]>
git.ipfire.org Git - thirdparty/kernel/linux.git/blob - mm/compaction.c
2 * linux/mm/compaction.c
4 * Memory compaction for the reduction of external fragmentation. Note that
5 * this heavily depends upon page migration to do all the real heavy
8 * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
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>
19 #define CREATE_TRACE_POINTS
20 #include <trace/events/compaction.h>
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
29 struct 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 */
37 /* Account for isolated anon and file pages */
38 unsigned long nr_anon
;
39 unsigned long nr_file
;
41 unsigned int order
; /* order a direct compactor needs */
42 int migratetype
; /* MOVABLE, RECLAIMABLE etc */
46 static unsigned long release_freepages(struct list_head
*freelist
)
48 struct page
*page
, *next
;
49 unsigned long count
= 0;
51 list_for_each_entry_safe(page
, next
, freelist
, lru
) {
60 /* Isolate free pages onto a private freelist. Must hold zone->lock */
61 static unsigned long isolate_freepages_block(struct zone
*zone
,
62 unsigned long blockpfn
,
63 struct list_head
*freelist
)
65 unsigned long zone_end_pfn
, end_pfn
;
66 int nr_scanned
= 0, total_isolated
= 0;
69 /* Get the last PFN we should scan for free pages at */
70 zone_end_pfn
= zone
->zone_start_pfn
+ zone
->spanned_pages
;
71 end_pfn
= min(blockpfn
+ pageblock_nr_pages
, zone_end_pfn
);
73 /* Find the first usable PFN in the block to initialse page cursor */
74 for (; blockpfn
< end_pfn
; blockpfn
++) {
75 if (pfn_valid_within(blockpfn
))
78 cursor
= pfn_to_page(blockpfn
);
80 /* Isolate free pages. This assumes the block is valid */
81 for (; blockpfn
< end_pfn
; blockpfn
++, cursor
++) {
83 struct page
*page
= cursor
;
85 if (!pfn_valid_within(blockpfn
))
92 /* Found a free page, break it into order-0 pages */
93 isolated
= split_free_page(page
);
94 total_isolated
+= isolated
;
95 for (i
= 0; i
< isolated
; i
++) {
96 list_add(&page
->lru
, freelist
);
100 /* If a page was split, advance to the end of it */
102 blockpfn
+= isolated
- 1;
103 cursor
+= isolated
- 1;
107 trace_mm_compaction_isolate_freepages(nr_scanned
, total_isolated
);
108 return total_isolated
;
111 /* Returns true if the page is within a block suitable for migration to */
112 static bool suitable_migration_target(struct page
*page
)
115 int migratetype
= get_pageblock_migratetype(page
);
117 /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
118 if (migratetype
== MIGRATE_ISOLATE
|| migratetype
== MIGRATE_RESERVE
)
121 /* If the page is a large free page, then allow migration */
122 if (PageBuddy(page
) && page_order(page
) >= pageblock_order
)
125 /* If the block is MIGRATE_MOVABLE, allow migration */
126 if (migratetype
== MIGRATE_MOVABLE
)
129 /* Otherwise skip the block */
134 * Based on information in the current compact_control, find blocks
135 * suitable for isolating free pages from and then isolate them.
137 static void isolate_freepages(struct zone
*zone
,
138 struct compact_control
*cc
)
141 unsigned long high_pfn
, low_pfn
, pfn
;
143 int nr_freepages
= cc
->nr_freepages
;
144 struct list_head
*freelist
= &cc
->freepages
;
147 low_pfn
= cc
->migrate_pfn
+ pageblock_nr_pages
;
151 * Isolate free pages until enough are available to migrate the
152 * pages on cc->migratepages. We stop searching if the migrate
153 * and free page scanners meet or enough free pages are isolated.
155 spin_lock_irqsave(&zone
->lock
, flags
);
156 for (; pfn
> low_pfn
&& cc
->nr_migratepages
> nr_freepages
;
157 pfn
-= pageblock_nr_pages
) {
158 unsigned long isolated
;
164 * Check for overlapping nodes/zones. It's possible on some
165 * configurations to have a setup like
167 * i.e. it's possible that all pages within a zones range of
168 * pages do not belong to a single zone.
170 page
= pfn_to_page(pfn
);
171 if (page_zone(page
) != zone
)
174 /* Check the block is suitable for migration */
175 if (!suitable_migration_target(page
))
178 /* Found a block suitable for isolating free pages from */
179 isolated
= isolate_freepages_block(zone
, pfn
, freelist
);
180 nr_freepages
+= isolated
;
183 * Record the highest PFN we isolated pages from. When next
184 * looking for free pages, the search will restart here as
185 * page migration may have returned some pages to the allocator
188 high_pfn
= max(high_pfn
, pfn
);
190 spin_unlock_irqrestore(&zone
->lock
, flags
);
192 /* split_free_page does not map the pages */
193 list_for_each_entry(page
, freelist
, lru
) {
194 arch_alloc_page(page
, 0);
195 kernel_map_pages(page
, 1, 1);
198 cc
->free_pfn
= high_pfn
;
199 cc
->nr_freepages
= nr_freepages
;
202 /* Update the number of anon and file isolated pages in the zone */
203 static void acct_isolated(struct zone
*zone
, struct compact_control
*cc
)
206 unsigned int count
[NR_LRU_LISTS
] = { 0, };
208 list_for_each_entry(page
, &cc
->migratepages
, lru
) {
209 int lru
= page_lru_base_type(page
);
213 cc
->nr_anon
= count
[LRU_ACTIVE_ANON
] + count
[LRU_INACTIVE_ANON
];
214 cc
->nr_file
= count
[LRU_ACTIVE_FILE
] + count
[LRU_INACTIVE_FILE
];
215 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, cc
->nr_anon
);
216 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, cc
->nr_file
);
219 /* Similar to reclaim, but different enough that they don't share logic */
220 static bool too_many_isolated(struct zone
*zone
)
222 unsigned long active
, inactive
, isolated
;
224 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
225 zone_page_state(zone
, NR_INACTIVE_ANON
);
226 active
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
227 zone_page_state(zone
, NR_ACTIVE_ANON
);
228 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
) +
229 zone_page_state(zone
, NR_ISOLATED_ANON
);
231 return isolated
> (inactive
+ active
) / 2;
235 * Isolate all pages that can be migrated from the block pointed to by
236 * the migrate scanner within compact_control.
238 static unsigned long isolate_migratepages(struct zone
*zone
,
239 struct compact_control
*cc
)
241 unsigned long low_pfn
, end_pfn
;
242 unsigned long nr_scanned
= 0, nr_isolated
= 0;
243 struct list_head
*migratelist
= &cc
->migratepages
;
245 /* Do not scan outside zone boundaries */
246 low_pfn
= max(cc
->migrate_pfn
, zone
->zone_start_pfn
);
248 /* Only scan within a pageblock boundary */
249 end_pfn
= ALIGN(low_pfn
+ pageblock_nr_pages
, pageblock_nr_pages
);
251 /* Do not cross the free scanner or scan within a memory hole */
252 if (end_pfn
> cc
->free_pfn
|| !pfn_valid(low_pfn
)) {
253 cc
->migrate_pfn
= end_pfn
;
258 * Ensure that there are not too many pages isolated from the LRU
259 * list by either parallel reclaimers or compaction. If there are,
260 * delay for some time until fewer pages are isolated
262 while (unlikely(too_many_isolated(zone
))) {
263 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
265 if (fatal_signal_pending(current
))
269 /* Time to isolate some pages for migration */
270 spin_lock_irq(&zone
->lru_lock
);
271 for (; low_pfn
< end_pfn
; low_pfn
++) {
273 if (!pfn_valid_within(low_pfn
))
277 /* Get the page and skip if free */
278 page
= pfn_to_page(low_pfn
);
282 /* Try isolate the page */
283 if (__isolate_lru_page(page
, ISOLATE_BOTH
, 0) != 0)
286 /* Successfully isolated */
287 del_page_from_lru_list(zone
, page
, page_lru(page
));
288 list_add(&page
->lru
, migratelist
);
289 cc
->nr_migratepages
++;
292 /* Avoid isolating too much */
293 if (cc
->nr_migratepages
== COMPACT_CLUSTER_MAX
)
297 acct_isolated(zone
, cc
);
299 spin_unlock_irq(&zone
->lru_lock
);
300 cc
->migrate_pfn
= low_pfn
;
302 trace_mm_compaction_isolate_migratepages(nr_scanned
, nr_isolated
);
304 return cc
->nr_migratepages
;
308 * This is a migrate-callback that "allocates" freepages by taking pages
309 * from the isolated freelists in the block we are migrating to.
311 static struct page
*compaction_alloc(struct page
*migratepage
,
315 struct compact_control
*cc
= (struct compact_control
*)data
;
316 struct page
*freepage
;
318 /* Isolate free pages if necessary */
319 if (list_empty(&cc
->freepages
)) {
320 isolate_freepages(cc
->zone
, cc
);
322 if (list_empty(&cc
->freepages
))
326 freepage
= list_entry(cc
->freepages
.next
, struct page
, lru
);
327 list_del(&freepage
->lru
);
334 * We cannot control nr_migratepages and nr_freepages fully when migration is
335 * running as migrate_pages() has no knowledge of compact_control. When
336 * migration is complete, we count the number of pages on the lists by hand.
338 static void update_nr_listpages(struct compact_control
*cc
)
340 int nr_migratepages
= 0;
341 int nr_freepages
= 0;
344 list_for_each_entry(page
, &cc
->migratepages
, lru
)
346 list_for_each_entry(page
, &cc
->freepages
, lru
)
349 cc
->nr_migratepages
= nr_migratepages
;
350 cc
->nr_freepages
= nr_freepages
;
353 static int compact_finished(struct zone
*zone
,
354 struct compact_control
*cc
)
357 unsigned long watermark
= low_wmark_pages(zone
) + (1 << cc
->order
);
359 if (fatal_signal_pending(current
))
360 return COMPACT_PARTIAL
;
362 /* Compaction run completes if the migrate and free scanner meet */
363 if (cc
->free_pfn
<= cc
->migrate_pfn
)
364 return COMPACT_COMPLETE
;
366 /* Compaction run is not finished if the watermark is not met */
367 if (!zone_watermark_ok(zone
, cc
->order
, watermark
, 0, 0))
368 return COMPACT_CONTINUE
;
371 return COMPACT_CONTINUE
;
373 /* Direct compactor: Is a suitable page free? */
374 for (order
= cc
->order
; order
< MAX_ORDER
; order
++) {
375 /* Job done if page is free of the right migratetype */
376 if (!list_empty(&zone
->free_area
[order
].free_list
[cc
->migratetype
]))
377 return COMPACT_PARTIAL
;
379 /* Job done if allocation would set block type */
380 if (order
>= pageblock_order
&& zone
->free_area
[order
].nr_free
)
381 return COMPACT_PARTIAL
;
384 return COMPACT_CONTINUE
;
388 * compaction_suitable: Is this suitable to run compaction on this zone now?
390 * COMPACT_SKIPPED - If there are too few free pages for compaction
391 * COMPACT_PARTIAL - If the allocation would succeed without compaction
392 * COMPACT_CONTINUE - If compaction should run now
394 unsigned long compaction_suitable(struct zone
*zone
, int order
)
397 unsigned long watermark
;
400 * Watermarks for order-0 must be met for compaction. Note the 2UL.
401 * This is because during migration, copies of pages need to be
402 * allocated and for a short time, the footprint is higher
404 watermark
= low_wmark_pages(zone
) + (2UL << order
);
405 if (!zone_watermark_ok(zone
, 0, watermark
, 0, 0))
406 return COMPACT_SKIPPED
;
409 * fragmentation index determines if allocation failures are due to
410 * low memory or external fragmentation
412 * index of -1 implies allocations might succeed dependingon watermarks
413 * index towards 0 implies failure is due to lack of memory
414 * index towards 1000 implies failure is due to fragmentation
416 * Only compact if a failure would be due to fragmentation.
418 fragindex
= fragmentation_index(zone
, order
);
419 if (fragindex
>= 0 && fragindex
<= sysctl_extfrag_threshold
)
420 return COMPACT_SKIPPED
;
422 if (fragindex
== -1 && zone_watermark_ok(zone
, order
, watermark
, 0, 0))
423 return COMPACT_PARTIAL
;
425 return COMPACT_CONTINUE
;
428 static int compact_zone(struct zone
*zone
, struct compact_control
*cc
)
432 ret
= compaction_suitable(zone
, cc
->order
);
434 case COMPACT_PARTIAL
:
435 case COMPACT_SKIPPED
:
436 /* Compaction is likely to fail */
438 case COMPACT_CONTINUE
:
439 /* Fall through to compaction */
443 /* Setup to move all movable pages to the end of the zone */
444 cc
->migrate_pfn
= zone
->zone_start_pfn
;
445 cc
->free_pfn
= cc
->migrate_pfn
+ zone
->spanned_pages
;
446 cc
->free_pfn
&= ~(pageblock_nr_pages
-1);
448 migrate_prep_local();
450 while ((ret
= compact_finished(zone
, cc
)) == COMPACT_CONTINUE
) {
451 unsigned long nr_migrate
, nr_remaining
;
453 if (!isolate_migratepages(zone
, cc
))
456 nr_migrate
= cc
->nr_migratepages
;
457 migrate_pages(&cc
->migratepages
, compaction_alloc
,
458 (unsigned long)cc
, 0);
459 update_nr_listpages(cc
);
460 nr_remaining
= cc
->nr_migratepages
;
462 count_vm_event(COMPACTBLOCKS
);
463 count_vm_events(COMPACTPAGES
, nr_migrate
- nr_remaining
);
465 count_vm_events(COMPACTPAGEFAILED
, nr_remaining
);
466 trace_mm_compaction_migratepages(nr_migrate
- nr_remaining
,
469 /* Release LRU pages not migrated */
470 if (!list_empty(&cc
->migratepages
)) {
471 putback_lru_pages(&cc
->migratepages
);
472 cc
->nr_migratepages
= 0;
477 /* Release free pages and check accounting */
478 cc
->nr_freepages
-= release_freepages(&cc
->freepages
);
479 VM_BUG_ON(cc
->nr_freepages
!= 0);
484 unsigned long compact_zone_order(struct zone
*zone
,
485 int order
, gfp_t gfp_mask
)
487 struct compact_control cc
= {
489 .nr_migratepages
= 0,
491 .migratetype
= allocflags_to_migratetype(gfp_mask
),
494 INIT_LIST_HEAD(&cc
.freepages
);
495 INIT_LIST_HEAD(&cc
.migratepages
);
497 return compact_zone(zone
, &cc
);
500 int sysctl_extfrag_threshold
= 500;
503 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
504 * @zonelist: The zonelist used for the current allocation
505 * @order: The order of the current allocation
506 * @gfp_mask: The GFP mask of the current allocation
507 * @nodemask: The allowed nodes to allocate from
509 * This is the main entry point for direct page compaction.
511 unsigned long try_to_compact_pages(struct zonelist
*zonelist
,
512 int order
, gfp_t gfp_mask
, nodemask_t
*nodemask
)
514 enum zone_type high_zoneidx
= gfp_zone(gfp_mask
);
515 int may_enter_fs
= gfp_mask
& __GFP_FS
;
516 int may_perform_io
= gfp_mask
& __GFP_IO
;
519 int rc
= COMPACT_SKIPPED
;
522 * Check whether it is worth even starting compaction. The order check is
523 * made because an assumption is made that the page allocator can satisfy
524 * the "cheaper" orders without taking special steps
526 if (order
<= PAGE_ALLOC_COSTLY_ORDER
|| !may_enter_fs
|| !may_perform_io
)
529 count_vm_event(COMPACTSTALL
);
531 /* Compact each zone in the list */
532 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
, high_zoneidx
,
536 status
= compact_zone_order(zone
, order
, gfp_mask
);
537 rc
= max(status
, rc
);
539 /* If a normal allocation would succeed, stop compacting */
540 if (zone_watermark_ok(zone
, order
, low_wmark_pages(zone
), 0, 0))
548 /* Compact all zones within a node */
549 static int compact_node(int nid
)
555 if (nid
< 0 || nid
>= nr_node_ids
|| !node_online(nid
))
557 pgdat
= NODE_DATA(nid
);
559 /* Flush pending updates to the LRU lists */
562 for (zoneid
= 0; zoneid
< MAX_NR_ZONES
; zoneid
++) {
563 struct compact_control cc
= {
565 .nr_migratepages
= 0,
569 zone
= &pgdat
->node_zones
[zoneid
];
570 if (!populated_zone(zone
))
574 INIT_LIST_HEAD(&cc
.freepages
);
575 INIT_LIST_HEAD(&cc
.migratepages
);
577 compact_zone(zone
, &cc
);
579 VM_BUG_ON(!list_empty(&cc
.freepages
));
580 VM_BUG_ON(!list_empty(&cc
.migratepages
));
586 /* Compact all nodes in the system */
587 static int compact_nodes(void)
591 for_each_online_node(nid
)
594 return COMPACT_COMPLETE
;
597 /* The written value is actually unused, all memory is compacted */
598 int sysctl_compact_memory
;
600 /* This is the entry point for compacting all nodes via /proc/sys/vm */
601 int sysctl_compaction_handler(struct ctl_table
*table
, int write
,
602 void __user
*buffer
, size_t *length
, loff_t
*ppos
)
605 return compact_nodes();
610 int sysctl_extfrag_handler(struct ctl_table
*table
, int write
,
611 void __user
*buffer
, size_t *length
, loff_t
*ppos
)
613 proc_dointvec_minmax(table
, write
, buffer
, length
, ppos
);
618 #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
619 ssize_t
sysfs_compact_node(struct sys_device
*dev
,
620 struct sysdev_attribute
*attr
,
621 const char *buf
, size_t count
)
623 compact_node(dev
->id
);
627 static SYSDEV_ATTR(compact
, S_IWUSR
, NULL
, sysfs_compact_node
);
629 int compaction_register_node(struct node
*node
)
631 return sysdev_create_file(&node
->sysdev
, &attr_compact
);
634 void compaction_unregister_node(struct node
*node
)
636 return sysdev_remove_file(&node
->sysdev
, &attr_compact
);
638 #endif /* CONFIG_SYSFS && CONFIG_NUMA */