On 09/16/2015 11:01 AM, Peter Zijlstra wrote:
On Tue, Sep 15, 2015 at 11:29:14AM -0400, Waiman Long wrote:
Only the queue head vCPU will be in pv_wait_head() spinning to acquire the
lock.
But what will guarantee fwd progress for the lock that is the head?
Suppose CPU0 becomes head and enters
On 09/16/2015 11:01 AM, Peter Zijlstra wrote:
On Tue, Sep 15, 2015 at 11:29:14AM -0400, Waiman Long wrote:
Only the queue head vCPU will be in pv_wait_head() spinning to acquire the
lock.
But what will guarantee fwd progress for the lock that is the head?
Suppose CPU0 becomes head and enters
On Tue, Sep 15, 2015 at 11:29:14AM -0400, Waiman Long wrote:
> Only the queue head vCPU will be in pv_wait_head() spinning to acquire the
> lock.
But what will guarantee fwd progress for the lock that is the head?
Suppose CPU0 becomes head and enters the /* claim the lock */ loop.
Then CPU1
On Tue, Sep 15, 2015 at 11:29:14AM -0400, Waiman Long wrote:
> Only the queue head vCPU will be in pv_wait_head() spinning to acquire the
> lock.
But what will guarantee fwd progress for the lock that is the head?
Suppose CPU0 becomes head and enters the /* claim the lock */ loop.
Then CPU1
On 09/15/2015 04:24 AM, Peter Zijlstra wrote:
On Mon, Sep 14, 2015 at 03:15:20PM -0400, Waiman Long wrote:
On 09/14/2015 10:00 AM, Peter Zijlstra wrote:
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
This patch allows one attempt for the lock waiter to steal the lock
On Mon, Sep 14, 2015 at 03:15:20PM -0400, Waiman Long wrote:
> On 09/14/2015 10:00 AM, Peter Zijlstra wrote:
> >On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
> >>This patch allows one attempt for the lock waiter to steal the lock
^^^
> >>when entering the PV
On Mon, Sep 14, 2015 at 03:15:20PM -0400, Waiman Long wrote:
> On 09/14/2015 10:00 AM, Peter Zijlstra wrote:
> >On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
> >>This patch allows one attempt for the lock waiter to steal the lock
^^^
> >>when entering the PV
On 09/15/2015 04:24 AM, Peter Zijlstra wrote:
On Mon, Sep 14, 2015 at 03:15:20PM -0400, Waiman Long wrote:
On 09/14/2015 10:00 AM, Peter Zijlstra wrote:
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
This patch allows one attempt for the lock waiter to steal the lock
On 09/14/2015 03:15 PM, Waiman Long wrote:
On 09/14/2015 10:00 AM, Peter Zijlstra wrote:
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
This patch allows one attempt for the lock waiter to steal the lock
when entering the PV slowpath. This helps to reduce the performance
penalty
On 09/14/2015 10:04 AM, Peter Zijlstra wrote:
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
This patch allows one attempt for the lock waiter to steal the lock
when entering the PV slowpath. This helps to reduce the performance
penalty caused by lock waiter preemption while not
On 09/14/2015 10:00 AM, Peter Zijlstra wrote:
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
This patch allows one attempt for the lock waiter to steal the lock
when entering the PV slowpath. This helps to reduce the performance
penalty caused by lock waiter preemption while not
On 09/14/2015 09:57 AM, Peter Zijlstra wrote:
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
+#define queued_spin_trylock(l) pv_queued_spin_trylock_unfair(l)
+static inline bool pv_queued_spin_trylock_unfair(struct qspinlock *lock)
+{
+ struct __qspinlock *l = (void *)lock;
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
> This patch allows one attempt for the lock waiter to steal the lock
> when entering the PV slowpath. This helps to reduce the performance
> penalty caused by lock waiter preemption while not having much of
> the downsides of a real
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
> This patch allows one attempt for the lock waiter to steal the lock
> when entering the PV slowpath. This helps to reduce the performance
> penalty caused by lock waiter preemption while not having much of
> the downsides of a real
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
> +#define queued_spin_trylock(l) pv_queued_spin_trylock_unfair(l)
> +static inline bool pv_queued_spin_trylock_unfair(struct qspinlock *lock)
> +{
> + struct __qspinlock *l = (void *)lock;
> +
> + if (READ_ONCE(l->locked))
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
> +#define queued_spin_trylock(l) pv_queued_spin_trylock_unfair(l)
> +static inline bool pv_queued_spin_trylock_unfair(struct qspinlock *lock)
> +{
> + struct __qspinlock *l = (void *)lock;
> +
> + if (READ_ONCE(l->locked))
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
> This patch allows one attempt for the lock waiter to steal the lock
> when entering the PV slowpath. This helps to reduce the performance
> penalty caused by lock waiter preemption while not having much of
> the downsides of a real
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
> This patch allows one attempt for the lock waiter to steal the lock
> when entering the PV slowpath. This helps to reduce the performance
> penalty caused by lock waiter preemption while not having much of
> the downsides of a real
On 09/14/2015 09:57 AM, Peter Zijlstra wrote:
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
+#define queued_spin_trylock(l) pv_queued_spin_trylock_unfair(l)
+static inline bool pv_queued_spin_trylock_unfair(struct qspinlock *lock)
+{
+ struct __qspinlock *l = (void *)lock;
On 09/14/2015 10:00 AM, Peter Zijlstra wrote:
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
This patch allows one attempt for the lock waiter to steal the lock
when entering the PV slowpath. This helps to reduce the performance
penalty caused by lock waiter preemption while not
On 09/14/2015 10:04 AM, Peter Zijlstra wrote:
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
This patch allows one attempt for the lock waiter to steal the lock
when entering the PV slowpath. This helps to reduce the performance
penalty caused by lock waiter preemption while not
On 09/14/2015 03:15 PM, Waiman Long wrote:
On 09/14/2015 10:00 AM, Peter Zijlstra wrote:
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
This patch allows one attempt for the lock waiter to steal the lock
when entering the PV slowpath. This helps to reduce the performance
penalty
This patch allows one attempt for the lock waiter to steal the lock
when entering the PV slowpath. This helps to reduce the performance
penalty caused by lock waiter preemption while not having much of
the downsides of a real unfair lock.
Linux kernel builds were run in KVM guest on an 8-socket,
This patch allows one attempt for the lock waiter to steal the lock
when entering the PV slowpath. This helps to reduce the performance
penalty caused by lock waiter preemption while not having much of
the downsides of a real unfair lock.
Linux kernel builds were run in KVM guest on an 8-socket,
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