performance improvement suggestions

I take it this PC is connected to the internet.
Can you advise the ip address of your gateway/router?

It appears that both your NIC's have an address in the 10.10.10.X range and I'm assuming the 7i76e is 10.10.10.10. Your network IP address should be in a different range. eg 192.168.1.X I don't run a static IP address for that network and allow it to be allocated by the DHCP server.

So I think your machine may become confused when it looks for your 7i76e becasue it does not know which NIC to look from.

I did discuss this in a recent video which may help. (about 16 min in)

I can move the address range on the Mesa boards using mesaflash (I've been playing around already because they would need different addresses anyway from 10.10.10.10)

pcw mentioned that with two NICs you may need to modify the ini / HAL file

any merit in limiting the network ip address range via subnet mask?

auto enp2s0
iface enp2s0 inet static
address 10.10.10.11/24
hardware-irq-coalesce-rx-usecs 0

auto enp3s0
iface enp3s0 inet static
address 11.10.10.11/24
hardware-irq-coalesce-rx-usecs 0

wiki.debian.org/NetworkConfiguration

.... well, i dont know what ive done but it now works with a 1000000 servo period

(I've fiddled with a bit..... rebooted with original rt kernel
+ changed the interfaces file as above .... something worked....

I was wondering if there was a way to lower the priority of applications in linux (such as firefox), as it weems that my latency rises from ~20K to 52K when opening a youtube clip.

is there any merit in lowering the application priorities / increasing those priorities used by linuxcnc

is that not the purpose of subnetting

second metwork address was
address 11.10.10.11/24

www.davidc.net/sites/default/subnets/subnets.html

changed them to
address 11.10.10.11/28 to limit the address range on each of the NIC ports. 1-14

I think where Tommy is coming from is that the private IP address ranges that are not routed on the internet are
192.168.X.X
10.X.X.X.X
172.16.X.X

You need to ensure your internal IP's are in one of these ranges.

So one day you might need to get to something on the public 11.10.10.X IP address range and you won't be able to.
Why don't you go with
10.10.10.X and 10.10.11.X ?

Just a bit further on this. A very long time ago in a more generous and slower era, I ran a web server via a dedicated dialup link!
At that time, the ISP allocate me a whole /26 range so I had 64 registered IP addresses. I did have to do a bit of fancy subnetting back then, but for home use, its much cleaner to subnet by different ranges (eg 192.168.1/24 10.10.10/24 and 172.16.1/24.

I always use DHCP wherever possible and if a machine benefits from a fixed IP address eg, a printer or security camera, I use a DHCP address reservation for it as its much easier to manage the network that way and I always know where my printer is!