[nsd-users] CPU and memory usage

Wouter Wijngaards wouter at nlnetlabs.nl
Fri Jul 11 08:31:55 CEST 2014


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Hi Ed,

On 07/10/2014 03:53 PM, Ed Y wrote:
> Hi there,
> 
> I have an NSD 4.0.3 slave running on FreeBSD.  There are about 120 
> signed (NSEC3) domain names in the db, which is 500MB.  Whenever
> the largest zone file (89MB when signed) is transferred from the
> master, the CPU load on the box sits at around 90% for several
> hours.  During this time nsd-control zonestatus shows a different
> commit serial vs served serial, indicating that it's processing.
> If I remove all of the other zone files from nsd.conf and just
> leave that 89MB zone the zone is transferred and served in less
> than 1min.
> 
> FreeBSD (64-bit) is running as a VM with 10GB of memory, it has 2 
> processors with four cores each.
> 
> I found one past nsd-users email that indicated there was a problem
> in 4.0.3 with large zone files and that the next version allows a
> separate db to be specified for large zones??

Yes that would likely help you here.  The main effect is to reduce the
memory usage, and disk usage, I think that is what NSD is spending its
time on.  It is trying to update the nsd.db and this is (apparantly)
taking a lot of time.  Perhaps the VM has a lot of memory but the host
system does not and it starts swapping to disk?

The version under development (available in the development
repository), has a feature where you can set database: "" and it then
does not make that database.  And likely, that means when you do a
zone transfer your machine does not start swapping to disk (or
whatever other pathological problems manifest at that time).  However,
without the nsd.db is still needs to use main memory, if you are short
on that, then your OS could still go swap to disk and things become
very slow.

Best regards,
   Wouter
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