[patch V3 08/20] sched/mmcid: Use cpumask_weighted_or()

Thomas Gleixner
2025-10-29T13:09:11Z

Use cpumask_weighted_or() instead of cpumask_or() and cpumask_weight() on
the result, which walks the same bitmap twice. Results in 10-20% less
cycles, which reduces the runqueue lock hold time.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/sched/core.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10375,6 +10375,7 @@ void call_trace_sched_update_nr_running(
static inline void mm_update_cpus_allowed(struct mm_struct *mm, const struct cpumask *affmsk)
{
struct cpumask *mm_allowed;
+ unsigned int weight;

if (!mm)
return;
@@ -10385,8 +10386,8 @@ static inline void mm_update_cpus_allowe
*/
guard(raw_spinlock)(&mm->mm_cid.lock);
mm_allowed = mm_cpus_allowed(mm);
- cpumask_or(mm_allowed, mm_allowed, affmsk);
- WRITE_ONCE(mm->mm_cid.nr_cpus_allowed, cpumask_weight(mm_allowed));
+ weight = cpumask_weighted_or(mm_allowed, mm_allowed, affmsk);
+ WRITE_ONCE(mm->mm_cid.nr_cpus_allowed, weight);
}

void sched_mm_cid_exit_signals(struct task_struct *t)