Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20181010082933.4ful4dzk7rkijcwu@queper01-lin> <CAKfTPtA1sgf77xLUPr74iEEb+W8PGCMCkgu+Kw8xM_Jxx7_hjQ@mail.gmail.com>
 <20181010095459.orw2gse75klpwosx@queper01-lin> <CAKfTPtA+FWrMnerQhrNQhvmvVSK_S86da=8shpdET-807zZgVg@mail.gmail.com>
 <20181010103623.ttjexasymdpi66lu@queper01-lin> <CAKfTPtBM24F99OhtjWU-cx4DdFFpvUMMDYuqZH_vaJg9HEpPTw@mail.gmail.com>
 <20181010122348.GL9130@localhost.localdomain> <CAKfTPtCVryjWWT_M1zEZfJUjGkt2JPUiBK6vt0YiJTK4qVoqbA@mail.gmail.com>
 <20181010125033.GP9130@localhost.localdomain> <CAKfTPtAL5b0ZAOY_85ajskOX+thLf3j3M-xJ+Pt_NrM+N8udPw@mail.gmail.com>
 <20181010133443.GR9130@localhost.localdomain>
In-Reply-To: <20181010133443.GR9130@localhost.localdomain>
From:   Vincent Guittot <vincent.guittot@linaro.org>
Date:   Wed, 10 Oct 2018 15:38:57 +0200
Message-ID: <CAKfTPtAyhXtKH3XeQHUHZLK+uvdsAzh5H=X+1OOAWFpP9o-L5w@mail.gmail.com>
Subject: Re: [RFC PATCH 0/7] Introduce thermal pressure
To:     Juri Lelli <juri.lelli@gmail.com>
Cc:     Quentin Perret <quentin.perret@arm.com>,
        Ingo Molnar <mingo@kernel.org>,
        Thara Gopinath <thara.gopinath@linaro.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Zhang Rui <rui.zhang@intel.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@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>,
        "open list:THERMAL" <linux-pm@vger.kernel.org>,
        Ionela Voinescu <ionela.voinescu@arm.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, 10 Oct 2018 at 15:35, Juri Lelli <juri.lelli@gmail.com> wrote:
>
> On 10/10/18 15:08, Vincent Guittot wrote:
> > On Wed, 10 Oct 2018 at 14:50, Juri Lelli <juri.lelli@gmail.com> wrote:
> > >
> > > On 10/10/18 14:34, Vincent Guittot wrote:
> > > > Hi  Juri,
> > > >
> > > > On Wed, 10 Oct 2018 at 14:23, Juri Lelli <juri.lelli@gmail.com> wrote:
> > > > >
> > > > > On 10/10/18 14:04, Vincent Guittot wrote:
> > > > >
> > > > > [...]
> > > > >
> > > > > > The problem was the same with RT, the cfs utilization was lower than
> > > > > > reality because RT steals soem cycle to CFS
> > > > > > So schedutil was selecting a lower frequency when cfs was running
> > > > > > whereas the CPU was fully used.
> > > > > > The same can happen with thermal:
> > > > > > cap the max freq because of thermal
> > > > > > the utilization with decrease.
> > > > > > remove the cap
> > > > > > the utilization is still low and you will select a low OPP because you
> > > > > > don't take into account cycle stolen by thermal like with RT
> > > > >
> > > > > What if we scale frequency component considering the capped temporary
> > > > > max?
> > > >
> > > > Do you mean using a kind of scale_thermal_capacity in accumulate_sum
> > > > when computing utilization ?
> > >
> > > Yeah, something like that I guess. So that we account for temporary
> > > "fake" 1024..
> >
> > But the utilization will not be invariant anymore across the system
>
> Mmm, I guess I might be wrong, but I was thinking we should be able to
> deal with this similarly to what we do with cpus with different max
> capacities. So, another factor?  Because then, how do we handle other
> ways in which max freq can be restricted (e.g. from userspace as Javi
> was also mentioning)?

IMHO, userspace capping is a different story because it is not
expected to happen so often but it should stay for a while and in this
case, a solution is probably to rebuild the sched_domain and update
all the cpu_capacity struct and fields