Had noticed a strange issue today, BIND began using more than 10% of CPU time, which caused really slow responds. I'd been using Google Public DNS A/B for forwarding recursive requests, after noticing the issue I changed it to point to OpenDNS 1st and 2nd server. The issue had gone. Checked it vice-versa again - issue was reproduced again, so I'm still using OpenDNS for forwarding requests.
Do you have any idea why does CPU load depend on used DNS forwarder? Or what can cause this coincidence?
Below's system and BIND version information:
ns.XXX.net:~# named -v
BIND 9.4.2-P2
ns.XXX.net:~# uname -a
OpenBSD ns.XXX.net 4.7 GENERIC.MP#449 i386
