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Date: Mon, 21 May 2007 16:58:45 -0400 (EDT)
From: Jason Baron <jbaron@...hat.com>
To: Peter Zijlstra <a.p.zijlstra@...llo.nl>
cc: linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
Bill Huey <billh@...ppy.monkey.org>,
Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] lockdep: lock contention tracking
On Sun, 20 May 2007, Peter Zijlstra wrote:
>
> Add lock contention tracking to lockdep
>
looks really nice to me.
To me, in addition to the number of times the lock is contended we also
need the total number of times the lock was acquired, to make the
statistics significant. I've included one such patch below, which also
introduces a 'event', thiking of things like lock timings that were
mentioned, but this is not necessary.
thanks,
-Jason
Signed-off-by: Jason Baron <jbaron@...hat.com>
--- linux-2.6.22-rc2-lockdep/include/linux/lockdep.h.bak 2007-05-21 15:55:30.000000000 -0400
+++ linux-2.6.22-rc2-lockdep/include/linux/lockdep.h 2007-05-21 16:30:13.000000000 -0400
@@ -36,6 +36,17 @@
};
/*
+ * lock contention types
+ */
+
+enum lock_contention_event
+{
+ LOCK_CONTENTION_WRITE = 0,
+ LOCK_CONTENTION_READ,
+ LOCK_CONTENTION_TOTAL
+};
+
+/*
* Usage-state bitmasks:
*/
#define LOCKF_USED (1 << LOCK_USED)
@@ -121,6 +132,7 @@
const char *name;
int name_version;
+ atomic_t total;
atomic_t read_contentions;
atomic_t write_contentions;
struct lockdep_contention_point contention_point[4];
@@ -253,7 +265,7 @@
extern void lock_release(struct lockdep_map *lock, int nested,
unsigned long ip);
-extern void lock_contended(struct lockdep_map *lock, int read,
+extern void lock_contended(struct lockdep_map *lock, enum lock_contention_event,
unsigned long ip);
# define INIT_LOCKDEP .lockdep_recursion = 0,
--- linux-2.6.22-rc2-lockdep/kernel/lockdep_proc.c.bak 2007-05-21 16:10:12.000000000 -0400
+++ linux-2.6.22-rc2-lockdep/kernel/lockdep_proc.c 2007-05-21 16:11:38.000000000 -0400
@@ -348,16 +348,17 @@
struct lock_class *class;
list_for_each_entry(class, &all_lock_classes, lock_entry) {
- int r, w;
+ int r, w, t;
r = atomic_read(&class->read_contentions);
w = atomic_read(&class->write_contentions);
+ t = atomic_read(&class->total);
if (r || w) {
int i;
char sym[KSYM_SYMBOL_LEN];
- seq_printf(m, "%s: %d %d", class->name, w, r);
+ seq_printf(m, "%s: %d %d %d", class->name, w, r, t);
for (i = 0; i < ARRAY_SIZE(class->contention_point);
i++) {
struct lockdep_contention_point *cp =
--- linux-2.6.22-rc2-lockdep/kernel/lockdep.c.bak 2007-05-21 16:02:05.000000000 -0400
+++ linux-2.6.22-rc2-lockdep/kernel/lockdep.c 2007-05-21 16:29:35.000000000 -0400
@@ -2429,7 +2429,7 @@
}
static void
-__lock_contended(struct lockdep_map *lock, int read, unsigned long ip)
+__lock_contended(struct lockdep_map *lock, enum lock_contention_event event, unsigned long ip)
{
struct task_struct *curr = current;
struct held_lock *hlock, *prev_hlock;
@@ -2463,10 +2463,17 @@
return;
found_it:
- if (read)
+ switch (event) {
+ case LOCK_CONTENTION_READ:
atomic_inc(&class->read_contentions);
- else
+ break;
+ case LOCK_CONTENTION_WRITE:
atomic_inc(&class->write_contentions);
+ break;
+ case LOCK_CONTENTION_TOTAL:
+ atomic_inc(&class->total);
+ return;
+ }
for (i = 0; i < ARRAY_SIZE(class->contention_point); i++) {
if (class->contention_point[i].ip == 0) {
@@ -2530,6 +2537,7 @@
current->lockdep_recursion = 1;
__lock_acquire(lock, subclass, trylock, read, check,
irqs_disabled_flags(flags), ip);
+ __lock_contended(lock, LOCK_CONTENTION_TOTAL, 0);
current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
}
@@ -2553,7 +2561,7 @@
EXPORT_SYMBOL_GPL(lock_release);
-void lock_contended(struct lockdep_map *lock, int read, unsigned long ip)
+void lock_contended(struct lockdep_map *lock, enum lock_contention_event event, unsigned long ip)
{
unsigned long flags;
@@ -2563,7 +2571,7 @@
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion = 1;
- __lock_contended(lock, read, ip);
+ __lock_contended(lock, event, ip);
current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
}
-
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