[Pdns-users] Latency and cache size are correlated

bert hubert bert.hubert at netherlabs.nl
Wed Apr 30 11:56:27 UTC 2008

On Tue, Apr 29, 2008 at 05:17:57PM -0700, Eugene Pefti wrote:
> Can somebody explain me why the recursor cache size and latency are
> correlated and directly proportional?
> This is my dns graph.
> http://ns2.w3media.net/recursor/
> Whenever the cache grows up to 30K entries the latency reaches as high as
> 120 ms. See the second graph called  "Questions/Answers latency in
> milliseconds"

You have so little questions (10/second) that the statistics are not very
good, and will be dominated by single queries that time out.

> It when it reaches 120-130 ms it really affects recursor performance.

If you see performance issues, please try
http://svn.powerdns.com/snapshots/pdns-recursor-3.1.6-pre.tar.bz2 it
contains an important fix for a timeout problem.

Also, have you managed to look at the questions I sent you earlier? 


http://www.PowerDNS.com      Open source, database driven DNS Software 
http://netherlabs.nl              Open and Closed source services

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