Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753125AbbBSRBj (ORCPT ); Thu, 19 Feb 2015 12:01:39 -0500 Received: from foss-mx-na.arm.com ([217.140.108.86]:44138 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751981AbbBSRBi (ORCPT ); Thu, 19 Feb 2015 12:01:38 -0500 Date: Thu, 19 Feb 2015 17:02:36 +0000 From: Morten Rasmussen To: Peter Zijlstra Cc: Vincent Guittot , "mingo@kernel.org" , "linux-kernel@vger.kernel.org" , "preeti@linux.vnet.ibm.com" , "kamalesh@linux.vnet.ibm.com" , "riel@redhat.com" , "efault@gmx.de" , "nicolas.pitre@linaro.org" , Dietmar Eggemann , "linaro-kernel@lists.linaro.org" , Paul Turner , Ben Segall Subject: Re: [PATCH RESEND v9 04/10] sched: Make sched entity usage tracking scale-invariant Message-ID: <20150219170236.GB22059@e105550-lin.cambridge.arm.com> References: <1421316570-23097-1-git-send-email-vincent.guittot@linaro.org> <1421316570-23097-5-git-send-email-vincent.guittot@linaro.org> <20150219163442.GK5029@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150219163442.GK5029@twins.programming.kicks-ass.net> 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: 2734 Lines: 71 On Thu, Feb 19, 2015 at 04:34:42PM +0000, Peter Zijlstra wrote: > On Thu, Jan 15, 2015 at 11:09:24AM +0100, Vincent Guittot wrote: > > From: Morten Rasmussen > > > > Apply frequency scale-invariance correction factor to usage tracking. > > Each segment of the running_load_avg geometric series is now scaled by the > > current frequency so the utilization_avg_contrib of each entity will be > > invariant with frequency scaling. > > > As a result, utilization_load_avg which is > > the sum of utilization_avg_contrib, becomes invariant too. So the usage level > > that is returned by get_cpu_usage, stays relative to the max frequency as the > > cpu_capacity which is is compared against. > > > Then, we want the keep the load tracking values in a 32bits type, which implies > > that the max value of {runnable|running}_avg_sum must be lower than > > 2^32/88761=48388 (88761 is the max weigth of a task). > > > As LOAD_AVG_MAX = 47742, > > arch_scale_freq_capacity must return a value less than > > (48388/47742) << SCHED_CAPACITY_SHIFT = 1037 (SCHED_SCALE_CAPACITY = 1024). > > So we define the range to [0..SCHED_SCALE_CAPACITY] in order to avoid overflow. > > > cc: Paul Turner > > cc: Ben Segall > > > > Signed-off-by: Morten Rasmussen > > Signed-off-by: Vincent Guittot > > --- > > kernel/sched/fair.c | 21 ++++++++++++++------- > > 1 file changed, 14 insertions(+), 7 deletions(-) > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index a96affd..a5039da 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -2266,6 +2266,8 @@ static u32 __compute_runnable_contrib(u64 n) > > return contrib + runnable_avg_yN_sum[n]; > > } > > > > +unsigned long __weak arch_scale_freq_capacity(struct sched_domain *sd, int cpu); > > There is no actual function definition in this patch; this would hinder > linking, no? The function definition already lives further down in fair.c. I can move it up here if you prefer? > > > > if (running) > > + sa->running_avg_sum += delta_w * scale_freq > > + >> SCHED_CAPACITY_SHIFT; > > > > if (running) > > + sa->running_avg_sum += runnable_contrib * scale_freq > > + >> SCHED_CAPACITY_SHIFT; > > > if (running) > > + sa->running_avg_sum += delta * scale_freq > > + >> SCHED_CAPACITY_SHIFT; > > If you're going to respin; please but {} around that. Sure. -- 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/