With doing the comparison again of Linux 3.15 stable against Linux 3.16 Git, in a number of tests the performance was measurably slower with the newer code still under development. In a majority of the tests the performance was about the same, but in none of the cases was there any significant performance gains for this system.
All of the benchmark results, system details, logs, etc, are available via 1406227-KH-LINUX316K91. Worth noting is that Linux 3.16 is the first kernel to support the Intel P-State governor with this Devil's Canyon system so between the kernels there is a switch from ACPI CPUfreq with its ondemand governor as the default to Intel P-State performance being the new default scaling governor for this i7-4790K system.
The Apache performance seemed to be incredibly affected by whatever is currently going on with Linux 3.16.
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via Twitter and Google+ or contacted via MichaelLarabel.com.