It always was a lot less important than proponents of monolithic kernels made it seem, there were two things that were left out of such discussions:
- paging is a very efficient way to copy a block of data from one process to another.
- the perceived speed of an interactive system has everything to do with responsiveness and very little with actual throughput. And responsiveness is associated with near real-time operation which happens to be something micro kernel based systems excel at.
With the advent of multi core CPUs monolithic kernels jumping in on doing slow shared memory concurrency kind of killed the idea of monolithic kernels to be fast. They can't be fast unless they do actor model, but it goes against the idea of monoliths, hence they can't do better than microkernels.
- paging is a very efficient way to copy a block of data from one process to another.
- the perceived speed of an interactive system has everything to do with responsiveness and very little with actual throughput. And responsiveness is associated with near real-time operation which happens to be something micro kernel based systems excel at.