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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Thu, 28 Oct 2021 21:21:02 +0200
Message-ID: <CAJZ5v0jmQgg_DwqSdFsoMd5qV_ZH=cHUJtb372mqv=GSWioRgw@mail.gmail.com>
Subject: Re: problem in changing from active to passive mode
To:     Julia Lawall <julia.lawall@inria.fr>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Doug Smythies <dsmythies@telus.net>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Len Brown <lenb@kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Linux PM list <linux-pm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Thu, Oct 28, 2021 at 9:13 PM Julia Lawall <julia.lawall@inria.fr> wrote:
>
>
>
> On Thu, 28 Oct 2021, Rafael J. Wysocki wrote:
>
> > On Thu, Oct 28, 2021 at 7:57 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> > >
> > > On Thu, Oct 28, 2021 at 7:29 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> > > >
> > > > On Thu, Oct 28, 2021 at 7:10 PM Julia Lawall <julia.lawall@inria.fr> wrote:
> > > > >
> > > > > > Now, for your graph 3, are you saying this pseudo
> > > > > > code of the process is repeatable?:
> > > > > >
> > > > > > Power up the system, booting kernel 5.9
> > > > > > switch to passive/schedutil.
> > > > > > wait X minutes for system to settle
> > > > > > do benchmark, result ~13 seconds
> > > > > > re-boot to kernel 5.15-RC
> > > > > > switch to passive/schedutil.
> > > > > > wait X minutes for system to settle
> > > > > > do benchmark, result ~40 seconds
> > > > > > re-boot to kernel 5.9
> > > > > > switch to passive/schedutil.
> > > > > > wait X minutes for system to settle
> > > > > > do benchmark, result ~28 seconds
> > > > >
> > > > > In the first boot of 5.9, the des (desired?) field of the HWP_REQUEST
> > > > > register is 0 and in the second boot (after booting 5.15 and entering
> > > > > passive mode) it is 10.  I don't know though if this is a bug or a
> > > > > feature...
> > > >
> > > > It looks like a bug.
> > > >
> > > > I think that the desired value is not cleared on driver exit which
> > > > should happen.  Let me see if I can do a quick patch for that.
> > >
> > > Please check the behavior with the attached patch applied.
> >
> > Well, actually, the previous one won't do anything, because the
> > desired perf field is already cleared in this function before writing
> > the MSR, so please try the one attached to this message instead.
> >
>
> Turbostat still shows 10:
>
> cpu0: MSR_HWP_CAPABILITIES: 0x070a1525 (high 37 guar 21 eff 10 low 7)
> cpu0: MSR_HWP_REQUEST: 0x000a2525 (min 37 max 37 des 10 epp 0x0 window 0x0 pkg 0x0)
> cpu0: MSR_HWP_REQUEST_PKG: 0x8000ff00 (min 0 max 255 des 0 epp 0x80 window 0x0)
> cpu0: MSR_HWP_STATUS: 0x00000004 (No-Guaranteed_Perf_Change, No-Excursion_Min)
> cpu1: MSR_PM_ENABLE: 0x00000001 (HWP)
> cpu1: MSR_HWP_CAPABILITIES: 0x070a1525 (high 37 guar 21 eff 10 low 7)
> cpu1: MSR_HWP_REQUEST: 0x000a2525 (min 37 max 37 des 10 epp 0x0 window 0x0 pkg 0x0)
> cpu1: MSR_HWP_REQUEST_PKG: 0x8000ff00 (min 0 max 255 des 0 epp 0x80 window 0x0)
> cpu1: MSR_HWP_STATUS: 0x00000004 (No-Guaranteed_Perf_Change, No-Excursion_Min)
> cpu2: MSR_PM_ENABLE: 0x00000001 (HWP)
> cpu2: MSR_HWP_CAPABILITIES: 0x070a1525 (high 37 guar 21 eff 10 low 7)
> cpu2: MSR_HWP_REQUEST: 0x000a2525 (min 37 max 37 des 10 epp 0x0 window 0x0 pkg 0x0)
> cpu2: MSR_HWP_REQUEST_PKG: 0x8000ff00 (min 0 max 255 des 0 epp 0x80 window 0x0)
> cpu2: MSR_HWP_STATUS: 0x00000004 (No-Guaranteed_Perf_Change, No-Excursion_Min)
> cpu3: MSR_PM_ENABLE: 0x00000001 (HWP)
> cpu3: MSR_HWP_CAPABILITIES: 0x070a1525 (high 37 guar 21 eff 10 low 7)
> cpu3: MSR_HWP_REQUEST: 0x000a2525 (min 37 max 37 des 10 epp 0x0 window 0x0 pkg 0x0)
> cpu3: MSR_HWP_REQUEST_PKG: 0x8000ff00 (min 0 max 255 des 0 epp 0x80 window 0x0)
> cpu3: MSR_HWP_STATUS: 0x00000004 (No-Guaranteed_Perf_Change, No-Excursion_Min)

Hmmm.

Is this also the case if you go from "passive" to "active" on 5.15-rc
w/ the patch applied?