Re: [PATCH 1/1] SGI X86 UV: Provide a System Activity Indicator driver

[Andi Kleen]

Mike Travis <travis@xxxxxxx> writes:
>
> I do use the timer mechanism (once per second) to update the scir state.
> Unfortunately, the state is *always* not idle during the timer callback
> (since we are actively executing), so I needed some way of knowing the
> idle state prior to the timer callback.

The idle thread always has pid 0. So if the timer sees current->pid == 0
it interrupted idle.

But sampling only once a second would be presumably not very accurate.
You could just check the per cpu statistics the kernel keeps
anyways in the timer.

I agree with Ingo that this doesn't belong in a idle notifier.

-Andi
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