linux-kernel - Re: [PATCH 1/4] PM / devfreq: reuse system workqueue machanism

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Date:   Tue, 10 Dec 2019 10:41:27 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Kamil Konieczny <k.konieczny@...sung.com>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>
Subject: Re: [PATCH 1/4] PM / devfreq: reuse system workqueue machanism

On 12/9/19 11:44 PM, Kamil Konieczny wrote:
> There is no need for creating another workqueue, it is enough
> to reuse system_freezable_power_efficient one.
> 
> Signed-off-by: Kamil Konieczny <k.konieczny@...sung.com>
> ---
>  drivers/devfreq/devfreq.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 46a7ff7c2994..955949c6fc1f 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -1532,11 +1532,11 @@ static int __init devfreq_init(void)
>  		return PTR_ERR(devfreq_class);
>  	}
>  
> -	devfreq_wq = create_freezable_workqueue("devfreq_wq");
> +	devfreq_wq = system_freezable_power_efficient_wq;

It affect the behaviors of whole device drivers using devfreq subsystem.
It is not good to change the workqueue type without any reasonable
data like experiment result, power-consumption result and performance
result for almost device drivers using devfreq subsystem.

Are there any problem or any benefit to change workqueue type?

Actually, it is not simple to change the like just one device driver
because devfreq subsytem is very important for both performance
and power-consumption.

If you hope to change the feature related to both performance 
and power-consumption, please suggest the reasonable data
with fundamental reason.

So, I can't agree it.


>  	if (!devfreq_wq) {
>  		class_destroy(devfreq_class);
> -		pr_err("%s: couldn't create workqueue\n", __FILE__);
> -		return -ENOMEM;
> +		pr_err("%s: system_freezable_power_efficient_wq isn't initialized\n", __FILE__);
> +		return -EINVAL;
>  	}
>  	devfreq_class->dev_groups = devfreq_groups;
>  
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics