Quoted from Microkernels, Úlfar Erlingsson and Athanasios Kyparlis
"For some frequent operations, e.g. networking, the overhead of
context-switching was too great for an out-of-kernel implementation.
Thus the microkernels were not as efficient as originally thought."
I can't understand why for some frequent operations microkernels are
not efficient as originally thought. I thinking is why IPC cost on Mach
is very high. Its that true? Can anyone explain why that overhead
happen in Mach?