Perfomance issue between 1.5.8-1ubuntu1.1 (xenial) and 1.6.7-1ubuntu2.1 (bionic)

[Ralf Hildebrandt]

We're using unbound on our four proxy servers (and a hand-compiled,
current version of squid), which channel all outbound HTTP/HTTPS traffic.

Naturally, these machine do a lot of resolving.

Recently I upgraded the OS from xenial to bionic, and while everything
was working as expected I noticed a significant increase in the DNS
query times on those proxies.

Before the update (runnung unbound 1.5.8-1ubuntu1.1) we were seeing query
times around 20ms: After the upgrade (1.6.7-1ubuntu2.1) those rose to
40ms.

See these graphs:
https://www.arschkrebs.de/bugs/dnssvc30d.png
https://www.arschkrebs.de/bugs/dnssvc1w.png

I then tinkered with different package versions -- tried upgrading to
1.7.3 (no change) and finally downgraded back to to 1.5.8-1ubuntu1.1 -
and the query times dropped to pre-update levels.

Is that to be expected? Is it a regression? I'm a bit late to notice,
but I thought I'd rather ask.

-- 
Ralf Hildebrandt                   Charite Universitätsmedizin Berlin
ralf.hildebrandt at charite.de        Campus Benjamin Franklin
https://www.charite.de             Hindenburgdamm 30, 12203 Berlin
Geschäftsbereich IT, Abt. Netzwerk fon: +49-30-450.570.155