Well, then you should probably start reading the publications about L3 and L4 of the last 7 years and you will find an in-detail analysis why your statement could be taken as offensive rant... ;-) There are pretty exact numbers of MACH's cache utilization and performance of IPC and the structural problems of the communication mechanism.
Well, I have done that (read papers). Cache utilization is very easy to fix. In fact when I did Mach VM overhauling (couple of years ago) it maybe took me one day to implement coloring. IPC issue was not discovered by l3/4 team, but rather was known issue for very long time. There are much older Utah and UW papers that address that. Anything else l3/4 team has up the sleeve? If I was to say that being tightly architectutre coupled is strange or that since l4 took almost everything out of the kernel, memory management could have been evicted as well (like eros microkernel does), then you may need to get offended. Otherwise, I don't see your point. L4 papers states that since there is no way to prove that Mach only causes 5% degradation statement is not valid. I say same logic applies to MkLinux vs. L4Linux. I am not trying to start am flame war. Nor do I claim that L4 is worthless. I simply want to see if there is a way to validate specific statement. If there is, that means that statement is valid, if there is not, then you tell me ... As simple as that. IS.