[PATCH] sched/fair: Remove stale references to LAST_BUDDY and SKIP_BUDDY

[PATCH] sched/fair: Remove stale references to LAST_BUDDY and SKIP_BUDDY

[Madadi Vineeth Reddy]

Commit 5e963f2bd465 ("sched/fair: Commit to EEVDF") removed the
functionality associated with LAST_BUDDY and SKIP_BUDDY. However,
some outdated references remained in the comments for pick_next_entity
and check_preempt_wakeup_fair. This commit cleans up those comments
to maintain clarity and correctness.

No functional change intended.

Co-developed-by: Adam Li <adamli@os.amperecomputing.com>
Signed-off-by: Adam Li <adamli@os.amperecomputing.com>
Signed-off-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
---
 kernel/sched/fair.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9dafb374d76d..379dbcbb24e9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5578,8 +5578,6 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags);
  * Pick the next process, keeping these things in mind, in this order:
  * 1) keep things fair between processes/task groups
  * 2) pick the "next" process, since someone really wants that to run
- * 3) pick the "last" process, for cache locality
- * 4) do not run the "skip" process, if something else is available
  */
 static struct sched_entity *
 pick_next_entity(struct rq *rq, struct cfs_rq *cfs_rq)
@@ -8780,9 +8778,7 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
 	 *
 	 * Note: this also catches the edge-case of curr being in a throttled
 	 * group (e.g. via set_curr_task), since update_curr() (in the
-	 * enqueue of curr) will have resulted in resched being set.  This
-	 * prevents us from potentially nominating it as a false LAST_BUDDY
-	 * below.
+	 * enqueue of curr) will have resulted in resched being set.
 	 */
 	if (test_tsk_need_resched(rq->curr))
 		return;
-- 
2.43.5

Re: [PATCH] sched/fair: Remove stale references to LAST_BUDDY and SKIP_BUDDY

[Madadi Vineeth Reddy]

Hi Peter, Ingo,

Ping.

Any thoughts on this? Can it be picked up?

Thanks,
Madadi Vineeth Reddy

On 14/03/25 14:31, Madadi Vineeth Reddy wrote:
> Commit 5e963f2bd465 ("sched/fair: Commit to EEVDF") removed the
> functionality associated with LAST_BUDDY and SKIP_BUDDY. However,
> some outdated references remained in the comments for pick_next_entity
> and check_preempt_wakeup_fair. This commit cleans up those comments
> to maintain clarity and correctness.
> 
> No functional change intended.
> 
> Co-developed-by: Adam Li <adamli@os.amperecomputing.com>
> Signed-off-by: Adam Li <adamli@os.amperecomputing.com>
> Signed-off-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
> ---
>  kernel/sched/fair.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 9dafb374d76d..379dbcbb24e9 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5578,8 +5578,6 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags);
>   * Pick the next process, keeping these things in mind, in this order:
>   * 1) keep things fair between processes/task groups
>   * 2) pick the "next" process, since someone really wants that to run
> - * 3) pick the "last" process, for cache locality
> - * 4) do not run the "skip" process, if something else is available
>   */
>  static struct sched_entity *
>  pick_next_entity(struct rq *rq, struct cfs_rq *cfs_rq)
> @@ -8780,9 +8778,7 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
>  	 *
>  	 * Note: this also catches the edge-case of curr being in a throttled
>  	 * group (e.g. via set_curr_task), since update_curr() (in the
> -	 * enqueue of curr) will have resulted in resched being set.  This
> -	 * prevents us from potentially nominating it as a false LAST_BUDDY
> -	 * below.
> +	 * enqueue of curr) will have resulted in resched being set.
>  	 */
>  	if (test_tsk_need_resched(rq->curr))
>  		return;

Re: [PATCH] sched/fair: Remove stale references to LAST_BUDDY and SKIP_BUDDY

[Madadi Vineeth Reddy]

On 13/04/25 09:40, Madadi Vineeth Reddy wrote:
> Hi Peter, Ingo,
> 
> Ping.
> 
> Any thoughts on this? Can it be picked up?
> 
> Thanks,
> Madadi Vineeth Reddy

Hi Peter, Ingo,

This still applies cleanly on top of tip/sched/core.

Could this be considered for merging?

Thank you,
Madadi Vineeth Reddy

> 
> On 14/03/25 14:31, Madadi Vineeth Reddy wrote:
>> Commit 5e963f2bd465 ("sched/fair: Commit to EEVDF") removed the
>> functionality associated with LAST_BUDDY and SKIP_BUDDY. However,
>> some outdated references remained in the comments for pick_next_entity
>> and check_preempt_wakeup_fair. This commit cleans up those comments
>> to maintain clarity and correctness.
>>
>> No functional change intended.
>>
>> Co-developed-by: Adam Li <adamli@os.amperecomputing.com>
>> Signed-off-by: Adam Li <adamli@os.amperecomputing.com>
>> Signed-off-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
>> ---
>>  kernel/sched/fair.c | 6 +-----
>>  1 file changed, 1 insertion(+), 5 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 9dafb374d76d..379dbcbb24e9 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -5578,8 +5578,6 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags);
>>   * Pick the next process, keeping these things in mind, in this order:
>>   * 1) keep things fair between processes/task groups
>>   * 2) pick the "next" process, since someone really wants that to run
>> - * 3) pick the "last" process, for cache locality
>> - * 4) do not run the "skip" process, if something else is available
>>   */
>>  static struct sched_entity *
>>  pick_next_entity(struct rq *rq, struct cfs_rq *cfs_rq)
>> @@ -8780,9 +8778,7 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
>>  	 *
>>  	 * Note: this also catches the edge-case of curr being in a throttled
>>  	 * group (e.g. via set_curr_task), since update_curr() (in the
>> -	 * enqueue of curr) will have resulted in resched being set.  This
>> -	 * prevents us from potentially nominating it as a false LAST_BUDDY
>> -	 * below.
>> +	 * enqueue of curr) will have resulted in resched being set.
>>  	 */
>>  	if (test_tsk_need_resched(rq->curr))
>>  		return;
>