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SubjectRe: [PATCH v8 04/16] sched/core: uclamp: Add system default clamps
On Wed, May 08, 2019 at 09:07:33PM +0200, Peter Zijlstra wrote:
> On Tue, Apr 02, 2019 at 11:41:40AM +0100, Patrick Bellasi wrote:
> > +static inline struct uclamp_se
> > +uclamp_eff_get(struct task_struct *p, unsigned int clamp_id)
> > +{
> > + struct uclamp_se uc_req = p->uclamp_req[clamp_id];
> > + struct uclamp_se uc_max = uclamp_default[clamp_id];
> > +
> > + /* System default restrictions always apply */
> > + if (unlikely(uc_req.value > uc_max.value))
> > + return uc_max;
> > +
> > + return uc_req;
> > +}
> > +
> > +static inline unsigned int
> > +uclamp_eff_bucket_id(struct task_struct *p, unsigned int clamp_id)
> > +{
> > + struct uclamp_se uc_eff;
> > +
> > + /* Task currently refcounted: use back-annotated (effective) bucket */
> > + if (p->uclamp[clamp_id].active)
> > + return p->uclamp[clamp_id].bucket_id;
> > +
> > + uc_eff = uclamp_eff_get(p, clamp_id);
> > +
> > + return uc_eff.bucket_id;
> > +}
> > +
> > +unsigned int uclamp_eff_value(struct task_struct *p, unsigned int clamp_id)
> > +{
> > + struct uclamp_se uc_eff;
> > +
> > + /* Task currently refcounted: use back-annotated (effective) value */
> > + if (p->uclamp[clamp_id].active)
> > + return p->uclamp[clamp_id].value;
> > +
> > + uc_eff = uclamp_eff_get(p, clamp_id);
> > +
> > + return uc_eff.value;
> > +}
>
> This is 'wrong' because:
>
> uclamp_eff_value(p,id) := uclamp_eff(p,id).value

Clearly I means to say the above does not hold with the given
implementation, while the naming would suggest it does.

> Which seems to suggest the uclamp_eff_*() functions want another name.
>
> Also, suppose the above would be true; does GCC really generate better
> code for the LHS compared to the RHS?

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