Unfortunately for mu turn off IRQ coalescing does not seem to solve the problem.
Running: /sbin/ethtool -c enp10s0 report among other things: rx-usecs: 0 rx-frames: 1 rx-usecs-irq: n/a rx-frames-irq: n/a tx-usecs: 0 tx-frames: 1 tx-usecs-irq: n/a tx-frames-irq: n/a All other parameters are n/a I have another card I350 which should be able to do both hardware time stamp of both sent and received frames. This would remove uncertainties about time stamping of messages. It should also be able to send messages with time trigger. Then if possible to synchronize with call of update function jitter within servo period would make no difference at all, messages transmitted equally spaced exactly at the times intended. Regards Nicklas Karlsson fre 2026-09-18 klockan 20:33 -0700 skrev John Dammeyer: > 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 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
