Re: [RFC PATCH v3 0/3] sched: simplify the select_task_rq_fair()

From: Peter Zijlstra
Date: Wed Feb 20 2013 - 08:32:57 EST

On Wed, 2013-02-20 at 11:49 +0100, Ingo Molnar wrote:

> The changes look clean and reasoable,

I don't necessarily agree, note that O(n^2) storage requirement that
Michael failed to highlight ;-)

> any ideas exactly *why* it speeds up?

That is indeed the most interesting part.. There's two parts to
select_task_rq_fair(), the 'regular' affine wakeup path, and the
fork/exec find_idlest_goo() path. At the very least we need to quantify
which of these two parts contributes most to the speedup.

In the power balancing discussion we already noted that the
find_idlest_goo() is in need of attention.

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