Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754109Ab1C1NRQ (ORCPT ); Mon, 28 Mar 2011 09:17:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:15709 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753381Ab1C1NRP (ORCPT ); Mon, 28 Mar 2011 09:17:15 -0400 Date: Mon, 28 Mar 2011 09:17:05 -0400 From: Vivek Goyal To: Chad Talbott Cc: Gui Jianfeng , jaxboe@fusionio.com, linux-kernel@vger.kernel.org, mrubin@google.com, teravest@google.com Subject: Re: [PATCH 0/3] cfq-iosched: Fair cross-group preemption Message-ID: <20110328131705.GB7226@redhat.com> References: <1300756245-12380-1-git-send-email-ctalbott@google.com> <20110322150905.GD3757@redhat.com> <20110322181231.GJ3757@redhat.com> <20110323204146.GK13315@redhat.com> <20110325213202.GB21593@redhat.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/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1805 Lines: 36 On Fri, Mar 25, 2011 at 04:53:13PM -0700, Chad Talbott wrote: > On Fri, Mar 25, 2011 at 2:32 PM, Vivek Goyal wrote: > >> You seem pretty unenthusiastic about a). ?How do you feel about b)? > > > > IMHO, Using RT group with throttling avoids introducing asymmetry between > > task and group attributes. So I will prefer that approch. Though it means > > more code as we will be introducing RT groups but that might be useful > > in general for something else too. (I am assuming that somebody makes > > use of RT class for cfqq). > > > > The one more down side of trying to use throttling is that one needs to > > come up with absolute limit. So one shall have to know disk capacity > > and if there are no BE tasks running then latency sensitive task will > > be unnecessarily throttled (until and unless some management software > > can monitor it and change limit dynamically). > > > > So if you are worried about setting the absolute limit part, then I guess > > I am fine with option a). But if you think that setting absolute limit > > is not a problem, then option b) is preferred. > > I prefer option a) - so much so that even with the older CFQ group > implementation we did work to merge the RT and BE service trees to > achieve that behavior. But I see that using blkio.class is a poor > choice of interface name. I will rename the interface and resubmit > the patch series (also with Gui's suggestion to keep the "_device" > suffix for consistency). Do you need this feature to be global or per device or both? Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/