linux-kernel - Re: [patch v2] mm, vmscan: avoid thrashing anon lru when free + file is low

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Message-Id: <20170602133637.7f6b49fbb740fb70e3b2307d@linux-foundation.org>
Date:   Fri, 2 Jun 2017 13:36:37 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Minchan Kim <minchan@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch v2] mm, vmscan: avoid thrashing anon lru when free +
 file is low

On Mon, 1 May 2017 14:34:21 -0700 (PDT) David Rientjes <rientjes@...gle.com> wrote:

> The purpose of the code that commit 623762517e23 ("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.
> 

--- a/mm/vmscan.c~mm-vmscan-avoid-thrashing-anon-lru-when-free-file-is-low-fix
+++ a/mm/vmscan.c
@@ -2233,7 +2233,7 @@ static void get_scan_count(struct lruvec
 			 * anonymous pages on the LRU in eligible zones.
 			 * Otherwise, the small LRU gets thrashed.
 			 */
-			if (!inactive_list_is_low(lruvec, false, sc, false) &&
+			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;

Worried.  Did you send the correct version?