Spectre/Meltdown Performance Impact Across Eight Linux Distributions

While nearly all Linux distributions have been mitigated against the Spectre and Meltdown CPU vulnerabilities for over one year, the performance ahead associated with these speculative execution vulnerabilities can vary. This is especially more so with the enterprise Linux distributions that are generally shipping on older kernel branches prior to where the initial kernel support was mainlined. With recent kernel releases we've also seen varying optimizations and other changes around the Spectre/Meltdown/L1TF mitigations. So for those wondering about the varying impact, here are some side-by-side benchmarks.

For those curious how the Spectre/Meltdown mitigation impact can vary between Linux distributions, on the same system I tested eight different Linux distributions while comparing the default mitigation costs to that of disabling all possible Spectre/Meltdown/L1TF mitigations that can be run-time disabled. The same up-to-date microcode of the BIOS/firmware was maintained the same with primarily going to the extents an end-user would if wanting to try to recover the performance costs involved with Spectre/Meltdown on each of the tested Linux distributions.

The Linux distributions tested were:

- CentOS 7
- Red Hat Enterprise Linux 8 Beta
- Fedora 29
- Manjaro 18.0.3
- openSUSE 15.0
- Ubuntu 18.04 LTS
- Ubuntu 18.10
- Clear Linux 28230

Each OS was tested "out of the box" except for when disabling the relevant Spectre/Meltdown mitigations. The same Intel Core i9 7960X system with MSI X299 SLI PLUS, 16GB RAM, 256GB Intel SSD, and Radeon RX 560 graphics was used for testing.

All of these benchmarks were facilitated using the Phoronix Test Suite.