Re: [patch] CFS scheduler, -v15

[Dmitry Adamushko]

On 06/06/07, Srivatsa Vaddagiri <vatsa@xxxxxxxxxx> wrote:
> [ ... ]
> > > This way, on RT -> NORMAL transition.. some 'delta_exec' ( between
> > > deactivate_task() ---> activate_task() ) will be accounted later as if
> > > the task was 'sched_fair_class' during this time.. which I think makes
> > > some sense. What do you think?
> > >
> >
> > Why not do it explicitly in __setscheduler() if the new policy is SCHED_NORMAL
> > or SCHED_BATCH.
>
> Yes this is the approach I prefer, because we burden the fast/normal
> path less that way (RT->NORMAL transition is not common).

I don't think that rt_sched_class :: dequeue_task_rt() is in any of
such "fast pathes" that we should really care about an additional
math. operation.

If this approach is ok, logically-wise (no side effects from a short
'delta_exec', esp. on RT -> NORMAL).. I think it's better as it keeps
the 'sched_class' interface simpler.

> That's why I
> was considering a set_curr_task() method in fair_sched_class which will
> be invoked in __setscheduler() if the new policy of currently running
> task happens to be SCHED_NORMAL/BATCH. Alternately if the new policy of
> currently running task happens to be SCHED_FIFO (and its old policy was
> SCHED_NORMAL) we need to invoke put_prev_task() method (so that
> fair_clock etc is updated based on outgoing task's execution time in
> SCHED_NORMAL class).

rt_sched_class :: put_prev_task() from __setscheduler() ? But it's not
supposed to be called from here, logically-wise. You just rely on its
current behavior (which is only about updating 'exec_start' and
'exec_sum') -- that's just bad. Maybe I misunderatood your intention
though..


> --
> Regards,
> vatsa

--
Best regards,
Dmitry Adamushko
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