AMD Patch To Use MWAIT Instead Of HALT For Certain Cases Yield A ~21% Improvement

As a Linux kernel change for benefiting AMD CPUs going back to Zen 1 and for matching behavior Intel has had in place since the Core 2 times, AMD submitted a patch for having the Linux kernel use the MWAIT instruction instead of HALT for when the system isn't using the CPU idle driver either for C-states being disabled by the BIOS or the driver not part of the kernel build. In turn this can lead to around a 21% improvement in exit latency on affected systems...