diff --git a/kernel/sched/core.c b/kernel/sched/core.c index d095fb1be6e9..0e40055c2367 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5829,6 +5829,9 @@ void sched_tick(void) unsigned long hw_pressure; u64 resched_latency; + if (!cpu_preferred(cpu)) + sched_push_current_non_preferred_cpu(rq); + if (housekeeping_cpu(cpu, HK_TYPE_KERNEL_NOISE)) arch_scale_freq_tick(); @@ -11253,3 +11256,83 @@ void sched_change_end(struct sched_change_ctx *ctx) p->sched_class->prio_changed(rq, p, ctx->prio); } } + +#ifdef CONFIG_PREFERRED_CPU +static DEFINE_PER_CPU(struct cpu_stop_work, npc_push_task_work); + +static int sched_non_preferred_cpu_push_stop(void *arg) +{ + struct task_struct *p = arg; + struct rq *rq = this_rq(); + struct rq_flags rf; + int cpu; + + if (cpu_preferred(rq->cpu)) { + scoped_guard(rq_lock_irqsave, rq) + rq->npc_push_work_pending = false; + put_task_struct(p); + return 0; + } + + scoped_guard (raw_spinlock_irq, &p->pi_lock) { + /* + * select_fallback_rq() may acquire the rq lock in case of + * fallback. So call it before grabbing rq lock. If the task + * migrates to another CPU before the rq lock is acquired, + * subsequent validation of task's current rq will help to + * safely bail out. + */ + cpu = select_fallback_rq(rq->cpu, p); + rq_lock(rq, &rf); + rq->npc_push_work_pending = false; + update_rq_clock(rq); + context_unsafe_alias(rq); + + if (task_rq(p) == rq && task_on_rq_queued(p)) + rq = __migrate_task(rq, &rf, p, cpu); + rq_unlock(rq, &rf); + } + + put_task_struct(p); + return 0; +} + +/* + * Push the current task running on non-preferred CPU(npc). + * Using this non preferred CPU will lead to more contention + * in the host. So it is better not to use this CPU. + * + * Since task is running, call a stopper to push the task out. This is + * similar to how task moves during hotplug. In select_fallback_rq() a + * preferred CPU will be chosen and henceforth task shouldn't come back to + * this CPU again. + * + * Works for FAIR class only. + * + * If task is affined only on non-preferred CPUs, no point in moving it out. + */ +void sched_push_current_non_preferred_cpu(struct rq *rq) +{ + struct task_struct *push_task = rq->curr; + + scoped_guard(rq_lock, rq) { + /* Push the task if its explicit affinity allows */ + if (!task_can_migrate_to_preferred(push_task, rq->cpu)) + return; + + /* There is already a stopper thread. Don't race with it. */ + if (rq->npc_push_work_pending) + return; + + if (is_migration_disabled(push_task)) + return; + + rq->npc_push_work_pending = true; + } + + /* sched_tick runs with interrupts disabled. */ + get_task_struct(push_task); + stop_one_cpu_nowait(rq->cpu, sched_non_preferred_cpu_push_stop, + push_task, this_cpu_ptr(&npc_push_task_work)); +} +#endif diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index d41d23a5632b..7d2ec527b8a2 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1326,6 +1326,9 @@ struct rq { #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING u64 prev_steal_time_rq; #endif +#ifdef CONFIG_PREFERRED_CPU + bool npc_push_work_pending; +#endif /* calc_load related fields */ unsigned long calc_load_update; @@ -4299,4 +4302,10 @@ DEFINE_CLASS_IS_UNCONDITIONAL(sched_change) #include "ext/ext.h" +#ifdef CONFIG_PREFERRED_CPU +void sched_push_current_non_preferred_cpu(struct rq *rq); +#else /* !CONFIG_PREFERRED_CPU */ +static inline void sched_push_current_non_preferred_cpu(struct rq *rq) { } +#endif + #endif /* _KERNEL_SCHED_SCHED_H */