[patch] schedstat: consolidate per-task cpu runtime stats

[Ken Chen <kenchen@google.com>]

When we turn on CONFIG_SCHEDSTATS, per-task cpu runtime is accumulated
twice. Once in task->se.sum_exec_runtime and once in sched_info.cpu_time.
These two stats are exactly the same.

Given that task->se.sum_exec_runtime is always accumulated by the core
scheduler, sched_info can reuse that data instead of duplicate the accounting.

Signed-off-by: Ken Chen <kenchen@google.com>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index d467760..4d745ba 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -347,7 +347,7 @@
 static int proc_pid_schedstat(struct task_struct *task, char *buffer)
 {
 	return sprintf(buffer, "%llu %llu %lu\n",
-			task->sched_info.cpu_time,
+			task->se.sum_exec_runtime,
 			task->sched_info.run_delay,
 			task->sched_info.pcount);
 }
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 55e30d1..a0fa340 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -672,8 +672,7 @@ struct reclaim_state;
 struct sched_info {
 	/* cumulative counters */
 	unsigned long pcount;	      /* # of times run on this cpu */
-	unsigned long long cpu_time,  /* time spent on the cpu */
-			   run_delay; /* time spent waiting on a runqueue */
+	unsigned long long run_delay; /* time spent waiting on a runqueue */

 	/* timestamps */
 	unsigned long long last_arrival,/* when we last ran on a cpu */
diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index b3179da..abb6e17 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -127,7 +127,7 @@ int __delayacct_add_tsk
 	 */
 	t1 = tsk->sched_info.pcount;
 	t2 = tsk->sched_info.run_delay;
-	t3 = tsk->sched_info.cpu_time;
+	t3 = tsk->se.sum_exec_runtime;

 	d->cpu_count += t1;

diff --git a/kernel/sched.c b/kernel/sched.c
index 4d1920d..1ed1809 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -586,6 +586,8 @@ struct rq {
 #ifdef CONFIG_SCHEDSTATS
 	/* latency stats */
 	struct sched_info rq_sched_info;
+	unsigned long long rq_cpu_time;
+	/* could above be rq->cfs_rq.exec_clock + rq->rt_rq.rt_runtime ? */

 	/* sys_sched_yield() stats */
 	unsigned int yld_exp_empty;
diff --git a/kernel/sched_stats.h b/kernel/sched_stats.h
index 4272594..b07eee8 100644
--- a/kernel/sched_stats.h
+++ b/kernel/sched_stats.h
@@ -31,7 +31,7 @@ static int show_schedstat(struct seq_file *seq, void *v)
 		    rq->yld_act_empty, rq->yld_exp_empty, rq->yld_count,
 		    rq->sched_switch, rq->sched_count, rq->sched_goidle,
 		    rq->ttwu_count, rq->ttwu_local,
-		    rq->rq_sched_info.cpu_time,
+		    rq->rq_cpu_time,
 		    rq->rq_sched_info.run_delay, rq->rq_sched_info.pcount);

 		seq_printf(seq, "\n");
@@ -123,7 +123,7 @@ static inline void
 rq_sched_info_depart(struct rq *rq, unsigned long long delta)
 {
 	if (rq)
-		rq->rq_sched_info.cpu_time += delta;
+		rq->rq_cpu_time += delta;
 }

 static inline void
@@ -238,7 +238,6 @@ static inline void sched_info_depart
 	unsigned long long delta = task_rq(t)->clock -
 					t->sched_info.last_arrival;

-	t->sched_info.cpu_time += delta;
 	rq_sched_info_depart(task_rq(t), delta);

 	if (t->state == TASK_RUNNING)