Re: [Xenomai-help] Beginner's question / testsuite / latency

[Jan Kiszka <jan.kiszka@domain.hid>]

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Julien Heyman wrote:
> Hi,
> 
> I am currently trying to evaluate Xenomai, and my current setup is :
> VIA C3 533Mhz processor, Kubuntu 6.06 Linux distribution.
> I am using Xenomai-2.1.0 over a 2.6.17.4 kernel.

General advice: especially when starting new, try to pick the latest
version, at least the latest from the preferred series (here 2.1.2). But
2.2 is even better. :)

> When I run the latency part of the testsuite (in a console under KDE), I
> get
> results that I cannot understand, so I probably did something wrong
> (execution trace included below).
> I get reasonable values during the first seconds, then all of a sudden
> latencies begin to rise, continuously, to very large values.
> - I did check that DMA transfer is activated on my HD.
> - I did select "Enable SMI workaround" + "Globally disable SMI" in the
> Xenomai
> options while configuring the kernel.
> - I have disabled power management at BIOS level and disabled ACPI support
> and
> CPU frequency scaling during kernel configuration.
> - I checked that I don't have anything called "legacy USB" in my BIOS. I do
> have an "OnChip USB" option enable in the BIOS though.
> 
> Any advice would be appreciated !

Maybe it's related to some other weird on-chip hardware. At work we run
Xenomai only on a head-less VIA C3 box, i.e. without X. No problems so
far. I would suggest to try stopping X and run the test from the text mode.

A further tool to analyse such effects in details is the I-pipe tracer.
It's an additional patch you have to apply to your kernel (see
http://download.gna.org/adeos/patches/v2.6/i386/tracer). Enable this
I-pipe option, rebuild your kernel, and start the latency test with -f.
The test will then capture on every new worst-case delay a backtrace to
/proc/ipipe/trace/frozen. You may want to play with the number of
back-trace points or the verbose mode (see /proc/ipipe/trace/*) even
after the capturing.

Unless you find something obvious immediately, feel free to post a
backtrace that includes the problematic delay period before the freeze
(compress when too large).

Jan


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