AIUI, in general, they don't. Avoiding the overhead of context switches is the research question in microkernels, and while there is progress being made, last I'd heard there wasn't a solution that didn't carry caveats. Now to be fair, sometimes those caveats are fine - ex. if you only write software in rust maybe you can get away with actually passing around memory without copies - but often they undermine the ability to run arbitrary software on general purpose hardware.
(If I'm behind and this has been solved in the general case, I'm happy to be corrected, but this was my undestanding of things as of a few years ago and I haven't heard about a breakthrough)
Redox-OS is based on this approach and is honestly extremely clean and easy to understand (when compared to MINIX which also adopts the same approach).
AIUI, in general, they don't. Avoiding the overhead of context switches is the research question in microkernels, and while there is progress being made, last I'd heard there wasn't a solution that didn't carry caveats. Now to be fair, sometimes those caveats are fine - ex. if you only write software in rust maybe you can get away with actually passing around memory without copies - but often they undermine the ability to run arbitrary software on general purpose hardware.
(If I'm behind and this has been solved in the general case, I'm happy to be corrected, but this was my undestanding of things as of a few years ago and I haven't heard about a breakthrough)