virtio Network interface attached to a vm guest causes jitter on an ixl SR-IOV NIC

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virtio Network interface attached to a vm guest causes jitter on an ixl SR-IOV NIC

Tom Smyth
Hello,

Running 6.5 Stable and 6.5 Current 5/07/2019  on a Proxmox 5.3 VM,

if you are running  avm with  a virtio NIC and an SR-IOV  ixl nic (40G
Intel nic) attached
you can encounter pretty severe jitter on pings to and from the ixl NIC,
i.e. minimum ping of 0.390 ms  and then it can jump to  55ms, up to 400ms
very regularly >30% of ping responses suffering high jitter,

removing the virtio NIC (which was intended as a management device only)
improved our jitter considerably.  with only 12 abnormal pings   out of 652
pings,

--- ping statistics ---
652 packets transmitted, 652 packets received, 0.0% packet loss
round-trip min/avg/max/std-dev = 0.141/4.107/428.184/30.197 ms

I hope this info helps other OpenBSD SR-IOV users...
--
Kindest regards,
Tom Smyth.