[ksk]

I have never heard of any project where virtual calls are the dominant factor in performance.

Are there any open source projects amongst your examples?

[nkurz]

It's not necessarily done with explicit 'virtual' calls in C++, but speed of dispatch is very important to interpreters for dynamic languages. Here's an improvement to Python where the same general type of fixes make a significant difference: http://bugs.python.org/issue4753

[ksk]

Good example.