“Performance is important in high performance computing. A performance impact on HPC use can be more than a simple annoyance. Because of the high investment cost and energy usage of HPC systems, a performance impact can have a signi cant effect on price per compute job. As we have discussed in the previous sections, the “page table isolation” workarounds have an overhead on entering and leaving the kernel. Luck happens that in HPC, computers spend most of their time in user space, doing computations. Low-latency networks such as In niband allow HPC systems to perform network communication without involving the kernel. Therefore during HPC computations, the Linux kernel might not be actively involved and the CPUs are running at full power.”