From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752997AbbJTJcf (ORCPT ); Tue, 20 Oct 2015 05:32:35 -0400 Received: from terminus.zytor.com ([198.137.202.10]:49685 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752617AbbJTJc3 (ORCPT ); Tue, 20 Oct 2015 05:32:29 -0400 Date: Tue, 20 Oct 2015 02:31:42 -0700 From: tip-bot for Frederic Weisbecker Message-ID: Cc: linux-kernel@vger.kernel.org, umgwanakikbuti@gmail.com, mingo@kernel.org, oleg@redhat.com, hpa@zytor.com, torvalds@linux-foundation.org, efault@gmx.de, riel@redhat.com, akpm@linux-foundation.org, paulmck@linux.vnet.ibm.com, fweisbec@gmail.com, peterz@infradead.org, adobriyan@gmail.com, davej@redhat.com, cmetcalf@ezchip.com, cl@linux.com, tglx@linutronix.de Reply-To: cl@linux.com, tglx@linutronix.de, cmetcalf@ezchip.com, davej@redhat.com, adobriyan@gmail.com, peterz@infradead.org, fweisbec@gmail.com, paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org, torvalds@linux-foundation.org, riel@redhat.com, efault@gmx.de, hpa@zytor.com, mingo@kernel.org, oleg@redhat.com, linux-kernel@vger.kernel.org, umgwanakikbuti@gmail.com In-Reply-To: <1444663283-30068-1-git-send-email-fweisbec@gmail.com> References: <1444663283-30068-1-git-send-email-fweisbec@gmail.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] nohz: Revert "nohz: Set isolcpus when nohz_full is set" Git-Commit-ID: 0baabb385eb4bce699ddab0db015112be6cf1e6a X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 0baabb385eb4bce699ddab0db015112be6cf1e6a Gitweb: http://git.kernel.org/tip/0baabb385eb4bce699ddab0db015112be6cf1e6a Author: Frederic Weisbecker AuthorDate: Mon, 12 Oct 2015 17:21:23 +0200 Committer: Ingo Molnar CommitDate: Tue, 20 Oct 2015 10:13:36 +0200 nohz: Revert "nohz: Set isolcpus when nohz_full is set" This reverts: 8cb9764fc88b ("nohz: Set isolcpus when nohz_full is set") We assumed that full-nohz users always want scheduler isolation on full dynticks CPUs, therefore we included full-nohz CPUs on cpu_isolated_map. This means that tasks run by default on CPUs outside the nohz_full range unless their affinity is explicity overwritten. This suits pure isolation workloads but when the machine is needed to run common workloads, the available sets of CPUs to run common tasks becomes reduced. We reach an extreme case when CONFIG_NO_HZ_FULL_ALL is enabled as it leaves only CPU 0 for non-isolation tasks, which makes people think that their supercomputer regressed to 90's UP - which is true in a sense. Some full-nohz users appear to be interested in running normal workloads either before or after an isolation workload. Full-nohz isn't optimized toward normal workloads but it's still better than UP performance. We are reaching a limitation in kernel presets here. Lets revert this cpu_isolated_map inclusion and let userspace do its own scheduler isolation using cpusets or explicit affinity settings. Reported-by: Ingo Molnar Reported-by: Mike Galbraith Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Acked-by: Thomas Gleixner Cc: Alexey Dobriyan Cc: Andrew Morton Cc: Chris Metcalf Cc: Christoph Lameter Cc: Dave Jones Cc: Linus Torvalds Cc: Mike Galbraith Cc: Oleg Nesterov Cc: Paul E . McKenney Cc: Peter Zijlstra Cc: Rik van Riel Link: http://lkml.kernel.org/r/1444663283-30068-1-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 10a8faa..5bd7d60 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7238,9 +7238,6 @@ void __init sched_init_smp(void) alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL); alloc_cpumask_var(&fallback_doms, GFP_KERNEL); - /* nohz_full won't take effect without isolating the cpus. */ - tick_nohz_full_add_cpus_to(cpu_isolated_map); - sched_init_numa(); /*