linux-kernel - RE: [RFC/RFT][PATCH] cpufreq: intel_pstate: Accept passive mode with HWP enabled

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Date:   Sun, 31 May 2020 14:38:45 -0700
From:   "Doug Smythies" <dsmythies@...us.net>
To:     "'Srinivas Pandruvada'" <srinivas.pandruvada@...ux.intel.com>,
        "'Rafael J. Wysocki'" <rjw@...ysocki.net>
Cc:     "'LKML'" <linux-kernel@...r.kernel.org>,
        "'Len Brown'" <len.brown@...el.com>,
        "'Peter Zijlstra'" <peterz@...radead.org>,
        "'Giovanni Gherdovich'" <ggherdovich@...e.cz>,
        "'Francisco Jerez'" <francisco.jerez.plata@...el.com>,
        "'Linux PM'" <linux-pm@...r.kernel.org>
Subject: RE: [RFC/RFT][PATCH] cpufreq: intel_pstate: Accept passive mode with HWP enabled

On 2020.05.31 12:29 Srinivas Pandruvada wrote:
> On Sun, 2020-05-31 at 11:59 -0700, Srinivas Pandruvada wrote:
>> On Sun, 2020-05-31 at 11:06 -0700, Doug Smythies wrote:
>> > Hi Srinivas,
>> >
>> > Thanks you for your quick reply.
>> >
>> > On 2020.05.31 09:54 Srinivas Pandruvada wrote
>> > > On Sun, 2020-05-31 at 09:39 -0700, Doug Smythies wrote:
>> > > > Event begins at 17.456 seconds elapsed time.
>> > > > Previous event was about 107 milliseconds ago.
>> > > >
>> > > > Old min ; new min ; freq GHz; load % ; duration mS
>> > > > 27      ; 28      ; 4.60    ; 68.17  ; 10.226
>> > > > 28      ; 26      ; 4.53    ; 57.47  ; 10.005
>> > >
>> > > Seems you hit power/thermal limit
>> >
>> > No.
>> >
>> > I am nowhere near any power limit at all.
>> > I have meticulously configured and tested the thermal management of
>> > this computer.
>> > I never ever hit a thermal limit and have TDP set such that the
>> > processor
>> > temperature never exceeds about 75 degrees centigrade.
>> >
>> > There should never be throttling involved in these experiments.
>> > I can achieve throttling when compiling the kernel and with
>> > torture test mode on the mprime test (other CPU stressors,
>> > including my own, are not as good at generating heat as
>> > mprime).
>> >
>> > This system can run indefinitely at 99.9 watts processor package
>> > power.
>> > Example (turbostat, steady state, CPU freq throttled to 4.04 GHz):
>> >
>> > doug@s18:~$ sudo ~/turbostat --Summary --quiet --show
>> > Busy%,Bzy_MHz,PkgTmp,PkgWatt,GFXWatt,IRQ --interval 12
>> > Busy%   Bzy_MHz IRQ     PkgTmp  PkgWatt GFXWatt
>> > 100.21  4045    72231   66      99.93   0.00
>> > 100.21  4043    72239   65      99.92   0.00
>> >
>> > > Is this some Lenovo system?
>> >
>> > No. The web page version of my original e-mail has
>> > a link to the test computer hardware profile.
>> >
>> > The motherboard is ASUS PRIME Z390-P.
>> >
>>
>> OK, this seems a desktop system.
>>
>> > > If you disable HWP you don't see that?
>> >
>> > Correct.
>> >
>> > > What is the value of
>> > > cat /sys/bus/pci/devices/0000\:00\:04.0/tcc_offset_degree_celsius
>> >
>> > ? "No such file or directory"
>> >
>> > > cat /sys/class/powercap/intel-rapl-mmio/intel-rapl-
>> > > mmio:0/constraint_0_power_limit_uw
>> You may not have
>> CONFIG_INT340X_THERMAL=y

I have:
CONFIG_INT340X_THERMAL=m

>>
>> What is
>> #rdmsr 0x1a2

>From the turbostat startup spew of stuff
(also in a link on the web page version of the e-mail):

MSR_IA32_TEMPERATURE_TARGET: 0x0064100d (100 C)

Or manually now:

root@s18:/home/doug/prime95# rdmsr 0x1a2
64100d

>>
>> Try changing energy_perf_bias and see if it helps here.

Yes, that is a test I meant to do, and should have done.

No, it doesn't help.

>>
> Also if
> MSR 0x1FC bit 19 is 0, change to 1.
> 

Ya, I have always found documentation on 0x1FC somewhat lacking.
Anyway, the bit is already 1.
Is the bit EE_TURBO_DISABLE?
Anyway, I tried that bit as 0, and it didn't help.

> Thanks,
> Srinivas
> 

... Doug