From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Thu, 21 Aug 2008 04:52:05 -0700 (PDT) Received: from cuda.sgi.com ([192.48.176.15]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m7LBq06H008208 for ; Thu, 21 Aug 2008 04:52:01 -0700 Received: from mail.parisc-linux.org (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 164DC1A1F5C3 for ; Thu, 21 Aug 2008 04:53:21 -0700 (PDT) Received: from mail.parisc-linux.org (palinux.external.hp.com [192.25.206.14]) by cuda.sgi.com with ESMTP id pXIeVyabms5p6uo0 for ; Thu, 21 Aug 2008 04:53:21 -0700 (PDT) Date: Thu, 21 Aug 2008 05:53:10 -0600 From: Matthew Wilcox Subject: Re: XFS vs Elevators (was Re: [PATCH RFC] nilfs2: continuous snapshotting file system) Message-ID: <20080821115310.GP8318@parisc-linux.org> References: <20080820004326.519405a2.akpm@linux-foundation.org> <200808201613.AA00212@capsicum.lab.ntt.co.jp> <20080820143916.1a7eddab.akpm@linux-foundation.org> <20080821021259.GA5706@disturbed> <20080821051508.GB5706@disturbed> <20080821060418.GC5706@disturbed> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080821060418.GC5706@disturbed> Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Szabolcs Szakacsits , Andrew Morton , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, xfs@oss.sgi.com On Thu, Aug 21, 2008 at 04:04:18PM +1000, Dave Chinner wrote: > One thing I just found out - my old *laptop* is 4-5x faster than the > 10krpm scsi disk behind an old cciss raid controller. I'm wondering > if the long delays in dispatch is caused by an interaction with CTQ > but I can't change it on the cciss raid controllers. Are you using > ctq/ncq on your machine? If so, can you reduce the depth to > something less than 4 and see what difference that makes? I don't think that's going to make a difference when using CFQ. I did some tests that showed that CFQ would never issue more than one IO at a time to a drive. This was using sixteen userspace threads, each doing a 4k direct I/O to the same location. When using noop, I would get 70k IOPS and when using CFQ I'd get around 40k IOPS. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step."