Re: [PATCH v5 05/10] cpufreq/schedutil: get max utilization

Juri Lelli
2018-06-04T10:12:53Z

On 04/06/18 09:14, Vincent Guittot wrote:
> On 4 June 2018 at 09:04, Juri Lelli <juri.lelli@redhat.com> wrote:
> > Hi Vincent,
> >
> > On 04/06/18 08:41, Vincent Guittot wrote:
> >> On 1 June 2018 at 19:45, Joel Fernandes <joelaf@google.com> wrote:
> >> > On Fri, Jun 01, 2018 at 03:53:07PM +0200, Vincent Guittot wrote:
> >
> > [...]
> >
> >> > IMO I feel its overkill to account dl_avg when we already have DL's running
> >> > bandwidth we can use. I understand it may be too instanenous, but perhaps we
> >>
> >> We keep using dl bandwidth which is quite correct for dl needs but
> >> doesn't reflect how it has disturbed other classes
> >>
> >> > can fix CFS's problems within CFS itself and not have to do this kind of
> >> > extra external accounting ?
> >
> > I would also keep accounting for waiting time due to higher prio classes
> > all inside CFS. My impression, when discussing it with you on IRC, was
> > that we should be able to do that by not decaying cfs.util_avg when CFS
> > is preempted (creating a new signal for it). Is not this enough?
>
> We don't just want to not decay a signal but increase the signal to
> reflect the amount of preemption

OK.

> Then, we can't do that in a current signal. So you would like to add
> another metrics in cfs_rq ?

Since it's CFS related, I'd say it should fit in CFS.

> The place doesn't really matter to be honest in cfs_rq or in dl_rq but
> you will not prevent to add call in dl class to start/stop the
> accounting of the preemption
>
> >
> > I feel we should try to keep cross-class accounting/interaction at a
> > minimum.
>
> accounting for cross class preemption can't be done without
> cross-class accounting

Mmm, can't we distinguish in, say, pick_next_task_fair() if prev was of
higher prio class and act accordingly?

Thanks,

- Juri