Re: [RFC PATCH] sched: wakeup buddy

[Mike Galbraith]

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 :)

-Mike

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/