[dns-operations] DNS server benchmarking sanity check

Anand Buddhdev anandb at ripe.net
Sun Aug 14 20:17:03 UTC 2016

On 14/08/16 12:47, Florian Weimer wrote:

>> Thanks for this. Both Knot and NSD have code to use SO_REUSEPORT. In
>> NSD, it can be turned on or off in the configuration, and so I'm testing
>> both modes. NSD with SO_REUSEPORT performs *much* better.
> Why is this so?  Does NSD use I/O multiplexing?

NSD can spawn multiple processes, and each process binds to a socket.
However, the kernel doesn't distribute queries evenly amongst the
processes. This can lead to some processes being overworked while others
are lightly loaded.

SO_REUSEPORT solves this by letting the kernel divide the queries much
more evenly amongst all the processes, so that they can deliver the
maximum number of responses each.


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