Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755420AbYKJNxj (ORCPT ); Mon, 10 Nov 2008 08:53:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754950AbYKJNxa (ORCPT ); Mon, 10 Nov 2008 08:53:30 -0500 Received: from mx2.redhat.com ([66.187.237.31]:57785 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754913AbYKJNxa (ORCPT ); Mon, 10 Nov 2008 08:53:30 -0500 From: Jeff Moyer To: Jens Axboe Cc: "Vitaly V. Bursov" , linux-kernel@vger.kernel.org Subject: Re: Slow file transfer speeds with CFQ IO scheduler in some cases References: <4917263D.2090904@telenet.dn.ua> <20081110104423.GA26778@kernel.dk> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Mon, 10 Nov 2008 08:51:18 -0500 In-Reply-To: <20081110104423.GA26778@kernel.dk> (Jens Axboe's message of "Mon, 10 Nov 2008 11:44:24 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.60 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1463 Lines: 38 Jens Axboe writes: > On Sun, Nov 09 2008, Vitaly V. Bursov wrote: >> Hello, >> >> I'm building small server system with openvz kernel and have ran into >> some IO performance problems. Reading a single file via NFS delivers >> around 9 MB/s over gigabit network, but while reading, say, 2 different >> or same file 2 times at the same time I get >60MB/s. >> >> Changing IO scheduler to deadline or anticipatory fixes problem. >> >> Tested kernels: >> OpenVZ RHEL5 028stab059.3 (9 MB/s with HZ=100, 20MB/s with HZ=1000 >> fast local reads) >> Vanilla 2.6.27.5 (40 MB/s with HZ=100, slow local reads) >> >> Vanilla performs better in worst case but I believe 40 is still low >> concerning test results below. > > Can you check with this patch applied? > > http://bugzilla.kernel.org/attachment.cgi?id=18473&action=view Funny, I was going to ask the same question. ;) The reason Jens wants you to try this patch is that nfsd may be farming off the I/O requests to different threads which are then performing interleaved I/O. The above patch tries to detect this and allow cooperating processes to get disk time instead of waiting for the idle timeout. Cheers, Jeff -- 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/