Re: [Xenomai-help] Results of xenomai's latency test vs. RTAI's

["M. Koehrer" <mathias_koehrer@domain.hid>]

Hi everybody,

I have repeated the test using a parallel stress test (dd if=/dev/sda of=/dev/null, I have
a SATA harddisk).
The results are that my RTAI latency of 4µs is not valid, here the latency is about 26µs.
However, xenomai shows a higher latency of about 40µs.
The interesting thing is, that without load RTAI seems to run very long in a very 
low latency region, at the same setup xenomai shows large latencies earlier.


Well, I have repeated these tests on a different PC that has a server mainboard and 
a Pentium D 4 (real dual core) CPU.
The results (measured under load) are much better here:
RTAI shows a latency of about 6µs
Xenomai shows a latency of about 10µs.
Both values are acceptable, however I wonder where the difference comes from?

Thanks for all the feedback on that issue!

Regards

Mathias
> > I have rebuild my system using V2.2.4 of xenomai.
> > Also, I had a look to reuse the kernel configuration from the 2.4.33 RTAI
> system.
> > However, the results are more or less the same.
> > The only kernel module I have loaded is the "tg3" network driver, the
> chipset of the 
> > PC (ICH6) is supported by the SMI detection and it is activated.
> > 
> 
> On such hw, you may want to enable the following:
> CONFIG_BLK_DEV_IDEDMA_PCI=y
> CONFIG_BLK_DEV_IDEDMA=y
> CONFIG_IDEDMA_AUTO=y
> 
> > I have enclosed my kernel configuration, perhaps this can help to identify
> an issue.
> > I do not have X11 running, it is a text-mode only system that is
> controlled via telnet from
> > another PC.
> > 
> > I'll try to do a stress test on the RTAI system as well.
> > 
> 
> You could try running RTAI 3.3 over 2.6.17 with the very same config
> file too (Xenomai opts aside, of course), so you could rule out any
> configuration problem if the gap still exists.


-- 
Mathias Koehrer
mathias_koehrer@domain.hid


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