From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753521AbbDHJla (ORCPT ); Wed, 8 Apr 2015 05:41:30 -0400 Received: from casper.infradead.org ([85.118.1.10]:45802 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751287AbbDHJl0 (ORCPT ); Wed, 8 Apr 2015 05:41:26 -0400 Date: Wed, 8 Apr 2015 11:41:14 +0200 From: Peter Zijlstra To: cmetcalf@ezchip.com Cc: Frederic Weisbecker , "Paul E. McKenney" , "Rafael J. Wysocki" , Martin Schwidefsky , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/2] nohz: make nohz_full imply isolcpus Message-ID: <20150408094114.GX23123@twins.programming.kicks-ass.net> References: <5522BF1E.2040606@ezchip.com> <1428344205-27678-1-git-send-email-cmetcalf@ezchip.com> <1428344205-27678-2-git-send-email-cmetcalf@ezchip.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1428344205-27678-2-git-send-email-cmetcalf@ezchip.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 06, 2015 at 02:16:45PM -0400, cmetcalf@ezchip.com wrote: > From: Chris Metcalf > > It's not clear that nohz_full is useful without isolcpus also > set, since otherwise the scheduler has to run periodically to > try to determine whether to steal work from other cores. So the Changelog and the patch don't seem to agree with one another. The Changelog states that nohz_full should depend on isolcpus. The patch implies nohz_full for isolcpus. These are not the same; and I don't see the argument for the former make sense for the latter. In specific isolcpus without nohz_full does make sense. > Signed-off-by: Chris Metcalf > Acked-by: Mike Galbraith ["thumbs up!"] > Acked-by: Rik van Riel > --- > kernel/sched/core.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index f0f831e8a345..275f12c608f2 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -6836,6 +6836,7 @@ static int init_sched_domains(const struct cpumask *cpu_map) > doms_cur = alloc_sched_domains(ndoms_cur); > if (!doms_cur) > doms_cur = &fallback_doms; > + tick_nohz_full_set_cpus(cpu_isolated_map); > cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map); > err = build_sched_domains(doms_cur[0], NULL); > register_sched_domain_sysctl();