From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f69.google.com (mail-pl0-f69.google.com [209.85.160.69]) by kanga.kvack.org (Postfix) with ESMTP id 278B36B0006 for ; Wed, 4 Apr 2018 10:34:51 -0400 (EDT) Received: by mail-pl0-f69.google.com with SMTP id f19-v6so14576987plr.23 for ; Wed, 04 Apr 2018 07:34:51 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id t192si3868277pgb.595.2018.04.04.07.34.49 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 04 Apr 2018 07:34:50 -0700 (PDT) Date: Wed, 4 Apr 2018 16:34:47 +0200 From: Michal Hocko Subject: Re: [PATCH 1/3] mm: memcontrol: Use cgroup_rstat for event accounting Message-ID: <20180404143447.GJ6312@dhcp22.suse.cz> References: <20180324160901.512135-1-tj@kernel.org> <20180324160901.512135-2-tj@kernel.org> <20180404140855.GA28966@cmpxchg.org> <20180404141850.GC28966@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180404141850.GC28966@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Tejun Heo , vdavydov.dev@gmail.com, guro@fb.com, riel@surriel.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, cgroups@vger.kernel.org, linux-mm@kvack.org On Wed 04-04-18 10:18:50, Johannes Weiner wrote: > On Wed, Apr 04, 2018 at 10:08:55AM -0400, Johannes Weiner wrote: > > On Sat, Mar 24, 2018 at 09:08:59AM -0700, Tejun Heo wrote: > > > @@ -91,6 +91,9 @@ struct mem_cgroup_stat_cpu { > > > unsigned long events[MEMCG_NR_EVENTS]; > > > unsigned long nr_page_events; > > > unsigned long targets[MEM_CGROUP_NTARGETS]; > > > + > > > + /* for cgroup rstat delta calculation */ > > > + unsigned long last_events[MEMCG_NR_EVENTS]; > > > }; > > > > > > struct mem_cgroup_reclaim_iter { > > > @@ -233,7 +236,11 @@ struct mem_cgroup { > > > > > > struct mem_cgroup_stat_cpu __percpu *stat_cpu; > > > atomic_long_t stat[MEMCG_NR_STAT]; > > > - atomic_long_t events[MEMCG_NR_EVENTS]; > > > + > > > + /* events is managed by cgroup rstat */ > > > + unsigned long long events[MEMCG_NR_EVENTS]; /* local */ > > > + unsigned long long tree_events[MEMCG_NR_EVENTS]; /* subtree */ > > > + unsigned long long pending_events[MEMCG_NR_EVENTS];/* propagation */ > > > > The lazy updates are neat, but I'm a little concerned at the memory > > footprint. On a 64-cpu machine for example, this adds close to 9000 > > words to struct mem_cgroup. And we really only need the accuracy for > > the 4 cgroup items in memory.events, not all VM events and stats. > > > > Why not restrict the patch to those? It would also get rid of the > > weird sharing between VM and cgroup enums. > > In fact, I wonder if we need per-cpuness for MEMCG_LOW, MEMCG_HIGH > etc. in the first place. They describe super high-level reclaim and > OOM events, so they're not nearly as hot as other VM events and > stats. We could probably just have a per-memcg array of atomics. Agreed! -- Michal Hocko SUSE Labs