diff --git a/kernel/sched/core.c b/kernel/sched/core.c index d4edee72d793..d095fb1be6e9 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2511,6 +2511,24 @@ static inline bool rq_has_pinned_tasks(struct rq *rq) return rq->nr_pinned; } +static inline bool task_can_migrate_to_preferred(struct task_struct *p, int cpu) +{ + /* No need to migrate from a preferred CPU */ + if (cpu_preferred(cpu)) + return false; + + /* Only FAIR tasks honor preferred CPU state */ + if (unlikely(p->sched_class != &fair_sched_class)) + return false; + + /* Ignore preferred state if task affinity is changing */ + if (unlikely(!cpumask_test_cpu(task_cpu(p), p->cpus_ptr))) + return false; + + return cpumask_intersects_and(p->cpus_ptr, cpu_preferred_mask, + task_cpu_possible_mask(p)); +} + /* * Per-CPU kthreads are allowed to run on !active && online CPUs, see * __set_cpus_allowed_ptr() and select_fallback_rq(). @@ -2526,8 +2544,12 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) return cpu_online(cpu); /* Non kernel threads are not allowed during either online or offline. */ - if (!(p->flags & PF_KTHREAD)) + if (!(p->flags & PF_KTHREAD)) { + /* Try to use preferred CPU if task's affinity allows */ + if (task_can_migrate_to_preferred(p, cpu)) + return false; return cpu_active(cpu); + } /* KTHREAD_IS_PER_CPU is always allowed. */ if (kthread_is_per_cpu(p)) @@ -2537,7 +2559,11 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) if (cpu_dying(cpu)) return false; - /* But are allowed during online. */ + /* Try to keep unbound kthreads on a preferred CPU if possible. */ + if (task_can_migrate_to_preferred(p, cpu)) + return false; + + /* Otherwise, they are allowed to run on online CPU. */ return cpu_online(cpu); }