On 09/26/2016 06:20 PM, Vlastimil Babka wrote:
> The compaction_zonelist_suitable() function tries to determine if compaction
> will be able to proceed after sufficient reclaim, i.e. whether there are
> enough reclaimable pages to provide enough order-0 freepages for compaction.
>
> This addition of reclaimable pages to the free pages works well for the
> order-0
> watermark check, but in the fragmentation index check we only consider truly
> free pages. Thus we can get fragindex value close to 0 which indicates failure
> do to lack of memory, and wrongly decide that compaction won't be suitable
> even
> after reclaim.
>
> Instead of trying to somehow adjust fragindex for reclaimable pages, let's
> just
> skip it from compaction_zonelist_suitable().
>
> Signed-off-by: Vlastimil Babka <vba...@suse.cz>
> Cc: Michal Hocko <mho...@kernel.org>
> Cc: Mel Gorman <mgor...@techsingularity.net>
> Cc: Joonsoo Kim <iamjoonsoo....@lge.com>
> Cc: David Rientjes <rient...@google.com>
> Cc: Rik van Riel <r...@redhat.com>
Bah, a fix below, sorry.
----8<----
>From 1cd4855305a9c7eef0cf0c1af9f310cecdcc9406 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vba...@suse.cz>
Date: Thu, 29 Sep 2016 11:54:07 +0200
Subject: [PATCH] mm, compaction: ignore fragindex from
compaction_zonelist_suitable()-fix
COMPACT_NOT_SUITABLE_ZONE should not leak outside compaction_suitable() and
we should not skip tracepoint.
Signed-off-by: Vlastimil Babka <vba...@suse.cz>
---
mm/compaction.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index badb92bf14b4..0409a4ad6ea1 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1445,7 +1445,7 @@ enum compact_result compaction_suitable(struct zone
*zone, int order,
if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
fragindex = fragmentation_index(zone, order);
if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
- return COMPACT_NOT_SUITABLE_ZONE;
+ ret = COMPACT_NOT_SUITABLE_ZONE;
}
trace_mm_compaction_suitable(zone, order, ret);
--
2.10.0
