schedstat: consolidate per-task cpu runtime stats

Impact: simplify code

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>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 5 insertions, 4 deletions

diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index b3179dad71be..abb6e17505e2 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -127,7 +127,7 @@ int __delayacct_add_tsk(struct taskstats *d, struct task_struct *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 f53e2b8ef521..fd835fc320b8 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -596,6 +596,8 @@ 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 7dbf72a2b02c..3b01098164c8 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
@@ -236,7 +236,6 @@ static inline void sched_info_depart(struct task_struct *t)
         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)