[tip:sched/core] sched: Implement on-demand (active) cfs_rq list
From: tip-bot for Peter Zijlstra
Date: Thu Nov 18 2010 - 09:11:18 EST
Commit-ID: 3d4b47b4b040c9d77dd68104cfc1055d89a55afd
Gitweb: http://git.kernel.org/tip/3d4b47b4b040c9d77dd68104cfc1055d89a55afd
Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
AuthorDate: Mon, 15 Nov 2010 15:47:01 -0800
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Thu, 18 Nov 2010 13:27:47 +0100
sched: Implement on-demand (active) cfs_rq list
Make certain load-balance actions scale per number of active cgroups
instead of the number of existing cgroups.
This makes wakeup/sleep paths more expensive, but is a win for systems
where the vast majority of existing cgroups are idle.
Signed-off-by: Paul Turner <pjt@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
LKML-Reference: <20101115234937.666535048@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/sched.c | 105 +++++++++++++-------------------------------------
kernel/sched_fair.c | 46 +++++++++++++++++++---
kernel/sched_rt.c | 24 ++++++++++++
3 files changed, 92 insertions(+), 83 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index e2f1a30..22436dd 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -274,9 +274,7 @@ struct task_group {
#define root_task_group init_task_group
-/* task_group_lock serializes add/remove of task groups and also changes to
- * a task group's cpu shares.
- */
+/* task_group_lock serializes the addition/removal of task groups */
static DEFINE_SPINLOCK(task_group_lock);
#ifdef CONFIG_FAIR_GROUP_SCHED
@@ -344,6 +342,7 @@ struct cfs_rq {
* leaf_cfs_rq_list ties together list of leaf cfs_rq's in a cpu. This
* list is used during load balance.
*/
+ int on_list;
struct list_head leaf_cfs_rq_list;
struct task_group *tg; /* group that "owns" this runqueue */
@@ -1547,7 +1546,7 @@ static unsigned long cpu_avg_load_per_task(int cpu)
#ifdef CONFIG_FAIR_GROUP_SCHED
-static void update_cfs_load(struct cfs_rq *cfs_rq);
+static void update_cfs_load(struct cfs_rq *cfs_rq, int lb);
static void update_cfs_shares(struct cfs_rq *cfs_rq);
/*
@@ -1570,7 +1569,7 @@ static int tg_shares_up(struct task_group *tg, void *data)
raw_spin_lock_irqsave(&rq->lock, flags);
update_rq_clock(rq);
- update_cfs_load(cfs_rq);
+ update_cfs_load(cfs_rq, 1);
load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1);
load_avg -= cfs_rq->load_contribution;
@@ -7688,15 +7687,13 @@ static void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq)
#ifdef CONFIG_FAIR_GROUP_SCHED
static void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
- struct sched_entity *se, int cpu, int add,
+ struct sched_entity *se, int cpu,
struct sched_entity *parent)
{
struct rq *rq = cpu_rq(cpu);
tg->cfs_rq[cpu] = cfs_rq;
init_cfs_rq(cfs_rq, rq);
cfs_rq->tg = tg;
- if (add)
- list_add(&cfs_rq->leaf_cfs_rq_list, &rq->leaf_cfs_rq_list);
tg->se[cpu] = se;
/* se could be NULL for init_task_group */
@@ -7716,7 +7713,7 @@ static void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
#ifdef CONFIG_RT_GROUP_SCHED
static void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
- struct sched_rt_entity *rt_se, int cpu, int add,
+ struct sched_rt_entity *rt_se, int cpu,
struct sched_rt_entity *parent)
{
struct rq *rq = cpu_rq(cpu);
@@ -7725,8 +7722,6 @@ static void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
init_rt_rq(rt_rq, rq);
rt_rq->tg = tg;
rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
- if (add)
- list_add(&rt_rq->leaf_rt_rq_list, &rq->leaf_rt_rq_list);
tg->rt_se[cpu] = rt_se;
if (!rt_se)
@@ -7835,7 +7830,7 @@ void __init sched_init(void)
* We achieve this by letting init_task_group's tasks sit
* directly in rq->cfs (i.e init_task_group->se[] = NULL).
*/
- init_tg_cfs_entry(&init_task_group, &rq->cfs, NULL, i, 1, NULL);
+ init_tg_cfs_entry(&init_task_group, &rq->cfs, NULL, i, NULL);
#endif
#endif /* CONFIG_FAIR_GROUP_SCHED */
@@ -7843,7 +7838,7 @@ void __init sched_init(void)
#ifdef CONFIG_RT_GROUP_SCHED
INIT_LIST_HEAD(&rq->leaf_rt_rq_list);
#ifdef CONFIG_CGROUP_SCHED
- init_tg_rt_entry(&init_task_group, &rq->rt, NULL, i, 1, NULL);
+ init_tg_rt_entry(&init_task_group, &rq->rt, NULL, i, NULL);
#endif
#endif
@@ -8119,7 +8114,7 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
if (!se)
goto err_free_rq;
- init_tg_cfs_entry(tg, cfs_rq, se, i, 0, parent->se[i]);
+ init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
}
return 1;
@@ -8130,15 +8125,22 @@ err:
return 0;
}
-static inline void register_fair_sched_group(struct task_group *tg, int cpu)
-{
- list_add_rcu(&tg->cfs_rq[cpu]->leaf_cfs_rq_list,
- &cpu_rq(cpu)->leaf_cfs_rq_list);
-}
-
static inline void unregister_fair_sched_group(struct task_group *tg, int cpu)
{
- list_del_rcu(&tg->cfs_rq[cpu]->leaf_cfs_rq_list);
+ struct rq *rq = cpu_rq(cpu);
+ unsigned long flags;
+ int i;
+
+ /*
+ * Only empty task groups can be destroyed; so we can speculatively
+ * check on_list without danger of it being re-added.
+ */
+ if (!tg->cfs_rq[cpu]->on_list)
+ return;
+
+ raw_spin_lock_irqsave(&rq->lock, flags);
+ list_del_leaf_cfs_rq(tg->cfs_rq[i]);
+ raw_spin_unlock_irqrestore(&rq->lock, flags);
}
#else /* !CONFG_FAIR_GROUP_SCHED */
static inline void free_fair_sched_group(struct task_group *tg)
@@ -8151,10 +8153,6 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
return 1;
}
-static inline void register_fair_sched_group(struct task_group *tg, int cpu)
-{
-}
-
static inline void unregister_fair_sched_group(struct task_group *tg, int cpu)
{
}
@@ -8209,7 +8207,7 @@ int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
if (!rt_se)
goto err_free_rq;
- init_tg_rt_entry(tg, rt_rq, rt_se, i, 0, parent->rt_se[i]);
+ init_tg_rt_entry(tg, rt_rq, rt_se, i, parent->rt_se[i]);
}
return 1;
@@ -8219,17 +8217,6 @@ err_free_rq:
err:
return 0;
}
-
-static inline void register_rt_sched_group(struct task_group *tg, int cpu)
-{
- list_add_rcu(&tg->rt_rq[cpu]->leaf_rt_rq_list,
- &cpu_rq(cpu)->leaf_rt_rq_list);
-}
-
-static inline void unregister_rt_sched_group(struct task_group *tg, int cpu)
-{
- list_del_rcu(&tg->rt_rq[cpu]->leaf_rt_rq_list);
-}
#else /* !CONFIG_RT_GROUP_SCHED */
static inline void free_rt_sched_group(struct task_group *tg)
{
@@ -8240,14 +8227,6 @@ int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
{
return 1;
}
-
-static inline void register_rt_sched_group(struct task_group *tg, int cpu)
-{
-}
-
-static inline void unregister_rt_sched_group(struct task_group *tg, int cpu)
-{
-}
#endif /* CONFIG_RT_GROUP_SCHED */
#ifdef CONFIG_CGROUP_SCHED
@@ -8263,7 +8242,6 @@ struct task_group *sched_create_group(struct task_group *parent)
{
struct task_group *tg;
unsigned long flags;
- int i;
tg = kzalloc(sizeof(*tg), GFP_KERNEL);
if (!tg)
@@ -8276,10 +8254,6 @@ struct task_group *sched_create_group(struct task_group *parent)
goto err;
spin_lock_irqsave(&task_group_lock, flags);
- for_each_possible_cpu(i) {
- register_fair_sched_group(tg, i);
- register_rt_sched_group(tg, i);
- }
list_add_rcu(&tg->list, &task_groups);
WARN_ON(!parent); /* root should already exist */
@@ -8309,11 +8283,11 @@ void sched_destroy_group(struct task_group *tg)
unsigned long flags;
int i;
- spin_lock_irqsave(&task_group_lock, flags);
- for_each_possible_cpu(i) {
+ /* end participation in shares distribution */
+ for_each_possible_cpu(i)
unregister_fair_sched_group(tg, i);
- unregister_rt_sched_group(tg, i);
- }
+
+ spin_lock_irqsave(&task_group_lock, flags);
list_del_rcu(&tg->list);
list_del_rcu(&tg->siblings);
spin_unlock_irqrestore(&task_group_lock, flags);
@@ -8391,7 +8365,6 @@ static DEFINE_MUTEX(shares_mutex);
int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
int i;
- unsigned long flags;
/*
* We can't change the weight of the root cgroup.
@@ -8408,19 +8381,6 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
if (tg->shares == shares)
goto done;
- spin_lock_irqsave(&task_group_lock, flags);
- for_each_possible_cpu(i)
- unregister_fair_sched_group(tg, i);
- list_del_rcu(&tg->siblings);
- spin_unlock_irqrestore(&task_group_lock, flags);
-
- /* wait for any ongoing reference to this group to finish */
- synchronize_sched();
-
- /*
- * Now we are free to modify the group's share on each cpu
- * w/o tripping rebalance_share or load_balance_fair.
- */
tg->shares = shares;
for_each_possible_cpu(i) {
/*
@@ -8429,15 +8389,6 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
set_se_shares(tg->se[i], shares);
}
- /*
- * Enable load balance activity on this group, by inserting it back on
- * each cpu's rq->leaf_cfs_rq_list.
- */
- spin_lock_irqsave(&task_group_lock, flags);
- for_each_possible_cpu(i)
- register_fair_sched_group(tg, i);
- list_add_rcu(&tg->siblings, &tg->parent->children);
- spin_unlock_irqrestore(&task_group_lock, flags);
done:
mutex_unlock(&shares_mutex);
return 0;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index d86544b..0560e72 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -143,6 +143,24 @@ static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
return cfs_rq->tg->cfs_rq[this_cpu];
}
+static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
+{
+ if (!cfs_rq->on_list) {
+ list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
+ &rq_of(cfs_rq)->leaf_cfs_rq_list);
+
+ cfs_rq->on_list = 1;
+ }
+}
+
+static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
+{
+ if (cfs_rq->on_list) {
+ list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
+ cfs_rq->on_list = 0;
+ }
+}
+
/* Iterate thr' all leaf cfs_rq's on a runqueue */
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
@@ -246,6 +264,14 @@ static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
return &cpu_rq(this_cpu)->cfs;
}
+static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
+{
+}
+
+static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
+{
+}
+
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
@@ -648,7 +674,7 @@ account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
}
#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
-static void update_cfs_load(struct cfs_rq *cfs_rq)
+static void update_cfs_load(struct cfs_rq *cfs_rq, int lb)
{
u64 period = sched_avg_period();
u64 now, delta;
@@ -673,6 +699,11 @@ static void update_cfs_load(struct cfs_rq *cfs_rq)
cfs_rq->load_period /= 2;
cfs_rq->load_avg /= 2;
}
+
+ if (lb && !cfs_rq->nr_running) {
+ if (cfs_rq->load_avg < (period / 8))
+ list_del_leaf_cfs_rq(cfs_rq);
+ }
}
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
@@ -719,7 +750,7 @@ static void update_cfs_shares(struct cfs_rq *cfs_rq)
reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
-static inline void update_cfs_load(struct cfs_rq *cfs_rq)
+static inline void update_cfs_load(struct cfs_rq *cfs_rq, int lb)
{
}
@@ -849,7 +880,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
* Update run-time statistics of the 'current'.
*/
update_curr(cfs_rq);
- update_cfs_load(cfs_rq);
+ update_cfs_load(cfs_rq, 0);
account_entity_enqueue(cfs_rq, se);
update_cfs_shares(cfs_rq);
@@ -863,6 +894,9 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
if (se != cfs_rq->curr)
__enqueue_entity(cfs_rq, se);
se->on_rq = 1;
+
+ if (cfs_rq->nr_running == 1)
+ list_add_leaf_cfs_rq(cfs_rq);
}
static void __clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
@@ -907,7 +941,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
if (se != cfs_rq->curr)
__dequeue_entity(cfs_rq, se);
se->on_rq = 0;
- update_cfs_load(cfs_rq);
+ update_cfs_load(cfs_rq, 0);
account_entity_dequeue(cfs_rq, se);
update_min_vruntime(cfs_rq);
update_cfs_shares(cfs_rq);
@@ -1142,7 +1176,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
for_each_sched_entity(se) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
- update_cfs_load(cfs_rq);
+ update_cfs_load(cfs_rq, 0);
update_cfs_shares(cfs_rq);
}
@@ -1172,7 +1206,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
for_each_sched_entity(se) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
- update_cfs_load(cfs_rq);
+ update_cfs_load(cfs_rq, 0);
update_cfs_shares(cfs_rq);
}
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index bea7d79..c914ec7 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -183,6 +183,17 @@ static inline u64 sched_rt_period(struct rt_rq *rt_rq)
return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
}
+static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
+{
+ list_add_rcu(&rt_rq->leaf_rt_rq_list,
+ &rq_of_rt_rq(rt_rq)->leaf_rt_rq_list);
+}
+
+static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
+{
+ list_del_rcu(&rt_rq->leaf_rt_rq_list);
+}
+
#define for_each_leaf_rt_rq(rt_rq, rq) \
list_for_each_entry_rcu(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
@@ -276,6 +287,14 @@ static inline u64 sched_rt_period(struct rt_rq *rt_rq)
return ktime_to_ns(def_rt_bandwidth.rt_period);
}
+static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
+{
+}
+
+static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
+{
+}
+
#define for_each_leaf_rt_rq(rt_rq, rq) \
for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
@@ -825,6 +844,9 @@ static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
return;
+ if (!rt_rq->rt_nr_running)
+ list_add_leaf_rt_rq(rt_rq);
+
if (head)
list_add(&rt_se->run_list, queue);
else
@@ -844,6 +866,8 @@ static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
__clear_bit(rt_se_prio(rt_se), array->bitmap);
dec_rt_tasks(rt_se, rt_rq);
+ if (!rt_rq->rt_nr_running)
+ list_del_leaf_rt_rq(rt_rq);
}
/*
--
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