[za_creature]

I'm not a systems guy, but you're probably right. A mutex requires an atomic variable which triggers the same cache coherency mechanism under contention.

What Justine probably meant was an apples to oranges comparison: in userspace, you can sometimes add constraints that allow for a faster algorithm whereas the cpu generally has to assume the worst.

That being said, if you look through this thread you'll find similar issues with OP's phrasing. A fine engineer / hacker, but too much 4chan troll in my book.