From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756033Ab1HEHnp (ORCPT ); Fri, 5 Aug 2011 03:43:45 -0400 Received: from mx1.fusionio.com ([66.114.96.30]:45327 "EHLO mx1.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753926Ab1HEHnm (ORCPT ); Fri, 5 Aug 2011 03:43:42 -0400 X-ASG-Debug-ID: 1312530221-03d6a510a62582e0001-xx1T2L X-Barracuda-Envelope-From: JAxboe@fusionio.com Message-ID: <4E3B9F2C.7080809@fusionio.com> Date: Fri, 5 Aug 2011 09:43:40 +0200 From: Jens Axboe MIME-Version: 1.0 To: Vivek Goyal CC: linux kernel mailing list , Shaohua Li , Suresh Jayaraman , Moyer Jeff Moyer , Christoph Hellwig Subject: Re: [PATCH] cfq-iosched: Add documentation about idling [V2] References: <20110802174006.GD6399@redhat.com> X-ASG-Orig-Subj: Re: [PATCH] cfq-iosched: Add documentation about idling [V2] In-Reply-To: <20110802174006.GD6399@redhat.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Barracuda-Connect: mail1.int.fusionio.com[10.101.1.21] X-Barracuda-Start-Time: 1312530221 X-Barracuda-URL: http://10.101.1.180:8000/cgi-mod/mark.cgi X-Barracuda-Spam-Score: 0.00 X-Barracuda-Spam-Status: No, SCORE=0.00 using per-user scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=1000.0 KILL_LEVEL=9.0 tests= X-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.2.70955 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------------------------- Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2011-08-02 19:40, Vivek Goyal wrote: > There are always questions about why CFQ is idling on various conditions. > Recent ones is Christoph asking again why to idle on REQ_NOIDLE. His > assertion is that XFS is relying more and more on workqueues and is > concerned that CFQ idling on IO from every workqueue will impact > XFS badly. > > So he suggested that I add some more documentation about CFQ idling > and that can provide more clarity on the topic and also gives an > opprotunity to poke a hole in theory and lead to improvements. > > So here is my attempt at that. Any comments are welcome. Applied, thanks. -- Jens Axboe