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Re: [Xen-devel] NR_PIRQS vs. NR_IRQS

To: Jan Beulich <jbeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] NR_PIRQS vs. NR_IRQS
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Fri, 14 Nov 2008 07:54:29 +0000
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On 14/11/08 07:48, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

>>> Yes, I'm sure with a bit of finessing we could have NR_IRQS != NR_VECTORS.
>>> I'm sure there'll be some barking NUMA box down the road that will require
>>> something like that, but thankfully not so far.
>> 
>> I agree with keeping this naming distinction of course, although I think
>> allowing NR_IRQS > NR_VECTORS right now is not very useful. But maybe you
>> have a box in mind that needs it?
> 
> I had sent a mail a few days ago on this, where IBM was testing 96 CPU
> support (4-node system), and it crashing because of a PIRQ ending up in
> DYNIRQ space (kernel perspective), because there being 300+ IO-APIC
> pins. While the crash ought to be fixed with the subsequent patch, it's
> clear that none of the devices with an accumulated pin number greater
> than 255 will actually work on that system.

Oh dear. :-D

 -- Keir



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