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From: "Hernandez Lopez, Fabiola" <fabiola.hernandez.lopez@intel.com>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Subject: RE: Frequency not returning to fixed value after AVX workload
Date: Mon, 14 Oct 2019 21:11:57 +0000
Message-ID: <67737C20FC7E4D44B44817ABFA5B1DCE6EC020E9@CRSMSX104.amr.corp.intel.com> (raw)
In-Reply-To: <3340378.NBreQbsDsf@kreacher>

How do you measure the frequency?
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?




  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-11 17:45 Hernandez Lopez, Fabiola
2019-10-14  9:44 ` Rafael J. Wysocki
2019-10-14 21:11   ` Hernandez Lopez, Fabiola [this message]
2019-10-14 21:23     ` Srinivas Pandruvada
2019-10-23 18:26       ` Hernandez Lopez, Fabiola

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