Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752625AbbBSQew (ORCPT ); Thu, 19 Feb 2015 11:34:52 -0500 Received: from casper.infradead.org ([85.118.1.10]:46154 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751728AbbBSQeu (ORCPT ); Thu, 19 Feb 2015 11:34:50 -0500 Date: Thu, 19 Feb 2015 17:34:42 +0100 From: Peter Zijlstra To: Vincent Guittot Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, preeti@linux.vnet.ibm.com, Morten.Rasmussen@arm.com, kamalesh@linux.vnet.ibm.com, riel@redhat.com, efault@gmx.de, nicolas.pitre@linaro.org, dietmar.eggemann@arm.com, 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: <20150219163442.GK5029@twins.programming.kicks-ass.net> References: <1421316570-23097-1-git-send-email-vincent.guittot@linaro.org> <1421316570-23097-5-git-send-email-vincent.guittot@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1421316570-23097-5-git-send-email-vincent.guittot@linaro.org> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2444 Lines: 64 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? > 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. -- 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/