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Commit c2033b00 authored by Vlastimil Babka's avatar Vlastimil Babka Committed by Linus Torvalds
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mm, compaction: restrict full priority to non-costly orders 



The new ultimate compaction priority disables some heuristics, which may
result in excessive cost.  This is fine for non-costly orders where we
want to try hard before resulting for OOM, but might be disruptive for
costly orders which do not trigger OOM and should generally have some
fallback.  Thus, we disable the full priority for costly orders.

Suggested-by: default avatarMichal Hocko <mhocko@kernel.org>
Link: http://lkml.kernel.org/r/20160906135258.18335-4-vbabka@suse.cz


Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d9436498

include/linux/compaction.h

+1 −0
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ enum compact_priority { 
	COMPACT_PRIO_SYNC_FULL,

	MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_FULL,

	COMPACT_PRIO_SYNC_LIGHT,

	MIN_COMPACT_COSTLY_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,

	DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,

	COMPACT_PRIO_ASYNC,

	INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC

mm/page_alloc.c

+4 −1
Original line number Diff line number Diff line
@@ -3163,6 +3163,7 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, 
		     int *compaction_retries)

{

	int max_retries = MAX_COMPACT_RETRIES;

	int min_priority;



	if (!order)

		return false;
@@ -3205,7 +3206,9 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, 
	 * all retries or failed at the lower priorities.

	 */

check_priority:

	if (*compact_priority > MIN_COMPACT_PRIORITY) {

	min_priority = (order > PAGE_ALLOC_COSTLY_ORDER) ?

			MIN_COMPACT_COSTLY_PRIORITY : MIN_COMPACT_PRIORITY;

	if (*compact_priority > min_priority) {

		(*compact_priority)--;

		*compaction_retries = 0;

		return true;