[Pdns-users] Constantly increasing memory usage

Stefan Schmidt zaphodb at zaphods.net
Thu Oct 20 15:02:01 UTC 2011

On Tue, Oct 18, 2011 at 3:02 PM, admin at cu.cc <admin at cu.cc> wrote:
> I checked "pdns_control version" command and it returns that the version is
> 2.9.21

Yeah you should upgrade.

> When I ran the command "pdns_control list" it gives me:
> corrupt-packets=0,deferred-cache-inserts=20,deferred-cache-lookup=11,latency=0,packetcache-hit=3254,packetcache-miss=7039,packetcache-size=903,qsize-q=1,query-cache-hit=17260,query-cache-miss=14247,recursing-answers=0,recursing-questions=0,servfail-packets=0,tcp-answers=0,tcp-queries=0,timedout-packets=838,udp-answers=9417,udp-queries=10294,udp4-answers=9417,udp4-queries=10294,udp6-answers=0,udp6-queries=0,

That doesn't sound like an awful low of packets to be honest. How much
time was in between server start and this command?

> Stefan, you are right about this: I left max-cache-entries and cache-ttl,
> negquery-cache-ttl, query-cache-ttl and recursive-cache-ttl unconfigured
> (BTW I do not see max-cache-entries is that its exact name or shall I add a
> new line with it in pdns.conf?). Could you please give me an idea of what
> values should I put there and how would that affect performance? There are
> quite a few combinations and I am not sure if I will be able to tweak them
> accordingly.

I fear i'm not up to date with the authoritative server knobs, others
on this list might be able to give more insight. All i can say for now
is that you should try what happens if you cut all those default
values to half. After upgrading to the latest stable version that is
of course.
If you enable the built-in web server and let powerdns run for a while
this might give you an idea which knob to turn.
See the packetcache-size and query-cache-miss values for example and
cache hit rates in general.

> "The same goes for MySQL as well of course." - Sorry I don't understand
> that, could you please clarify? What do I need to set to MySQL?

That was meant as a general statement that one needs to tune MySQL too
in order for it not to take up all available RAM depending on it's
working set and query load.


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