 -080032#include <linux/memcontrol.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070033
34/* How many pages do we try to swap or page in/out together? */
35int page_cluster;
36
Hisashi Hifumi902aaed2007-10-16 01:24:52 -070037static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
38static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
39static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs) = { 0, };
40
Adrian Bunkb2213852006-09-25 23:31:02 -070041/*
42 * This path almost never happens for VM activity - pages are normally
43 * freed via pagevecs. But it gets used by networking.
44 */
Harvey Harrison920c7a52008-02-04 22:29:26 -080045static void __page_cache_release(struct page *page)
Adrian Bunkb2213852006-09-25 23:31:02 -070046{
47 if (PageLRU(page)) {
48 unsigned long flags;
49 struct zone *zone = page_zone(page);
50
51 spin_lock_irqsave(&zone->lru_lock, flags);
52 VM_BUG_ON(!PageLRU(page));
53 __ClearPageLRU(page);
54 del_page_from_lru(zone, page);
55 spin_unlock_irqrestore(&zone->lru_lock, flags);
56 }
57 free_hot_page(page);
58}
59
Nick Piggin8519fb32006-02-07 12:58:52 -080060static void put_compound_page(struct page *page)
61{
Christoph Lameterd85f3382007-05-06 14:49:39 -070062 page = compound_head(page);
Nick Piggin8519fb32006-02-07 12:58:52 -080063 if (put_page_testzero(page)) {
Andy Whitcroft33f2ef82006-12-06 20:33:32 -080064 compound_page_dtor *dtor;
Nick Piggin8519fb32006-02-07 12:58:52 -080065
Andy Whitcroft33f2ef82006-12-06 20:33:32 -080066 dtor = get_compound_page_dtor(page);
Nick Piggin8519fb32006-02-07 12:58:52 -080067 (*dtor)(page);
68 }
69}
70
Linus Torvalds1da177e2005-04-16 15:20:36 -070071void put_page(struct page *page)
72{
Nick Piggin8519fb32006-02-07 12:58:52 -080073 if (unlikely(PageCompound(page)))
74 put_compound_page(page);
75 else if (put_page_testzero(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -070076 __page_cache_release(page);
77}
78EXPORT_SYMBOL(put_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070079
Alexander Zarochentsev1d7ea732006-08-13 23:24:27 -070080/**
Randy Dunlap76824862008-03-19 17:00:40 -070081 * put_pages_list() - release a list of pages
82 * @pages: list of pages threaded on page->lru
Alexander Zarochentsev1d7ea732006-08-13 23:24:27 -070083 *
84 * Release a list of pages which are strung together on page.lru. Currently
85 * used by read_cache_pages() and related error recovery code.
Alexander Zarochentsev1d7ea732006-08-13 23:24:27 -070086 */
87void put_pages_list(struct list_head *pages)
88{
89 while (!list_empty(pages)) {
90 struct page *victim;
91
92 victim = list_entry(pages->prev, struct page, lru);
93 list_del(&victim->lru);
94 page_cache_release(victim);
95 }
96}
97EXPORT_SYMBOL(put_pages_list);
98
Linus Torvalds1da177e2005-04-16 15:20:36 -070099/*
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700100 * pagevec_move_tail() must be called with IRQ disabled.
101 * Otherwise this may cause nasty races.
102 */
103static void pagevec_move_tail(struct pagevec *pvec)
104{
105 int i;
106 int pgmoved = 0;
107 struct zone *zone = NULL;
108
109 for (i = 0; i < pagevec_count(pvec); i++) {
110 struct page *page = pvec->pages[i];
111 struct zone *pagezone = page_zone(page);
112
113 if (pagezone != zone) {
114 if (zone)
115 spin_unlock(&zone->lru_lock);
116 zone = pagezone;
117 spin_lock(&zone->lru_lock);
118 }
119 if (PageLRU(page) && !PageActive(page)) {
120 list_move_tail(&page->lru, &zone->inactive_list);
121 pgmoved++;
122 }
123 }
124 if (zone)
125 spin_unlock(&zone->lru_lock);
126 __count_vm_events(PGROTATED, pgmoved);
127 release_pages(pvec->pages, pvec->nr, pvec->cold);
128 pagevec_reinit(pvec);
129}
130
131/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132 * Writeback is about to end against a page which has been marked for immediate
133 * reclaim. If it still appears to be reclaimable, move it to the tail of the
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700134 * inactive list.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135 */
Miklos Szerediac6aadb2008-04-28 02:12:38 -0700136void rotate_reclaimable_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700137{
Miklos Szerediac6aadb2008-04-28 02:12:38 -0700138 if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
139 PageLRU(page)) {
140 struct pagevec *pvec;
141 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142
Miklos Szerediac6aadb2008-04-28 02:12:38 -0700143 page_cache_get(page);
144 local_irq_save(flags);
145 pvec = &__get_cpu_var(lru_rotate_pvecs);
146 if (!pagevec_add(pvec, page))
147 pagevec_move_tail(pvec);
148 local_irq_restore(flags);
149 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150}
151
152/*
153 * FIXME: speed this up?
154 */
Harvey Harrison920c7a52008-02-04 22:29:26 -0800155void activate_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156{
157 struct zone *zone = page_zone(page);
158
159 spin_lock_irq(&zone->lru_lock);
160 if (PageLRU(page) && !PageActive(page)) {
161 del_page_from_inactive_list(zone, page);
162 SetPageActive(page);
163 add_page_to_active_list(zone, page);
Christoph Lameterf8891e52006-06-30 01:55:45 -0700164 __count_vm_event(PGACTIVATE);
Hugh Dickins427d5412008-03-04 14:29:03 -0800165 mem_cgroup_move_lists(page, true);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166 }
167 spin_unlock_irq(&zone->lru_lock);
168}
169
170/*
171 * Mark a page as having seen activity.
172 *
173 * inactive,unreferenced -> inactive,referenced
174 * inactive,referenced -> active,unreferenced
175 * active,unreferenced -> active,referenced
176 */
Harvey Harrison920c7a52008-02-04 22:29:26 -0800177void mark_page_accessed(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178{
179 if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
180 activate_page(page);
181 ClearPageReferenced(page);
182 } else if (!PageReferenced(page)) {
183 SetPageReferenced(page);
184 }
185}
186
187EXPORT_SYMBOL(mark_page_accessed);
188
189/**
190 * lru_cache_add: add a page to the page lists
191 * @page: the page to add
192 */
Harvey Harrison920c7a52008-02-04 22:29:26 -0800193void lru_cache_add(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194{
195 struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
196
197 page_cache_get(page);
198 if (!pagevec_add(pvec, page))
199 __pagevec_lru_add(pvec);
200 put_cpu_var(lru_add_pvecs);
201}
202
Harvey Harrison920c7a52008-02-04 22:29:26 -0800203void lru_cache_add_active(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204{
205 struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
206
207 page_cache_get(page);
208 if (!pagevec_add(pvec, page))
209 __pagevec_lru_add_active(pvec);
210 put_cpu_var(lru_add_active_pvecs);
211}
212
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700213/*
214 * Drain pages out of the cpu's pagevecs.
215 * Either "cpu" is the current CPU, and preemption has already been
216 * disabled; or "cpu" is being hot-unplugged, and is already dead.
217 */
218static void drain_cpu_pagevecs(int cpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219{
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700220 struct pagevec *pvec;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700221
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700222 pvec = &per_cpu(lru_add_pvecs, cpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700223 if (pagevec_count(pvec))
224 __pagevec_lru_add(pvec);
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700225
Andrew Morton80bfed92006-01-06 00:11:14 -0800226 pvec = &per_cpu(lru_add_active_pvecs, cpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700227 if (pagevec_count(pvec))
228 __pagevec_lru_add_active(pvec);
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700229
230 pvec = &per_cpu(lru_rotate_pvecs, cpu);
231 if (pagevec_count(pvec)) {
232 unsigned long flags;
233
234 /* No harm done if a racing interrupt already did this */
235 local_irq_save(flags);
236 pagevec_move_tail(pvec);
237 local_irq_restore(flags);
238 }
Andrew Morton80bfed92006-01-06 00:11:14 -0800239}
240
241void lru_add_drain(void)
242{
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700243 drain_cpu_pagevecs(get_cpu());
Andrew Morton80bfed92006-01-06 00:11:14 -0800244 put_cpu();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700245}
246
Nick Piggin053837f2006-01-18 17:42:27 -0800247#ifdef CONFIG_NUMA
David Howellsc4028952006-11-22 14:57:56 +0000248static void lru_add_drain_per_cpu(struct work_struct *dummy)
Nick Piggin053837f2006-01-18 17:42:27 -0800249{
250 lru_add_drain();
251}
252
253/*
254 * Returns 0 for success
255 */
256int lru_add_drain_all(void)
257{
David Howellsc4028952006-11-22 14:57:56 +0000258 return schedule_on_each_cpu(lru_add_drain_per_cpu);
Nick Piggin053837f2006-01-18 17:42:27 -0800259}
260
261#else
262
263/*
264 * Returns 0 for success
265 */
266int lru_add_drain_all(void)
267{
268 lru_add_drain();
269 return 0;
270}
271#endif
272
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700274 * Batched page_cache_release(). Decrement the reference count on all the
275 * passed pages. If it fell to zero then remove the page from the LRU and
276 * free it.
277 *
278 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
279 * for the remainder of the operation.
280 *
281 * The locking in this function is against shrink_cache(): we recheck the
282 * page count inside the lock to see whether shrink_cache grabbed the page
283 * via the LRU. If it did, give up: shrink_cache will free it.
284 */
285void release_pages(struct page **pages, int nr, int cold)
286{
287 int i;
288 struct pagevec pages_to_free;
289 struct zone *zone = NULL;
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700290 unsigned long uninitialized_var(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291
292 pagevec_init(&pages_to_free, cold);
293 for (i = 0; i < nr; i++) {
294 struct page *page = pages[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700295
Nick Piggin8519fb32006-02-07 12:58:52 -0800296 if (unlikely(PageCompound(page))) {
297 if (zone) {
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700298 spin_unlock_irqrestore(&zone->lru_lock, flags);
Nick Piggin8519fb32006-02-07 12:58:52 -0800299 zone = NULL;
300 }
301 put_compound_page(page);
302 continue;
303 }
304
Nick Pigginb5810032005-10-29 18:16:12 -0700305 if (!put_page_testzero(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306 continue;
307
Nick Piggin46453a62006-03-22 00:07:58 -0800308 if (PageLRU(page)) {
309 struct zone *pagezone = page_zone(page);
310 if (pagezone != zone) {
311 if (zone)
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700312 spin_unlock_irqrestore(&zone->lru_lock,
313 flags);
Nick Piggin46453a62006-03-22 00:07:58 -0800314 zone = pagezone;
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700315 spin_lock_irqsave(&zone->lru_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316 }
Nick Piggin725d7042006-09-25 23:30:55 -0700317 VM_BUG_ON(!PageLRU(page));
Nick Piggin67453912006-03-22 00:08:00 -0800318 __ClearPageLRU(page);
Nick Piggin46453a62006-03-22 00:07:58 -0800319 del_page_from_lru(zone, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 }
Nick Piggin46453a62006-03-22 00:07:58 -0800321
322 if (!pagevec_add(&pages_to_free, page)) {
323 if (zone) {
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700324 spin_unlock_irqrestore(&zone->lru_lock, flags);
Nick Piggin46453a62006-03-22 00:07:58 -0800325 zone = NULL;
326 }
327 __pagevec_free(&pages_to_free);
328 pagevec_reinit(&pages_to_free);
329 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330 }
331 if (zone)
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700332 spin_unlock_irqrestore(&zone->lru_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700333
334 pagevec_free(&pages_to_free);
335}
336
337/*
338 * The pages which we're about to release may be in the deferred lru-addition
339 * queues. That would prevent them from really being freed right now. That's
340 * OK from a correctness point of view but is inefficient - those pages may be
341 * cache-warm and we want to give them back to the page allocator ASAP.
342 *
343 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
344 * and __pagevec_lru_add_active() call release_pages() directly to avoid
345 * mutual recursion.
346 */
347void __pagevec_release(struct pagevec *pvec)
348{
349 lru_add_drain();
350 release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
351 pagevec_reinit(pvec);
352}
353
Steve French7f285702005-11-01 10:22:55 -0800354EXPORT_SYMBOL(__pagevec_release);
355
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356/*
357 * pagevec_release() for pages which are known to not be on the LRU
358 *
359 * This function reinitialises the caller's pagevec.
360 */
361void __pagevec_release_nonlru(struct pagevec *pvec)
362{
363 int i;
364 struct pagevec pages_to_free;
365
366 pagevec_init(&pages_to_free, pvec->cold);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 for (i = 0; i < pagevec_count(pvec); i++) {
368 struct page *page = pvec->pages[i];
369
Nick Piggin725d7042006-09-25 23:30:55 -0700370 VM_BUG_ON(PageLRU(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700371 if (put_page_testzero(page))
372 pagevec_add(&pages_to_free, page);
373 }
374 pagevec_free(&pages_to_free);
375 pagevec_reinit(pvec);
376}
377
378/*
379 * Add the passed pages to the LRU, then drop the caller's refcount
380 * on them. Reinitialises the caller's pagevec.
381 */
382void __pagevec_lru_add(struct pagevec *pvec)
383{
384 int i;
385 struct zone *zone = NULL;
386
387 for (i = 0; i < pagevec_count(pvec); i++) {
388 struct page *page = pvec->pages[i];
389 struct zone *pagezone = page_zone(page);
390
391 if (pagezone != zone) {
392 if (zone)
393 spin_unlock_irq(&zone->lru_lock);
394 zone = pagezone;
395 spin_lock_irq(&zone->lru_lock);
396 }
Nick Piggin725d7042006-09-25 23:30:55 -0700397 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800398 SetPageLRU(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399 add_page_to_inactive_list(zone, page);
400 }
401 if (zone)
402 spin_unlock_irq(&zone->lru_lock);
403 release_pages(pvec->pages, pvec->nr, pvec->cold);
404 pagevec_reinit(pvec);
405}
406
407EXPORT_SYMBOL(__pagevec_lru_add);
408
409void __pagevec_lru_add_active(struct pagevec *pvec)
410{
411 int i;
412 struct zone *zone = NULL;
413
414 for (i = 0; i < pagevec_count(pvec); i++) {
415 struct page *page = pvec->pages[i];
416 struct zone *pagezone = page_zone(page);
417
418 if (pagezone != zone) {
419 if (zone)
420 spin_unlock_irq(&zone->lru_lock);
421 zone = pagezone;
422 spin_lock_irq(&zone->lru_lock);
423 }
Nick Piggin725d7042006-09-25 23:30:55 -0700424 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800425 SetPageLRU(page);
Nick Piggin725d7042006-09-25 23:30:55 -0700426 VM_BUG_ON(PageActive(page));
Nick Piggin4c84cac2006-03-22 00:08:00 -0800427 SetPageActive(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700428 add_page_to_active_list(zone, page);
429 }
430 if (zone)
431 spin_unlock_irq(&zone->lru_lock);
432 release_pages(pvec->pages, pvec->nr, pvec->cold);
433 pagevec_reinit(pvec);
434}
435
436/*
437 * Try to drop buffers from the pages in a pagevec
438 */
439void pagevec_strip(struct pagevec *pvec)
440{
441 int i;
442
443 for (i = 0; i < pagevec_count(pvec); i++) {
444 struct page *page = pvec->pages[i];
445
446 if (PagePrivate(page) && !TestSetPageLocked(page)) {
Christoph Lameter5b40dc72006-03-16 23:04:07 -0800447 if (PagePrivate(page))
448 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449 unlock_page(page);
450 }
451 }
452}
453
454/**
455 * pagevec_lookup - gang pagecache lookup
456 * @pvec: Where the resulting pages are placed
457 * @mapping: The address_space to search
458 * @start: The starting page index
459 * @nr_pages: The maximum number of pages
460 *
461 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
462 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
463 * reference against the pages in @pvec.
464 *
465 * The search returns a group of mapping-contiguous pages with ascending
466 * indexes. There may be holes in the indices due to not-present pages.
467 *
468 * pagevec_lookup() returns the number of pages which were found.
469 */
470unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
471 pgoff_t start, unsigned nr_pages)
472{
473 pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
474 return pagevec_count(pvec);
475}
476
Christoph Hellwig78539fd2006-01-11 20:47:41 +1100477EXPORT_SYMBOL(pagevec_lookup);
478
Linus Torvalds1da177e2005-04-16 15:20:36 -0700479unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
480 pgoff_t *index, int tag, unsigned nr_pages)
481{
482 pvec->nr = find_get_pages_tag(mapping, index, tag,
483 nr_pages, pvec->pages);
484 return pagevec_count(pvec);
485}
486
Steve French7f285702005-11-01 10:22:55 -0800487EXPORT_SYMBOL(pagevec_lookup_tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700488
489#ifdef CONFIG_SMP
490/*
491 * We tolerate a little inaccuracy to avoid ping-ponging the counter between
492 * CPUs
493 */
494#define ACCT_THRESHOLD max(16, NR_CPUS * 2)
495
496static DEFINE_PER_CPU(long, committed_space) = 0;
497
498void vm_acct_memory(long pages)
499{
500 long *local;
501
502 preempt_disable();
503 local = &__get_cpu_var(committed_space);
504 *local += pages;
505 if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
506 atomic_add(*local, &vm_committed_space);
507 *local = 0;
508 }
509 preempt_enable();
510}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511
512#ifdef CONFIG_HOTPLUG_CPU
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513
514/* Drop the CPU's cached committed space back into the central pool. */
515static int cpu_swap_callback(struct notifier_block *nfb,
516 unsigned long action,
517 void *hcpu)
518{
519 long *committed;
520
521 committed = &per_cpu(committed_space, (long)hcpu);
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -0700522 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700523 atomic_add(*committed, &vm_committed_space);
524 *committed = 0;
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700525 drain_cpu_pagevecs((long)hcpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700526 }
527 return NOTIFY_OK;
528}
529#endif /* CONFIG_HOTPLUG_CPU */
530#endif /* CONFIG_SMP */
531
Linus Torvalds1da177e2005-04-16 15:20:36 -0700532/*
533 * Perform any setup for the swap system
534 */
535void __init swap_setup(void)
536{
537 unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
538
Peter Zijlstrae0bf68d2007-10-16 23:25:46 -0700539#ifdef CONFIG_SWAP
540 bdi_init(swapper_space.backing_dev_info);
541#endif
542
Linus Torvalds1da177e2005-04-16 15:20:36 -0700543 /* Use a smaller cluster for small-memory machines */
544 if (megs < 16)
545 page_cluster = 2;
546 else
547 page_cluster = 3;
548 /*
549 * Right now other parts of the system means that we
550 * _really_ don't want to cluster much more
551 */
Ingo Molnar023160672006-12-06 20:38:17 -0800552#ifdef CONFIG_HOTPLUG_CPU
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 hotcpu_notifier(cpu_swap_callback, 0);
Ingo Molnar023160672006-12-06 20:38:17 -0800554#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555}