From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755207Ab0GJNYo (ORCPT ); Sat, 10 Jul 2010 09:24:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:30866 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755001Ab0GJNYm (ORCPT ); Sat, 10 Jul 2010 09:24:42 -0400 Date: Sat, 10 Jul 2010 09:24:17 -0400 From: Vivek Goyal To: Nauman Rafique Cc: Munehiro Ikeda , linux-kernel@vger.kernel.org, Ryo Tsuruta , taka@valinux.co.jp, kamezawa.hiroyu@jp.fujitsu.com, Andrea Righi , Gui Jianfeng , akpm@linux-foundation.org, balbir@linux.vnet.ibm.com Subject: Re: [RFC][PATCH 00/11] blkiocg async support Message-ID: <20100710132417.GA2752@redhat.com> References: <4C369009.80503@ds.jp.nec.com> <20100709134546.GC3672@redhat.com> <4C37BC1A.20102@ds.jp.nec.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 09, 2010 at 05:55:23PM -0700, Nauman Rafique wrote: [..] > > Well, right.  I agree. > > But I think we can work parallel.  I will try to struggle on both. > > IMHO, we have a classic chicken and egg problem here. We should try to > merge pieces as they become available. If we get to agree on patches > that do async IO tracking for IO controller, we should go ahead with > them instead of trying to wait for per cgroup dirty ratios. > > In terms of getting numbers, we have been using patches that add per > cpuset dirty ratios on top of NUMA_EMU, and we get good > differentiation between buffered writes as well as buffered writes vs. > reads. > > It is really obvious that as long as flusher threads ,etc are not > cgroup aware, differentiation for buffered writes would not be perfect > in all cases, but this is a step in the right direction and we should > go for it. Working parallel on two separate pieces is fine. But pushing second piece in first does not make much sense to me because second piece does not work if first piece is not in. There is no way to test it. What's the point of pushing a code in kernel which only compiles but does not achieve intented purposes because some other pieces are missing. Per cgroup dirty ratio is a little hard problem and few attempts have already been made at it. IMHO, we need to first work on that piece and get it inside the kernel and then work on IO tracking patches. Lets fix the hard problem first that is necessary to make second set of patches work. Thanks Vivek