Reduce the number of while-loop iterations (from two to one in the most common situation)
Signed-off-by: Arjan Koers <[email protected]> diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c index bab3b9e..995d479 100644 --- a/arch/x86/kernel/pvclock.c +++ b/arch/x86/kernel/pvclock.c @@ -126,7 +126,7 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) struct pvclock_shadow_time shadow; unsigned version; cycle_t ret, offset; - u64 last; + u64 last, save; do { version = pvclock_get_time_values(&shadow, src); @@ -158,8 +158,9 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) do { if (ret < last) return last; + save = last; last = atomic64_cmpxchg(&last_value, last, ret); - } while (unlikely(last != ret)); + } while (unlikely(last != save)); return ret; } -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
