Re: [PATCH v2 4/5] mm, kswapd: replace kswapd compaction with waking up kcompactd

[Vlastimil Babka]

A fixlet for things Joonsoo caught.

----8<----
From: Vlastimil Babka <vba...@suse.cz>
Date: Wed, 2 Mar 2016 11:50:16 +0100
Subject: mm-kswapd-replace-kswapd-compaction-with-waking-up-kcompactd-fix

Change zone_balanced() check in balance_pgdat() to consider only base pages
as that's the same what kswapd_shrink_zone() later does. So a zone that would
be selected due to lack of high-order pages would not be reclaimed anyway,
and just cause extra CPU churn.

Also remove unnecessary variable testorder in kswapd_shrink_zone().

Reported-by: Joonsoo Kim <iamjoonsoo....@lge.com>
Signed-off-by: Vlastimil Babka <vba...@suse.cz>
---
 mm/vmscan.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index b8478a737ef5..23bc7e643ad8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3073,7 +3073,6 @@ static bool kswapd_shrink_zone(struct zone *zone,
                               int classzone_idx,
                               struct scan_control *sc)
 {
-       int testorder = sc->order;
        unsigned long balance_gap;
        bool lowmem_pressure;
 
@@ -3094,7 +3093,7 @@ static bool kswapd_shrink_zone(struct zone *zone,
         * reclaim is necessary
         */
        lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone));
-       if (!lowmem_pressure && zone_balanced(zone, testorder, false,
+       if (!lowmem_pressure && zone_balanced(zone, sc->order, false,
                                                balance_gap, classzone_idx))
                return true;
 
@@ -3109,7 +3108,7 @@ static bool kswapd_shrink_zone(struct zone *zone,
         * waits.
         */
        if (zone_reclaimable(zone) &&
-           zone_balanced(zone, testorder, false, 0, classzone_idx)) {
+           zone_balanced(zone, sc->order, false, 0, classzone_idx)) {
                clear_bit(ZONE_CONGESTED, &zone->flags);
                clear_bit(ZONE_DIRTY, &zone->flags);
        }
@@ -3190,7 +3189,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int 
classzone_idx)
                                break;
                        }
 
-                       if (!zone_balanced(zone, order, true, 0, 0)) {
+                       if (!zone_balanced(zone, order, false, 0, 0)) {
                                end_zone = i;
                                break;
                        } else {
-- 
2.7.2