1 files changed, 117 insertions, 0 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index f61f77983ff4..9583e193dc47 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -35,6 +35,8 @@ struct compact_control {
         unsigned long nr_anon;
         unsigned long nr_file;
 
+        unsigned int order;             /* order a direct compactor needs */
+        int migratetype;                /* MOVABLE, RECLAIMABLE etc */
         struct zone *zone;
 };
 
@@ -341,6 +343,9 @@ static void update_nr_listpages(struct compact_control *cc)
 static int compact_finished(struct zone *zone,
                                                 struct compact_control *cc)
 {
+        unsigned int order;
+        unsigned long watermark = low_wmark_pages(zone) + (1 << cc->order);
+
         if (fatal_signal_pending(current))
                 return COMPACT_PARTIAL;
 
@@ -348,6 +353,24 @@ static int compact_finished(struct zone *zone,
         if (cc->free_pfn <= cc->migrate_pfn)
                 return COMPACT_COMPLETE;
 
+        /* Compaction run is not finished if the watermark is not met */
+        if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
+                return COMPACT_CONTINUE;
+
+        if (cc->order == -1)
+                return COMPACT_CONTINUE;
+
+        /* Direct compactor: Is a suitable page free? */
+        for (order = cc->order; order < MAX_ORDER; order++) {
+                /* Job done if page is free of the right migratetype */
+                if (!list_empty(&zone->free_area[order].free_list[cc->migratetype]))
+                        return COMPACT_PARTIAL;
+
+                /* Job done if allocation would set block type */
+                if (order >= pageblock_order && zone->free_area[order].nr_free)
+                        return COMPACT_PARTIAL;
+        }
+
         return COMPACT_CONTINUE;
 }
 
@@ -394,6 +417,99 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
         return ret;
 }
 
+static unsigned long compact_zone_order(struct zone *zone,
+                                                int order, gfp_t gfp_mask)
+{
+        struct compact_control cc = {
+                .nr_freepages = 0,
+                .nr_migratepages = 0,
+                .order = order,
+                .migratetype = allocflags_to_migratetype(gfp_mask),
+                .zone = zone,
+        };
+        INIT_LIST_HEAD(&cc.freepages);
+        INIT_LIST_HEAD(&cc.migratepages);
+
+        return compact_zone(zone, &cc);
+}
+
+/**
+ * try_to_compact_pages - Direct compact to satisfy a high-order allocation
+ * @zonelist: The zonelist used for the current allocation
+ * @order: The order of the current allocation
+ * @gfp_mask: The GFP mask of the current allocation
+ * @nodemask: The allowed nodes to allocate from
+ *
+ * This is the main entry point for direct page compaction.
+ */
+unsigned long try_to_compact_pages(struct zonelist *zonelist,
+                        int order, gfp_t gfp_mask, nodemask_t *nodemask)
+{
+        enum zone_type high_zoneidx = gfp_zone(gfp_mask);
+        int may_enter_fs = gfp_mask & __GFP_FS;
+        int may_perform_io = gfp_mask & __GFP_IO;
+        unsigned long watermark;
+        struct zoneref *z;
+        struct zone *zone;
+        int rc = COMPACT_SKIPPED;
+
+        /*
+         * Check whether it is worth even starting compaction. The order check is
+         * made because an assumption is made that the page allocator can satisfy
+         * the "cheaper" orders without taking special steps
+         */
+        if (order <= PAGE_ALLOC_COSTLY_ORDER || !may_enter_fs || !may_perform_io)
+                return rc;
+
+        count_vm_event(COMPACTSTALL);
+
+        /* Compact each zone in the list */
+        for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
+                                                                nodemask) {
+                int fragindex;
+                int status;
+
+                /*
+                 * Watermarks for order-0 must be met for compaction. Note
+                 * the 2UL. This is because during migration, copies of
+                 * pages need to be allocated and for a short time, the
+                 * footprint is higher
+                 */
+                watermark = low_wmark_pages(zone) + (2UL << order);
+                if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
+                        continue;
+
+                /*
+                 * fragmentation index determines if allocation failures are
+                 * due to low memory or external fragmentation
+                 *
+                 * index of -1 implies allocations might succeed depending
+                 *      on watermarks
+                 * index towards 0 implies failure is due to lack of memory
+                 * index towards 1000 implies failure is due to fragmentation
+                 *
+                 * Only compact if a failure would be due to fragmentation.
+                 */
+                fragindex = fragmentation_index(zone, order);
+                if (fragindex >= 0 && fragindex <= 500)
+                        continue;
+
+                if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0)) {
+                        rc = COMPACT_PARTIAL;
+                        break;
+                }
+
+                status = compact_zone_order(zone, order, gfp_mask);
+                rc = max(status, rc);
+
+                if (zone_watermark_ok(zone, order, watermark, 0, 0))
+                        break;
+        }
+
+        return rc;
+}
+
+
 /* Compact all zones within a node */
 static int compact_node(int nid)
 {
@@ -412,6 +528,7 @@ static int compact_node(int nid)
                 struct compact_control cc = {
                         .nr_freepages = 0,
                         .nr_migratepages = 0,
+                        .order = -1,
                 };
 
                 zone = &pgdat->node_zones[zoneid];