sched/nohz: Optimize nohz_idle_balance()

Avoid calling update_blocked_averages() when it does not in fact have
any by re-using/extending update_nohz_stats().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index aad7c03dbad80f8e085280b13e9630ba2a8bca90..5c357561db5d396e7a79347e1a12ffe0e1f1237b 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7898,7 +7898,7 @@ group_type group_classify(struct sched_group *group,
        return group_other;
 }
 
-static bool update_nohz_stats(struct rq *rq)
+static bool update_nohz_stats(struct rq *rq, bool force)
 {
 #ifdef CONFIG_NO_HZ_COMMON
        unsigned int cpu = rq->cpu;
@@ -7909,7 +7909,7 @@ static bool update_nohz_stats(struct rq *rq)
        if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
                return false;
 
-       if (!time_after(jiffies, rq->last_blocked_load_update_tick))
+       if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick))
                return true;
 
        update_blocked_averages(cpu);
@@ -7942,7 +7942,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
        for_each_cpu_and(i, sched_group_span(group), env->cpus) {
                struct rq *rq = cpu_rq(i);
 
-               if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq))
+               if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false))
                        env->flags |= LBF_NOHZ_AGAIN;
 
                /* Bias balancing toward CPUs of our domain: */
@@ -9552,8 +9552,7 @@ static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
 
                rq = cpu_rq(balance_cpu);
 
-               update_blocked_averages(rq->cpu);
-               has_blocked_load |= rq->has_blocked_load;
+               has_blocked_load |= update_nohz_stats(rq, true);
 
                /*
                 * If time for next balance is due,