vmscan: only defer compaction for failed order and higher

Currently a failed order-9 (transparent hugepage) compaction can lead to
memory compaction being temporarily disabled for a memory zone.  Even if
we only need compaction for an order 2 allocation, eg.  for jumbo frames
networking.

The fix is relatively straightforward: keep track of the highest order at
which compaction is succeeding, and only defer compaction for orders at
which compaction is failing.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 11 insertions, 4 deletions

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 7a9323aef4a3..51a90b7f2d60 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -34,20 +34,26 @@ extern unsigned long compaction_suitable(struct zone *zone, int order);
  * allocation success. 1 << compact_defer_limit compactions are skipped up
  * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
  */
-static inline void defer_compaction(struct zone *zone)
+static inline void defer_compaction(struct zone *zone, int order)
 {
         zone->compact_considered = 0;
         zone->compact_defer_shift++;
 
+        if (order < zone->compact_order_failed)
+                zone->compact_order_failed = order;
+
         if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
                 zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
 }
 
 /* Returns true if compaction should be skipped this time */
-static inline bool compaction_deferred(struct zone *zone)
+static inline bool compaction_deferred(struct zone *zone, int order)
 {
         unsigned long defer_limit = 1UL << zone->compact_defer_shift;
 
+        if (order < zone->compact_order_failed)
+                return false;
+
         /* Avoid possible overflow */
         if (++zone->compact_considered > defer_limit)
                 zone->compact_considered = defer_limit;
@@ -73,11 +79,11 @@ static inline unsigned long compaction_suitable(struct zone *zone, int order)
         return COMPACT_SKIPPED;
 }
 
-static inline void defer_compaction(struct zone *zone)
+static inline void defer_compaction(struct zone *zone, int order)
 {
 }
 
-static inline bool compaction_deferred(struct zone *zone)
+static inline bool compaction_deferred(struct zone *zone, int order)
 {
         return 1;
 }
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 650ba2fb3301..dff711509661 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -365,6 +365,7 @@ struct zone {
          */
         unsigned int            compact_considered;
         unsigned int            compact_defer_shift;
+        int                     compact_order_failed;
 #endif
 
         ZONE_PADDING(_pad1_)