BIND 9.x caching Performance under heavy loads

[Mark Andrews]

> On 2005-03-31, Bernhard Schmidt <berni at birkenwald.de> wrote:
> 
> > But still, the CPU hog is there, and the CPU hog is not explainable with
> > the general difference in speed. After all, it is running fine for some
> > days until CPU usage explodes. I'm running the non-threaded version now
> > since one day, if it keeps running this way until next week the bug is
> > related to threading.
> 
> I got some new results, maybe someone could point me to the options we
> might have. 
> 
> The bug appeared with the multithreaded version as well as with the
> non-threaded version. We removed the biiiig RBL zone from the server and
> the bug still appeared. So far we did only find _one_ option which makes
> our problem disappear:
> 
> 	max-cache-size 300M;
> 
> if we set it to unlimited or to something higher than 300M (for example
> 400M) BIND starts burning the CPU within two days. Remind you that this
> server has 4GB of RAM and is dedicated to this BIND process. No ulimits
> are set.

	If you start to page you will burn cpu.  Sounds like you need
	to increase the amount of memory that a process can get.  Note
	the OS may still have a limit which needs to be adjusted even
	when limits says that it is unlimited.
 
> Our next try will probably be to compile with
> ISC_MEM_USE_INTERNAL_MALLOC. I read there are some (performance) issues
> with this flag and running threaded, would it be wise to use the
> non-threaded version and basically ignore three of four CPUs?
> 
> Thanks
> Bernhard
> 
> 
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org