From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753349Ab0CWUcM (ORCPT ); Tue, 23 Mar 2010 16:32:12 -0400 Received: from casper.infradead.org ([85.118.1.10]:44209 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752933Ab0CWUcJ (ORCPT ); Tue, 23 Mar 2010 16:32:09 -0400 Subject: Re: [PATCH 2/3] sched: enforce per-cpu utilization limits on runtime balancing From: Peter Zijlstra To: Fabio Checconi Cc: Ingo Molnar , Thomas Gleixner , Paul Turner , Dario Faggioli , Michael Trimarchi , Dhaval Giani , Tommaso Cucinotta , linux-kernel@vger.kernel.org In-Reply-To: <20100303170014.GP2490@gandalf.sssup.it> References: <91b76b9b7555024d9afd7264eeae1b2db6a5e74c.1266931410.git.fabio@helm.retis> <1267129703.22519.559.camel@laptop> <20100303170014.GP2490@gandalf.sssup.it> Content-Type: text/plain; charset="UTF-8" Date: Tue, 23 Mar 2010 21:32:04 +0100 Message-ID: <1269376324.5283.6.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2010-03-03 at 18:00 +0100, Fabio Checconi wrote: > > From: Peter Zijlstra > > Date: Thu, Feb 25, 2010 09:28:23PM +0100 > > > > On Tue, 2010-02-23 at 19:56 +0100, Fabio Checconi wrote: > > > +#ifdef CONFIG_SMP > > > +static inline unsigned long rt_init_free_bw(void) > > > +{ > > > + unsigned long used = to_ratio(global_rt_period(), global_rt_runtime()); > > > + > > > + return to_ratio(RUNTIME_INF, RUNTIME_INF) - used; > > > +} > > > +#endif > > > > > +static void __rt_restart_balancing(void) > > > +{ > > > + unsigned long used, global, free; > > > + struct rq *rq; > > > + int i; > > > + > > > + used = rt_used_bandwidth(); > > > + global = to_ratio(RUNTIME_INF, RUNTIME_INF); > > > + > > > + free = global - used; > > > > > > We take the max as RUNTIME_INF instead of global_rt_* so that we can > > move runtime around and fully saturate a single cpu (given there is > > enough free to compensate on other cpus) ? > > The only reason I've used RUNTIME_INF instead of global_rt_* is for the > !GROUP_SCHED case, where using the global_rt_* values would make balancing > have no effect at all (the initial value for def_rt_bandwidth already > uses the maximum bw on each cpu) . The current throttling implementation > in this case still tries to concentrate bw on a single cpu, and I wanted > to replicate the same behaviour. > > Should I go for the global_rt_* values and add some #ifdef unreadability > to avoid the balancing overhead in the !GROUP_SCHED case? Nah, but adding a comment to clarify this might help.. I only asked because it was not immediately obvious.