Over the "Red Hat Compatible Kernel" that Oracle ships that is the same as what's found in RHEL, CentOS, Scientific, etc, they also maintain their own Unbreakable Enterprise Kernel. The Oracle UEK isn't based on Linux 2.6.32 but a more recent release (in the case of Oracle Linux 6.5, the Linux 3.8 kernel) plus with various out-of-tree patches like SSD optimizations, NUMA optimizations, and other changes that they say offer more features and better performance.
With my last testing of Oracle Linux with its "UEK" kernel being of the EL 6.1 distributions in late 2011 and then a quick RHEL 6.2 benchmark in early 2012, I decided on Monday to run a quick kernel comparison atop the brand new release of Oracle Linux 6.5.
Various benchmarks were ran on Oracle Linux 6.4 x86_64 from the same Intel Core i7 3960X Extreme Edition system. The only change between test runs was using the Red Hat Compatible 2.6.32-431.el6.x86_64 kernel and then the Oracle Unbreakable Enterprise Kernel 3.8.13-16.2.1.el6uek.x86_64.
The benchmark results in full and all of the system details are hosted on OpenBenchmarking.org via 1312025-SO-ORACLELIN55. Check it out!
There were some performance changes between the enterprise kernels for disk workloads, but that was about it from the different workloads benchmarked on Monday -- see more results from the OpenBenchmarking.org link.