Nowadays, energy savings have become one of the most critical issues. In this paper, we propose an energy-efficient approach to scheduling periodic real-time tasks in the multicore context. Within a voltage/frequency domain (VFD), a simple static voltage/frequency scaling schedule (SimpleVS) is first introduced to select the utilization of the heaviest-loaded core as the shared operating frequency of this VFD. Next, the slack reallocation policy is proposed to further reclaim slack times while satisfying timeliness requirements. The slack reallocation strives to redistribute the slack times uniformly to the cores on the same VFD by appropriate job migrations. Experimental results show that compared with the static frequency schedule, our proposed policy can achieve energy savings up to 22 percent when the system is under-utilized.