[Pdns-users] pdns-recursor cache settings

Tomasz Kawalec kawalec.tomasz at gmail.com
Sat Feb 22 14:10:19 UTC 2014

          I've a question about pdns-recursor and its settings. I've a
pdns-recursor running with 4 threads. I'm trying to set up the best
performance setting and I'm confused about the max-(packet)cache-entries
settings. In the performance guide (
http://doc.powerdns.com/html/recursor-performance.html) it is said that:

"Limit the size of the caches to a sensible value. Cache hit rate does not
improve meaningfully beyond 4 million max-cache-entries per thread,
reducing the memory footprint reduces CPU cache misses. See below for more
information about the various caches. "

Does it mean if I want 4 million `max-cache-entries` per thread with 4
threads running I've to set `max-cache-entries` to 4000000 (4M) or 16000000

How can I interpret these example settings with `threads` set to 4?
a) max-cache-entries = 4000000
b) max-packetcache-entries = 1000000

a) Each thread will have the limit of 4000000 entries or 1000000 entries?
b) Each thread will have the limit of 1000000 entries or 250000 entries?

I've studied the documentation and I can't find an answer to my question.
Please answer if You are absolutely sure how those settings behave.

If anyone have experience in setting the threads/max-(packet)cache entries
for busy DNS environment and would like to share his settings with stating
average qps from hosts will be appreciated. Best Regards.
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