A security flaw has been found in the way that Intel processors from the last ten years handle kernel memory. The solution being implemented in the Windows and Linux kernels can vary from virtually no impact up to 20% or 30% for processes that involve a high number of kernel calls, such as writing to databases.
https://www.notebookcheck.net/Intel-hardware-flaw-will-cause-a-drop-in-performance-for-kernel-heavy-processes-once-fixed.276240.0.html