I worked on VMware's virtual machine monitor from 2000 until June. Overcoming customers' performance fears was a major impediment in the early years. Every frac

I worked on VMware's virtual machine monitor from 2000 until June. Overcoming customers' performance fears was a major impediment in the early years. Every fraction of a percent we gave up relative to native ruled out whole classes of applications. Nothing other than C would have been conceivable. Even C++ would have been wildly inappropriate, as it is for most kernels, because so much invisible code can hide behind a close-brace. The mapping from source to machine representation in C is relatively trivial, which is the source of all C's ups and downs. If you ever plan to count microseconds, cache misses, TLB misses, mispredicted branches, etc., you had better start with a toolchain whose machine-level output is grokable from the source.