Attracted by the enormous potentials of Graphics Processing Units (GPUs), an array of efforts has surged to deploy Breadth-First Search (BFS) on GPUs, which, however, often exploits the static mechanisms to address the challenges that are dynamic in nature. Such a mismatch prevents us from achieving the optimal performance for offloading graph traversal on GPUs. To this end, we propose XBFS framework that leverages the runtime optimizations atop GPUs to cope with the nondeterministic characteristics of BFS providing several novel techniques design.