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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@alibaba-inc.com: Force kswapd reclaim no more than needed] Link: http://lkml.kernel.org/r/1466518566-30034-12-git-send-email-mgorman@techsingularity.net Link: http://lkml.kernel.org/r/1467970510-21195-13-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Hillf Danton <hillf.zj@alibaba-inc.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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parent
6256c6b499
commit
86c79f6b54
59
mm/vmscan.c
59
mm/vmscan.c
@ -3144,31 +3144,39 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
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sc.nr_reclaimed = 0;
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sc.nr_reclaimed = 0;
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/* Scan from the highest requested zone to dma */
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/*
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for (i = classzone_idx; i >= 0; i--) {
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* If the number of buffer_heads in the machine exceeds the
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zone = pgdat->node_zones + i;
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* maximum allowed level then reclaim from all zones. This is
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if (!populated_zone(zone))
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* not specific to highmem as highmem may not exist but it is
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continue;
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* it is expected that buffer_heads are stripped in writeback.
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*/
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if (buffer_heads_over_limit) {
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for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
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zone = pgdat->node_zones + i;
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if (!populated_zone(zone))
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continue;
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/*
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* If the number of buffer_heads in the machine
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* exceeds the maximum allowed level and this node
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* has a highmem zone, force kswapd to reclaim from
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* it to relieve lowmem pressure.
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*/
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if (buffer_heads_over_limit && is_highmem_idx(i)) {
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classzone_idx = i;
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break;
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}
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if (!zone_balanced(zone, order, 0)) {
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classzone_idx = i;
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classzone_idx = i;
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break;
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break;
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}
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}
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}
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}
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if (i < 0)
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/*
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goto out;
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* Only reclaim if there are no eligible zones. Check from
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* high to low zone as allocations prefer higher zones.
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* Scanning from low to high zone would allow congestion to be
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* cleared during a very small window when a small low
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* zone was balanced even under extreme pressure when the
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* overall node may be congested.
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*/
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for (i = classzone_idx; i >= 0; i--) {
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zone = pgdat->node_zones + i;
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if (!populated_zone(zone))
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continue;
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if (zone_balanced(zone, sc.order, classzone_idx))
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goto out;
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}
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/*
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/*
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* Do some background aging of the anon list, to give
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* Do some background aging of the anon list, to give
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@ -3213,19 +3221,6 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
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if (try_to_freeze() || kthread_should_stop())
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if (try_to_freeze() || kthread_should_stop())
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break;
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break;
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/*
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* Stop reclaiming if any eligible zone is balanced and clear
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* node writeback or congested.
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*/
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for (i = 0; i <= classzone_idx; i++) {
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zone = pgdat->node_zones + i;
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if (!populated_zone(zone))
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continue;
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if (zone_balanced(zone, sc.order, classzone_idx))
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goto out;
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}
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/*
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/*
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* Raise priority if scanning rate is too low or there was no
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* Raise priority if scanning rate is too low or there was no
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* progress in reclaiming pages
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* progress in reclaiming pages
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