Great article. Thanks. So now the question that perhaps Peter Wallace can answer. If the only Ethernet device is the Mesa 7i92 and there isn't even an eth0 in the /dev folder (there are tty_ and even parallel port) setting the interrupt coalescing off should be mandatory right? John
> -----Original Message----- > From: Nicklas SB Karlsson [mailto:[email protected]] > Sent: September 18, 2026 6:35 PM > To: [email protected] > Subject: Re: [Emc-users] Ethernet send packets jitter > > 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 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
