Re: Linux 6.10-rc2 - massive performance regression

[Linux regression tracking (Thorsten Leemhuis)]

On 09.06.24 00:00, Linus Torvalds wrote:
> On Sat, 8 Jun 2024 at 14:36, David Laight <David.Laight@xxxxxxxxxx> wrote:
> [...]
>> I've done some tests.
>> I'm seeing a three-fold slow down on:
>> $ i=0; while [ $i -lt 1000000 ]; do i=$((i + 1)); done
>> which goes from 1 second to 3.
>>
>> I can run that with ftrace monitoring scheduler events (and a few
>> other things) and can't spot anywhere the process isn't running
>> for a significant time.
> 
> Sounds like cpu frequency. Almost certainly hw-specific. I went
> through that on my Threadripper in the 6.9 timeframe, but I'm not
> seeing any issues in this current release.

David, what kind of hardware do you use? Johan Hovold as
man-in-the-middle just reported "CPU frequency of the big cores on the
Lenovo ThinkPad X13s sometimes appears to get stuck at a low frequency
with 6.10-rc2" and 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".

For more details, see:
https://lore.kernel.org/all/ZmVfcEOxmjUHZTSX@xxxxxxxxxxxxxxxxxxxx/

> If you bisect it, we have somebody to blame and point fingers at...

Sadly that one is not bisected yet either. :-/

Ciao, Thorsten