Red Hat Enterprise has a page about it's green function, one might want to look into the use of the software quoted there, most of it has been tested in fedora before being included in red hat enterprise.
http://press.redhat.com/2010/05/25/red- ... e-linux-6/
The new “tickless” kernel, in combination with numerous user-mode enhancements, previewed in recent Fedora releases, offers the possibility to reduce the number of wakeups per second for modern CPUs from 1024 (the ‘tick’ in Red Hat Enterprise Linux 5) to typically less than 30. Using well-documented tools, users may be able to lower this even more by manual tuning. This reduction makes it possible to quiesce the processor more effectively when the application load is low, thereby reducing power consumption.
Active State Power Management (ASPM)
ASPM is designed to reduce the power consumption on inactive PCI Express lanes. This feature is expected to be available for systems with relatively new hardware and firmware support. The implementation introduces a very small delay when an inactive PCI lane returns to an active state, but our internal testing has shown that the additional latency is negligible, so we believe that it is a worthwhile tradeoff.
Aggressive Link Power Management (ALPM)
The idea behind ALPM for SATA AHCI (Advanced Host Controller Interface) is to move a SATA (Serial ATA) link to a very low power mode when no I/O is pending. The controller is designed to automatically return the link back into an active power state as soon as an I/O is pending again. Savings of between 0.5 and 1.5 watts per SATA port can be expected. There are three different settings for ALPM. The default for non-hotplugable ports is the medium power setting, which seems to provide a good compromise between power saving and performance. More aggressive power saving can cause noticeable performance degradation, so while suitable for some custom environments, is not enabled by default.
Relatime drive access optimization
Relatime drive access optimization is a new method for avoiding metadata write operations on normal filesystem read accesses. In order to achieve this, the access time information is cached instead of being written immediately to a disk. The net result is that the speed of many operations, such as booting, is improved. The feature also results in increased link idle times and reduced disk spin time. Depending on the disks being used and the specific use case, this feature has the potential to save up to 2W per disk.
Enhanced graphics power management
Enhanced graphics power management is another area where Red Hat works continually to improve the abilities of the graphics drivers provided by different vendors. Depending on the hardware, our drivers offer the ability to do LVDS (low voltage differential signaling) reclocking, GPU reclocking and even complete GPU powerdowns.
Combined with relatime drive access optimization, the operating system has been carefully audited, using new SystemTap scripts, to identify applications that were doing unnecessary disk and network I/O. This iterative process is used to continuously optimize applications, reducing their I/O footprints and power demands.
Starting with Fedora 11, a new system service called Tuned was introduced. Briefly, this is a dynamic adaptive system daemon with a flexible plugin mechanism. As of today, monitoring and tuning plugins exist for ATA (Advanced Technology Attachment) hard-disk subsystems and Ethernet devices, and are available to measure CPU latency using PM-QOS (Power Management – Quality of Service). For Red Hat Enterprise Linux 6, this feature is expected to be combined with the ktune service, which provides an easier mechanism for static system tuning. We also anticipate that user definable and predefined profiles for various use cases, with an easy to use CLI, will be added.
Battery Life ToolKit (BLTK)
To analyze the impact of power management changes and enhancements, Red Hat engineers use a framework to generate reproducible workloads. The BLTK provides this, with several real life scenarios, ranging from a simple workload using a Firefox page reader to a more complex workload using OpenOffice writer and spreadsheet applications.