mm: compaction: direct compact when a high-order allocation fails
authorMel Gorman <mel@csn.ul.ie>
Mon, 24 May 2010 21:32:30 +0000 (14:32 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 25 May 2010 15:06:59 +0000 (08:06 -0700)
commit56de7263fcf3eb10c8dcdf8d59a9cec831795f3f
tree164637c0b678e20adfdcec4129563d9234faf405
parented4a6d7f0676db50b5023cc01f6cda82a2f2a307
mm: compaction: direct compact when a high-order allocation fails

Ordinarily when a high-order allocation fails, direct reclaim is entered
to free pages to satisfy the allocation.  With this patch, it is
determined if an allocation failed due to external fragmentation instead
of low memory and if so, the calling process will compact until a suitable
page is freed.  Compaction by moving pages in memory is considerably
cheaper than paging out to disk and works where there are locked pages or
no swap.  If compaction fails to free a page of a suitable size, then
reclaim will still occur.

Direct compaction returns as soon as possible.  As each block is
compacted, it is checked if a suitable page has been freed and if so, it
returns.

[akpm@linux-foundation.org: Fix build errors]
[aarcange@redhat.com: fix count_vm_event preempt in memory compaction direct reclaim]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: 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: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/compaction.h
include/linux/vmstat.h
mm/compaction.c
mm/page_alloc.c
mm/vmstat.c