> On Thursday 12 December 2002 07:26 pm, Zwane Mwaikambo wrote:
> > On Thu, 12 Dec 2002, Nakajima, Jun wrote:
> > > BTW, we are working on a xAPIC patch that supports more than 8 CPUs in a
> > > generic fashion (don't use hardcode OEM checking). We already tested it
> > > on two OEM systems with 16 CPUs.
> > > - It uses clustered mode. We don't want to use physical mode because it
> > > does not support lowest priority delivery mode.
> >
> > Wouldn't that only be for all including self? Or is the documentation
> > incorrect?
> >
> > Thanks,
> > Zwane
>
> I'm not sure I understand your question. Lowest Priority delivery mode only
> works with logical interrupts. (I've tried it with physical intrs. It fails
> miserably.) The "all including self" and "all excluding self" destination
> shorthands don't do lowest priority arbitration. They always deliver the
> interrupt to the CPUs mentioned in the shortand.
>
> Lowest priority delivery mode isn't _too_ useful in Linux yet. It would be
> nice to preferentially target idle CPUs with interrupts in real time. That
> means changing each CPU's Task Priority Register (TPR) to represent how busy
> it is. I've got some patches to do that, but haven't posted them as anything
> more than a RFC.
>
Hmm, I though the APIC routing patch found in the LSE project
(http://sourceforge.net/projects/lse/) did this already. Atleast I've
tested this patch on a couple of Dual E7500 Xeon boxes (kernel 2.4.20) and
it distributes interrupts nicely.
However with the patch enabled, the interrupt latency on for example the
Intel GbE 82544GC devices increased a fraction with this patch (a
microsecond or two).
Regards,
-- Steffen Persvold | Scali AS mailto:sp@scali.com | http://www.scali.com Tel: (+47) 2262 8950 | Olaf Helsets vei 6 Fax: (+47) 2262 8951 | N0621 Oslo, NORWAY- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/