vmscan: count pages into balanced for zone with good watermark

It's possible a zone watermark is ok when entering the balance_pgdat()
loop, while the zone is within the requested classzone_idx.  Count pages
from this zone into `balanced'.  In this way, we can skip shrinking zones
too much for high order allocation.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index a297603d35bc..77ee24fc891a 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2748,6 +2748,8 @@ out:
 
                         /* If balanced, clear the congested flag */
                         zone_clear_flag(zone, ZONE_CONGESTED);
+                        if (i <= *classzone_idx)
+                                balanced += zone->present_pages;
                 }
         }