Re: [PATCH][RFC] per isr in_progress markers

Ingo Molnar (mingo@elte.hu)
Mon, 9 Sep 2002 20:44:25 +0200 (CEST)


On Mon, 9 Sep 2002, Linus Torvalds wrote:

> Remember: you'd be "improving latency" by taking several interrupts
> instead of taking just one. And usually, if the system is really under
> so much interrupt load that this would be noticeable, you want to try to
> _mitigate_ interrupts instead of adding new ones.

There's also the following effect that could generate additional
interrupts: the *same* IRQ source that is currently executing might
generate a (spurious but otherwise harmless) interrupt if we first ACK the
card then ACK the APIC and then do processing. Our current way of masking
interrupts in the IO-APIC at least leaves them pending there until the
handler's main work loop is finished and mitigates irqs.

Ingo

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