The more people want to avoid fixing what’s really wrong with their server, the more they go out and find all the weird stuff that they can blame on something else (usually the product), or keep doing the same things that aren’t fixing the problem.
Spinlocks are one of those things. People will measure them, stare them, Google them, and have no idea what to make of them, all while being sure there’s something going on with them.
I don’t want to discount when spinlocks can actually cause a problem, but you shouldn’t treat every performance problem like it’s a bridge too far from what you can solve.
I have seen performance problems which actually did come down to spinlock issues. For every one of those, I’ve seen, oh, about 95-100 or so which came down to inefficient code.