This is (in my experience) a byproduct of good design, so changing the design wouldn't be a great idea.
Every time I've seen this happen it's in code that scales really well to lots of CPUs while having a lot of shared state, and the way it gets there is that it's using very fine-grained locks combined with smart load balancing. The idea is that the load balancer makes it improbable-but-not-impossible that two processors would ever want to touch the same state. And to achieve that, locks are scattered throughout, usually protecting tiny critical sections and tiny amounts of state.
Whenever I've gotten into that situation or found code that was in that situation, the code performed better than if it had coarser locks and better than if it used lock-free algorithms (because those usually carry their own baggage and "tax"). They performed better than the serial version of the code that had no locks.
So, the situation is: you've got code that performs great, but does in fact spend maybe ~2% of its time in the CAS to lock and unlock locks. So... you can get a tiny bit faster if you use a spinlock, because then unlocking isn't a CAS, and you run 1% faster.
Every time I've seen this happen it's in code that scales really well to lots of CPUs while having a lot of shared state, and the way it gets there is that it's using very fine-grained locks combined with smart load balancing. The idea is that the load balancer makes it improbable-but-not-impossible that two processors would ever want to touch the same state. And to achieve that, locks are scattered throughout, usually protecting tiny critical sections and tiny amounts of state.
Whenever I've gotten into that situation or found code that was in that situation, the code performed better than if it had coarser locks and better than if it used lock-free algorithms (because those usually carry their own baggage and "tax"). They performed better than the serial version of the code that had no locks.
So, the situation is: you've got code that performs great, but does in fact spend maybe ~2% of its time in the CAS to lock and unlock locks. So... you can get a tiny bit faster if you use a spinlock, because then unlocking isn't a CAS, and you run 1% faster.