Re: sched: tweak select_idle_sibling to look for idle threads

From: Peter Zijlstra
Date: Mon May 02 2016 - 10:58:33 EST

On Mon, May 02, 2016 at 04:50:04PM +0200, Mike Galbraith wrote:
> Oh btw, did you know single socket boxen have no sd_busy? That doesn't
> look right.

I suspected; didn't bother looking at yet. The 'problem' is that the LLC
domain is the top-most, so it doesn't have a parent domain. I'm sure we
can come up with something if we can get this all working right.

And yes, I can get gains on various workloads with various options, I
can even break all workloads, but I've so far completely failed on
getting a win for everyone :/

In particular low count sysbench-psql (oltp test) vs tbench
client==nr_cores is having me flummoxed for a bit.