This patch adds several markers around semaphore primitives.
Along with a tracing application this patch can be useful for measuring
kernel semaphore usage and contention.
Signed-off-by: Mike Mason <[email protected]>
Signed-off-by: David Wilder <[email protected]>
---
lib/semaphore-sleepers.c | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)
diff --git a/lib/semaphore-sleepers.c b/lib/semaphore-sleepers.c
index 1281805..5343a96 100644
--- a/lib/semaphore-sleepers.c
+++ b/lib/semaphore-sleepers.c
@@ -15,6 +15,7 @@
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/init.h>
+#include <linux/marker.h>
#include <asm/semaphore.h>
/*
@@ -50,6 +51,7 @@
fastcall void __up(struct semaphore *sem)
{
+ trace_mark(sem_up, "%p", sem);
wake_up(&sem->wait);
}
@@ -59,6 +61,7 @@ fastcall void __sched __down(struct semaphore * sem)
DECLARE_WAITQUEUE(wait, tsk);
unsigned long flags;
+ trace_mark(sem_down, "%p", sem);
tsk->state = TASK_UNINTERRUPTIBLE;
spin_lock_irqsave(&sem->wait.lock, flags);
add_wait_queue_exclusive_locked(&sem->wait, &wait);
@@ -73,12 +76,14 @@ fastcall void __sched __down(struct semaphore * sem)
* the wait_queue_head.
*/
if (!atomic_add_negative(sleepers - 1, &sem->count)) {
+ trace_mark(sem_down_resume, "%p", sem);
sem->sleepers = 0;
break;
}
sem->sleepers = 1; /* us - see -1 above */
spin_unlock_irqrestore(&sem->wait.lock, flags);
+ trace_mark(sem_down_sched, "%p", sem);
schedule();
spin_lock_irqsave(&sem->wait.lock, flags);
@@ -97,6 +102,7 @@ fastcall int __sched __down_interruptible(struct semaphore * sem)
DECLARE_WAITQUEUE(wait, tsk);
unsigned long flags;
+ trace_mark(sem_down_intr, "%p", sem);
tsk->state = TASK_INTERRUPTIBLE;
spin_lock_irqsave(&sem->wait.lock, flags);
add_wait_queue_exclusive_locked(&sem->wait, &wait);
@@ -113,6 +119,7 @@ fastcall int __sched __down_interruptible(struct semaphore * sem)
* and exit.
*/
if (signal_pending(current)) {
+ trace_mark(sem_down_intr_fail, "%p", sem);
retval = -EINTR;
sem->sleepers = 0;
atomic_add(sleepers, &sem->count);
@@ -126,12 +133,14 @@ fastcall int __sched __down_interruptible(struct semaphore * sem)
* still hoping to get the semaphore.
*/
if (!atomic_add_negative(sleepers - 1, &sem->count)) {
+ trace_mark(sem_down_intr_resume, "%p", sem);
sem->sleepers = 0;
break;
}
sem->sleepers = 1; /* us - see -1 above */
spin_unlock_irqrestore(&sem->wait.lock, flags);
+ trace_mark(sem_down_intr_sched, "%p", sem);
schedule();
spin_lock_irqsave(&sem->wait.lock, flags);
"David J. Wilder" <[email protected]> writes:
> This patch adds several markers around semaphore primitives. Along
> with a tracing application this patch can be useful for measuring
> kernel semaphore usage and contention. [...]
In order to evaluate the permanent placement of markers, more
information will be needed, such as effects upon performance
and code size.
- FChE
* David J. Wilder ([email protected]) wrote:
> This patch adds several markers around semaphore primitives.
> Along with a tracing application this patch can be useful for measuring
> kernel semaphore usage and contention.
>
Yup, looks good. I'll take it into my instrumentation patchset.
I'll soon submit the markers-over-immediate values. The performance
tests should be done upon this optimized version.
Mathieu
> Signed-off-by: Mike Mason <[email protected]>
> Signed-off-by: David Wilder <[email protected]>
> ---
> lib/semaphore-sleepers.c | 9 +++++++++
> 1 files changed, 9 insertions(+), 0 deletions(-)
>
> diff --git a/lib/semaphore-sleepers.c b/lib/semaphore-sleepers.c
> index 1281805..5343a96 100644
> --- a/lib/semaphore-sleepers.c
> +++ b/lib/semaphore-sleepers.c
> @@ -15,6 +15,7 @@
> #include <linux/sched.h>
> #include <linux/err.h>
> #include <linux/init.h>
> +#include <linux/marker.h>
> #include <asm/semaphore.h>
>
> /*
> @@ -50,6 +51,7 @@
>
> fastcall void __up(struct semaphore *sem)
> {
> + trace_mark(sem_up, "%p", sem);
> wake_up(&sem->wait);
> }
>
> @@ -59,6 +61,7 @@ fastcall void __sched __down(struct semaphore * sem)
> DECLARE_WAITQUEUE(wait, tsk);
> unsigned long flags;
>
> + trace_mark(sem_down, "%p", sem);
> tsk->state = TASK_UNINTERRUPTIBLE;
> spin_lock_irqsave(&sem->wait.lock, flags);
> add_wait_queue_exclusive_locked(&sem->wait, &wait);
> @@ -73,12 +76,14 @@ fastcall void __sched __down(struct semaphore * sem)
> * the wait_queue_head.
> */
> if (!atomic_add_negative(sleepers - 1, &sem->count)) {
> + trace_mark(sem_down_resume, "%p", sem);
> sem->sleepers = 0;
> break;
> }
> sem->sleepers = 1; /* us - see -1 above */
> spin_unlock_irqrestore(&sem->wait.lock, flags);
>
> + trace_mark(sem_down_sched, "%p", sem);
> schedule();
>
> spin_lock_irqsave(&sem->wait.lock, flags);
> @@ -97,6 +102,7 @@ fastcall int __sched __down_interruptible(struct semaphore * sem)
> DECLARE_WAITQUEUE(wait, tsk);
> unsigned long flags;
>
> + trace_mark(sem_down_intr, "%p", sem);
> tsk->state = TASK_INTERRUPTIBLE;
> spin_lock_irqsave(&sem->wait.lock, flags);
> add_wait_queue_exclusive_locked(&sem->wait, &wait);
> @@ -113,6 +119,7 @@ fastcall int __sched __down_interruptible(struct semaphore * sem)
> * and exit.
> */
> if (signal_pending(current)) {
> + trace_mark(sem_down_intr_fail, "%p", sem);
> retval = -EINTR;
> sem->sleepers = 0;
> atomic_add(sleepers, &sem->count);
> @@ -126,12 +133,14 @@ fastcall int __sched __down_interruptible(struct semaphore * sem)
> * still hoping to get the semaphore.
> */
> if (!atomic_add_negative(sleepers - 1, &sem->count)) {
> + trace_mark(sem_down_intr_resume, "%p", sem);
> sem->sleepers = 0;
> break;
> }
> sem->sleepers = 1; /* us - see -1 above */
> spin_unlock_irqrestore(&sem->wait.lock, flags);
>
> + trace_mark(sem_down_intr_sched, "%p", sem);
> schedule();
>
> spin_lock_irqsave(&sem->wait.lock, flags);
>
>
> -
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--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
On Mon, 2007-11-12 at 16:52 -0800, David J. Wilder wrote:
> This patch adds several markers around semaphore primitives.
> Along with a tracing application this patch can be useful for measuring
> kernel semaphore usage and contention.
It would be much better to help in eradicating every last semaphore user
and then these statistics will be provided by lockstat.