Michael Larabel from Phoronix has run three Intel Xeon and two AMD EPYC systems through a battery of testing including a virtual machine to determine the performance cost that security mitigation patches such as Spectre, Meltdown, and Foreshadow have had on the platforms under Linux. The Linux 4.19-rc1 kernel was used in the testing, but they didn't disable Hyper-Threading / SMT support on the Intel chips as some public cloud providers adjust their scheduler to block threads from going across users. Doing so would lower performance even more. An overview chart and more information gleaned from the article can be found here. Thanks TurboGLH ! After testing all of the configurations on the stock Linux 4.19-rc1 kernel, tests were repeated after using the various run-time switches for disabling mitigations. All of the systems were tested with Ubuntu 18.04.1 LTS x86_64 with the Linux 4.19-rc1 kernel via the Ubuntu Mainline Kernel PPA, up-to-date microcodes/BIOS, GCC 7.3, and the EXT4 file-system.