On Mon, Apr 18, 2016 at 03:35:06PM +0200, Frederic Weisbecker wrote:
> On Mon, Apr 18, 2016 at 06:17:21PM +0900, Byungchul Park wrote:
> > On Wed, Apr 13, 2016 at 03:56:51PM +0200, Frederic Weisbecker wrote:
> > > @@ -4645,11 +4674,11 @@ void cpu_load_update_nohz(int active)
> > > void cpu_load_update_active(struct rq *this_rq)
> > > {
> > > unsigned long load = weighted_cpuload(cpu_of(this_rq));
> > > - /*
> > > - * See the mess around cpu_load_update_idle() / cpu_load_update_nohz().
> > > - */
> > > - this_rq->last_load_update_tick = jiffies;
> > > - __cpu_load_update(this_rq, load, 1, 1);
> > > +
> > > + if (tick_nohz_tick_stopped())
> > > + cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
> > > + else
> > > + cpu_load_update_periodic(this_rq, load);
> >
> > Considering it further, I wonder if needing it.
> > (Sorry if I missed something.)
> >
> > Case 1. tickless -> (scheduler_tick) -> tickless
> >
> > I am not sure for this case if the rq's load can be changed or not,
> > especially, if the rq's load can be changed *at this point*.
> > Please remind that the load[0] is set here.
>
> load[0] won't change because it's set by cpu_load_update_nohz_start().
> But all the other load[idx] need to be decayed further.
Ah. Right. Sched tick will be handled even in the case 1...
I like your patches. But I am still wondering if the sched tick handling is
necessary even in the case 1. Of course it's another problem though.
Thanks anyway,
Byungchul
>
> >
> > Case 2. tickless -> (scheduler_tick) -> restart tick
> >
> > Will be done by the tick restart routine when exiting irq.
> > -> no problem.
> >
> > Case 3. tick -> (scheduler_tick) -> tickless
> >
> > Same as before.
> > -> no problem.
> >
> > Case 4. tick -> (scheduler_tick) -> tick
> >
> > We can rely on regular schedule_tick().
> > -> no problem.
> >
>
> Thanks for your review!
