From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753175Ab1IMHx0 (ORCPT ); Tue, 13 Sep 2011 03:53:26 -0400 Received: from mail-yw0-f46.google.com ([209.85.213.46]:55852 "EHLO mail-yw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751670Ab1IMHxZ (ORCPT ); Tue, 13 Sep 2011 03:53:25 -0400 Date: Tue, 13 Sep 2011 16:46:53 +0900 From: Tejun Heo To: Shaohua Li Cc: lkml , Jens Axboe , Vivek Goyal Subject: Re: [RFC]block: don't mark flush request as SOFTBARRIER Message-ID: <20110913074653.GC11397@mtj.dyndns.org> References: <1315445394.29510.71.camel@sli10-conroe> <20110911025128.GM29319@htj.dyndns.org> <1315875841.29510.80.camel@sli10-conroe> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1315875841.29510.80.camel@sli10-conroe> 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, Sep 13, 2011 at 09:04:01AM +0800, Shaohua Li wrote: > we do the flush first and then dispatch the data. The flush is > already delayed a lot, so if latency is a problem, we already saw > it. I don't necessarily agree with the above. We don't induce any extra latency for flushes which don't overlap. > Why not just remove SOFTBARRIER and use elv_dispatch_sort() for > flush data so drive can better arrange requests? Maybe, I don't know. Elevator sorting on writes is likely to be much less important to begin with. Combined with the fact that sorting flush data would require more writes to be flushed by the following flush, I don't think it would be clear which way would be better. If it can be shown that sorting flush data is better, why not? Thanks. -- tejun