From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755858Ab1LMWS5 (ORCPT ); Tue, 13 Dec 2011 17:18:57 -0500 Received: from mx1.redhat.com ([209.132.183.28]:10876 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752757Ab1LMWSx (ORCPT ); Tue, 13 Dec 2011 17:18:53 -0500 From: Jeff Moyer To: Dave Kleikamp Cc: linux-aio@kvack.org, linux-kernel@vger.kernel.org, Chris Mason , Jens Axboe , Andi Kleen Subject: Re: [PATCH] AIO: Don't plug the I/O queue in do_io_submit() References: <4EE7C74D.1020306@oracle.com> 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: Tue, 13 Dec 2011 17:18:41 -0500 In-Reply-To: <4EE7C74D.1020306@oracle.com> (Dave Kleikamp's message of "Tue, 13 Dec 2011 15:44:45 -0600") 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 Dave Kleikamp writes: > Asynchronous I/O latency to a solid-state disk greatly increased > between the 2.6.32 and 3.0 kernels. By removing the plug from > do_io_submit(), we observed a 34% improvement in the I/O latency. > > Unfortunately, at this level, we don't know if the request is to > a rotating disk or not. I'm guessing I know the answer to this, but what workload were you testing, and can you provide more concrete evidence than "latency greatly increased?" Also, have you tested the effects this has when using traditional storage for whatever your workload is? I don't feel comfortable essentially reverting a performance patch without knowing the entire picture. I will certainly do some testing on my end, too. Cheers, Jeff