Yes IRQ coalescing seems like a problem. Read here https://www.ibm.com/docs/en/aix/7.1.0?topic=options-interrupt-coalescing then a packet is received it wait for more packets up to a maximum time before interrupt is generated.
If have been able to disable other internet packets only one packet is expected and it make no sense to wait for more. But even though timer add some extra delay it does not explain why receive sometimes take a lot longer time. Nicklas Karlsson tor 2026-09-17 klockan 07:28 -0700 skrev Peter Wallace: > 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 > > > > > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > Peter Wallace > Mesa Electronics > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
