Re: Frequency not returning to fixed value after AVX workload

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

On Mon, 2019-10-14 at 21:11 +0000, Hernandez Lopez, Fabiola wrote:
> How do you measure the frequency?
Do whatever you are doing to get to your problem state and while doing
the test run in another window:

#turbostat

Attach the output.

Thanks,
Srinivas

> With lscpu.
> 
> What exactly do you do to get the expected frequency back?
> A script is used that sets the frequency with
> /sys/devices/system/cpu/cpu*/cpufreq/scaling_setspeed
> 
> Is the target frequency in the turbo range?
> No, the target frequency is the same as the base processor frequency:
> 2.4GHz. The max turbo frequency for this CPU si 3.9 GHz.
> This has been tested with turbo boost enabled and disabled. 
> 
> This behavior is very sporadic: < 10%
> 
> Thanks,
> Fabiola
> 
> -----Original Message-----
> From: Rafael J. Wysocki [mailto:rjw@rjwysocki.net] 
> Sent: Monday, October 14, 2019 4:45 AM
> To: Hernandez Lopez, Fabiola <fabiola.hernandez.lopez@intel.com>
> Cc: linux-pm@vger.kernel.org; Srinivas Pandruvada <
> srinivas.pandruvada@linux.intel.com>
> Subject: Re: Frequency not returning to fixed value after AVX
> workload
> 
> On Friday, October 11, 2019 7:45:55 PM CEST Hernandez Lopez, Fabiola
> wrote:
> > Hi,
> > 
> > We are seeing an unexpected behavior after applying AVX workloads. 
> > After setting the CPU frequency to a fixed value with CPU Freq - 
> > userspace governor and applying heavy AVX workloads, the CPU
> > frequency 
> > is decreased (as expected) but it never returns to the previously
> > established value.
> 
> How do you measure the frequency?
> 
> > This does not happen on all cores, only on a single core. The only
> > way 
> > to return to the desired frequency is by setting it through the 
> > command line again.
> 
> What exactly do you do to get the expected frequency back?
> 
> > We are wondering how can this change in frequency happen.
> 
> Is the target frequency in the turbo range?
> 
> 
>