Root/
1 | /* |
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> |
15 | #include <linux/sysctl.h> |
16 | #include <linux/sysfs.h> |
17 | #include "internal.h" |
18 | |
19 | /* |
20 | * compact_control is used to track pages being migrated and the free pages |
21 | * they are being migrated to during memory compaction. The free_pfn starts |
22 | * at the end of a zone and migrate_pfn begins at the start. Movable pages |
23 | * are moved to the end of a zone during a compaction run and the run |
24 | * completes when free_pfn <= migrate_pfn |
25 | */ |
26 | struct compact_control { |
27 | struct list_head freepages; /* List of free pages to migrate to */ |
28 | struct list_head migratepages; /* List of pages being migrated */ |
29 | unsigned long nr_freepages; /* Number of isolated free pages */ |
30 | unsigned long nr_migratepages; /* Number of pages to migrate */ |
31 | unsigned long free_pfn; /* isolate_freepages search base */ |
32 | unsigned long migrate_pfn; /* isolate_migratepages search base */ |
33 | |
34 | /* Account for isolated anon and file pages */ |
35 | unsigned long nr_anon; |
36 | unsigned long nr_file; |
37 | |
38 | unsigned int order; /* order a direct compactor needs */ |
39 | int migratetype; /* MOVABLE, RECLAIMABLE etc */ |
40 | struct zone *zone; |
41 | }; |
42 | |
43 | static 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 */ |
58 | static 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; |
63 | int total_isolated = 0; |
64 | 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; |
84 | |
85 | if (!PageBuddy(page)) |
86 | continue; |
87 | |
88 | /* Found a free page, break it into order-0 pages */ |
89 | isolated = split_free_page(page); |
90 | total_isolated += isolated; |
91 | for (i = 0; i < isolated; i++) { |
92 | list_add(&page->lru, freelist); |
93 | page++; |
94 | } |
95 | |
96 | /* If a page was split, advance to the end of it */ |
97 | if (isolated) { |
98 | blockpfn += isolated - 1; |
99 | cursor += isolated - 1; |
100 | } |
101 | } |
102 | |
103 | return total_isolated; |
104 | } |
105 | |
106 | /* Returns true if the page is within a block suitable for migration to */ |
107 | static bool suitable_migration_target(struct page *page) |
108 | { |
109 | |
110 | int migratetype = get_pageblock_migratetype(page); |
111 | |
112 | /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */ |
113 | if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE) |
114 | return false; |
115 | |
116 | /* If the page is a large free page, then allow migration */ |
117 | if (PageBuddy(page) && page_order(page) >= pageblock_order) |
118 | return true; |
119 | |
120 | /* If the block is MIGRATE_MOVABLE, allow migration */ |
121 | if (migratetype == MIGRATE_MOVABLE) |
122 | return true; |
123 | |
124 | /* Otherwise skip the block */ |
125 | return false; |
126 | } |
127 | |
128 | /* |
129 | * Based on information in the current compact_control, find blocks |
130 | * suitable for isolating free pages from and then isolate them. |
131 | */ |
132 | static void isolate_freepages(struct zone *zone, |
133 | struct compact_control *cc) |
134 | { |
135 | struct page *page; |
136 | unsigned long high_pfn, low_pfn, pfn; |
137 | unsigned long flags; |
138 | int nr_freepages = cc->nr_freepages; |
139 | struct list_head *freelist = &cc->freepages; |
140 | |
141 | pfn = cc->free_pfn; |
142 | low_pfn = cc->migrate_pfn + pageblock_nr_pages; |
143 | high_pfn = low_pfn; |
144 | |
145 | /* |
146 | * Isolate free pages until enough are available to migrate the |
147 | * pages on cc->migratepages. We stop searching if the migrate |
148 | * and free page scanners meet or enough free pages are isolated. |
149 | */ |
150 | spin_lock_irqsave(&zone->lock, flags); |
151 | for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages; |
152 | pfn -= pageblock_nr_pages) { |
153 | unsigned long isolated; |
154 | |
155 | if (!pfn_valid(pfn)) |
156 | continue; |
157 | |
158 | /* |
159 | * Check for overlapping nodes/zones. It's possible on some |
160 | * configurations to have a setup like |
161 | * node0 node1 node0 |
162 | * i.e. it's possible that all pages within a zones range of |
163 | * pages do not belong to a single zone. |
164 | */ |
165 | page = pfn_to_page(pfn); |
166 | if (page_zone(page) != zone) |
167 | continue; |
168 | |
169 | /* Check the block is suitable for migration */ |
170 | if (!suitable_migration_target(page)) |
171 | continue; |
172 | |
173 | /* Found a block suitable for isolating free pages from */ |
174 | isolated = isolate_freepages_block(zone, pfn, freelist); |
175 | nr_freepages += isolated; |
176 | |
177 | /* |
178 | * Record the highest PFN we isolated pages from. When next |
179 | * looking for free pages, the search will restart here as |
180 | * page migration may have returned some pages to the allocator |
181 | */ |
182 | if (isolated) |
183 | high_pfn = max(high_pfn, pfn); |
184 | } |
185 | spin_unlock_irqrestore(&zone->lock, flags); |
186 | |
187 | /* split_free_page does not map the pages */ |
188 | list_for_each_entry(page, freelist, lru) { |
189 | arch_alloc_page(page, 0); |
190 | kernel_map_pages(page, 1, 1); |
191 | } |
192 | |
193 | cc->free_pfn = high_pfn; |
194 | cc->nr_freepages = nr_freepages; |
195 | } |
196 | |
197 | /* Update the number of anon and file isolated pages in the zone */ |
198 | static void acct_isolated(struct zone *zone, struct compact_control *cc) |
199 | { |
200 | struct page *page; |
201 | unsigned int count[NR_LRU_LISTS] = { 0, }; |
202 | |
203 | list_for_each_entry(page, &cc->migratepages, lru) { |
204 | int lru = page_lru_base_type(page); |
205 | count[lru]++; |
206 | } |
207 | |
208 | cc->nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; |
209 | cc->nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; |
210 | __mod_zone_page_state(zone, NR_ISOLATED_ANON, cc->nr_anon); |
211 | __mod_zone_page_state(zone, NR_ISOLATED_FILE, cc->nr_file); |
212 | } |
213 | |
214 | /* Similar to reclaim, but different enough that they don't share logic */ |
215 | static bool too_many_isolated(struct zone *zone) |
216 | { |
217 | |
218 | unsigned long inactive, isolated; |
219 | |
220 | inactive = zone_page_state(zone, NR_INACTIVE_FILE) + |
221 | zone_page_state(zone, NR_INACTIVE_ANON); |
222 | isolated = zone_page_state(zone, NR_ISOLATED_FILE) + |
223 | zone_page_state(zone, NR_ISOLATED_ANON); |
224 | |
225 | return isolated > inactive; |
226 | } |
227 | |
228 | /* |
229 | * Isolate all pages that can be migrated from the block pointed to by |
230 | * the migrate scanner within compact_control. |
231 | */ |
232 | static unsigned long isolate_migratepages(struct zone *zone, |
233 | struct compact_control *cc) |
234 | { |
235 | unsigned long low_pfn, end_pfn; |
236 | struct list_head *migratelist = &cc->migratepages; |
237 | |
238 | /* Do not scan outside zone boundaries */ |
239 | low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn); |
240 | |
241 | /* Only scan within a pageblock boundary */ |
242 | end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages); |
243 | |
244 | /* Do not cross the free scanner or scan within a memory hole */ |
245 | if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) { |
246 | cc->migrate_pfn = end_pfn; |
247 | return 0; |
248 | } |
249 | |
250 | /* |
251 | * Ensure that there are not too many pages isolated from the LRU |
252 | * list by either parallel reclaimers or compaction. If there are, |
253 | * delay for some time until fewer pages are isolated |
254 | */ |
255 | while (unlikely(too_many_isolated(zone))) { |
256 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
257 | |
258 | if (fatal_signal_pending(current)) |
259 | return 0; |
260 | } |
261 | |
262 | /* Time to isolate some pages for migration */ |
263 | spin_lock_irq(&zone->lru_lock); |
264 | for (; low_pfn < end_pfn; low_pfn++) { |
265 | struct page *page; |
266 | if (!pfn_valid_within(low_pfn)) |
267 | continue; |
268 | |
269 | /* Get the page and skip if free */ |
270 | page = pfn_to_page(low_pfn); |
271 | if (PageBuddy(page)) |
272 | continue; |
273 | |
274 | /* Try isolate the page */ |
275 | if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0) |
276 | continue; |
277 | |
278 | /* Successfully isolated */ |
279 | del_page_from_lru_list(zone, page, page_lru(page)); |
280 | list_add(&page->lru, migratelist); |
281 | mem_cgroup_del_lru(page); |
282 | cc->nr_migratepages++; |
283 | |
284 | /* Avoid isolating too much */ |
285 | if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) |
286 | break; |
287 | } |
288 | |
289 | acct_isolated(zone, cc); |
290 | |
291 | spin_unlock_irq(&zone->lru_lock); |
292 | cc->migrate_pfn = low_pfn; |
293 | |
294 | return cc->nr_migratepages; |
295 | } |
296 | |
297 | /* |
298 | * This is a migrate-callback that "allocates" freepages by taking pages |
299 | * from the isolated freelists in the block we are migrating to. |
300 | */ |
301 | static struct page *compaction_alloc(struct page *migratepage, |
302 | unsigned long data, |
303 | int **result) |
304 | { |
305 | struct compact_control *cc = (struct compact_control *)data; |
306 | struct page *freepage; |
307 | |
308 | /* Isolate free pages if necessary */ |
309 | if (list_empty(&cc->freepages)) { |
310 | isolate_freepages(cc->zone, cc); |
311 | |
312 | if (list_empty(&cc->freepages)) |
313 | return NULL; |
314 | } |
315 | |
316 | freepage = list_entry(cc->freepages.next, struct page, lru); |
317 | list_del(&freepage->lru); |
318 | cc->nr_freepages--; |
319 | |
320 | return freepage; |
321 | } |
322 | |
323 | /* |
324 | * We cannot control nr_migratepages and nr_freepages fully when migration is |
325 | * running as migrate_pages() has no knowledge of compact_control. When |
326 | * migration is complete, we count the number of pages on the lists by hand. |
327 | */ |
328 | static void update_nr_listpages(struct compact_control *cc) |
329 | { |
330 | int nr_migratepages = 0; |
331 | int nr_freepages = 0; |
332 | struct page *page; |
333 | |
334 | list_for_each_entry(page, &cc->migratepages, lru) |
335 | nr_migratepages++; |
336 | list_for_each_entry(page, &cc->freepages, lru) |
337 | nr_freepages++; |
338 | |
339 | cc->nr_migratepages = nr_migratepages; |
340 | cc->nr_freepages = nr_freepages; |
341 | } |
342 | |
343 | static int compact_finished(struct zone *zone, |
344 | struct compact_control *cc) |
345 | { |
346 | unsigned int order; |
347 | unsigned long watermark = low_wmark_pages(zone) + (1 << cc->order); |
348 | |
349 | if (fatal_signal_pending(current)) |
350 | return COMPACT_PARTIAL; |
351 | |
352 | /* Compaction run completes if the migrate and free scanner meet */ |
353 | if (cc->free_pfn <= cc->migrate_pfn) |
354 | return COMPACT_COMPLETE; |
355 | |
356 | /* Compaction run is not finished if the watermark is not met */ |
357 | if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0)) |
358 | return COMPACT_CONTINUE; |
359 | |
360 | if (cc->order == -1) |
361 | return COMPACT_CONTINUE; |
362 | |
363 | /* Direct compactor: Is a suitable page free? */ |
364 | for (order = cc->order; order < MAX_ORDER; order++) { |
365 | /* Job done if page is free of the right migratetype */ |
366 | if (!list_empty(&zone->free_area[order].free_list[cc->migratetype])) |
367 | return COMPACT_PARTIAL; |
368 | |
369 | /* Job done if allocation would set block type */ |
370 | if (order >= pageblock_order && zone->free_area[order].nr_free) |
371 | return COMPACT_PARTIAL; |
372 | } |
373 | |
374 | return COMPACT_CONTINUE; |
375 | } |
376 | |
377 | static int compact_zone(struct zone *zone, struct compact_control *cc) |
378 | { |
379 | int ret; |
380 | |
381 | /* Setup to move all movable pages to the end of the zone */ |
382 | cc->migrate_pfn = zone->zone_start_pfn; |
383 | cc->free_pfn = cc->migrate_pfn + zone->spanned_pages; |
384 | cc->free_pfn &= ~(pageblock_nr_pages-1); |
385 | |
386 | migrate_prep_local(); |
387 | |
388 | while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) { |
389 | unsigned long nr_migrate, nr_remaining; |
390 | |
391 | if (!isolate_migratepages(zone, cc)) |
392 | continue; |
393 | |
394 | nr_migrate = cc->nr_migratepages; |
395 | migrate_pages(&cc->migratepages, compaction_alloc, |
396 | (unsigned long)cc, 0); |
397 | update_nr_listpages(cc); |
398 | nr_remaining = cc->nr_migratepages; |
399 | |
400 | count_vm_event(COMPACTBLOCKS); |
401 | count_vm_events(COMPACTPAGES, nr_migrate - nr_remaining); |
402 | if (nr_remaining) |
403 | count_vm_events(COMPACTPAGEFAILED, nr_remaining); |
404 | |
405 | /* Release LRU pages not migrated */ |
406 | if (!list_empty(&cc->migratepages)) { |
407 | putback_lru_pages(&cc->migratepages); |
408 | cc->nr_migratepages = 0; |
409 | } |
410 | |
411 | } |
412 | |
413 | /* Release free pages and check accounting */ |
414 | cc->nr_freepages -= release_freepages(&cc->freepages); |
415 | VM_BUG_ON(cc->nr_freepages != 0); |
416 | |
417 | return ret; |
418 | } |
419 | |
420 | static unsigned long compact_zone_order(struct zone *zone, |
421 | int order, gfp_t gfp_mask) |
422 | { |
423 | struct compact_control cc = { |
424 | .nr_freepages = 0, |
425 | .nr_migratepages = 0, |
426 | .order = order, |
427 | .migratetype = allocflags_to_migratetype(gfp_mask), |
428 | .zone = zone, |
429 | }; |
430 | INIT_LIST_HEAD(&cc.freepages); |
431 | INIT_LIST_HEAD(&cc.migratepages); |
432 | |
433 | return compact_zone(zone, &cc); |
434 | } |
435 | |
436 | int sysctl_extfrag_threshold = 500; |
437 | |
438 | /** |
439 | * try_to_compact_pages - Direct compact to satisfy a high-order allocation |
440 | * @zonelist: The zonelist used for the current allocation |
441 | * @order: The order of the current allocation |
442 | * @gfp_mask: The GFP mask of the current allocation |
443 | * @nodemask: The allowed nodes to allocate from |
444 | * |
445 | * This is the main entry point for direct page compaction. |
446 | */ |
447 | unsigned long try_to_compact_pages(struct zonelist *zonelist, |
448 | int order, gfp_t gfp_mask, nodemask_t *nodemask) |
449 | { |
450 | enum zone_type high_zoneidx = gfp_zone(gfp_mask); |
451 | int may_enter_fs = gfp_mask & __GFP_FS; |
452 | int may_perform_io = gfp_mask & __GFP_IO; |
453 | unsigned long watermark; |
454 | struct zoneref *z; |
455 | struct zone *zone; |
456 | int rc = COMPACT_SKIPPED; |
457 | |
458 | /* |
459 | * Check whether it is worth even starting compaction. The order check is |
460 | * made because an assumption is made that the page allocator can satisfy |
461 | * the "cheaper" orders without taking special steps |
462 | */ |
463 | if (order <= PAGE_ALLOC_COSTLY_ORDER || !may_enter_fs || !may_perform_io) |
464 | return rc; |
465 | |
466 | count_vm_event(COMPACTSTALL); |
467 | |
468 | /* Compact each zone in the list */ |
469 | for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx, |
470 | nodemask) { |
471 | int fragindex; |
472 | int status; |
473 | |
474 | /* |
475 | * Watermarks for order-0 must be met for compaction. Note |
476 | * the 2UL. This is because during migration, copies of |
477 | * pages need to be allocated and for a short time, the |
478 | * footprint is higher |
479 | */ |
480 | watermark = low_wmark_pages(zone) + (2UL << order); |
481 | if (!zone_watermark_ok(zone, 0, watermark, 0, 0)) |
482 | continue; |
483 | |
484 | /* |
485 | * fragmentation index determines if allocation failures are |
486 | * due to low memory or external fragmentation |
487 | * |
488 | * index of -1 implies allocations might succeed depending |
489 | * on watermarks |
490 | * index towards 0 implies failure is due to lack of memory |
491 | * index towards 1000 implies failure is due to fragmentation |
492 | * |
493 | * Only compact if a failure would be due to fragmentation. |
494 | */ |
495 | fragindex = fragmentation_index(zone, order); |
496 | if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold) |
497 | continue; |
498 | |
499 | if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0)) { |
500 | rc = COMPACT_PARTIAL; |
501 | break; |
502 | } |
503 | |
504 | status = compact_zone_order(zone, order, gfp_mask); |
505 | rc = max(status, rc); |
506 | |
507 | if (zone_watermark_ok(zone, order, watermark, 0, 0)) |
508 | break; |
509 | } |
510 | |
511 | return rc; |
512 | } |
513 | |
514 | |
515 | /* Compact all zones within a node */ |
516 | static int compact_node(int nid) |
517 | { |
518 | int zoneid; |
519 | pg_data_t *pgdat; |
520 | struct zone *zone; |
521 | |
522 | if (nid < 0 || nid >= nr_node_ids || !node_online(nid)) |
523 | return -EINVAL; |
524 | pgdat = NODE_DATA(nid); |
525 | |
526 | /* Flush pending updates to the LRU lists */ |
527 | lru_add_drain_all(); |
528 | |
529 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
530 | struct compact_control cc = { |
531 | .nr_freepages = 0, |
532 | .nr_migratepages = 0, |
533 | .order = -1, |
534 | }; |
535 | |
536 | zone = &pgdat->node_zones[zoneid]; |
537 | if (!populated_zone(zone)) |
538 | continue; |
539 | |
540 | cc.zone = zone; |
541 | INIT_LIST_HEAD(&cc.freepages); |
542 | INIT_LIST_HEAD(&cc.migratepages); |
543 | |
544 | compact_zone(zone, &cc); |
545 | |
546 | VM_BUG_ON(!list_empty(&cc.freepages)); |
547 | VM_BUG_ON(!list_empty(&cc.migratepages)); |
548 | } |
549 | |
550 | return 0; |
551 | } |
552 | |
553 | /* Compact all nodes in the system */ |
554 | static int compact_nodes(void) |
555 | { |
556 | int nid; |
557 | |
558 | for_each_online_node(nid) |
559 | compact_node(nid); |
560 | |
561 | return COMPACT_COMPLETE; |
562 | } |
563 | |
564 | /* The written value is actually unused, all memory is compacted */ |
565 | int sysctl_compact_memory; |
566 | |
567 | /* This is the entry point for compacting all nodes via /proc/sys/vm */ |
568 | int sysctl_compaction_handler(struct ctl_table *table, int write, |
569 | void __user *buffer, size_t *length, loff_t *ppos) |
570 | { |
571 | if (write) |
572 | return compact_nodes(); |
573 | |
574 | return 0; |
575 | } |
576 | |
577 | int sysctl_extfrag_handler(struct ctl_table *table, int write, |
578 | void __user *buffer, size_t *length, loff_t *ppos) |
579 | { |
580 | proc_dointvec_minmax(table, write, buffer, length, ppos); |
581 | |
582 | return 0; |
583 | } |
584 | |
585 | #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) |
586 | ssize_t sysfs_compact_node(struct sys_device *dev, |
587 | struct sysdev_attribute *attr, |
588 | const char *buf, size_t count) |
589 | { |
590 | compact_node(dev->id); |
591 | |
592 | return count; |
593 | } |
594 | static SYSDEV_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node); |
595 | |
596 | int compaction_register_node(struct node *node) |
597 | { |
598 | return sysdev_create_file(&node->sysdev, &attr_compact); |
599 | } |
600 | |
601 | void compaction_unregister_node(struct node *node) |
602 | { |
603 | return sysdev_remove_file(&node->sysdev, &attr_compact); |
604 | } |
605 | #endif /* CONFIG_SYSFS && CONFIG_NUMA */ |
606 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9