From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v7 05/14] sched: Introduce a sched_feat for Energy Aware Scheduling Date: Tue, 2 Oct 2018 14:34:16 +0200 Message-ID: <20181002123416.GA3439@hirez.programming.kicks-ass.net> References: <20180912091309.7551-1-quentin.perret@arm.com> <20180912091309.7551-6-quentin.perret@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20180912091309.7551-6-quentin.perret@arm.com> Sender: linux-kernel-owner@vger.kernel.org To: Quentin Perret Cc: rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, gregkh@linuxfoundation.org, mingo@redhat.com, dietmar.eggemann@arm.com, morten.rasmussen@arm.com, chris.redpath@arm.com, patrick.bellasi@arm.com, valentin.schneider@arm.com, vincent.guittot@linaro.org, thara.gopinath@linaro.org, viresh.kumar@linaro.org, tkjos@google.com, joel@joelfernandes.org, smuckle@google.com, adharmap@codeaurora.org, skannan@codeaurora.org, pkondeti@codeaurora.org, juri.lelli@redhat.com, edubezval@gmail.com, srinivas.pandruvada@linux.intel.com, currojerez@riseup.net, javi.merino@kernel.org List-Id: linux-pm@vger.kernel.org On Wed, Sep 12, 2018 at 10:13:00AM +0100, Quentin Perret wrote: > In order to make sure Energy Aware Scheduling (EAS) doesn't hurt > systems not using it, add a new sched_feat, called ENERGY_AWARE, > guarding the access to EAS code paths. > > Signed-off-by: Quentin Perret > --- > kernel/sched/features.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/kernel/sched/features.h b/kernel/sched/features.h > index 85ae8488039c..26ff6752e492 100644 > --- a/kernel/sched/features.h > +++ b/kernel/sched/features.h > @@ -90,3 +90,10 @@ SCHED_FEAT(WA_BIAS, true) > * UtilEstimation. Use estimated CPU utilization. > */ > SCHED_FEAT(UTIL_EST, true) > + > +/* > + * Energy-Aware Scheduling. Whether or not tasks will be placed into an > + * energy-aware fashion depends on this feature being enabled and on the > + * root domain having an Energy Model attached. > + */ > +SCHED_FEAT(ENERGY_AWARE, false) So these are debug knobs.. I would expect there to be a regular static_key that is controlled by the presence of EM data. Remember, if you compile with SCHED_DEBUG=n, this becomes a compile time constant: false, and the compiler gets to do lots of DCE.