Linux 6.2 Performance Option Helps Extend The Longevity Of Intel Skylake Era PCs

If you are wanting to maximize the usefulness of your Intel Skylake-era desktop/laptop/server currently relying on IBRS, with the stable kernel release of Linux 6.2 in February it's certainly worth considering the use of Call Depth Tracking via the new "retbleed=stuff" option if wanting to still maintain a secure system but recovering some of the performance lost otherwise to IBRS.

Across the 120+ benchmarks ran in total across a mix of synthetic and real-world workloads, booting the same Linux 6.2 kernel with retbleed=stuff increased the performance by 6%. However, even with this "faster" performance of Call Depth Tracking, the kernel was still running at just 84% of the unmitigated system performance by booting with mitigations=off. In any case at least retbleed=stuff is available now as an option for lessening the performance overhead at least until upgrading to a newer more secure, powerful, and power efficient system when able. We'll see if for a post-6.2 kernel release whether upstream Linux developers may end up defaulting to the Retbleed stuffing for Intel Skylake era processors.