From: Clark Williams <williams@redhat.com>
To: Stefan Jenisch <stefan.jenisch@gmail.com>
Cc: linux-rt-users@vger.kernel.org
Subject: Re: Difficulties with cyclictest on AMD CPU
Date: Mon, 28 Apr 2014 09:24:24 -0500 [thread overview]
Message-ID: <20140428092424.71629805@sluggy> (raw)
In-Reply-To: <535CE374.7050907@gmail.com>
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On Sun, 27 Apr 2014 13:01:08 +0200
Stefan Jenisch <stefan.jenisch@gmail.com> wrote:
>
> So my guess is that the cpu goes into some sort of powersave mode from
> time to time. The wakeup from these powersave state results in
> latencies. Currently I am looking for a proper solution to this problem
> and what I have tried so far:
>
> - BIOS upgrade
> - Upgraded to linux-3.10.12-rt25
> - Disabling all sort of powersave modes in the kernel config
> - Activated cpufreq-performance (which seems to be ignored anyway)
> - Searched the BIOS for any powersave modes to deactivate (none found)
>
> I got rather clueless on what else to try! Does anyone has a helping
> hint on how to solve this one???
>
> With many thanks in advance,
>
> Stefan J.
>
Did you get this message when starting cyclictest?
# /dev/cpu_dma_latency set to 0us
That's a hack that is supposed to prevent the system from entering
deeper C-states than C-state 0.
What version of rt-tests are you running?
Clark
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prev parent reply other threads:[~2014-04-28 14:24 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-27 11:01 Difficulties with cyclictest on AMD CPU Stefan Jenisch
2014-04-28 14:24 ` Clark Williams [this message]
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