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HP ProLiant Server Power Management for Red Hat Enterprise Linux 6.x

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Figure 6: Power consumption with capping
ProLiant power management with RHEL 6.x
RHEL 6.x manages the power usage of ProLiant servers by adjusting the processor P-states when the HP Power
Regulator setting in RBSU is configured in OS Control mode. Typically within the Linux operating system, a governor
dictates the policy, while the actual P-state transition is accomplished by a suitable P-state driver. RHEL 6.x offers a
choice of governors, each implementing a different policy ranging from userspace, which enables the user space
program (cpuspeed) to directly configure the processor frequency, to performance, which selects the P-state
corresponding to the highest supported frequency. The default governor is the ondemand governor, which dynamically
adjusts the processor P-states to match the load on the server.
On Intel-based ProLiant platforms RHEL 6.x natively supports the Intel Demand Based Switching with Enhanced Intel
SpeedStep ® Technology. On AMD-based ProLiant platforms, RHEL 6.x supports AMD's PowerNow! technology. The
following table lists the P-state driver on Intel-based and AMD-based ProLiant G6, G7 or later platforms under OS
Control mode.
Processor Family
Intel ® Xeon ®
AMD Opteron ™
In order for RHEL 6.x to manage the power consumption of the processor, the firmware must communicate information
about the processor P-states and their associated frequencies to the OS. You can find this information in the file and
directories under /sys/devices/system/cpu. Included in the RHEL 6.x media is the cpufreq-util command
(installed via the cpufrequtils-007-5.el6.i686.rpm package) that provides information about the P-states of
the processors in the system in a user-friendly format. When used without arguments, cpufreq-info displays
information about all processor cores, including the P-state driver, the frequency range supported by the processor, the
available frequency steps (which are actually the P-states), the available and current governors, and the current
frequency. Example 1 shows how cpufreq-info also supports options to display information specific to a CPU.