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SubjectRe: affinity and tasklets...

On Mon, 17 Dec 2001, Ashok Raj wrote:

> In a MP case, we would like 2 separate processors taking the
> completion processing. But running tasklets dont seem to suit this
> since it basically queues on the same CPU that is currently running,
> and this means both get queued to the same tasklet_vec[cpu]. But i
> want each to run on a separate CPU. is using softirq the right method?
> or could i have cpu affinity for tasklets? (i know there is afficinity
> for interrupts, but iam not aware of this for tasklets.)

you'll get a natural affinity of tasklets: they will run on the processor
where the tasklet got activated. Tasklets are just a special form of
softirqs, they have no context in the classic task sense, the only
difference they have to softirqs is that the tasklet code guarantees
single-threadedness of the function executed.
if you are going to rely on tasklets for good SMP scalability then i'd
suggest using a separate tasklet for every device IRQ. Then bind hardirqs
to a particular CPU - thus both the hardirq, the softirq/tasklet will run
on the same processor.

Ingo

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