Benchmarking The Performance Impact Of Linux 5.15's Newest Protection Around Side Channel Attacks
Across a wide range of different real-world benchmarks that involve file operations and other kernel interactivity, there wasn't any noticeable difference with using ZERO_CALL_USED_REGS with the GCC 11 built kernel.
For I/O micro-benchmarks, it depended upon the particular test case but in some areas there was a minor hit to the performance.