linux-kernel - Re: [RFCv3 PATCH 01/48] sched: add utilization_avg

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Message-ID: <54DB17CC.6050009@linux.vnet.ibm.com>
Date:	Wed, 11 Feb 2015 14:20:20 +0530
From:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To:	Morten Rasmussen <morten.rasmussen@....com>, peterz@...radead.org,
	mingo@...hat.com, vincent.guittot@...aro.org
CC:	dietmar.eggemann@....com, yuyang.du@...el.com,
	mturquette@...aro.org, nico@...aro.org, rjw@...ysocki.net,
	juri.lelli@....com, linux-kernel@...r.kernel.org,
	Paul Turner <pjt@...gle.com>, Ben Segall <bsegall@...gle.com>
Subject: Re: [RFCv3 PATCH 01/48] sched: add utilization_avg_contrib

On 02/05/2015 12:00 AM, Morten Rasmussen wrote:
> From: Vincent Guittot <vincent.guittot@...aro.org>
> 
> Add new statistics which reflect the average time a task is running on the CPU
> and the sum of these running time of the tasks on a runqueue. The latter is
> named utilization_load_avg.
> 
> This patch is based on the usage metric that was proposed in the 1st
> versions of the per-entity load tracking patchset by Paul Turner
> <pjt@...gle.com> but that has be removed afterwards. This version differs from
> the original one in the sense that it's not linked to task_group.
> 
> The rq's utilization_load_avg will be used to check if a rq is overloaded or
> not instead of trying to compute how many tasks a group of CPUs can handle.
> 
> Rename runnable_avg_period into avg_period as it is now used with both
> runnable_avg_sum and running_avg_sum
> 
> Add some descriptions of the variables to explain their differences
> 
> cc: Paul Turner <pjt@...gle.com>
> cc: Ben Segall <bsegall@...gle.com>
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> Acked-by: Morten Rasmussen <morten.rasmussen@....com>
> ---
>  include/linux/sched.h | 21 ++++++++++++---
>  kernel/sched/debug.c  | 10 ++++---
>  kernel/sched/fair.c   | 74 ++++++++++++++++++++++++++++++++++++++++-----------
>  kernel/sched/sched.h  |  8 +++++-
>  4 files changed, 89 insertions(+), 24 deletions(-)

> +static inline void __update_task_entity_utilization(struct sched_entity *se)
> +{
> +	u32 contrib;
> +
> +	/* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
> +	contrib = se->avg.running_avg_sum * scale_load_down(SCHED_LOAD_SCALE);
> +	contrib /= (se->avg.avg_period + 1);
> +	se->avg.utilization_avg_contrib = scale_load(contrib);
> +}
> +
> +static long __update_entity_utilization_avg_contrib(struct sched_entity *se)
> +{
> +	long old_contrib = se->avg.utilization_avg_contrib;
> +
> +	if (entity_is_task(se))
> +		__update_task_entity_utilization(se);
> +
> +	return se->avg.utilization_avg_contrib - old_contrib;

When the entity is not a task, shouldn't the utilization_avg_contrib be
updated like this :

se->avg.utilization_avg_contrib = group_cfs_rq(se)->utilization_load_avg
? and then the delta with old_contrib be passed ?

Or is this being updated someplace that I have missed ?

Regards
Preeti U Murthy

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