9.2.5 db causes high cpu? was: Re: BIND 9.2.5rc1 is now available.

Brad Knowles brad at stop.mail-abuse.org
Sun Feb 20 01:44:29 UTC 2005

At 8:58 AM +0900 2005-02-20, JINMEI Tatuya / 
=?ISO-2022-JP?B?GyRCP0BMQEMjOkgbKEI=?= wrote:

>  I'd first like to recommend disabling threads.  From my experiences,
>  enable-threads buys almost nothing for most OSes, unfortunately.  If
>  you can allow the configuration with 2 named processes, it should
>  provide better performance than a single BIND9 process with 2 threads.

	But BIND9 already has serious memory problems, and running 
multiple copies would make that situation far, far worse.  Moreover, 
99% of the content between the two copies would be duplicated, and 
you run into the problem where you need to split your incoming 
traffic across the separate processes, and that's not always easy to 

	We ran into all these same problems when I set up the AOL Caching 
Nameserver farm at AOL in '96-'97, using four DEC Alpha 4100 machines 
with four CPUs each, 4GB of RAM, and four copies of BIND 8 running on 
each machine, in active-active failover.  Sure, the whole cluster 
could do something on the order of 32,000 queries per second, with 
each copy of BIND topping out at 2000 qps, but then you come up with 
the problem of how to distribute that load across the cluster so that 
you really do see the throughput potential?

	For nameservers which have any amount of authoritative function, 
the BIND9 threading solution means that the nameserver is not blind 
on startup, which I consider to be a huge win over BIND8 -- a 
critical win, even.

	I don't think this is a feasible long-term solution.

	If we can't make BIND9 with threading work as well as or better 
than multiple copies of BIND8, then we might as well go home.  IMO, 
BIND8 can't be retired until this happens.

>  One possible reason for this is that max-cache-size did not work for
>  ADB, another memory-conscious database for caching servers, in 9.2.x.
>  I believe 9.3.x has a fix to this.

	Have we finally implemented an interface to Berkeley DB?

Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.

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