Re: [RFC PATCH] sched: wakeup buddy

From: Mike Galbraith
Date: Thu Feb 28 2013 - 02:24:04 EST

On Thu, 2013-02-28 at 14:38 +0800, Michael Wang wrote:

> + /*
> + * current is the only task on rq and it is
> + * going to sleep, current cpu will be a nice
> + * candidate for p to run on.
> + */

The sync hint only means it might be going to sleep soon, and even then,
there can still be enough execution overlap to be a win to schedule
cross core. Sched pipe numbers will always be much prettier if you do
wakeup cpu affine, as it's ~100% scheduler and ~100% sync. You may lose
a lot on other stuff if you interpret the hint as gospel truth.

IMHO, sched pipe is a "how fat have I become" benchmark, not "how well
do I perform". The scheduler performs well when it makes more work
happen. Playing ping-pong with yourself is _exercise_, not a job :)


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