diff mbox series

[v4,2/2] sched/fair: Use helper function to access rd->overutilized

Message ID 20240301151725.874604-3-sshegde@linux.ibm.com
State New
Headers
Series sched/fair: Limit access to overutilized |

Commit Message

Shrikanth Hegde March 1, 2024, 3:17 p.m. UTC 
  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@linux.ibm.com>
---
 kernel/sched/fair.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

--
2.39.3

Comments

Qais Yousef March 3, 2024, 6:54 p.m. UTC | #1 
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@linux.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@layalina.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
>
Shrikanth Hegde March 4, 2024, 8:28 a.m. UTC | #2 
On 3/4/24 12:24 AM, Qais Yousef wrote:
> 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@linux.ibm.com>
> 
> Can we do the same for rd->overload too? A set_rd_overload_status() would be
> a nice addition too. Anyway.


We have some more experiments going around overload. 
For example, currently it is writing sg_status & SG_OVERLOAD without checking if it has 
changed first. On large systems that are not overloaded, that may help by reducing the 
bus traffic. 

I will pick up this after we have some more data on the above. 

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

Thank you.

> 
> Thanks!
diff mbox series

Patch

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;
 	}