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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
Mel Gormanb7aba692011-01-13 15:45:54 -080019#define CREATE_TRACE_POINTS
20#include <trace/events/compaction.h>
21
Mel Gorman748446b2010-05-24 14:32:27 -070022/*
23 * compact_control is used to track pages being migrated and the free pages
24 * they are being migrated to during memory compaction. The free_pfn starts
25 * at the end of a zone and migrate_pfn begins at the start. Movable pages
26 * are moved to the end of a zone during a compaction run and the run
27 * completes when free_pfn <= migrate_pfn
28 */
29struct compact_control {
30 struct list_head freepages; /* List of free pages to migrate to */
31 struct list_head migratepages; /* List of pages being migrated */
32 unsigned long nr_freepages; /* Number of isolated free pages */
33 unsigned long nr_migratepages; /* Number of pages to migrate */
34 unsigned long free_pfn; /* isolate_freepages search base */
35 unsigned long migrate_pfn; /* isolate_migratepages search base */
Mel Gorman77f1fe62011-01-13 15:45:57 -080036 bool sync; /* Synchronous migration */
Mel Gorman748446b2010-05-24 14:32:27 -070037
Mel Gorman56de7262010-05-24 14:32:30 -070038 unsigned int order; /* order a direct compactor needs */
39 int migratetype; /* MOVABLE, RECLAIMABLE etc */
Mel Gorman748446b2010-05-24 14:32:27 -070040 struct zone *zone;
41};
42
43static unsigned long release_freepages(struct list_head *freelist)
44{
45 struct page *page, *next;
46 unsigned long count = 0;
47
48 list_for_each_entry_safe(page, next, freelist, lru) {
49 list_del(&page->lru);
50 __free_page(page);
51 count++;
52 }
53
54 return count;
55}
56
57/* Isolate free pages onto a private freelist. Must hold zone->lock */
58static unsigned long isolate_freepages_block(struct zone *zone,
59 unsigned long blockpfn,
60 struct list_head *freelist)
61{
62 unsigned long zone_end_pfn, end_pfn;
Mel Gormanb7aba692011-01-13 15:45:54 -080063 int nr_scanned = 0, total_isolated = 0;
Mel Gorman748446b2010-05-24 14:32:27 -070064 struct page *cursor;
65
66 /* Get the last PFN we should scan for free pages at */
67 zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
68 end_pfn = min(blockpfn + pageblock_nr_pages, zone_end_pfn);
69
70 /* Find the first usable PFN in the block to initialse page cursor */
71 for (; blockpfn < end_pfn; blockpfn++) {
72 if (pfn_valid_within(blockpfn))
73 break;
74 }
75 cursor = pfn_to_page(blockpfn);
76
77 /* Isolate free pages. This assumes the block is valid */
78 for (; blockpfn < end_pfn; blockpfn++, cursor++) {
79 int isolated, i;
80 struct page *page = cursor;
81
82 if (!pfn_valid_within(blockpfn))
83 continue;
Mel Gormanb7aba692011-01-13 15:45:54 -080084 nr_scanned++;
Mel Gorman748446b2010-05-24 14:32:27 -070085
86 if (!PageBuddy(page))
87 continue;
88
89 /* Found a free page, break it into order-0 pages */
90 isolated = split_free_page(page);
91 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
108/* Returns true if the page is within a block suitable for migration to */
109static bool suitable_migration_target(struct page *page)
110{
111
112 int migratetype = get_pageblock_migratetype(page);
113
114 /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
115 if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE)
116 return false;
117
118 /* If the page is a large free page, then allow migration */
119 if (PageBuddy(page) && page_order(page) >= pageblock_order)
120 return true;
121
122 /* If the block is MIGRATE_MOVABLE, allow migration */
123 if (migratetype == MIGRATE_MOVABLE)
124 return true;
125
126 /* Otherwise skip the block */
127 return false;
128}
129
130/*
131 * Based on information in the current compact_control, find blocks
132 * suitable for isolating free pages from and then isolate them.
133 */
134static void isolate_freepages(struct zone *zone,
135 struct compact_control *cc)
136{
137 struct page *page;
138 unsigned long high_pfn, low_pfn, pfn;
139 unsigned long flags;
140 int nr_freepages = cc->nr_freepages;
141 struct list_head *freelist = &cc->freepages;
142
Mel Gorman7454f4b2011-06-15 15:08:50 -0700143 /*
144 * Initialise the free scanner. The starting point is where we last
145 * scanned from (or the end of the zone if starting). The low point
146 * is the end of the pageblock the migration scanner is using.
147 */
Mel Gorman748446b2010-05-24 14:32:27 -0700148 pfn = cc->free_pfn;
149 low_pfn = cc->migrate_pfn + pageblock_nr_pages;
Mel Gorman7454f4b2011-06-15 15:08:50 -0700150
151 /*
152 * Take care that if the migration scanner is at the end of the zone
153 * that the free scanner does not accidentally move to the next zone
154 * in the next isolation cycle.
155 */
156 high_pfn = min(low_pfn, pfn);
Mel Gorman748446b2010-05-24 14:32:27 -0700157
158 /*
159 * Isolate free pages until enough are available to migrate the
160 * pages on cc->migratepages. We stop searching if the migrate
161 * and free page scanners meet or enough free pages are isolated.
162 */
Mel Gorman748446b2010-05-24 14:32:27 -0700163 for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages;
164 pfn -= pageblock_nr_pages) {
165 unsigned long isolated;
166
167 if (!pfn_valid(pfn))
168 continue;
169
170 /*
171 * Check for overlapping nodes/zones. It's possible on some
172 * configurations to have a setup like
173 * node0 node1 node0
174 * i.e. it's possible that all pages within a zones range of
175 * pages do not belong to a single zone.
176 */
177 page = pfn_to_page(pfn);
178 if (page_zone(page) != zone)
179 continue;
180
181 /* Check the block is suitable for migration */
182 if (!suitable_migration_target(page))
183 continue;
184
Mel Gorman602605a2011-03-22 16:33:08 -0700185 /*
186 * Found a block suitable for isolating free pages from. Now
187 * we disabled interrupts, double check things are ok and
188 * isolate the pages. This is to minimise the time IRQs
189 * are disabled
190 */
191 isolated = 0;
192 spin_lock_irqsave(&zone->lock, flags);
193 if (suitable_migration_target(page)) {
194 isolated = isolate_freepages_block(zone, pfn, freelist);
195 nr_freepages += isolated;
196 }
197 spin_unlock_irqrestore(&zone->lock, flags);
Mel Gorman748446b2010-05-24 14:32:27 -0700198
199 /*
200 * Record the highest PFN we isolated pages from. When next
201 * looking for free pages, the search will restart here as
202 * page migration may have returned some pages to the allocator
203 */
204 if (isolated)
205 high_pfn = max(high_pfn, pfn);
206 }
Mel Gorman748446b2010-05-24 14:32:27 -0700207
208 /* split_free_page does not map the pages */
209 list_for_each_entry(page, freelist, lru) {
210 arch_alloc_page(page, 0);
211 kernel_map_pages(page, 1, 1);
212 }
213
214 cc->free_pfn = high_pfn;
215 cc->nr_freepages = nr_freepages;
216}
217
218/* Update the number of anon and file isolated pages in the zone */
219static void acct_isolated(struct zone *zone, struct compact_control *cc)
220{
221 struct page *page;
Minchan Kimb9e84ac2011-10-31 17:06:44 -0700222 unsigned int count[2] = { 0, };
Mel Gorman748446b2010-05-24 14:32:27 -0700223
Minchan Kimb9e84ac2011-10-31 17:06:44 -0700224 list_for_each_entry(page, &cc->migratepages, lru)
225 count[!!page_is_file_cache(page)]++;
Mel Gorman748446b2010-05-24 14:32:27 -0700226
Minchan Kimb9e84ac2011-10-31 17:06:44 -0700227 __mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
228 __mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
Mel Gorman748446b2010-05-24 14:32:27 -0700229}
230
231/* Similar to reclaim, but different enough that they don't share logic */
232static bool too_many_isolated(struct zone *zone)
233{
Minchan Kimbc693042010-09-09 16:38:00 -0700234 unsigned long active, inactive, isolated;
Mel Gorman748446b2010-05-24 14:32:27 -0700235
236 inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
237 zone_page_state(zone, NR_INACTIVE_ANON);
Minchan Kimbc693042010-09-09 16:38:00 -0700238 active = zone_page_state(zone, NR_ACTIVE_FILE) +
239 zone_page_state(zone, NR_ACTIVE_ANON);
Mel Gorman748446b2010-05-24 14:32:27 -0700240 isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
241 zone_page_state(zone, NR_ISOLATED_ANON);
242
Minchan Kimbc693042010-09-09 16:38:00 -0700243 return isolated > (inactive + active) / 2;
Mel Gorman748446b2010-05-24 14:32:27 -0700244}
245
Mel Gormanf9e35b32011-06-15 15:08:52 -0700246/* possible outcome of isolate_migratepages */
247typedef enum {
248 ISOLATE_ABORT, /* Abort compaction now */
249 ISOLATE_NONE, /* No pages isolated, continue scanning */
250 ISOLATE_SUCCESS, /* Pages isolated, migrate */
251} isolate_migrate_t;
252
Mel Gorman748446b2010-05-24 14:32:27 -0700253/*
254 * Isolate all pages that can be migrated from the block pointed to by
255 * the migrate scanner within compact_control.
256 */
Mel Gormanf9e35b32011-06-15 15:08:52 -0700257static isolate_migrate_t isolate_migratepages(struct zone *zone,
Mel Gorman748446b2010-05-24 14:32:27 -0700258 struct compact_control *cc)
259{
260 unsigned long low_pfn, end_pfn;
Mel Gorman9927af742011-01-13 15:45:59 -0800261 unsigned long last_pageblock_nr = 0, pageblock_nr;
Mel Gormanb7aba692011-01-13 15:45:54 -0800262 unsigned long nr_scanned = 0, nr_isolated = 0;
Mel Gorman748446b2010-05-24 14:32:27 -0700263 struct list_head *migratelist = &cc->migratepages;
Minchan Kim39deaf82011-10-31 17:06:51 -0700264 isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;
Mel Gorman748446b2010-05-24 14:32:27 -0700265
266 /* Do not scan outside zone boundaries */
267 low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
268
269 /* Only scan within a pageblock boundary */
270 end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
271
272 /* Do not cross the free scanner or scan within a memory hole */
273 if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
274 cc->migrate_pfn = end_pfn;
Mel Gormanf9e35b32011-06-15 15:08:52 -0700275 return ISOLATE_NONE;
Mel Gorman748446b2010-05-24 14:32:27 -0700276 }
277
278 /*
279 * Ensure that there are not too many pages isolated from the LRU
280 * list by either parallel reclaimers or compaction. If there are,
281 * delay for some time until fewer pages are isolated
282 */
283 while (unlikely(too_many_isolated(zone))) {
Mel Gormanf9e35b32011-06-15 15:08:52 -0700284 /* async migration should just abort */
285 if (!cc->sync)
286 return ISOLATE_ABORT;
287
Mel Gorman748446b2010-05-24 14:32:27 -0700288 congestion_wait(BLK_RW_ASYNC, HZ/10);
289
290 if (fatal_signal_pending(current))
Mel Gormanf9e35b32011-06-15 15:08:52 -0700291 return ISOLATE_ABORT;
Mel Gorman748446b2010-05-24 14:32:27 -0700292 }
293
294 /* Time to isolate some pages for migration */
Andrea Arcangelib2eef8c2011-03-22 16:33:10 -0700295 cond_resched();
Mel Gorman748446b2010-05-24 14:32:27 -0700296 spin_lock_irq(&zone->lru_lock);
297 for (; low_pfn < end_pfn; low_pfn++) {
298 struct page *page;
Andrea Arcangelib2eef8c2011-03-22 16:33:10 -0700299 bool locked = true;
300
301 /* give a chance to irqs before checking need_resched() */
302 if (!((low_pfn+1) % SWAP_CLUSTER_MAX)) {
303 spin_unlock_irq(&zone->lru_lock);
304 locked = false;
305 }
306 if (need_resched() || spin_is_contended(&zone->lru_lock)) {
307 if (locked)
308 spin_unlock_irq(&zone->lru_lock);
309 cond_resched();
310 spin_lock_irq(&zone->lru_lock);
311 if (fatal_signal_pending(current))
312 break;
313 } else if (!locked)
314 spin_lock_irq(&zone->lru_lock);
315
Mel Gorman0bf380b2012-02-03 15:37:18 -0800316 /*
317 * migrate_pfn does not necessarily start aligned to a
318 * pageblock. Ensure that pfn_valid is called when moving
319 * into a new MAX_ORDER_NR_PAGES range in case of large
320 * memory holes within the zone
321 */
322 if ((low_pfn & (MAX_ORDER_NR_PAGES - 1)) == 0) {
323 if (!pfn_valid(low_pfn)) {
324 low_pfn += MAX_ORDER_NR_PAGES - 1;
325 continue;
326 }
327 }
328
Mel Gorman748446b2010-05-24 14:32:27 -0700329 if (!pfn_valid_within(low_pfn))
330 continue;
Mel Gormanb7aba692011-01-13 15:45:54 -0800331 nr_scanned++;
Mel Gorman748446b2010-05-24 14:32:27 -0700332
Mel Gormandc908602012-02-08 17:13:38 -0800333 /*
334 * Get the page and ensure the page is within the same zone.
335 * See the comment in isolate_freepages about overlapping
336 * nodes. It is deliberate that the new zone lock is not taken
337 * as memory compaction should not move pages between nodes.
338 */
Mel Gorman748446b2010-05-24 14:32:27 -0700339 page = pfn_to_page(low_pfn);
Mel Gormandc908602012-02-08 17:13:38 -0800340 if (page_zone(page) != zone)
341 continue;
342
343 /* Skip if free */
Mel Gorman748446b2010-05-24 14:32:27 -0700344 if (PageBuddy(page))
345 continue;
346
Mel Gorman9927af742011-01-13 15:45:59 -0800347 /*
348 * For async migration, also only scan in MOVABLE blocks. Async
349 * migration is optimistic to see if the minimum amount of work
350 * satisfies the allocation
351 */
352 pageblock_nr = low_pfn >> pageblock_order;
353 if (!cc->sync && last_pageblock_nr != pageblock_nr &&
354 get_pageblock_migratetype(page) != MIGRATE_MOVABLE) {
355 low_pfn += pageblock_nr_pages;
356 low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
357 last_pageblock_nr = pageblock_nr;
358 continue;
359 }
360
Andrea Arcangelibc835012011-01-13 15:47:08 -0800361 if (!PageLRU(page))
362 continue;
363
364 /*
365 * PageLRU is set, and lru_lock excludes isolation,
366 * splitting and collapsing (collapsing has already
367 * happened if PageLRU is set).
368 */
369 if (PageTransHuge(page)) {
370 low_pfn += (1 << compound_order(page)) - 1;
371 continue;
372 }
373
Mel Gormanc8244932012-01-12 17:19:38 -0800374 if (!cc->sync)
375 mode |= ISOLATE_ASYNC_MIGRATE;
376
Mel Gorman748446b2010-05-24 14:32:27 -0700377 /* Try isolate the page */
Minchan Kim39deaf82011-10-31 17:06:51 -0700378 if (__isolate_lru_page(page, mode, 0) != 0)
Mel Gorman748446b2010-05-24 14:32:27 -0700379 continue;
380
Andrea Arcangelibc835012011-01-13 15:47:08 -0800381 VM_BUG_ON(PageTransCompound(page));
382
Mel Gorman748446b2010-05-24 14:32:27 -0700383 /* Successfully isolated */
384 del_page_from_lru_list(zone, page, page_lru(page));
385 list_add(&page->lru, migratelist);
Mel Gorman748446b2010-05-24 14:32:27 -0700386 cc->nr_migratepages++;
Mel Gormanb7aba692011-01-13 15:45:54 -0800387 nr_isolated++;
Mel Gorman748446b2010-05-24 14:32:27 -0700388
389 /* Avoid isolating too much */
Hillf Danton31b83842012-01-10 15:07:59 -0800390 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
391 ++low_pfn;
Mel Gorman748446b2010-05-24 14:32:27 -0700392 break;
Hillf Danton31b83842012-01-10 15:07:59 -0800393 }
Mel Gorman748446b2010-05-24 14:32:27 -0700394 }
395
396 acct_isolated(zone, cc);
397
398 spin_unlock_irq(&zone->lru_lock);
399 cc->migrate_pfn = low_pfn;
400
Mel Gormanb7aba692011-01-13 15:45:54 -0800401 trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
402
Mel Gormanf9e35b32011-06-15 15:08:52 -0700403 return ISOLATE_SUCCESS;
Mel Gorman748446b2010-05-24 14:32:27 -0700404}
405
406/*
407 * This is a migrate-callback that "allocates" freepages by taking pages
408 * from the isolated freelists in the block we are migrating to.
409 */
410static struct page *compaction_alloc(struct page *migratepage,
411 unsigned long data,
412 int **result)
413{
414 struct compact_control *cc = (struct compact_control *)data;
415 struct page *freepage;
416
417 /* Isolate free pages if necessary */
418 if (list_empty(&cc->freepages)) {
419 isolate_freepages(cc->zone, cc);
420
421 if (list_empty(&cc->freepages))
422 return NULL;
423 }
424
425 freepage = list_entry(cc->freepages.next, struct page, lru);
426 list_del(&freepage->lru);
427 cc->nr_freepages--;
428
429 return freepage;
430}
431
432/*
433 * We cannot control nr_migratepages and nr_freepages fully when migration is
434 * running as migrate_pages() has no knowledge of compact_control. When
435 * migration is complete, we count the number of pages on the lists by hand.
436 */
437static void update_nr_listpages(struct compact_control *cc)
438{
439 int nr_migratepages = 0;
440 int nr_freepages = 0;
441 struct page *page;
442
443 list_for_each_entry(page, &cc->migratepages, lru)
444 nr_migratepages++;
445 list_for_each_entry(page, &cc->freepages, lru)
446 nr_freepages++;
447
448 cc->nr_migratepages = nr_migratepages;
449 cc->nr_freepages = nr_freepages;
450}
451
452static int compact_finished(struct zone *zone,
Andrea Arcangeli5a03b052011-01-13 15:47:11 -0800453 struct compact_control *cc)
Mel Gorman748446b2010-05-24 14:32:27 -0700454{
Mel Gorman56de7262010-05-24 14:32:30 -0700455 unsigned int order;
Andrea Arcangeli5a03b052011-01-13 15:47:11 -0800456 unsigned long watermark;
Mel Gorman56de7262010-05-24 14:32:30 -0700457
Mel Gorman748446b2010-05-24 14:32:27 -0700458 if (fatal_signal_pending(current))
459 return COMPACT_PARTIAL;
460
461 /* Compaction run completes if the migrate and free scanner meet */
462 if (cc->free_pfn <= cc->migrate_pfn)
463 return COMPACT_COMPLETE;
464
Johannes Weiner82478fb2011-01-20 14:44:21 -0800465 /*
466 * order == -1 is expected when compacting via
467 * /proc/sys/vm/compact_memory
468 */
Mel Gorman56de7262010-05-24 14:32:30 -0700469 if (cc->order == -1)
470 return COMPACT_CONTINUE;
471
Michal Hocko3957c772011-06-15 15:08:25 -0700472 /* Compaction run is not finished if the watermark is not met */
473 watermark = low_wmark_pages(zone);
474 watermark += (1 << cc->order);
475
476 if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
477 return COMPACT_CONTINUE;
478
Mel Gorman56de7262010-05-24 14:32:30 -0700479 /* Direct compactor: Is a suitable page free? */
480 for (order = cc->order; order < MAX_ORDER; order++) {
481 /* Job done if page is free of the right migratetype */
482 if (!list_empty(&zone->free_area[order].free_list[cc->migratetype]))
483 return COMPACT_PARTIAL;
484
485 /* Job done if allocation would set block type */
486 if (order >= pageblock_order && zone->free_area[order].nr_free)
487 return COMPACT_PARTIAL;
488 }
489
Mel Gorman748446b2010-05-24 14:32:27 -0700490 return COMPACT_CONTINUE;
491}
492
Mel Gorman3e7d3442011-01-13 15:45:56 -0800493/*
494 * compaction_suitable: Is this suitable to run compaction on this zone now?
495 * Returns
496 * COMPACT_SKIPPED - If there are too few free pages for compaction
497 * COMPACT_PARTIAL - If the allocation would succeed without compaction
498 * COMPACT_CONTINUE - If compaction should run now
499 */
500unsigned long compaction_suitable(struct zone *zone, int order)
501{
502 int fragindex;
503 unsigned long watermark;
504
505 /*
Michal Hocko3957c772011-06-15 15:08:25 -0700506 * order == -1 is expected when compacting via
507 * /proc/sys/vm/compact_memory
508 */
509 if (order == -1)
510 return COMPACT_CONTINUE;
511
512 /*
Mel Gorman3e7d3442011-01-13 15:45:56 -0800513 * Watermarks for order-0 must be met for compaction. Note the 2UL.
514 * This is because during migration, copies of pages need to be
515 * allocated and for a short time, the footprint is higher
516 */
517 watermark = low_wmark_pages(zone) + (2UL << order);
518 if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
519 return COMPACT_SKIPPED;
520
521 /*
522 * fragmentation index determines if allocation failures are due to
523 * low memory or external fragmentation
524 *
Shaohua Lia582a732011-06-15 15:08:49 -0700525 * index of -1000 implies allocations might succeed depending on
526 * watermarks
Mel Gorman3e7d3442011-01-13 15:45:56 -0800527 * index towards 0 implies failure is due to lack of memory
528 * index towards 1000 implies failure is due to fragmentation
529 *
530 * Only compact if a failure would be due to fragmentation.
531 */
532 fragindex = fragmentation_index(zone, order);
533 if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
534 return COMPACT_SKIPPED;
535
Shaohua Lia582a732011-06-15 15:08:49 -0700536 if (fragindex == -1000 && zone_watermark_ok(zone, order, watermark,
537 0, 0))
Mel Gorman3e7d3442011-01-13 15:45:56 -0800538 return COMPACT_PARTIAL;
539
540 return COMPACT_CONTINUE;
541}
542
Mel Gorman748446b2010-05-24 14:32:27 -0700543static int compact_zone(struct zone *zone, struct compact_control *cc)
544{
545 int ret;
546
Mel Gorman3e7d3442011-01-13 15:45:56 -0800547 ret = compaction_suitable(zone, cc->order);
548 switch (ret) {
549 case COMPACT_PARTIAL:
550 case COMPACT_SKIPPED:
551 /* Compaction is likely to fail */
552 return ret;
553 case COMPACT_CONTINUE:
554 /* Fall through to compaction */
555 ;
556 }
557
Mel Gorman748446b2010-05-24 14:32:27 -0700558 /* Setup to move all movable pages to the end of the zone */
559 cc->migrate_pfn = zone->zone_start_pfn;
560 cc->free_pfn = cc->migrate_pfn + zone->spanned_pages;
561 cc->free_pfn &= ~(pageblock_nr_pages-1);
562
563 migrate_prep_local();
564
565 while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
566 unsigned long nr_migrate, nr_remaining;
Minchan Kim9d502c12011-03-22 16:30:39 -0700567 int err;
Mel Gorman748446b2010-05-24 14:32:27 -0700568
Mel Gormanf9e35b32011-06-15 15:08:52 -0700569 switch (isolate_migratepages(zone, cc)) {
570 case ISOLATE_ABORT:
571 ret = COMPACT_PARTIAL;
572 goto out;
573 case ISOLATE_NONE:
Mel Gorman748446b2010-05-24 14:32:27 -0700574 continue;
Mel Gormanf9e35b32011-06-15 15:08:52 -0700575 case ISOLATE_SUCCESS:
576 ;
577 }
Mel Gorman748446b2010-05-24 14:32:27 -0700578
579 nr_migrate = cc->nr_migratepages;
Minchan Kim9d502c12011-03-22 16:30:39 -0700580 err = migrate_pages(&cc->migratepages, compaction_alloc,
Mel Gorman7f0f2492011-01-13 15:45:58 -0800581 (unsigned long)cc, false,
Mel Gormana6bc32b2012-01-12 17:19:43 -0800582 cc->sync ? MIGRATE_SYNC_LIGHT : MIGRATE_ASYNC);
Mel Gorman748446b2010-05-24 14:32:27 -0700583 update_nr_listpages(cc);
584 nr_remaining = cc->nr_migratepages;
585
586 count_vm_event(COMPACTBLOCKS);
587 count_vm_events(COMPACTPAGES, nr_migrate - nr_remaining);
588 if (nr_remaining)
589 count_vm_events(COMPACTPAGEFAILED, nr_remaining);
Mel Gormanb7aba692011-01-13 15:45:54 -0800590 trace_mm_compaction_migratepages(nr_migrate - nr_remaining,
591 nr_remaining);
Mel Gorman748446b2010-05-24 14:32:27 -0700592
593 /* Release LRU pages not migrated */
Minchan Kim9d502c12011-03-22 16:30:39 -0700594 if (err) {
Mel Gorman748446b2010-05-24 14:32:27 -0700595 putback_lru_pages(&cc->migratepages);
596 cc->nr_migratepages = 0;
597 }
598
599 }
600
Mel Gormanf9e35b32011-06-15 15:08:52 -0700601out:
Mel Gorman748446b2010-05-24 14:32:27 -0700602 /* Release free pages and check accounting */
603 cc->nr_freepages -= release_freepages(&cc->freepages);
604 VM_BUG_ON(cc->nr_freepages != 0);
605
606 return ret;
607}
Mel Gorman76ab0f52010-05-24 14:32:28 -0700608
Kyungmin Parkd43a87e2011-10-31 17:09:08 -0700609static unsigned long compact_zone_order(struct zone *zone,
Andrea Arcangeli5a03b052011-01-13 15:47:11 -0800610 int order, gfp_t gfp_mask,
Andrea Arcangelid527caf2011-03-22 16:30:38 -0700611 bool sync)
Mel Gorman56de7262010-05-24 14:32:30 -0700612{
613 struct compact_control cc = {
614 .nr_freepages = 0,
615 .nr_migratepages = 0,
616 .order = order,
617 .migratetype = allocflags_to_migratetype(gfp_mask),
618 .zone = zone,
Mel Gorman77f1fe62011-01-13 15:45:57 -0800619 .sync = sync,
Mel Gorman56de7262010-05-24 14:32:30 -0700620 };
621 INIT_LIST_HEAD(&cc.freepages);
622 INIT_LIST_HEAD(&cc.migratepages);
623
624 return compact_zone(zone, &cc);
625}
626
Mel Gorman5e771902010-05-24 14:32:31 -0700627int sysctl_extfrag_threshold = 500;
628
Mel Gorman56de7262010-05-24 14:32:30 -0700629/**
630 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
631 * @zonelist: The zonelist used for the current allocation
632 * @order: The order of the current allocation
633 * @gfp_mask: The GFP mask of the current allocation
634 * @nodemask: The allowed nodes to allocate from
Mel Gorman77f1fe62011-01-13 15:45:57 -0800635 * @sync: Whether migration is synchronous or not
Mel Gorman56de7262010-05-24 14:32:30 -0700636 *
637 * This is the main entry point for direct page compaction.
638 */
639unsigned long try_to_compact_pages(struct zonelist *zonelist,
Mel Gorman77f1fe62011-01-13 15:45:57 -0800640 int order, gfp_t gfp_mask, nodemask_t *nodemask,
641 bool sync)
Mel Gorman56de7262010-05-24 14:32:30 -0700642{
643 enum zone_type high_zoneidx = gfp_zone(gfp_mask);
644 int may_enter_fs = gfp_mask & __GFP_FS;
645 int may_perform_io = gfp_mask & __GFP_IO;
Mel Gorman56de7262010-05-24 14:32:30 -0700646 struct zoneref *z;
647 struct zone *zone;
648 int rc = COMPACT_SKIPPED;
649
650 /*
651 * Check whether it is worth even starting compaction. The order check is
652 * made because an assumption is made that the page allocator can satisfy
653 * the "cheaper" orders without taking special steps
654 */
Andrea Arcangelic5a73c32011-01-13 15:47:11 -0800655 if (!order || !may_enter_fs || !may_perform_io)
Mel Gorman56de7262010-05-24 14:32:30 -0700656 return rc;
657
658 count_vm_event(COMPACTSTALL);
659
660 /* Compact each zone in the list */
661 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
662 nodemask) {
Mel Gorman56de7262010-05-24 14:32:30 -0700663 int status;
664
Andrea Arcangelid527caf2011-03-22 16:30:38 -0700665 status = compact_zone_order(zone, order, gfp_mask, sync);
Mel Gorman56de7262010-05-24 14:32:30 -0700666 rc = max(status, rc);
667
Mel Gorman3e7d3442011-01-13 15:45:56 -0800668 /* If a normal allocation would succeed, stop compacting */
669 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
Mel Gorman56de7262010-05-24 14:32:30 -0700670 break;
671 }
672
673 return rc;
674}
675
676
Mel Gorman76ab0f52010-05-24 14:32:28 -0700677/* Compact all zones within a node */
678static int compact_node(int nid)
679{
680 int zoneid;
681 pg_data_t *pgdat;
682 struct zone *zone;
683
684 if (nid < 0 || nid >= nr_node_ids || !node_online(nid))
685 return -EINVAL;
686 pgdat = NODE_DATA(nid);
687
688 /* Flush pending updates to the LRU lists */
689 lru_add_drain_all();
690
691 for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
692 struct compact_control cc = {
693 .nr_freepages = 0,
694 .nr_migratepages = 0,
Mel Gorman56de7262010-05-24 14:32:30 -0700695 .order = -1,
Mel Gormanb16d3d52012-01-12 17:19:26 -0800696 .sync = true,
Mel Gorman76ab0f52010-05-24 14:32:28 -0700697 };
698
699 zone = &pgdat->node_zones[zoneid];
700 if (!populated_zone(zone))
701 continue;
702
703 cc.zone = zone;
704 INIT_LIST_HEAD(&cc.freepages);
705 INIT_LIST_HEAD(&cc.migratepages);
706
707 compact_zone(zone, &cc);
708
709 VM_BUG_ON(!list_empty(&cc.freepages));
710 VM_BUG_ON(!list_empty(&cc.migratepages));
711 }
712
713 return 0;
714}
715
716/* Compact all nodes in the system */
717static int compact_nodes(void)
718{
719 int nid;
720
721 for_each_online_node(nid)
722 compact_node(nid);
723
724 return COMPACT_COMPLETE;
725}
726
727/* The written value is actually unused, all memory is compacted */
728int sysctl_compact_memory;
729
730/* This is the entry point for compacting all nodes via /proc/sys/vm */
731int sysctl_compaction_handler(struct ctl_table *table, int write,
732 void __user *buffer, size_t *length, loff_t *ppos)
733{
734 if (write)
735 return compact_nodes();
736
737 return 0;
738}
Mel Gormaned4a6d72010-05-24 14:32:29 -0700739
Mel Gorman5e771902010-05-24 14:32:31 -0700740int sysctl_extfrag_handler(struct ctl_table *table, int write,
741 void __user *buffer, size_t *length, loff_t *ppos)
742{
743 proc_dointvec_minmax(table, write, buffer, length, ppos);
744
745 return 0;
746}
747
Mel Gormaned4a6d72010-05-24 14:32:29 -0700748#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
Kay Sievers10fbcf42011-12-21 14:48:43 -0800749ssize_t sysfs_compact_node(struct device *dev,
750 struct device_attribute *attr,
Mel Gormaned4a6d72010-05-24 14:32:29 -0700751 const char *buf, size_t count)
752{
753 compact_node(dev->id);
754
755 return count;
756}
Kay Sievers10fbcf42011-12-21 14:48:43 -0800757static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
Mel Gormaned4a6d72010-05-24 14:32:29 -0700758
759int compaction_register_node(struct node *node)
760{
Kay Sievers10fbcf42011-12-21 14:48:43 -0800761 return device_create_file(&node->dev, &dev_attr_compact);
Mel Gormaned4a6d72010-05-24 14:32:29 -0700762}
763
764void compaction_unregister_node(struct node *node)
765{
Kay Sievers10fbcf42011-12-21 14:48:43 -0800766 return device_remove_file(&node->dev, &dev_attr_compact);
Mel Gormaned4a6d72010-05-24 14:32:29 -0700767}
768#endif /* CONFIG_SYSFS && CONFIG_NUMA */