Displaying 14 results from an estimated 14 matches for "virt_unfairlocks_en".
2014 May 30
0
[PATCH v11 09/16] qspinlock, x86: Allow unfair spinlock in a virtual guest
...lock in a native environment is generally not a good idea as
there is a possibility of lock starvation for a heavily contended lock.
This patch adds a new configuration option for the x86 architecture
to enable the use of unfair queue spinlock (AVIRT_UNFAIR_LOCKS)
in a virtual guest. A jump label (virt_unfairlocks_enabled) is
used to switch between a fair and an unfair version of the spinlock
code. This jump label will only be enabled in a virtual guest where
the X86_FEATURE_HYPERVISOR feature bit is set.
Enabling this configuration feature causes a slight decrease the
performance of an uncontended lock-unlock...
2014 Jun 11
3
[PATCH v11 09/16] qspinlock, x86: Allow unfair spinlock in a virtual guest
...+ * pending bit spinning code path which disallows lock stealing.
> + */
> + queue_spin_lock_slowpath(lock, -1);
> +}
Why is this needed?
> +/*
> + * Redefine arch_spin_lock and arch_spin_trylock as inline functions that will
> + * jump to the unfair versions if the static key virt_unfairlocks_enabled
> + * is true.
> + */
> +#undef arch_spin_lock
> +#undef arch_spin_trylock
> +#undef arch_spin_lock_flags
> +
> +/**
> + * arch_spin_lock - acquire a queue spinlock
> + * @lock: Pointer to queue spinlock structure
> + */
> +static inline void arch_spin_lock(str...
2014 Jun 11
3
[PATCH v11 09/16] qspinlock, x86: Allow unfair spinlock in a virtual guest
...+ * pending bit spinning code path which disallows lock stealing.
> + */
> + queue_spin_lock_slowpath(lock, -1);
> +}
Why is this needed?
> +/*
> + * Redefine arch_spin_lock and arch_spin_trylock as inline functions that will
> + * jump to the unfair versions if the static key virt_unfairlocks_enabled
> + * is true.
> + */
> +#undef arch_spin_lock
> +#undef arch_spin_trylock
> +#undef arch_spin_lock_flags
> +
> +/**
> + * arch_spin_lock - acquire a queue spinlock
> + * @lock: Pointer to queue spinlock structure
> + */
> +static inline void arch_spin_lock(str...
2014 Jun 12
0
[PATCH v11 09/16] qspinlock, x86: Allow unfair spinlock in a virtual guest
...llow either unfair or paravirt spinlock,
but not both. I do think that a little bit of unfairness will help in
the virtual environment.
>> +/*
>> + * Redefine arch_spin_lock and arch_spin_trylock as inline functions that will
>> + * jump to the unfair versions if the static key virt_unfairlocks_enabled
>> + * is true.
>> + */
>> +#undef arch_spin_lock
>> +#undef arch_spin_trylock
>> +#undef arch_spin_lock_flags
>> +
>> +/**
>> + * arch_spin_lock - acquire a queue spinlock
>> + * @lock: Pointer to queue spinlock structure
>> + */
>...
2014 May 08
1
[PATCH v10 10/19] qspinlock, x86: Allow unfair spinlock in a virtual guest
...t; --- a/kernel/locking/qspinlock.c
> +++ b/kernel/locking/qspinlock.c
> @@ -227,6 +227,14 @@ static __always_inline int get_qlock(struct qspinlock *lock)
> {
> struct __qspinlock *l = (void *)lock;
>
> +#ifdef CONFIG_PARAVIRT_UNFAIR_LOCKS
> + if (static_key_false(¶virt_unfairlocks_enabled))
> + /*
> + * Need to use atomic operation to get the lock when
> + * lock stealing can happen.
> + */
> + return cmpxchg(&l->locked, 0, _Q_LOCKED_VAL) == 0;
That's missing {}.
> +#endif
> barrier();
> ACCESS_ONCE(l->locked) = _Q_LOCKED_VA...
2014 May 08
1
[PATCH v10 10/19] qspinlock, x86: Allow unfair spinlock in a virtual guest
...t; --- a/kernel/locking/qspinlock.c
> +++ b/kernel/locking/qspinlock.c
> @@ -227,6 +227,14 @@ static __always_inline int get_qlock(struct qspinlock *lock)
> {
> struct __qspinlock *l = (void *)lock;
>
> +#ifdef CONFIG_PARAVIRT_UNFAIR_LOCKS
> + if (static_key_false(¶virt_unfairlocks_enabled))
> + /*
> + * Need to use atomic operation to get the lock when
> + * lock stealing can happen.
> + */
> + return cmpxchg(&l->locked, 0, _Q_LOCKED_VAL) == 0;
That's missing {}.
> +#endif
> barrier();
> ACCESS_ONCE(l->locked) = _Q_LOCKED_VA...
2014 Jun 12
2
[PATCH v11 14/16] pvqspinlock: Add qspinlock para-virtualization support
On Fri, May 30, 2014 at 11:44:00AM -0400, Waiman Long wrote:
> @@ -19,13 +19,46 @@ extern struct static_key virt_unfairlocks_enabled;
> * that the clearing the lock bit is done ASAP without artificial delay
> * due to compiler optimization.
> */
> +#ifdef CONFIG_PARAVIRT_SPINLOCKS
> +static __always_inline void __queue_spin_unlock(struct qspinlock *lock)
> +#else
> static inline void queue_spin_u...
2014 Jun 12
2
[PATCH v11 14/16] pvqspinlock: Add qspinlock para-virtualization support
On Fri, May 30, 2014 at 11:44:00AM -0400, Waiman Long wrote:
> @@ -19,13 +19,46 @@ extern struct static_key virt_unfairlocks_enabled;
> * that the clearing the lock bit is done ASAP without artificial delay
> * due to compiler optimization.
> */
> +#ifdef CONFIG_PARAVIRT_SPINLOCKS
> +static __always_inline void __queue_spin_unlock(struct qspinlock *lock)
> +#else
> static inline void queue_spin_u...
2014 May 30
19
[PATCH v11 00/16] qspinlock: a 4-byte queue spinlock with PV support
v10->v11:
- Use a simple test-and-set unfair lock to simplify the code,
but performance may suffer a bit for large guest with many CPUs.
- Take out Raghavendra KT's test results as the unfair lock changes
may render some of his results invalid.
- Add PV support without increasing the size of the core queue node
structure.
- Other minor changes to address some of the
2014 May 30
19
[PATCH v11 00/16] qspinlock: a 4-byte queue spinlock with PV support
v10->v11:
- Use a simple test-and-set unfair lock to simplify the code,
but performance may suffer a bit for large guest with many CPUs.
- Take out Raghavendra KT's test results as the unfair lock changes
may render some of his results invalid.
- Add PV support without increasing the size of the core queue node
structure.
- Other minor changes to address some of the
2014 Jun 12
0
[PATCH v11 14/16] pvqspinlock: Add qspinlock para-virtualization support
On 06/12/2014 04:17 AM, Peter Zijlstra wrote:
> On Fri, May 30, 2014 at 11:44:00AM -0400, Waiman Long wrote:
>> @@ -19,13 +19,46 @@ extern struct static_key virt_unfairlocks_enabled;
>> * that the clearing the lock bit is done ASAP without artificial delay
>> * due to compiler optimization.
>> */
>> +#ifdef CONFIG_PARAVIRT_SPINLOCKS
>> +static __always_inline void __queue_spin_unlock(struct qspinlock *lock)
>> +#else
>>...
2014 May 30
0
[PATCH v11 14/16] pvqspinlock: Add qspinlock para-virtualization support
...kick_cpu(pv->mycpu);
+}
+
+#endif /* _ASM_X86_PVQSPINLOCK_H */
diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
index 448de8b..5ddc456 100644
--- a/arch/x86/include/asm/qspinlock.h
+++ b/arch/x86/include/asm/qspinlock.h
@@ -19,13 +19,46 @@ extern struct static_key virt_unfairlocks_enabled;
* that the clearing the lock bit is done ASAP without artificial delay
* due to compiler optimization.
*/
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+static __always_inline void __queue_spin_unlock(struct qspinlock *lock)
+#else
static inline void queue_spin_unlock(struct qspinlock *lock)
+#end...
2014 May 07
32
[PATCH v10 00/19] qspinlock: a 4-byte queue spinlock with PV support
v9->v10:
- Make some minor changes to qspinlock.c to accommodate review feedback.
- Change author to PeterZ for 2 of the patches.
- Include Raghavendra KT's test results in patch 18.
v8->v9:
- Integrate PeterZ's version of the queue spinlock patch with some
modification:
http://lkml.kernel.org/r/20140310154236.038181843 at infradead.org
- Break the more complex
2014 May 07
32
[PATCH v10 00/19] qspinlock: a 4-byte queue spinlock with PV support
v9->v10:
- Make some minor changes to qspinlock.c to accommodate review feedback.
- Change author to PeterZ for 2 of the patches.
- Include Raghavendra KT's test results in patch 18.
v8->v9:
- Integrate PeterZ's version of the queue spinlock patch with some
modification:
http://lkml.kernel.org/r/20140310154236.038181843 at infradead.org
- Break the more complex