On Thu, Feb 23, 2017 at 12:18:48PM +0900, byungchul.park wrote:
> > Current code handles this by replenishing a runtime in hrtimer callback
> > for deadline. But this approach has room for improvement in two ways:
> >
> > 1. No need to keep the hrtimer for a sleep task because it can be
> > handled when waking it up.
> >
> > 2. It will be replenished twice unnecessarily if the task sleeps for
> > long time so that the deadline, assigned in the hrtimer callback,
> > also passed. In other words, one happens in the callback and the
> > other happens in update_dl_entiry() when waking it up.
I wanted to enhance not only the second but also the first, so remove
the unnecessary timer overhead for sleep tasks. It's possible but it
makes code too complecated and I won't do that.
I will resend a patch doing only the second one at the next spin.
Thank you,
Byungchul
> > @@ -981,6 +983,9 @@ static void dequeue_task_dl(struct rq *rq, struct
> > task_struct *p, int flags)
> > {
> > update_curr_dl(rq);
> > __dequeue_task_dl(rq, p, flags);
> > +
> > + if (flags & DEQUEUE_SLEEP)
> > + hrtimer_try_to_cancel(&p->dl.dl_timer);
>
> Sorry. I found I might have made a mistake. I might have to re-start the
> timer when waking it up if necessary. Let me think more.
