From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754386AbbDHPWN (ORCPT ); Wed, 8 Apr 2015 11:22:13 -0400 Received: from mail-am1on0061.outbound.protection.outlook.com ([157.56.112.61]:45089 "EHLO emea01-am1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753267AbbDHPWK (ORCPT ); Wed, 8 Apr 2015 11:22:10 -0400 Message-ID: <55254794.4070503@ezchip.com> Date: Wed, 8 Apr 2015 11:21:56 -0400 From: Chris Metcalf User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Peter Zijlstra CC: Frederic Weisbecker , "Paul E. McKenney" , "Rafael J. Wysocki" , Martin Schwidefsky , Ingo Molnar , Subject: Re: [PATCH v2 2/2] nohz: make nohz_full imply isolcpus References: <5522BF1E.2040606@ezchip.com> <1428344205-27678-1-git-send-email-cmetcalf@ezchip.com> <1428344205-27678-2-git-send-email-cmetcalf@ezchip.com> <20150408094114.GX23123@twins.programming.kicks-ass.net> <5525357B.2080205@ezchip.com> <20150408142641.GG5029@twins.programming.kicks-ass.net> In-Reply-To: <20150408142641.GG5029@twins.programming.kicks-ass.net> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [12.216.194.146] X-ClientProxiedBy: BN1PR12CA0041.namprd12.prod.outlook.com (25.160.77.51) To VI1PR02MB0784.eurprd02.prod.outlook.com (25.162.14.146) Authentication-Results: vger.kernel.org; dkim=none (message not signed) header.d=none; X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:VI1PR02MB0784; X-Forefront-Antispam-Report: BMV:1;SFV:NSPM;SFS:(10009020)(6049001)(6009001)(377454003)(51704005)(479174004)(54534003)(24454002)(87976001)(50466002)(62966003)(86362001)(23746002)(47776003)(77156002)(64126003)(83506001)(92566002)(2950100001)(122386002)(19580405001)(15975445007)(87266999)(76176999)(54356999)(36756003)(50986999)(46102003)(59896002)(117636001)(65816999)(65956001)(110136001)(19580395003)(66066001)(42186005)(40100003)(77096005)(62816006)(18886065003);DIR:OUT;SFP:1101;SCL:1;SRVR:VI1PR02MB0784;H:[10.7.0.41];FPR:;SPF:None;MLV:sfv;LANG:en; X-Microsoft-Antispam-PRVS: X-Exchange-Antispam-Report-Test: UriScan:; X-Exchange-Antispam-Report-CFA-Test: BCL:0;PCL:0;RULEID:(601004)(5002010)(5005006);SRVR:VI1PR02MB0784;BCL:0;PCL:0;RULEID:;SRVR:VI1PR02MB0784; X-Forefront-PRVS: 0540846A1D X-OriginatorOrg: ezchip.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Apr 2015 15:22:06.3716 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR02MB0784 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/08/2015 10:26 AM, Peter Zijlstra wrote: > On Wed, Apr 08, 2015 at 10:04:43AM -0400, Chris Metcalf wrote: >> On 04/08/2015 05:41 AM, Peter Zijlstra wrote: >>> On Mon, Apr 06, 2015 at 02:16:45PM -0400, cmetcalf@ezchip.com wrote: >>>> From: Chris Metcalf >>>> >>>> It's not clear that nohz_full is useful without isolcpus also >>>> set, since otherwise the scheduler has to run periodically to >>>> try to determine whether to steal work from other cores. >>> So the Changelog and the patch don't seem to agree with one another. >>> >>> The Changelog states that nohz_full should depend on isolcpus. >> The git commit message says "make nohz_full imply isolcpus". >> That's consistent with the code. > Well, but then the Changelog doesn't make any sense. Apparently the body of the commit message isn't as clear as it might be :-) It does say the same thing, though, basically that if nohz_full DOESN'T imply isolcpus, that's a bad thing. I'm happy to reword the text to avoid the double negative and say: nohz_full is only useful with isolcpus also set, since otherwise the scheduler has to run periodically to try to determine whether to steal work from other cores. Frederic, do you want me to respin the patch, or can you just update the text of the commit message as above? -- Chris Metcalf, EZChip Semiconductor http://www.ezchip.com