search for: pv_spinlocks_init

...tup_arch(void) > if (firmware_has_feature(FW_FEATURE_LPAR)) { > vpa_init(boot_cpuid); > > - if (lppaca_shared_proc(get_lppaca())) > + if (lppaca_shared_proc(get_lppaca())) { > static_branch_enable(&shared_processor); > +#ifdef CONFIG_PARAVIRT_SPINLOCKS > + pv_spinlocks_init(); > +#endif > + } We could avoid the ifdef with this I think? diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h index 434615f1d761..6ec72282888d 100644 --- a/arch/powerpc/include/asm/spinlock.h +++ b/arch/powerpc/include/asm/spinlock.h @@ -10,5 +10,9 @...

...tup_arch(void) > if (firmware_has_feature(FW_FEATURE_LPAR)) { > vpa_init(boot_cpuid); > > - if (lppaca_shared_proc(get_lppaca())) > + if (lppaca_shared_proc(get_lppaca())) { > static_branch_enable(&shared_processor); > +#ifdef CONFIG_PARAVIRT_SPINLOCKS > + pv_spinlocks_init(); > +#endif > + } We could avoid the ifdef with this I think? diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h index 434615f1d761..6ec72282888d 100644 --- a/arch/powerpc/include/asm/spinlock.h +++ b/arch/powerpc/include/asm/spinlock.h @@ -10,5 +10,9 @...

On Thu, Jul 09, 2020 at 12:06:13PM -0400, Waiman Long wrote: > We don't really need to do a pv_spinlocks_init() if pv_kick() isn't > supported. Waiman, if you cannot explain how not having kick is a sane thing, what are you saying here?

On Thu, Jul 09, 2020 at 12:06:13PM -0400, Waiman Long wrote: > We don't really need to do a pv_spinlocks_init() if pv_kick() isn't > supported. Waiman, if you cannot explain how not having kick is a sane thing, what are you saying here?

...are_has_feature(FW_FEATURE_LPAR)) { >> vpa_init(boot_cpuid); >> >> - if (lppaca_shared_proc(get_lppaca())) >> + if (lppaca_shared_proc(get_lppaca())) { >> static_branch_enable(&shared_processor); >> +#ifdef CONFIG_PARAVIRT_SPINLOCKS >> + pv_spinlocks_init(); >> +#endif >> + } > We could avoid the ifdef with this I think? > > diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h > index 434615f1d761..6ec72282888d 100644 > --- a/arch/powerpc/include/asm/spinlock.h > +++ b/arch/powerpc/inc...

On 7/23/20 10:00 AM, Peter Zijlstra wrote: > On Thu, Jul 09, 2020 at 12:06:13PM -0400, Waiman Long wrote: >> We don't really need to do a pv_spinlocks_init() if pv_kick() isn't >> supported. > Waiman, if you cannot explain how not having kick is a sane thing, what > are you saying here? > The current PPC paravirt spinlock code doesn't do any cpu kick. It does an equivalence of pv_wait by yielding the cpu to the lock holder only...

...f (*ptr != val) + return; + yield_to_any(); + /* + * We could pass in a CPU here if waiting in the queue and yield to + * the previous CPU in the queue. + */ +} + +static __always_inline void pv_kick(int cpu) +{ + prod_cpu(cpu); +} + +extern void __pv_init_lock_hash(void); + +static inline void pv_spinlocks_init(void) +{ + __pv_init_lock_hash(); +} + +#endif + #include <asm-generic/qspinlock.h> #endif /* _ASM_POWERPC_QSPINLOCK_H */ diff --git a/arch/powerpc/include/asm/qspinlock_paravirt.h b/arch/powerpc/include/asm/qspinlock_paravirt.h new file mode 100644 index 000000000000..6dbdb8a4f84f --- /d...

...f (*ptr != val) + return; + yield_to_any(); + /* + * We could pass in a CPU here if waiting in the queue and yield to + * the previous CPU in the queue. + */ +} + +static __always_inline void pv_kick(int cpu) +{ + prod_cpu(cpu); +} + +extern void __pv_init_lock_hash(void); + +static inline void pv_spinlocks_init(void) +{ + __pv_init_lock_hash(); +} + +#endif + #include <asm-generic/qspinlock.h> #endif /* _ASM_POWERPC_QSPINLOCK_H */ diff --git a/arch/powerpc/include/asm/qspinlock_paravirt.h b/arch/powerpc/include/asm/qspinlock_paravirt.h new file mode 100644 index 000000000000..6dbdb8a4f84f --- /d...

...f (*ptr != val) + return; + yield_to_any(); + /* + * We could pass in a CPU here if waiting in the queue and yield to + * the previous CPU in the queue. + */ +} + +static __always_inline void pv_kick(int cpu) +{ + prod_cpu(cpu); +} + +extern void __pv_init_lock_hash(void); + +static inline void pv_spinlocks_init(void) +{ + __pv_init_lock_hash(); +} + +#endif + #include <asm-generic/qspinlock.h> #endif /* _ASM_POWERPC_QSPINLOCK_H */ diff --git a/arch/powerpc/include/asm/qspinlock_paravirt.h b/arch/powerpc/include/asm/qspinlock_paravirt.h new file mode 100644 index 000000000000..750d1b5e0202 --- /d...

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

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

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

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