Linux 5.11 Is Regressing Hard For AMD Performance With Schedutil

[elatllat]

...setting the governor to static performance for all cores.
This has been my "default behavior" for almost a decade...

Even for boxes that mostly Idle i have a script to use performance when there is load.

[Anarchy]

Will someone please make a gofundme account so that we can fund AMD's Linux kernel support!!!

It's 2020 people, wtf?! :-|

[milkylainen]

Cpufreq and governors has been in the making for.. a very long time.
Schedutil, ondemand etc. All have had tons of caveats and whatnots of strange behavior.
It has resulted in me just turning off cpufreq in my kernels or setting the governor to static performance for all cores.
This has been my "default behavior" for almost a decade.
I just don't trust this subsystem one iota.

[MadCatX]

Michael
Michael Larabel, saving the linux kernel performance once again! Companies whom you've saved millions of dollars in power expenses should pay you in gold. Anyway, enjoy my measly Paypal tip and merry xmas!

[ssokolow]

Why bother testing crap for 0.1W of power savings?
Those governors should be warned of and shunned, they severely hurt enduser Linux experience for often nonexistent power savings.

That's why it's important to test them. To make sure bad defaults get called out.

[zerothruster]

"The CPU power consumption of the EPYC 7702 was lower with Linux 5.11 Schedutil but on a performance-per-Watt basis was behind the Linux 5.10 efficiency."

Looks as if schedutil is really only concerned with minimising overall power consumption, which for data centres is perhaps a useful target, but otherwise only (sometimes) useful for laptops when they are running on battery power (or, perhaps, to stop them overheating which might be a consideration for intel hardware). No doubt developers with modern intel hardware can care about the reduced performance per watt (assuming it does also apply to intel and is not an "oh, we accidentally screwed up performance on amd, oh dear" case).

Michael, thanks for doing this. At least I can compile my own kernels. As you said, for distros the slowness will be a bad move if it doesn't get fixed.

[aufkrawall]

I disagree, default test conditions should be default literally, unless you benchmark specific quirk like diffrent compiler or diffrent governor or something else.

Why bother testing crap for 0.1W of power savings?
Those governors should be warned of and shunned, they severely hurt enduser Linux experience for often nonexistent power savings.

[cl333r]

AMD should really pay you, Michael

No, you're breathtaking!

[ThoreauHD]

They really should hire Michael, if they aren't going to stand up a proper kernel dev team. Better to beat down the nails with what you got, than get constantly blindsided by brokeness.

[alberto-pv]

AMD should really pay you, Michael