From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752942AbdCAPxr (ORCPT ); Wed, 1 Mar 2017 10:53:47 -0500 Received: from mx2.suse.de ([195.135.220.15]:52719 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752340AbdCAPxm (ORCPT ); Wed, 1 Mar 2017 10:53:42 -0500 Date: Wed, 1 Mar 2017 16:21:44 +0100 From: Michal Hocko To: Johannes Weiner Cc: Andrew Morton , Jia He , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 5/9] mm: don't avoid high-priority reclaim on unreclaimable nodes Message-ID: <20170301152144.GE11730@dhcp22.suse.cz> References: <20170228214007.5621-1-hannes@cmpxchg.org> <20170228214007.5621-6-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170228214007.5621-6-hannes@cmpxchg.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 28-02-17 16:40:03, Johannes Weiner wrote: > 246e87a93934 ("memcg: fix get_scan_count() for small targets") sought > to avoid high reclaim priorities for kswapd by forcing it to scan a > minimum amount of pages when lru_pages >> priority yielded nothing. > > b95a2f2d486d ("mm: vmscan: convert global reclaim to per-memcg LRU > lists"), due to switching global reclaim to a round-robin scheme over > all cgroups, had to restrict this forceful behavior to unreclaimable > zones in order to prevent massive overreclaim with many cgroups. > > The latter patch effectively neutered the behavior completely for all > but extreme memory pressure. But in those situations we might as well > drop the reclaimers to lower priority levels. Remove the check. > > Signed-off-by: Johannes Weiner Acked-by: Michal Hocko > --- > mm/vmscan.c | 19 +++++-------------- > 1 file changed, 5 insertions(+), 14 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 911957b66622..46b6223fe7f3 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2129,22 +2129,13 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg, > int pass; > > /* > - * If the zone or memcg is small, nr[l] can be 0. This > - * results in no scanning on this priority and a potential > - * priority drop. Global direct reclaim can go to the next > - * zone and tends to have no problems. Global kswapd is for > - * zone balancing and it needs to scan a minimum amount. When > + * If the zone or memcg is small, nr[l] can be 0. When > * reclaiming for a memcg, a priority drop can cause high > - * latencies, so it's better to scan a minimum amount there as > - * well. > + * latencies, so it's better to scan a minimum amount. When a > + * cgroup has already been deleted, scrape out the remaining > + * cache forcefully to get rid of the lingering state. > */ > - if (current_is_kswapd()) { > - if (!pgdat_reclaimable(pgdat)) > - force_scan = true; > - if (!mem_cgroup_online(memcg)) > - force_scan = true; > - } > - if (!global_reclaim(sc)) > + if (!global_reclaim(sc) || !mem_cgroup_online(memcg)) > force_scan = true; > > /* If we have no swap space, do not bother scanning anon pages. */ > -- > 2.11.1 -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 745B46B0389 for ; Wed, 1 Mar 2017 10:21:46 -0500 (EST) Received: by mail-wr0-f199.google.com with SMTP id u48so18161907wrc.0 for ; Wed, 01 Mar 2017 07:21:46 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id n9si6972439wra.117.2017.03.01.07.21.45 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 01 Mar 2017 07:21:45 -0800 (PST) Date: Wed, 1 Mar 2017 16:21:44 +0100 From: Michal Hocko Subject: Re: [PATCH 5/9] mm: don't avoid high-priority reclaim on unreclaimable nodes Message-ID: <20170301152144.GE11730@dhcp22.suse.cz> References: <20170228214007.5621-1-hannes@cmpxchg.org> <20170228214007.5621-6-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170228214007.5621-6-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Andrew Morton , Jia He , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com On Tue 28-02-17 16:40:03, Johannes Weiner wrote: > 246e87a93934 ("memcg: fix get_scan_count() for small targets") sought > to avoid high reclaim priorities for kswapd by forcing it to scan a > minimum amount of pages when lru_pages >> priority yielded nothing. > > b95a2f2d486d ("mm: vmscan: convert global reclaim to per-memcg LRU > lists"), due to switching global reclaim to a round-robin scheme over > all cgroups, had to restrict this forceful behavior to unreclaimable > zones in order to prevent massive overreclaim with many cgroups. > > The latter patch effectively neutered the behavior completely for all > but extreme memory pressure. But in those situations we might as well > drop the reclaimers to lower priority levels. Remove the check. > > Signed-off-by: Johannes Weiner Acked-by: Michal Hocko > --- > mm/vmscan.c | 19 +++++-------------- > 1 file changed, 5 insertions(+), 14 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 911957b66622..46b6223fe7f3 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2129,22 +2129,13 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg, > int pass; > > /* > - * If the zone or memcg is small, nr[l] can be 0. This > - * results in no scanning on this priority and a potential > - * priority drop. Global direct reclaim can go to the next > - * zone and tends to have no problems. Global kswapd is for > - * zone balancing and it needs to scan a minimum amount. When > + * If the zone or memcg is small, nr[l] can be 0. When > * reclaiming for a memcg, a priority drop can cause high > - * latencies, so it's better to scan a minimum amount there as > - * well. > + * latencies, so it's better to scan a minimum amount. When a > + * cgroup has already been deleted, scrape out the remaining > + * cache forcefully to get rid of the lingering state. > */ > - if (current_is_kswapd()) { > - if (!pgdat_reclaimable(pgdat)) > - force_scan = true; > - if (!mem_cgroup_online(memcg)) > - force_scan = true; > - } > - if (!global_reclaim(sc)) > + if (!global_reclaim(sc) || !mem_cgroup_online(memcg)) > force_scan = true; > > /* If we have no swap space, do not bother scanning anon pages. */ > -- > 2.11.1 -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org