Much work has been done on IPv6 standards and testbeds deployment. However, little is known about the performance of the real IPv6 Internet, especially from the perspective of end users. In this paper, we present a measurement study of current IPv6 performance conducted from CERNET¹. We study 585,680 packet-level traces with 133,340 million packets collected from 936 IPv4/IPv6 dual-stack Web servers located in 44 countries. We present a comprehensive performance comparison of IPv6 and IPv4, including connectivity, packet loss rate, roundtrip time, etc. Our measurement results show that IPv6 connections tend to have smaller RTTs than their IPv4 counterparts, but suffer higher packet loss rate at the same time. We also notice that tunneled paths do not show notable performance degradation compared with native paths. To our best knowledge, this paper is the first performance study based on both large scale TCP and ICMP traffic measurement in real IPv6 Internet.