The benefits and costs of writing a POSIX kernel in a high-level language


Cody Cutler, M. Frans Kaashoek, and Robert T. Morris, MIT CSAIL


This paper presents an evaluation of the use of a high-level language (HLL) with garbage collection to implement a monolithic POSIX-style kernel. The goal is to explore if it is reasonable to use an HLL instead of C for such kernels, by examining performance costs, implementation challenges, and programmability and safety benefits.

The paper contributes Biscuit, a kernel written in Go that implements enough of POSIX (virtual memory, mmap, TCP/IP sockets, a logging file system, poll, etc.) to execute significant applications. Biscuit makes lib- eral use of Go's HLL features (closures, channels, maps, interfaces, garbage collected heap allocation), which sub- jectively made programming easier. The most challenging puzzle was handling the possibility of running out of ker- nel heap memory; Biscuit benefited from the analyzability of Go source to address this challenge.

On a set of kernel-intensive benchmarks (including NG- INX and Redis) the fraction of kernel CPU time Biscuit spends on HLL features (primarily garbage collection and thread stack expansion checks) ranges up to 13%. The longest single GC-related pause suffered by NGINX was 115 microseconds; the longest observed sum of GC delays to a complete NGINX client request was 600 microsec- onds. In experiments comparing nearly identical system call, page fault, and context switch code paths written in Go and C, the Go version was 5% to 15% slower.

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@inproceedings {222627,
author = {Cody Cutler and M. Frans Kaashoek and Robert T. Morris},
title = {The benefits and costs of writing a {POSIX} kernel in a high-level language},
booktitle = {13th {USENIX} Symposium on Operating Systems Design and Implementation ({OSDI} 18)},
year = {2018},
isbn = {978-1-931971-47-8},
address = {Carlsbad, CA},
pages = {89--105},
url = {},
publisher = {{USENIX} Association},