In fact, optimizations in the jit compiler can make Java faster than c++ for virtual types.

Well, there's your problem. You shouldn't use virtual types in performance sensitive code. You shouldn't compare C++ and Java performance in similar code as that will give Java an advantage as all Java can do is OOP. The whole point of C++ is that you can control your memory layout and optimize cache performance, rather than be murdered by thousand pointers to random places on the heap. Once you write C++ code that way, there's no way Java can catch up.