On a system running Oracle Linux 6.5 (compatible version only) or Oracle Linux 5.10 (compatible version and UEK2), the system CPUs cannot get deeper than the C1 state when the system is idle (sleep state). This can manifest itself in C-state thread wakeup performance latencies.
Workaround
Edit the /etc/grub.conf file to add the following kernel parameter:
intel_idle.max_cstate=0
This disables the default intel_idle driver and forces the kernel to use acpi_idle.
This issue does not exist for Oracle Linux 6.5 UEK3.