Re: SMP CPU affinity questions

[Zwane Mwaikambo <zwane@arm.linux.org.uk>]

On Wed, 2 Nov 2005, Jeffrey V. Merkey wrote:

> IOApic's support binding of interrupt delivery in intel based platforms, but I
> am unaware of tools which force this
> setting by default on Linux, but someone else may be able to point you in that
> direction.  Most folks code APIC ICC delivery to
> AV_LOPRI (meaning lowest priority processor gets next interrupt).   This is
> advantageous for cache coherency since the IRQ code
> is probaby still in that processors cache.  You may have to modify the kernel.
> Linux doesn't allow processors to be shutdown and
> reactiviated real time, it just starts them and lets them run, so you don;t
> have to worry about the case of migrating interrupts
> off pinned APICs.  The APIC supports what you are asking for, but I am not
> certain anyone implemented anything other
> than AV_LOPRI settings by default in the IO APIC code.  I would suggest you
> look over the IO APIC Code -- this is a lot
> of work, BTW.

Or you could just put something which writes to 
/proc/irq/$IRQ/smp_affinity in your initscripts.

Cheers,
	Zwane

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