Messages in this thread | | | Date | Thu, 13 Nov 2008 15:14:35 -0800 (PST) | Subject | Re: [PATCH] sparse_irq aka dyn_irq v13 | From | David Miller <> |
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From: Mike Travis <travis@sgi.com> Date: Thu, 13 Nov 2008 15:11:29 -0800
> 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.
We use a value of 256 and I've been booting linux on 128 cpu sparc64 systems with lots of PCI-E host controllers (and others have booted it on even larger ones). All of which have several NUMA domains.
It's not an issue.
> 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.
Just because the same piece of information is repeated over and over again doesn't mean it really matters.
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