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Commit c46261de authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds
Browse files

lockstat: human readability tweaks 



Present all this fancy new lock statistics information:

*warning, _wide_ output ahead*

(output edited for purpose of brevity)

 # cat /proc/lock_stat
lock_stat version 0.1
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
                              class name    contentions   waittime-min   waittime-max waittime-total   acquisitions   holdtime-min   holdtime-max holdtime-total
-----------------------------------------------------------------------------------------------------------------------------------------------------------------

                         &inode->i_mutex:         14458           6.57      398832.75     2469412.23        6768876           0.34    11398383.65   339410830.89
                         ---------------
                         &inode->i_mutex           4486          [<ffffffff802a08f9>] pipe_wait+0x86/0x8d
                         &inode->i_mutex              0          [<ffffffff802a01e8>] pipe_write_fasync+0x29/0x5d
                         &inode->i_mutex              0          [<ffffffff802a0e18>] pipe_read+0x74/0x3a5
                         &inode->i_mutex              0          [<ffffffff802a1a6a>] do_lookup+0x81/0x1ae

.................................................................................................................................................................

              &inode->i_data.tree_lock-W:           491           0.27          62.47         493.89        2477833           0.39         468.89     1146584.25
              &inode->i_data.tree_lock-R:            65           0.44           4.27          48.78       26288792           0.36         184.62    10197458.24
              --------------------------
                &inode->i_data.tree_lock             46          [<ffffffff80277095>] __do_page_cache_readahead+0x69/0x24f
                &inode->i_data.tree_lock             31          [<ffffffff8026f9fb>] add_to_page_cache+0x31/0xba
                &inode->i_data.tree_lock              0          [<ffffffff802770ee>] __do_page_cache_readahead+0xc2/0x24f
                &inode->i_data.tree_lock              0          [<ffffffff8026f6e4>] find_get_page+0x1a/0x58

.................................................................................................................................................................

                      proc_inum_idr.lock:             0           0.00           0.00           0.00             36           0.00          65.60         148.26
                        proc_subdir_lock:             0           0.00           0.00           0.00        3049859           0.00         106.81     1563212.42
                        shrinker_rwsem-W:             0           0.00           0.00           0.00              5           0.00           1.73           3.68
                        shrinker_rwsem-R:             0           0.00           0.00           0.00            633           2.57         246.57       10909.76

'contentions' and 'acquisitions' are the number of such events measured (since
the last reset). The waittime- and holdtime- (min, max, total) numbers are
presented in microseconds.

If there are any contention points, the lock class is presented in the block
format (as i_mutex and tree_lock above), otherwise a single line of output is
presented.

The output is sorted on absolute number of contentions (read + write), this
should get the worst offenders presented first, so that:

 # grep : /proc/lock_stat | head

will quickly show who's bad.

The stats can be reset using:

 # echo 0 > /proc/lock_stat

[bunk@stusta.de: make 2 functions static]
[akpm@linux-foundation.org: fix printk warning]
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Acked-by: default avatarJason Baron <jbaron@redhat.com>
Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f20786ff

kernel/lockdep.c

+44 −0
Original line number Diff line number Diff line
@@ -149,6 +149,50 @@ static void lock_time_inc(struct lock_time *lt, s64 time) 
	lt->nr++;

}



static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)

{

	dst->min += src->min;

	dst->max += src->max;

	dst->total += src->total;

	dst->nr += src->nr;

}



struct lock_class_stats lock_stats(struct lock_class *class)

{

	struct lock_class_stats stats;

	int cpu, i;



	memset(&stats, 0, sizeof(struct lock_class_stats));

	for_each_possible_cpu(cpu) {

		struct lock_class_stats *pcs =

			&per_cpu(lock_stats, cpu)[class - lock_classes];



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

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



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

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



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

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

	}



	return stats;

}



void clear_lock_stats(struct lock_class *class)

{

	int cpu;



	for_each_possible_cpu(cpu) {

		struct lock_class_stats *cpu_stats =

			&per_cpu(lock_stats, cpu)[class - lock_classes];



		memset(cpu_stats, 0, sizeof(struct lock_class_stats));

	}

	memset(class->contention_point, 0, sizeof(class->contention_point));

}



static struct lock_class_stats *get_lock_stats(struct lock_class *class)

{

	return &get_cpu_var(lock_stats)[class - lock_classes];

kernel/lockdep_proc.c

+266 −0
Original line number Diff line number Diff line
@@ -15,6 +15,10 @@ 
#include <linux/seq_file.h>

#include <linux/kallsyms.h>

#include <linux/debug_locks.h>

#include <linux/vmalloc.h>

#include <linux/sort.h>

#include <asm/uaccess.h>

#include <asm/div64.h>



#include "lockdep_internals.h"
@@ -344,6 +348,262 @@ static const struct file_operations proc_lockdep_stats_operations = { 
	.release	= seq_release,

};



#ifdef CONFIG_LOCK_STAT



struct lock_stat_data {

	struct lock_class *class;

	struct lock_class_stats stats;

};



struct lock_stat_seq {

	struct lock_stat_data *iter;

	struct lock_stat_data *iter_end;

	struct lock_stat_data stats[MAX_LOCKDEP_KEYS];

};



/*

 * sort on absolute number of contentions

 */

static int lock_stat_cmp(const void *l, const void *r)

{

	const struct lock_stat_data *dl = l, *dr = r;

	unsigned long nl, nr;



	nl = dl->stats.read_waittime.nr + dl->stats.write_waittime.nr;

	nr = dr->stats.read_waittime.nr + dr->stats.write_waittime.nr;



	return nr - nl;

}



static void seq_line(struct seq_file *m, char c, int offset, int length)

{

	int i;



	for (i = 0; i < offset; i++)

		seq_puts(m, " ");

	for (i = 0; i < length; i++)

		seq_printf(m, "%c", c);

	seq_puts(m, "\n");

}



static void snprint_time(char *buf, size_t bufsiz, s64 nr)

{

	unsigned long rem;



	rem = do_div(nr, 1000); /* XXX: do_div_signed */

	snprintf(buf, bufsiz, "%lld.%02d", (long long)nr, ((int)rem+5)/10);

}



static void seq_time(struct seq_file *m, s64 time)

{

	char num[15];



	snprint_time(num, sizeof(num), time);

	seq_printf(m, " %14s", num);

}



static void seq_lock_time(struct seq_file *m, struct lock_time *lt)

{

	seq_printf(m, "%14lu", lt->nr);

	seq_time(m, lt->min);

	seq_time(m, lt->max);

	seq_time(m, lt->total);

}



static void seq_stats(struct seq_file *m, struct lock_stat_data *data)

{

	char name[39];

	struct lock_class *class;

	struct lock_class_stats *stats;

	int i, namelen;



	class = data->class;

	stats = &data->stats;



	snprintf(name, 38, "%s", class->name);

	namelen = strlen(name);



	if (stats->write_holdtime.nr) {

		if (stats->read_holdtime.nr)

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

		else

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



		seq_lock_time(m, &stats->write_waittime);

		seq_puts(m, " ");

		seq_lock_time(m, &stats->write_holdtime);

		seq_puts(m, "\n");

	}



	if (stats->read_holdtime.nr) {

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

		seq_lock_time(m, &stats->read_waittime);

		seq_puts(m, " ");

		seq_lock_time(m, &stats->read_holdtime);

		seq_puts(m, "\n");

	}



	if (stats->read_waittime.nr + stats->write_waittime.nr == 0)

		return;



	if (stats->read_holdtime.nr)

		namelen += 2;



	for (i = 0; i < ARRAY_SIZE(class->contention_point); i++) {

		char sym[KSYM_SYMBOL_LEN];

		char ip[32];



		if (class->contention_point[i] == 0)

			break;



		if (!i)

			seq_line(m, '-', 40-namelen, namelen);



		sprint_symbol(sym, class->contention_point[i]);

		snprintf(ip, sizeof(ip), "[<%p>]",

				(void *)class->contention_point[i]);

		seq_printf(m, "%40s %14lu %29s %s\n", name,

				stats->contention_point[i],

				ip, sym);

	}

	if (i) {

		seq_puts(m, "\n");

		seq_line(m, '.', 0, 40 + 1 + 8 * (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",

			"class name",

			"contentions",

			"waittime-min",

			"waittime-max",

			"waittime-total",

			"acquisitions",

			"holdtime-min",

			"holdtime-max",

			"holdtime-total");

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

	seq_printf(m, "\n");

}



static void *ls_start(struct seq_file *m, loff_t *pos)

{

	struct lock_stat_seq *data = m->private;



	if (data->iter == data->stats)

		seq_header(m);



	return data->iter;

}



static void *ls_next(struct seq_file *m, void *v, loff_t *pos)

{

	struct lock_stat_seq *data = m->private;



	(*pos)++;



	data->iter = v;

	data->iter++;

	if (data->iter == data->iter_end)

		data->iter = NULL;



	return data->iter;

}



static void ls_stop(struct seq_file *m, void *v)

{

}



static int ls_show(struct seq_file *m, void *v)

{

	struct lock_stat_seq *data = m->private;



	seq_stats(m, data->iter);

	return 0;

}



static struct seq_operations lockstat_ops = {

	.start	= ls_start,

	.next	= ls_next,

	.stop	= ls_stop,

	.show	= ls_show,

};



static int lock_stat_open(struct inode *inode, struct file *file)

{

	int res;

	struct lock_class *class;

	struct lock_stat_seq *data = vmalloc(sizeof(struct lock_stat_seq));



	if (!data)

		return -ENOMEM;



	res = seq_open(file, &lockstat_ops);

	if (!res) {

		struct lock_stat_data *iter = data->stats;

		struct seq_file *m = file->private_data;



		data->iter = iter;

		list_for_each_entry(class, &all_lock_classes, lock_entry) {

			iter->class = class;

			iter->stats = lock_stats(class);

			iter++;

		}

		data->iter_end = iter;



		sort(data->stats, data->iter_end - data->iter,

				sizeof(struct lock_stat_data),

				lock_stat_cmp, NULL);



		m->private = data;

	} else

		vfree(data);



	return res;

}



static ssize_t lock_stat_write(struct file *file, const char __user *buf,

			       size_t count, loff_t *ppos)

{

	struct lock_class *class;

	char c;



	if (count) {

		if (get_user(c, buf))

			return -EFAULT;



		if (c != '0')

			return count;



		list_for_each_entry(class, &all_lock_classes, lock_entry)

			clear_lock_stats(class);

	}

	return count;

}



static int lock_stat_release(struct inode *inode, struct file *file)

{

	struct seq_file *seq = file->private_data;



	vfree(seq->private);

	seq->private = NULL;

	return seq_release(inode, file);

}



static const struct file_operations proc_lock_stat_operations = {

	.open		= lock_stat_open,

	.write		= lock_stat_write,

	.read		= seq_read,

	.llseek		= seq_lseek,

	.release	= lock_stat_release,

};

#endif /* CONFIG_LOCK_STAT */



static int __init lockdep_proc_init(void)

{

	struct proc_dir_entry *entry;
@@ -356,6 +616,12 @@ static int __init lockdep_proc_init(void) 
	if (entry)

		entry->proc_fops = &proc_lockdep_stats_operations;



#ifdef CONFIG_LOCK_STAT

	entry = create_proc_entry("lock_stat", S_IRUSR, NULL);

	if (entry)

		entry->proc_fops = &proc_lock_stat_operations;

#endif



	return 0;

}