linux-kernel - Re: [PATCH v4 2/2] sched/fair: Use helper function to access rd->overutilized

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Date: Sun, 3 Mar 2024 18:54:41 +0000
From: Qais Yousef <qyousef@...alina.io>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: mingo@...nel.org, peterz@...radead.org, vincent.guittot@...aro.org,
	yu.c.chen@...el.com, dietmar.eggemann@....com,
	linux-kernel@...r.kernel.org, nysal@...ux.ibm.com,
	aboorvad@...ux.ibm.com, srikar@...ux.ibm.com, vschneid@...hat.com,
	pierre.gondois@....com, morten.rasmussen@....com
Subject: Re: [PATCH v4 2/2] sched/fair: Use helper function to access
 rd->overutilized

On 03/01/24 20:47, Shrikanth Hegde wrote:
> Overutilized field is accessed directly in multiple places.
> So it could use a helper function. That way one might be more
> informed that it needs to be used only in case of EAS.
> 
> No change in functionality intended.
> 
> Signed-off-by: Shrikanth Hegde <sshegde@...ux.ibm.com>

Can we do the same for rd->overload too? A set_rd_overload_status() would be
a nice addition too. Anyway.

Reviewed-by: Qais Yousef <qyousef@...alina.io>


Thanks!

--
Qais Yousef

> ---
>  kernel/sched/fair.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index a71f8a1506e4..650909a648d0 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6670,6 +6670,15 @@ static inline bool cpu_overutilized(int cpu)
>  	return !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu);
>  }
> 
> +/*
> + * Ensure that caller can do EAS. overutilized value
> + * make sense only if EAS is enabled
> + */
> +static inline int is_rd_overutilized(struct root_domain *rd)
> +{
> +	return READ_ONCE(rd->overutilized);
> +}
> +
>  static inline void set_rd_overutilized_status(struct root_domain *rd,
>  					      unsigned int status)
>  {
> @@ -6686,13 +6695,14 @@ static inline void check_update_overutilized_status(struct rq *rq)
>  	if (!sched_energy_enabled())
>  		return;
> 
> -	if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu))
> +	if (!is_rd_overutilized(rq->rd) && cpu_overutilized(rq->cpu))
>  		set_rd_overutilized_status(rq->rd, SG_OVERUTILIZED);
>  }
>  #else
>  static inline void check_update_overutilized_status(struct rq *rq) { }
>  static inline void set_rd_overutilized_status(struct root_domain *rd,
>  					      unsigned int status) { }
> +static inline int is_rd_overutilized(struct root_domain *rd) { }
>  #endif
> 
>  /* Runqueue only has SCHED_IDLE tasks enqueued */
> @@ -7974,7 +7984,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
> 
>  	rcu_read_lock();
>  	pd = rcu_dereference(rd->pd);
> -	if (!pd || READ_ONCE(rd->overutilized))
> +	if (!pd || is_rd_overutilized(rd))
>  		goto unlock;
> 
>  	/*
> @@ -10859,7 +10869,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
>  	if (sched_energy_enabled()) {
>  		struct root_domain *rd = env->dst_rq->rd;
> 
> -		if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
> +		if (rcu_dereference(rd->pd) && !is_rd_overutilized(rd))
>  			goto out_balanced;
>  	}
> 
> --
> 2.39.3
>