[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] NR_PIRQS vs. NR_IRQS
On 13/11/08 18:41, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote: > PIRQs are actually a different namespace. They aren't necessarily 1:1 > mapped. Hence NR_PIRQS and NR_IRQS not really same thing. However I'll agree that in some cases it's assumed that the namespaces are the same size (PHYSDEVOP_alloc_irq_vector pretty much does that). And they *are* being used rather interchangeably already... So yes, actually perhaps we should kill off NR_PIRQS. It seems not worth cleaning up usage of NR_IRQS vs NR_PIRQS to make the distinction clean and correct. > 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? -- Keir > -- Keir > > On 13/11/08 16:59, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote: > >> I'm having some difficulty understanding why these two need to be >> distinguished: Depending on the code location, an IRQ passed in from the >> guest may be checked against NR_PIRQS (map_domain_pirq() as called >> from PHYSDEVOP_alloc_irq_vector) or NR_IRQS (PHYSDEVOP_irq_status_query, >> PHYSDEVOP_map_pirq), despite it having the same source. >> >> Also, tying NR_IRQS to NR_VECTORS seems bogus - even with current >> code I can't see why we shouldn't be able to support a higher NR_IRQS >> without immediately doing the more involved code changes needed to >> also grow NR_VECTORS. After all, NR_IRQS is directly tied to the number >> of IO-APIC pins we can support - in order to support a device, its >> cumulative pin number (being the irq) must be below NR_IRQS. But since >> very likely not all pins are connected to devices, NR_VECTORS is much >> less of a limiting factor. >> >> Thanks, Jan >> >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@xxxxxxxxxxxxxxxxxxx >> http://lists.xensource.com/xen-devel > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxxxxxxxx > http://lists.xensource.com/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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