Re: [PATCH v3 10/13] sched/fair: Compute task/cpu utilization at wake-up more correctly

[Morten Rasmussen]

On Thu, Aug 18, 2016 at 09:40:55AM +0100, Morten Rasmussen wrote:
> On Mon, Aug 15, 2016 at 04:42:37PM +0100, Morten Rasmussen wrote:
> > On Mon, Aug 15, 2016 at 04:23:42PM +0200, Peter Zijlstra wrote:
> > > But unlike that function, it doesn't actually use __update_load_avg().
> > > Why not?
> > 
> > Fair question :)
> > 
> > We currently exploit the fact that the task utilization is _not_ updated
> > in wake-up balancing to make sure we don't under-estimate the capacity
> > requirements for tasks that have slept for a while. If we update it, we
> > loose the non-decayed 'peak' utilization, but I guess we could just
> > store it somewhere when we do the wake-up decay.
> > 
> > I thought there was a better reason when I wrote the patch, but I don't
> > recall right now. I will look into it again and see if we can use
> > __update_load_avg() to do a proper update instead of doing things twice.
> 
> AFAICT, we should be able to synchronize the task utilization to the
> previous rq utilization using __update_load_avg() as you suggest. The
> patch below is should work as a replacement without any changes to
> subsequent patches. It doesn't solve the under-estimation issue, but I
> have another patch for that.

And here is a possible solution to the under-estimation issue. The patch
would have to go at the end of this set.

---8<---