thp: use compaction in kswapd for GFP_ATOMIC order > 0

This takes advantage of memory compaction to properly generate pages of
order > 0 if regular page reclaim fails and priority level becomes more
severe and we don't reach the proper watermarks.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 26 insertions, 5 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index da25b5a2e476..60d52a7298d5 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -42,6 +42,8 @@ struct compact_control {
         unsigned int order;             /* order a direct compactor needs */
         int migratetype;                /* MOVABLE, RECLAIMABLE etc */
         struct zone *zone;
+
+        int compact_mode;
 };
 
 static unsigned long release_freepages(struct list_head *freelist)
@@ -382,10 +384,10 @@ static void update_nr_listpages(struct compact_control *cc)
 }
 
 static int compact_finished(struct zone *zone,
-                                                struct compact_control *cc)
+                            struct compact_control *cc)
 {
         unsigned int order;
-        unsigned long watermark = low_wmark_pages(zone) + (1 << cc->order);
+        unsigned long watermark;
 
         if (fatal_signal_pending(current))
                 return COMPACT_PARTIAL;
@@ -395,12 +397,27 @@ static int compact_finished(struct zone *zone,
                 return COMPACT_COMPLETE;
 
         /* Compaction run is not finished if the watermark is not met */
+        if (cc->compact_mode != COMPACT_MODE_KSWAPD)
+                watermark = low_wmark_pages(zone);
+        else
+                watermark = high_wmark_pages(zone);
+        watermark += (1 << cc->order);
+
         if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
                 return COMPACT_CONTINUE;
 
         if (cc->order == -1)
                 return COMPACT_CONTINUE;
 
+        /*
+         * Generating only one page of the right order is not enough
+         * for kswapd, we must continue until we're above the high
+         * watermark as a pool for high order GFP_ATOMIC allocations
+         * too.
+         */
+        if (cc->compact_mode == COMPACT_MODE_KSWAPD)
+                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 */
@@ -514,8 +531,9 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
 }
 
 unsigned long compact_zone_order(struct zone *zone,
-                                                int order, gfp_t gfp_mask,
-                                                bool sync)
+                                 int order, gfp_t gfp_mask,
+                                 bool sync,
+                                 int compact_mode)
 {
         struct compact_control cc = {
                 .nr_freepages = 0,
@@ -524,6 +542,7 @@ unsigned long compact_zone_order(struct zone *zone,
                 .migratetype = allocflags_to_migratetype(gfp_mask),
                 .zone = zone,
                 .sync = sync,
+                .compact_mode = compact_mode,
         };
         INIT_LIST_HEAD(&cc.freepages);
         INIT_LIST_HEAD(&cc.migratepages);
@@ -569,7 +588,8 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist,
                                                                 nodemask) {
                 int status;
 
-                status = compact_zone_order(zone, order, gfp_mask, sync);
+                status = compact_zone_order(zone, order, gfp_mask, sync,
+                                            COMPACT_MODE_DIRECT_RECLAIM);
                 rc = max(status, rc);
 
                 /* If a normal allocation would succeed, stop compacting */
@@ -600,6 +620,7 @@ static int compact_node(int nid)
                         .nr_freepages = 0,
                         .nr_migratepages = 0,
                         .order = -1,
+                        .compact_mode = COMPACT_MODE_DIRECT_RECLAIM,
                 };
 
                 zone = &pgdat->node_zones[zoneid];