Track lock hold times - that is the time we held the lock.
/proc/lock_holdtime - starts with the same three colums as lock_contentions:
<class name> <(write) contentions> <read contentions>
After that come two times four more columns:
<nr> <min> <max> <total>
for both (write) locks and read locks. Times are in 1e-9 seconds.
Writing a 0 to the file clears the stats.
Signed-off-by: Peter Zijlstra <[email protected]>
---
include/linux/lockdep.h | 3 ++
kernel/lockdep.c | 32 ++++++++++++++++++++++++--
kernel/lockdep_proc.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 91 insertions(+), 2 deletions(-)
Index: linux-2.6/include/linux/lockdep.h
===================================================================
--- linux-2.6.orig/include/linux/lockdep.h 2007-05-22 23:46:53.000000000 +0200
+++ linux-2.6/include/linux/lockdep.h 2007-05-22 23:47:16.000000000 +0200
@@ -134,6 +134,8 @@ struct lock_class {
struct lock_contention_point contention_point[4];
struct lock_time read_waittime;
struct lock_time write_waittime;
+ struct lock_time read_holdtime;
+ struct lock_time write_holdtime;
#endif
};
@@ -188,6 +190,7 @@ struct held_lock {
#ifdef CONFIG_LOCK_STAT
unsigned long long waittime_stamp;
+ unsigned long long holdtime_stamp;
#endif
/*
* The lock-stack is unified in that the lock chains of interrupt
Index: linux-2.6/kernel/lockdep.c
===================================================================
--- linux-2.6.orig/kernel/lockdep.c 2007-05-22 23:47:06.000000000 +0200
+++ linux-2.6/kernel/lockdep.c 2007-05-22 23:47:23.000000000 +0200
@@ -1283,6 +1283,8 @@ register_lock_class(struct lockdep_map *
#ifdef CONFIG_LOCK_STAT
class->read_waittime.lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
class->write_waittime.lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
+ class->read_holdtime.lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
+ class->write_holdtime.lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
#endif
class->name_version = count_matching_names(class);
/*
@@ -2087,6 +2089,7 @@ static int __lock_acquire(struct lockdep
hlock->hardirqs_off = hardirqs_off;
#ifdef CONFIG_LOCK_STAT
hlock->waittime_stamp = 0;
+ hlock->holdtime_stamp = sched_clock();
#endif
if (check != 2)
@@ -2327,6 +2330,7 @@ static int check_unlock(struct task_stru
return 1;
}
+#ifdef CONFIG_LOCK_STAT
static void lock_time_add(struct lock_time *lt, unsigned long long wt)
{
__raw_spin_lock(<->lock);
@@ -2341,6 +2345,23 @@ static void lock_time_add(struct lock_ti
__raw_spin_unlock(<->lock);
}
+static void lock_release_holdtime(struct held_lock *hlock)
+{
+ unsigned long long holdtime;
+
+ holdtime = sched_clock() - hlock->holdtime_stamp;
+
+ if (hlock->read)
+ lock_time_add(&hlock->class->read_holdtime, holdtime);
+ else
+ lock_time_add(&hlock->class->write_holdtime, holdtime);
+}
+#else
+static void lock_release_holdtime(struct held_lock *hlock)
+{
+}
+#endif
+
/*
* Remove the lock to the list of currently held locks in a
* potentially non-nested (out of order) manner. This is a
@@ -2378,6 +2399,8 @@ lock_release_non_nested(struct task_stru
return print_unlock_inbalance_bug(curr, lock, ip);
found_it:
+ lock_release_holdtime(hlock);
+
/*
* We have the right lock to unlock, 'hlock' points to it.
* Now we remove it from the stack, and add back the other
@@ -2430,6 +2453,8 @@ static int lock_release_nested(struct ta
curr->curr_chain_key = hlock->prev_chain_key;
+ lock_release_holdtime(hlock);
+
#ifdef CONFIG_DEBUG_LOCKDEP
hlock->prev_chain_key = 0;
hlock->class = NULL;
@@ -2519,7 +2544,7 @@ __lock_acquired(struct lockdep_map *lock
struct task_struct *curr = current;
struct held_lock *hlock, *prev_hlock;
unsigned int depth;
- unsigned long long waittime;
+ unsigned long long now, waittime;
int i;
depth = curr->lockdep_depth;
@@ -2545,7 +2570,10 @@ found_it:
if (!hlock->waittime_stamp)
return;
- waittime = sched_clock() - hlock->waittime_stamp;
+ now = sched_clock();
+ waittime = now - hlock->waittime_stamp;
+
+ hlock->holdtime_stamp = now;
if (hlock->read)
lock_time_add(&hlock->class->read_waittime, waittime);
Index: linux-2.6/kernel/lockdep_proc.c
===================================================================
--- linux-2.6.orig/kernel/lockdep_proc.c 2007-05-22 23:46:53.000000000 +0200
+++ linux-2.6/kernel/lockdep_proc.c 2007-05-22 23:47:16.000000000 +0200
@@ -493,6 +493,60 @@ static const struct file_operations proc
.llseek = seq_lseek,
.release = seq_release,
};
+
+static int lock_holdtime_show(struct seq_file *m, void *v)
+{
+ struct lock_class *class;
+ int r, w;
+
+ list_for_each_entry(class, &all_lock_classes, lock_entry) {
+ r = atomic_read(&class->read_contentions);
+ w = atomic_read(&class->write_contentions);
+
+ if (r || w) {
+ seq_printf(m, "%s: %d %d", class->name, w, r);
+ print_time(m, &class->write_holdtime);
+ print_time(m, &class->read_holdtime);
+ seq_printf(m, "\n");
+ }
+ }
+
+ return 0;
+}
+
+static int lock_holdtime_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, lock_holdtime_show, NULL);
+}
+
+ssize_t lock_holdtime_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_time(&class->read_holdtime);
+ clear_time(&class->write_holdtime);
+ }
+ }
+ return count;
+}
+
+static const struct file_operations proc_lock_holdtime_operations = {
+ .open = lock_holdtime_open,
+ .write = lock_holdtime_write,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
#endif /* CONFIG_LOCK_STAT */
static int __init lockdep_proc_init(void)
@@ -515,6 +569,10 @@ static int __init lockdep_proc_init(void
entry = create_proc_entry("lock_waittime", S_IRUSR, NULL);
if (entry)
entry->proc_fops = &proc_lock_waittime_operations;
+
+ entry = create_proc_entry("lock_holdtime", S_IRUSR, NULL);
+ if (entry)
+ entry->proc_fops = &proc_lock_holdtime_operations;
#endif
return 0;
--
-
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