Ubuntu 25.10’s transition to using Rust Coreutils in place of GNU Coreutils has uncovered a few performance issues so far with the Rust version being slower than the C-based GNU Coreutils. Fortunately there still are a few weeks to go until Ubuntu 25.10 releases as stable and upstream developers are working to address these performance gaps.
The recent Rust Coreutils 0.2.2 release with faster base64 turned out to stem from an Ubuntu developer pointing out the performance disparity. That base64 issue was raised in this bug report and quickly resolved in Rust Coreutils to end up providing even better performance than GNU Coreutils’ base64.
A bug report opened last week is cksum being up to 17x slower than GNU for some large files. A test case was provided for the cksum utility being so slow. The uutils lead developer Sylvestre Ledru was able to reproduce the performance issue and is currently working through some patches to improve the performance of cksum.
There was also a bug report raised for Rust Coreutils’ sort command not finishing the sort process for large one line files. The real-world use-case may be limited but the issue is being tracked down too as being another “performance” problem.
We’ll see what more performance issues with Rust Coreutils are discovered and addressed prior to the Ubuntu 25.10 release in October. Most important is getting these significant underlying changes being made to Ubuntu in good shape ahead of the all important Ubuntu 26.04 LTS release in April.
