Date: Thu, 31 Mar 2016 14:24:45 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Steve Muckle <steve.muckle@linaro.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Linux PM list <linux-pm@vger.kernel.org>,
        Juri Lelli <juri.lelli@arm.com>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v6 7/7][Resend] cpufreq: schedutil: New governor based on
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On Mon, Mar 28, 2016 at 11:17:44AM -0700, Steve Muckle wrote:
> The scenario I'm contemplating is that while a CPU-intensive task is
> running a thermal interrupt goes off. The driver for this thermal
> interrupt responds by capping fmax. If this happens just after the tick,
> it seems possible that we could wait a full tick before changing the
> frequency. Given a 10ms tick it could be rather annoying for thermal
> management algorithms on some platforms (I'm familiar with a few).

So I'm blissfully unaware of all the thermal stuffs we have; but it
looks like its somehow bolten onto cpufreq without feedback.

The thing I worry about is thermal scaling the CPU back past where RT/DL
tasks can still complete in time. It should not be able to do that, or
rather, missing deadlines because thermal is about as useful as
rebooting the device.

I guess I'm saying is, the whole cpufreq/thermal 'interface' needs work
anyhow.