Messages in this thread | | | From | (Eric W. Biederman) | Date | Wed, 24 Sep 2008 12:34:09 -0700 | Subject | Re: Should irq_chip->mask disable percpu interrupts to all cpus, or just to this cpu? |
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Jeremy Fitzhardinge <jeremy@goop.org> writes:
> I found handle_percpu_irq() which addresses my concerns. It doesn't > attempt to mask the interrupt, takes no locks, and doesn't set or test > IRQ_INPROGRESS in desc->status, so it will scale perfectly across > multiple cpus. It makes no changes to the desc structure, so there > isn't even any cacheline bouncing.
kstat_irqs. Is arguably part of the irq structure. And kstat_irqs is a major pain in my book.
And for a rare event you have a cacheline read. I don't think we are quite there yet but we really want to allocate irq_desc on the right NUMA node in a multi socket system, to reduce the cache miss times.
Is it a big deal? Probably not. But I think it would be a bad idea to increasingly use infrastructure that will make it hard to optimize the code.
Especially since the common case in high performance drivers is going to be, individually routable irq sources. Having one queue per cpu and one irq per queue. Which sounds like the same case you have.
Eric
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