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>

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) */
 

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
 }
 
 /*

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;