Re: cpufreq/thermal regression in 6.10

[Rafael J. Wysocki]

On Mon, Jun 10, 2024 at 1:17 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
>
> Hi,
>
> Thanks for the report.
>
> On Sun, Jun 9, 2024 at 9:53 AM Johan Hovold <johan@xxxxxxxxxx> 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@xxxxxxxxxxxxxx/
> >
> > 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.

If this is the step-wise governor, the problem might have been
introduced by commit

042a3d80f118 thermal: core: Move passive polling management to the core

which removed passive polling count updates from that governor, so if
the thermal zone in question has passive polling only and no regular
polling, temperature updates may stop coming before the governor drops
the cooling device states to the "no target" level.

So please test the attached partial revert of the above commit when you can.
---
 drivers/thermal/gov_step_wise.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

Index: linux-pm/drivers/thermal/gov_step_wise.c
===================================================================
--- linux-pm.orig/drivers/thermal/gov_step_wise.c
+++ linux-pm/drivers/thermal/gov_step_wise.c
@@ -93,6 +93,16 @@ static void thermal_zone_trip_update(str
 		if (instance->initialized && old_target == instance->target)
 			continue;
 
+		if (trip->type == THERMAL_TRIP_PASSIVE) {
+			/* If needed, update the status of passive polling. */
+			if (old_target == THERMAL_NO_TARGET &&
+			    instance->target != THERMAL_NO_TARGET)
+				tz->passive++;
+			else if (old_target != THERMAL_NO_TARGET &&
+				 instance->target == THERMAL_NO_TARGET)
+				tz->passive--;
+		}
+
 		instance->initialized = true;
 
 		mutex_lock(&instance->cdev->lock);