On Thu, 17 Sep 2026, andy pugh wrote:
On Wed, 16 Sept 2026 at 21:20, Nicklas SB Karlsson <[email protected]> wrote:
Running Linuxcnc and send receive Ethernet jitter is small for most packets but
sometimes there is delay of well
above on millisecond, running for maybe a minute or so worst case is between
6...7 milliseconds.
Maybe you need to disable IRQ coalescing? It's mentioned briefly in
the hm2_eth docs, but also might be relevant to EtherCAT.
https://linuxcnc.org/docs/stable/html/man/man9/hm2_eth.9.html
(It's at least a google-able phrase for further investigation)
At least for hm2_eth, basic Network latency improvement methods are:
On Intel (and some less common others like broadcom), disable IRQ coalescing
On Realtek, install the DKMS driver (the stock Linux driver has multi-ms
random latencies)
On all, use isolcpus (or whatever the newer scheme is called) to isolate the
last CPU, and then pin the Ethernet IRQ to that CPU.
Use the latest kernel (I have a test system that always got random timeouts,
say once a day, with 6.x kernels, this was totally fixed with a 7.X kernel
--
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
? George Fitch, Atlanta Constitution Newspaper, 1912
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Peter Wallace
Mesa Electronics
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