Messages in this thread | | | Date | Fri, 15 Mar 2002 08:50:43 +0100 (CET) | From | Ingo Molnar <> | Subject | Re: Severe IRQ problems on Foster (P4 Xeon) system |
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On Thu, 14 Mar 2002, Martin J. Bligh wrote:
> >> Btw is it correct that one could also use the APIC Task Priority Registers > >> to implement "fair" IRQ routing? (If linux adjusted them, which it > >> currently doesn't). > > > > Yes, and Dave Olien has already done this. It's a good idea for P3, > > and seems to me to be essential for P4.
another problem with TPR-based IRQ routing (in addition to the ones i mentioned in the previous mail) is that if you 'deny' certain IRQs via the TPR, then if all CPUs run kernel-intensive jobs, then IRQs will never be served by any of the CPUs (or will be served only after a long latency). Sure, this can be hacked around, but if gets ugly very fast and doesnt get us very far. All in one, i found the TPR to be not flexible enough for what we really want: good IRQ distribution and good IRQ affinity at once.
Ingo
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