Re: cpu load balancing problem on smp

[Arjan van de Ven <arjan@linux.intel.com>]

On Tue, 2007-02-06 at 18:32 +0100, Marc Donner wrote:
> Hi @all
> 
> we have detected some problems on our live systems and so i have build a test 
> setup in our lab as follow:
> 
> 3 Core 2 duo servers, each with 2 CPUs,  with GE interfaces. 2 of them are 
> only for generating network traffic. the 3rd server is the one i want to 
> test. it is connected over two GE links to the other servers. the testserver 
> is configured as an ip router. running kernel 2.6.20. 
> 
> now if i  let traffic flow over the box, about 600Mbit/s and about 120k 
> packets/s all seems to be ok. the load is balanced over all cpus. if now 
> insert some iptables rules, about 500, the softirq load increases, but all 
> seems to be ok. now i insert some rules more, and suddenly 1 CPU is 100% 
> loaded and the other ones are 99% idle. the load toggles now between the cpus 
> in intervals.

I wonder if you are using irqbalance.. if not you probably want to...
(this should at least split it over 2 cpus)

see http://www.irqbalance.org to get irqbalance