For any Intel Haswell Linux users with Iris Graphics thinking of switching to the Linux 3.19 kernel
when it's released in what might just be a few hours, be forewarned as testing this weekend revealed there looks to be an OpenGL performance regression attributed to this new kernel.
This weekend I was running some Linux 3.17 vs. 3.18 vs. 3.19 benchmarks on the ASUS Zenbook UX301LAA Haswell ultrabook now that it's no longer my main production system in having replaced it with the Broadwell X1 Carbon.
When comparing the past three kernel releases with this ASUS Zenbook with Core i7 4558U Haswell processor with Iris Graphics 5100, the Linux 3.19 performance clearly dropped. Tests were from Ubuntu 15.04 in its current development form with the Mesa 10.4.2 build. All of the Linux OpenGL benchmarks were run via the Phoronix Test Suite
In many of the tests, the Linux 3.19 performance for this system was clearly lower than the vanilla builds of Linux 3.17 and 3.18.
In some tests it's basically wiping out the Haswell Iris gains made in Linux 3.18.
You can find all of my initial test data for this issue from this OpenBenchmarking.org result file
. I'm still looking at the results from the LinuxBenchmarking.com
test farm to see if there's any regressions there for the Intel graphics kernel trackers or if I can reproduce this 3.19 regression on any other Intel ultrabooks/laptops around the Phoronix office.