Re: [Bug 219984] New: [BISECTED] High power usage since 'PCI/ASPM: Correct LTR_L1.2_THRESHOLD computation'

[Bjorn Helgaas <helgaas@kernel.org>]

[bugzilla reporter bcc'd]

Bisected to https://git.kernel.org/linus/7afeb84d14ea

I'll take a look; including linux-pci for completeness and in case
others are interested.

On Sun, Apr 06, 2025 at 03:11:54PM +0000, bugzilla-daemon@kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=219984
> 
>             Bug ID: 219984
>            Summary: [BISECTED] High power usage since 'PCI/ASPM: Correct
>                     LTR_L1.2_THRESHOLD computation'
>           Reporter: sergey.v.dolgov@gmail.com
>         Regression: No
> 
> Created attachment 307924
>   --> https://bugzilla.kernel.org/attachment.cgi?id=307924&action=edit
> Bisection log
> 
> I have been observing increased power consumption on my HP Spectre x360
> Convertible 15-df1xxx (CoffeeLake) since kernel 6.1. Bisection revealed a
> regression in commit 7afeb84d14eaaebb71f5c558ed57ca858e4304e7 (PCI/ASPM:
> Correct LTR_L1.2_THRESHOLD computation). This still affects the mainline. 
> 
> With the original kernel 6.14, turbostat shows that the CPU sticks to Pkg%pc3
> more than 50% of the time, resulting in a discharge rate of 3.52 W reported by
> powertop during an idle empty plasma6 session with screen off.
> 
> After reverting 7afeb84d14eaaebb71f5c558ed57ca858e4304e7 and recompiling the
> kernel with the same config, Pk%pc10, CPU%LPI and SYS%LPI residencies are all
> above 80% during the same session, and "The battery reports a discharge rate of
> 1.35 W."
> 
> The two kernels above had no nvidia drivers to avoid tainting. However,
> compiling also the proprietary nvidia modules reduces the idle power
> consumption further to 796 mW.
> 
> Could you please revert 7afeb84d14eaaebb71f5c558ed57ca858e4304e7 upstream? Or,
> at least, to switch between the two encode_l12_threshold algorithms selectively
> depending on the system.