Instead of waking up a random and already idle CPU, we can take advantage of this_cpu being about to enter idle to run the ILB and update the blocked load.
Signed-off-by: Vincent Guittot <[email protected]> --- include/linux/sched/nohz.h | 2 ++ kernel/sched/fair.c | 11 ++++++++--- kernel/sched/idle.c | 6 ++++++ 3 files changed, 16 insertions(+), 3 deletions(-) diff --git a/include/linux/sched/nohz.h b/include/linux/sched/nohz.h index 6d67e9a5af6b..74cdc4e87310 100644 --- a/include/linux/sched/nohz.h +++ b/include/linux/sched/nohz.h @@ -9,8 +9,10 @@ #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON) extern void nohz_balance_enter_idle(int cpu); extern int get_nohz_timer_target(void); +extern void nohz_run_idle_balance(int cpu); #else static inline void nohz_balance_enter_idle(int cpu) { } +static inline void nohz_run_idle_balance(int cpu) { } #endif #ifdef CONFIG_NO_HZ_COMMON diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 935594cd5430..3d2ab28d5736 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10461,6 +10461,11 @@ static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) return true; } +void nohz_run_idle_balance(int cpu) +{ + nohz_idle_balance(cpu_rq(cpu), CPU_IDLE); +} + static void nohz_newidle_balance(struct rq *this_rq) { int this_cpu = this_rq->cpu; @@ -10482,10 +10487,10 @@ static void nohz_newidle_balance(struct rq *this_rq) return; /* - * Blocked load of idle CPUs need to be updated. - * Kick an ILB to update statistics. + * Set the need to trigger ILB in order to update blocked load + * before entering idle state. */ - kick_ilb(NOHZ_STATS_KICK); + this_rq->nohz_idle_balance = NOHZ_STATS_KICK; } #else /* !CONFIG_NO_HZ_COMMON */ diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 305727ea0677..52a4e9ce2f9b 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -261,6 +261,12 @@ static void cpuidle_idle_call(void) static void do_idle(void) { int cpu = smp_processor_id(); + + /* + * Check if we need to update some blocked load + */ + nohz_run_idle_balance(cpu); + /* * If the arch has a polling bit, we maintain an invariant: * -- 2.17.1
