The Radix Tree is a great data structure but it's really hard to use (as well as not actually being a radix tree).
The XArray is a redesign of the API to help more parts of the kernel use it as well as simplifying the parts of the kernel which are already using the radix tree.
To that end, I'd like to help people understand how I came up with the API design and how to use it.
Matthew works for Microsoft on the Linux kernel. He has a particular interest in persistent memory and storage.