From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f176.google.com (mail-we0-f176.google.com [74.125.82.176]) by kanga.kvack.org (Postfix) with ESMTP id 3DAAD6B0037 for ; Tue, 8 Jul 2014 18:19:14 -0400 (EDT) Received: by mail-we0-f176.google.com with SMTP id u56so6563743wes.21 for ; Tue, 08 Jul 2014 15:19:13 -0700 (PDT) Received: from zene.cmpxchg.org (zene.cmpxchg.org. [2a01:238:4224:fa00:ca1f:9ef3:caee:a2bd]) by mx.google.com with ESMTPS id l14si4982277wiw.91.2014.07.08.15.19.13 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 08 Jul 2014 15:19:13 -0700 (PDT) Date: Tue, 8 Jul 2014 18:19:06 -0400 From: Johannes Weiner Subject: Re: [PATCH -mm 0/8] memcg: reparent kmem on css offline Message-ID: <20140708221906.GC29639@cmpxchg.org> References: <20140707142506.GB1149@cmpxchg.org> <53BAD567.8060506@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53BAD567.8060506@parallels.com> Sender: owner-linux-mm@kvack.org List-ID: To: Vladimir Davydov Cc: akpm@linux-foundation.org, mhocko@suse.cz, cl@linux.com, glommer@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Mon, Jul 07, 2014 at 09:14:15PM +0400, Vladimir Davydov wrote: > 07.07.2014 18:25, Johannes Weiner: > >In addition, Tejun made offlined css iterable and split css_tryget() > >and css_tryget_online(), which would allow memcg to pin the css until > >the last charge is gone while continuing to iterate and reclaim it on > >hierarchical pressure, even after it was offlined. > > One more question. > > With reparenting enabled, the number of cgroups (lruvecs) that must be > iterated on global reclaim is bound by the number of live containers, > while w/o reparenting it's practically unbound, isn't it? Won't it be > the source of latency spikes? It might deteriorate a little bit, but it is a self-correcting problem as soon as memory pressure kicks. Creating and destroying cgroups is serialized at a global level, so I would expect the cost of doing that at a high rate to become a problem before the csss become an issue for the reclaim scanner. At some point we will probably have to make the global reclaim cgroup walk in shrink_zone() intermittent, but I'm not aware of any problems with it so far. -- 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