perfcounters: add task migrations counter

Impact: add new feature, new sw counter

Add a counter that counts the number of cross-CPU migrations a
task is suffering.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 2 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 5c3f4106314e..382cfdb5e38d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1852,12 +1852,14 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
                 p->se.sleep_start -= clock_offset;
         if (p->se.block_start)
                 p->se.block_start -= clock_offset;
+#endif
         if (old_cpu != new_cpu) {
-                schedstat_inc(p, se.nr_migrations);
+                p->se.nr_migrations++;
+#ifdef CONFIG_SCHEDSTATS
                 if (task_hot(p, old_rq->clock, NULL))
                         schedstat_inc(p, se.nr_forced2_migrations);
-        }
 #endif
+        }
         p->se.vruntime -= old_cfsrq->min_vruntime -
                                          new_cfsrq->min_vruntime;
 
@@ -2375,6 +2377,7 @@ static void __sched_fork(struct task_struct *p)
         p->se.exec_start                = 0;
         p->se.sum_exec_runtime          = 0;
         p->se.prev_sum_exec_runtime     = 0;
+        p->se.nr_migrations             = 0;
         p->se.last_wakeup               = 0;
         p->se.avg_overlap               = 0;