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

[Jemmy Wong]

Hi Tim,

Thanks for the review.


> On Oct 2, 2026, at 5:54 AM, Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> wrote:
> 
> 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

Agreed. I'll use group_pinned_imb in v2, which keeps the "pinned"
qualifier and matches the short "imb" naming. I'll also rename
sgc->imbalance to sgc->pinned_imb and its reader to sg_pinned_imb() in
patch 3 to match.

Thanks,
Jemmy