Memory utilisation problem on busy bind resolver

Doug Barton dougb at
Tue Aug 9 18:37:03 UTC 2011

On 08/09/2011 07:31, Dennis Perisa wrote:
> Hi folks,
> We are running a number of BIND 9.7.3-p3

9.7.4 is out.

> caching nameservers.  In the
> last couple of months, we've observed the memory utilisation of named
> increasing at a steady rate of 1-2% per day on our busiest resolver
> with no indication of subsiding - on occasion, there have been large
> step increases of 1 GB or so.
> All our other resolvers are configured identically but are behaving
> themselves with memory utilisation remaining at fairly constant
> levels.

Are they getting the same amount of traffic?

> I've looked at all the named logs until my eyeballs have almost fallen
> out of my head but am unable to determine the cause of this.  So I'm
> taking a step back and hoping to get some advice - what else can I do
> to find the cause of this?  Or is it something I simply need to live
> with?
> We're looking at measures such as periodic cache flushes, and tuning
> max-cache-size, max-cache-ttl and max-cache-nttl params to limit
> memory usage, but this may only be treating the symptom and costs us
> extra cpu cycles.

Why isn't the answer, "Put more RAM in the box?" IME if you have a busy
resolver which is using a lot of RAM it's for a good reason. The amount
of time you've already spent on this is worth more than the cost of the
hardware upgrade.



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