blob: 710a20bb9749cc9c9397e85bb59643dc38c27698 [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/**
81 * put_pages_list(): release a list of pages
82 *
83 * Release a list of pages which are strung together on page.lru. Currently
84 * used by read_cache_pages() and related error recovery code.
85 *
86 * @pages: list of pages threaded on page->lru
87 */
88void put_pages_list(struct list_head *pages)
89{
90 while (!list_empty(pages)) {
91 struct page *victim;
92
93 victim = list_entry(pages->prev, struct page, lru);
94 list_del(&victim->lru);
95 page_cache_release(victim);
96 }
97}
98EXPORT_SYMBOL(put_pages_list);
99
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100/*
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700101 * pagevec_move_tail() must be called with IRQ disabled.
102 * Otherwise this may cause nasty races.
103 */
104static void pagevec_move_tail(struct pagevec *pvec)
105{
106 int i;
107 int pgmoved = 0;
108 struct zone *zone = NULL;
109
110 for (i = 0; i < pagevec_count(pvec); i++) {
111 struct page *page = pvec->pages[i];
112 struct zone *pagezone = page_zone(page);
113
114 if (pagezone != zone) {
115 if (zone)
116 spin_unlock(&zone->lru_lock);
117 zone = pagezone;
118 spin_lock(&zone->lru_lock);
119 }
120 if (PageLRU(page) && !PageActive(page)) {
121 list_move_tail(&page->lru, &zone->inactive_list);
122 pgmoved++;
123 }
124 }
125 if (zone)
126 spin_unlock(&zone->lru_lock);
127 __count_vm_events(PGROTATED, pgmoved);
128 release_pages(pvec->pages, pvec->nr, pvec->cold);
129 pagevec_reinit(pvec);
130}
131
132/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133 * Writeback is about to end against a page which has been marked for immediate
134 * reclaim. If it still appears to be reclaimable, move it to the tail of the
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700135 * inactive list.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136 *
137 * Returns zero if it cleared PG_writeback.
138 */
139int rotate_reclaimable_page(struct page *page)
140{
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700141 struct pagevec *pvec;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142 unsigned long flags;
143
144 if (PageLocked(page))
145 return 1;
146 if (PageDirty(page))
147 return 1;
148 if (PageActive(page))
149 return 1;
150 if (!PageLRU(page))
151 return 1;
152
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700153 page_cache_get(page);
154 local_irq_save(flags);
155 pvec = &__get_cpu_var(lru_rotate_pvecs);
156 if (!pagevec_add(pvec, page))
157 pagevec_move_tail(pvec);
158 local_irq_restore(flags);
159
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160 if (!test_clear_page_writeback(page))
161 BUG();
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700162
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163 return 0;
164}
165
166/*
167 * FIXME: speed this up?
168 */
Harvey Harrison920c7a52008-02-04 22:29:26 -0800169void activate_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170{
171 struct zone *zone = page_zone(page);
172
173 spin_lock_irq(&zone->lru_lock);
174 if (PageLRU(page) && !PageActive(page)) {
175 del_page_from_inactive_list(zone, page);
176 SetPageActive(page);
177 add_page_to_active_list(zone, page);
Christoph Lameterf8891e52006-06-30 01:55:45 -0700178 __count_vm_event(PGACTIVATE);
Balbir Singh66e17072008-02-07 00:13:56 -0800179 mem_cgroup_move_lists(page_get_page_cgroup(page), true);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180 }
181 spin_unlock_irq(&zone->lru_lock);
182}
183
184/*
185 * Mark a page as having seen activity.
186 *
187 * inactive,unreferenced -> inactive,referenced
188 * inactive,referenced -> active,unreferenced
189 * active,unreferenced -> active,referenced
190 */
Harvey Harrison920c7a52008-02-04 22:29:26 -0800191void mark_page_accessed(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192{
193 if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
194 activate_page(page);
195 ClearPageReferenced(page);
196 } else if (!PageReferenced(page)) {
197 SetPageReferenced(page);
198 }
199}
200
201EXPORT_SYMBOL(mark_page_accessed);
202
203/**
204 * lru_cache_add: add a page to the page lists
205 * @page: the page to add
206 */
Harvey Harrison920c7a52008-02-04 22:29:26 -0800207void lru_cache_add(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700208{
209 struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
210
211 page_cache_get(page);
212 if (!pagevec_add(pvec, page))
213 __pagevec_lru_add(pvec);
214 put_cpu_var(lru_add_pvecs);
215}
216
Harvey Harrison920c7a52008-02-04 22:29:26 -0800217void lru_cache_add_active(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218{
219 struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
220
221 page_cache_get(page);
222 if (!pagevec_add(pvec, page))
223 __pagevec_lru_add_active(pvec);
224 put_cpu_var(lru_add_active_pvecs);
225}
226
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700227/*
228 * Drain pages out of the cpu's pagevecs.
229 * Either "cpu" is the current CPU, and preemption has already been
230 * disabled; or "cpu" is being hot-unplugged, and is already dead.
231 */
232static void drain_cpu_pagevecs(int cpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233{
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700234 struct pagevec *pvec;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700235
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700236 pvec = &per_cpu(lru_add_pvecs, cpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700237 if (pagevec_count(pvec))
238 __pagevec_lru_add(pvec);
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700239
Andrew Morton80bfed92006-01-06 00:11:14 -0800240 pvec = &per_cpu(lru_add_active_pvecs, cpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700241 if (pagevec_count(pvec))
242 __pagevec_lru_add_active(pvec);
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700243
244 pvec = &per_cpu(lru_rotate_pvecs, cpu);
245 if (pagevec_count(pvec)) {
246 unsigned long flags;
247
248 /* No harm done if a racing interrupt already did this */
249 local_irq_save(flags);
250 pagevec_move_tail(pvec);
251 local_irq_restore(flags);
252 }
Andrew Morton80bfed92006-01-06 00:11:14 -0800253}
254
255void lru_add_drain(void)
256{
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700257 drain_cpu_pagevecs(get_cpu());
Andrew Morton80bfed92006-01-06 00:11:14 -0800258 put_cpu();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700259}
260
Nick Piggin053837f2006-01-18 17:42:27 -0800261#ifdef CONFIG_NUMA
David Howellsc4028952006-11-22 14:57:56 +0000262static void lru_add_drain_per_cpu(struct work_struct *dummy)
Nick Piggin053837f2006-01-18 17:42:27 -0800263{
264 lru_add_drain();
265}
266
267/*
268 * Returns 0 for success
269 */
270int lru_add_drain_all(void)
271{
David Howellsc4028952006-11-22 14:57:56 +0000272 return schedule_on_each_cpu(lru_add_drain_per_cpu);
Nick Piggin053837f2006-01-18 17:42:27 -0800273}
274
275#else
276
277/*
278 * Returns 0 for success
279 */
280int lru_add_drain_all(void)
281{
282 lru_add_drain();
283 return 0;
284}
285#endif
286
Linus Torvalds1da177e2005-04-16 15:20:36 -0700287/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700288 * Batched page_cache_release(). Decrement the reference count on all the
289 * passed pages. If it fell to zero then remove the page from the LRU and
290 * free it.
291 *
292 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
293 * for the remainder of the operation.
294 *
295 * The locking in this function is against shrink_cache(): we recheck the
296 * page count inside the lock to see whether shrink_cache grabbed the page
297 * via the LRU. If it did, give up: shrink_cache will free it.
298 */
299void release_pages(struct page **pages, int nr, int cold)
300{
301 int i;
302 struct pagevec pages_to_free;
303 struct zone *zone = NULL;
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700304 unsigned long uninitialized_var(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700305
306 pagevec_init(&pages_to_free, cold);
307 for (i = 0; i < nr; i++) {
308 struct page *page = pages[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700309
Nick Piggin8519fb32006-02-07 12:58:52 -0800310 if (unlikely(PageCompound(page))) {
311 if (zone) {
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700312 spin_unlock_irqrestore(&zone->lru_lock, flags);
Nick Piggin8519fb32006-02-07 12:58:52 -0800313 zone = NULL;
314 }
315 put_compound_page(page);
316 continue;
317 }
318
Nick Pigginb5810032005-10-29 18:16:12 -0700319 if (!put_page_testzero(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 continue;
321
Nick Piggin46453a62006-03-22 00:07:58 -0800322 if (PageLRU(page)) {
323 struct zone *pagezone = page_zone(page);
324 if (pagezone != zone) {
325 if (zone)
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700326 spin_unlock_irqrestore(&zone->lru_lock,
327 flags);
Nick Piggin46453a62006-03-22 00:07:58 -0800328 zone = pagezone;
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700329 spin_lock_irqsave(&zone->lru_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330 }
Nick Piggin725d7042006-09-25 23:30:55 -0700331 VM_BUG_ON(!PageLRU(page));
Nick Piggin67453912006-03-22 00:08:00 -0800332 __ClearPageLRU(page);
Nick Piggin46453a62006-03-22 00:07:58 -0800333 del_page_from_lru(zone, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700334 }
Nick Piggin46453a62006-03-22 00:07:58 -0800335
336 if (!pagevec_add(&pages_to_free, page)) {
337 if (zone) {
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700338 spin_unlock_irqrestore(&zone->lru_lock, flags);
Nick Piggin46453a62006-03-22 00:07:58 -0800339 zone = NULL;
340 }
341 __pagevec_free(&pages_to_free);
342 pagevec_reinit(&pages_to_free);
343 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344 }
345 if (zone)
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700346 spin_unlock_irqrestore(&zone->lru_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347
348 pagevec_free(&pages_to_free);
349}
350
351/*
352 * The pages which we're about to release may be in the deferred lru-addition
353 * queues. That would prevent them from really being freed right now. That's
354 * OK from a correctness point of view but is inefficient - those pages may be
355 * cache-warm and we want to give them back to the page allocator ASAP.
356 *
357 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
358 * and __pagevec_lru_add_active() call release_pages() directly to avoid
359 * mutual recursion.
360 */
361void __pagevec_release(struct pagevec *pvec)
362{
363 lru_add_drain();
364 release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
365 pagevec_reinit(pvec);
366}
367
Steve French7f285702005-11-01 10:22:55 -0800368EXPORT_SYMBOL(__pagevec_release);
369
Linus Torvalds1da177e2005-04-16 15:20:36 -0700370/*
371 * pagevec_release() for pages which are known to not be on the LRU
372 *
373 * This function reinitialises the caller's pagevec.
374 */
375void __pagevec_release_nonlru(struct pagevec *pvec)
376{
377 int i;
378 struct pagevec pages_to_free;
379
380 pagevec_init(&pages_to_free, pvec->cold);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381 for (i = 0; i < pagevec_count(pvec); i++) {
382 struct page *page = pvec->pages[i];
383
Nick Piggin725d7042006-09-25 23:30:55 -0700384 VM_BUG_ON(PageLRU(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700385 if (put_page_testzero(page))
386 pagevec_add(&pages_to_free, page);
387 }
388 pagevec_free(&pages_to_free);
389 pagevec_reinit(pvec);
390}
391
392/*
393 * Add the passed pages to the LRU, then drop the caller's refcount
394 * on them. Reinitialises the caller's pagevec.
395 */
396void __pagevec_lru_add(struct pagevec *pvec)
397{
398 int i;
399 struct zone *zone = NULL;
400
401 for (i = 0; i < pagevec_count(pvec); i++) {
402 struct page *page = pvec->pages[i];
403 struct zone *pagezone = page_zone(page);
404
405 if (pagezone != zone) {
406 if (zone)
407 spin_unlock_irq(&zone->lru_lock);
408 zone = pagezone;
409 spin_lock_irq(&zone->lru_lock);
410 }
Nick Piggin725d7042006-09-25 23:30:55 -0700411 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800412 SetPageLRU(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413 add_page_to_inactive_list(zone, page);
414 }
415 if (zone)
416 spin_unlock_irq(&zone->lru_lock);
417 release_pages(pvec->pages, pvec->nr, pvec->cold);
418 pagevec_reinit(pvec);
419}
420
421EXPORT_SYMBOL(__pagevec_lru_add);
422
423void __pagevec_lru_add_active(struct pagevec *pvec)
424{
425 int i;
426 struct zone *zone = NULL;
427
428 for (i = 0; i < pagevec_count(pvec); i++) {
429 struct page *page = pvec->pages[i];
430 struct zone *pagezone = page_zone(page);
431
432 if (pagezone != zone) {
433 if (zone)
434 spin_unlock_irq(&zone->lru_lock);
435 zone = pagezone;
436 spin_lock_irq(&zone->lru_lock);
437 }
Nick Piggin725d7042006-09-25 23:30:55 -0700438 VM_BUG_ON(PageLRU(page));
Nick Piggin8d438f92006-03-22 00:07:59 -0800439 SetPageLRU(page);
Nick Piggin725d7042006-09-25 23:30:55 -0700440 VM_BUG_ON(PageActive(page));
Nick Piggin4c84cac2006-03-22 00:08:00 -0800441 SetPageActive(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442 add_page_to_active_list(zone, page);
443 }
444 if (zone)
445 spin_unlock_irq(&zone->lru_lock);
446 release_pages(pvec->pages, pvec->nr, pvec->cold);
447 pagevec_reinit(pvec);
448}
449
450/*
451 * Try to drop buffers from the pages in a pagevec
452 */
453void pagevec_strip(struct pagevec *pvec)
454{
455 int i;
456
457 for (i = 0; i < pagevec_count(pvec); i++) {
458 struct page *page = pvec->pages[i];
459
460 if (PagePrivate(page) && !TestSetPageLocked(page)) {
Christoph Lameter5b40dc72006-03-16 23:04:07 -0800461 if (PagePrivate(page))
462 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700463 unlock_page(page);
464 }
465 }
466}
467
468/**
469 * pagevec_lookup - gang pagecache lookup
470 * @pvec: Where the resulting pages are placed
471 * @mapping: The address_space to search
472 * @start: The starting page index
473 * @nr_pages: The maximum number of pages
474 *
475 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
476 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
477 * reference against the pages in @pvec.
478 *
479 * The search returns a group of mapping-contiguous pages with ascending
480 * indexes. There may be holes in the indices due to not-present pages.
481 *
482 * pagevec_lookup() returns the number of pages which were found.
483 */
484unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
485 pgoff_t start, unsigned nr_pages)
486{
487 pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
488 return pagevec_count(pvec);
489}
490
Christoph Hellwig78539fd2006-01-11 20:47:41 +1100491EXPORT_SYMBOL(pagevec_lookup);
492
Linus Torvalds1da177e2005-04-16 15:20:36 -0700493unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
494 pgoff_t *index, int tag, unsigned nr_pages)
495{
496 pvec->nr = find_get_pages_tag(mapping, index, tag,
497 nr_pages, pvec->pages);
498 return pagevec_count(pvec);
499}
500
Steve French7f285702005-11-01 10:22:55 -0800501EXPORT_SYMBOL(pagevec_lookup_tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700502
503#ifdef CONFIG_SMP
504/*
505 * We tolerate a little inaccuracy to avoid ping-ponging the counter between
506 * CPUs
507 */
508#define ACCT_THRESHOLD max(16, NR_CPUS * 2)
509
510static DEFINE_PER_CPU(long, committed_space) = 0;
511
512void vm_acct_memory(long pages)
513{
514 long *local;
515
516 preempt_disable();
517 local = &__get_cpu_var(committed_space);
518 *local += pages;
519 if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
520 atomic_add(*local, &vm_committed_space);
521 *local = 0;
522 }
523 preempt_enable();
524}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525
526#ifdef CONFIG_HOTPLUG_CPU
Linus Torvalds1da177e2005-04-16 15:20:36 -0700527
528/* Drop the CPU's cached committed space back into the central pool. */
529static int cpu_swap_callback(struct notifier_block *nfb,
530 unsigned long action,
531 void *hcpu)
532{
533 long *committed;
534
535 committed = &per_cpu(committed_space, (long)hcpu);
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -0700536 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700537 atomic_add(*committed, &vm_committed_space);
538 *committed = 0;
Hisashi Hifumi902aaed2007-10-16 01:24:52 -0700539 drain_cpu_pagevecs((long)hcpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700540 }
541 return NOTIFY_OK;
542}
543#endif /* CONFIG_HOTPLUG_CPU */
544#endif /* CONFIG_SMP */
545
Linus Torvalds1da177e2005-04-16 15:20:36 -0700546/*
547 * Perform any setup for the swap system
548 */
549void __init swap_setup(void)
550{
551 unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
552
Peter Zijlstrae0bf68d2007-10-16 23:25:46 -0700553#ifdef CONFIG_SWAP
554 bdi_init(swapper_space.backing_dev_info);
555#endif
556
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557 /* Use a smaller cluster for small-memory machines */
558 if (megs < 16)
559 page_cluster = 2;
560 else
561 page_cluster = 3;
562 /*
563 * Right now other parts of the system means that we
564 * _really_ don't want to cluster much more
565 */
Ingo Molnar023160672006-12-06 20:38:17 -0800566#ifdef CONFIG_HOTPLUG_CPU
Linus Torvalds1da177e2005-04-16 15:20:36 -0700567 hotcpu_notifier(cpu_swap_callback, 0);
Ingo Molnar023160672006-12-06 20:38:17 -0800568#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700569}