The patch titled
Subject: mm: vmscan: do not reclaim from kswapd if there is any eligible zone
has been added to the -mm tree. Its filename is
mm-vmscan-do-not-reclaim-from-kswapd-if-there-is-any-eligible-zone.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-vmscan-do-not-reclaim-from-kswapd-if-there-is-any-eligible-zone.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-vmscan-do-not-reclaim-from-kswapd-if-there-is-any-eligible-zone.patch
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------------------------------------------------------
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>
Cc: 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
mm-meminit-always-return-a-valid-node-from-early_pfn_to_nid.patch
mm-meminit-ensure-node-is-online-before-checking-whether-pages-are-uninitialised.patch
mm-meminit-remove-early_page_nid_uninitialised.patch
mm-vmstat-add-infrastructure-for-per-node-vmstats.patch
mm-vmscan-move-lru_lock-to-the-node.patch
mm-vmscan-move-lru-lists-to-node.patch
mm-mmzone-clarify-the-usage-of-zone-padding.patch
mm-vmscan-begin-reclaiming-pages-on-a-per-node-basis.patch
mm-vmscan-have-kswapd-only-scan-based-on-the-highest-requested-zone.patch
mm-vmscan-make-kswapd-reclaim-in-terms-of-nodes.patch
mm-vmscan-remove-balance-gap.patch
mm-vmscan-simplify-the-logic-deciding-whether-kswapd-sleeps.patch
mm-vmscan-by-default-have-direct-reclaim-only-shrink-once-per-node.patch
mm-vmscan-remove-duplicate-logic-clearing-node-congestion-and-dirty-state.patch
mm-vmscan-do-not-reclaim-from-kswapd-if-there-is-any-eligible-zone.patch
mm-vmscan-make-shrink_node-decisions-more-node-centric.patch
mm-memcg-move-memcg-limit-enforcement-from-zones-to-nodes.patch
mm-workingset-make-working-set-detection-node-aware.patch
mm-page_alloc-consider-dirtyable-memory-in-terms-of-nodes.patch
mm-move-page-mapped-accounting-to-the-node.patch
mm-rename-nr_anon_pages-to-nr_anon_mapped.patch
mm-move-most-file-based-accounting-to-the-node.patch
mm-move-vmscan-writes-and-file-write-accounting-to-the-node.patch
mm-vmscan-only-wakeup-kswapd-once-per-node-for-the-requested-classzone.patch
mm-page_alloc-wake-kswapd-based-on-the-highest-eligible-zone.patch
mm-convert-zone_reclaim-to-node_reclaim.patch
mm-vmscan-avoid-passing-in-classzone_idx-unnecessarily-to-shrink_node.patch
mm-vmscan-avoid-passing-in-classzone_idx-unnecessarily-to-compaction_ready.patch
mm-vmscan-avoid-passing-in-remaining-unnecessarily-to-prepare_kswapd_sleep.patch
mm-vmscan-have-kswapd-reclaim-from-all-zones-if-reclaiming-and-buffer_heads_over_limit.patch
mm-vmscan-add-classzone-information-to-tracepoints.patch
mm-page_alloc-remove-fair-zone-allocation-policy.patch
mm-page_alloc-cache-the-last-node-whose-dirty-limit-is-reached.patch
mm-vmstat-replace-__count_zone_vm_events-with-a-zone-id-equivalent.patch
mm-vmstat-account-per-zone-stalls-and-pages-skipped-during-reclaim.patch
mm-vmstat-print-node-based-stats-in-zoneinfo-file.patch
mm-vmstat-remove-zone-and-node-double-accounting-by-approximating-retries.patch
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