Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753625Ab2KTBRJ (ORCPT ); Mon, 19 Nov 2012 20:17:09 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:18764 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751786Ab2KTBRH (ORCPT ); Mon, 19 Nov 2012 20:17:07 -0500 X-Authority-Analysis: v=2.0 cv=f9bK9ZOM c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=yHbJst7BUucA:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=meVymXHHAAAA:8 a=eYYPdsDFe-UA:10 a=rWYUxwV3Lchv5pqS5qgA:9 a=PUjeQqilurYA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 74.67.115.198 Message-ID: <1353374226.6276.16.camel@gandalf.local.home> Subject: Re: [PATCH] nohz/cpuset: Make a CPU stick with do_timer() duty in the presence of nohz cpusets From: Steven Rostedt To: Hakan Akkan Cc: Frederic Weisbecker , LKML , Thomas Gleixner , Peter Zijlstra , Ingo Molnar Date: Mon, 19 Nov 2012 20:17:06 -0500 In-Reply-To: References: <4FDD7AA8.6080601@gmail.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.4.3-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1342 Lines: 29 On Mon, 2012-11-19 at 17:27 -0700, Hakan Akkan wrote: > > > > I suggest to rather define a tunable timekeeping duty CPU affinity in > > a cpumask file at /sys/devices/system/cpu/timekeeping and a toggle at > > /sys/devices/system/cpu/cpuX/timekeeping (like the online file). This > > way the user can decide whether adaptive nohz CPU can handle > > timekeeping or this must be forced to other CPUs in order to enforce > > isolation. > > Well, users want tickless CPUs because they don't want timekeeping > (or any other kernel activity for that matter) to run in there. So, I believe > having that "timekeeping affinity" stay in the regular CPUs is good enough. > Please let me know how users could utilize these control files to do anything > other than keeping the timekeeping out of adaptive nohz CPUs. I agree. If we already have some /sys cpumask that denotes which CPUs will be adaptive NO_HZ (or simply isolated) then just keep the tick from ever going on those CPUs. If all but one CPU is set for nohz, and that one CPU goes idle, it should still be the one doing the tick. -- Steve -- 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/