Re: [PATCH] sched/fair: util_est: fast ramp-up EWMA on utilization increases
From: Patrick Bellasi
Date: Mon Jul 01 2019 - 04:53:57 EST
On 30-Jun 10:43, Vincent Guittot wrote:
> On Fri, 28 Jun 2019 at 16:10, Patrick Bellasi <patrick.bellasi@xxxxxxx> wrote:
> > On 28-Jun 15:51, Vincent Guittot wrote:
> > > On Fri, 28 Jun 2019 at 14:38, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > > > On Fri, Jun 28, 2019 at 11:08:14AM +0100, Patrick Bellasi wrote:
> > > > > On 26-Jun 13:40, Vincent Guittot wrote:
> > > AFAICT, it's not related to the time-scaling
> > >
> > > In fact the big 1st activation happens because task runs at low OPP
> > > and hasn't enough time to finish its running phase before the time to
> > > begin the next one happens. This means that the task will run several
> > > computations phase in one go which is no more a 75% task.
> > But in that case, running multiple activations back to back, should we
> > not expect the util_avg to exceed the 75% mark?
> But task starts with a very low value and Pelt needs time to ramp up.
> > > Once cpu reaches a high enough OPP that enable to have sleep phase
> > > between each running phases, the task load tracking comes back to the
> > > normal slope increase (the one that would have happen if task would
> > > have jump from 5% to 75% but already running at max OPP)
> > Indeed, I can see from the plots a change in slope. But there is also
> > that big drop after the first big activation: 375 units in 1.1ms.
> > Is that expected? I guess yes, since we fix the clock_pelt with the
> > lost_idle_time.
... but, I guess Peter was mainly asking about the point above: is
that "big" drop after the first activation related to time-scaling or