In 2015 clang & gcc have a more or less working devirtualization feature that eliminates the virtual overhead in a simple benchmark such as this. The compiler sees all classes and knows that a particular interface is implemented by only one class, so it simply elides the virtual table lookup. Add that features such as speculative devirtualization that can remove a surprisingly large number of virtual calls in an established code base such as Firefox: http://gcc.gnu.org/ml/gcc-patches/2013-09/msg00007.html

If C++ will exist in 10 years from now, I predict 'virtual' to be just yet another legacy keyword.