https://wccftech.com/intel-delivers-on-a-promise-linux-patch-improves-igpu-performance-per-watt-by-43/

Intel's open-source driver team has managed to improve the performance of Intel's iGPUs by 15% while increasing performance per watt by 43% at the same time (via Phoronix). The post was published by Francisco Jerez that leads the open-source driver team. Intel had previously promised to turn its attention to open-source drivers as well and it looks like its delivering on at least one deliverable.

In a single patch, the Intel developers were able to improve performance per watt by 43% (which is a very significant gain I might add) while increasing absolute performance by 15%. The patch was tested on an Intel Ice Lake iGPU but should be valid for pretty much all Intel iGPUs that support this p-state. That said, you might experience a different level of performance improvement based on the exact iGPU. Before we go any further, here is an extract of the relevant portion from the patch note: