From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760072AbcIMSpZ (ORCPT ); Tue, 13 Sep 2016 14:45:25 -0400 Received: from mail-db5eur01on0074.outbound.protection.outlook.com ([104.47.2.74]:24800 "EHLO EUR01-DB5-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1759605AbcIMSpW (ORCPT ); Tue, 13 Sep 2016 14:45:22 -0400 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=cmetcalf@mellanox.com; Subject: Re: Ping: [PATCH v15 00/13] support "task_isolation" mode To: Francis Giraldeau , Gilad Ben Yossef , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Andrew Morton , Rik van Riel , Tejun Heo , Frederic Weisbecker , Thomas Gleixner , "Paul E. McKenney" , Christoph Lameter , Viresh Kumar , Catalin Marinas , Will Deacon , Andy Lutomirski , Daniel Lezcano , , , References: <1471382376-5443-1-git-send-email-cmetcalf@mellanox.com> <057a958c-4491-b449-ae59-7d331afc872d@gmail.com> <909484ad-534d-524a-51db-19b7d013f73e@mellanox.com> <3e93004f-e1c5-f606-33fb-7cb44b99eb0a@gmail.com> From: Chris Metcalf Message-ID: Date: Tue, 13 Sep 2016 12:12:06 -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: <3e93004f-e1c5-f606-33fb-7cb44b99eb0a@gmail.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [108.20.173.108] X-ClientProxiedBy: CY1PR17CA0006.namprd17.prod.outlook.com (10.163.68.16) To VI1PR0501MB2765.eurprd05.prod.outlook.com (10.172.11.15) X-MS-Office365-Filtering-Correlation-Id: 586e5c68-e48a-4647-3d81-08d3dbf0be0c X-Microsoft-Exchange-Diagnostics: 1;VI1PR0501MB2765;2:WYkqAYsNK/x/Gp1l7TXHQs1L3y/GAWK/cNd8ORF5FTdcyVjYimIjWZV7DzJylJAjNjW9MmNff9nJZSj+y+ZzOdSMpXTl/Z9T93X6eG2hqntO6Fu+ojLkLivvnBEF1hYtStaDAKLBfu1dUYJrZVPKMmsa9V+Nyw5YAgA6IRmeb9cu4tznfk5JQp6dWS1sSHXa;3:MtVIrfLe6LCkuTpSuIvfPusuqH6GEbSYu1AyKw1FGFvQy/CmuORFiQG1x0QMe7bLdm3nKjswUv5poXksJdlvhp5jZDCWFFSfbl53hVXzMMslFbLTMANY0a+4aof+msUW;25:hzuRo8igBvMw+sM7gqO68W/+SvCWxHOezg5Y5vBIXThzJiAiyu2rkyC/yFftaW/5aPopOjQEhRt7VgkCJc5xE88jNP2TFyf+TNcuufkI5GaQs7m6tOmNo4KWZi/6hVf1/mG4s8y/OC2zDxxTunSDb8jLJ961mw0MX6E0fXCoKHo+4UKluCB9dxQH+8j3RN7zOh91BYNaT2/Jt2jO5x+fH6AVci3pacxIi29ETG28rwWB3L3UUb4Jp/4A1S81E3VfVtZjSUN68xJV4HfcUufT0rrwDqYC9GotLoBPwKcKuIW7RZzoMZF2bKtB1rFhp82kD21YWvspHgjpbzG4DHUQO/1wpfcDKW7Xz8hGR8B+uihOBbbn38nIEIA9gJSk9VVbqqpOoM4gExugM8RtJ7tqdf+wfE8EnWmxennVuY7ChWM= X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:VI1PR0501MB2765; 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It makes perfect sense in retrospect :-) On 9/12/2016 8:20 PM, Francis Giraldeau wrote: > On a side note, the NOSIG mode may be confusing for the users. At first, > I was expecting that NOSIG behaves the same way as the normal task isolation > mode. In the current situation, if the user wants the normal behavior, but > does not care about the signal, the user must register an empty signal handler. So, "normal behavior" isn't really well defined once we start allowing empty signal handlers. In particular, task isolation will be turned off before invoking your signal handler, and if the handler is empty, you just lose isolation and that's that. By contrast, the NOSIG mode will try to keep you isolated. I'm definitely open to suggestions about how to frame the API for NOSIG or equivalent modes. What were you expecting to be able to do by suppressing the signal, and how is NOSIG not the thing you wanted? > However, if I understand correctly, other settings beside NOHZ and isolcpus > are required to support quiet CPUs, such as irq_affinity and rcu_nocb. It would > be very convenient from the user point of view if these other settings were configure > correctly. I think it makes sense to move towards a mode where enabling task_isolation sets up the rcu_nocbs and irq_affinity automatically, rather than requiring users to understand all the fiddly configuration and boot argument details. > I can work on that and also write some doc (Documentation/task-isolation.txt ?). Sure, documentation is always welcome! -- Chris Metcalf, Mellanox Technologies http://www.mellanox.com