Benchmarking The Intel Performance Change With Linux FSGSBASE Support
In some scientific workloads like CP2K, the performance was slightly better but still behind the unmitigated kernel.
At this time there wasn't much change out of the Java workloads as Java likely still needs to be updated with the FSGSBASE support for further benefit.
For most purely CPU user-space workloads, don't expect much in the way of performance changes.