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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: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peter Zijlstra 2007-07-19 01:49:00 -07:00 committed by Linus Torvalds
parent 443aef0edd
commit 96645678cd
4 changed files with 55 additions and 21 deletions
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17
include/linux/lockdep.h
View File

@ -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 */

38
kernel/lockdep.c
View File

@ -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 @@ found_it:
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;
now = sched_clock();
waittime = now - hlock->waittime_stamp;
hlock->holdtime_stamp = now;
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 (hlock->read)
lock_time_inc(&stats->read_waittime, waittime);
else
lock_time_inc(&stats->write_waittime, waittime);
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)

19
kernel/lockdep_proc.c
View File

@ -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");
}

2
kernel/mutex.c
View File

@ -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));