Maintained by: NLnet Labs

[Unbound-users] RRset and Message cache functionality

W.C.A. Wijngaards
Wed Jun 30 13:57:41 CEST 2010

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Hi Sheridan,

The way that is measured it by setting the sizes very large, and before
they fill up, measure.

The things you say about your system are because of your local config.
If you configured different that would happen.  What you describe is
intended and normal, and caused by your configuration of the sizes.  If
you want unbound to have a 130Mb rrset cache, then it will do that. :-)

If you want to know everything about them you would have to read the
source.  Short summary is that the message cache contains message
formats, and the rrset cache contains rr data from the internet.  So if
your queries are different, and have less number of records per message,
but very large ones (say TXT or NAPTR), then the rrset cache would grow
faster.  If you have many small rrsets then the message cache may grow
faster.  For typical internet, roughly 2-to-1.

Best regards,

On 06/24/2010 10:44 PM, sheridan at wrote:
> Hi,
> I'm trying to understand the cache memory usage of unbound a bit better. I
> noticed that unbound-control only responds with the message and rrset
> cache usage so I assume these are responsible for most of the memory
> usage.
> I also notice in the tuning documentation it's recommended the rrset cache
> be allocated roughly twice the memory of the message cache, but on my
> system the message cache catches and surpasses the rrset at around 130MB
> using the default configuration for everything but the sizes.
> I really have no idea how these two caches are being used(what they
> contain, when they're referenced, ect.) so I'm not sure if the behavior is
> normal or not. I'm hoping someone can offer insight or point me towards
> any relevant documentation.
> Thanks for any input.
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