---

yaml
---
r: 332441
b: refs/heads/master
c: 6299702
h: refs/heads/master
i:
  332439: 2625201
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c89511ab2f8fe2b47585e60da8af7fd213ec877e
+refs/heads/master: 62997027ca5b3d4618198ed8b1aba40b61b1137b

trunk/include/linux/compaction.h

@@ -24,6 +24,7 @@ extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
 			int order, gfp_t gfp_mask, nodemask_t *mask,
 			bool sync, bool *contended, struct page **page);
 extern int compact_pgdat(pg_data_t *pgdat, int order);
+extern void reset_isolation_suitable(pg_data_t *pgdat);
 extern unsigned long compaction_suitable(struct zone *zone, int order);
 
 /* Do not skip compaction more than 64 times */
@@ -61,6 +62,16 @@ static inline bool compaction_deferred(struct zone *zone, int order)
 	return zone->compact_considered < defer_limit;
 }
 
+/* Returns true if restarting compaction after many failures */
+static inline bool compaction_restarting(struct zone *zone, int order)
+{
+	if (order < zone->compact_order_failed)
+		return false;
+
+	return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
+		zone->compact_considered >= 1UL << zone->compact_defer_shift;
+}
+
 #else
 static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
 			int order, gfp_t gfp_mask, nodemask_t *nodemask,
@@ -74,6 +85,10 @@ static inline int compact_pgdat(pg_data_t *pgdat, int order)
 	return COMPACT_CONTINUE;
 }
 
+static inline void reset_isolation_suitable(pg_data_t *pgdat)
+{
+}
+
 static inline unsigned long compaction_suitable(struct zone *zone, int order)
 {
 	return COMPACT_SKIPPED;

trunk/include/linux/mmzone.h

@@ -370,7 +370,8 @@ struct zone {
 	spinlock_t		lock;
 	int                     all_unreclaimable; /* All pages pinned */
 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
-	unsigned long		compact_blockskip_expire;
+	/* Set to true when the PG_migrate_skip bits should be cleared */
+	bool			compact_blockskip_flush;
 
 	/* pfns where compaction scanners should start */
 	unsigned long		compact_cached_free_pfn;

trunk/mm/compaction.c

@@ -66,24 +66,15 @@ static inline bool isolation_suitable(struct compact_control *cc,
  * should be skipped for page isolation when the migrate and free page scanner
  * meet.
  */
-static void reset_isolation_suitable(struct zone *zone)
+static void __reset_isolation_suitable(struct zone *zone)
 {
 	unsigned long start_pfn = zone->zone_start_pfn;
 	unsigned long end_pfn = zone->zone_start_pfn + zone->spanned_pages;
 	unsigned long pfn;
 
-	/*
-	 * Do not reset more than once every five seconds. If allocations are
-	 * failing sufficiently quickly to allow this to happen then continually
-	 * scanning for compaction is not going to help. The choice of five
-	 * seconds is arbitrary but will mitigate excessive scanning.
-	 */
-	if (time_before(jiffies, zone->compact_blockskip_expire))
-		return;
-
 	zone->compact_cached_migrate_pfn = start_pfn;
 	zone->compact_cached_free_pfn = end_pfn;
-	zone->compact_blockskip_expire = jiffies + (HZ * 5);
+	zone->compact_blockskip_flush = false;
 
 	/* Walk the zone and mark every pageblock as suitable for isolation */
 	for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
@@ -102,9 +93,24 @@ static void reset_isolation_suitable(struct zone *zone)
 	}
 }
 
+void reset_isolation_suitable(pg_data_t *pgdat)
+{
+	int zoneid;
+
+	for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
+		struct zone *zone = &pgdat->node_zones[zoneid];
+		if (!populated_zone(zone))
+			continue;
+
+		/* Only flush if a full compaction finished recently */
+		if (zone->compact_blockskip_flush)
+			__reset_isolation_suitable(zone);
+	}
+}
+
 /*
  * If no pages were isolated then mark this pageblock to be skipped in the
- * future. The information is later cleared by reset_isolation_suitable().
+ * future. The information is later cleared by __reset_isolation_suitable().
  */
 static void update_pageblock_skip(struct compact_control *cc,
 			struct page *page, unsigned long nr_isolated,
@@ -820,7 +826,15 @@ static int compact_finished(struct zone *zone,
 
 	/* Compaction run completes if the migrate and free scanner meet */
 	if (cc->free_pfn <= cc->migrate_pfn) {
-		reset_isolation_suitable(cc->zone);
+		/*
+		 * Mark that the PG_migrate_skip information should be cleared
+		 * by kswapd when it goes to sleep. kswapd does not set the
+		 * flag itself as the decision to be clear should be directly
+		 * based on an allocation request.
+		 */
+		if (!current_is_kswapd())
+			zone->compact_blockskip_flush = true;
+
 		return COMPACT_COMPLETE;
 	}
 
@@ -943,9 +957,13 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
 		zone->compact_cached_migrate_pfn = cc->migrate_pfn;
 	}
 
-	/* Clear pageblock skip if there are numerous alloc failures */
-	if (zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT)
-		reset_isolation_suitable(zone);
+	/*
+	 * Clear pageblock skip if there were failures recently and compaction
+	 * is about to be retried after being deferred. kswapd does not do
+	 * this reset as it'll reset the cached information when going to sleep.
+	 */
+	if (compaction_restarting(zone, cc->order) && !current_is_kswapd())
+		__reset_isolation_suitable(zone);
 
 	migrate_prep_local();
 

trunk/mm/page_alloc.c

@@ -2172,6 +2172,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
 				preferred_zone, migratetype);
 		if (page) {
 got_page:
+			preferred_zone->compact_blockskip_flush = false;
 			preferred_zone->compact_considered = 0;
 			preferred_zone->compact_defer_shift = 0;
 			if (order >= preferred_zone->compact_order_failed)

trunk/mm/vmscan.c

@@ -2895,6 +2895,14 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
 		 */
 		set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
 
+		/*
+		 * Compaction records what page blocks it recently failed to
+		 * isolate pages from and skips them in the future scanning.
+		 * When kswapd is going to sleep, it is reasonable to assume
+		 * that pages and compaction may succeed so reset the cache.
+		 */
+		reset_isolation_suitable(pgdat);
+
 		if (!kthread_should_stop())
 			schedule();