Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752101Ab3GORYl (ORCPT ); Mon, 15 Jul 2013 13:24:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:26324 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751383Ab3GORYk (ORCPT ); Mon, 15 Jul 2013 13:24:40 -0400 Date: Mon, 15 Jul 2013 13:24:23 -0400 From: Dave Jones To: Frederic Weisbecker Cc: Linux Kernel Mailing List , rostedt@goodmis.org Subject: Re: nohz: Warn if the machine can not perform nohz_full Message-ID: <20130715172423.GA27745@redhat.com> Mail-Followup-To: Dave Jones , Frederic Weisbecker , Linux Kernel Mailing List , rostedt@goodmis.org References: <20130715170859.GA25570@redhat.com> <20130715171800.GD6442@somewhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130715171800.GD6442@somewhere> 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: 1635 Lines: 36 On Mon, Jul 15, 2013 at 07:18:02PM +0200, Frederic Weisbecker wrote: > > 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 ? > > I believe we want it to be enabled on distros in the long term. But right now it would > be a bad idea until the off case (nohz_full= parameter empty) is carefully optimized. > I'm currently working on that. > > Now for the unstable tsc, which is what it's about on the above code block, we need > the tick to be there to leverage the sched clock madness. May be there could be some > other solution that could work along full dynticks but for now we chose the easy path. > > Are broken TSCs that common? I just hit one apparently. http://paste.fedoraproject.org/25421/73907845/raw/ That's a fairly recent Atom board, so I suspect it's not uncommon on that platform. > Also what is the preffered way to tell the distros that they shouldn't enable that option > for now? Here is what we currently have in the tail of the related Kconfig help: > > This is implemented at the expense of some overhead in user <-> kernel > transitions: syscalls, exceptions and interrupts. Even when it's > dynamically off. "This feature is not ready to be deployed" ? "This will taint the kernel if it decides it can't work" ? 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/