Re: [RFC PATCH 01/14] sched: track the runnable average on aper-task entitiy basis

[Peter Zijlstra]

On Wed, 2012-02-01 at 17:38 -0800, Paul Turner wrote:
> +       /*
> +        * Use 1024us as the unit of measurement since it's a reasonable
> +        * approximation of 1ms and fast to compute.
> +        */
> +       delta >>= 10;

ns -> us ?, text talks about ms, slightly confusing

> +       if (!delta)
> +               return 0;
> +       sa->last_runnable_update = now;
> +
> +       delta_w = sa->runnable_avg_period % 1024;

so delta_w is the chunk of this p we already accounted.

> +       if (delta + delta_w >= 1024) {

if delta pushes us over 1024*1024 ns (~1ms) we roll a window.

> +               /* period roll-over */
> +               decayed = 1;
> +
> +               delta_w = 1024 - delta_w;

The distance we need to reach the next window.

> +               BUG_ON(delta_w > delta); 

somehow reading this code took forever, this suggests clarification,
either through better variable names or more comments. Could also mean
I'm a moron and should get more sleep or so :-)
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