blob: da7d35ea51034796e27fc7274a382c338c5a03e8 [file] [log] [blame]
Mel Gorman748446b2010-05-24 14:32:27 -07001/*
2 * linux/mm/compaction.c
3 *
4 * Memory compaction for the reduction of external fragmentation. Note that
5 * this heavily depends upon page migration to do all the real heavy
6 * lifting
7 *
8 * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
9 */
10#include <linux/swap.h>
11#include <linux/migrate.h>
12#include <linux/compaction.h>
13#include <linux/mm_inline.h>
14#include <linux/backing-dev.h>
Mel Gorman76ab0f52010-05-24 14:32:28 -070015#include <linux/sysctl.h>
Mel Gormaned4a6d72010-05-24 14:32:29 -070016#include <linux/sysfs.h>
Mel Gorman748446b2010-05-24 14:32:27 -070017#include "internal.h"
18
Michal Nazarewiczff9543f2011-12-29 13:09:50 +010019#if defined CONFIG_COMPACTION || defined CONFIG_CMA
20
Mel Gormanb7aba692011-01-13 15:45:54 -080021#define CREATE_TRACE_POINTS
22#include <trace/events/compaction.h>
23
Mel Gorman748446b2010-05-24 14:32:27 -070024static unsigned long release_freepages(struct list_head *freelist)
25{
26 struct page *page, *next;
27 unsigned long count = 0;
28
29 list_for_each_entry_safe(page, next, freelist, lru) {
30 list_del(&page->lru);
31 __free_page(page);
32 count++;
33 }
34
35 return count;
36}
37
Michal Nazarewiczff9543f2011-12-29 13:09:50 +010038static void map_pages(struct list_head *list)
39{
40 struct page *page;
41
42 list_for_each_entry(page, list, lru) {
43 arch_alloc_page(page, 0);
44 kernel_map_pages(page, 1, 1);
45 }
46}
47
Michal Nazarewicz47118af2011-12-29 13:09:50 +010048static inline bool migrate_async_suitable(int migratetype)
49{
50 return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
51}
52
Michal Nazarewicz85aa1252012-01-30 13:24:03 +010053/*
54 * Isolate free pages onto a private freelist. Caller must hold zone->lock.
55 * If @strict is true, will abort returning 0 on any invalid PFNs or non-free
56 * pages inside of the pageblock (even though it may still end up isolating
57 * some pages).
58 */
59static unsigned long isolate_freepages_block(unsigned long blockpfn,
60 unsigned long end_pfn,
61 struct list_head *freelist,
62 bool strict)
Mel Gorman748446b2010-05-24 14:32:27 -070063{
Mel Gormanb7aba692011-01-13 15:45:54 -080064 int nr_scanned = 0, total_isolated = 0;
Mel Gorman748446b2010-05-24 14:32:27 -070065 struct page *cursor;
66
Mel Gorman748446b2010-05-24 14:32:27 -070067 cursor = pfn_to_page(blockpfn);
68
69 /* Isolate free pages. This assumes the block is valid */
70 for (; blockpfn < end_pfn; blockpfn++, cursor++) {
71 int isolated, i;
72 struct page *page = cursor;
73
Michal Nazarewicz85aa1252012-01-30 13:24:03 +010074 if (!pfn_valid_within(blockpfn)) {
75 if (strict)
76 return 0;
Mel Gorman748446b2010-05-24 14:32:27 -070077 continue;
Michal Nazarewicz85aa1252012-01-30 13:24:03 +010078 }
Mel Gormanb7aba692011-01-13 15:45:54 -080079 nr_scanned++;
Mel Gorman748446b2010-05-24 14:32:27 -070080
Michal Nazarewicz85aa1252012-01-30 13:24:03 +010081 if (!PageBuddy(page)) {
82 if (strict)
83 return 0;
Mel Gorman748446b2010-05-24 14:32:27 -070084 continue;
Michal Nazarewicz85aa1252012-01-30 13:24:03 +010085 }
Mel Gorman748446b2010-05-24 14:32:27 -070086
87 /* Found a free page, break it into order-0 pages */
88 isolated = split_free_page(page);
Michal Nazarewicz85aa1252012-01-30 13:24:03 +010089 if (!isolated && strict)
90 return 0;
Mel Gorman748446b2010-05-24 14:32:27 -070091 total_isolated += isolated;
92 for (i = 0; i < isolated; i++) {
93 list_add(&page->lru, freelist);
94 page++;
95 }
96
97 /* If a page was split, advance to the end of it */
98 if (isolated) {
99 blockpfn += isolated - 1;
100 cursor += isolated - 1;
101 }
102 }
103
Mel Gormanb7aba692011-01-13 15:45:54 -0800104 trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated);
Mel Gorman748446b2010-05-24 14:32:27 -0700105 return total_isolated;
106}
107
Michal Nazarewicz85aa1252012-01-30 13:24:03 +0100108/**
109 * isolate_freepages_range() - isolate free pages.
110 * @start_pfn: The first PFN to start isolating.
111 * @end_pfn: The one-past-last PFN.
112 *
113 * Non-free pages, invalid PFNs, or zone boundaries within the
114 * [start_pfn, end_pfn) range are considered errors, cause function to
115 * undo its actions and return zero.
116 *
117 * Otherwise, function returns one-past-the-last PFN of isolated page
118 * (which may be greater then end_pfn if end fell in a middle of
119 * a free page).
120 */
Michal Nazarewiczff9543f2011-12-29 13:09:50 +0100121unsigned long
Michal Nazarewicz85aa1252012-01-30 13:24:03 +0100122isolate_freepages_range(unsigned long start_pfn, unsigned long end_pfn)
123{
124 unsigned long isolated, pfn, block_end_pfn, flags;
125 struct zone *zone = NULL;
126 LIST_HEAD(freelist);
127
128 if (pfn_valid(start_pfn))
129 zone = page_zone(pfn_to_page(start_pfn));
130
131 for (pfn = start_pfn; pfn < end_pfn; pfn += isolated) {
132 if (!pfn_valid(pfn) || zone != page_zone(pfn_to_page(pfn)))
133 break;
134
135 /*
136 * On subsequent iterations ALIGN() is actually not needed,
137 * but we keep it that we not to complicate the code.
138 */
139 block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
140 block_end_pfn = min(block_end_pfn, end_pfn);
141
142 spin_lock_irqsave(&zone->lock, flags);
143 isolated = isolate_freepages_block(pfn, block_end_pfn,
144 &freelist, true);
145 spin_unlock_irqrestore(&zone->lock, flags);
146
147 /*
148 * In strict mode, isolate_freepages_block() returns 0 if
149 * there are any holes in the block (ie. invalid PFNs or
150 * non-free pages).
151 */
152 if (!isolated)
153 break;
154
155 /*
156 * If we managed to isolate pages, it is always (1 << n) *
157 * pageblock_nr_pages for some non-negative n. (Max order
158 * page may span two pageblocks).
159 */
160 }
161
162 /* split_free_page does not map the pages */
163 map_pages(&freelist);
164
165 if (pfn < end_pfn) {
166 /* Loop terminated early, cleanup. */
167 release_freepages(&freelist);
168 return 0;
169 }
170
171 /* We don't use freelists for anything. */
172 return pfn;
173}
174
Mel Gorman748446b2010-05-24 14:32:27 -0700175/* Update the number of anon and file isolated pages in the zone */
176static void acct_isolated(struct zone *zone, struct compact_control *cc)
177{
178 struct page *page;
Minchan Kimb9e84ac2011-10-31 17:06:44 -0700179 unsigned int count[2] = { 0, };
Mel Gorman748446b2010-05-24 14:32:27 -0700180
Minchan Kimb9e84ac2011-10-31 17:06:44 -0700181 list_for_each_entry(page, &cc->migratepages, lru)
182 count[!!page_is_file_cache(page)]++;
Mel Gorman748446b2010-05-24 14:32:27 -0700183
Minchan Kimb9e84ac2011-10-31 17:06:44 -0700184 __mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
185 __mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
Mel Gorman748446b2010-05-24 14:32:27 -0700186}
187
188/* Similar to reclaim, but different enough that they don't share logic */
189static bool too_many_isolated(struct zone *zone)
190{
Minchan Kimbc693042010-09-09 16:38:00 -0700191 unsigned long active, inactive, isolated;
Mel Gorman748446b2010-05-24 14:32:27 -0700192
193 inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
194 zone_page_state(zone, NR_INACTIVE_ANON);
Minchan Kimbc693042010-09-09 16:38:00 -0700195 active = zone_page_state(zone, NR_ACTIVE_FILE) +
196 zone_page_state(zone, NR_ACTIVE_ANON);
Mel Gorman748446b2010-05-24 14:32:27 -0700197 isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
198 zone_page_state(zone, NR_ISOLATED_ANON);
199
Minchan Kimbc693042010-09-09 16:38:00 -0700200 return isolated > (inactive + active) / 2;
Mel Gorman748446b2010-05-24 14:32:27 -0700201}
202
Michal Nazarewicz2fe86e02012-01-30 13:16:26 +0100203/**
204 * isolate_migratepages_range() - isolate all migrate-able pages in range.
205 * @zone: Zone pages are in.
206 * @cc: Compaction control structure.
207 * @low_pfn: The first PFN of the range.
208 * @end_pfn: The one-past-the-last PFN of the range.
209 *
210 * Isolate all pages that can be migrated from the range specified by
211 * [low_pfn, end_pfn). Returns zero if there is a fatal signal
212 * pending), otherwise PFN of the first page that was not scanned
213 * (which may be both less, equal to or more then end_pfn).
214 *
215 * Assumes that cc->migratepages is empty and cc->nr_migratepages is
216 * zero.
217 *
218 * Apart from cc->migratepages and cc->nr_migratetypes this function
219 * does not modify any cc's fields, in particular it does not modify
220 * (or read for that matter) cc->migrate_pfn.
Mel Gorman748446b2010-05-24 14:32:27 -0700221 */
Michal Nazarewiczff9543f2011-12-29 13:09:50 +0100222unsigned long
Michal Nazarewicz2fe86e02012-01-30 13:16:26 +0100223isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
224 unsigned long low_pfn, unsigned long end_pfn)
Mel Gorman748446b2010-05-24 14:32:27 -0700225{
Mel Gorman9927af742011-01-13 15:45:59 -0800226 unsigned long last_pageblock_nr = 0, pageblock_nr;
Mel Gormanb7aba692011-01-13 15:45:54 -0800227 unsigned long nr_scanned = 0, nr_isolated = 0;
Mel Gorman748446b2010-05-24 14:32:27 -0700228 struct list_head *migratelist = &cc->migratepages;
Minchan Kim39deaf82011-10-31 17:06:51 -0700229 isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;
Mel Gorman748446b2010-05-24 14:32:27 -0700230
Mel Gorman748446b2010-05-24 14:32:27 -0700231 /*
232 * Ensure that there are not too many pages isolated from the LRU
233 * list by either parallel reclaimers or compaction. If there are,
234 * delay for some time until fewer pages are isolated
235 */
236 while (unlikely(too_many_isolated(zone))) {
Mel Gormanf9e35b32011-06-15 15:08:52 -0700237 /* async migration should just abort */
238 if (!cc->sync)
Michal Nazarewicz2fe86e02012-01-30 13:16:26 +0100239 return 0;
Mel Gormanf9e35b32011-06-15 15:08:52 -0700240
Mel Gorman748446b2010-05-24 14:32:27 -0700241 congestion_wait(BLK_RW_ASYNC, HZ/10);
242
243 if (fatal_signal_pending(current))
Michal Nazarewicz2fe86e02012-01-30 13:16:26 +0100244 return 0;
Mel Gorman748446b2010-05-24 14:32:27 -0700245 }
246
247 /* Time to isolate some pages for migration */
Andrea Arcangelib2eef8c2011-03-22 16:33:10 -0700248 cond_resched();
Mel Gorman748446b2010-05-24 14:32:27 -0700249 spin_lock_irq(&zone->lru_lock);
250 for (; low_pfn < end_pfn; low_pfn++) {
251 struct page *page;
Andrea Arcangelib2eef8c2011-03-22 16:33:10 -0700252 bool locked = true;
253
254 /* give a chance to irqs before checking need_resched() */
255 if (!((low_pfn+1) % SWAP_CLUSTER_MAX)) {
256 spin_unlock_irq(&zone->lru_lock);
257 locked = false;
258 }
259 if (need_resched() || spin_is_contended(&zone->lru_lock)) {
260 if (locked)
261 spin_unlock_irq(&zone->lru_lock);
262 cond_resched();
263 spin_lock_irq(&zone->lru_lock);
264 if (fatal_signal_pending(current))
265 break;
266 } else if (!locked)
267 spin_lock_irq(&zone->lru_lock);
268
Mel Gorman0bf380b2012-02-03 15:37:18 -0800269 /*
270 * migrate_pfn does not necessarily start aligned to a
271 * pageblock. Ensure that pfn_valid is called when moving
272 * into a new MAX_ORDER_NR_PAGES range in case of large
273 * memory holes within the zone
274 */
275 if ((low_pfn & (MAX_ORDER_NR_PAGES - 1)) == 0) {
276 if (!pfn_valid(low_pfn)) {
277 low_pfn += MAX_ORDER_NR_PAGES - 1;
278 continue;
279 }
280 }
281
Mel Gorman748446b2010-05-24 14:32:27 -0700282 if (!pfn_valid_within(low_pfn))
283 continue;
Mel Gormanb7aba692011-01-13 15:45:54 -0800284 nr_scanned++;
Mel Gorman748446b2010-05-24 14:32:27 -0700285
Mel Gormandc908602012-02-08 17:13:38 -0800286 /*
287 * Get the page and ensure the page is within the same zone.
288 * See the comment in isolate_freepages about overlapping
289 * nodes. It is deliberate that the new zone lock is not taken
290 * as memory compaction should not move pages between nodes.
291 */
Mel Gorman748446b2010-05-24 14:32:27 -0700292 page = pfn_to_page(low_pfn);
Mel Gormandc908602012-02-08 17:13:38 -0800293 if (page_zone(page) != zone)
294 continue;
295
296 /* Skip if free */
Mel Gorman748446b2010-05-24 14:32:27 -0700297 if (PageBuddy(page))
298 continue;
299
Mel Gorman9927af742011-01-13 15:45:59 -0800300 /*
301 * For async migration, also only scan in MOVABLE blocks. Async
302 * migration is optimistic to see if the minimum amount of work
303 * satisfies the allocation
304 */
305 pageblock_nr = low_pfn >> pageblock_order;
306 if (!cc->sync && last_pageblock_nr != pageblock_nr &&
Michal Nazarewicz47118af2011-12-29 13:09:50 +0100307 !migrate_async_suitable(get_pageblock_migratetype(page))) {
Mel Gorman9927af742011-01-13 15:45:59 -0800308 low_pfn += pageblock_nr_pages;
309 low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
310 last_pageblock_nr = pageblock_nr;
311 continue;
312 }
313
Andrea Arcangelibc835012011-01-13 15:47:08 -0800314 if (!PageLRU(page))
315 continue;
316
317 /*
318 * PageLRU is set, and lru_lock excludes isolation,
319 * splitting and collapsing (collapsing has already
320 * happened if PageLRU is set).
321 */
322 if (PageTransHuge(page)) {
323 low_pfn += (1 << compound_order(page)) - 1;
324 continue;
325 }
326
Mel Gormanc8244932012-01-12 17:19:38 -0800327 if (!cc->sync)
328 mode |= ISOLATE_ASYNC_MIGRATE;
329
Mel Gorman748446b2010-05-24 14:32:27 -0700330 /* Try isolate the page */
Minchan Kim39deaf82011-10-31 17:06:51 -0700331 if (__isolate_lru_page(page, mode, 0) != 0)
Mel Gorman748446b2010-05-24 14:32:27 -0700332 continue;
333
Andrea Arcangelibc835012011-01-13 15:47:08 -0800334 VM_BUG_ON(PageTransCompound(page));
335
Mel Gorman748446b2010-05-24 14:32:27 -0700336 /* Successfully isolated */
337 del_page_from_lru_list(zone, page, page_lru(page));
338 list_add(&page->lru, migratelist);
Mel Gorman748446b2010-05-24 14:32:27 -0700339 cc->nr_migratepages++;
Mel Gormanb7aba692011-01-13 15:45:54 -0800340 nr_isolated++;
Mel Gorman748446b2010-05-24 14:32:27 -0700341
342 /* Avoid isolating too much */
Hillf Danton31b83842012-01-10 15:07:59 -0800343 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
344 ++low_pfn;
Mel Gorman748446b2010-05-24 14:32:27 -0700345 break;
Hillf Danton31b83842012-01-10 15:07:59 -0800346 }
Mel Gorman748446b2010-05-24 14:32:27 -0700347 }
348
349 acct_isolated(zone, cc);
350
351 spin_unlock_irq(&zone->lru_lock);
Mel Gorman748446b2010-05-24 14:32:27 -0700352
Mel Gormanb7aba692011-01-13 15:45:54 -0800353 trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
354
Michal Nazarewicz2fe86e02012-01-30 13:16:26 +0100355 return low_pfn;
356}
357
Michal Nazarewiczff9543f2011-12-29 13:09:50 +0100358#endif /* CONFIG_COMPACTION || CONFIG_CMA */
359#ifdef CONFIG_COMPACTION
360
361/* Returns true if the page is within a block suitable for migration to */
362static bool suitable_migration_target(struct page *page)
Michal Nazarewicz2fe86e02012-01-30 13:16:26 +0100363{
Michal Nazarewicz2fe86e02012-01-30 13:16:26 +0100364
Michal Nazarewiczff9543f2011-12-29 13:09:50 +0100365 int migratetype = get_pageblock_migratetype(page);
Michal Nazarewicz2fe86e02012-01-30 13:16:26 +0100366
Michal Nazarewiczff9543f2011-12-29 13:09:50 +0100367 /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
368 if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE)
369 return false;
Michal Nazarewicz2fe86e02012-01-30 13:16:26 +0100370
Michal Nazarewiczff9543f2011-12-29 13:09:50 +0100371 /* If the page is a large free page, then allow migration */
372 if (PageBuddy(page) && page_order(page) >= pageblock_order)
373 return true;
374
Michal Nazarewicz47118af2011-12-29 13:09:50 +0100375 /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
376 if (migrate_async_suitable(migratetype))
Michal Nazarewiczff9543f2011-12-29 13:09:50 +0100377 return true;
378
379 /* Otherwise skip the block */
380 return false;
381}
382
383/*
384 * Based on information in the current compact_control, find blocks
385 * suitable for isolating free pages from and then isolate them.
386 */
387static void isolate_freepages(struct zone *zone,
388 struct compact_control *cc)
389{
390 struct page *page;
391 unsigned long high_pfn, low_pfn, pfn, zone_end_pfn, end_pfn;
392 unsigned long flags;
393 int nr_freepages = cc->nr_freepages;
394 struct list_head *freelist = &cc->freepages;
395
396 /*
397 * Initialise the free scanner. The starting point is where we last
398 * scanned from (or the end of the zone if starting). The low point
399 * is the end of the pageblock the migration scanner is using.
400 */
401 pfn = cc->free_pfn;
402 low_pfn = cc->migrate_pfn + pageblock_nr_pages;
403
404 /*
405 * Take care that if the migration scanner is at the end of the zone
406 * that the free scanner does not accidentally move to the next zone
407 * in the next isolation cycle.
408 */
409 high_pfn = min(low_pfn, pfn);
410
411 zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
412
413 /*
414 * Isolate free pages until enough are available to migrate the
415 * pages on cc->migratepages. We stop searching if the migrate
416 * and free page scanners meet or enough free pages are isolated.
417 */
418 for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages;
419 pfn -= pageblock_nr_pages) {
420 unsigned long isolated;
421
422 if (!pfn_valid(pfn))
423 continue;
424
425 /*
426 * Check for overlapping nodes/zones. It's possible on some
427 * configurations to have a setup like
428 * node0 node1 node0
429 * i.e. it's possible that all pages within a zones range of
430 * pages do not belong to a single zone.
431 */
432 page = pfn_to_page(pfn);
433 if (page_zone(page) != zone)
434 continue;
435
436 /* Check the block is suitable for migration */
437 if (!suitable_migration_target(page))
438 continue;
439
440 /*
441 * Found a block suitable for isolating free pages from. Now
442 * we disabled interrupts, double check things are ok and
443 * isolate the pages. This is to minimise the time IRQs
444 * are disabled
445 */
446 isolated = 0;
447 spin_lock_irqsave(&zone->lock, flags);
448 if (suitable_migration_target(page)) {
449 end_pfn = min(pfn + pageblock_nr_pages, zone_end_pfn);
450 isolated = isolate_freepages_block(pfn, end_pfn,
451 freelist, false);
452 nr_freepages += isolated;
453 }
454 spin_unlock_irqrestore(&zone->lock, flags);
455
456 /*
457 * Record the highest PFN we isolated pages from. When next
458 * looking for free pages, the search will restart here as
459 * page migration may have returned some pages to the allocator
460 */
461 if (isolated)
462 high_pfn = max(high_pfn, pfn);
Michal Nazarewicz2fe86e02012-01-30 13:16:26 +0100463 }
464
Michal Nazarewiczff9543f2011-12-29 13:09:50 +0100465 /* split_free_page does not map the pages */
466 map_pages(freelist);
Michal Nazarewicz2fe86e02012-01-30 13:16:26 +0100467
Michal Nazarewiczff9543f2011-12-29 13:09:50 +0100468 cc->free_pfn = high_pfn;
469 cc->nr_freepages = nr_freepages;
Mel Gorman748446b2010-05-24 14:32:27 -0700470}
471
472/*
473 * This is a migrate-callback that "allocates" freepages by taking pages
474 * from the isolated freelists in the block we are migrating to.
475 */
476static struct page *compaction_alloc(struct page *migratepage,
477 unsigned long data,
478 int **result)
479{
480 struct compact_control *cc = (struct compact_control *)data;
481 struct page *freepage;
482
483 /* Isolate free pages if necessary */
484 if (list_empty(&cc->freepages)) {
485 isolate_freepages(cc->zone, cc);
486
487 if (list_empty(&cc->freepages))
488 return NULL;
489 }
490
491 freepage = list_entry(cc->freepages.next, struct page, lru);
492 list_del(&freepage->lru);
493 cc->nr_freepages--;
494
495 return freepage;
496}
497
498/*
499 * We cannot control nr_migratepages and nr_freepages fully when migration is
500 * running as migrate_pages() has no knowledge of compact_control. When
501 * migration is complete, we count the number of pages on the lists by hand.
502 */
503static void update_nr_listpages(struct compact_control *cc)
504{
505 int nr_migratepages = 0;
506 int nr_freepages = 0;
507 struct page *page;
508
509 list_for_each_entry(page, &cc->migratepages, lru)
510 nr_migratepages++;
511 list_for_each_entry(page, &cc->freepages, lru)
512 nr_freepages++;
513
514 cc->nr_migratepages = nr_migratepages;
515 cc->nr_freepages = nr_freepages;
516}
517
Michal Nazarewiczff9543f2011-12-29 13:09:50 +0100518/* possible outcome of isolate_migratepages */
519typedef enum {
520 ISOLATE_ABORT, /* Abort compaction now */
521 ISOLATE_NONE, /* No pages isolated, continue scanning */
522 ISOLATE_SUCCESS, /* Pages isolated, migrate */
523} isolate_migrate_t;
524
525/*
526 * Isolate all pages that can be migrated from the block pointed to by
527 * the migrate scanner within compact_control.
528 */
529static isolate_migrate_t isolate_migratepages(struct zone *zone,
530 struct compact_control *cc)
531{
532 unsigned long low_pfn, end_pfn;
533
534 /* Do not scan outside zone boundaries */
535 low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
536
537 /* Only scan within a pageblock boundary */
538 end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
539
540 /* Do not cross the free scanner or scan within a memory hole */
541 if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
542 cc->migrate_pfn = end_pfn;
543 return ISOLATE_NONE;
544 }
545
546 /* Perform the isolation */
547 low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn);
548 if (!low_pfn)
549 return ISOLATE_ABORT;
550
551 cc->migrate_pfn = low_pfn;
552
553 return ISOLATE_SUCCESS;
554}
555
Mel Gorman748446b2010-05-24 14:32:27 -0700556static int compact_finished(struct zone *zone,
Andrea Arcangeli5a03b052011-01-13 15:47:11 -0800557 struct compact_control *cc)
Mel Gorman748446b2010-05-24 14:32:27 -0700558{
Mel Gorman56de7262010-05-24 14:32:30 -0700559 unsigned int order;
Andrea Arcangeli5a03b052011-01-13 15:47:11 -0800560 unsigned long watermark;
Mel Gorman56de7262010-05-24 14:32:30 -0700561
Mel Gorman748446b2010-05-24 14:32:27 -0700562 if (fatal_signal_pending(current))
563 return COMPACT_PARTIAL;
564
565 /* Compaction run completes if the migrate and free scanner meet */
566 if (cc->free_pfn <= cc->migrate_pfn)
567 return COMPACT_COMPLETE;
568
Johannes Weiner82478fb2011-01-20 14:44:21 -0800569 /*
570 * order == -1 is expected when compacting via
571 * /proc/sys/vm/compact_memory
572 */
Mel Gorman56de7262010-05-24 14:32:30 -0700573 if (cc->order == -1)
574 return COMPACT_CONTINUE;
575
Michal Hocko3957c772011-06-15 15:08:25 -0700576 /* Compaction run is not finished if the watermark is not met */
577 watermark = low_wmark_pages(zone);
578 watermark += (1 << cc->order);
579
580 if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
581 return COMPACT_CONTINUE;
582
Mel Gorman56de7262010-05-24 14:32:30 -0700583 /* Direct compactor: Is a suitable page free? */
584 for (order = cc->order; order < MAX_ORDER; order++) {
585 /* Job done if page is free of the right migratetype */
586 if (!list_empty(&zone->free_area[order].free_list[cc->migratetype]))
587 return COMPACT_PARTIAL;
588
589 /* Job done if allocation would set block type */
590 if (order >= pageblock_order && zone->free_area[order].nr_free)
591 return COMPACT_PARTIAL;
592 }
593
Mel Gorman748446b2010-05-24 14:32:27 -0700594 return COMPACT_CONTINUE;
595}
596
Mel Gorman3e7d3442011-01-13 15:45:56 -0800597/*
598 * compaction_suitable: Is this suitable to run compaction on this zone now?
599 * Returns
600 * COMPACT_SKIPPED - If there are too few free pages for compaction
601 * COMPACT_PARTIAL - If the allocation would succeed without compaction
602 * COMPACT_CONTINUE - If compaction should run now
603 */
604unsigned long compaction_suitable(struct zone *zone, int order)
605{
606 int fragindex;
607 unsigned long watermark;
608
609 /*
Michal Hocko3957c772011-06-15 15:08:25 -0700610 * order == -1 is expected when compacting via
611 * /proc/sys/vm/compact_memory
612 */
613 if (order == -1)
614 return COMPACT_CONTINUE;
615
616 /*
Mel Gorman3e7d3442011-01-13 15:45:56 -0800617 * Watermarks for order-0 must be met for compaction. Note the 2UL.
618 * This is because during migration, copies of pages need to be
619 * allocated and for a short time, the footprint is higher
620 */
621 watermark = low_wmark_pages(zone) + (2UL << order);
622 if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
623 return COMPACT_SKIPPED;
624
625 /*
626 * fragmentation index determines if allocation failures are due to
627 * low memory or external fragmentation
628 *
Shaohua Lia582a732011-06-15 15:08:49 -0700629 * index of -1000 implies allocations might succeed depending on
630 * watermarks
Mel Gorman3e7d3442011-01-13 15:45:56 -0800631 * index towards 0 implies failure is due to lack of memory
632 * index towards 1000 implies failure is due to fragmentation
633 *
634 * Only compact if a failure would be due to fragmentation.
635 */
636 fragindex = fragmentation_index(zone, order);
637 if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
638 return COMPACT_SKIPPED;
639
Shaohua Lia582a732011-06-15 15:08:49 -0700640 if (fragindex == -1000 && zone_watermark_ok(zone, order, watermark,
641 0, 0))
Mel Gorman3e7d3442011-01-13 15:45:56 -0800642 return COMPACT_PARTIAL;
643
644 return COMPACT_CONTINUE;
645}
646
Mel Gorman748446b2010-05-24 14:32:27 -0700647static int compact_zone(struct zone *zone, struct compact_control *cc)
648{
649 int ret;
650
Mel Gorman3e7d3442011-01-13 15:45:56 -0800651 ret = compaction_suitable(zone, cc->order);
652 switch (ret) {
653 case COMPACT_PARTIAL:
654 case COMPACT_SKIPPED:
655 /* Compaction is likely to fail */
656 return ret;
657 case COMPACT_CONTINUE:
658 /* Fall through to compaction */
659 ;
660 }
661
Mel Gorman748446b2010-05-24 14:32:27 -0700662 /* Setup to move all movable pages to the end of the zone */
663 cc->migrate_pfn = zone->zone_start_pfn;
664 cc->free_pfn = cc->migrate_pfn + zone->spanned_pages;
665 cc->free_pfn &= ~(pageblock_nr_pages-1);
666
667 migrate_prep_local();
668
669 while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
670 unsigned long nr_migrate, nr_remaining;
Minchan Kim9d502c12011-03-22 16:30:39 -0700671 int err;
Mel Gorman748446b2010-05-24 14:32:27 -0700672
Mel Gormanf9e35b32011-06-15 15:08:52 -0700673 switch (isolate_migratepages(zone, cc)) {
674 case ISOLATE_ABORT:
675 ret = COMPACT_PARTIAL;
676 goto out;
677 case ISOLATE_NONE:
Mel Gorman748446b2010-05-24 14:32:27 -0700678 continue;
Mel Gormanf9e35b32011-06-15 15:08:52 -0700679 case ISOLATE_SUCCESS:
680 ;
681 }
Mel Gorman748446b2010-05-24 14:32:27 -0700682
683 nr_migrate = cc->nr_migratepages;
Minchan Kim9d502c12011-03-22 16:30:39 -0700684 err = migrate_pages(&cc->migratepages, compaction_alloc,
Mel Gorman7f0f2492011-01-13 15:45:58 -0800685 (unsigned long)cc, false,
Mel Gormana6bc32b2012-01-12 17:19:43 -0800686 cc->sync ? MIGRATE_SYNC_LIGHT : MIGRATE_ASYNC);
Mel Gorman748446b2010-05-24 14:32:27 -0700687 update_nr_listpages(cc);
688 nr_remaining = cc->nr_migratepages;
689
690 count_vm_event(COMPACTBLOCKS);
691 count_vm_events(COMPACTPAGES, nr_migrate - nr_remaining);
692 if (nr_remaining)
693 count_vm_events(COMPACTPAGEFAILED, nr_remaining);
Mel Gormanb7aba692011-01-13 15:45:54 -0800694 trace_mm_compaction_migratepages(nr_migrate - nr_remaining,
695 nr_remaining);
Mel Gorman748446b2010-05-24 14:32:27 -0700696
697 /* Release LRU pages not migrated */
Minchan Kim9d502c12011-03-22 16:30:39 -0700698 if (err) {
Mel Gorman748446b2010-05-24 14:32:27 -0700699 putback_lru_pages(&cc->migratepages);
700 cc->nr_migratepages = 0;
701 }
702
703 }
704
Mel Gormanf9e35b32011-06-15 15:08:52 -0700705out:
Mel Gorman748446b2010-05-24 14:32:27 -0700706 /* Release free pages and check accounting */
707 cc->nr_freepages -= release_freepages(&cc->freepages);
708 VM_BUG_ON(cc->nr_freepages != 0);
709
710 return ret;
711}
Mel Gorman76ab0f52010-05-24 14:32:28 -0700712
Kyungmin Parkd43a87e2011-10-31 17:09:08 -0700713static unsigned long compact_zone_order(struct zone *zone,
Andrea Arcangeli5a03b052011-01-13 15:47:11 -0800714 int order, gfp_t gfp_mask,
Andrea Arcangelid527caf2011-03-22 16:30:38 -0700715 bool sync)
Mel Gorman56de7262010-05-24 14:32:30 -0700716{
717 struct compact_control cc = {
718 .nr_freepages = 0,
719 .nr_migratepages = 0,
720 .order = order,
721 .migratetype = allocflags_to_migratetype(gfp_mask),
722 .zone = zone,
Mel Gorman77f1fe62011-01-13 15:45:57 -0800723 .sync = sync,
Mel Gorman56de7262010-05-24 14:32:30 -0700724 };
725 INIT_LIST_HEAD(&cc.freepages);
726 INIT_LIST_HEAD(&cc.migratepages);
727
728 return compact_zone(zone, &cc);
729}
730
Mel Gorman5e771902010-05-24 14:32:31 -0700731int sysctl_extfrag_threshold = 500;
732
Mel Gorman56de7262010-05-24 14:32:30 -0700733/**
734 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
735 * @zonelist: The zonelist used for the current allocation
736 * @order: The order of the current allocation
737 * @gfp_mask: The GFP mask of the current allocation
738 * @nodemask: The allowed nodes to allocate from
Mel Gorman77f1fe62011-01-13 15:45:57 -0800739 * @sync: Whether migration is synchronous or not
Mel Gorman56de7262010-05-24 14:32:30 -0700740 *
741 * This is the main entry point for direct page compaction.
742 */
743unsigned long try_to_compact_pages(struct zonelist *zonelist,
Mel Gorman77f1fe62011-01-13 15:45:57 -0800744 int order, gfp_t gfp_mask, nodemask_t *nodemask,
745 bool sync)
Mel Gorman56de7262010-05-24 14:32:30 -0700746{
747 enum zone_type high_zoneidx = gfp_zone(gfp_mask);
748 int may_enter_fs = gfp_mask & __GFP_FS;
749 int may_perform_io = gfp_mask & __GFP_IO;
Mel Gorman56de7262010-05-24 14:32:30 -0700750 struct zoneref *z;
751 struct zone *zone;
752 int rc = COMPACT_SKIPPED;
753
754 /*
755 * Check whether it is worth even starting compaction. The order check is
756 * made because an assumption is made that the page allocator can satisfy
757 * the "cheaper" orders without taking special steps
758 */
Andrea Arcangelic5a73c32011-01-13 15:47:11 -0800759 if (!order || !may_enter_fs || !may_perform_io)
Mel Gorman56de7262010-05-24 14:32:30 -0700760 return rc;
761
762 count_vm_event(COMPACTSTALL);
763
764 /* Compact each zone in the list */
765 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
766 nodemask) {
Mel Gorman56de7262010-05-24 14:32:30 -0700767 int status;
768
Andrea Arcangelid527caf2011-03-22 16:30:38 -0700769 status = compact_zone_order(zone, order, gfp_mask, sync);
Mel Gorman56de7262010-05-24 14:32:30 -0700770 rc = max(status, rc);
771
Mel Gorman3e7d3442011-01-13 15:45:56 -0800772 /* If a normal allocation would succeed, stop compacting */
773 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
Mel Gorman56de7262010-05-24 14:32:30 -0700774 break;
775 }
776
777 return rc;
778}
779
780
Mel Gorman76ab0f52010-05-24 14:32:28 -0700781/* Compact all zones within a node */
Rik van Riel7be62de2012-03-21 16:33:52 -0700782static int __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
Mel Gorman76ab0f52010-05-24 14:32:28 -0700783{
784 int zoneid;
Mel Gorman76ab0f52010-05-24 14:32:28 -0700785 struct zone *zone;
786
Mel Gorman76ab0f52010-05-24 14:32:28 -0700787 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
Mel Gorman76ab0f52010-05-24 14:32:28 -0700788
789 zone = &pgdat->node_zones[zoneid];
790 if (!populated_zone(zone))
791 continue;
792
Rik van Riel7be62de2012-03-21 16:33:52 -0700793 cc->nr_freepages = 0;
794 cc->nr_migratepages = 0;
795 cc->zone = zone;
796 INIT_LIST_HEAD(&cc->freepages);
797 INIT_LIST_HEAD(&cc->migratepages);
Mel Gorman76ab0f52010-05-24 14:32:28 -0700798
Dan Carpenteraad6ec32012-03-21 16:33:54 -0700799 if (cc->order == -1 || !compaction_deferred(zone, cc->order))
Rik van Riel7be62de2012-03-21 16:33:52 -0700800 compact_zone(zone, cc);
Mel Gorman76ab0f52010-05-24 14:32:28 -0700801
Rik van Rielaff62242012-03-21 16:33:52 -0700802 if (cc->order > 0) {
803 int ok = zone_watermark_ok(zone, cc->order,
804 low_wmark_pages(zone), 0, 0);
805 if (ok && cc->order > zone->compact_order_failed)
806 zone->compact_order_failed = cc->order + 1;
807 /* Currently async compaction is never deferred. */
808 else if (!ok && cc->sync)
809 defer_compaction(zone, cc->order);
810 }
811
Rik van Riel7be62de2012-03-21 16:33:52 -0700812 VM_BUG_ON(!list_empty(&cc->freepages));
813 VM_BUG_ON(!list_empty(&cc->migratepages));
Mel Gorman76ab0f52010-05-24 14:32:28 -0700814 }
815
816 return 0;
817}
818
Rik van Riel7be62de2012-03-21 16:33:52 -0700819int compact_pgdat(pg_data_t *pgdat, int order)
820{
821 struct compact_control cc = {
822 .order = order,
823 .sync = false,
824 };
825
826 return __compact_pgdat(pgdat, &cc);
827}
828
829static int compact_node(int nid)
830{
Rik van Riel7be62de2012-03-21 16:33:52 -0700831 struct compact_control cc = {
832 .order = -1,
833 .sync = true,
834 };
835
Hugh Dickins8575ec22012-03-21 16:33:53 -0700836 return __compact_pgdat(NODE_DATA(nid), &cc);
Rik van Riel7be62de2012-03-21 16:33:52 -0700837}
838
Mel Gorman76ab0f52010-05-24 14:32:28 -0700839/* Compact all nodes in the system */
840static int compact_nodes(void)
841{
842 int nid;
843
Hugh Dickins8575ec22012-03-21 16:33:53 -0700844 /* Flush pending updates to the LRU lists */
845 lru_add_drain_all();
846
Mel Gorman76ab0f52010-05-24 14:32:28 -0700847 for_each_online_node(nid)
848 compact_node(nid);
849
850 return COMPACT_COMPLETE;
851}
852
853/* The written value is actually unused, all memory is compacted */
854int sysctl_compact_memory;
855
856/* This is the entry point for compacting all nodes via /proc/sys/vm */
857int sysctl_compaction_handler(struct ctl_table *table, int write,
858 void __user *buffer, size_t *length, loff_t *ppos)
859{
860 if (write)
861 return compact_nodes();
862
863 return 0;
864}
Mel Gormaned4a6d72010-05-24 14:32:29 -0700865
Mel Gorman5e771902010-05-24 14:32:31 -0700866int sysctl_extfrag_handler(struct ctl_table *table, int write,
867 void __user *buffer, size_t *length, loff_t *ppos)
868{
869 proc_dointvec_minmax(table, write, buffer, length, ppos);
870
871 return 0;
872}
873
Mel Gormaned4a6d72010-05-24 14:32:29 -0700874#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
Kay Sievers10fbcf42011-12-21 14:48:43 -0800875ssize_t sysfs_compact_node(struct device *dev,
876 struct device_attribute *attr,
Mel Gormaned4a6d72010-05-24 14:32:29 -0700877 const char *buf, size_t count)
878{
Hugh Dickins8575ec22012-03-21 16:33:53 -0700879 int nid = dev->id;
880
881 if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
882 /* Flush pending updates to the LRU lists */
883 lru_add_drain_all();
884
885 compact_node(nid);
886 }
Mel Gormaned4a6d72010-05-24 14:32:29 -0700887
888 return count;
889}
Kay Sievers10fbcf42011-12-21 14:48:43 -0800890static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
Mel Gormaned4a6d72010-05-24 14:32:29 -0700891
892int compaction_register_node(struct node *node)
893{
Kay Sievers10fbcf42011-12-21 14:48:43 -0800894 return device_create_file(&node->dev, &dev_attr_compact);
Mel Gormaned4a6d72010-05-24 14:32:29 -0700895}
896
897void compaction_unregister_node(struct node *node)
898{
Kay Sievers10fbcf42011-12-21 14:48:43 -0800899 return device_remove_file(&node->dev, &dev_attr_compact);
Mel Gormaned4a6d72010-05-24 14:32:29 -0700900}
901#endif /* CONFIG_SYSFS && CONFIG_NUMA */
Michal Nazarewiczff9543f2011-12-29 13:09:50 +0100902
903#endif /* CONFIG_COMPACTION */