Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760057AbYHULx1 (ORCPT ); Thu, 21 Aug 2008 07:53:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759974AbYHULxN (ORCPT ); Thu, 21 Aug 2008 07:53:13 -0400 Received: from palinux.external.hp.com ([192.25.206.14]:40302 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758869AbYHULxM (ORCPT ); Thu, 21 Aug 2008 07:53:12 -0400 Date: Thu, 21 Aug 2008 05:53:10 -0600 From: Matthew Wilcox To: Szabolcs Szakacsits , Andrew Morton , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, xfs@oss.sgi.com 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> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1266 Lines: 24 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." -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/