Re: problem in changing from active to passive mode

[Julia Lawall]

On Thu, 28 Oct 2021, Rafael J. Wysocki wrote:

> On Thu, Oct 28, 2021 at 7:57 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> >
> > On Thu, Oct 28, 2021 at 7:29 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> > >
> > > On Thu, Oct 28, 2021 at 7:10 PM Julia Lawall <julia.lawall@xxxxxxxx> 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)

julia