Ubuntu Server 20.04 CPU Security Mitigation Performance Impact

Earlier this week I published new benchmarks looking at the desktop CPU security mitigation impact with Ubuntu 20.04. Here are similar tests done in looking at the server mitigation impact with the near-final Ubuntu 20.04 LTS while testing server workloads on Intel Xeon and AMD EPYC server platforms. Like the desktop tests, the mitigation impact with the out-of-the-box protections against Spectre, Meltdown, and friends is being compared to booting the same Ubuntu 20.04 release with "mitigations=off" for run-time disabling of the relevant mitigations on each platform.

This complementary set of tests is focused on looking at the current mitigation impact across both new and old server platforms while using the latest software stack with Ubuntu 20.04 "Focal Fossa" based on the Linux 5.4 kernel.

The tested server platforms for evaluating the CPU security mitigation impact on Intel with Ubuntu 20.04 included the Xeon E5-2687W v3 (Haswell), Xeon E3-1275 v6 (Kabylake), dual Xeon Gold 6138 (Skylake), and dual Xeon Gold 5220R (Cascade Lake Refresh) for a mix of CPUs across microarchitecture generations with varying levels of hardware mitigations. For an AMD reference point was an EPYC 7502P server.

Note that between the different servers are other hardware differences at play in providing a broad look at the mitigation impact rather than trying to serve as just a detailed CPU mitigation comparison, so while you may be able to see some broad trends, this article isn't intended as a server CPU comparison but just a high level look at the server performance mitigation impact on Ubuntu 20.04.

Tests on each server were Ubuntu Server 20.04 running various real-world server workloads and repeated after booting the same kernel with "mitigations=off" as a kernel option. Via the Phoronix Test Suite dozens of different benchmarks were carried out.