Very slow and inconsistent internal network speed (between, VM's on the same host) for FreeBSD 11.0+ as guest on, XCP-ng/XenServer

[Roger Pau Monné]

On Mon, Jun 24, 2019 at 10:24:09PM +0200, Christian M wrote:
> Thanks for your input Bjarne.
> 
> Previously I tested with iperf2, but I have made som tests with iperf3 now
> also and noticed there are a lot of "Retr" (TCP retries) in some cases.
> Went back here to your post and saw that your results also showed a lot of
> retries in some cases. My new tests showed similar results to yours
> (although not nearly as hi throughput as you have). When Linux is client
> the retries are 0, with FreeBSD as client the number is > 0.

Can you figure out what caused those retries? Wrong MTU, bad
checksums?

> I'm not sure
> if our numbers are considered high though, and something that actually is a
> problem? Although, on a internal network with no external factors like
> interference, I feel this should always be 0 no matter what?

If properly configured yes, there should be no retries when doing
intra-VM connections.

Thanks, Roger.