From: Tim Sander <tim@krieglstein.org>
To: Matthias Fuchs <mfuchs@ma-fu.de>
Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
Subject: Re: 3.12.6-rt9 on AM335x (armv7)
Date: Tue, 07 Jan 2014 23:58:57 +0100 [thread overview]
Message-ID: <10785809.PZUZGWPMgY@hydra> (raw)
In-Reply-To: <52CC6F94.6070906@ma-fu.de>
Hi Matthias
> without hackbench and frieds (idle system) I get a max. latency of about
> 4ms. Running hackbench (default arguments, -l 1000), it still increases up
> to 5ms:
>
> ...
> # Total: 000000193
> # Min Latencies: 00024
> # Avg Latencies: 00205
> # Max Latencies: 05058
> ...
>
> The obvious PM stuff is disabled. No dynamic frequency scaling, etc.
> Really weired stuff. I already mentioned the 3.2 system with the same CPU in
> the OSADL lab. It comes with max. latency of 118us. So I really expect
> something similiar.
Yeah 118 µs should be the right ballpark, while still a little high for my
taste. All cortex a8 seem to have rather high latency. The A9's seem much
better in this respect.
Have you seen the following:
https://www.osadl.org/Realtime-Preempt-Kernel.kernel-rt.0.html#latencyfighting
Cyclictest has tracing support which might help finding the cause of the long
latency.
Best regards
Tim
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next prev parent reply other threads:[~2014-01-07 22:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-01 16:37 3.12.6-rt9 on AM335x (armv7) Matthias Fuchs
2014-01-06 19:48 ` Matthias Fuchs
2014-01-07 8:38 ` Tim Sander
2014-01-07 21:20 ` Matthias Fuchs
2014-01-07 22:58 ` Tim Sander [this message]
2014-01-07 23:46 ` Pavel Vasilyev
2014-01-08 8:08 ` Matthias Fuchs
2014-01-08 8:06 ` Matthias Fuchs
2014-02-07 16:07 ` Sebastian Andrzej Siewior
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