Re: sched: tweak select_idle_sibling to look for idle threads

From: Chris Mason
Date: Mon May 02 2016 - 11:49:04 EST

On Mon, May 02, 2016 at 04:58:17PM +0200, Peter Zijlstra wrote:
> 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 :/

Adding in the task_hot() check to decide if scanning idle was a good
idea ended up being really important. I'm happy to try a few variations
here as well, do you have a more recent patch?