Re: [PATCH] sched/fair: Introduce fits_capacity()
From: Viresh Kumar
Date: Tue Jun 18 2019 - 03:52:33 EST
On 18-06-19, 09:26, Rafael J. Wysocki wrote:
> On Tue, Jun 18, 2019 at 5:12 AM Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
> > +Rafael
> > On 17-06-19, 17:02, Peter Zijlstra wrote:
> > > On Thu, Jun 06, 2019 at 08:22:04AM +0530, Viresh Kumar wrote:
> > > > Hmm, even if the values are same currently I am not sure if we want
> > > > the same for ever. I will write a patch for it though, if Peter/Rafael
> > > > feel the same as you.
> > >
> > > Is it really the same variable or just two numbers that happen to be the
> > > same?
> > In both cases we are trying to keep the load under 80% of what can be supported.
> > But I am not sure of the answer to your question.
> > Maybe Rafael knows :)
> Which variable?
Schedutil multiplies the target frequency by 1.25 (20% more capacity eventually)
to get enough room for more load and similar thing is done in fair.c at several
places to see if the new task can fit in a runqueue without overloading it.
Quentin suggested to use common code for this calculation and that is what is
getting discussed here.