---

yaml
---
r: 284405
b: refs/heads/master
c: fe4b1b2
h: refs/heads/master
i:
  284403: bb20990
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a6bc32b899223a877f595ef9ddc1e89ead5072b8
+refs/heads/master: fe4b1b244bdb96136855f2c694071cb09d140766

trunk/mm/vmscan.c

@@ -2163,6 +2163,42 @@ static void shrink_zone(int priority, struct zone *zone,
 	} while (memcg);
 }
 
+/* Returns true if compaction should go ahead for a high-order request */
+static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
+{
+	unsigned long balance_gap, watermark;
+	bool watermark_ok;
+
+	/* Do not consider compaction for orders reclaim is meant to satisfy */
+	if (sc->order <= PAGE_ALLOC_COSTLY_ORDER)
+		return false;
+
+	/*
+	 * Compaction takes time to run and there are potentially other
+	 * callers using the pages just freed. Continue reclaiming until
+	 * there is a buffer of free pages available to give compaction
+	 * a reasonable chance of completing and allocating the page
+	 */
+	balance_gap = min(low_wmark_pages(zone),
+		(zone->present_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
+			KSWAPD_ZONE_BALANCE_GAP_RATIO);
+	watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order);
+	watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
+
+	/*
+	 * If compaction is deferred, reclaim up to a point where
+	 * compaction will have a chance of success when re-enabled
+	 */
+	if (compaction_deferred(zone))
+		return watermark_ok;
+
+	/* If compaction is not ready to start, keep reclaiming */
+	if (!compaction_suitable(zone, sc->order))
+		return false;
+
+	return watermark_ok;
+}
+
 /*
  * This is the direct reclaim path, for page-allocating processes.  We only
  * try to reclaim pages from zones which will satisfy the caller's allocation
@@ -2180,8 +2216,8 @@ static void shrink_zone(int priority, struct zone *zone,
  * scan then give up on it.
  *
  * This function returns true if a zone is being reclaimed for a costly
- * high-order allocation and compaction is either ready to begin or deferred.
- * This indicates to the caller that it should retry the allocation or fail.
+ * high-order allocation and compaction is ready to begin. This indicates to
+ * the caller that it should retry the allocation or fail.
  */
 static bool shrink_zones(int priority, struct zonelist *zonelist,
 					struct scan_control *sc)
@@ -2215,9 +2251,7 @@ static bool shrink_zones(int priority, struct zonelist *zonelist,
 				 * noticable problem, like transparent huge page
 				 * allocations.
 				 */
-				if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&
-					(compaction_suitable(zone, sc->order) ||
-					 compaction_deferred(zone))) {
+				if (compaction_ready(zone, sc)) {
 					should_abort_reclaim = true;
 					continue;
 				}