How Linux’s Random Number Generator Got a 8450% Speed Boost in 5.18

Jason Donenfeld, the lead developer of WireGuard and maintainer of the Linux kernel’s random number generator, has recently overseen major improvements to the kernel’s entropy subsystem.

In Linux 5.17 the random code was updated to use BLAKE2s instead of SHA‑1; because BLAKE2s is faster and more secure, this simple change yielded roughly a 131 % speed increase.

Continuing the work in Linux 5.18, Donenfeld refactored the generator’s data structures from a global per‑NUMA layout to a per‑CPU layout, removing many locks on the fast path and eliminating the need to defer work to a queue.

The commit log for the random.git repository shows a flurry of contributions over two days that will be merged during the March 5.18 merge window.

An email from the developer highlighted that the new code improves the getrandom() system call. Benchmarks on an Intel Xeon E5‑2697 v2 (2.70 GHz, 112 GB RAM) using stress‑ng getrandom() demonstrated an astonishing 8450 % performance gain.

By switching to a per‑CPU structure, many locks disappear on multi‑core CPUs, which explains the dramatic speedup; the change also removes the previous requirement to defer operations to a work queue, further benefiting high‑core‑count machines and servers.