Messages in this thread | | | Date | Thu, 13 Nov 2008 15:11:29 -0800 | From | Mike Travis <> | Subject | Re: [PATCH] sparse_irq aka dyn_irq v13 |
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David Miller wrote: > From: Paul Mackerras <paulus@samba.org> > Date: Fri, 14 Nov 2008 09:19:13 +1100 > >> Andrew Morton writes: >> >>> Other architectures want (or have) sparse interrupts. Are those guys >>> paying attention here? >> On powerpc we have a mapping from virtual irq numbers (in the range 0 >> to NR_IRQS-1) to physical irq numbers (which can be anything) and back >> again. I think our approach is simpler than what's being proposed >> here, though we don't try to keep the irqdescs node-local as this >> patch seems to (fortunately our big systems aren't so NUMA-ish as to >> make that necessary). > > This is exactly what sparc64 does as well, same as powerpc, and > as Paul said it's so much incredibly simpler than the dyn_irq stuff.
One problem is that pre-defining a static NR_IRQ count is almost always wrong when the NR_CPUS count is large, and should be adjusted as resources require.
Large UV systems will take a performance hit from off-node accesses when the CPU count (or more likely the NODE count) reaches some threshold. So keeping as much interrupt context close to the interrupting source is a good thing.
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