From mboxrd@z Thu Jan 1 00:00:00 1970 From: Curt Wohlgemuth Subject: Re: [Lsf] IO less throttling and cgroup aware writeback (Was: Re: Preliminary Agenda and Activities for LSF) Date: Wed, 6 Apr 2011 10:14:39 -0700 Message-ID: References: <20110330222002.GB20849@dastard> <20110331141637.GA11139@redhat.com> <20110331222756.GC2904@dastard> <20110401171838.GD20986@redhat.com> <20110401214947.GE6957@dastard> <20110405131359.GA14239@redhat.com> <20110405225639.GB31057@dastard> <20110406153715.GA18777@redhat.com> <20110406160805.GC18777@redhat.com> <20110406171017.GA28689@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Vivek Goyal , Dave Chinner , James Bottomley , lsf@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org To: Jan Kara Return-path: Received: from smtp-out.google.com ([74.125.121.67]:46630 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754587Ab1DFROn convert rfc822-to-8bit (ORCPT ); Wed, 6 Apr 2011 13:14:43 -0400 Received: from wpaz37.hot.corp.google.com (wpaz37.hot.corp.google.com [172.24.198.101]) by smtp-out.google.com with ESMTP id p36HEevE015092 for ; Wed, 6 Apr 2011 10:14:40 -0700 Received: from qwf7 (qwf7.prod.google.com [10.241.194.71]) by wpaz37.hot.corp.google.com with ESMTP id p36HBBTB019841 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for ; Wed, 6 Apr 2011 10:14:39 -0700 Received: by qwf7 with SMTP id 7so1207803qwf.24 for ; Wed, 06 Apr 2011 10:14:39 -0700 (PDT) In-Reply-To: <20110406171017.GA28689@quack.suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, Apr 6, 2011 at 10:10 AM, Jan Kara wrote: > On Wed 06-04-11 12:08:05, Vivek Goyal wrote: >> On Wed, Apr 06, 2011 at 11:37:15AM -0400, Vivek Goyal wrote: >> >> [..] >> > > what kswapd is going to do writeback when the pages >> > > it's trying to writeback during a critical low memory event belo= ng >> > > to a cgroup that is throttled at the IO level, etc. >> > >> > Throttling will move up so kswapd will not be throttled. Even toda= y, >> > kswapd is part of root group and we do not suggest throttling root= group. >> > >> > For the case of proportional disk sharing, we will probably accoun= t >> > IO to respective cgroups (pages submitted by kswapd) and that shou= ld >> > not flush to disk fairly fast and should not block for long time a= s it is >> > work consering mechanism. >> > >> > Do you see an issue with kswapd IO being accounted to respective c= groups >> > for proportional IO. For throttling case, all IO would go to root = group >> > which is unthrottled and real issue of dirtying too many pages by >> > processes will be handled by throttling processes when they are di= rtying >> > page cache. >> >> Or may be it is not a good idea to try to account pages to associate= d >> cgroups when memory is low and kswapd is doing IO. We can probably m= ark >> kswapd with some flag and account all IO to root group even for >> proportional weight mechanism. In this case isolation will be broken= but >> I guess one can not do much. To avoid this situation, one should not >> have allowed too many writes and I think that's where low dirty rati= o >> can come into the picture. > =A0Well, I wouldn't bother too much with kswapd handling. MM people p= lan to > get rid of writeback from direct reclaim and just remove the dirty pa= ge > from LRU and recycle it once flusher thread writes it... But still, it matters which memcg is "responsible" for the background writeout from direct reclaim. One could argue that direct reclaim should just specify the root cgroup... Curt > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0= =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Honza > -- > Jan Kara > SUSE Labs, CR > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdev= el" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at =A0http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html