This is one of the reasons for MIT's exokernel design- most of what the operating system does gets pulled into userspace libraries by default, the same way it i

This is one of the reasons for MIT's exokernel design- most of what the operating system does gets pulled into userspace libraries by default, the same way it is with green threads, so you get the same kinds of benefits with file systems, networking, IPC, etc. I'm kind of disappointed most kernels that have added scheduler activations have dropped support because they didn't want to deal with both interfaces and weren't willing to drop the traditional one.