"Replacing a sort algorithm in the FreeBSD kernel has improved its boot speed by a factor of 100 or more… and although it's aimed at a micro-VM, the gains should benefit everyone. MicroVMs are a hot area of technology R&D in the last half decade or so. The core idea is a re-invention of some of concepts and technology that IBM invented along with the hypervisor in the 1960s: designing OSes specifically to run as guests under another OS. This means building the OS specifically to run inside a VM, and to talk to resources provided by a specific hypervisor rather than to fake hardware." "When I started working on speeding up the boot process, the kernel took about 10 seconds to boot, so I have a kernel booting about 400x faster now than I did a few years ago." https://www.theregister.com/2023/08/29/freebsd_boots_in_25ms/