Re: [RFC] sched: CPU topology try

From: Peter Zijlstra
Date: Tue Jan 07 2014 - 09:11:37 EST

On Tue, Jan 07, 2014 at 02:22:20PM +0100, Peter Zijlstra wrote:

I just realized there's two different p's in there.

> Ah, another way of looking at it is that the avg without blocked
> component is a 'now' picture. It is the load we are concerned with right
> now.
> The more blocked we add the further out we look; with the obvious limit
> of the entire averaging period.
> So the avg that is runnable is right now, t_0; the avg that is runnable +
> blocked is t_0 + p, where p is the avg period over which we expect the
> blocked contribution to appear.

So the above p for period, is unrelated to the below p which is a
probability function.

> So something like:
> avg = runnable + p(i) * blocked; where p(i) \e [0,1]
> could maybe be used to replace the cpu_load array and still represent
> the concept of looking at a bigger picture for larger sets. Leaving open
> the details of the map p.

We probably want to assume task wakeup is constant over time, so p (our
probability function) should probably be an exponential distribution.
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