Maybe we should revisit microkernels

Summary

Microkernels If you want a complete description of what microkernels are then read the wikipedia article, but in one sentence it's a kernel where everything is in userspace except for scheduling, managing access to I/O devices, and IPC. Why microkernels? Better security, better reliability, better modularity. Better security because in a muicrokernel system a bug in one driver only gives an attacker access to that subsystem (or maybe even that driver), as opposed to having unlimited access to the whole system like is the case with mainstream operating systems today. Better relaibility becasue a crash in one subsystem only crashes that subsystem instead of crashing everything; if windows were a microkernel system then the crowdstrike bug would have just stopped some IT security staff from getting telemetry instead of being front page news. If linux were a microkernel system then the linux kernel team wouldn't be responsible for merging every driver for every hardware device, and wouldn't be responsible for vetting code that they would have to become experts on the inner workings of every chip supported by the linux kernel to properly vet. Why not microkernels? If microkernels are so much better why isn't every OS a microkernel OS? Lots of people were asking that question in the 80s and 90s, and a lot of them made microkernel OS's, and it turned out the answer was that the overhead was too high. The overhead was too high because computers in the 80s didn't have a way for a userspace process to directly access a particular hardware device. That means that every time eg: the filesystem wanted to do a disk read, it had to do a system call, which triggered a context switch, which triggered a whole bunch of expensive locking and memory copying. Why microkernels now? In a word: IOMMU. Virtually all PCs in use today have IOMMUs, they've been standard issue for about a decade. By using IOMMU and shared memory in the right way you can completely eliminate context switches from...