From: Vincent Guittot <vincent.guittot@linaro.org>
To: Quentin Perret <quentin.perret@arm.com>
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 V3 3/3] thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping
Date: Thu, 25 Apr 2019 14:04:10 +0200 [thread overview]
Message-ID: <CAKfTPtAmCvQVudPrUzWa-yhPBRATFYr1a1=iPZ3fonv_K5wn5w@mail.gmail.com> (raw)
In-Reply-To: <20190425104504.pbej3b74pwinx6jj@queper01-ThinkPad-T460s>
On Thu, 25 Apr 2019 at 12:45, Quentin Perret <quentin.perret@arm.com> wrote:
>
> On Tuesday 23 Apr 2019 at 18:38:46 (-0400), Thara Gopinath wrote:
> > I think there is one major difference between user-defined frequency
> > constraints and frequency constraints due to thermal events in terms of
> > the time period the system spends in the the constraint state.
> > Typically, a user constraint lasts for seconds if not minutes and I
> > think in this case cpu_capacity_orig should reflect this constraint and
> > not cpu_capacity like this patch set.
>
> That might not always be true I think. There's tons of userspace thermal
> deamons out there, and I wouldn't be suprised if they were writing into
> the cpufreq sysfs files, although I'm not sure.
They would better use the sysfs set_target interface of cpu_cooling
device in this case.
>
> Another thing is, if you want to change the capacity_orig value, you'll
> need to rebuild the sched domains and all I believe. Otherwise there is
> a risk to 'break' the sd_asym flags. So we need to make sure we're happy
> to pay that price.
That would be the goal, if userspace uses the sysfs interface of
cpufreq to set a new max frequency, it should be considered as a long
change in regards to the scheduling rate and in this case it should be
interesting to update cpacity_orig and rebuild sched_domain.
>
> > Also, in case of the user
> > constraint, there is possibly no need to accumulate and average the
> > capacity constraints and instantaneous values can be directly applied to
> > cpu_capacity_orig. On the other hand thermal pressure is more spiky and
> > sometimes in the order of ms and us requiring the accumulating and
> > averaging.
> > >
> > > Perhaps the Intel boost stuff could be factored in there ? That is,
> > > at times when the boost freq is not reachable capacity_of() would appear
> > > smaller ... Unless this wants to be reflected instantaneously ?
> > Again, do you think intel boost is more applicable to be reflected in
> > cpu_capacity_orig and not cpu_capacity?
>
> I'm not even sure if we want to reflect it at all TBH, but I'd be
> interested to see what Intel folks think :-)
>
> Thanks,
> Quentin
next prev parent reply other threads:[~2019-04-25 12:04 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-16 19:38 [PATCH V2 0/3] Introduce Thermal Pressure Thara Gopinath
2019-04-16 19:38 ` [PATCH V2 1/3] Calculate " Thara Gopinath
2019-04-18 10:14 ` Quentin Perret
2019-04-24 4:13 ` Thara Gopinath
2019-04-24 16:38 ` Peter Zijlstra
2019-04-24 16:45 ` Peter Zijlstra
2019-04-25 10:57 ` Quentin Perret
2019-04-25 12:45 ` Vincent Guittot
2019-04-25 12:47 ` Quentin Perret
2019-04-26 14:17 ` Thara Gopinath
2019-05-08 12:41 ` Quentin Perret
2019-04-16 19:38 ` [PATCH V2 2/3] sched/fair: update cpu_capcity to reflect thermal pressure Thara Gopinath
2019-04-16 19:38 ` [PATCH V3 3/3] thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping Thara Gopinath
2019-04-18 9:48 ` Quentin Perret
2019-04-23 22:38 ` Thara Gopinath
2019-04-24 15:56 ` Ionela Voinescu
2019-04-26 10:24 ` Thara Gopinath
2019-04-25 10:45 ` Quentin Perret
2019-04-25 12:04 ` Vincent Guittot [this message]
2019-04-25 12:50 ` Quentin Perret
2019-04-26 13:47 ` Thara Gopinath
2019-04-24 16:47 ` Peter Zijlstra
2019-04-17 5:36 ` [PATCH V2 0/3] Introduce Thermal Pressure Ingo Molnar
2019-04-17 5:55 ` Ingo Molnar
2019-04-17 17:28 ` Thara Gopinath
2019-04-17 17:18 ` Thara Gopinath
2019-04-17 18:29 ` Ingo Molnar
2019-04-18 0:07 ` Thara Gopinath
2019-04-18 9:22 ` Quentin Perret
2019-04-24 16:34 ` Peter Zijlstra
2019-04-25 17:33 ` Ingo Molnar
2019-04-25 17:44 ` Ingo Molnar
2019-04-26 7:08 ` Vincent Guittot
2019-04-26 8:35 ` Ingo Molnar
2019-04-24 15:57 ` Ionela Voinescu
2019-04-26 11:50 ` Thara Gopinath
2019-04-26 14:46 ` Ionela Voinescu
2019-04-29 13:29 ` Ionela Voinescu
2019-04-30 14:39 ` Ionela Voinescu
2019-04-30 16:10 ` Thara Gopinath
2019-05-02 10:44 ` Ionela Voinescu
2019-04-30 15:57 ` Thara Gopinath
2019-04-30 16:02 ` Thara Gopinath
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