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SubjectRe: [patch] auto-limiting IRQ load take #2, irq-rewrite-2.4.11-F4


Your approach is still wrong. Please do not accept this patch.

cheers,
jamal

On Wed, 3 Oct 2001, Ingo Molnar wrote:

>
> the attached patch contains a cleaned up version of IRQ auto-mitigation.
>
> - i've removed the max_rate limit and have streamlined the impact of the
> load-estimator on do_IRQ() to this piece of code:
>
> desc->total_contexts++;
> if (unlikely(in_interrupt()))
> goto mitigate_irqload;
>
> i dont think we can get much cheaper than this. (We could perhaps avoid
> the total_contexts counter by saving a 'snapshot' of the existing
> kstat.irqs array of counters in every timer tick and comparing the
> snapshot to the current kstat.irqs values. That looked pretty unclean
> though.)
>
> - the per-cpu irq counting in -D9 was incorrect as it collapsed all irq
> handlers into a single counter.
>
> - i've removed the net-polling hacks - they are unrelated to this problem.
>
> the patch is against 2.4.11-pre2. (the eepro100.c fixes from the -ac tree
> are already included in -pre2, i only included them in this patch to make
> patching & testing against 2.4.10 easier.).
>
> (i'd like to stress the point again that the goal of this approach is
> *not* to be nice. This is an airbag mechanizm, it can and will hurt
> performance. But my box does not lock up anymore.)
>
> Ingo
>

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