From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752769Ab2AOWqD (ORCPT ); Sun, 15 Jan 2012 17:46:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47347 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752513Ab2AOWpi (ORCPT ); Sun, 15 Jan 2012 17:45:38 -0500 Date: Sun, 15 Jan 2012 17:45:32 -0500 From: Vivek Goyal To: Shaohua Li Cc: Dave Chinner , linux-kernel@vger.kernel.org, axboe@kernel.dk, jmoyer@redhat.com Subject: Re: [RFC 0/3]block: An IOPS based ioscheduler Message-ID: <20120115224532.GD3174@redhat.com> References: <20120104065337.230911609@sli10-conroe.sh.intel.com> <20120104071931.GB17026@dastard> <1325746241.22361.503.camel@sli10-conroe> <1325826750.22361.533.camel@sli10-conroe> <20120108221615.GA4198@dastard> <1326071375.22361.543.camel@sli10-conroe> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1326071375.22361.543.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 On Mon, Jan 09, 2012 at 09:09:35AM +0800, Shaohua Li wrote: [..] > > You need to present raw numbers and give us some idea of how close > > those numbers are to raw hardware capability for us to have any idea > > what improvements these numbers actually demonstrate. > Yes, your guess is right. The hardware has limitation. 12 SSD exceeds > the jbod capability, for both throughput and IOPS, that's why only > read/write mixed workload impacts. I'll use less SSD in later tests, > which will demonstrate the performance better. I'll report both raw > numbers and fiops/cfq numbers later. If fiops number are better please explain why those numbers are better. If you cut down on idling, it is obivious that you will get higher throughput on these flash devices. CFQ does disable queue idling for non rotational NCQ devices. If higher throughput is due to driving deeper queue depths, then CFQ can do that too just by changing quantum and disabling idling. So I really don't understand that what are you doing fundamentally different in FIOPS ioscheduler. The only thing I can think of more accurate accounting per queue in terms of number of IOs instead of time. Which can just serve to improve fairness a bit for certain workloads. In practice, I think it might not matter much. Thanks Vivek