Read that aforelinked article for the complete Ubuntu Linux review of the i7-4790K compared to other Intel and AMD processors with a slew of benchmarks done using the Phoronix Test Suite and OpenBenchmarking.org so you can compare the data against your own Linux system in an easy and fully reproducible way.
For your viewing pleasure this weekend, I have some very basic overclocking Linux tests for the i7-4790K. With the ASRock Z97 Extreme6 motherboard I wasn't able to get a good overclock with the limited time I spent with the board prior to leaving for Russia, but will be back with more Devil's Canyon testing next month on Phoronix.
With the few minutes I spent toying with Devil's Canyon overclocking, 4.5GHz was the best stable overclock (compared to 4.0GHz base / 4.4GHz Turbo). I was able to boot up to 4.6GHz and then 4.65GHz, but ultimately these 4.6+ GHz overclocks weren't stable with the motherboard used and eventually under load would run into kernel issues with machine check errors.
Anyhow, for those wanting some basic results at 4.5GHz or just some new i7-4790K Linux reference points to compare to your own system, head on over to the data in 1406121-KH-INTELCORE47.