[PATCH V2 2/2] mm/vmscan: not check compaction_ready on promoted zones

[Weijie Yang]

We abort direct reclaim if find the zone is ready for compaction.
Sometimes the zone is just a promoted highmem zone to force scan
pinning highmem, which is not the intended zone the caller want to
alloc page from. In this situation, setting aborted_reclaim to
indicate the caller turn back to retry allocation is waste of time
and could cause a loop in __alloc_pages_slowpath().

This patch do not check compaction_ready() on promoted zones to avoid
the above situation, only set aborted_reclaim if the caller intended
zone is ready to compaction.

Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Weijie Yang <weijie.yang@xxxxxxxxxxx>
---
 mm/vmscan.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index da0a87c..9ec6519 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2299,6 +2299,7 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
 	unsigned long nr_soft_scanned;
 	bool aborted_reclaim = false;
 	gfp_t orig_mask = sc->gfp_mask;
+	enum zone_type requested_highidx = gfp_zone(sc->gfp_mask);
 
 	/*
 	 * If the number of buffer_heads in the machine exceeds the maximum
@@ -2332,7 +2333,8 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
 				 * noticeable problem, like transparent huge
 				 * page allocations.
 				 */
-				if (compaction_ready(zone, sc)) {
+				if ((zonelist_zone_idx(z) <= requested_highidx)
+				    && compaction_ready(zone, sc)) {
 					aborted_reclaim = true;
 					continue;
 				}
-- 
1.7.10.4


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