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Date: Thu, 12 Nov 2015 09:20:01 +0100
From: =?windows-1252?Q?St=E9phane_ANCELOT?= <sancelot@free.fr>
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Subject: Re: [Xenomai] intel turbo boost
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To: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Cc: "xenomai@xenomai.org" <xenomai@xenomai.org>

On 08/11/2015 12:26, Gilles Chanteperdrix wrote:
> On Wed, Nov 04, 2015 at 01:30:32AM +0100, Gilles Chanteperdrix wrote:
>> On Thu, Sep 03, 2015 at 09:00:36AM +0200, St=E9phane ANCELOT wrote:
>>> Hi,
>>>
>>> Do you think I can use the Intel integrated turbo boost mode, without
>>> problems.
>>>
>>> I have this nice processor :
>>> http://ark.intel.com/fr/products/76308/Intel-Core-i5-4300U-Processor-3M=
-Cache-up-to-2_90-GHz
>> Just experimented this, the turbo mode is a problem for applications
>> which rely on a precise relation between the actual count of cpu
>> cycles of a busy loop and the time. The sched_quota falls under that
>> category and simply does not work reliably when turbo mode is
>> enabled. Fortunately, it is possible to turn off turbo mode. For
>> that, in the kernel configuration
>> - enable CPU_FREQ
>> - choose performance mode by default
>> - enable intel pstate driver
>> - echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
>>
>> Other than that, turbo mode does not seem to break the latency,
>> which would mean that the tsc frequency does not change with turbo
>> mode.
> Turbo mode also breaks the autotune feature. So, on a machine with
> turbo mode, autotune should be triggered after writing to the /proc
> file.
>
Hi,
You can disable turbo mode, in bios cpu settings . Writting to the=20
no_turbo file is not permitted, but equals 1.
How do you trig autotune ?
Regards,
Steph