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SubjectRe: introduce NMI_AUTO as nmi_watchdog option

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, 2010-01-13 at 10:32 +0100, Ingo Molnar wrote:
> > other architectures have NMI concepts as well, such as Sparc64.
>
> I think both sparc64 and ppc64 fake NMIs by playing games with hw IRQ
> priorities and partial masks. But yes.
>
> One interesting 'feature' for the perf-nmi interaction is creating an idle
> scheduling class for counters, because as long as there is a counter present
> you can use his NMIs to drive the watchdog, but as soon as there are non
> left, you need to install one.

Yeah. I'd suggest to not complicate things with that initially - but to simply
create a standalone event for it and 'waste' a counter on NMI generation.

Later on it can indeed be a good feature to make the NMI watchdog 'seemless'
in the sense of it not causing any wasted hw resources - it can piggyback on
any existing NMI event. (as long as that event is at least ~1 HZ strong or so)

Ingo


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