memory_order::relaxed doesn't imply locking. Compilers on platforms where aligned access is atomic will generally implement relaxed reads and writes without loc

memory_order::relaxed doesn't imply locking. Compilers on platforms where aligned access is atomic will generally implement relaxed reads and writes without locking, barriers or other expensive operations. So x = x + 1 with relaxed semantics should be cheap and best effort, like you want.