Re: [PATCH v7 02/15] sched/core: uclamp: Enforce last task UCLAMP_MAX

Patrick Bellasi
2019-03-14T17:06:19Z

On 13-Mar 17:29, Suren Baghdasaryan wrote:
> On Wed, Mar 13, 2019 at 9:16 AM Patrick Bellasi <patrick.bellasi@arm.com> wrote:
> >
> > On 13-Mar 15:12, Peter Zijlstra wrote:
> > > On Fri, Feb 08, 2019 at 10:05:41AM +0000, Patrick Bellasi wrote:
> > > > +static inline void uclamp_idle_reset(struct rq *rq, unsigned int clamp_id,
> > > > + unsigned int clamp_value)
> > > > +{
> > > > + /* Reset max-clamp retention only on idle exit */
> > > > + if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
> > > > + return;
> > > > +
> > > > + WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value);
> > > > +
> > > > + /*
> > > > + * This function is called for both UCLAMP_MIN (before) and UCLAMP_MAX
> > > > + * (after). The idle flag is reset only the second time, when we know
> > > > + * that UCLAMP_MIN has been already updated.
> > >
> > > Why do we care? That is, what is this comment trying to tell us.
> >
> > Right, the code is clear enough, I'll remove this comment.
>
> It would be probably even clearer if rq->uclamp_flags &=
> ~UCLAMP_FLAG_IDLE is done from inside uclamp_rq_inc after
> uclamp_rq_inc_id for both clamps is called.

Good point! I'll move it there to have something like:

---8<---
static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
{
unsigned int clamp_id;

if (unlikely(!p->sched_class->uclamp_enabled))
return;

for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id)
uclamp_rq_inc_id(p, rq, clamp_id);

/* Reset clamp holding when we have at least one RUNNABLE task */
if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
}
---8<---

--
#include <best/regards.h>

Patrick Bellasi