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Date:   Thu, 25 Apr 2019 13:47:44 +0100
From:   Quentin Perret <quentin.perret@arm.com>
To:     Vincent Guittot <vincent.guittot@linaro.org>
Cc:     Thara Gopinath <thara.gopinath@linaro.org>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Zhang Rui <rui.zhang@intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Amit Kachhap <amit.kachhap@gmail.com>,
        viresh kumar <viresh.kumar@linaro.org>,
        Javi Merino <javi.merino@kernel.org>,
        Eduardo Valentin <edubezval@gmail.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Nicolas Dechesne <nicolas.dechesne@linaro.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>
Subject: Re: [PATCH V2 1/3] Calculate Thermal Pressure
Message-ID: <20190425124741.y5stnnf7moujmout@queper01-ThinkPad-T460s>
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On Thursday 25 Apr 2019 at 14:45:57 (+0200), Vincent Guittot wrote:
> On Thu, 25 Apr 2019 at 12:57, Quentin Perret <quentin.perret@arm.com> wrote:
> >
> > On Tuesday 16 Apr 2019 at 15:38:39 (-0400), Thara Gopinath wrote:
> > > +/* Per cpu structure to keep track of Thermal Pressure */
> > > +struct thermal_pressure {
> > > +     unsigned long scale; /* scale reflecting average cpu max capacity*/
> > > +     unsigned long acc_scale; /* Accumulated scale for this time window */
> > > +     unsigned long old_scale; /* Scale value for the previous window */
> > > +     unsigned long raw_scale; /* Raw max capacity */
> > > +     unsigned long age_stamp; /* Last time old_scale was updated */
> > > +     unsigned long last_update; /* Last time acc_scale was updated */
> > > +     spinlock_t lock; /* Lock for protecting from simultaneous access*/
> > > +     /* Timer for periodic update of thermal pressure */
> > > +     struct timer_list timer;
> >
> > Do you actually need the periodic update ? You only really need to
> > update the 'scale' value when updating the LB stats no ? Nobody
> > accesses that value in between two LBs.
> 
> Do you mean calling a variant of sched_update_thermal_pressure() in
> update_cpu_capacity() instead of periodic update ?
> Yes , that should be enough

Right something like this, and remove all the timers. Should be a bit
cleaner I guess.

Thanks,
Quentin