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compaction: checks correct fragmentation index 

fragmentation_index() returns -1000 when the allocation might succeed
This doesn't match the comment and code in compaction_suitable(). I
thought compaction_suitable should return COMPACT_PARTIAL in -1000
case, because in this case allocation could succeed depending on
watermarks.

The impact of this is that compaction starts and compact_finished() is
called which rechecks the watermarks and the free lists.  It should have
the same result in that compaction should not start but is more expensive.

Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Shaohua Li 2011-06-15 15:08:49 -07:00 committed by Linus Torvalds
parent 5db8a73a8d
commit a582a738c7
1 changed files with 4 additions and 2 deletions
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6
mm/compaction.c
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@ -480,7 +480,8 @@ unsigned long compaction_suitable(struct zone *zone, int order)
* fragmentation index determines if allocation failures are due to
* low memory or external fragmentation
*
* index of -1 implies allocations might succeed dependingon watermarks
* index of -1000 implies allocations might succeed depending on
* watermarks
* index towards 0 implies failure is due to lack of memory
* index towards 1000 implies failure is due to fragmentation
*
@ -490,7 +491,8 @@ unsigned long compaction_suitable(struct zone *zone, int order)
if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
return COMPACT_SKIPPED;
if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0))
if (fragindex == -1000 && zone_watermark_ok(zone, order, watermark,
0, 0))
return COMPACT_PARTIAL;
return COMPACT_CONTINUE;