The patch titled
Subject: mm: vmscan: do not reclaim from kswapd if there is any eligible zone
has been removed from the -mm tree. Its filename was
mm-vmscan-do-not-reclaim-from-kswapd-if-there-is-any-eligible-zone.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm: vmscan: do not reclaim from kswapd if there is any eligible zone
kswapd scans from highest to lowest for a zone that requires balancing.
This was necessary when reclaim was per-zone to fairly age pages on lower
zones. Now that we are reclaiming on a per-node basis, any eligible zone
can be used and pages will still be aged fairly. This patch avoids
reclaiming excessively unless buffer_heads are over the limit and it's
necessary to reclaim from a higher zone than requested by the waker of
kswapd to relieve low memory pressure.
[hillf.zj@xxxxxxxxxxxxxxx: Force kswapd reclaim no more than needed]
Link: http://lkml.kernel.org/r/1466518566-30034-12-git-send-email-mgorman@xxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1467970510-21195-13-git-send-email-mgorman@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 59 ++++++++++++++++++++++----------------------------
1 file changed, 27 insertions(+), 32 deletions(-)
diff -puN mm/vmscan.c~mm-vmscan-do-not-reclaim-from-kswapd-if-there-is-any-eligible-zone mm/vmscan.c
--- a/mm/vmscan.c~mm-vmscan-do-not-reclaim-from-kswapd-if-there-is-any-eligible-zone
+++ a/mm/vmscan.c
@@ -3144,31 +3144,39 @@ static int balance_pgdat(pg_data_t *pgda
sc.nr_reclaimed = 0;
- /* Scan from the highest requested zone to dma */
- for (i = classzone_idx; i >= 0; i--) {
- zone = pgdat->node_zones + i;
- if (!populated_zone(zone))
- continue;
-
- /*
- * If the number of buffer_heads in the machine
- * exceeds the maximum allowed level and this node
- * has a highmem zone, force kswapd to reclaim from
- * it to relieve lowmem pressure.
- */
- if (buffer_heads_over_limit && is_highmem_idx(i)) {
- classzone_idx = i;
- break;
- }
+ /*
+ * If the number of buffer_heads in the machine exceeds the
+ * maximum allowed level then reclaim from all zones. This is
+ * not specific to highmem as highmem may not exist but it is
+ * it is expected that buffer_heads are stripped in writeback.
+ */
+ if (buffer_heads_over_limit) {
+ for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
+ zone = pgdat->node_zones + i;
+ if (!populated_zone(zone))
+ continue;
- if (!zone_balanced(zone, order, 0)) {
classzone_idx = i;
break;
}
}
- if (i < 0)
- goto out;
+ /*
+ * Only reclaim if there are no eligible zones. Check from
+ * high to low zone as allocations prefer higher zones.
+ * Scanning from low to high zone would allow congestion to be
+ * cleared during a very small window when a small low
+ * zone was balanced even under extreme pressure when the
+ * overall node may be congested.
+ */
+ for (i = classzone_idx; i >= 0; i--) {
+ zone = pgdat->node_zones + i;
+ if (!populated_zone(zone))
+ continue;
+
+ if (zone_balanced(zone, sc.order, classzone_idx))
+ goto out;
+ }
/*
* Do some background aging of the anon list, to give
@@ -3214,19 +3222,6 @@ static int balance_pgdat(pg_data_t *pgda
break;
/*
- * Stop reclaiming if any eligible zone is balanced and clear
- * node writeback or congested.
- */
- for (i = 0; i <= classzone_idx; i++) {
- zone = pgdat->node_zones + i;
- if (!populated_zone(zone))
- continue;
-
- if (zone_balanced(zone, sc.order, classzone_idx))
- goto out;
- }
-
- /*
* Raise priority if scanning rate is too low or there was no
* progress in reclaiming pages
*/
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
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