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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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  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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