Commit 06226226 authored Jul 10, 2017 by David Rientjes Committed by Linus Torvalds Jul 10, 2017

mm, vmscan: avoid thrashing anon lru when free + file is low

The purpose of the code that commit 62376251 ("revert 'mm: vmscan:
do not swap anon pages just because free+file is low'") reintroduces is
to prefer swapping anonymous memory rather than trashing the file lru.

If the anonymous inactive lru for the set of eligible zones is
considered low, however, or the length of the list for the given reclaim
priority does not allow for effective anonymous-only reclaiming, then
avoid forcing SCAN_ANON.  Forcing SCAN_ANON will end up thrashing the
small list and leave unreclaimed memory on the file lrus.

If the inactive list is insufficient, fallback to balanced reclaim so
the file lru doesn't remain untouched.

[akpm@linux-foundation.org: fix build]
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1705011432220.137835@chino.kir.corp.google.com


Signed-off-by: David Rientjes <rientjes@google.com>
Suggested-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 0a1345f8

mm/vmscan.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -2228,10 +2228,19 @@ static void get_scan_count(struct lruvec lruvec, struct mem_cgroup memcg,
		}

		if (unlikely(pgdatfile + pgdatfree <= total_high_wmark)) {
		/*
		* Force SCAN_ANON if there are enough inactive
		* anonymous pages on the LRU in eligible zones.
		* Otherwise, the small LRU gets thrashed.
		*/
		if (!inactive_list_is_low(lruvec, false, memcg, sc, false) &&
		lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, sc->reclaim_idx)
		>> sc->priority) {
		scan_balance = SCAN_ANON;
		goto out;
		}
		}
		}

		/*
		* If there is enough inactive page cache, i.e. if the size of the

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