linux-kernel - Re: [RFC] sched: Distinguish between idle

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Date:   Mon, 7 May 2018 17:15:16 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Rohit Jain <rohit.k.jain@...cle.com>, matt@...eblueprint.co.uk,
        peterz@...radead.org
Cc:     mingo@...nel.org, dhaval.giani@...cle.com,
        subhra.mazumdar@...cle.com, steven.sistare@...cle.com,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC] sched: Distinguish between idle_cpu calls based on desired
 effect

On 05/07/2018 04:41 PM, Rohit Jain wrote:
> In commit 247f2f6f3c706b40b5f3886646f3eb53671258bf we distinguish
> between idle_cpu when the vcpu is not running for scheduling threads.
> However, idle_cpu function is used at other places for actually checking
> whether the state of the CPU is idle or not. Hence splitting the use of
> that function based on the desired return value.
> 
> Signed-off-by: Rohit Jain <rohit.k.jain@...cle.com>
> ---
>  include/linux/sched.h |  1 +
>  kernel/sched/core.c   | 14 ++++++++++++++
>  kernel/sched/fair.c   | 20 ++++++++++----------
>  3 files changed, 25 insertions(+), 10 deletions(-)
> 

> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 71bdb86..171e160 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -4028,6 +4028,20 @@ int idle_cpu(int cpu)
>  		return 0;
>  #endif
>  
> +	return 1;
> +}
> +
> +/**
> + * idle_cpu - is a given CPU idle for enqueuing work.

    * available_idle_cpu -

> + * @cpu: the processor in question.
> + *
> + * Return: 1 if the CPU is currently idle. 0 otherwise.
> + */
> +int available_idle_cpu(int cpu)
> +{
> +	if (!idle_cpu(cpu))
> +		return 0;
> +
>  	if (vcpu_is_preempted(cpu))
>  		return 0;
>  


-- 
~Randy