From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [Patch v2 3/3] mm/memcg: add next_mz back to soft limit tree if not reclaimed yet Date: Mon, 14 Mar 2022 10:41:13 +0100 Message-ID: References: <20220312071623.19050-1-richard.weiyang@gmail.com> <20220312071623.19050-3-richard.weiyang@gmail.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1647250873; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=vjCAmfOeIAmJsBLZGTQdftIhcJ0qr7uynuuuQ3TesCo=; b=NzzajjqEfhDUN2nmysnf+Itb4aFQe8SNtcbcddDI3ZQKOLMqLXLomuKFhQbSjmDeW6Lekw 7b5Hl1XvWv8QXxMRHPR6mBKZIsXYiF69jyNsz+nsuhsZ2iZB/auOvRvq5e22Q+WIs2Hc3R DfgIu7LRtH+3wSJn0pEhnJzOMIKDtUE= Content-Disposition: inline In-Reply-To: <20220312071623.19050-3-richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Wei Yang Cc: hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org On Sat 12-03-22 07:16:23, Wei Yang wrote: > When memory reclaim failed for a maximum number of attempts and we bail > out of the reclaim loop, we forgot to put the target mem_cgroup chosen > for next reclaim back to the soft limit tree. This prevented pages in > the mem_cgroup from being reclaimed in the future even though the > mem_cgroup exceeded its soft limit. > > Let's say there are two mem_cgroup and both of them exceed the soft > limit, while the first one is more active then the second. Since we add > a mem_cgroup to soft limit tree every 1024 event, the second one just > get a rare chance to be put on soft limit tree even it exceeds the > limit. yes, 1024 could be just 4MB of memory or 2GB if all the charged pages are THPs. So the excess can build up considerably. > As time goes on, the first mem_cgroup was kept close to its soft limit > due to reclaim activities, while the memory usage of the second > mem_cgroup keeps growing over the soft limit for a long time due to its > relatively rare occurrence. > > This patch adds next_mz back to prevent this sceanrio. > > Signed-off-by: Wei Yang Even though your changelog is different the change itself is identical to https://lore.kernel.org/linux-mm/8d35206601ccf0e1fe021d24405b2a0c2f4e052f.1613584277.git.tim.c.chen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org/ In those cases I would preserve the the original authorship by From: Tim Chen and add his s-o-b before yours. Acked-by: Michal Hocko Thanks! > --- > mm/memcontrol.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 344a7e891bc5..e803ff02aae2 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3493,8 +3493,13 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order, > loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS)) > break; > } while (!nr_reclaimed); > - if (next_mz) > + if (next_mz) { > + spin_lock_irq(&mctz->lock); > + excess = soft_limit_excess(next_mz->memcg); > + __mem_cgroup_insert_exceeded(next_mz, mctz, excess); > + spin_unlock_irq(&mctz->lock); > css_put(&next_mz->memcg->css); > + } > return nr_reclaimed; > } > > -- > 2.33.1 -- Michal Hocko SUSE Labs