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[PATCH] lockdep: core, reduce per-lock class-cache size 

lockdep_map is embedded into every lock, which blows up data structure
sizes all around the kernel.  Reduce the class-cache to be for the default
class only - that is used in 99.9% of the cases and even if we dont have a
class cached, the lookup in the class-hash is lockless.

This change reduces the per-lock dep_map overhead by 56 bytes on 64-bit
platforms and by 28 bytes on 32-bit platforms.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Ingo Molnar 2006-07-10 04:44:04 -07:00 committed by Linus Torvalds
parent 55794a412f
commit d6d897cec2
2 changed files with 55 additions and 34 deletions
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2
include/linux/lockdep.h
View File

@ -120,7 +120,7 @@ struct lock_class {
*/
struct lockdep_map {
struct lock_class_key *key;
struct lock_class *class[MAX_LOCKDEP_SUBCLASSES];
struct lock_class *class_cache;
const char *name;
};

87
kernel/lockdep.c
View File

@ -1104,7 +1104,7 @@ extern void __error_too_big_MAX_LOCKDEP_SUBCLASSES(void);
* itself, so actual lookup of the hash should be once per lock object.
*/
static inline struct lock_class *
register_lock_class(struct lockdep_map *lock, unsigned int subclass)
look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
{
struct lockdep_subclass_key *key;
struct list_head *hash_head;
@ -1148,7 +1148,26 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass)
*/
list_for_each_entry(class, hash_head, hash_entry)
if (class->key == key)
goto out_set;
return class;
return NULL;
}
/*
* Register a lock's class in the hash-table, if the class is not present
* yet. Otherwise we look it up. We cache the result in the lock object
* itself, so actual lookup of the hash should be once per lock object.
*/
static inline struct lock_class *
register_lock_class(struct lockdep_map *lock, unsigned int subclass)
{
struct lockdep_subclass_key *key;
struct list_head *hash_head;
struct lock_class *class;
class = look_up_lock_class(lock, subclass);
if (likely(class))
return class;
/*
* Debug-check: all keys must be persistent!
@ -1163,6 +1182,9 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass)
return NULL;
}
key = lock->key->subkeys + subclass;
hash_head = classhashentry(key);
__raw_spin_lock(&hash_lock);
/*
* We have to do the hash-walk again, to avoid races
@ -1209,8 +1231,8 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass)
out_unlock_set:
__raw_spin_unlock(&hash_lock);
out_set:
lock->class[subclass] = class;
if (!subclass)
lock->class_cache = class;
DEBUG_LOCKS_WARN_ON(class->subclass != subclass);
@ -1914,7 +1936,7 @@ void lockdep_init_map(struct lockdep_map *lock, const char *name,
}
lock->name = name;
lock->key = key;
memset(lock->class, 0, sizeof(lock->class[0])*MAX_LOCKDEP_SUBCLASSES);
lock->class_cache = NULL;
}
EXPORT_SYMBOL_GPL(lockdep_init_map);
@ -1928,8 +1950,8 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
unsigned long ip)
{
struct task_struct *curr = current;
struct lock_class *class = NULL;
struct held_lock *hlock;
struct lock_class *class;
unsigned int depth, id;
int chain_head = 0;
u64 chain_key;
@ -1947,8 +1969,11 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
return 0;
}
class = lock->class[subclass];
/* not cached yet? */
if (!subclass)
class = lock->class_cache;
/*
* Not cached yet or subclass?
*/
if (unlikely(!class)) {
class = register_lock_class(lock, subclass);
if (!class)
@ -2449,48 +2474,44 @@ void lockdep_free_key_range(void *start, unsigned long size)
void lockdep_reset_lock(struct lockdep_map *lock)
{
struct lock_class *class, *next, *entry;
struct lock_class *class, *next;
struct list_head *head;
unsigned long flags;
int i, j;
raw_local_irq_save(flags);
__raw_spin_lock(&hash_lock);
/*
* Remove all classes this lock has:
* Remove all classes this lock might have:
*/
for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
/*
* If the class exists we look it up and zap it:
*/
class = look_up_lock_class(lock, j);
if (class)
zap_class(class);
}
/*
* Debug check: in the end all mapped classes should
* be gone.
*/
__raw_spin_lock(&hash_lock);
for (i = 0; i < CLASSHASH_SIZE; i++) {
head = classhash_table + i;
if (list_empty(head))
continue;
list_for_each_entry_safe(class, next, head, hash_entry) {
for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
entry = lock->class[j];
if (class == entry) {
zap_class(class);
lock->class[j] = NULL;
break;
}
if (unlikely(class == lock->class_cache)) {
__raw_spin_unlock(&hash_lock);
DEBUG_LOCKS_WARN_ON(1);
goto out_restore;
}
}
}
/*
* Debug check: in the end all mapped classes should
* be gone.
*/
for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
entry = lock->class[j];
if (!entry)
continue;
__raw_spin_unlock(&hash_lock);
DEBUG_LOCKS_WARN_ON(1);
raw_local_irq_restore(flags);
return;
}
__raw_spin_unlock(&hash_lock);
out_restore:
raw_local_irq_restore(flags);
}