Re: [PATCH] 2.6.1-mm2: Get irq_vector size right for generic subarchUP installer kernels

[Zwane Mwaikambo]

On Wed, 14 Jan 2004, James Cleverdon wrote:

> On Tuesday 13 January 2004 5:00 pm, Zwane Mwaikambo wrote:
> > On Tue, 13 Jan 2004, James Cleverdon wrote:
> > > Problem:  Earlier I didn't consider the case of the generic sub-arch and
> > > uni-proc installer kernels used by a number of distros.  It currently is
> > > scaled by NR_CPUS.  The correct values should be big for summit and
> > > generic, and can stay the same for all others.
> >
> > This all looks strange, especially in assign_irq_vector() does this
> > mean that you'll try and allocate up to 1024 vectors?
>
> The irq_vector array name is a bit misleading.  It contains the vectors for
> each potential I/O APIC RTE.  The array needs to be at least the sum of all
> the RTEs in the system.  Summit PCI bridge chips have large I/O APICs (50
> RTEs), and a large system has up to 16 of them.  16*50 = 800.  Allocating 1k
> entries provides a pad for the future, and u8 doesn't cost much.

Ok i understand the need to accomodate all the RTEs, but what i was
considering was what happens when assign_irq_vector runs out of vectors to
allocate and ends up "wrapping". I just sent an email to Jun Nakajima with
a bit more detail.

Thanks,
	Zwane

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