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author | Mel Gorman <mel@csn.ul.ie> | 2010-05-24 14:32:32 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-25 08:07:00 -0700 |
commit | 4f92e2586b43a2402e116055d4edda704f911b5b (patch) | |
tree | 6a765ebeba951c02a7878bcea52a4769ad2e45c2 /mm/mempolicy.c | |
parent | 5e7719058079a1423ccce56148b0aaa56b2df821 (diff) | |
download | op-kernel-dev-4f92e2586b43a2402e116055d4edda704f911b5b.zip op-kernel-dev-4f92e2586b43a2402e116055d4edda704f911b5b.tar.gz |
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/mempolicy.c')
0 files changed, 0 insertions, 0 deletions