On Mon, 28 Jul 2014, Vlastimil Babka wrote:
> The compact_stall vmstat counter counts the number of allocations stalled by
> direct compaction. It does not count when all attempted zones had deferred
> compaction, but it does count when all zones skipped compaction. The skipping
> is decided based on very early check of compaction_suitable(), based on
> watermarks and memory fragmentation. Therefore it makes sense not to count
> skipped compactions as stalls. Moreover, compact_success or compact_fail is
> also already not being counted when compaction was skipped, so this patch
> changes the compact_stall counting to match the other two.
>
> Additionally, restructure __alloc_pages_direct_compact() code for better
> readability.
>
> Signed-off-by: Vlastimil Babka <vba...@suse.cz>
> Cc: Minchan Kim <minc...@kernel.org>
> Acked-by: Mel Gorman <mgor...@suse.de>
> Cc: Joonsoo Kim <iamjoonsoo....@lge.com>
> Cc: Michal Nazarewicz <min...@mina86.com>
> Cc: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
> Cc: Christoph Lameter <c...@linux.com>
> Cc: Rik van Riel <r...@redhat.com>
> Cc: David Rientjes <rient...@google.com>
Acked-by: David Rientjes <rient...@google.com>
This makes the second patch in the series more understandable but I still
renew my suggestion that you should be doing the following as part of the
second patch.
---
diff --git a/mm/compaction.c b/mm/compaction.c
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1136,7 +1136,7 @@ unsigned long try_to_compact_pages(struct zonelist
*zonelist,
int may_perform_io = gfp_mask & __GFP_IO;
struct zoneref *z;
struct zone *zone;
- int rc = COMPACT_DEFERRED;
+ int rc = COMPACT_SKIPPED;
int alloc_flags = 0;
/* Check if the GFP flags allow compaction */
@@ -1147,6 +1147,7 @@ unsigned long try_to_compact_pages(struct zonelist
*zonelist,
if (allocflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
alloc_flags |= ALLOC_CMA;
#endif
+ rc = COMPACT_DEFERRED;
/* Compact each zone in the list */
for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
nodemask) {
--
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