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| author | Mel Gorman <mel@csn.ul.ie> | 2010-05-24 14:32:32 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-25 08:07:00 -0700 |
| commit | 4f92e2586b43a2402e116055d4edda704f911b5b (patch) | |
| tree | 6a765ebeba951c02a7878bcea52a4769ad2e45c2 /mm | |
| parent | 5e7719058079a1423ccce56148b0aaa56b2df821 (diff) | |
| download | lwn-4f92e2586b43a2402e116055d4edda704f911b5b.tar.gz lwn-4f92e2586b43a2402e116055d4edda704f911b5b.zip | |
mm: compaction: defer compaction using an exponential backoff when compaction fails
The fragmentation index may indicate that a failure is due to external
fragmentation but after a compaction run completes, it is still possible
for an allocation to fail. There are two obvious reasons as to why
o Page migration cannot move all pages so fragmentation remains
o A suitable page may exist but watermarks are not met
In the event of compaction followed by an allocation failure, this patch
defers further compaction in the zone (1 << compact_defer_shift) times.
If the next compaction attempt also fails, compact_defer_shift is
increased up to a maximum of 6. If compaction succeeds, the defer
counters are reset again.
The zone that is deferred is the first zone in the zonelist - i.e. the
preferred zone. To defer compaction in the other zones, the information
would need to be stored in the zonelist or implemented similar to the
zonelist_cache. This would impact the fast-paths and is not justified at
this time.
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/page_alloc.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index cd88a860f088..95ad42de5a87 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1769,7 +1769,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, { struct page *page; - if (!order) + if (!order || compaction_deferred(preferred_zone)) return NULL; *did_some_progress = try_to_compact_pages(zonelist, order, gfp_mask, @@ -1785,6 +1785,8 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, alloc_flags, preferred_zone, migratetype); if (page) { + preferred_zone->compact_considered = 0; + preferred_zone->compact_defer_shift = 0; count_vm_event(COMPACTSUCCESS); return page; } @@ -1795,6 +1797,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, * but not enough to satisfy watermarks. */ count_vm_event(COMPACTFAIL); + defer_compaction(preferred_zone); cond_resched(); } |