This paper presents Unikernel Linux (UKL), a path toward integrating unikernel optimization techniques in Linux, a general purpose operating system. UKL adds a configuration option to Linux allowing for a single, optimized process to link with the kernel directly, and run at supervisor privilege. This UKL process does not require application source code modification, only a re-link with our, slightly modified, Linux kernel and glibc. Unmodified applications show modest performance gains out of the box, and developers can further optimize applications for more significant gains (e.g. 26% throughput improvement for Redis). UKL retains support for co-running multiple user level processes capable of communicating with the UKL process using standard IPC. UKL preserves Linux's battle-tested codebase, community, and ecosystem of tools, applications, and hardware support. UKL runs both on bare-metal and virtual servers and supports multi-core execution. The changes to the Linux kernel are modest (1250 LOC).

The proliferation of multi-core, accelerator-enabled embedded systems has introduced new opportunities to consolidate real-time systems of increasing complexity. But the road to build confidence on the temporal behavior of co-running applications has presented formidable challenges. Most prominently, the main memory subsystem represents a performance bottleneck for both CPUs and accelerators. And industry-viable frameworks for full-system main memory management and performance analysis are past due. In this paper, we propose our Envelope-aWare Predictive model, or E-WarP for short. E-WarP is a methodology and technological framework to: (1) analyze the memory demand of applications following a profile-driven approach; (2) make realistic predictions on the temporal behavior of workload deployed on CPUs and accelerators; and (3) perform saturation-aware system consolidation. This work aims at providing the technological foundations as well as the theoretical grassroots for truly workload-aware analysis of real-time systems. We provide a full implementation of our techniques on a commercial platform (NXP S32V234) and make two key observations. First, we achieve, on average, a 6% overprediction on the runtime of bandwidth-regulated applications. Second, we experimentally validate that the calculated bounds hold if the main memory subsystem operates below saturation.

Unikernels have demonstrated enormous advantages over Linux in many important domains, causing some to propose that the days of Linux's dominance may be coming to an end. On the contrary, we believe that unikernels' advantages represent the next natural evolution for Linux, as it can adopt the best ideas from the unikernel approach and, along with its battle-tested codebase and large open source community, continue to dominate. In this paper, we posit that an upstreamable unikernel target is achievable from the Linux kernel, and, through an early Linux unikernel prototype, demonstrate that some simple changes can bring dramatic performance advantages.