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Commit 96645678 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds
Browse files

lockstat: measure lock bouncing 



    __acquire
        |
       lock _____
        |        \
        |    __contended
        |         |
        |        wait
        | _______/
        |/
        |
   __acquired
        |
   __release
        |
     unlock

We measure acquisition and contention bouncing.

This is done by recording a cpu stamp in each lock instance.

Contention bouncing requires the cpu stamp to be set on acquisition. Hence we
move __acquired into the generic path.

__acquired is then used to measure acquisition bouncing by comparing the
current cpu with the old stamp before replacing it.

__contended is used to measure contention bouncing (only useful for preemptable
locks)

[akpm@linux-foundation.org: cleanups]
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 443aef0e

include/linux/lockdep.h

+16 −1
Original line number Diff line number Diff line
@@ -130,12 +130,24 @@ struct lock_time { 
	unsigned long			nr;

};



enum bounce_type {

	bounce_acquired_write,

	bounce_acquired_read,

	bounce_contended_write,

	bounce_contended_read,

	nr_bounce_types,



	bounce_acquired = bounce_acquired_write,

	bounce_contended = bounce_contended_write,

};



struct lock_class_stats {

	unsigned long			contention_point[4];

	struct lock_time		read_waittime;

	struct lock_time		write_waittime;

	struct lock_time		read_holdtime;

	struct lock_time		write_holdtime;

	unsigned long			bounces[nr_bounce_types];

};



struct lock_class_stats lock_stats(struct lock_class *class);
@@ -150,6 +162,9 @@ struct lockdep_map { 
	struct lock_class_key		*key;

	struct lock_class		*class_cache;

	const char			*name;

#ifdef CONFIG_LOCK_STAT

	int				cpu;

#endif

};



/*
@@ -321,8 +336,8 @@ do { \ 
	if (!try(_lock)) {					\

		lock_contended(&(_lock)->dep_map, _RET_IP_);	\

		lock(_lock);					\

		lock_acquired(&(_lock)->dep_map);		\

	}							\

	lock_acquired(&(_lock)->dep_map);			\

} while (0)



#else /* CONFIG_LOCK_STAT */

kernel/lockdep.c

+26 −12
Original line number Diff line number Diff line
@@ -177,6 +177,9 @@ struct lock_class_stats lock_stats(struct lock_class *class) 


		lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);

		lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);



		for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)

			stats.bounces[i] += pcs->bounces[i];

	}



	return stats;
@@ -2325,6 +2328,9 @@ void lockdep_init_map(struct lockdep_map *lock, const char *name, 
	lock->name = name;

	lock->key = key;

	lock->class_cache = NULL;

#ifdef CONFIG_LOCK_STAT

	lock->cpu = raw_smp_processor_id();

#endif

	if (subclass)

		register_lock_class(lock, subclass, 1);

}
@@ -2775,6 +2781,8 @@ __lock_contended(struct lockdep_map *lock, unsigned long ip) 
	stats = get_lock_stats(hlock->class);

	if (point < ARRAY_SIZE(stats->contention_point))

		stats->contention_point[i]++;

	if (lock->cpu != smp_processor_id())

		stats->bounces[bounce_contended + !!hlock->read]++;

	put_lock_stats(stats);

}
@@ -2786,8 +2794,8 @@ __lock_acquired(struct lockdep_map *lock) 
	struct lock_class_stats *stats;

	unsigned int depth;

	u64 now;

	s64 waittime;

	int i;

	s64 waittime = 0;

	int i, cpu;



	depth = curr->lockdep_depth;

	if (DEBUG_LOCKS_WARN_ON(!depth))
@@ -2809,19 +2817,25 @@ __lock_acquired(struct lockdep_map *lock) 
	return;



found_it:

	if (!hlock->waittime_stamp)

		return;



	cpu = smp_processor_id();

	if (hlock->waittime_stamp) {

		now = sched_clock();

		waittime = now - hlock->waittime_stamp;

		hlock->holdtime_stamp = now;

	}



	stats = get_lock_stats(hlock->class);

	if (waittime) {

		if (hlock->read)

			lock_time_inc(&stats->read_waittime, waittime);

		else

			lock_time_inc(&stats->write_waittime, waittime);

	}

	if (lock->cpu != cpu)

		stats->bounces[bounce_acquired + !!hlock->read]++;

	put_lock_stats(stats);



	lock->cpu = cpu;

}



void lock_contended(struct lockdep_map *lock, unsigned long ip)

kernel/lockdep_proc.c

+12 −7
Original line number Diff line number Diff line
@@ -430,16 +430,18 @@ static void seq_stats(struct seq_file *m, struct lock_stat_data *data) 
		else

			seq_printf(m, "%40s:", name);



		seq_printf(m, "%14lu ", stats->bounces[bounce_contended_write]);

		seq_lock_time(m, &stats->write_waittime);

		seq_puts(m, " ");

		seq_printf(m, " %14lu ", stats->bounces[bounce_acquired_write]);

		seq_lock_time(m, &stats->write_holdtime);

		seq_puts(m, "\n");

	}



	if (stats->read_holdtime.nr) {

		seq_printf(m, "%38s-R:", name);

		seq_printf(m, "%14lu ", stats->bounces[bounce_contended_read]);

		seq_lock_time(m, &stats->read_waittime);

		seq_puts(m, " ");

		seq_printf(m, " %14lu ", stats->bounces[bounce_acquired_read]);

		seq_lock_time(m, &stats->read_holdtime);

		seq_puts(m, "\n");

	}
@@ -469,26 +471,29 @@ static void seq_stats(struct seq_file *m, struct lock_stat_data *data) 
	}

	if (i) {

		seq_puts(m, "\n");

		seq_line(m, '.', 0, 40 + 1 + 8 * (14 + 1));

		seq_line(m, '.', 0, 40 + 1 + 10 * (14 + 1));

		seq_puts(m, "\n");

	}

}



static void seq_header(struct seq_file *m)

{

	seq_printf(m, "lock_stat version 0.1\n");

	seq_line(m, '-', 0, 40 + 1 + 8 * (14 + 1));

	seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s\n",

	seq_printf(m, "lock_stat version 0.2\n");

	seq_line(m, '-', 0, 40 + 1 + 10 * (14 + 1));

	seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s "

			"%14s %14s\n",

			"class name",

			"con-bounces",

			"contentions",

			"waittime-min",

			"waittime-max",

			"waittime-total",

			"acq-bounces",

			"acquisitions",

			"holdtime-min",

			"holdtime-max",

			"holdtime-total");

	seq_line(m, '-', 0, 40 + 1 + 8 * (14 + 1));

	seq_line(m, '-', 0, 40 + 1 + 10 * (14 + 1));

	seq_printf(m, "\n");

}

kernel/mutex.c

+1 −1
Original line number Diff line number Diff line
@@ -180,8 +180,8 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass) 
		spin_lock_mutex(&lock->wait_lock, flags);

	}



	lock_acquired(&lock->dep_map);

done:

	lock_acquired(&lock->dep_map);

	/* got the lock - rejoice! */

	mutex_remove_waiter(lock, &waiter, task_thread_info(task));

	debug_mutex_set_owner(lock, task_thread_info(task));