Keywords: perfbook_html

## C.7.2 AMD64

AMD64 is compatible with x86, and has recently updated its memory model [Adv07] to enforce the tighter ordering that actual implementations have provided for some time. The AMD64 implementation of the Linux `smp_mb()` primitive is `mfence`, `smp_rmb()` is `lfence`, and `smp_wmb()` is `sfence`. In theory, these might be relaxed, but any such relaxation must take SSE and 3DNOW instructions into account.