Fast Core Scheduling with Userspace Process Abstraction

We introduce uProcess, a pure userspace process abstraction that enables CPU cores to be rescheduled among applications at sub-microsecond timescale without trapping into the kernel. We achieve this by constructing a special privileged mode in userspace to achieve safe and efficient separation among uProcesses. The core idea is a careful combination of two emerging hardware features - userspace interrupts (Uintr) and memory protection keys (MPK). We materialize the uProcess abstraction by implementing Vessel, a userspace core scheduler that colocates latency-critical and best-effort applications with minimal switching overhead when they time-share CPU cores. Our experiment result shows that Vessel exhibits better overall performance and low latency when multiple applications are colocated.