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

[Karl Pielorz]

--On 04 July 2019 10:59 +0200 Christian M <christian.marcos at gmail.com> 
wrote:

> From my tests I found that 10.4-RELEASE was as fast as you could expect
> (>10Gbit/s), then something changed in 11.0-RELEASE and carried on and got
> even worse in 12.0-RELEASE. Would it not be a good idea to begin there
> (10.4 -> 11.0), and try to identify what changes could impact the
> performance drop so significantly? This is perhaps a much harder task than
> it sounds for someone that knows nothing about what changes was made, and
> how difficult it would be to identify what changes actually could be
> relevant. Just a thought.

Looking at FreeBSD source - there doesn't appear to be a lot that has 
changed (at least in sys/xen) even from 10.4 through to 12 - certainly 
nothing networking I can see (unless I'm using svn log 'wrong', or there's 
other xen stuff within FreeBSD I should be looking at).

So this could be caused by other changes that have happened with the OS 
over that time.

If I get time - I'll see if I can follow the thread and setup a similar 
test system here, to be fair we've not had a performance issue with Xen 
Networking (as nothing we do needs the performance - yet). We've been much 
more plagued by packet weirdness which virtio has fixed.

Even if I can re-create things here - it may only be an "oh yeah, so it is" 
moment.

-Kp