FreeBSD 13 on bhyve freezes under load

[Christian Stærk]

Hello,

I recently upgraded one of my bhyve guests to FreeBSD 13.0-RELEASE. The 
host is running 12.2-RELEASE-p4.

The guest in question is used for building packages with poudriere and 
is always the first one to get upgraded to new releases.

The guest freezes consistently every time poudriere tries to build the 
thunderbird package. Although it is not a complete freeze. It responds 
to ping and programs like top and systat continue updating. However, all 
I/O operations seem to hang.

systat looks like this when it happens: 
https://borderworlds.dk/~xi/FreeBSD%2013%20frozen.png 
<https://borderworlds.dk/~xi/FreeBSD%2013%20frozen.png>

What is the best way to debug this?

Best regards
Christian