WebAssembly for Container Runtime: Are We There Yet?

To pursue more efficient software deployment with containers, WebAssembly (abbreviated as Wasm) has long been regarded as a promising alternative to native container runtime (such as Docker container) due to its features of secure memory sandbox, lightweight isolation, portability, and multi-language support. However, it remains unknown whether and how much Wasm indeed brings benefits for containerized software applications. To fill the knowledge gap, this paper presents the first measurement study on Wasm-based container runtime (i.e., Wasm container) by comparison with the Docker container and native standalone Wasm runtime for execution performance in terms of the startup, computation, system interface access, and resource consumption. Surprisingly, we find that the Wasm container does not achieve better performance versus the Docker container as expected and introduces significant overhead compared to the standalone Wasm runtime. Through comparison, we identify the main causes of performance degradation for Wasm containers. Some stem from the heavy containerization overhead similar to Docker containers, while others are inherently caused by Wasm VMs and the WASI interface. Our findings can help software developers, Wasm container developers and the Wasm community improve the efficiency of utilizing Wasm-based container runtime, ultimately optimizing software performance.