BIND 9.x caching Performance under heavy loads

Bernhard Schmidt berni at
Wed Mar 30 23:47:35 UTC 2005

On 2005-03-25, Kelsey Cummings <kgc at> wrote:

>> Also, if you have a uniprocessor system, you might want to test the
>> patch I recently posted to enable better BIND9 statistics.
> The systems are all P4 CPUs with HT enabled. 
> While the comments are appreciated they don't address the specific problems
> which is bind going into a 100% CPU spin for no apparent reason after a long
> period of stable operation.  During this time it's still answering reqeusts
> but with delays in the 10-30 second range.

JFTR, I have a similar problem, with BIND 9.3.1 threaded running on a
Dual Xeon 2.8Ghz with 4GB RAM on SLES9 (Linux 2.6.5-something). The box
is not very much loaded (about 100-400qps depending on daytime), but has
to carry a big RBL which pumps up memory usage to 500M after startup and
has query logging enabled. It does both authorative and resolver (old

After some days of decent operation (with about 10% CPU load in daytime, less
during the night) CPU usage ramps from 5% to 80% within half an hour. No
suspicious queries, same query rate, memory definitely not used (the
process has 900M or so), about the same amount of recursive clients and
so on. The only thing that fixes it is either "rndc flush" or restarting
the named-process.

This doesn't have a notable impact on query latency, but it is
disturbing enough to have it restarted immediately. The old setup (BIND
9.2.2, same machine, SuSE 9.0 with some 2.4 kernel) did not show this

Any ideas? I could disable threading, but the dual CPU were bought, so I
do want to use them.


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