From Xen

Unikernels are famous for providing excellent performance in terms of boot times, throughput and memory consumption, to name a few metrics. However, they are infamous for making it hard and extremely time consuming to extract such performance, and for needing significant engineering effort in order to port applications to them.

Unikraft is a novel micro-library OS that (1) fully modularizes OS primitives so that it is easy to customize the unikernel and include only relevant components and (2) exposes a set of composable, performance-oriented APIs in order to make it easy for developers to obtain high performance.

One of Unikraft's explicit goals is to be close to POSIX compatible to be able to run standard, off-the-shelf applications. Our evaluation using such applications like nginx, SQLite, and Redis shows that running them on Unikraft results in a 1.7x-2.7x performance improvement compared to Linux guests. In addition, Unikraft images for these apps are around 1MB, require less than 10MB of RAM to run, and boot in around 1ms on top of the VMM time (total boot time 3ms-40ms).

Unikraft is an official Xen Project and Linux Foundation project, and its code is released under a BSD license.


  • Website [1].
  • Source code on Github [2]
  • Eurosys 2021 best paper award [3]