Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753678Ab0GZNRs (ORCPT ); Mon, 26 Jul 2010 09:17:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41930 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750913Ab0GZNRr (ORCPT ); Mon, 26 Jul 2010 09:17:47 -0400 From: Jeff Moyer To: Jens Axboe Cc: Heinz Diehl , linux-kernel@vger.kernel.org Subject: Re: [PATCH] cfq-iosched: don't allow aliased requests to starve others References: <20100724080459.GA6500@fancy-poultry.org> <4C4ABA55.2000204@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, 26 Jul 2010 09:17:38 -0400 In-Reply-To: <4C4ABA55.2000204@kernel.dk> (Jens Axboe's message of "Sat, 24 Jul 2010 12:03:01 +0200") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (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: 1345 Lines: 34 Jens Axboe writes: > On 07/24/2010 10:04 AM, Heinz Diehl wrote: >> On 14.07.2010, Jeff Moyer wrote: >> >>> Comments, as always, are welcome. >> >> This patch, applied to 2.6.35-rc6, increases desktop interactivity >> _NOTICEABLY_ on my quadcore machine, and the machine stays rock-stable. >> I have now tested this patch with the latest 2.6.35-rc kernels over >> 1 week. >> >> Unfortunately, I can't provide some testing results which makes this >> statement more objective, but I'll do some synthetic testing in the next >> days. > > It is extremely unlikely that this patch will have any impact on > "normal" workloads. To even hit a code path where it would make a > difference, you would need to use O_DIRECT IO, otherwise you cannot have > aliases in the IO scheduler. I agree that it shouldn't help normal workloads at all. I do think there is one other case where you can get aliases: doing I/O both through the file system and the underlying device. However, that's obviously a bad idea (and maybe open_bdev_exclusive will keep that from happening?). 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/