From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753990Ab1FJJRw (ORCPT ); Fri, 10 Jun 2011 05:17:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:62330 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750774Ab1FJJRv (ORCPT ); Fri, 10 Jun 2011 05:17:51 -0400 Date: Fri, 10 Jun 2011 05:17:47 -0400 From: Vivek Goyal To: Shaohua Li Cc: Tao Ma , linux-kernel@vger.kernel.org, Jens Axboe Subject: Re: CFQ: async queue blocks the whole system Message-ID: <20110610091747.GC4183@redhat.com> References: <1307616577-6101-1-git-send-email-tm@tao.ma> <20110609141451.GD29913@redhat.com> <4DF0DD0F.8090407@tao.ma> <20110609153738.GF29913@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 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. Thanks Vivek