Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751673Ab3GORJO (ORCPT ); Mon, 15 Jul 2013 13:09:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:26923 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751227Ab3GORJN (ORCPT ); Mon, 15 Jul 2013 13:09:13 -0400 Date: Mon, 15 Jul 2013 13:08:59 -0400 From: Dave Jones To: Linux Kernel Mailing List Cc: rostedt@goodmis.org, fweisbec@gmail.com Subject: Re: nohz: Warn if the machine can not perform nohz_full Message-ID: <20130715170859.GA25570@redhat.com> Mail-Followup-To: Dave Jones , Linux Kernel Mailing List , rostedt@goodmis.org, fweisbec@gmail.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1850 Lines: 45 > Gitweb: http://git.kernel.org/linus/;a=commit;h=e12d0271774fea9fddf1e2a7952a0bffb2ee8e8b > Commit: e12d0271774fea9fddf1e2a7952a0bffb2ee8e8b > Parent: 7d132055814ef17a6c7b69f342244c410a5e000f > Author: Steven Rostedt > AuthorDate: Fri May 10 17:12:28 2013 -0400 > Committer: Frederic Weisbecker > CommitDate: Thu Jun 20 01:15:51 2013 +0200 > > nohz: Warn if the machine can not perform nohz_full > > If the user configures NO_HZ_FULL and defines nohz_full=XXX on the > kernel command line, or enables NO_HZ_FULL_ALL, but nohz fails > due to the machine having a unstable clock, warn about it. > > We do not want users thinking that they are getting the benefit > of nohz when their machine can not support it. > --- > kernel/time/tick-sched.c | 5 +++++ > 1 files changed, 5 insertions(+), 0 deletions(-) > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > index f420813..d87d22c 100644 > --- a/kernel/time/tick-sched.c > +++ b/kernel/time/tick-sched.c > @@ -178,6 +178,11 @@ static bool can_stop_full_tick(void) > */ > if (!sched_clock_stable) { > trace_tick_stop(0, "unstable sched clock\n"); > + /* > + * Don't allow the user to think they can get > + * full NO_HZ with this machine. > + */ > + WARN_ONCE(1, "NO_HZ FULL will not work with unstable sched clock"); > return false; So I guess you guys never want this to be enabled on distro kernels ? If that's the case, can you add something to that effect in Kconfig ? Dave -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/