From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756096Ab3G3OBM (ORCPT ); Tue, 30 Jul 2013 10:01:12 -0400 Received: from mail-gh0-f173.google.com ([209.85.160.173]:47916 "EHLO mail-gh0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755385Ab3G3OBK (ORCPT ); Tue, 30 Jul 2013 10:01:10 -0400 Date: Tue, 30 Jul 2013 10:01:06 -0400 From: Tejun Heo To: Shaohua Li Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, neilb@suse.de, djbw@fb.com Subject: Re: [patch 3/3] raid5: only wakeup necessary threads Message-ID: <20130730140106.GE12016@htj.dyndns.org> References: <20130730055207.698660010@kernel.org> <20130730055425.056034691@kernel.org> <20130730124655.GB2599@htj.dyndns.org> <20130730132414.GB30352@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130730132414.GB30352@kernel.org> 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 Hello, Shaohua. On Tue, Jul 30, 2013 at 09:24:14PM +0800, Shaohua Li wrote: > In the raid5 case, it's very hard to keep the order the bios passed in, because > we need read some disks, calculate parity, and write some disks, the timing > could break any kind of order. Besides the workqueue handles 8 stripes one > time, so I suppose this keeps some order if there is. Of course, it can't be absolute but still keeping the relative ordering and temporal locality (ie. issue IOs in order once the XOR calculation of the whole source bio is done rather than issuing as each block completes calculation) would help quite a bit. Thanks. -- tejun