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

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Date:   Thu, 21 Sep 2023 05:51:16 +0000
From:   "Meng, Li (Jassmine)" <Li.Meng@....com>
To:     "Limonciello, Mario" <Mario.Limonciello@....com>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        "Huang, Ray" <Ray.Huang@....com>
CC:     "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "Fontenot, Nathan" <Nathan.Fontenot@....com>,
        "Sharma, Deepak" <Deepak.Sharma@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Huang, Shimmer" <Shimmer.Huang@....com>,
        "Yuan, Perry" <Perry.Yuan@....com>,
        "Du, Xiaojian" <Xiaojian.Du@....com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Borislav Petkov <bp@...en8.de>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: RE: [PATCH V7 0/7] amd-pstate preferred core

[AMD Official Use Only - General]

Hi Natalenko and Mario:

> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@....com>
> Sent: Thursday, September 21, 2023 4:12 AM
> To: Oleksandr Natalenko <oleksandr@...alenko.name>; Huang, Ray
> <Ray.Huang@....com>; Meng, Li (Jassmine) <Li.Meng@....com>
> Cc: linux-pm@...r.kernel.org; linux-kernel@...r.kernel.org;
> x86@...nel.org; linux-acpi@...r.kernel.org; Shuah Khan
> <skhan@...uxfoundation.org>; linux-kselftest@...r.kernel.org; Fontenot,
> Nathan <Nathan.Fontenot@....com>; Sharma, Deepak
> <Deepak.Sharma@....com>; Deucher, Alexander
> <Alexander.Deucher@....com>; Huang, Shimmer
> <Shimmer.Huang@....com>; Yuan, Perry <Perry.Yuan@....com>; Du,
> Xiaojian <Xiaojian.Du@....com>; Viresh Kumar <viresh.kumar@...aro.org>;
> Borislav Petkov <bp@...en8.de>; Rafael J . Wysocki
> <rafael.j.wysocki@...el.com>
> 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().
> >