3 files changed, 43 insertions, 16 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index f94cbc0b99a5..d8187f9cabbf 100644
--- a/mm/compaction.c
+++ b/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();
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 44c56049edf9..b97cf12f07a9 100644
--- a/mm/page_alloc.c
+++ b/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)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1ee4b69a28a5..b010efc43891 100644
--- a/mm/vmscan.c
+++ b/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();