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

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Date:	Thu, 12 Feb 2015 02:07:31 +0100
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc:	Morten Rasmussen <morten.rasmussen@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Yuyang Du <yuyang.du@...el.com>,
	Michael Turquette <mturquette@...aro.org>,
	Nicolas Pitre <nico@...aro.org>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	Juri Lelli <juri.lelli@....com>,
	linux-kernel <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 11 February 2015 at 09:50, Preeti U Murthy <preeti@...ux.vnet.ibm.com> wrote:
> 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 ?

Patch 02 handles the contribution of entities which are not tasks.

Regards,
Vincent

>
> Regards
> Preeti U Murthy
>
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