From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755443AbbIBQQz (ORCPT ); Wed, 2 Sep 2015 12:16:55 -0400 Received: from mail-am1on0100.outbound.protection.outlook.com ([157.56.112.100]:2080 "EHLO emea01-am1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752619AbbIBQQx (ORCPT ); Wed, 2 Sep 2015 12:16:53 -0400 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=cmetcalf@ezchip.com; linux.vnet.ibm.com; dkim=none (message not signed) header.d=none;linux.vnet.ibm.com; dmarc=none action=none header.from=ezchip.com; Subject: Re: [PATCH 1/2] nohz: Affine unpinned timers to housekeepers To: Mike Galbraith , Frederic Weisbecker References: <1441119060-2230-1-git-send-email-fweisbec@gmail.com> <1441119060-2230-2-git-send-email-fweisbec@gmail.com> <20150901204723.GA6590@lerouge> <1441186689.4163.11.camel@gmail.com> CC: "Jiang, Yunhong" , Ingo Molnar , Peter Zijlstra , LKML , Vatika Harlalka , Thomas Gleixner , Preeti U Murthy , Christoph Lameter , "Paul E . McKenney" From: Chris Metcalf Message-ID: <55E720DE.8020100@ezchip.com> Date: Wed, 2 Sep 2015 12:16:30 -0400 User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <1441186689.4163.11.camel@gmail.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [12.216.194.146] X-ClientProxiedBy: DM3PR14CA0023.namprd14.prod.outlook.com (25.164.193.161) To HE1PR02MB0778.eurprd02.prod.outlook.com (25.161.118.142) X-Microsoft-Exchange-Diagnostics: 1;HE1PR02MB0778;2:lSTtei3nG6dDFm05OEfp1yViBNyk2AdknInguBP2agp2UiljgbQHlZq9yh4rbL6zPGtvaDopTIhKO5wn8XE8zPOCAkftgV8wJPgxfw3ossL/fiu+97jYRd+pic5SaYyD1tn25clpSaNAeuUSje4UH2cRKkeyjP6nOCAqrmj0ipc=;3:VLTu+dc/oZ/hjY/5DwZophgDPge80LKbq/4n2HDgTOUzX0dffGNYek5scr6MgtIXsf5JAD7Zxk1wwvI7oeJsZlIb9WdpQZTez75Y+2Um4zJmtfLAUVkKGya9xomzGWdZRqX+Rfy95nfhUqZ/Skxk9Q==;25:v1IhKv3HgQ/QeVWdvxo9Cw9Lt6XvdtBjs2n3u2NsQ3qecd/U2dDJ8tuyobCoO1zQiSaeMv+T8RQpbL2wE7TwFvD3JNym8vfWpHmaHs9pX7c8g6/DIt6DJMTsHb9w6A3Zs7cBeuOR+wRF+Ahi+xbGoiQx5o/PYHITpxC/Jg1xRpxJ5kzVLz+AASXC8kk9paD5Fj5H9f+S6PDMJ8bVS3NK/ScQs3H4AA54E3dzmMS/oRdcAgG5nNtpsJfC5UVjeuW2VhGLBYWSLVW2pXjPXe97yg==;20:zyoMn/0WbZwMH9vWqkGm2fKH65fzCHHjwC1kKlSJop8ABgCEh/uOJVtCWTJztsAlnR98NHp27ATZCVx90wwEFD1pZiqVwGGUZHpXV51jfkb9Nd0Tsn92UqlaJdM0Br9GKAG5jP5b1v+DmSRzBF8vwVjgPdEQ/GS9JCwBV3fLHQY= X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:HE1PR02MB0778;UriScan:;BCL:0;PCL:0;RULEID:;SRVR:HE1PR02MB0793; 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Yeah, the problem seems to be folks who use it as a kind of "hey, maybe this gives me some optimization boost somewhere" kind of setting. Did we ever hear actual use cases for people who benefited from running nohz_full on cpus with an active scheduler, i.e. no isolcpus for that core? I find it hard to imagine, but, maybe...? If we don't have such use cases, what should we do here? I'm slightly sympathetic to these folks who are going "Gee, my machine suddenly got way slower", but only in the same sense as people who shoot themselves in the foot and then say "Gee, my foot is bleeding". But maybe I'm being too hard core :-) -- Chris Metcalf, EZChip Semiconductor http://www.ezchip.com