With memory_order_acquire, you need a load-load barrier on the read side of RCU on ARM; with memory_order_consume, assuming an optimal implementation you do not

With memory_order_acquire, you need a load-load barrier on the read side of RCU on ARM; with memory_order_consume, assuming an optimal implementation you do not. On alpha you need a barrier either way. Hence consume improves performance on ARM (and other similar architectures), but doesn't help Alpha. edit: to be more explicit, you can't formally implement RCU with relaxed + a compiler barrier, although in practice it might work most of the time.