search for: splpar_rw_yield

...x80000000 | smp_processor_id() in the lock when it is + * held. Conveniently, we have a word in the paca that holds this + * value. + */ + +#if defined(CONFIG_PPC_SPLPAR) +/* We only yield to the hypervisor if we are in shared processor mode */ +void splpar_spin_yield(arch_spinlock_t *lock); +void splpar_rw_yield(arch_rwlock_t *lock); +#else /* SPLPAR */ +static inline void splpar_spin_yield(arch_spinlock_t *lock) {}; +static inline void splpar_rw_yield(arch_rwlock_t *lock) {}; +#endif + +static inline void spin_yield(arch_spinlock_t *lock) +{ + if (is_shared_processor()) + splpar_spin_yield(lock); + else...

This series adds an option to use queued spinlocks for powerpc, and makes it the default for the Book3S-64 subarch. This effort starts with the generic code so it's very simple but still very performant. There are optimisations that can be made to slowpaths, but I think it's better to attack those incrementally if/when we find things, and try to add the improvements to generic code as

v2 is updated to account for feedback from Will, Peter, and Waiman (thank you), and trims off a couple of RFC and unrelated patches. Thanks, Nick Nicholas Piggin (6): powerpc/powernv: must include hvcall.h to get PAPR defines powerpc/pseries: move some PAPR paravirt functions to their own file powerpc: move spinlock implementation to simple_spinlock powerpc/64s: implement queued

Updated with everybody's feedback (thanks all), and more performance results. What I've found is I might have been measuring the worst load point for the paravirt case, and by looking at a range of loads it's clear that queued spinlocks are overall better even on PV, doubly so when you look at the generally much improved worst case latencies. I have defaulted it to N even though

v3 is updated to use __pv_queued_spin_unlock, noticed by Waiman (thank you). Thanks, Nick Nicholas Piggin (6): powerpc/powernv: must include hvcall.h to get PAPR defines powerpc/pseries: move some PAPR paravirt functions to their own file powerpc: move spinlock implementation to simple_spinlock powerpc/64s: implement queued spinlocks and rwlocks powerpc/pseries: implement paravirt

v3 is updated to use __pv_queued_spin_unlock, noticed by Waiman (thank you). Thanks, Nick Nicholas Piggin (6): powerpc/powernv: must include hvcall.h to get PAPR defines powerpc/pseries: move some PAPR paravirt functions to their own file powerpc: move spinlock implementation to simple_spinlock powerpc/64s: implement queued spinlocks and rwlocks powerpc/pseries: implement paravirt

...- return false; - return !!(be32_to_cpu(lppaca_of(cpu).yield_count) & 1); -} -#endif - static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) { return lock.slock == 0; @@ -110,15 +97,6 @@ static inline void splpar_spin_yield(arch_spinlock_t *lock) {}; static inline void splpar_rw_yield(arch_rwlock_t *lock) {}; #endif -static inline bool is_shared_processor(void) -{ -#ifdef CONFIG_PPC_SPLPAR - return static_branch_unlikely(&shared_processor); -#else - return false; -#endif -} - static inline void spin_yield(arch_spinlock_t *lock) { if (is_shared_processor()) diff --git...

...yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count); if ((yield_count & 1) == 0) return; /* virtual cpu is currently running */ - rmb(); + smp_rmb(); if (lock->slock != lock_value) return; /* something has changed */ plpar_hcall_norets(H_CONFER, @@ -56,7 +56,7 @@ void splpar_rw_yield(arch_rwlock_t *rw) yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count); if ((yield_count & 1) == 0) return; /* virtual cpu is currently running */ - rmb(); + smp_rmb(); if (rw->lock != lock_value) return; /* something has changed */ plpar_hcall_norets(H_CONFER, -- 2...