Memory Barriers: a Hardware View for Software Hackers Paul E. McKenney Linux Technology Center IBM Beaverton paulmck@linux.vnet.ibm.com July 23, 2010 So what possessed CPU designers to cause them to inflict memory barriers on poor unsuspecting SMP software designers? In short, because reordering memory references al- lows much better performance, and so memory barri- ers are needed to force orderi