From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756949AbYDQHK3 (ORCPT ); Thu, 17 Apr 2008 03:10:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753991AbYDQHKQ (ORCPT ); Thu, 17 Apr 2008 03:10:16 -0400 Received: from brick.kernel.dk ([87.55.233.238]:21428 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753628AbYDQHKP (ORCPT ); Thu, 17 Apr 2008 03:10:15 -0400 Date: Thu, 17 Apr 2008 09:10:12 +0200 From: Jens Axboe To: Paolo Valente Cc: Pavel Machek , linux-kernel@vger.kernel.org Subject: Re: [RESEND][RFC] BFQ I/O Scheduler Message-ID: <20080417071012.GP12774@kernel.dk> References: <20080401152903.GB34860@gandalf.sssup.it> <20080416184441.GA3923@ucw.cz> <4806EACB.7040408@unimore.it> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4806EACB.7040408@unimore.it> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 17 2008, Paolo Valente wrote: > Pavel Machek ha scritto: > > > >>In the first type of tests, to achieve a higher throughput than CFQ > >>(with the default 100 ms time slice), the maximum budget for BFQ > >>had to be set to at least 4k sectors. Using the same value for the > >> > > > >Hmm, 4k sectors is ~40 seconds worst case, no? That's quite long... > > > Actually, in the worst case among our tests, the aggregate throughput > with 4k sectors was ~ 20 MB/s, hence the time for 4k sectors ~ 4k * 512 > / 20M = 100 ms. That's not worse case, it is pretty close to BEST case. Worst case is 4k of sectors, with each being a 512b IO and causing a full stroke seek. For that type of workload, even a modern sata hard drive will be doing 500kb/sec or less. That's rougly a thousand sectors per seconds, so ~4 seconds worst case for 4k sectors. -- Jens Axboe