From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Tso Subject: Re: [PATCH 9/9] ext3: do not throttle metadata and journal IO Date: Tue, 21 Apr 2009 15:14:01 -0400 Message-ID: <20090421191401.GF15541__16839.7716050551$1240341507$gmane$org@mit.edu> References: <20090417125004.GY4593@kernel.dk> <20090417143903.GA30365@linux> <20090421001822.GB19186@mit.edu> <20090421083001.GA8441@linux> <20090421140631.GF19186@mit.edu> <20090421143130.GA22626@linux> <20090421163537.GI19186@mit.edu> <20090421172317.GM19637@balbir.in.ibm.com> <20090421174620.GD15541@mit.edu> <20090421181429.GO19637@balbir.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20090421181429.GO19637-SINUvgVNF2CyUtPGxGje5AC/G2K4zDHf@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Balbir Singh Cc: randy.dunlap-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, Paul Menage , Carl Henrik Lunde , Jens Axboe , eric.rannaud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, fernando-gVGce1chcLdL9jVzuh4AOg@public.gmane.org, Andrea Righi , dradford-cT2on/YLNlBWk0Htik3J/w@public.gmane.org, agk-9JcytcrH/bA+uJoB2kUjGw@public.gmane.org, subrata-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dave-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org, matt-cT2on/YLNlBWk0Htik3J/w@public.gmane.org, roberto-5KDOxZqKugI@public.gmane.org, ngupta-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org List-Id: containers.vger.kernel.org On Tue, Apr 21, 2009 at 11:44:29PM +0530, Balbir Singh wrote: > > That would be true in general, but only the process writing to the > file will dirty it. So dirty already accounts for the read/write > split. I'd assume that the cost is only for the dirty page, since we > do IO only on write in this case, unless I am missing something very > obvious. Maybe I'm missing something, but the (in development) patches I saw seemed to use the existing infrastructure designed for RSS cost tracking (which is also not yet in mainline, unless I'm mistaken --- but I didn't see page_get_page_cgroup() in the mainline tree yet). Right? So if process A in cgroup A reads touches the file first by reading from it, then the pages read by process A will be assigned as being "owned" by cgroup A. Then when the patch described at http://lkml.org/lkml/2008/9/9/245 ... tries to charge a write done by process B in cgroup B, the code will call page_get_page_cgroup(), see that it is "owned" by cgroup A, and charge the dirty page to cgroup A. If process A and all of the other processes in cgroup A only access this file read-only, and process B is updating this file very heavily --- and it is a large file --- then cgroup B will get a completely free pass as far as dirtying pages to this file, since it will be all charged 100% to cgroup A, incorrectly. So what am I missing? - Ted