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Date: Mon, 9 Sep 2002 20:44:25 +0200 (CEST)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Zwane Mwaikambo <zwane@mwaikambo.name>, Robert Love <rml@tech9.net>,
       Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH][RFC] per isr in_progress markers
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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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