Hi Peng, There're 2 versions of ixgbe_tx_queue_release_mbufs. One in ixgbe_rxtx.c, the other is in ixgbe_rxtx_vec.c. What you shown is the one in ixgbe_rxtx.c. You can find the one in ixgbe_rxtx_vec.c already has the sanity check for reference count. Thanks.