Re: [PATCH v4 6/7] sched: add function nr_running_cpu to expose number of tasks running on cpu

From: Peter Zijlstra
Date: Tue Jul 15 2014 - 08:07:49 EST

On Tue, Jul 15, 2014 at 11:50:45AM +0200, Peter Zijlstra wrote:
> So you already have an idle notifier (which is x86 only, we should fix
> that I suppose), and you then double check there really isn't anything
> else running.

Note that we've already done a large part of the expense of going idle
by the time we call that idle notifier -- in specific, we've
reprogrammed the clock to stop the tick.

Its really wasteful to then generate work again, which means we have to
again reprogram the clock etc.

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