On Sat, May 29, 2004 at 06:41:46PM +1000, michael@optusnet.com.au wrote:
> Arjan van de Ven <arjanv@redhat.com> writes:
> > On Fri, May 28, 2004 at 11:33:32AM -0700, Martin J. Bligh wrote:
> [...]
> > > Also, we may well have more than 1 CPU's worth of traffic to
> > > process in a large network server.
> > 
> > One NIC? I've yet to see that ;)
> 
> Oh, and another corner case. 
> 
> Say you have a cpu-bound process on an SMP box.
> Say you're also using a large chunk of a CPU processing
> interrupts from a single IRQ.
> 
> What stops the cpu-bound process being scheduled onto
> the same CPU as the interrupt handlers?
> 
> Now you've got one idle CPU, and one seriously overloaded
> CPU.

yes and the only real answer here is to make the scheduler move the process.
"balancing" the irq (say every other irq) will actually use BOTH cpus 100%
(yes balancing is that expensive due to cache misses :)