RE: [PATCH][2.4] generic cluster APIC support for systems with m ore than 8 CPUs

["Martin J. Bligh" <mbligh@aracnet.com>]

>> > Yes, our feeling it is possible to handle all non-NUMAQ
>> systems pretty
>> > generically in terms of APIC setup and interrupt routing. We can use
>> > either logical clustered or physical destination modes. But
>> for NUMAQ
>> > systems, interrupt routing has to know about the local
>> nodes and have
>> > necessary logic to do the routing withing local node.
>>
>> NUMA-Q doesn't have to know about the local nodes. I set it up to use
>> physical delivery broadcast, which is a node-local broadcast ... gave
>> me NUMA affinity for free. I could also use logical clustered
>> (p3 style)
>> addressing, and work out all the node locality, but I don't
>> see the point.
>
> I actually meant interrupt distribution (rather than interrupt routing).
> AFAIK, interrupt distribution right now assumes flat logical setup and
> tries to distribute the interrupt. And is disabled in case of clustered
> APIC mode.  I was just thinking loud, about the changes interrupt
> distribution code should have for systems using clustered APIC/physical
> mode (NUMAQ and non-NUMAQ).

Actually, if you're talking about irq_balance, that needs fixing for all
NUMA systems to get affininity, not just NUMA-Q. It then needs an
abstraction layer to do "program the IO-APIC with a cpu_bitmask" that's
different for each apic addressing mode used.

M.