linux-kernel - Re: cpufreq/thermal regression in 6.10

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Date: Mon, 10 Jun 2024 13:17:07 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Johan Hovold <johan@...nel.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, Daniel Lezcano <daniel.lezcano@...aro.org>, 
	Viresh Kumar <viresh.kumar@...aro.org>, Zhang Rui <rui.zhang@...el.com>, 
	Lukasz Luba <lukasz.luba@....com>, Steev Klimaszewski <steev@...i.org>, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, regressions@...ts.linux.dev
Subject: Re: cpufreq/thermal regression in 6.10

Hi,

Thanks for the report.

On Sun, Jun 9, 2024 at 9:53 AM Johan Hovold <johan@...nel.org> wrote:
>
> Hi,
>
> Steev reported to me off-list that the CPU frequency of the big cores on
> the Lenovo ThinkPad X13s sometimes appears to get stuck at a low
> frequency with 6.10-rc2.
>
> I just confirmed that once the cores are fully throttled (using the
> stepwise thermal governor) due to the skin temperature reaching the
> first trip point, scaling_max_freq gets stuck at the next OPP:
>
>         cpu4/cpufreq/scaling_max_freq:940800
>         cpu5/cpufreq/scaling_max_freq:940800
>         cpu6/cpufreq/scaling_max_freq:940800
>         cpu7/cpufreq/scaling_max_freq:940800
>
> when the temperature drops again.

So apparently something fails to update its frequency QoS request.

Would it be possible to provoke this with thermal debug enabled
(CONFIG_THERMAL_DEBUGFS set) and see what's there in
/sys/kernel/debug/thermal/?

> This obviously leads to a massive performance drop and could possibly
> also be related to reports like this one:
>
>         https://lore.kernel.org/all/CAHk-=wjwFGQZcDinK=BkEaA8FSyVg5NaUe0BobxowxeZ5PvetA@mail.gmail.com/
>
> I assume the regression may have been introduced by all the thermal work
> that went into 6.10-rc1, but I don't have time to try to track this down
> myself right now (and will be away from keyboard most of next week).
>
> I've confirmed that 6.9 works as expected.

Well, I'd need to ask someone else affected by this, then.