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SubjectRe: userspace irq balancer
William Lee Irwin III <> wrote:
>> In
>> the userspace implementation the reprogramming is done infrequently
>> enough to make even significant cost negligible; in-kernel the cost
>> is entirely uncontrolled and the rate of reprogramming unlimited.

On Mon, May 26, 2003 at 06:59:20PM -0700, Andrew Morton wrote:
> eh?

The number of interrupt sources on a system ends up scaling this up to
numerous IO-APIC RTE reprograms and ioapic_lock acquisitions per-second
(granted, with a 5s timeout between reprogramming storms) where it
competes against IO-APIC interrupt acknowledgements.

Making the lock per- IO-APIC would at least put a bound on the number
of competitors mutually interfering with each other, but a tighter
bound on the amount of work than NR_IRQS would be more useful than that.

-- wli
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