Re: userspace irq balancer

[Andrew Morton]

Arjan van de Ven <[e-mail]> 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.