From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from outbound-smtp08.blacknight.com (outbound-smtp08.blacknight.com [46.22.139.13]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E01A68 for ; Thu, 25 Nov 2021 15:24:47 +0000 (UTC) Received: from mail.blacknight.com (pemlinmail05.blacknight.ie [81.17.254.26]) by outbound-smtp08.blacknight.com (Postfix) with ESMTPS id DE1D61C4FE5 for ; Thu, 25 Nov 2021 15:19:04 +0000 (GMT) Received: (qmail 917 invoked from network); 25 Nov 2021 15:19:04 -0000 Received: from unknown (HELO stampy.112glenside.lan) (mgorman@techsingularity.net@[84.203.17.29]) by 81.17.254.9 with ESMTPA; 25 Nov 2021 15:19:04 -0000 From: Mel Gorman To: Andrew Morton Cc: Michal Hocko , Vlastimil Babka , Alexey Avramov , Rik van Riel , Mike Galbraith , Darrick Wong , regressions@lists.linux.dev, Linux-fsdevel , Linux-MM , LKML , Mel Gorman Subject: [PATCH 1/1] mm: vmscan: Reduce throttling due to a failure to make progress Date: Thu, 25 Nov 2021 15:18:53 +0000 Message-Id: <20211125151853.8540-1-mgorman@techsingularity.net> X-Mailer: git-send-email 2.31.1 Precedence: bulk X-Mailing-List: regressions@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Mike Galbraith, Alexey Avramov and Darrick Wong all reported similar problems due to reclaim throttling for excessive lengths of time. In Alexey's case, a memory hog that should go OOM quickly stalls for several minutes before stalling. In Mike and Darrick's cases, a small memcg environment stalled excessively even though the system had enough memory overall. Commit 69392a403f49 ("mm/vmscan: throttle reclaim when no progress is being made") introduced the problem although commit a19594ca4a8b ("mm/vmscan: increase the timeout if page reclaim is not making progress") made it worse. Systems at or near an OOM state that cannot be recovered must reach OOM quickly and memcg should kill tasks if a memcg is near OOM. To address this, only stall for the first zone in the zonelist, reduce the timeout to 1 tick for VMSCAN_THROTTLE_NOPROGRESS and only stall if the scan control nr_reclaimed is 0 and kswapd is still active. If kswapd has stopped reclaiming due to excessive failures, do not stall at all so that OOM triggers relatively quickly. Alexey's test case was the most straight forward for i in {1..3}; do tail /dev/zero; done On vanilla 5.16-rc1, this test stalled and was reset after 10 minutes. After the patch, the test gets killed after roughly 15 seconds which is the same length of time taken in 5.15. Link: https://lore.kernel.org/r/99e779783d6c7fce96448a3402061b9dc1b3b602.camel@gmx.de Link: https://lore.kernel.org/r/20211124011954.7cab9bb4@mail.inbox.lv Link: https://lore.kernel.org/r/20211022144651.19914-1-mgorman@techsingularity.net Fixes: 69392a403f49 ("mm/vmscan: throttle reclaim when no progress is being made") Signed-off-by: Mel Gorman Tested-by: Darrick J. Wong --- mm/vmscan.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index fb9584641ac7..176ddd28df21 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1057,7 +1057,17 @@ void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason) break; case VMSCAN_THROTTLE_NOPROGRESS: - timeout = HZ/2; + timeout = 1; + + /* + * If kswapd is disabled, reschedule if necessary but do not + * throttle as the system is likely near OOM. + */ + if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES) { + cond_resched(); + return; + } + break; case VMSCAN_THROTTLE_ISOLATED: timeout = HZ/50; @@ -3395,7 +3405,7 @@ static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc) return; /* Throttle if making no progress at high prioities. */ - if (sc->priority < DEF_PRIORITY - 2) + if (sc->priority < DEF_PRIORITY - 2 && !sc->nr_reclaimed) reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS); } @@ -3415,6 +3425,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) unsigned long nr_soft_scanned; gfp_t orig_mask; pg_data_t *last_pgdat = NULL; + pg_data_t *first_pgdat = NULL; /* * If the number of buffer_heads in the machine exceeds the maximum @@ -3478,14 +3489,18 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) /* need some check for avoid more shrink_zone() */ } + if (!first_pgdat) + first_pgdat = zone->zone_pgdat; + /* See comment about same check for global reclaim above */ if (zone->zone_pgdat == last_pgdat) continue; last_pgdat = zone->zone_pgdat; shrink_node(zone->zone_pgdat, sc); - consider_reclaim_throttle(zone->zone_pgdat, sc); } + consider_reclaim_throttle(first_pgdat, sc); + /* * Restore to original mask to avoid the impact on the caller if we * promoted it to __GFP_HIGHMEM. -- 2.31.1