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From: Peter Zijlstra <peterz@infradead.org>
To: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-api@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
	Tejun Heo <tj@kernel.org>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Paul Turner <pjt@google.com>,
	Quentin Perret <quentin.perret@arm.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Juri Lelli <juri.lelli@redhat.com>, Todd Kjos <tkjos@google.com>,
	Joel Fernandes <joelaf@google.com>,
	Steve Muckle <smuckle@google.com>,
	Suren Baghdasaryan <surenb@google.com>
Subject: Re: [PATCH v7 03/15] sched/core: uclamp: Add system default clamps
Date: Wed, 13 Mar 2019 15:32:40 +0100	[thread overview]
Message-ID: <20190313143240.GH5922@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190208100554.32196-4-patrick.bellasi@arm.com>

On Fri, Feb 08, 2019 at 10:05:42AM +0000, Patrick Bellasi wrote:

> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 45460e7a3eee..447261cd23ba 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -584,14 +584,32 @@ struct sched_dl_entity {
>   * Utilization clamp for a scheduling entity
>   * @value:		clamp value "requested" by a se
>   * @bucket_id:		clamp bucket corresponding to the "requested" value
> + * @effective:		clamp value and bucket actually "assigned" to the se
> + * @active:		the se is currently refcounted in a rq's bucket
>   *
> + * Both bucket_id and effective::bucket_id are the index of the clamp bucket
> + * matching the corresponding clamp value which are pre-computed and stored to
> + * avoid expensive integer divisions from the fast path.
> + *
> + * The active bit is set whenever a task has got an effective::value assigned,
> + * which can be different from the user requested clamp value. This allows to
> + * know a task is actually refcounting the rq's effective::bucket_id bucket.
>   */
>  struct uclamp_se {
> +	/* 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;
> +	/*
> +	 * Clamp value "obtained" by a scheduling entity.
> +	 *
> +	 * This cache the actual clamp value, possibly enforced by system
> +	 * default clamps, a task is subject to while enqueued in a rq.
> +	 */
> +	struct {
> +		unsigned int value	: bits_per(SCHED_CAPACITY_SCALE);
> +		unsigned int bucket_id	: bits_per(UCLAMP_BUCKETS);
> +	} effective;

I still think that this effective thing is backwards.

The existing code already used @value and @bucket_id as 'effective' and
you're now changing all that again. This really doesn't make sense to
me.

Also; if you don't add it inside struct uclamp_se, but add a second
instance,

>  };
>  #endif /* CONFIG_UCLAMP_TASK */
>  


> @@ -803,6 +811,70 @@ static inline void uclamp_rq_update(struct rq *rq, unsigned int clamp_id,
>  	WRITE_ONCE(rq->uclamp[clamp_id].value, max_value);
>  }
>  
> +/*
> + * 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
> + *
> + * As a side effect, update the task's effective value:
> + *    task_struct::uclamp::effective::value
> + * to represent the clamp value of the task effective bucket index.
> + */
> +static inline void
> +uclamp_effective_get(struct task_struct *p, unsigned int clamp_id,
> +		     unsigned int *clamp_value, unsigned int *bucket_id)
> +{
> +	/* Task specific clamp value */
> +	*bucket_id = p->uclamp[clamp_id].bucket_id;
> +	*clamp_value = p->uclamp[clamp_id].value;
> +
> +	/* Always apply system default restrictions */
> +	if (unlikely(*clamp_value > uclamp_default[clamp_id].value)) {
> +		*clamp_value = uclamp_default[clamp_id].value;
> +		*bucket_id = uclamp_default[clamp_id].bucket_id;
> +	}
> +}

you can avoid horrors like this and simply return a struct uclamp_se by
value.



  reply	other threads:[~2019-03-13 14:32 UTC|newest]

Thread overview: 84+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-08 10:05 [PATCH v7 00/15] Add utilization clamping support Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 01/15] sched/core: uclamp: Add CPU's clamp buckets refcounting Patrick Bellasi
2019-03-12 12:52   ` Dietmar Eggemann
2019-03-13 15:15     ` Patrick Bellasi
2019-03-13 21:01       ` Suren Baghdasaryan
2019-03-14 14:54         ` Patrick Bellasi
2019-03-14 15:00       ` Patrick Bellasi
2019-03-12 15:20   ` Peter Zijlstra
2019-03-12 15:50     ` Patrick Bellasi
2019-03-13  8:19       ` Peter Zijlstra
2019-03-13 11:37         ` Patrick Bellasi
2019-03-13 13:40   ` Peter Zijlstra
2019-03-13 16:12     ` Patrick Bellasi
2019-03-13 17:22       ` Peter Zijlstra
2019-03-13 18:22         ` Patrick Bellasi
2019-03-13 19:48       ` Peter Zijlstra
2019-03-14 12:13         ` Patrick Bellasi
2019-03-14 13:32           ` Peter Zijlstra
2019-03-14 15:07             ` Patrick Bellasi
2019-03-14 19:18               ` Peter Zijlstra
2019-03-13 13:52   ` Peter Zijlstra
2019-03-13 15:59     ` Patrick Bellasi
2019-03-13 19:30       ` Peter Zijlstra
2019-03-14 11:03         ` Patrick Bellasi
2019-03-14 13:27           ` Peter Zijlstra
2019-03-13 19:39       ` Peter Zijlstra
2019-03-14 11:18         ` Patrick Bellasi
2019-03-13 21:23     ` Suren Baghdasaryan
2019-03-14 12:43       ` Patrick Bellasi
2019-03-13 14:06   ` Peter Zijlstra
2019-03-13 15:28     ` Patrick Bellasi
2019-03-13 14:09   ` Peter Zijlstra
2019-03-13 15:23     ` Patrick Bellasi
2019-03-13 19:46       ` Peter Zijlstra
2019-03-13 21:08         ` Suren Baghdasaryan
2019-03-14 12:22           ` Patrick Bellasi
2019-03-14 11:45         ` Patrick Bellasi
2019-03-13 21:32   ` Suren Baghdasaryan
2019-03-14 14:46     ` Patrick Bellasi
2019-03-14 15:29       ` Suren Baghdasaryan
2019-03-14 15:40         ` Patrick Bellasi
2019-03-14 16:39           ` Suren Baghdasaryan
2019-02-08 10:05 ` [PATCH v7 02/15] sched/core: uclamp: Enforce last task UCLAMP_MAX Patrick Bellasi
2019-03-13 14:10   ` Peter Zijlstra
2019-03-13 16:20     ` Patrick Bellasi
2019-03-13 17:29       ` Peter Zijlstra
2019-03-13 18:29         ` Patrick Bellasi
2019-03-13 14:12   ` Peter Zijlstra
2019-03-13 16:16     ` Patrick Bellasi
2019-03-14  0:29       ` Suren Baghdasaryan
2019-03-14 17:06         ` Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 03/15] sched/core: uclamp: Add system default clamps Patrick Bellasi
2019-03-13 14:32   ` Peter Zijlstra [this message]
2019-03-13 17:09     ` Patrick Bellasi
2019-03-13 19:58       ` Peter Zijlstra
2019-03-13 20:10       ` Peter Zijlstra
2019-03-15 13:41         ` Patrick Bellasi
2019-03-13 20:13   ` Peter Zijlstra
2019-03-13 20:18   ` Peter Zijlstra
2019-03-18 12:18     ` Patrick Bellasi
2019-03-18 13:10       ` Peter Zijlstra
2019-03-18 14:21         ` Patrick Bellasi
2019-03-18 14:29           ` Peter Zijlstra
2019-02-08 10:05 ` [PATCH v7 04/15] sched/core: Allow sched_setattr() to use the current policy Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 05/15] sched/core: uclamp: Extend sched_setattr() to support utilization clamping Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 06/15] sched/core: uclamp: Reset uclamp values on RESET_ON_FORK Patrick Bellasi
2019-03-13 20:52   ` Peter Zijlstra
2019-03-18 12:58     ` Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 07/15] sched/core: uclamp: Set default clamps for RT tasks Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 08/15] sched/cpufreq: uclamp: Add clamps for FAIR and " Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 09/15] sched/core: uclamp: Add uclamp_util_with() Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 10/15] sched/fair: uclamp: Add uclamp support to energy_compute() Patrick Bellasi
2019-03-06 17:21   ` Quentin Perret
2019-03-18 15:19     ` Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 11/15] sched/core: uclamp: Extend CPU's cgroup controller Patrick Bellasi
2019-02-14 15:48   ` Tejun Heo
2019-03-19 10:00     ` Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 12/15] sched/core: uclamp: Propagate parent clamps Patrick Bellasi
2019-03-14 16:17   ` Suren Baghdasaryan
2019-03-18 16:54     ` Patrick Bellasi
2019-03-18 16:58       ` Suren Baghdasaryan
2019-02-08 10:05 ` [PATCH v7 13/15] sched/core: uclamp: Propagate system defaults to root group Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 14/15] sched/core: uclamp: Use TG's clamps to restrict TASK's clamps Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 15/15] sched/core: uclamp: Update CPU's refcount on TG's clamp changes Patrick Bellasi

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