Re: userspace irq balancer

Zwane Mwaikambo
2003-05-22T02:09:38Z

On Wed, 21 May 2003, William Lee Irwin III wrote:

> This is not the case. Interrupt arbitration for sane things generally
> balances interrupt load automatically in-hardware. AIUI the TPR was
> intended to enable the hardware to do such a thing for xAPIC. Linux
> doesn't use the TPR now, which results in decisions made by the
> hardware on xAPIC -based SMP systems that are highly detrimental to
> performance.

Well using the APIC arbitration round robin thing isn't all that smart
either unless you use the TPR, so TPR would be a win everywhere.

> IMHO Linux on Pentium IV should use the TPR in conjunction with _very_
> simplistic interrupt load accounting by default and all more
> sophisticated logic should be punted straight to userspace as an
> administrative API.
>
> i.e. frob the fscking TPR as recommended by the APIC docs every once in
> a while by default, punt anything (and everything) fancier up to
> userspace, and get the code that doesn't even understand what the fsck
> DESTMOD means the Hell out of the kernel and the Hell away from my
> IO-APIC RTE's.

Word... This is all rather tired, if we have a working irq affinity user
accessible interface this can all go away, so how about we just work
towards that means, and then remove kirqd when everyone is happy
(personally i like Arjan's/RH9 userland irqbalance).

Zwane
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