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Message-ID: <20250205012411.1010817-2-longman@redhat.com>
Date: Tue, 4 Feb 2025 20:24:10 -0500
From: Waiman Long <longman@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Will Deacon <will.deacon@....com>,
Boqun Feng <boqun.feng@...il.com>
Cc: linux-kernel@...r.kernel.org,
Waiman Long <longman@...hat.com>
Subject: [PATCH v2 1/2] locking/lock_events: Add locking events for rtmutex slow paths
Add locking events for rtlock_slowlock() and rt_mutex_slowlock() for
profiling the slow path behavior of rt_spin_lock() and rt_mutex_lock().
Signed-off-by: Waiman Long <longman@...hat.com>
---
kernel/locking/lock_events_list.h | 21 +++++++++++++++++++++
kernel/locking/rtmutex.c | 29 ++++++++++++++++++++++++-----
2 files changed, 45 insertions(+), 5 deletions(-)
diff --git a/kernel/locking/lock_events_list.h b/kernel/locking/lock_events_list.h
index 97fb6f3f840a..80b11f194c9f 100644
--- a/kernel/locking/lock_events_list.h
+++ b/kernel/locking/lock_events_list.h
@@ -67,3 +67,24 @@ LOCK_EVENT(rwsem_rlock_handoff) /* # of read lock handoffs */
LOCK_EVENT(rwsem_wlock) /* # of write locks acquired */
LOCK_EVENT(rwsem_wlock_fail) /* # of failed write lock acquisitions */
LOCK_EVENT(rwsem_wlock_handoff) /* # of write lock handoffs */
+
+/*
+ * Locking events for rtlock_slowlock()
+ */
+LOCK_EVENT(rtlock_slowlock) /* # of rtlock_slowlock() calls */
+LOCK_EVENT(rtlock_slow_acq1) /* # of locks acquired after wait_lock */
+LOCK_EVENT(rtlock_slow_acq2) /* # of locks acquired in for loop */
+LOCK_EVENT(rtlock_slow_sleep) /* # of sleeps */
+LOCK_EVENT(rtlock_slow_wake) /* # of wakeup's */
+
+/*
+ * Locking events for rt_mutex_slowlock()
+ */
+LOCK_EVENT(rtmutex_slowlock) /* # of rt_mutex_slowlock() calls */
+LOCK_EVENT(rtmutex_slow_block) /* # of rt_mutex_slowlock_block() calls */
+LOCK_EVENT(rtmutex_slow_acq1) /* # of locks acquired after wait_lock */
+LOCK_EVENT(rtmutex_slow_acq2) /* # of locks acquired at the end */
+LOCK_EVENT(rtmutex_slow_acq3) /* # of locks acquired in *block() */
+LOCK_EVENT(rtmutex_slow_sleep) /* # of sleeps */
+LOCK_EVENT(rtmutex_slow_wake) /* # of wakeup's */
+LOCK_EVENT(rtmutex_deadlock) /* # of rt_mutex_handle_deadlock()'s */
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 4a8df1800cbb..c80902eacd79 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -27,6 +27,7 @@
#include <trace/events/lock.h>
#include "rtmutex_common.h"
+#include "lock_events.h"
#ifndef WW_RT
# define build_ww_mutex() (false)
@@ -1612,10 +1613,13 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
struct task_struct *owner;
int ret = 0;
+ lockevent_inc(rtmutex_slow_block);
for (;;) {
/* Try to acquire the lock: */
- if (try_to_take_rt_mutex(lock, current, waiter))
+ if (try_to_take_rt_mutex(lock, current, waiter)) {
+ lockevent_inc(rtmutex_slow_acq3);
break;
+ }
if (timeout && !timeout->task) {
ret = -ETIMEDOUT;
@@ -1638,8 +1642,10 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
owner = NULL;
raw_spin_unlock_irq_wake(&lock->wait_lock, wake_q);
- if (!owner || !rtmutex_spin_on_owner(lock, waiter, owner))
+ if (!owner || !rtmutex_spin_on_owner(lock, waiter, owner)) {
+ lockevent_inc(rtmutex_slow_sleep);
rt_mutex_schedule();
+ }
raw_spin_lock_irq(&lock->wait_lock);
set_current_state(state);
@@ -1694,6 +1700,7 @@ static int __sched __rt_mutex_slowlock(struct rt_mutex_base *lock,
int ret;
lockdep_assert_held(&lock->wait_lock);
+ lockevent_inc(rtmutex_slowlock);
/* Try to acquire the lock again: */
if (try_to_take_rt_mutex(lock, current, NULL)) {
@@ -1701,6 +1708,7 @@ static int __sched __rt_mutex_slowlock(struct rt_mutex_base *lock,
__ww_mutex_check_waiters(rtm, ww_ctx, wake_q);
ww_mutex_lock_acquired(ww, ww_ctx);
}
+ lockevent_inc(rtmutex_slow_acq1);
return 0;
}
@@ -1719,10 +1727,12 @@ static int __sched __rt_mutex_slowlock(struct rt_mutex_base *lock,
__ww_mutex_check_waiters(rtm, ww_ctx, wake_q);
ww_mutex_lock_acquired(ww, ww_ctx);
}
+ lockevent_inc(rtmutex_slow_acq2);
} else {
__set_current_state(TASK_RUNNING);
remove_waiter(lock, waiter);
rt_mutex_handle_deadlock(ret, chwalk, lock, waiter);
+ lockevent_inc(rtmutex_deadlock);
}
/*
@@ -1751,6 +1761,7 @@ static inline int __rt_mutex_slowlock_locked(struct rt_mutex_base *lock,
&waiter, wake_q);
debug_rt_mutex_free_waiter(&waiter);
+ lockevent_cond_inc(rtmutex_slow_wake, !wake_q_empty(wake_q));
return ret;
}
@@ -1823,9 +1834,12 @@ static void __sched rtlock_slowlock_locked(struct rt_mutex_base *lock,
struct task_struct *owner;
lockdep_assert_held(&lock->wait_lock);
+ lockevent_inc(rtlock_slowlock);
- if (try_to_take_rt_mutex(lock, current, NULL))
+ if (try_to_take_rt_mutex(lock, current, NULL)) {
+ lockevent_inc(rtlock_slow_acq1);
return;
+ }
rt_mutex_init_rtlock_waiter(&waiter);
@@ -1838,8 +1852,10 @@ static void __sched rtlock_slowlock_locked(struct rt_mutex_base *lock,
for (;;) {
/* Try to acquire the lock again */
- if (try_to_take_rt_mutex(lock, current, &waiter))
+ if (try_to_take_rt_mutex(lock, current, &waiter)) {
+ lockevent_inc(rtlock_slow_acq2);
break;
+ }
if (&waiter == rt_mutex_top_waiter(lock))
owner = rt_mutex_owner(lock);
@@ -1847,8 +1863,10 @@ static void __sched rtlock_slowlock_locked(struct rt_mutex_base *lock,
owner = NULL;
raw_spin_unlock_irq_wake(&lock->wait_lock, wake_q);
- if (!owner || !rtmutex_spin_on_owner(lock, &waiter, owner))
+ if (!owner || !rtmutex_spin_on_owner(lock, &waiter, owner)) {
+ lockevent_inc(rtlock_slow_sleep);
schedule_rtlock();
+ }
raw_spin_lock_irq(&lock->wait_lock);
set_current_state(TASK_RTLOCK_WAIT);
@@ -1865,6 +1883,7 @@ static void __sched rtlock_slowlock_locked(struct rt_mutex_base *lock,
debug_rt_mutex_free_waiter(&waiter);
trace_contention_end(lock, 0);
+ lockevent_cond_inc(rtlock_slow_wake, !wake_q_empty(wake_q));
}
static __always_inline void __sched rtlock_slowlock(struct rt_mutex_base *lock)
--
2.48.1
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