I didn't know about using alignment to avoid cache bouncing. Fascinating stuff

I love that this article includes a test program at the bottom to allow you to verify its claims.

Where do lock free algorithms fall in this analysis?

>Critical section under 100ns, low contention (2-4 threads): Spinlock. You’ll waste less time spinning than you would on a context switch.

If your sections are that short then you can use a hybrid mutex and never actually park. Unless you're wrong about how long things take, in which case you'll save yourself.

>alignas(64) in C++

    std::hardware_destructive_interference_size

Exists so you don't have to guess, although in practice it'll basically always be 64.

The code samples also don't obey the basic best practices for spinlocks for x86_64 or arm64. Spinlocks should perform a relaxed read in the loop, and only attempt a compare and set with acquire order if the first check shows the lock is unowned. This avoids hammering the CPU with cache coherency traffic.

Similarly the x86 PAUSE instruction isn't mentioned, even though it exist specifically to signal spin sections to the CPU.

Spinlocks outside the kernel are a bad idea in almost all cases, except dedicated nonpreemptable cases; use a hybrid mutex. Spinning for consumer threads can be done in specialty exclusive thread per core cases where you want to minimize wakeup costs, but that's not the same as a spinlock which would cause any contending thread to spin.