My VM is Lighter (and Safer) than your Container
đź“ś Abstract
Containers are in great demand because they are lightweight when compared to virtual machines. On the downside, containers offer weaker isolation than VMs, to the point where people run containers in virtual machines to achieve proper isolation. In this paper, we examine whether there is indeed a strict tradeoff between isolation (VMs) and efficiency (containers). We find that VMs can be as nimble as containers, as long as they are small and the toolstack is fast enough. We achieve lightweight VMs by using unikernels for specialized applications and with Tinyx, a tool that enables creating tailor-made, trimmed-down Linux virtual machines. By themselves, lightweight virtual machines are not enough to ensure good performance since the virtualization control plane (the toolstack) becomes the performance bottleneck. We present LightVM, a new virtualization solution based on Xen that is optimized to offer fast boot-times regardless of the number of active VMs. LightVM features a complete redesign of Xen’s control plane, transforming its centralized operation to a distributed one where interactions with the hypervisor are reduced to a minimum. LightVM can boot a VM in 2.3ms, comparable to fork/exec on Linux (1ms), and two orders of magnitude faster than Docker. LightVM can pack thousands of LightVM guests on modest hardware with memory and CPU usage comparable to that of processes.
✨ Summary
LightVM demonstrated that hypervisor-based virtualization could approach container-like startup latency and density by combining small guest images—especially unikernels and Tinyx-built Linux images—with a redesigned Xen control plane. The released implementation and its NoXS/Chaos components remain available as open source. (flosch.eu)
The paper’s influence is most clearly reflected in subsequent microVM and serverless work. The Firecracker paper explicitly identifies LightVM as an earlier project pursuing stronger isolation with lightweight virtualization, while Firecracker applies the same broad systems objective using a minimal KVM-based VMM; AWS reports that Firecracker was deployed in Lambda and Fargate at production scale. (css.csail.mit.edu) Later serverless and systems papers continue to cite LightVM when discussing low-overhead VM isolation, cold-start latency, and high-density execution environments. (usenix.org)