We present a high performance multicore I/O manager based on libuv for Glasgow Haskell Compiler (GHC). The new I/O manager is packaged as an ordinary Haskell package rather than baked into GHC's runtime system(GHC RTS), yet takes advantage of GHC RTS's comprehensive concurrent support, such as lightweight threads and safe/unsafe FFI options. The new I/O manager's performance is comparable with existing implementation, with greater stability under high load. It also can be easily extended to support all of libuv's callback-based APIs, allowing us to write a complete high performance I/O toolkit without spending time on dealing with OS differences or low-level I/O system calls.