From: Waiman Long <waiman.l...@hp.com> This patch makes the necessary changes at the x86 architecture specific layer to enable the use of queue spinlock for x86-64. As x86-32 machines are typically not multi-socket. The benefit of queue spinlock may not be apparent. So queue spinlock is not enabled.
Currently, there is some incompatibilities between the para-virtualized spinlock code (which hard-codes the use of ticket spinlock) and the queue spinlock. Therefore, the use of queue spinlock is disabled when the para-virtualized spinlock is enabled. The arch/x86/include/asm/qspinlock.h header file includes some x86 specific optimization which will make the queue spinlock code perform better than the generic implementation. Cc: Ingo Molnar <mi...@redhat.com> Cc: David Vrabel <david.vra...@citrix.com> Cc: Oleg Nesterov <o...@redhat.com> Cc: Scott J Norton <scott.nor...@hp.com> Cc: Paolo Bonzini <paolo.bonz...@gmail.com> Cc: Douglas Hatch <doug.ha...@hp.com> Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com> Cc: Boris Ostrovsky <boris.ostrov...@oracle.com> Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: "H. Peter Anvin" <h...@zytor.com> Cc: Rik van Riel <r...@redhat.com> Cc: Raghavendra K T <raghavendra...@linux.vnet.ibm.com> Signed-off-by: Waiman Long <waiman.l...@hp.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Link: http://lkml.kernel.org/r/1421784755-21945-3-git-send-email-waiman.l...@hp.com --- arch/x86/Kconfig | 1 + arch/x86/include/asm/qspinlock.h | 20 ++++++++++++++++++++ arch/x86/include/asm/spinlock.h | 5 +++++ arch/x86/include/asm/spinlock_types.h | 4 ++++ 4 files changed, 30 insertions(+) create mode 100644 arch/x86/include/asm/qspinlock.h --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -125,6 +125,7 @@ config X86 select MODULES_USE_ELF_RELA if X86_64 select CLONE_BACKWARDS if X86_32 select ARCH_USE_BUILTIN_BSWAP + select ARCH_USE_QUEUE_SPINLOCK select ARCH_USE_QUEUE_RWLOCK select OLD_SIGSUSPEND3 if X86_32 || IA32_EMULATION select OLD_SIGACTION if X86_32 --- /dev/null +++ b/arch/x86/include/asm/qspinlock.h @@ -0,0 +1,20 @@ +#ifndef _ASM_X86_QSPINLOCK_H +#define _ASM_X86_QSPINLOCK_H + +#include <asm-generic/qspinlock_types.h> + +#define queue_spin_unlock queue_spin_unlock +/** + * queue_spin_unlock - release a queue spinlock + * @lock : Pointer to queue spinlock structure + * + * An smp_store_release() on the least-significant byte. + */ +static inline void queue_spin_unlock(struct qspinlock *lock) +{ + smp_store_release((u8 *)lock, 0); +} + +#include <asm-generic/qspinlock.h> + +#endif /* _ASM_X86_QSPINLOCK_H */ --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -42,6 +42,10 @@ extern struct static_key paravirt_ticketlocks_enabled; static __always_inline bool static_key_false(struct static_key *key); +#ifdef CONFIG_QUEUE_SPINLOCK +#include <asm/qspinlock.h> +#else + #ifdef CONFIG_PARAVIRT_SPINLOCKS static inline void __ticket_enter_slowpath(arch_spinlock_t *lock) @@ -196,6 +200,7 @@ static inline void arch_spin_unlock_wait cpu_relax(); } } +#endif /* CONFIG_QUEUE_SPINLOCK */ /* * Read-write spinlocks, allowing multiple readers --- a/arch/x86/include/asm/spinlock_types.h +++ b/arch/x86/include/asm/spinlock_types.h @@ -23,6 +23,9 @@ typedef u32 __ticketpair_t; #define TICKET_SHIFT (sizeof(__ticket_t) * 8) +#ifdef CONFIG_QUEUE_SPINLOCK +#include <asm-generic/qspinlock_types.h> +#else typedef struct arch_spinlock { union { __ticketpair_t head_tail; @@ -33,6 +36,7 @@ typedef struct arch_spinlock { } arch_spinlock_t; #define __ARCH_SPIN_LOCK_UNLOCKED { { 0 } } +#endif /* CONFIG_QUEUE_SPINLOCK */ #include <asm-generic/qrwlock_types.h> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
