Retbleed Impact, Overall CPU Security Mitigation Cost For Intel Xeon E3 v5 Skylake

The default Retbleed mitigations on this Xeon E3 Skylake server can lead to longer build times now, even if keeping Hyper Threading enabled as all these tests were.

Database workloads are one of the common real-world areas impaired by these mitigations as well.

Kernel micro-benchmarks to no surprise show big impacts from Retbleed and other mitigations.

Across all of the benchmarks carried out in affected areas (see this result page), the default mitigated performance on this Xeon E3-1245 v5 Skylake CPU was at 80% the speed with the same software when booting the kernel with "mitigations=off" for run-time disabling these various CPU security fixes. When comparing the new Linux 5.19 default state to "retbleed=off" for showing just the Retbleed difference, the new Retbleed-mitigated default state in affected workloads is 89% the speed of the prior/unmitigated performance. Thankfully Retbleed doesn't affect the latest generations of Intel and AMD CPUs, but for older generations the performance cost continues adding up and may be time to consider upgrading for better performance and also much better power efficiency among other advantages.