sched: debug: track maximum 'slice'

track the maximum amount of time a task has executed while
the CPU load was at least 2x. (i.e. at least two nice-0
tasks were runnable)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

4 files changed, 15 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 833f7dc2b8de..9761b165d563 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -921,6 +921,7 @@ struct sched_entity {
         u64                     block_start;
         u64                     block_max;
         u64                     exec_max;
+        u64                     slice_max;
 
         unsigned long           wait_runtime_overruns;
         unsigned long           wait_runtime_underruns;
diff --git a/kernel/sched.c b/kernel/sched.c
index e92b185e371b..282d037c7300 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1603,6 +1603,7 @@ static void __sched_fork(struct task_struct *p)
         p->se.sleep_max                 = 0;
         p->se.block_max                 = 0;
         p->se.exec_max                  = 0;
+        p->se.slice_max                 = 0;
         p->se.wait_max                  = 0;
         p->se.wait_runtime_overruns     = 0;
         p->se.wait_runtime_underruns    = 0;
diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c
index 94915f1fd9de..fd080f686f18 100644
--- a/kernel/sched_debug.c
+++ b/kernel/sched_debug.c
@@ -254,6 +254,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
         P(se.sleep_max);
         P(se.block_max);
         P(se.exec_max);
+        P(se.slice_max);
         P(se.wait_max);
         P(se.wait_runtime_overruns);
         P(se.wait_runtime_underruns);
@@ -282,6 +283,7 @@ void proc_sched_set_task(struct task_struct *p)
         p->se.sleep_max                 = 0;
         p->se.block_max                 = 0;
         p->se.exec_max                  = 0;
+        p->se.slice_max                 = 0;
         p->se.wait_max                  = 0;
         p->se.wait_runtime_overruns     = 0;
         p->se.wait_runtime_underruns    = 0;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 0990b20fdcf5..5c15d8ae92cb 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -739,6 +739,17 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
         update_stats_wait_end(cfs_rq, se);
         update_stats_curr_start(cfs_rq, se);
         set_cfs_rq_curr(cfs_rq, se);
+#ifdef CONFIG_SCHEDSTATS
+        /*
+         * Track our maximum slice length, if the CPU's load is at
+         * least twice that of our own weight (i.e. dont track it
+         * when there are only lesser-weight tasks around):
+         */
+        if (rq_of(cfs_rq)->ls.load.weight >= 2*se->load.weight) {
+                se->slice_max = max(se->slice_max,
+                        se->sum_exec_runtime - se->prev_sum_exec_runtime);
+        }
+#endif
         se->prev_sum_exec_runtime = se->sum_exec_runtime;
 }