Displaying 20 results from an estimated 33 matches for "mayhalt".
2015 Apr 24
0
[PATCH v16 13/14] pvqspinlock: Improve slowpath performance by avoiding cmpxchg
In the pv_scan_next() function, the slow cmpxchg atomic operation is
performed even if the other CPU is not even close to being halted. This
extra cmpxchg can harm slowpath performance.
This patch introduces the new mayhalt flag to indicate if the other
spinning CPU is close to being halted or not. The current threshold
for x86 is 2k cpu_relax() calls. If this flag is not set, the other
spinning CPU will have at least 2k more cpu_relax() calls before
it can enter the halt state. This should give enough time for the
se...
2015 Apr 29
4
[PATCH v16 13/14] pvqspinlock: Improve slowpath performance by avoiding cmpxchg
...Fri, Apr 24, 2015 at 02:56:42PM -0400, Waiman Long wrote:
> In the pv_scan_next() function, the slow cmpxchg atomic operation is
> performed even if the other CPU is not even close to being halted. This
> extra cmpxchg can harm slowpath performance.
>
> This patch introduces the new mayhalt flag to indicate if the other
> spinning CPU is close to being halted or not. The current threshold
> for x86 is 2k cpu_relax() calls. If this flag is not set, the other
> spinning CPU will have at least 2k more cpu_relax() calls before
> it can enter the halt state. This should give en...
2015 Apr 29
4
[PATCH v16 13/14] pvqspinlock: Improve slowpath performance by avoiding cmpxchg
...Fri, Apr 24, 2015 at 02:56:42PM -0400, Waiman Long wrote:
> In the pv_scan_next() function, the slow cmpxchg atomic operation is
> performed even if the other CPU is not even close to being halted. This
> extra cmpxchg can harm slowpath performance.
>
> This patch introduces the new mayhalt flag to indicate if the other
> spinning CPU is close to being halted or not. The current threshold
> for x86 is 2k cpu_relax() calls. If this flag is not set, the other
> spinning CPU will have at least 2k more cpu_relax() calls before
> it can enter the halt state. This should give en...
2014 May 30
0
[PATCH v11 14/16] pvqspinlock: Add qspinlock para-virtualization support
...CPU (in pv_queue_spin_check) and the
+ * the status check by the previous queue head (in pv_halt_check).
+ * See the comments on those functions to see how the races are being
+ * addressed.
+ */
+
+/*
+ * Spin threshold for queue spinlock
+ */
+#define QSPIN_THRESHOLD (1U<<14)
+#define MAYHALT_THRESHOLD (QSPIN_THRESHOLD - 0x10)
+
+/*
+ * CPU state flags
+ */
+#define PV_CPU_ACTIVE 1 /* This CPU is active */
+#define PV_CPU_KICKED 2 /* This CPU is being kicked */
+#define PV_CPU_HALTED -1 /* This CPU is halted */
+
+/*
+ * Additional fields to be added to the queue node structure
+...
2015 Apr 29
0
[PATCH v16 13/14] pvqspinlock: Improve slowpath performance by avoiding cmpxchg
...t 02:56:42PM -0400, Waiman Long wrote:
>> In the pv_scan_next() function, the slow cmpxchg atomic operation is
>> performed even if the other CPU is not even close to being halted. This
>> extra cmpxchg can harm slowpath performance.
>>
>> This patch introduces the new mayhalt flag to indicate if the other
>> spinning CPU is close to being halted or not. The current threshold
>> for x86 is 2k cpu_relax() calls. If this flag is not set, the other
>> spinning CPU will have at least 2k more cpu_relax() calls before
>> it can enter the halt state. Thi...
2014 Oct 16
2
[PATCH v12 09/11] pvqspinlock, x86: Add para-virtualization support
...n pv_link_and_wait_node) and the
+ * the status check by the previous queue head (in pv_wait_check).
+ *
+ * See the comments on those functions to see how the races are being
+ * addressed.
+ */
+
+/*
+ * Spin thresholds for queue spinlock
+ */
+#define QSPIN_THRESHOLD SPIN_THRESHOLD
+#define MAYHALT_THRESHOLD 0x10
+
+/*
+ * CPU state flags
+ */
+#define PV_CPU_ACTIVE 1 /* This CPU is active */
+#define PV_CPU_KICKED 2 /* This CPU is being kicked */
+#define PV_CPU_HALTED -1 /* This CPU is halted */
+
+/*
+ * Special head node pointer value
+ */
+#define PV_INVALID_HEAD NULL
+
+/*
+ * Ad...
2014 Oct 16
2
[PATCH v12 09/11] pvqspinlock, x86: Add para-virtualization support
...n pv_link_and_wait_node) and the
+ * the status check by the previous queue head (in pv_wait_check).
+ *
+ * See the comments on those functions to see how the races are being
+ * addressed.
+ */
+
+/*
+ * Spin thresholds for queue spinlock
+ */
+#define QSPIN_THRESHOLD SPIN_THRESHOLD
+#define MAYHALT_THRESHOLD 0x10
+
+/*
+ * CPU state flags
+ */
+#define PV_CPU_ACTIVE 1 /* This CPU is active */
+#define PV_CPU_KICKED 2 /* This CPU is being kicked */
+#define PV_CPU_HALTED -1 /* This CPU is halted */
+
+/*
+ * Special head node pointer value
+ */
+#define PV_INVALID_HEAD NULL
+
+/*
+ * Ad...
2014 Oct 29
1
[PATCH v13 09/11] pvqspinlock, x86: Add para-virtualization support
...n pv_link_and_wait_node) and the
+ * the status check by the previous queue head (in pv_wait_check).
+ *
+ * See the comments on those functions to see how the races are being
+ * addressed.
+ */
+
+/*
+ * Spin thresholds for queue spinlock
+ */
+#define QSPIN_THRESHOLD SPIN_THRESHOLD
+#define MAYHALT_THRESHOLD 0x10
+
+/*
+ * CPU state flags
+ */
+#define PV_CPU_ACTIVE 1 /* This CPU is active */
+#define PV_CPU_KICKED 2 /* This CPU is being kicked */
+#define PV_CPU_HALTED -1 /* This CPU is halted */
+
+/*
+ * Special head node pointer value
+ */
+#define PV_INVALID_HEAD NULL
+
+/*
+ * Ad...
2014 Oct 29
1
[PATCH v13 09/11] pvqspinlock, x86: Add para-virtualization support
...n pv_link_and_wait_node) and the
+ * the status check by the previous queue head (in pv_wait_check).
+ *
+ * See the comments on those functions to see how the races are being
+ * addressed.
+ */
+
+/*
+ * Spin thresholds for queue spinlock
+ */
+#define QSPIN_THRESHOLD SPIN_THRESHOLD
+#define MAYHALT_THRESHOLD 0x10
+
+/*
+ * CPU state flags
+ */
+#define PV_CPU_ACTIVE 1 /* This CPU is active */
+#define PV_CPU_KICKED 2 /* This CPU is being kicked */
+#define PV_CPU_HALTED -1 /* This CPU is halted */
+
+/*
+ * Special head node pointer value
+ */
+#define PV_INVALID_HEAD NULL
+
+/*
+ * Ad...
2015 May 04
1
[PATCH v16 13/14] pvqspinlock: Improve slowpath performance by avoiding cmpxchg
...aiman Long wrote:
> >>In the pv_scan_next() function, the slow cmpxchg atomic operation is
> >>performed even if the other CPU is not even close to being halted. This
> >>extra cmpxchg can harm slowpath performance.
> >>
> >>This patch introduces the new mayhalt flag to indicate if the other
> >>spinning CPU is close to being halted or not. The current threshold
> >>for x86 is 2k cpu_relax() calls. If this flag is not set, the other
> >>spinning CPU will have at least 2k more cpu_relax() calls before
> >>it can enter the...
2015 May 04
1
[PATCH v16 13/14] pvqspinlock: Improve slowpath performance by avoiding cmpxchg
...aiman Long wrote:
> >>In the pv_scan_next() function, the slow cmpxchg atomic operation is
> >>performed even if the other CPU is not even close to being halted. This
> >>extra cmpxchg can harm slowpath performance.
> >>
> >>This patch introduces the new mayhalt flag to indicate if the other
> >>spinning CPU is close to being halted or not. The current threshold
> >>for x86 is 2k cpu_relax() calls. If this flag is not set, the other
> >>spinning CPU will have at least 2k more cpu_relax() calls before
> >>it can enter the...
2015 Apr 24
16
[PATCH v16 00/14] qspinlock: a 4-byte queue spinlock with PV support
...governors.
v13->v14:
- Patches 1 & 2: Add queue_spin_unlock_wait() to accommodate commit
78bff1c86 from Oleg Nesterov.
- Fix the system hang problem when using PV qspinlock in an
over-committed guest due to a racing condition in the
pv_set_head_in_tail() function.
- Increase the MAYHALT_THRESHOLD from 10 to 1024.
- Change kick_cpu into a regular function pointer instead of a
callee-saved function.
- Change lock statistics code to use separate bits for different
statistics.
v12->v13:
- Change patch 9 to generate separate versions of the
queue_spin_lock_slowpath func...
2015 Apr 24
16
[PATCH v16 00/14] qspinlock: a 4-byte queue spinlock with PV support
...governors.
v13->v14:
- Patches 1 & 2: Add queue_spin_unlock_wait() to accommodate commit
78bff1c86 from Oleg Nesterov.
- Fix the system hang problem when using PV qspinlock in an
over-committed guest due to a racing condition in the
pv_set_head_in_tail() function.
- Increase the MAYHALT_THRESHOLD from 10 to 1024.
- Change kick_cpu into a regular function pointer instead of a
callee-saved function.
- Change lock statistics code to use separate bits for different
statistics.
v12->v13:
- Change patch 9 to generate separate versions of the
queue_spin_lock_slowpath func...
2014 Oct 24
3
[PATCH v12 09/11] pvqspinlock, x86: Add para-virtualization support
...>> +{
>> + struct pv_qnode *pn = (struct pv_qnode *)node;
>> +
>> + BUILD_BUG_ON(sizeof(struct pv_qnode)> 5*sizeof(struct mcs_spinlock));
>> +
>> + if (!pv_enabled())
>> + return;
>> +
>> + pn->cpustate = PV_CPU_ACTIVE;
>> + pn->mayhalt = false;
>> + pn->mycpu = smp_processor_id();
>> + pn->head = PV_INVALID_HEAD;
>> +}
>
>> @@ -333,6 +393,7 @@ queue:
>> node += idx;
>> node->locked = 0;
>> node->next = NULL;
>> + pv_init_node(node);
>>
>>...
2014 Oct 24
3
[PATCH v12 09/11] pvqspinlock, x86: Add para-virtualization support
...>> +{
>> + struct pv_qnode *pn = (struct pv_qnode *)node;
>> +
>> + BUILD_BUG_ON(sizeof(struct pv_qnode)> 5*sizeof(struct mcs_spinlock));
>> +
>> + if (!pv_enabled())
>> + return;
>> +
>> + pn->cpustate = PV_CPU_ACTIVE;
>> + pn->mayhalt = false;
>> + pn->mycpu = smp_processor_id();
>> + pn->head = PV_INVALID_HEAD;
>> +}
>
>> @@ -333,6 +393,7 @@ queue:
>> node += idx;
>> node->locked = 0;
>> node->next = NULL;
>> + pv_init_node(node);
>>
>>...
2015 Apr 07
18
[PATCH v15 00/15] qspinlock: a 4-byte queue spinlock with PV support
...governors.
v13->v14:
- Patches 1 & 2: Add queue_spin_unlock_wait() to accommodate commit
78bff1c86 from Oleg Nesterov.
- Fix the system hang problem when using PV qspinlock in an
over-committed guest due to a racing condition in the
pv_set_head_in_tail() function.
- Increase the MAYHALT_THRESHOLD from 10 to 1024.
- Change kick_cpu into a regular function pointer instead of a
callee-saved function.
- Change lock statistics code to use separate bits for different
statistics.
v12->v13:
- Change patch 9 to generate separate versions of the
queue_spin_lock_slowpath func...
2015 Apr 07
18
[PATCH v15 00/15] qspinlock: a 4-byte queue spinlock with PV support
...governors.
v13->v14:
- Patches 1 & 2: Add queue_spin_unlock_wait() to accommodate commit
78bff1c86 from Oleg Nesterov.
- Fix the system hang problem when using PV qspinlock in an
over-committed guest due to a racing condition in the
pv_set_head_in_tail() function.
- Increase the MAYHALT_THRESHOLD from 10 to 1024.
- Change kick_cpu into a regular function pointer instead of a
callee-saved function.
- Change lock statistics code to use separate bits for different
statistics.
v12->v13:
- Change patch 9 to generate separate versions of the
queue_spin_lock_slowpath func...
2015 Apr 30
0
[PATCH v16 13/14] pvqspinlock: Improve slowpath performance by avoiding cmpxchg
...t 02:56:42PM -0400, Waiman Long wrote:
>> In the pv_scan_next() function, the slow cmpxchg atomic operation is
>> performed even if the other CPU is not even close to being halted. This
>> extra cmpxchg can harm slowpath performance.
>>
>> This patch introduces the new mayhalt flag to indicate if the other
>> spinning CPU is close to being halted or not. The current threshold
>> for x86 is 2k cpu_relax() calls. If this flag is not set, the other
>> spinning CPU will have at least 2k more cpu_relax() calls before
>> it can enter the halt state. Thi...
2014 Oct 24
0
[PATCH v12 09/11] pvqspinlock, x86: Add para-virtualization support
...pv_init_node(struct mcs_spinlock *node)
> +{
> + struct pv_qnode *pn = (struct pv_qnode *)node;
> +
> + BUILD_BUG_ON(sizeof(struct pv_qnode) > 5*sizeof(struct mcs_spinlock));
> +
> + if (!pv_enabled())
> + return;
> +
> + pn->cpustate = PV_CPU_ACTIVE;
> + pn->mayhalt = false;
> + pn->mycpu = smp_processor_id();
> + pn->head = PV_INVALID_HEAD;
> +}
> @@ -333,6 +393,7 @@ queue:
> node += idx;
> node->locked = 0;
> node->next = NULL;
> + pv_init_node(node);
>
> /*
> * We touched a (possibly) cold...
2014 Oct 16
15
[PATCH v12 00/11] qspinlock: a 4-byte queue spinlock with PV support
v11->v12:
- Based on PeterZ's version of the qspinlock patch
(https://lkml.org/lkml/2014/6/15/63).
- Incorporated many of the review comments from Konrad Wilk and
Paolo Bonzini.
- The pvqspinlock code is largely from my previous version with
PeterZ's way of going from queue tail to head and his idea of
using callee saved calls to KVM and XEN codes.
v10->v11:
- Use a