Re: RT patch acceptance

Bill Huey
2005-05-27T20:32:17Z

On Fri, May 27, 2005 at 02:10:56PM +0200, Ingo Molnar wrote:
> * Bill Huey <bhuey@lnxw.com> wrote:
>
> > There's really no good reason why this kernel can't get the same
> > latency as a nanokernel. The scheduler paths are riddled with SMP
> > rebalancing stuff and the like which contributes to overall system
> > latency. Remove those things and replace it with things like direct
> > CPU pining and you'll start seeing those numbers collapse. [...]
>
> could you be a bit more specific? None of that stuff should show up on
> UP kernels. Even on SMP, rebalancing is either asynchronous, or O(1).

I found out a couple of problems with IRQ rebalancing in that the
latency spread was effected by a ping-ponging of the actual interrupt
itself. I reported this to you in November and I fixed this problem
by gluing the interrupt to the same cpu as the irq-thread.

Not sure if it was the rebalancing or the cache issues, but they seem
related.

bill