Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751722Ab3CUS7X (ORCPT ); Thu, 21 Mar 2013 14:59:23 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:60476 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751096Ab3CUS7W (ORCPT ); Thu, 21 Mar 2013 14:59:22 -0400 Date: Thu, 21 Mar 2013 11:59:08 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: Christoph Lameter , Frederic Weisbecker , Rob Landley , linux-kernel@vger.kernel.org, josh@joshtriplett.org, zhong@linux.vnet.ibm.com, khilman@linaro.org, geoff@infradead.org, tglx@linutronix.de Subject: Re: [PATCH] nohz1: Documentation Message-ID: <20130321185908.GG3637@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1363636794.15703.32@driftwood> <20130318222548.GG3656@linux.vnet.ibm.com> <1363822338.6345.33.camel@gandalf.local.home> <20130320235545.GL3637@linux.vnet.ibm.com> <0000013d8db514e4-bf492080-82c9-412a-90b8-54ddc1463e4b-000000@email.amazonses.com> <20130321171518.GW3637@linux.vnet.ibm.com> <1363891462.6345.52.camel@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1363891462.6345.52.camel@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13032118-7606-0000-0000-000009BB759A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1546 Lines: 32 On Thu, Mar 21, 2013 at 02:44:22PM -0400, Steven Rostedt wrote: > On Thu, 2013-03-21 at 10:15 -0700, Paul E. McKenney wrote: > > > > The OS always has some sched other tasks around that become runnable after > > > a while (like for example the vm statistics update, or the notorious slab > > > scanning). As long as SCHED_FIFO is active and there is no process in the > > > same scheduling class then tick needs to be off. Also wish that this would > > > work with SCHED_OTHER if there is only a single task with a certain renice > > > value (-10?) and the rest is runnable at lower priorities. Maybe in that > > > case stop the tick for a longer period and then give the lower priority > > > tasks a chance to run but then switch off the tick again. > > > > These sound to me like good future enhancements. > > Exactly. Please, this is a complex enough change to something that is > critical to the entire system (similar to RCU itself). Lets take baby > steps here and get it right each step of the way. > > For now, no, if more than one process is scheduled on the CPU, we fall > out of dynamic tick mode. In the future, we can add SCHED_FIFO task > scheduled in to trigger it. But lets conquer that after we successfully > conquer the current changes. What Steve said!!! Thanx, Paul -- 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/