DHCP Queue

David W. Hankins David_Hankins at isc.org
Thu Feb 12 22:32:59 UTC 2009

On Thu, Feb 12, 2009 at 12:24:44PM -0800, Brad Dameron wrote:
> The fastest I have seen with ISC is about 1200 per second. And that was
> with the fastest machine we could get using a ramdisk for leases and
> turning logging completely off. I'm baffeled by that. 

That sounds about right, for a single thread.  Unfortunately that's
5.3:1 on presumably similar hardware.  You can run two daemons and
split the client load among them with some configuration tricks, so
maybe 2.6:1 to be fair, still a wide margin.  You might also get a bit
more performance out of using standard sockets rather than raw
sockets (and putting all the clients behind relays), but I'm not
actually sure how much.  I doubt it would get closer than 2 times.  It
would be interesting to see.

ISC DHCP's main performance challenge comes from its flexibility.  The
configuration language is an interpreted programming language!  All
that flexibility comes at a price.

Still, there are ways we can reorganize the execution path so that you
don't have to spend CPU to support features you aren't using.  We'll
get there someday.

In the meantime hopefully 1,200 per second (52 million clients at a
24 hour lease time, 2 million at 1 hour) is 'good enough' for modern
hardware until we can improve the tools.

David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins
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