From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200]) by kanga.kvack.org (Postfix) with ESMTP id C26FB6B025F for ; Wed, 30 Aug 2017 10:24:02 -0400 (EDT) Received: by mail-wr0-f200.google.com with SMTP id 40so8718570wrv.4 for ; Wed, 30 Aug 2017 07:24:02 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id o62si1720381wmo.233.2017.08.30.07.24.01 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 30 Aug 2017 07:24:01 -0700 (PDT) Date: Wed, 30 Aug 2017 16:23:59 +0200 From: Michal Hocko Subject: Re: [PATCH] mm: memcontrol: use per-cpu stocks for socket memory uncharging Message-ID: <20170830142359.anh6l7ey3eq6fksu@dhcp22.suse.cz> References: <20170829100150.4580-1-guro@fb.com> <20170830123655.6kce7yfkrhrhwubu@dhcp22.suse.cz> <20170830124459.GA10438@castle.DHCP.thefacebook.com> <20170830125543.um72yjhzps4lbj4t@dhcp22.suse.cz> <20170830125729.GA12012@castle.DHCP.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170830125729.GA12012@castle.DHCP.thefacebook.com> Sender: owner-linux-mm@kvack.org List-ID: To: Roman Gushchin Cc: linux-mm@kvack.org, Johannes Weiner , Vladimir Davydov , cgroups@vger.kernel.org, kernel-team@fb.com, linux-kernel@vger.kernel.org On Wed 30-08-17 13:57:29, Roman Gushchin wrote: > On Wed, Aug 30, 2017 at 02:55:43PM +0200, Michal Hocko wrote: > > On Wed 30-08-17 13:44:59, Roman Gushchin wrote: > > > On Wed, Aug 30, 2017 at 02:36:55PM +0200, Michal Hocko wrote: > > > > On Tue 29-08-17 11:01:50, Roman Gushchin wrote: > > > > [...] > > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > > > > index b9cf3cf4a3d0..a69d23082abf 100644 > > > > > --- a/mm/memcontrol.c > > > > > +++ b/mm/memcontrol.c > > > > > @@ -1792,6 +1792,9 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) > > > > > } > > > > > stock->nr_pages += nr_pages; > > > > > > > > > > + if (stock->nr_pages > CHARGE_BATCH) > > > > > + drain_stock(stock); > > > > > + > > > > > local_irq_restore(flags); > > > > > } > > > > > > > > Why do we need this? In other words, why cannot we rely on draining we > > > > already do? > > > > > > The existing draining depends on memory pressure, so to keep > > > the accounting (which we expose to a user) reasonable accurate > > > even without memory pressure, we need to limit the size of per-cpu stocks. > > > > Why don't we need this for regular page charges? Or maybe we do but that > > sounds like a seprate and an unrealted fix to me. > > Because we never refill more than CHARGE_BATCH. You are right that a single process will not but try_charge is a preemptible context and so multiple processes might pass consume_stock and then charge a N*CHARGE_BATCH. But I agree that this is quite unlikely so a separate patch is probably not worth it. -- 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