From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758236Ab0FUUAN (ORCPT ); Mon, 21 Jun 2010 16:00:13 -0400 Received: from 0122700014.0.fullrate.dk ([95.166.99.235]:56282 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758191Ab0FUUAL (ORCPT ); Mon, 21 Jun 2010 16:00:11 -0400 Message-ID: <4C1FC4CA.7030007@kernel.dk> Date: Mon, 21 Jun 2010 22:00:10 +0200 From: Jens Axboe MIME-Version: 1.0 To: Jeff Moyer CC: linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] cfq: always return false from should_idle if slice_idle is set to zero References: <1277149789-4493-1-git-send-email-jmoyer@redhat.com> <1277149789-4493-2-git-send-email-jmoyer@redhat.com> In-Reply-To: <1277149789-4493-2-git-send-email-jmoyer@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/06/10 21.49, Jeff Moyer wrote: > Hi, > > In testing a competing fsync-ing process and a sequential reader on > mid-grade storage, I found that cfq was incapable of achieving the I/O > rates of deadline, no matter how it was tuned. Investigation, and insight > from Vivek (mostly the latter), led to identifying that we were still > idling for the last queue in the service tree. > > Modifying cfq_should_idle to not idle when slice_idle is set to zero got > us much closer to the performance of deadline for this workload. I have > one follow-on patch that gets us on-par with deadline, but I think this > patch stands alone. > > Comments, as always, are appreciated. This looks good. -- Jens Axboe