linux-kernel - Re: [PATCH v7 03/15] sched/core: uclamp: Add system default clamps

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Date:   Wed, 13 Mar 2019 21:10:10 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-api@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        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>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v7 03/15] sched/core: uclamp: Add system default clamps

On Wed, Mar 13, 2019 at 05:09:40PM +0000, Patrick Bellasi wrote:

> Yes, that should be possible... will look into splitting this out in
> v8 to have something like:
> 
> ---8<---
> struct uclamp_req {
> 	/* Clamp value "requested" by a scheduling entity */
> 	unsigned int value		: bits_per(SCHED_CAPACITY_SCALE);
> 	unsigned int bucket_id		: bits_per(UCLAMP_BUCKETS);
> 	unsigned int active		: 1;
> 	unsigned int user_defined	: 1;
> }
> 
> struct uclamp_eff {
> 	unsigned int value	        : bits_per(SCHED_CAPACITY_SCALE);
> 	unsigned int bucket_id	        : bits_per(UCLAMP_BUCKETS);
> }

No, have _1_ type. There is no point what so ever to splitting this.

Also, what's @user_defined about, I don't think I've seen that in the
parent patch.

> struct task_struct {
>         // ...
>         #ifdef CONFIG_UCLAMP_TASK
>                 struct uclamp_req uclamp_req[UCLAMP_CNT];
>                 struct uclamp_eff uclamp_eff[UCLAMP_CNT];

		struct uclamp_se uclamp[UCLAMP_CNT];
		struct uclamp_se uclamp_req[UCLAMP_CNT];

Where the first is the very same introduced in patch #1, and leaving it
in place avoids having to update the sites already using that (or start
#1 with the _eff name to avoid having to change things around?).

>         #endif
>         // ...
> }
> 
> static inline struct uclamp_eff
> uclamp_eff_get(struct task_struct *p, unsigned int clamp_id)
> {
>         struct uclamp_eff uc_eff = p->uclamp_eff[clamp_id];

just this ^, these lines seem like a superfluous duplication:

> 	uc_eff.bucket_id = p->uclamp_req[clamp_id].bucket_id;
> 	uc_eff.value = p->uclamp_req[clamp_id].value;


> 	if (unlikely(uc_eff.clamp_value > uclamp_default[clamp_id].value)) {
> 		uc_eff.clamp_value = uclamp_default[clamp_id].value;
> 		uc_eff.bucket_id = uclamp_default[clamp_id].bucket_id;

and:

		uc = uclamp_default[clamp_id];

> 	}
> 
>         return uc_eff;
> }
> 
> static inline void
> uclamp_eff_set(struct task_struct *p, unsigned int clamp_id)
> {
>         p->uclamp_eff[clamp_id] = uclamp_eff_get(p, clamp_id);
> }
> ---8<---
> 
> Is that what you mean ?

Getting there :-)