[patch 139/158] autonuma: fix watermark checking in migrate_balanced_pgdat()

[patch 139/158] autonuma: fix watermark checking in migrate_balanced_pgdat()

[akpm]

From: Huang Ying <ying.huang@intel.com>
Subject: autonuma: fix watermark checking in migrate_balanced_pgdat()

When zone_watermark_ok() is called in migrate_balanced_pgdat() to check
migration target node, the parameter classzone_idx (for requested zone) is
specified as 0 (ZONE_DMA).  But when allocating memory for autonuma in
alloc_misplaced_dst_page(), the requested zone from GFP flags is
ZONE_MOVABLE.  That is, the requested zone is different.  The size of
lowmem_reserve for the different requested zone is different.  And this
may cause some issues.

For example, in the zoneinfo of a test machine as below,

Node 0, zone    DMA32
  pages free     61592
        min      29
        low      454
        high     879
        spanned  1044480
        present  442306
        managed  425921
        protection: (0, 0, 62457, 62457, 62457)

The free page number of ZONE_DMA32 is greater than "high watermark +
lowmem_reserve[ZONE_DMA]", but less than "high watermark +
lowmem_reserve[ZONE_MOVABLE]".  And because __alloc_pages_node() in
alloc_misplaced_dst_page() requests ZONE_MOVABLE, the zone_watermark_ok()
on ZONE_DMA32 in migrate_balanced_pgdat() may always return true.  So,
autonuma may not stop even when memory pressure in node 0 is heavy.

To fix the issue, ZONE_MOVABLE is used as parameter to call
zone_watermark_ok() in migrate_balanced_pgdat().  This makes it same as
requested zone in alloc_misplaced_dst_page().  So that
migrate_balanced_pgdat() returns false when memory pressure is heavy.

Link: http://lkml.kernel.org/r/20191101075727.26683-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/migrate.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/migrate.c~autonuma-fix-watermark-checking-in-migrate_balanced_pgdat
+++ a/mm/migrate.c
@@ -1859,7 +1859,7 @@ static bool migrate_balanced_pgdat(struc
 		if (!zone_watermark_ok(zone, 0,
 				       high_wmark_pages(zone) +
 				       nr_migrate_pages,
-				       0, 0))
+				       ZONE_MOVABLE, 0))
 			continue;
 		return true;
 	}
_