Well, yes, you use 64 bit indices. As you are padding your indices to cacheline size anyway, you have bits to spare. You can also still use 32bit indices and l

Well, yes, you use 64 bit indices. As you are padding your indices to cacheline size anyway, you have bits to spare. You can also still use 32bit indices and let them wrap around naturally and make it work as long as your queue size is less than 2*31. Comparison just becomes a little bit trickier. That's how TCP works for example.