Harmonizing Performance and Isolation in Microkernels with Efficient Intra-kernel Isolation and Communication

This paper presents UnderBridge, a redesign of traditional microkernel OSes to harmonize the tension between messaging performance and isolation. UnderBridge moves the OS components of a microkernel between user space and kernel space at runtime while enforcing consistent isolation. It retrofits Intel Memory Protection Key for Userspace (PKU) in kernel space to achieve such isolation efficiently and design a fast IPC mechanism across those OS components. Thanks to PKU's extremely low overhead, the inter-process communication (IPC) roundtrip cost in UnderBridge can be as low as 109 cycles. We have designed and implemented a new microkernel called ChCore based on UnderBridge and have also ported UnderBridge to three mainstream microkernels, i.e., seL4, Google Zircon, and Fiasco.OC. Evaluations show that UnderBridge speeds up the IPC by 3.0× compared with the state-of-the-art (e.g., SkyBridge) and improves the performance of IPC-intensive applications by up to 13.1× for the above three microkernels.