On Thu, 20 May 2021, Christoph Mathys wrote:
Date: Thu, 20 May 2021 09:36:46 +0200
From: Christoph Mathys <eraserix@xxxxxxxxx>
To: linux-rt-users@xxxxxxxxxxxxxxx
Subject: Network latency on 5.4 and 5.10
Hi all!
I'm trying to upgrade from 4.9-rt to 5.4-rt (also tried 5.10). I'm having a
hard time getting networking to perform on the same level as 4.9 (latency
wise). We drive an EtherCAT bus at 4kHz using the igb driver.
On 4.9, I just had to disable coalescing on the nic and increase the priority
of the irg threads and it performed as desired (more or less according to [1]
for 3.6+ without task pinning)
Doing the same on 5.4/5.10 does not seem to suffice any more. I get a lot of
warnings from our code that packets have not been sent or received in time
for the next control loop iteration.
Any suggestions on what I could try to improve the nic response?
Thanks!
Christoph
[1]
https://www.osadl.org/Real-time-Ethernet-UDP-worst-case-roun.qa-farm-rt-ethernet-udp-monitor+M514ebdffa90.0.html
No, help but I have seen the same thing with our real time UDP connected
Ethernet devices. 4.X seems to have much better latencies that 5.X. I've tried
up to 5.11.
Peter Wallace
Mesa Electronics
