Development of Linux kernel 5.9 kicked off about two months ago when Linus Torvalds announced the first Release Candidate (RC) milestone. After no less than eight RCs, the final release is out now and it should be coming to some of the most popular rolling release distributions in the next few weeks. As for the highlights of Linux 5.9, there’s support for the Unicore architecture, Zstandard (Zsdt) compression support for building x86 kernels, full support for asynchronous buffered read operations in the io_uring subsystem, as well as a new rescue= mount option and various performance improvements for the Btrfs file system.