Comment 11 for bug 455112

I forgot to mention one thing: In the Virtualbox forums there are some posters who wrote that installing the real time kernel (incl. headers) improved the performance of Virtualbox considerably. I tried, and it didn't make a difference for me. But it might be worth a try for others. (Note, however, that the real time kernel is a universe package - personally I don't want to have the kernel of all packages from the universe repos.) Nevertheless the positive experience by the above mentioned users suggests that the problem might be kernel related.