Messages in this thread | | | Date | Fri, 29 Feb 2008 22:32:07 +0100 | From | Ingo Molnar <> | Subject | Re: [RFC/PATCH] cpuset: cpuset irq affinities |
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* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> > Could you educate me a little, Peter, on what these irqs are and on > > the sorts of ways people might want to place them across CPUs? > > I'm not sure I know what you're asking. IRQ are hardware notifiers and > do all kinds of things depending on the hardware. Network cards > typically use them to notify the CPU of incoming packets. Video cards > can do vsync notifiers, empty dma buffers, whatnot.
irq affinity masks can basically be thought of as: "these are the CPUs where external hardware events will trigger certain kernel functions and cause overhead on those CPUs". An IRQ can have followup effects: softirq execution, workqueue execution, etc.
so managing the IRQ masks is very meaningful and just as meaningful as managing the affinity masks of tasks. You can think of "IRQ# 123" as "special kernel task # 123".
Ingo
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