Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755157Ab1BJCpb (ORCPT ); Wed, 9 Feb 2011 21:45:31 -0500 Received: from smtp-out.google.com ([74.125.121.67]:55987 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754721Ab1BJCpa (ORCPT ); Wed, 9 Feb 2011 21:45:30 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=YRyG1G8nzXhyuSea8LwMOytCINIW8KR0ga9Diks1n91pJNC6SMby9OeHHlKw7bamgX tJBzYuHQZRSgG+7MEWbQ== MIME-Version: 1.0 In-Reply-To: <20110210020946.GA27040@redhat.com> References: <20110210013211.21573.69260.stgit@neat.mtv.corp.google.com> <20110210020946.GA27040@redhat.com> Date: Wed, 9 Feb 2011 18:45:25 -0800 Message-ID: Subject: Re: [PATCH] Avoid preferential treatment of groups that aren't backlogged From: Chad Talbott To: Vivek Goyal Cc: jaxboe@fusionio.com, guijianfeng@cn.fujitsu.com, mrubin@google.com, teravest@google.com, jmoyer@redhat.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2157 Lines: 47 On Wed, Feb 9, 2011 at 6:09 PM, Vivek Goyal wrote: > In upstream code once a group gets backlogged we put it at the end > and not at the beginning of the tree. (I am wondering are you looking > at the google internal code :-)) > > So I don't think that issue of a low weight group getting more disk > time than its fair share is present in upstream kernels. You've caught me re-using a commit description. :) Here's an example of the kind of tests that fail without this patch (run via the test that Justin and Akshay have posted): 15:35:35 INFO ----- Running experiment 14: 950 rdrand, 50 rdrand.delay10 15:35:55 INFO Experiment completed in 20.4 seconds 15:35:55 INFO experiment 14 achieved DTFs: 886, 113 15:35:55 INFO experiment 14 FAILED: max observed error is 64, allowed is 50 15:35:55 INFO ----- Running experiment 15: 950 rdrand, 50 rdrand.delay50 15:36:16 INFO Experiment completed in 20.5 seconds 15:36:16 INFO experiment 15 achieved DTFs: 891, 108 15:36:16 INFO experiment 15 FAILED: max observed error is 59, allowed is 50 Since this is Jens' unmodified tree, I've had to change BLKIO_WEIGHT_MIN to 10 to allow this test to proceed. We typically run many jobs with small weights, and achieve the requested isolation: see below results with this patch: 14:59:17 INFO ----- Running experiment 14: 950 rdrand, 50 rdrand.delay10 14:59:36 INFO Experiment completed in 19.0 seconds 14:59:36 INFO experiment 14 achieved DTFs: 947, 52 14:59:36 INFO experiment 14 PASSED: max observed error is 3, allowed is 50 14:59:36 INFO ----- Running experiment 15: 950 rdrand, 50 rdrand.delay50 14:59:55 INFO Experiment completed in 18.5 seconds 14:59:55 INFO experiment 15 achieved DTFs: 944, 55 14:59:55 INFO experiment 15 PASSED: max observed error is 6, allowed is 50 As you can see, it's with seeky workloads that come and go from the service tree where this patch is required. Chad -- 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/