[etherlab-users] general performance questions

[martin troxler]

Hi George 

We use Ubuntu 10.04 with RT_PREEMT kernels 2.6.31.11-rt or 2.6.33.9-rt
(We started with 8.04 and 2.6.24, too) 
Our system works on a recent Core2Duo, has an update cycle of 250µs and
one domain with up to 1kB (5-20 servo drives running in cyclic position
mode).
The CPU load of the realtime process is below 15%. 

Do you use the generic driver or the patched ethercat e1000 driver? 
If you have to use the generic driver, the interrupt throttling of the
e1000 should be disabled! 
Regards 
Martin

>>> Georg Sassen <gsassen at batalpha.com> 11/5/2011 17:45 >>>
Hi,

since we are trying to optimize our systems, some general questions
arise again, as perhaps the answers have changed over the time. We are
using Ubuntu 8.04 with RT patches, with Ubuntu stock kernel 2.6.24-rt,
and EtherCAT master from about a month ago.

1) Which Ethernet card is best suited for the EtherCAT master when
using
large process data and fast EtherCAT cycles? We had some problems with
the E1000: When using lots (>100) of domains, we got many EtherCAT
datagram timeouts and the process EtherCAT-OP used nearly all of the
CPU
(1.86GHz Celeron). This got better when we put in a cheap 8139 card -
but we still see these errors from time to time and don't really know
where they come from.

2) Is using the RT PREEMPT kernel still ok? I don't read much about
other people using it here, most seem to be using RTAI?
If using RT PREEMPT, are there any special options to be set in the
system or are the default settings ok?

3) Would changing to a newer kernel (like 2.6.31-rt with Ubuntu 10.04)
make a difference performance-wise?

Thanks

   Georg


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