linux-kernel - Re: [PATCH v2 1/2] sched/fair: Only compute base_energy

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Date:   Fri, 30 Apr 2021 12:03:56 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     Pierre.Gondois@....com
Cc:     linux-kernel@...r.kernel.org, xuewen.yan@...soc.com,
        qperret@...rret.net, dietmar.eggemann@....com,
        Vincent.Donnefort@....com, mingo@...hat.com, peterz@...radead.org,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com
Subject: Re: [PATCH v2 1/2] sched/fair: Only compute base_energy_pd if
 necessary

Hi Pierre,

On 4/29/21 11:19 AM, Pierre.Gondois@....com wrote:
> From: Pierre Gondois <Pierre.Gondois@....com>
> 
> find_energy_efficient_cpu() searches the best energy CPU
> to place a task on. To do so, the energy of each performance domain
> (pd) is computed w/ and w/o the task placed in each pd.
> 
> The energy of a pd w/o the task (base_energy_pd) is computed prior
> knowing whether a CPU is available in the pd.
> 
> Move the base_energy_pd computation after looping through the CPUs
> of a pd and only computes it if at least one CPU is available.
> 
> Suggested-by: Xuewen Yan <xuewen.yan@...soc.com>
> Signed-off-by: Pierre Gondois <Pierre.Gondois@....com>
> ---
>   kernel/sched/fair.c | 38 ++++++++++++++++++++++----------------
>   1 file changed, 22 insertions(+), 16 deletions(-)
> 

Make sense. I will speed-up feec() on Android devices for tasks
being moved into 'background' cgroup (limited to subset of CPUs,
e.g. to only Little cores). LGTM.

Reviewed-by: Lukasz Luba <lukasz.luba@....com>

Regards,
Lukasz