Displaying 20 results from an estimated 46 matches for "trylock_pending".
2014 Apr 23
0
[PATCH v9 05/19] qspinlock: Optimize for smaller NR_CPUS
...val)
> {
> struct __qspinlock *l = (void *)lock;
>
> - ACCESS_ONCE(l->locked_pending) = 1;
> + ACCESS_ONCE(l->locked_pending) = _Q_LOCKED_VAL;
> }
>
> /*
> @@ -567,16 +563,16 @@ static __always_inline int get_qlock(struct qspinlock *lock)
> /**
> * trylock_pending - try to acquire queue spinlock using the pending bit
> * @lock : Pointer to queue spinlock structure
> - * @pval : Pointer to value of the queue spinlock 32-bit word
> + * @val : Current value of the queue spinlock 32-bit word
> * Return: 1 if lock acquired, 0 otherwise
> *
&...
2014 May 08
1
[PATCH v10 03/19] qspinlock: Add pending bit
On Wed, May 07, 2014 at 11:01:31AM -0400, Waiman Long wrote:
> +/**
> + * trylock_pending - try to acquire queue spinlock using the pending bit
> + * @lock : Pointer to queue spinlock structure
> + * @pval : Pointer to value of the queue spinlock 32-bit word
> + * Return: 1 if lock acquired, 0 otherwise
> + */
> +static inline int trylock_pending(struct qspinlock *lock, u...
2014 May 08
1
[PATCH v10 03/19] qspinlock: Add pending bit
On Wed, May 07, 2014 at 11:01:31AM -0400, Waiman Long wrote:
> +/**
> + * trylock_pending - try to acquire queue spinlock using the pending bit
> + * @lock : Pointer to queue spinlock structure
> + * @pval : Pointer to value of the queue spinlock 32-bit word
> + * Return: 1 if lock acquired, 0 otherwise
> + */
> +static inline int trylock_pending(struct qspinlock *lock, u...
2014 Apr 23
2
[PATCH v9 05/19] qspinlock: Optimize for smaller NR_CPUS
On 04/18/2014 05:40 PM, Waiman Long wrote:
> On 04/18/2014 03:05 PM, Peter Zijlstra wrote:
>> On Fri, Apr 18, 2014 at 01:52:50PM -0400, Waiman Long wrote:
>>> I am confused by your notation.
>> Nah, I think I was confused :-) Make the 1 _Q_LOCKED_VAL though, as
>> that's the proper constant to use.
>
> Everyone gets confused once in a while:-) I have plenty
2014 Apr 23
2
[PATCH v9 05/19] qspinlock: Optimize for smaller NR_CPUS
On 04/18/2014 05:40 PM, Waiman Long wrote:
> On 04/18/2014 03:05 PM, Peter Zijlstra wrote:
>> On Fri, Apr 18, 2014 at 01:52:50PM -0400, Waiman Long wrote:
>>> I am confused by your notation.
>> Nah, I think I was confused :-) Make the 1 _Q_LOCKED_VAL though, as
>> that's the proper constant to use.
>
> Everyone gets confused once in a while:-) I have plenty
2014 Apr 17
2
[PATCH v9 06/19] qspinlock: prolong the stay in the pending bit path
On Thu, Apr 17, 2014 at 11:03:58AM -0400, Waiman Long wrote:
> There is a problem in the current trylock_pending() function. When the
> lock is free, but the pending bit holder hasn't grabbed the lock &
> cleared the pending bit yet, the trylock_pending() function will fail.
I remember seeing some of this..
> It can be seen that the queue spinlock is slower than the ticket
> spinlock wh...
2014 Apr 17
2
[PATCH v9 06/19] qspinlock: prolong the stay in the pending bit path
On Thu, Apr 17, 2014 at 11:03:58AM -0400, Waiman Long wrote:
> There is a problem in the current trylock_pending() function. When the
> lock is free, but the pending bit holder hasn't grabbed the lock &
> cleared the pending bit yet, the trylock_pending() function will fail.
I remember seeing some of this..
> It can be seen that the queue spinlock is slower than the ticket
> spinlock wh...
2014 May 07
0
[PATCH v10 06/19] qspinlock: prolong the stay in the pending bit path
There is a problem in the current trylock_pending() function. When the
lock is free, but the pending bit holder hasn't grabbed the lock &
cleared the pending bit yet, the trylock_pending() function will fail.
As a result, the regular queuing code path will be used most of
the time even when there is only 2 tasks contending for the lock.
A...
2014 Apr 17
0
[PATCH v9 06/19] qspinlock: prolong the stay in the pending bit path
There is a problem in the current trylock_pending() function. When the
lock is free, but the pending bit holder hasn't grabbed the lock &
cleared the pending bit yet, the trylock_pending() function will fail.
As a result, the regular queuing code path will be used most of
the time even when there is only 2 tasks contending for the lock.
A...
2014 Apr 17
2
[PATCH v9 03/19] qspinlock: Add pending bit
On Thu, Apr 17, 2014 at 11:03:55AM -0400, Waiman Long wrote:
> +/**
> + * trylock_pending - try to acquire queue spinlock using the pending bit
> + * @lock : Pointer to queue spinlock structure
> + * @pval : Pointer to value of the queue spinlock 32-bit word
> + * Return: 1 if lock acquired, 0 otherwise
> + */
> +static inline int trylock_pending(struct qspinlock *lock, u...
2014 Apr 17
2
[PATCH v9 03/19] qspinlock: Add pending bit
On Thu, Apr 17, 2014 at 11:03:55AM -0400, Waiman Long wrote:
> +/**
> + * trylock_pending - try to acquire queue spinlock using the pending bit
> + * @lock : Pointer to queue spinlock structure
> + * @pval : Pointer to value of the queue spinlock 32-bit word
> + * Return: 1 if lock acquired, 0 otherwise
> + */
> +static inline int trylock_pending(struct qspinlock *lock, u...
2014 Apr 18
0
[PATCH v9 06/19] qspinlock: prolong the stay in the pending bit path
On 04/17/2014 12:36 PM, Peter Zijlstra wrote:
> On Thu, Apr 17, 2014 at 11:03:58AM -0400, Waiman Long wrote:
>> There is a problem in the current trylock_pending() function. When the
>> lock is free, but the pending bit holder hasn't grabbed the lock&
>> cleared the pending bit yet, the trylock_pending() function will fail.
> I remember seeing some of this..
>
>> It can be seen that the queue spinlock is slower than the tick...
2014 May 07
0
[PATCH v10 03/19] qspinlock: Add pending bit
...x b97a1ad..6467bfc 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -83,23 +83,97 @@ static inline struct mcs_spinlock *decode_tail(u32 tail)
return per_cpu_ptr(&mcs_nodes[idx], cpu);
}
+#define _Q_LOCKED_PENDING_MASK (_Q_LOCKED_MASK | _Q_PENDING_MASK)
+
+/**
+ * trylock_pending - try to acquire queue spinlock using the pending bit
+ * @lock : Pointer to queue spinlock structure
+ * @pval : Pointer to value of the queue spinlock 32-bit word
+ * Return: 1 if lock acquired, 0 otherwise
+ */
+static inline int trylock_pending(struct qspinlock *lock, u32 *pval)
+{
+ u32 old, n...
2014 Apr 17
2
[PATCH v9 05/19] qspinlock: Optimize for smaller NR_CPUS
...14 at 11:03:57AM -0400, Waiman Long wrote:
> +static __always_inline void
> +clear_pending_set_locked(struct qspinlock *lock, u32 val)
> +{
> + struct __qspinlock *l = (void *)lock;
> +
> + ACCESS_ONCE(l->locked_pending) = 1;
> +}
> @@ -157,8 +251,13 @@ static inline int trylock_pending(struct qspinlock *lock, u32 *pval)
> * we're pending, wait for the owner to go away.
> *
> * *,1,1 -> *,1,0
> + *
> + * this wait loop must be a load-acquire such that we match the
> + * store-release that clears the locked bit and create lock
> + * sequenti...
2014 Apr 17
2
[PATCH v9 05/19] qspinlock: Optimize for smaller NR_CPUS
...14 at 11:03:57AM -0400, Waiman Long wrote:
> +static __always_inline void
> +clear_pending_set_locked(struct qspinlock *lock, u32 val)
> +{
> + struct __qspinlock *l = (void *)lock;
> +
> + ACCESS_ONCE(l->locked_pending) = 1;
> +}
> @@ -157,8 +251,13 @@ static inline int trylock_pending(struct qspinlock *lock, u32 *pval)
> * we're pending, wait for the owner to go away.
> *
> * *,1,1 -> *,1,0
> + *
> + * this wait loop must be a load-acquire such that we match the
> + * store-release that clears the locked bit and create lock
> + * sequenti...
2014 Apr 17
0
[PATCH v9 05/19] qspinlock: Optimize for smaller NR_CPUS
...d;
+ }
+}
+
/**
* xchg_tail - Put in the new queue tail code word & retrieve previous one
* @lock : Pointer to queue spinlock structure
@@ -112,12 +201,17 @@ xchg_tail(struct qspinlock *lock, u32 tail, u32 *pval)
*pval = new;
return old;
}
+#endif /* _Q_PENDING_BITS == 8 */
/**
* trylock_pending - try to acquire queue spinlock using the pending bit
* @lock : Pointer to queue spinlock structure
* @pval : Pointer to value of the queue spinlock 32-bit word
* Return: 1 if lock acquired, 0 otherwise
+ *
+ * The pending bit won't be set as soon as one or more tasks queue up.
+ * This f...
2014 Apr 18
2
[PATCH v9 05/19] qspinlock: Optimize for smaller NR_CPUS
...__always_inline void
> >>+clear_pending_set_locked(struct qspinlock *lock, u32 val)
> >>+{
> >>+ struct __qspinlock *l = (void *)lock;
> >>+
> >>+ ACCESS_ONCE(l->locked_pending) = 1;
> >>+}
> >>@@ -157,8 +251,13 @@ static inline int trylock_pending(struct qspinlock *lock, u32 *pval)
> >> * we're pending, wait for the owner to go away.
> >> *
> >> * *,1,1 -> *,1,0
> >>+ *
> >>+ * this wait loop must be a load-acquire such that we match the
> >>+ * store-release that clea...
2014 Apr 18
2
[PATCH v9 05/19] qspinlock: Optimize for smaller NR_CPUS
...__always_inline void
> >>+clear_pending_set_locked(struct qspinlock *lock, u32 val)
> >>+{
> >>+ struct __qspinlock *l = (void *)lock;
> >>+
> >>+ ACCESS_ONCE(l->locked_pending) = 1;
> >>+}
> >>@@ -157,8 +251,13 @@ static inline int trylock_pending(struct qspinlock *lock, u32 *pval)
> >> * we're pending, wait for the owner to go away.
> >> *
> >> * *,1,1 -> *,1,0
> >>+ *
> >>+ * this wait loop must be a load-acquire such that we match the
> >>+ * store-release that clea...
2014 Apr 18
2
[PATCH v9 04/19] qspinlock: Extract out the exchange of tail code word
....
> >> */
> >>+ if (!(val& _Q_TAIL_MASK)&& queue_spin_trylock(lock))
> >>+ goto release;
> >But you just did a potentially very expensive op; @val isn't
> >representative anymore!
>
> That is not true. I pass in a pointer to val to trylock_pending() (the
> pointer thing) so that it will store the latest value that it reads from the
> lock back into val. I did miss one in the PV qspinlock exit loop. I will add
> it back when I do the next version.
But you did that read _before_ you touched a cold cacheline, that's 100s
of cycles...
2014 Apr 18
2
[PATCH v9 04/19] qspinlock: Extract out the exchange of tail code word
....
> >> */
> >>+ if (!(val& _Q_TAIL_MASK)&& queue_spin_trylock(lock))
> >>+ goto release;
> >But you just did a potentially very expensive op; @val isn't
> >representative anymore!
>
> That is not true. I pass in a pointer to val to trylock_pending() (the
> pointer thing) so that it will store the latest value that it reads from the
> lock back into val. I did miss one in the PV qspinlock exit loop. I will add
> it back when I do the next version.
But you did that read _before_ you touched a cold cacheline, that's 100s
of cycles...