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sched: Refactor update_shares_cpu() -> update_blocked_avgs() 

Now that running entities maintain their own load-averages the work we must do
in update_shares() is largely restricted to the periodic decay of blocked
entities.  This allows us to be a little less pessimistic regarding our
occupancy on rq->lock and the associated rq->clock updates required.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141507.133999170@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Paul Turner 2012-10-04 13:18:31 +02:00 committed by Ingo Molnar
parent 82958366cf
commit 48a1675323
1 changed files with 23 additions and 27 deletions
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50
kernel/sched/fair.c
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@ -3639,20 +3639,15 @@ next:
/* /*
* update tg->load_weight by folding this cpu's load_avg * update tg->load_weight by folding this cpu's load_avg
*/ */
static int update_shares_cpu(struct task_group *tg, int cpu) static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
{ {
struct sched_entity *se; struct sched_entity *se = tg->se[cpu];
struct cfs_rq *cfs_rq; struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
unsigned long flags;
struct rq *rq;
rq = cpu_rq(cpu); /* throttled entities do not contribute to load */
se = tg->se[cpu]; if (throttled_hierarchy(cfs_rq))
cfs_rq = tg->cfs_rq[cpu]; return;
raw_spin_lock_irqsave(&rq->lock, flags);
update_rq_clock(rq);
update_cfs_rq_blocked_load(cfs_rq, 1); update_cfs_rq_blocked_load(cfs_rq, 1);
if (se) { if (se) {
@ -3669,32 +3664,33 @@ static int update_shares_cpu(struct task_group *tg, int cpu)
if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running) if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running)
list_del_leaf_cfs_rq(cfs_rq); list_del_leaf_cfs_rq(cfs_rq);
} else { } else {
struct rq *rq = rq_of(cfs_rq);
update_rq_runnable_avg(rq, rq->nr_running); update_rq_runnable_avg(rq, rq->nr_running);
} }
raw_spin_unlock_irqrestore(&rq->lock, flags);
return 0;
} }
static void update_shares(int cpu) static void update_blocked_averages(int cpu)
{ {
struct cfs_rq *cfs_rq;
struct rq *rq = cpu_rq(cpu); struct rq *rq = cpu_rq(cpu);
struct cfs_rq *cfs_rq;
unsigned long flags;
rcu_read_lock(); raw_spin_lock_irqsave(&rq->lock, flags);
update_rq_clock(rq);
/* /*
* Iterates the task_group tree in a bottom up fashion, see * Iterates the task_group tree in a bottom up fashion, see
* list_add_leaf_cfs_rq() for details. * list_add_leaf_cfs_rq() for details.
*/ */
for_each_leaf_cfs_rq(rq, cfs_rq) { for_each_leaf_cfs_rq(rq, cfs_rq) {
/* throttled entities do not contribute to load */ /*
if (throttled_hierarchy(cfs_rq)) * Note: We may want to consider periodically releasing
continue; * rq->lock about these updates so that creating many task
* groups does not result in continually extending hold time.
update_shares_cpu(cfs_rq->tg, cpu); */
__update_blocked_averages_cpu(cfs_rq->tg, rq->cpu);
} }
rcu_read_unlock();
raw_spin_unlock_irqrestore(&rq->lock, flags);
} }
/* /*
@ -3746,7 +3742,7 @@ static unsigned long task_h_load(struct task_struct *p)
return load; return load;
} }
#else #else
static inline void update_shares(int cpu) static inline void update_blocked_averages(int cpu)
{ {
} }
@ -4813,7 +4809,7 @@ void idle_balance(int this_cpu, struct rq *this_rq)
*/ */
raw_spin_unlock(&this_rq->lock); raw_spin_unlock(&this_rq->lock);
update_shares(this_cpu); update_blocked_averages(this_cpu);
rcu_read_lock(); rcu_read_lock();
for_each_domain(this_cpu, sd) { for_each_domain(this_cpu, sd) {
unsigned long interval; unsigned long interval;
@ -5068,7 +5064,7 @@ static void rebalance_domains(int cpu, enum cpu_idle_type idle)
int update_next_balance = 0; int update_next_balance = 0;
int need_serialize; int need_serialize;
update_shares(cpu); update_blocked_averages(cpu);
rcu_read_lock(); rcu_read_lock();
for_each_domain(cpu, sd) { for_each_domain(cpu, sd) {