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sched/fair: Add NOHZ stats balancing 

Teach the idle balancer about the need to update statistics which have
a different periodicity from regular balancing.

Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
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>
This commit is contained in:
Peter Zijlstra 2017-12-21 10:42:50 +01:00 committed by Ingo Molnar
parent 4550487a99
commit a4064fb614
1 changed files with 19 additions and 12 deletions
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31
kernel/sched/fair.c
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@ -9053,6 +9053,7 @@ static struct {
cpumask_var_t idle_cpus_mask;
atomic_t nr_cpus;
unsigned long next_balance; /* in jiffy units */
unsigned long next_stats;
} nohz ____cacheline_aligned;
static inline int find_new_ilb(void)
@ -9087,9 +9088,8 @@ unlock:
* nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
* CPU (if there is one).
*/
static void kick_ilb(void)
static void kick_ilb(unsigned int flags)
{
unsigned int flags;
int ilb_cpu;
nohz.next_balance++;
@ -9099,7 +9099,7 @@ static void kick_ilb(void)
if (ilb_cpu >= nr_cpu_ids)
return;
flags = atomic_fetch_or(NOHZ_KICK_MASK, nohz_flags(ilb_cpu));
flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
if (flags & NOHZ_KICK_MASK)
return;
@ -9129,7 +9129,7 @@ static void nohz_balancer_kick(struct rq *rq)
struct sched_domain_shared *sds;
struct sched_domain *sd;
int nr_busy, i, cpu = rq->cpu;
bool kick = false;
unsigned int flags = 0;
if (unlikely(rq->idle_balance))
return;
@ -9148,11 +9148,14 @@ static void nohz_balancer_kick(struct rq *rq)
if (likely(!atomic_read(&nohz.nr_cpus)))
return;
if (time_after(now, nohz.next_stats))
flags = NOHZ_STATS_KICK;
if (time_before(now, nohz.next_balance))
return;
goto out;
if (rq->nr_running >= 2) {
kick = true;
flags = NOHZ_KICK_MASK;
goto out;
}
@ -9165,7 +9168,7 @@ static void nohz_balancer_kick(struct rq *rq)
*/
nr_busy = atomic_read(&sds->nr_busy_cpus);
if (nr_busy > 1) {
kick = true;
flags = NOHZ_KICK_MASK;
goto unlock;
}
@ -9175,7 +9178,7 @@ static void nohz_balancer_kick(struct rq *rq)
if (sd) {
if ((rq->cfs.h_nr_running >= 1) &&
check_cpu_capacity(rq, sd)) {
kick = true;
flags = NOHZ_KICK_MASK;
goto unlock;
}
}
@ -9188,7 +9191,7 @@ static void nohz_balancer_kick(struct rq *rq)
continue;
if (sched_asym_prefer(i, cpu)) {
kick = true;
flags = NOHZ_KICK_MASK;
goto unlock;
}
}
@ -9196,8 +9199,8 @@ static void nohz_balancer_kick(struct rq *rq)
unlock:
rcu_read_unlock();
out:
if (kick)
kick_ilb();
if (flags)
kick_ilb(flags);
}
void nohz_balance_exit_idle(unsigned int cpu)
@ -9389,7 +9392,9 @@ out:
static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
{
/* Earliest time when we have to do rebalance again */
unsigned long next_balance = jiffies + 60*HZ;
unsigned long now = jiffies;
unsigned long next_balance = now + 60*HZ;
unsigned long next_stats = now + msecs_to_jiffies(LOAD_AVG_PERIOD);
int update_next_balance = 0;
int this_cpu = this_rq->cpu;
unsigned int flags;
@ -9449,6 +9454,8 @@ static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
if (flags & NOHZ_BALANCE_KICK)
rebalance_domains(this_rq, CPU_IDLE);
nohz.next_stats = next_stats;
/*
* next_balance will be updated only when there is a need.
* When the CPU is attached to null domain for ex, it will not be