RE: [PATCH V7 0/7] amd-pstate preferred core

[Meng, Li (Jassmine)]

[AMD Official Use Only - General]

Hi Natalenko and Mario:

> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@xxxxxxx>
> Sent: Thursday, September 21, 2023 4:12 AM
> To: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>; Huang, Ray
> <Ray.Huang@xxxxxxx>; Meng, Li (Jassmine) <Li.Meng@xxxxxxx>
> Cc: linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> x86@xxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; Shuah Khan
> <skhan@xxxxxxxxxxxxxxxxxxx>; linux-kselftest@xxxxxxxxxxxxxxx; Fontenot,
> Nathan <Nathan.Fontenot@xxxxxxx>; Sharma, Deepak
> <Deepak.Sharma@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Huang, Shimmer
> <Shimmer.Huang@xxxxxxx>; Yuan, Perry <Perry.Yuan@xxxxxxx>; Du,
> Xiaojian <Xiaojian.Du@xxxxxxx>; Viresh Kumar <viresh.kumar@xxxxxxxxxx>;
> Borislav Petkov <bp@xxxxxxxxx>; Rafael J . Wysocki
> <rafael.j.wysocki@xxxxxxxxx>
> Subject: Re: [PATCH V7 0/7] amd-pstate preferred core
>
> On 9/20/2023 14:34, Oleksandr Natalenko wrote:
> > Hello.
> >
> > On středa 20. září 2023 18:56:09 CEST Mario Limonciello wrote:
> >>> When applied on top of v6.5.3 this breaks turbo on my 5950X after
> suspend/resume cycle. Please see the scenario description below.
> >>>
> >>> If I boot v6.5.3 + this patchset, then `turbostat` reports ~4.9 GHz on core
> 0 where `taskset -c 0 dd if=/dev/zero of=/dev/null` is being run.
> >>>
> >>> After I suspend the machine and then resume it, and run `dd` again,
> `turbostat` reports the core to be capped to a stock frequency of ~3.4 GHz.
> Rebooting the machine fixes this, and the CPU can boost again.
> >>>
> >>> If this patchset is reverted, then the CPU can turbo after
> suspend/resume cycle just fine.
> >>>
> >>> I'm using `amd_pstate=guided`.
> >>>
> >>> Is this behaviour expected?
> >>
> >> To help confirm where the issue is, can I ask you to do three
> >> experiments with the patch series applied:
> >>
> >> 1) 'amd_pstate=active' on your kernel command line.
> >
> > The issue is reproducible. If I toggle the governor in cpupower to
> `powersave` and back to `performance`, boost is restored.
> >
> >> 2) 'amd_pstate=active amd_prefcore=disable' on your kernel command
> line.
> >
> > The issue is not reproducible.
> >
> >> 3) 'amd_pstate=guided amd_prefcore=disable' on your kernel command
> line.
> >
> > The issue is not reproducible.
> >
> > I should also mention that in my initial configuration I use
> `amd_pstate=guided` and `schedutil`. If I switch to `performance` after
> suspend-resume cycle, the boost is restored. However, if I switch back to
> `schedutil`, the freq is capped.
> >
> > Does this info help?
> >
>
> Yeah, it matches my expectations for this issue you reported.
> Thanks!
>
> Jassmine can dig into a fix for another spin of this series.
[Meng, Li (Jassmine)]
Thank you very much!
I will fix this issue in the next patches.
>
> >> Looking through the code, I anticipate from your report that it
> >> reproduces on "1" but not "2" and "3".
> >>
> >> Meng,
> >>
> >> Can you try to repro?
> >>
> >> I think that it's probably a call to amd_pstate_init_prefcore()
> >> missing from amd_pstate_cpu_resume() and also
> amd_pstate_epp_resume().
> >