[PATCH 12/27] mm: vmscan: Do not reclaim from kswapd if there is any eligible zone
From: Mel Gorman <hidden>
Date: 2016-02-23 15:06:43
Also in:
lkml
Subsystem:
memory management, memory management - mglru (multi-gen lru), memory management - reclaim, the rest · Maintainers:
Andrew Morton, Johannes Weiner, Linus Torvalds
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. Signed-off-by: Mel Gorman <redacted> --- mm/vmscan.c | 32 +++++++++++++++++++------------- 1 file changed, 19 insertions(+), 13 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1f5d3829d35e..39ad2ab76a2b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c@@ -3123,24 +3123,30 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) sc.nr_reclaimed = 0; - /* Scan from the highest requested zone to dma */ + /* + * 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) { + for (i = MAX_NR_ZONES - 1; i >= 0; i++) { + zone = pgdat->node_zones + i; + if (!populated_zone(zone)) + continue; + + if (is_highmem_idx(i)) + classzone_idx = i; + break; + } + } + + /* Only reclaim if there are no eligible zones */ 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 (!zone_balanced(zone, order, 0, 0)) { + if (!zone_balanced(zone, order, 0, classzone_idx)) { classzone_idx = i; break; }
--
2.6.4
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