netdev - Re: [PATCH] sunrpc: queue work on system_power_efficient

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Date:   Thu, 1 Sep 2016 14:46:35 -0400
From:   Anna Schumaker <Anna.Schumaker@...app.com>
To:     Chunyan Zhang <zhang.lyra@...il.com>,
        <trond.myklebust@...marydata.com>, <anna.schumaker@...app.com>,
        <davem@...emloft.net>
CC:     <linux-nfs@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <ke.wang@...eadtrum.com>
Subject: Re: [PATCH] sunrpc: queue work on system_power_efficient_wq

On 09/01/2016 03:30 AM, Chunyan Zhang wrote:
> From: Ke Wang <ke.wang@...eadtrum.com>
> 
> sunrpc uses workqueue to clean cache regulary. There is no real dependency
> of executing work on the cpu which queueing it.
> 
> On a idle system, especially for a heterogeneous systems like big.LITTLE,
> it is observed that the big idle cpu was woke up many times just to service
> this work, which against the principle of power saving. It would be better
> if we can schedule it on a cpu which the scheduler believes to be the most
> appropriate one.
> 
> After apply this patch, system_wq will be replaced by
> system_power_efficient_wq for sunrpc. This functionality is enabled when
> CONFIG_WQ_POWER_EFFICIENT is selected.

Makes sense to me, but I'm a little surprised that there isn't a "schedule_delayed_power_efficient_work()" function to match how the normal workqueue is used.

Thanks,
Anna

> 
> Signed-off-by: Ke Wang <ke.wang@...eadtrum.com>
> ---
>  net/sunrpc/cache.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> index 4d8e11f..8aabe12 100644
> --- a/net/sunrpc/cache.c
> +++ b/net/sunrpc/cache.c
> @@ -353,7 +353,7 @@ void sunrpc_init_cache_detail(struct cache_detail *cd)
>  	spin_unlock(&cache_list_lock);
>  
>  	/* start the cleaning process */
> -	schedule_delayed_work(&cache_cleaner, 0);
> +	queue_delayed_work(system_power_efficient_wq, &cache_cleaner, 0);
>  }
>  EXPORT_SYMBOL_GPL(sunrpc_init_cache_detail);
>  
> @@ -476,7 +476,8 @@ static void do_cache_clean(struct work_struct *work)
>  		delay = 0;
>  
>  	if (delay)
> -		schedule_delayed_work(&cache_cleaner, delay);
> +		queue_delayed_work(system_power_efficient_wq,
> +				   &cache_cleaner, delay);
>  }
>  
>  
>