[Devel] [PATCH 2/5] store number of iowait events in a task_group

[Glauber Costa]

Instead of just having the rq to hold them, this patch stores
the nr_iowait figures for each task_group, except for the root
task group. That one is kept using the numbers originating from
the rq.

Signed-off-by: Glauber Costa <glommer at parallels.com>
---
 include/linux/sched.h |    1 +
 kernel/sched/core.c   |   42 ++++++++++++++++++++++++++++++++++++++----
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5b8ff53..b629c1e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1207,6 +1207,7 @@ struct sched_entity {
 
 	u64			nr_migrations;
 
+	atomic_t                nr_iowait;
 #ifdef CONFIG_SCHEDSTATS
 	struct sched_statistics statistics;
 #endif
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 455810f..fe35316 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2665,7 +2665,41 @@ static inline void task_group_account_field(struct task_struct *p, int index,
 #endif
 }
 
+static void task_group_inc_nr_iowait(struct task_struct *p, int cpu)
+{
+	struct task_group *tg;
+	struct rq *rq = cpu_rq(cpu);
+
+	rcu_read_lock();
+	tg = task_group(p);
+
+	atomic_inc(&rq->nr_iowait);
+
+	while (tg && tg != &root_task_group) {
+		atomic_inc(&tg->se[cpu]->nr_iowait);
+		tg = tg->parent;
+	}
+	rcu_read_unlock();
+
+}
+
+static void task_group_dec_nr_iowait(struct task_struct *p, int cpu)
+{
+	struct task_group *tg;
+	struct rq *rq = cpu_rq(cpu);
+
+	rcu_read_lock();
+	tg = task_group(p);
+
+	atomic_dec(&rq->nr_iowait);
+
+	while (tg && tg != &root_task_group) {
+		atomic_dec(&tg->se[cpu]->nr_iowait);
+		tg = tg->parent;
+	}
+	rcu_read_unlock();
 
+}
 /*
  * Account user cpu time to a process.
  * @p: the process that the cpu time gets accounted to
@@ -4677,12 +4711,12 @@ void __sched io_schedule(void)
 	struct rq *rq = raw_rq();
 
 	delayacct_blkio_start();
-	atomic_inc(&rq->nr_iowait);
+	task_group_inc_nr_iowait(current, cpu_of(rq));
 	blk_flush_plug(current);
 	current->in_iowait = 1;
 	schedule();
 	current->in_iowait = 0;
-	atomic_dec(&rq->nr_iowait);
+	task_group_dec_nr_iowait(current, cpu_of(rq));
 	delayacct_blkio_end();
 }
 EXPORT_SYMBOL(io_schedule);
@@ -4693,12 +4727,12 @@ long __sched io_schedule_timeout(long timeout)
 	long ret;
 
 	delayacct_blkio_start();
-	atomic_inc(&rq->nr_iowait);
+	task_group_inc_nr_iowait(current, cpu_of(rq));
 	blk_flush_plug(current);
 	current->in_iowait = 1;
 	ret = schedule_timeout(timeout);
 	current->in_iowait = 0;
-	atomic_dec(&rq->nr_iowait);
+	task_group_dec_nr_iowait(current, cpu_of(rq));
 	delayacct_blkio_end();
 	return ret;
 }
-- 
1.7.7.4