A Look At The CPU Security Mitigation Costs Three Years After Spectre/Meltdown

First up are benchmarks using the new Firefox 84 web browser along with the rest of the updated software stack for early 2021...

Often seeing the most real-world pain from these default CPU security mitigations on Linux and other platforms is the web browser performance. With this up-to-date software stack and the latest CPU microcodes, all of the processors tested were seeing a measurable out-of-the-box performance hit from the default mitigations. Obviously the older CPUs without the hardware mitigations in place were most impacted.

As I have noted before, the new AMD Zen 3 CPUs in some instances do see higher overhead than the prior Zen 2 processors in switching to always-on STIBP.