linux-kernel - Re: [RFC PATCH] ARM: configs: sunxi: Set ondemand govenor as default

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Date:   Tue, 27 Feb 2018 08:12:11 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Philipp Rossak <embed3d@...il.com>
Cc:     linux@...linux.org.uk, wens@...e.org, davem@...emloft.net,
        arnd@...db.de, mchehab@...nel.org, clabbe.montjoie@...il.com,
        rask@...melder.dk, krzk@...nel.org, sean@...s.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: Re: [RFC PATCH] ARM: configs: sunxi: Set ondemand govenor as default

On Mon, Feb 26, 2018 at 10:29:29PM +0100, Philipp Rossak wrote:
> 
> 
> On 19.02.2018 09:10, Maxime Ripard wrote:
> > On Sat, Feb 17, 2018 at 03:22:35PM +0100, Philipp Rossak wrote:
> > > Right now the performance govenor is the default frequency govenor on
> > > sunxi devices. This causes some general problems.
> > > When the cpu is idle the cpu runs with its maximum frequency.
> > > This causes a higher cpu temperature in the idle state. When the cpu is
> > > now under load the cpu gets with that higher idle temperature now faster
> > > to its thermal limits.
> > > An other big problem of the performace govenor is the missing
> > > thermal throttling. Some tests with cpuburn resulted in a system crash
> > > when the soc reached its thermal limits since no thermal throttling
> > > occurred.
> > 
> > This won't change anything with cpuburn. While cpuburn will be
> > running, ondemand will increase the frequency of the cores to the
> > maximum frequency, putting yourself in the exact same situation.
>
> I see here a totally different behavior on the hardware (Bananapi M2, A31s).
> First ondemand increases the cpu frequency, when the maximum temperature is
> reached, then it throttles down the cpu step by step to its minimum.

This is the thermal throttling, not the cpufreq governor.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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