search for: qspin_threshold

On 12/03/14 18:54, Waiman Long wrote: > This patch adds para-virtualization support to the queue spinlock in > the same way as was done in the PV ticket lock code. In essence, the > lock waiters will spin for a specified number of times (QSPIN_THRESHOLD > = 2^14) and then halted itself. The queue head waiter will spins > 2*QSPIN_THRESHOLD times before halting itself. When it has spinned > QSPIN_THRESHOLD times, the queue head will assume that the lock > holder may be scheduled out and attempt to kick the lock holder CPU > if it has...

On 12/03/14 18:54, Waiman Long wrote: > This patch adds para-virtualization support to the queue spinlock in > the same way as was done in the PV ticket lock code. In essence, the > lock waiters will spin for a specified number of times (QSPIN_THRESHOLD > = 2^14) and then halted itself. The queue head waiter will spins > 2*QSPIN_THRESHOLD times before halting itself. When it has spinned > QSPIN_THRESHOLD times, the queue head will assume that the lock > holder may be scheduled out and attempt to kick the lock holder CPU > if it has...

This patch adds para-virtualization support to the queue spinlock in the same way as was done in the PV ticket lock code. In essence, the lock waiters will spin for a specified number of times (QSPIN_THRESHOLD = 2^14) and then halted itself. The queue head waiter will spins 2*QSPIN_THRESHOLD times before halting itself. When it has spinned QSPIN_THRESHOLD times, the queue head will assume that the lock holder may be scheduled out and attempt to kick the lock holder CPU if it has the CPU number on hand. B...

...Vrabel ha scritto: >> On 12/03/14 18:54, Waiman Long wrote: >>> This patch adds para-virtualization support to the queue spinlock in >>> the same way as was done in the PV ticket lock code. In essence, the >>> lock waiters will spin for a specified number of times (QSPIN_THRESHOLD >>> = 2^14) and then halted itself. The queue head waiter will spins >>> 2*QSPIN_THRESHOLD times before halting itself. When it has spinned >>> QSPIN_THRESHOLD times, the queue head will assume that the lock >>> holder may be scheduled out and attempt to kick the...

...Vrabel ha scritto: >> On 12/03/14 18:54, Waiman Long wrote: >>> This patch adds para-virtualization support to the queue spinlock in >>> the same way as was done in the PV ticket lock code. In essence, the >>> lock waiters will spin for a specified number of times (QSPIN_THRESHOLD >>> = 2^14) and then halted itself. The queue head waiter will spins >>> 2*QSPIN_THRESHOLD times before halting itself. When it has spinned >>> QSPIN_THRESHOLD times, the queue head will assume that the lock >>> holder may be scheduled out and attempt to kick the...

...014 12:21, David Vrabel ha scritto: > On 12/03/14 18:54, Waiman Long wrote: >> This patch adds para-virtualization support to the queue spinlock in >> the same way as was done in the PV ticket lock code. In essence, the >> lock waiters will spin for a specified number of times (QSPIN_THRESHOLD >> = 2^14) and then halted itself. The queue head waiter will spins >> 2*QSPIN_THRESHOLD times before halting itself. When it has spinned >> QSPIN_THRESHOLD times, the queue head will assume that the lock >> holder may be scheduled out and attempt to kick the lock holder CPU...

This patch adds base para-virtualization support to the queue spinlock in the same way as was done in the PV ticket lock code. In essence, the lock waiters will spin for a specified number of times (QSPIN_THRESHOLD = 2^14) and then halted itself. The queue head waiter, unlike the other waiter, will spins 2*QSPIN_THRESHOLD times before halting itself. Before being halted, the queue head waiter will set a flag (_Q_LOCKED_SLOWPATH) in the lock byte to indicate that the unlock slowpath has to be invoked. In the...

...+ * 2) Halting of the queue node CPU (in 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...

...+ * 2) Halting of the queue node CPU (in 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...

v5->v6: - Change the optimized 2-task contending code to make it fairer at the expense of a bit of performance. - Add a patch to support unfair queue spinlock for Xen. - Modify the PV qspinlock code to follow what was done in the PV ticketlock. - Add performance data for the unfair lock as well as the PV support code. v4->v5: - Move the optimized 2-task contending code to the

v5->v6: - Change the optimized 2-task contending code to make it fairer at the expense of a bit of performance. - Add a patch to support unfair queue spinlock for Xen. - Modify the PV qspinlock code to follow what was done in the PV ticketlock. - Add performance data for the unfair lock as well as the PV support code. v4->v5: - Move the optimized 2-task contending code to the

...+ * 2) Halting of the queue node CPU (in 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...

...+ * 2) Halting of the queue node CPU (in 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...

v6->v7: - Remove an atomic operation from the 2-task contending code - Shorten the names of some macros - Make the queue waiter to attempt to steal lock when unfair lock is enabled. - Remove lock holder kick from the PV code and fix a race condition - Run the unfair lock & PV code on overcommitted KVM guests to collect performance data. v5->v6: - Change the optimized

v6->v7: - Remove an atomic operation from the 2-task contending code - Shorten the names of some macros - Make the queue waiter to attempt to steal lock when unfair lock is enabled. - Remove lock holder kick from the PV code and fix a race condition - Run the unfair lock & PV code on overcommitted KVM guests to collect performance data. v5->v6: - Change the optimized

v7->v8: - Remove one unneeded atomic operation from the slowpath, thus improving performance. - Simplify some of the codes and add more comments. - Test for X86_FEATURE_HYPERVISOR CPU feature bit to enable/disable unfair lock. - Reduce unfair lock slowpath lock stealing frequency depending on its distance from the queue head. - Add performance data for IvyBridge-EX CPU.

v7->v8: - Remove one unneeded atomic operation from the slowpath, thus improving performance. - Simplify some of the codes and add more comments. - Test for X86_FEATURE_HYPERVISOR CPU feature bit to enable/disable unfair lock. - Reduce unfair lock slowpath lock stealing frequency depending on its distance from the queue head. - Add performance data for IvyBridge-EX CPU.

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

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

N.B. Sorry for the duplicate. This patch series were resent as the original one was rejected by the vger.kernel.org list server due to long header. There is no change in content. v7->v8: - Remove one unneeded atomic operation from the slowpath, thus improving performance. - Simplify some of the codes and add more comments. - Test for X86_FEATURE_HYPERVISOR CPU feature bit