linux-kernel - Re: Thorsten is tracking regression again and could need a little help (was: Re: Linux 5.15)

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Date:   Mon, 1 Nov 2021 13:54:21 +0100
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     Idzibear <Idzibear@...utniks.org>
Cc:     linux-kernel@...r.kernel.org, regressions@...ts.linux.dev,
        torvalds@...ux-foundation.org
Subject: Re: Thorsten is tracking regression again and could need a little
 help (was: Re: Linux 5.15)

On 01.11.21 12:46, Idzibear wrote:
> https://www.reddit.com/r/linux/comments/qjyxso/the_515_kernel_has_been_released/hitiykt/
> 
> I just noticed something strange. I'm experimenting with some repurposed
> Desktop-PC to make it maybe into a homelab server.
> 
> I ran Kernel 5.14.10, and I had an idle usage of 19-22 watts. Updated to
> 5.15 and it went to 27-29 watts. Went back to 5.14.10 and it went down
> to 19-22 watts again. WTF?

thx for the report, yeah, sound like a regression. With that much of a
difference I'd suspect it's something that can consume a lot of power if
not sleeping properly, for example the CPU or the GPU. But that's just a
shot in the dark and it's hard to help here with debugging from a
distance (especially without a list of hardware components). With a bit
of luck tools like powertop might be able to debug this (check if the
CPU is sleeping well). But a 'git bisect', like already suggested
Gregkh, would be really the best to find the change that's causing this.

Ciao, Thorsten

#regzbot ^introduced: v5.14..v5.15
#regzbot title: idle power increased from ~20 to ~28 watts