On Alpha we have spinlocks that are 32b in size and an efficient cmpxchg64 implementation, so we qualify to make use of cmpxchg backed lockrefs. Select the ARCH_USE_CMPXCHG_LOCKREF Kconfig symbol and provide a trivial implementation of arch_spin_value_unlocked to satisfy the lockref code. Using Linus' simple testcase from http://article.gmane.org/gmane.linux.file-systems/77466 on a dual CPU ES47 system I see around an 8% gain: N Min Max Median Avg Stddev x 30 6194580 6295654 6272504 6272514 17694.232 + 30 6731164 6786334 6767982 6764274 13738.863 Difference at 95.0% confidence 491760 +/- 8188.17 7.83992% +/- 0.130541% (Student's t, pooled s = 15840.5) Signed-off-by: Matt Turner <mattst88@xxxxxxxxx> --- arch/alpha/Kconfig | 1 + arch/alpha/include/asm/spinlock.h | 5 +++++ 2 files changed, 6 insertions(+) diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig index bf9e9d3..f515a4d 100644 --- a/arch/alpha/Kconfig +++ b/arch/alpha/Kconfig @@ -3,6 +3,7 @@ config ALPHA default y select ARCH_MIGHT_HAVE_PC_PARPORT select ARCH_MIGHT_HAVE_PC_SERIO + select ARCH_USE_CMPXCHG_LOCKREF select HAVE_AOUT select HAVE_IDE select HAVE_OPROFILE diff --git a/arch/alpha/include/asm/spinlock.h b/arch/alpha/include/asm/spinlock.h index 37b570d..fed9c6f 100644 --- a/arch/alpha/include/asm/spinlock.h +++ b/arch/alpha/include/asm/spinlock.h @@ -16,6 +16,11 @@ #define arch_spin_unlock_wait(x) \ do { cpu_relax(); } while ((x)->lock) +static inline int arch_spin_value_unlocked(arch_spinlock_t lock) +{ + return lock.lock == 0; +} + static inline void arch_spin_unlock(arch_spinlock_t * lock) { mb(); -- 2.3.6 -- To unsubscribe from this list: send the line "unsubscribe linux-alpha" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
