search for: pspin_threshold

...ther minor design flaw is that formerly first VCPU gets appended to the tail when it decides to queue; is the performance gain worth it? Thanks. --- 1: Pause Loop Exiting is almost certain to vmexit in that case: we default to 4096 TSC cycles on KVM, and pending loop is longer than 4 (4096/PSPIN_THRESHOLD). We would also vmexit if critical section was longer than 4k. 2: In this example, vpus 1 and 2 use the lock while 3 never gets there. VCPU: 1 2 3 lock() // we are the holder pend() // we have pending bit vmexit...

...ther minor design flaw is that formerly first VCPU gets appended to the tail when it decides to queue; is the performance gain worth it? Thanks. --- 1: Pause Loop Exiting is almost certain to vmexit in that case: we default to 4096 TSC cycles on KVM, and pending loop is longer than 4 (4096/PSPIN_THRESHOLD). We would also vmexit if critical section was longer than 4k. 2: In this example, vpus 1 and 2 use the lock while 3 never gets there. VCPU: 1 2 3 lock() // we are the holder pend() // we have pending bit vmexit...

...generic/qspinlock.h> diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 8deedcf..adedd75 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -60,12 +60,17 @@ * Check the pending bit spinning threshold only if PV qspinlock is enabled */ #define PSPIN_THRESHOLD (1 << 10) -#define MAX_NODES 4 +/* + * We need to double the number of per-cpu mcs_spinlock structures to hold + * additional fields specific to para-virtualization support. + */ #ifdef CONFIG_PARAVIRT_SPINLOCKS -#define pv_qspinlock_enabled() static_key_false(&paravirt_spinlocks_ena...

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

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

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

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 patches into smaller ones to ease review effort. - Fix a racing condition in the PV qspinlock code. v7->v8: - Remove one unneeded atomic operation from the slowpath, thus improving

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 patches into smaller ones to ease review effort. - Fix a racing condition in the PV qspinlock code. v7->v8: - Remove one unneeded atomic operation from the slowpath, thus improving