[etherlab-users] yet another datagrams UNMATCHED - DC 0.2ms / 5kHz // igb kernel 3.18

Sebastien Blanchet blanchet at iram.fr
Thu Mar 8 19:38:24 CET 2018

Hi Daniel,

It was done in a RTAI kernel-thread.
I had modified the example supplied by IgH Ethercat Master.
I had plugged a digital scope to see the jitter, while checking missing packets 
in dmesg. The goal was just to see how fast EtherCAT was.

best regards
Sebastien BLANCHET

On 03/08/2018 03:54 PM, PAUL-SOFTWARE wrote:
> Hi Sebastien,
> did you implement your code as a kernel-thread or as a rtai-userspace-process getting these results?
> Mit freundlichen Grüßen / Best Regards
> i.A. Daniel Koch
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> -----Ursprüngliche Nachricht-----
> Von: etherlab-users [mailto:etherlab-users-bounces at etherlab.org] Im Auftrag von Sebastien Blanchet
> Gesendet: Mittwoch, 14. Februar 2018 14:37
> An: etherlab-users at etherlab.org
> Betreff: Re: [etherlab-users] yet another datagrams UNMATCHED - DC 0.2ms / 5kHz // igb kernel 3.18
> Hi Jürgen,
> I can share with you some results with the 8139too and r8169 ethercat native drivers when used with RTAI and Preempt-RT kernel.
> - with RTAI and 8139too you can achieve 10 KHz for the ethercat control loop without losing datagram. (tested on Debian 6.0 i386 with RTAI-3.8.1). The computer was a DELL Precision 390 with a Core Duo 2 processor, the slave were 4 Beckhoff Ethercat terminals (EL1004, EL2004, EL3102, EL4102).
> - with Preempt-RT and r8169 you can achieve 1 KHz for the ethercat control loop without losing datagram. (tested on Debian 7.0 i386 with Debian RT kernel).
> At 2 KHz, it does not work very well (sometime you miss datagrams), so the limit is somewhere in the 1...2 KHz range. The computer is a Beckhoff C6920-0040 with the PCIe extension slots, and a Celeron B810 processor. The slaves are 4 Kollmorgen AKD servo drives + 13 other Ethercat terminals from Beckhoff.
> Finally Preempt-RT is slower than RTAI, but it is really easier than RTAI.
> best regards,
> --
> Sebastien BLANCHET
> On 02/13/2018 02:12 PM, Christoph Schroeder wrote:
>> Hi Jürgen,
>> On 02/13/2018 10:01 AM, Jürgen Walter • DATATRONiQ wrote:
>>> I see- will get another Intel card (although compatible ones (kernel driver
>>> e1000, e1000e) seem to be hard to come by these days) and try with anther
>>> kernel driver.
>> I also did some tests with the EtherCAT master, Xenomai and different network
>> devices compatible with the ec_e1000e driver.
>> Test system was a Core-i5 (4th generation) with a Debian Wheezy  (Kernel 3.2)
>> with two slaves attached (Microship LAN9252 in simple Digital I/O mode). I
>> observed the following:
>>    * even with the PREEMPT patch and the native driver ec_e1000e I could barely
>>      achieve 2000Hz cycle rate without frame losses
>>    * with Xenomai I could go over 10000Hz without a problem, but there are some
>>      other issues with Xenomai:
>>        o the EtherCAT master is not ready to use the newer Xenomai 3.x branch and
>>          the Xenomai 2.x branch is not supported anymore
>>        o I got some issues with long term stability on my test system (Kernel
>>          panic) and decided not to use it on a productive system
>>        o I would suggest you go for RTAI since you will also get far more help
>>          from the EtherCAT community, I could barely find other people here who
>>          also use Xenomai with the EtherCAT master
>>    * while using Xenomai I observed, that there is also a huge difference between
>>      different network chips:
>>        o I initially used a card with an Intel 82572EI (introduced Q4'05) and
>>          also tried a Dual port card with an Intel 82571EB (introduced Q3'05)
>>          which had basically the same results on my test system
>>        o the best results I got were achieved with an Intel 82574L (introduced Q2'0)
>> I didn't try RTAI till now, but I think you will get the same or even better
>> results than I got with Xenomai.
>> The cards with Intel 82574L we got were sold as "Intel Gigabit CT Desktop
>> Adapter". The chip will be produced until 2020, so getting a card with it should
>> be no problem. Maybe this will help you.
>> Best regards,
>> Christoph
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