alalo

The 4% come from a application-level benchmark that was popular back then. This is about ARM9/armv5 too, which is not suited for any multi-user OS as address spaces switching is very expensive compared to today's architectures (armv6+) due to the needed cache flushing on every address space switch. This has nothing to do with L4 variants, this is an architectural issue.

ARM9's cache architecture is not suited for frequent address space switches due to the requirement to flush caches on every switch. All multi-user OSes suffer there it's just more accentuated on microkernels.

That's why the system is called L4Re nowadays, and the microkernel specifically "L4Re microkernel". Fiasco however remains the nerd version, let alone to have discussions as those here.