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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: Michal Hocko <mhocko@kernel.org>
Link: http://lkml.kernel.org/r/20160906135258.18335-4-vbabka@suse.cz
Signed-off-by: Vlastimil 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vlastimil Babka 2016-10-07 17:00:34 -07:00 committed by Linus Torvalds
parent d943649831
commit c2033b00db
2 changed files with 5 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/compaction.h
View File

@ -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

5
mm/page_alloc.c
View File

@ -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;