https://arstechnica.com/gadgets/2020/03/power-management-is-hard-linux-patch-boosts-ice-lake-performance/

Back in December, Linux users were starting to notice that Ice Lake-equipped laptops were getting better framerates in powersave mode than in performance mode. This Tuesday, Intel developer Francisco Jerez released a patchset to address the conundrum. Jerez begins by noting the fact that if your system bottleneck is I/O, boosting CPU performance won't help—the CPU can't process more data if the I/O subsystem isn't providing it fast enough.

"In IO-bound scenarios (by definition) the throughput of the system doesn't improve with increasing CPU frequency beyond the threshold value at which the IO device becomes the bottleneck."