The two knowledge base articles linked are also interesting:
Speculative Execution Exploit Performance Impacts - Describing the performance impacts to security patches for CVE-2017-5754 CVE-2017-5753 and CVE-2017-5715
Controlling the Performance Impact of Microcode and Security Patches for CVE-2017-5754 CVE-2017-5715 and CVE-2017-5753 using Red Hat Enterprise Linux Tunables
Speculative Execution Exploit Performance Impacts - Describing the performance impacts to security patches for CVE-2017-5754 CVE-2017-5753 and CVE-2017-5715
https://access.redhat.com/articles/3307751
Controlling the Performance Impact of Microcode and Security Patches for CVE-2017-5754 CVE-2017-5715 and CVE-2017-5753 using Red Hat Enterprise Linux Tunables
https://access.redhat.com/articles/3311301