linux-kernel - Re: [PATCH v8 04/16] sched/core: uclamp: Add system default clamps

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Date:   Tue, 7 May 2019 11:38:45 +0100
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-pm@...r.kernel.org,
        linux-api@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>
Subject: Re: [PATCH v8 04/16] sched/core: uclamp: Add system default clamps

On 17-Apr 17:51, Suren Baghdasaryan wrote:
> On Tue, Apr 2, 2019 at 3:42 AM Patrick Bellasi <patrick.bellasi@....com> wrote:

[...]

> > +/*
> > + * The effective clamp bucket index of a task depends on, by increasing
> > + * priority:
> > + * - the task specific clamp value, when explicitly requested from userspace
> > + * - the system default clamp value, defined by the sysadmin
> > + */
> > +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)
> 
> This function is not used anywhere AFAIKT.

Right, this is the dual of uclamp_eff_value() but, since we don't
actually use it in the corrent code, let's remove it and keep only the
latter.

> uclamp_eff_bucket_id() and
> uclamp_eff_value() look very similar, maybe they can be combined into
> one function returning struct uclamp_se?

I would prefer not since at the callsites of uclamp_eff_value() we
actually need just the value.

> > +{
> > +       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;
> > +}
> > +

-- 
#include <best/regards.h>

Patrick Bellasi