[Dnsmasq-discuss] Slow DHCP Performance with 7500 Static Reservations

[Jan Seiffert]

2011/6/14 Mike Ruiz <mruiz at zynga.com>:
> Hello All,
> We use dnsmasq as a very effective replacement for the ISC software, thus
> far with great success. However, we have run into occasional performance
> problems at scale.
> These seem to manifest as a general slowdown of the request -> reply
> process, which can sometimes exceed 90 seconds from request to reply.
[snip]
> Are there any obvious inflection points that would cause the server to drop
> in performance by a few orders of magnitude with lots of hosts defined? Are
> there any recommendations for tuning, beyond introducing more dnsmasq
> servers?

Hmmm, this sounds like some O² or worse scaling code...

Can you run some tests?
Compile dnsmasq with -g, and run it under valgrind like this:
valgrind --tool=callgrind --dump-instr=yes --collect-jumps=yes
--simulate-cache=yes --simulate-hwpref=yes --cacheuse=yes dnsmasq
--dnsmasq-options

Now let it hand out a dhcp allocation, and stop it afterwards.
You should get a callgrind.out.$pid and can feed it into kcachegrind.

> -Mike

Greetings
Jan

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