Re: userspace irq balancer

Andrew Morton
2003-05-20T09:01:56Z

Arjan van de Ven <arjanv@redhat.com> wrote:
>
> On Mon, May 19, 2003 at 10:03:50PM -0700, Dave Hansen wrote:
> > Does anyone have a patch to tear it out already? Is the current proc
> > interface acceptable, or do we want a syscall interface like wli
> > suggests?
>
> I have no problems with the proc interface; it's ascii so reasonably
> extendible in the future for, say, when 64 cpus on
> 32 bit linux get supported. It's also not THAT inefficient since my code
> only uses it when some binding changes, not all the time.

Concerns have been expressed that the /proc interface may be a bit racy.
One thing we do need to do is to write a /proc stresstest tool which pokes
numbers into the /proc files at high rates, run that under traffic for a
few hours.

There is no need to pull out the existing balancer until the userspace
solution is proven - it can be turned off with `noirqbalance' until that
work has been performed.

Nobody has tried improving the current balancer. From a quick look it
appears that it could work reasonably for the problematic packet-forwarding
workload if the when-to-start-balancing threshold is reduced from 1000/sec
to (say) 10/sec. Don't know - I've never seen a description of how the
algorithm should be improved.