Re: userspace irq balancer

[William Lee Irwin III]

On Mon, 26 May 2003, William Lee Irwin III wrote:
>> 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.

On Mon, May 26, 2003 at 10:15:23PM -0400, Zwane Mwaikambo wrote:
> Ok there are 16 IOAPICs on an 8quad, but really if we start banging on 
> that lock someone is doing way too much hardware access...

It's done to acknowledge every interrupt. Also, there is additional
cost associated with bouncing the lock's cacheline.

-- wli