Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754246Ab1FJJUs (ORCPT ); Fri, 10 Jun 2011 05:20:48 -0400 Received: from 0122700014.0.fullrate.dk ([95.166.99.235]:37799 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750774Ab1FJJUp (ORCPT ); Fri, 10 Jun 2011 05:20:45 -0400 Message-ID: <4DF1E1EB.8010808@kernel.dk> Date: Fri, 10 Jun 2011 11:20:43 +0200 From: Jens Axboe MIME-Version: 1.0 To: Vivek Goyal CC: Shaohua Li , Tao Ma , linux-kernel@vger.kernel.org Subject: Re: CFQ: async queue blocks the whole system References: <1307616577-6101-1-git-send-email-tm@tao.ma> <20110609141451.GD29913@redhat.com> <4DF0DD0F.8090407@tao.ma> <20110609153738.GF29913@redhat.com> <20110610091747.GC4183@redhat.com> In-Reply-To: <20110610091747.GC4183@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 Content-Length: 1023 Lines: 26 On 2011-06-10 11:17, Vivek Goyal wrote: > On Fri, Jun 10, 2011 at 09:19:12AM +0800, Shaohua Li wrote: > > [..] >>> If there is no major advantage of draining sync requests before async >>> is dispatched, I think this should be an easy fix. >> I thought this is to avoid sync latency if we switch from an async >> queue to sync queue later. > > Is it about the sync request latency which has already been dispatched? I > really wish that driver and disk should do some prioritazation for reads > here and CFQ does not have to jump through hoops like drain sync requests > before async requests are dispatched. That would never work. Are you suggesting putting that logic in all drivers? Or relying on hardware to get the fairness right? Not going to happen. -- Jens Axboe -- 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/