From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752553AbcHTISX (ORCPT ); Sat, 20 Aug 2016 04:18:23 -0400 Received: from mail-ve1eur01on0074.outbound.protection.outlook.com ([104.47.1.74]:28144 "EHLO EUR01-VE1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751175AbcHTIST (ORCPT ); Sat, 20 Aug 2016 04:18:19 -0400 X-Greylist: delayed 3618 seconds by postgrey-1.27 at vger.kernel.org; Sat, 20 Aug 2016 04:18:18 EDT Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=cmetcalf@mellanox.com; Subject: Re: [PATCH] Fix /proc/stat freezes (was [PATCH v15] "task_isolation" mode) To: Christoph Lameter , Frederic Weisbecker References: <1471382376-5443-1-git-send-email-cmetcalf@mellanox.com> CC: Gilad Ben Yossef , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Andrew Morton , "Rik van Riel" , Tejun Heo , Thomas Gleixner , "Paul E. McKenney" , Viresh Kumar , Catalin Marinas , Will Deacon , Andy Lutomirski , Daniel Lezcano , "Francis Giraldeau" , , , From: Chris Metcalf Message-ID: <427287c8-3fa8-093c-29ac-d492a88a6337@mellanox.com> Date: Fri, 19 Aug 2016 21:42:19 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [148.74.104.201] X-ClientProxiedBy: CY1PR0801CA0025.namprd08.prod.outlook.com (10.163.136.163) To DB6PR0501MB2757.eurprd05.prod.outlook.com (10.172.226.9) X-MS-Office365-Filtering-Correlation-Id: 2e51696f-51c4-4c8d-bbad-08d3c89b47d6 X-Microsoft-Exchange-Diagnostics: 1;DB6PR0501MB2757;2:IWdEgSzDFfbhoX0OhZMlRofXmjAXF2avgobPxhWPUligzoSs/EbfaSu+EvDiYlRrZSCUnuRlz+YaiVBIMvKqAi1Riod2zaEoPcL+5XSHMbhjqinSakx9Cx42SqPeN0YHj1s8HheoPXhXOk8+YF32Av8+k+c5lFnjX7DFQ39D5EUhIRbWkrSrshb88wO98ENz;3:IwD/XM2+SFmyGTFpCSAnzrvM3Bd4hNkPChPrgrLPcyTLycj4Go149Hn/qaMk1yavU96qVQAwl5miYIxZGS/uij+wIto07kwfwCHDp68fTDJHzfMGqBJDjCJhqKJW0c69 X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:DB6PR0501MB2757; X-Microsoft-Exchange-Diagnostics: 1;DB6PR0501MB2757;25: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 X-Microsoft-Exchange-Diagnostics: 1;DB6PR0501MB2757;31:H+j6vb6lA9qF6hqk9RHrmWRvxh0ZRDUV53j7MJH2AySgOOc1X7vvZdlNAL9Y3sTnd1SZC5IgUmr3TLSTdxZ6iiwTJ8/ZMgu43nj1EkJrXs3R0bzSTuYmoTsiRxkUVCeMUn1ryFknIecYNFVr54zkLyO+Szerg5+5eLyW/Hjg8Sr8YHRSskPS346MDrLaoO2nqlx8D4LXU0CDf2tbDoBRh4oGD4EU0eNu1sN+7o8JKqk=;20: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 X-Microsoft-Antispam-PRVS: X-Exchange-Antispam-Report-Test: UriScan:(171992500451332); X-Exchange-Antispam-Report-CFA-Test: BCL:0;PCL:0;RULEID:(6040176)(601004)(2401047)(5005006)(8121501046)(3002001)(10201501046)(6055026);SRVR:DB6PR0501MB2757;BCL:0;PCL:0;RULEID:;SRVR:DB6PR0501MB2757; X-Microsoft-Exchange-Diagnostics: 1;DB6PR0501MB2757;4:YJMdlTRqFs1csU74X2vbY2Vqi4o+vtP0KCZ5GFhArbshxg7gw5NYYjzdjQ2lvEZjAeC2b3WpUyVI57l623t+VBce12cjTC0d5z+IJeXG8EZ5pq1DqD4ET42IYjUG2WBUfUv521jpBpH/9WzFD1Dv8NLpwdsRNGpCOOdBkkCmtcQx/zfvFCt2KjVCoTPynVdxGHrKjSGALnEPF63jPIq96xKnsh+oFz/PQL90etMqTjWUHiXZ96CpSQ3neprvgDLa/NhstE33Gmwy7vzN4eD7UfNPZZWwefc1Of32qMVh85j63dgkp8HuBzib9Nsw5kRq54l/RuVf+r2shI2L5BLzJ8+BbNPswemq4Td2IYFPzpt0me0N3Gy0ET6b+KJBA+Th6Hq4Z7bhj1S9y0cXWOEm5tsXgaYsRSz6usEJ7PdOq2nEhA/jOjo8ncnEFePztz9KRDmkNNPZiXD3UyzKCY1HAg== X-Forefront-PRVS: 0040126723 X-Forefront-Antispam-Report: SFV:NSPM;SFS:(10009020)(4630300001)(6009001)(6049001)(7916002)(189002)(377454003)(24454002)(199003)(106356001)(83506001)(50466002)(23746002)(230700001)(47776003)(31686004)(65806001)(42186005)(76176999)(68736007)(97736004)(586003)(189998001)(19580395003)(64126003)(7846002)(33646002)(50986999)(101416001)(4001350100001)(7416002)(81156014)(2906002)(36756003)(117156001)(81166006)(7736002)(2950100001)(86362001)(6116002)(3846002)(65956001)(5001770100001)(92566002)(105586002)(66066001)(54356999)(8676002)(31696002)(4326007)(77096005)(305945005)(15975445007)(5660300001)(65826006)(18886065003);DIR:OUT;SFP:1101;SCL:1;SRVR:DB6PR0501MB2757;H:[192.168.1.62];FPR:;SPF:None;PTR:InfoNoRecords;MX:1;A:1;LANG:en; X-Microsoft-Exchange-Diagnostics: =?Windows-1252?Q?1;DB6PR0501MB2757;23:OEFZxoIWll1xyssOpX3fPMlPRN+rxan7Bga?= =?Windows-1252?Q?jYou6G6cJG+4oBmy/7fCiK01S9SEEwhwqpisTXkltOKVBpUqiXMfdowG?= =?Windows-1252?Q?ZnPOLY4n7rB9qsXx8tI/DRYKAT7oOOGB1Q63BzRYwrIJEecm33x07O73?= =?Windows-1252?Q?ECUsbkG0YTyrwRkTcFBQVjfGRnqdJqD1bkyq11ct0IJPVj0SVY1TzNho?= =?Windows-1252?Q?YdwCVZz4xBZlLL9eaZ8ga8Ua9IVlIsuYtgCFBR4xZg1M5Gcr1na2EDh4?= =?Windows-1252?Q?Aw9r0qc2e/wF0UPZxsbg4KhIvw29q7NDQdhhiMMA4RFXfQiiATs6MjoT?= =?Windows-1252?Q?PCtUp1HNkEvuV7FHjYI3P/UqNe4IlcM1ptUuvBG96qya1Ytn9orG1rkH?= =?Windows-1252?Q?N376dvbfj3mEUH+y9cnkztvybCYoRS+UuLSRrsrMRKG0qKdzcTSMoGtD?= =?Windows-1252?Q?JeFkcKXeVBnk1I3jN2Eri1JYtiaNfoz5LQXPmbQpWu+WGVuPLcdI7EmK?= =?Windows-1252?Q?UxVCUIBy6EYciqqa6pL5tDwlOnw/DEawpfYtuD6690ASVXuiKxr+31of?= =?Windows-1252?Q?htaeke0KyxRneGyjkIxEHHfWiQYal5oUFKYH5Y/vRmcaa5MynXi4tOIn?= =?Windows-1252?Q?sUcaWonAz9PJ5QVTDFv8pC8QuJbqAHWJkU8HQhX6YbroZK5Zo1Wp6hJw?= =?Windows-1252?Q?Q8UrF8TN7FjbneMabei5fiUB3xc4SYREpyTQFp94yPOrV6x4nl9nJOmf?= =?Windows-1252?Q?GayYM/twJ6EB9h3fG1ic8G/uHkU3wNGnKdVft+Mv7v2Iz+ViZ68HnHPu?= =?Windows-1252?Q?RgsOeRD70n1mLVhtR3t8n3n4gRObuSaTL8kzyed5NFBSmE8oNubD5Z+R?= =?Windows-1252?Q?wI8xRXOVPOvWLA3TQpZlKAhcWfXX9wU6o32uJrJZD1G84e0fVaP9OjZ/?= =?Windows-1252?Q?qqd9h124wArPNMT03/CK/33gx4sHzVFknhKydvhMSARn4IMMySmgr1u7?= =?Windows-1252?Q?OOI/HwVvgH2vWnmL8Z5CDbi3LwOpG4fqi3JDWn9sL7p/30WtdxhijWKM?= =?Windows-1252?Q?U0xqKOUOfiAvxUyxu6nsiZIR76jm9nPt2eKDiUzbvvTdHGOG5O7BqmH7?= =?Windows-1252?Q?dFpUvQGiAvOL6qTb37FQ+xp/OrdcrKRzzVsJsGkIhrsUyUBdfhaZrwxL?= =?Windows-1252?Q?SrM7yRck1sbzeQYfRdp+GYHRn2bwiC9o/tgekFqZ5mqgC5NQ23TRrgBD?= =?Windows-1252?Q?jyGfbVnEDouFurFqTYzv77ZBm01PFNPsjprJFvja6R1FjCVmlrSoDRQt?= =?Windows-1252?Q?zXywDj0t7PwmoqnwYmB65Uwz91TOfom+o0rOATxH7Hkgc8zCoM3g2wjW?= =?Windows-1252?Q?Zr9V4QCntqgHXz9qFqkgHH6WPTuGa8oS1+5AkH5Fs9MtF14KOfcUQhAz?= =?Windows-1252?Q?0uZ7LbvCM70AEnrlPmT+220+NVBmGqP/cQWXY5glPVHKmPx98z3gY7jX?= =?Windows-1252?Q?f1vTcgrQ=3D?= X-Microsoft-Exchange-Diagnostics: 1;DB6PR0501MB2757;6:Z7asO9DDNbbJZ1GbU98DmCtSUIsKjrrtIaDffgeymhhWIbTjH5135vZOmfpb58F45sD7kpa/O5bv8RsS2y9uek5mseO3pFQSbJWjKU7zChsE9vrM8oaVmh7B92W9KOL1g+lNFOnSBUQ6HQJBF2ZvcJZp/YalGk1dklcjmj9pfF2ZheO/2Wruy4bm3vFKhBl7ZQwF6iGRWLq1cmWrEUGTs9DiIS2qJuwIisWveplmc1Z7wV/oqhT5cHoxVqDcjcyroDiJ5oAjlly6XeLwL9Y2v0wSRVrtpraRrSlA+kA2La0uJuhMnQIUuVpMDnWqOD+bgYQsEsFxLsmcBZYcO2oSww==;5:mbbiEdQCi5DRRpImurbglCmbiYJrxKLJ/x3WEl/ZHMu3uAmjDYyzrEuannYJ/MTBFc0uyCuhiu3zHZg29TkAcMNaopnlkLpER+55hdO3hUV/jHCLelpJkQuGDQFMf2qtFYJw4jQEhuH6kXQSwFTggA==;24:LO3dPlHJuzloOYClCmaoGAr6f2kNQvB1X0LRkTGXY6A7/bOsefqw0uwJrE8LqlOyaZESIZXbjjqsL7yrV0IQP3hDQmkG7TJDj7MjbQyGm/0=;7:3R6Q6jA6s/2uEQUrE4TE/RanyBNxTiQE0TJT54rKrVl2tg7dhkafp38oZs31QXgNdSpOCoc5lgjQ7jYmrR3xyvzhs92FiL9pPhLugeaHiPaMKNsE/R6IMsFi4j7u44FRGfn8/OOlSXuANILM3FR3+ovc/1E2PChTARv1EbCGe487/726FKFVU85ACQcDrVcD8g17WsxHpG111UqFANsLwaJlFVTMPChhRH2jRUA5/cGr3d3iIXw7O0C6W8FrZqjf SpamDiagnosticOutput: 1:99 SpamDiagnosticMetadata: NSPM X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Aug 2016 01:42:32.7288 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB6PR0501MB2757 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/17/2016 3:37 PM, Christoph Lameter wrote: > On Tue, 16 Aug 2016, Chris Metcalf wrote: > >> - Dropped Christoph Lameter's patch to avoid scheduling the >> clocksource watchdog on nohz cores; the recommendation is to just >> boot with tsc=reliable for NOHZ in any case, if necessary. > We also said that there should be a WARN_ON if tsc=reliable is not > specified and processors are put into NOHZ mode. This is something not > obvious causing scheduling events on NOHZ processors. Yes, I agree. Frederic said he would queue a patch to do that, so I didn't want to propose another patch that would conflict. >> Frederic, do you have a sense of what is left to be done there? >> I can certainly try to contribute to that effort as well. > Here is a potential fix to the problem that /proc/stat values freeze when > processors go into NOHZ busy mode. I'd like to hear what people think > about the approach here. In particular one issue may be that I am > accessing remote tick-sched structures without serialization. But for > top/ps this may be ok. I noticed that other values shown by top/os also > sometime are a bit fuzzy. This seems pretty plausible to me, but I'm not an expert on what kind of locking might be required for these data structures. -- Chris Metcalf, Mellanox Technologies http://www.mellanox.com