From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756835AbcG0Pbg (ORCPT ); Wed, 27 Jul 2016 11:31:36 -0400 Received: from resqmta-ch2-09v.sys.comcast.net ([69.252.207.41]:40341 "EHLO resqmta-ch2-09v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755831AbcG0Pbd (ORCPT ); Wed, 27 Jul 2016 11:31:33 -0400 Date: Wed, 27 Jul 2016 10:31:31 -0500 (CDT) From: Christoph Lameter X-X-Sender: cl@east.gentwo.org To: Chris Metcalf cc: Gilad Ben Yossef , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Andrew Morton , Rik van Riel , Tejun Heo , Frederic Weisbecker , Thomas Gleixner , "Paul E. McKenney" , Viresh Kumar , Catalin Marinas , Will Deacon , Andy Lutomirski , Daniel Lezcano , linux-doc@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: clocksource_watchdog causing scheduling of timers every second (was [v13] support "task_isolation" mode) In-Reply-To: Message-ID: References: <1468529299-27929-1-git-send-email-cmetcalf@mellanox.com> <7a3f66f7-5011-7d59-2e0e-f57e4e42e6b6@mellanox.com> Content-Type: text/plain; charset=US-ASCII X-CMAE-Envelope: MS4wfEuMowhKPnet4fdTX1L9iC+I1o+aYKWNl48jAGkBFklp7b64BJd18zmBEiEFsgVYB8E9beTtiNYQ6aOklMhSusc9yTm+F0m07egVWm3yevXig3QqTZro BvrBb3quDbjOy3agzCj6YOXoE1eytMQ0ZUjBBkmaj0rYzUrbQq4gbajBIxsZMZxnM4ITm1B/xkVf1+DjTjBxiE3DqbwEMehjF9dB7qoP3weyYOKb/pIG/NJy Cc9BIiBoVyt1jtrSeUC/u6vwNCgtPWOTMK9KjfrYJ6Avk0adqQTIMCeowxg2b2d4K3LXJnkyCgQZORzOxjFNEG9ZupWfHjwHz1dPJmWhQ5ZLasU8rHBz9Or7 MQGxNP0Dd4cxKCUTgguzuOlhSbumSqX+HIsiubcCbjde+DEMwcBFrNgWnygBvlpOJ+B9QFKShXYsY3G4/auwmu8DILc70hf7Mhv5niVO0Hvnyvy2opqv+GcI 96o4mOeDRm1/ldxeDleCQiDi1sdD/Ze3BMUbzyDCpXh9r7ty8llDlnokD9BxqKHtQUmYobF2iCzjpaseeWa8+xw28GFHqYXwcSDxGocsvl5pGiK/SC8DBBPW 2SbQv/e7G+AznGwPkOOSWXaon8AcvZ62yhjX+Q/iwIjpQJrieuObRKkKhnvVr3oyd0QLHSbUsthFrAu58GpjENbC3B7qdwz7lTCdf+ju9Heem5N+1ipxL2KN sJKPMoq+d61d7aKIUrHn7ehuIzIRzoqjvcksbzAamsaVmBRAA3fkmw== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ok here is a possible patch that explicitly checks for housekeeping cpus: Subject: clocksource: Do not schedule watchdog on isolated or NOHZ cpus watchdog checks can only run on housekeeping capable cpus. Otherwise we will be generating noise that we would like to avoid on the isolated processors. Signed-off-by: Christoph Lameter Index: linux/kernel/time/clocksource.c =================================================================== --- linux.orig/kernel/time/clocksource.c 2016-07-27 08:41:17.109862517 -0500 +++ linux/kernel/time/clocksource.c 2016-07-27 10:28:31.172447732 -0500 @@ -269,9 +269,12 @@ static void clocksource_watchdog(unsigne * Cycle through CPUs to check if the CPUs stay synchronized * to each other. */ - next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask); - if (next_cpu >= nr_cpu_ids) - next_cpu = cpumask_first(cpu_online_mask); + do { + next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask); + if (next_cpu >= nr_cpu_ids) + next_cpu = cpumask_first(cpu_online_mask); + } while (!is_housekeeping_cpu(next_cpu)); + watchdog_timer.expires += WATCHDOG_INTERVAL; add_timer_on(&watchdog_timer, next_cpu); out: