Re: [PATCH 2/3] sched/fair: Rename group_imbalanced to group_pinned_task

[Tim Chen]

On Mon, 2026-09-28 at 12:20 +0800, Jemmy Wong wrote:
> The name dates back to the original group_imb heuristic, which flagged
> a group when the load difference between its busiest and idlest CPU
> exceeded the average task load. Commit 6263322c5e8f ("sched/fair:
> Rewrite group_imb trigger") replaced that heuristic: the flag is now
> set only when a lower domain fails to balance because tasks are pinned
> by cpus_ptr (LBF_SOME_PINNED), and kept while all tasks are pinned
> (LBF_ALL_PINNED). The name was carried over unchanged and later became
> group_imbalanced in commit 0b0695f2b34a ("sched/fair: Rework
> load_balance()").
> 
> Today the name no longer matches the condition:
> 
>  - group_classify() checks group_overloaded first, so a group whose
>    load really is skewed is usually not classified as imbalanced,
>    while a flagged group may carry a single extra task.
> 
>  - calculate_imbalance() does not measure any imbalance for this type;
>    it moves one task (migrate_task, imbalance = 1).
> 
>  - Elsewhere in fair.c "imbalance" consistently means the amount of
>    load to move (env->imbalance, imbalance_pct, calculate_imbalance(),
>    the lb_imbalance_* schedstats), and imbalanced_active_balance() uses
>    "imbalanced" for repeated balance failures, unrelated to this flag.
> 
> Rename it to group_pinned_task, which describes the condition that
> raises it and follows the adjective_noun pattern of group_misfit_task.
> The enum is local to fair.c, so no tracepoint, schedstat or other
> user-visible interface is affected.
> 
> No functional change.
> 
> Signed-off-by: Jemmy Wong <jemmywong512@xxxxxxxxx>
> ---
>  kernel/sched/fair.c | 30 +++++++++++++++---------------
>  1 file changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index f9ddcecfd19d..aa63950976aa 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -10363,7 +10363,7 @@ enum group_type {
>  	 * The tasks' affinity constraints previously prevented the scheduler
>  	 * from balancing the load across the system.
>  	 */
> -	group_imbalanced,
> +	group_pinned_task,

I believe we are trying to fix imbalance due to pinned tasks.
Perhaps group_pinned_imbalance is more descriptive.

Tim