sched debug: BKL usage statistics

add per task and per rq BKL usage statistics.

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

3 files changed, 17 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index d0cc58311b13..920eb7354d0a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -621,6 +621,10 @@ struct sched_info {
         /* timestamps */
         unsigned long long last_arrival,/* when we last ran on a cpu */
                            last_queued; /* when we were last queued to run */
+#ifdef CONFIG_SCHEDSTATS
+        /* BKL stats */
+        unsigned long bkl_cnt;
+#endif
 };
 #endif /* defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT) */
 
diff --git a/kernel/sched.c b/kernel/sched.c
index f33608e9e1a2..5004dff91850 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -356,6 +356,9 @@ struct rq {
         /* try_to_wake_up() stats */
         unsigned long ttwu_cnt;
         unsigned long ttwu_local;
+
+        /* BKL stats */
+        unsigned long bkl_cnt;
 #endif
         struct lock_class_key rq_lock_key;
 };
@@ -3414,6 +3417,12 @@ static inline void schedule_debug(struct task_struct *prev)
         profile_hit(SCHED_PROFILING, __builtin_return_address(0));
 
         schedstat_inc(this_rq(), sched_cnt);
+#ifdef CONFIG_SCHEDSTATS
+        if (unlikely(prev->lock_depth >= 0)) {
+                schedstat_inc(this_rq(), bkl_cnt);
+                schedstat_inc(prev, sched_info.bkl_cnt);
+        }
+#endif
 }
 
 /*
diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c
index 57ee9d5630a8..823b63a3a3e1 100644
--- a/kernel/sched_debug.c
+++ b/kernel/sched_debug.c
@@ -136,6 +136,8 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
                         SPLIT_NS(spread0));
         SEQ_printf(m, "  .%-30s: %ld\n", "nr_running", cfs_rq->nr_running);
         SEQ_printf(m, "  .%-30s: %ld\n", "load", cfs_rq->load.weight);
+        SEQ_printf(m, "  .%-30s: %ld\n", "bkl_cnt",
+                        rq->bkl_cnt);
 }
 
 static void print_cpu(struct seq_file *m, int cpu)
@@ -323,6 +325,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
         PN(se.exec_max);
         PN(se.slice_max);
         PN(se.wait_max);
+        P(sched_info.bkl_cnt);
 #endif
         SEQ_printf(m, "%-25s:%20Ld\n",
                    "nr_switches", (long long)(p->nvcsw + p->nivcsw));
@@ -350,6 +353,7 @@ void proc_sched_set_task(struct task_struct *p)
         p->se.exec_max                  = 0;
         p->se.slice_max                 = 0;
         p->se.wait_max                  = 0;
+        p->sched_info.bkl_cnt           = 0;
 #endif
         p->se.sum_exec_runtime          = 0;
         p->se.prev_sum_exec_runtime     = 0;