The ARTiS system is a real-time extension of the GNU/Linux scheduler dedicated to SMP (symmetric multiprocessors) systems. It allows to mix high performance computing and real-time. ARTiS exploits the SMP architecture to guarantee the preemption of a processor when the system has to schedule a real-time task. The implementation is available as a modification of the Linux kernel. The basic idea of ARTiS is to assign a selected set of processors to real-time operations. A migration mechanism of nonpreemptible tasks insures a latency level on these real-time processors. Furthermore, specific load-balancing strategies permit ARTiS to benefit from the full power of the SMP systems: the real-time reservation, while guaranteed, is not exclusive and does not imply a waste of resources