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Subject[tip:sched/core] sched: Implement hierarchical task accounting for SCHED_OTHER
Commit-ID:  953bfcd10e6f3697233e8e5128c611d275da39c1
Gitweb: http://git.kernel.org/tip/953bfcd10e6f3697233e8e5128c611d275da39c1
Author: Paul Turner <pjt@google.com>
AuthorDate: Thu, 21 Jul 2011 09:43:27 -0700
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Sun, 14 Aug 2011 12:01:13 +0200

sched: Implement hierarchical task accounting for SCHED_OTHER

Introduce hierarchical task accounting for the group scheduling case in CFS, as
well as promoting the responsibility for maintaining rq->nr_running to the
scheduling classes.

The primary motivation for this is that with scheduling classes supporting
bandwidth throttling it is possible for entities participating in throttled
sub-trees to not have root visible changes in rq->nr_running across activate
and de-activate operations. This in turn leads to incorrect idle and
weight-per-task load balance decisions.

This also allows us to make a small fixlet to the fastpath in pick_next_task()
under group scheduling.

Note: this issue also exists with the existing sched_rt throttling mechanism.
This patch does not address that.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184756.878333391@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/sched.c | 6 ++----
kernel/sched_fair.c | 6 ++++++
kernel/sched_rt.c | 5 ++++-
kernel/sched_stoptask.c | 2 ++
4 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index cf427bb..cd1a531 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -311,7 +311,7 @@ struct task_group root_task_group;
/* CFS-related fields in a runqueue */
struct cfs_rq {
struct load_weight load;
- unsigned long nr_running;
+ unsigned long nr_running, h_nr_running;

u64 exec_clock;
u64 min_vruntime;
@@ -1802,7 +1802,6 @@ static void activate_task(struct rq *rq, struct task_struct *p, int flags)
rq->nr_uninterruptible--;

enqueue_task(rq, p, flags);
- inc_nr_running(rq);
}

/*
@@ -1814,7 +1813,6 @@ static void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
rq->nr_uninterruptible++;

dequeue_task(rq, p, flags);
- dec_nr_running(rq);
}

#ifdef CONFIG_IRQ_TIME_ACCOUNTING
@@ -4258,7 +4256,7 @@ pick_next_task(struct rq *rq)
* Optimization: we know that if all tasks are in
* the fair class we can call that function directly:
*/
- if (likely(rq->nr_running == rq->cfs.nr_running)) {
+ if (likely(rq->nr_running == rq->cfs.h_nr_running)) {
p = fair_sched_class.pick_next_task(rq);
if (likely(p))
return p;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index f4b732a..f86b0cb 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1310,16 +1310,19 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
break;
cfs_rq = cfs_rq_of(se);
enqueue_entity(cfs_rq, se, flags);
+ cfs_rq->h_nr_running++;
flags = ENQUEUE_WAKEUP;
}

for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
+ cfs_rq->h_nr_running++;

update_cfs_load(cfs_rq, 0);
update_cfs_shares(cfs_rq);
}

+ inc_nr_running(rq);
hrtick_update(rq);
}

@@ -1339,6 +1342,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
dequeue_entity(cfs_rq, se, flags);
+ cfs_rq->h_nr_running--;

/* Don't dequeue parent if it has other entities besides us */
if (cfs_rq->load.weight) {
@@ -1358,11 +1362,13 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)

for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
+ cfs_rq->h_nr_running--;

update_cfs_load(cfs_rq, 0);
update_cfs_shares(cfs_rq);
}

+ dec_nr_running(rq);
hrtick_update(rq);
}

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index a8c207f..a9d3c6b 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -936,6 +936,8 @@ enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)

if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
enqueue_pushable_task(rq, p);
+
+ inc_nr_running(rq);
}

static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
@@ -946,6 +948,8 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
dequeue_rt_entity(rt_se);

dequeue_pushable_task(rq, p);
+
+ dec_nr_running(rq);
}

/*
@@ -1841,4 +1845,3 @@ static void print_rt_stats(struct seq_file *m, int cpu)
rcu_read_unlock();
}
#endif /* CONFIG_SCHED_DEBUG */
-
diff --git a/kernel/sched_stoptask.c b/kernel/sched_stoptask.c
index 6f43763..8b44e7f 100644
--- a/kernel/sched_stoptask.c
+++ b/kernel/sched_stoptask.c
@@ -34,11 +34,13 @@ static struct task_struct *pick_next_task_stop(struct rq *rq)
static void
enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
{
+ inc_nr_running(rq);
}

static void
dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
{
+ dec_nr_running(rq);
}

static void yield_task_stop(struct rq *rq)

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