Comment by vacuity
2 hours ago
The kernel, the memory manager and device drivers, the language runtimes for managed languages; would these not be written in "systems" languages? Essential complexity can only be rearranged, not removed. Nothing changes the fact that every interface between hardware and software needs to be bridged.
On a different note: why should the kernel even handle IPC or scheduling? Those take the basic capabilities of context switching, timer management, and memory management. Even "core functionality" can be a context switch (or a few) away; is a syscall not just a message to a system server? Only the most basic form of communication is necessary to delegate arbitrary functionality, so a true microkernel should only introduce that as an abstraction. Everything else either follows from the hardware or is left to the whims of software.
> The kernel, the memory manager and device drivers, the language runtimes for managed languages; would these not be written in "systems" languages?
The kernel and memory manager: probably yes, the device drivers: not necessarily, the language runtimes for managed languages: not necessarily.
> On a different note: why should the kernel even handle IPC or scheduling?
Because any other solution will quickly run into chicken-and-the-egg style problems.
> Those take the basic capabilities of context switching, timer management, and memory management.
Yes. But only one timer, the rest should be free to use by other applications.
> Even "core functionality" can be a context switch (or a few) away; is a syscall not just a message to a system server?
No. A syscall is usually defined as a call to a ring one level in from the one where you currently are. But lots of things that are syscalls right now do not necessarily have to be.
> Only the most basic form of communication is necessary to delegate arbitrary functionality, so a true microkernel should only introduce that as an abstraction.
Indeed. And they do.
> Everything else either follows from the hardware or is left to the whims of software.
A lot of the stuff that 'follows from the hardware' can be dealt with at the application level.