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

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available cpufreq governors: ondemand, userspace, performance
current policy: frequency should be within 1.20 GHz and 2.00 GHz.
The governor "ondemand" may decide which speed to use
within this range.
current CPU frequency is 1.20 GHz.
Idle power states (C-States) with RHEL 6.x
Processor power use at idle is a crucial factor in determining power consumption of a server when there is no workload
to execute. Typically, when a processor does not have work to perform, the operating system places the processor in a
halt state signified as C1. Newer generation processors support deep C-states (C2-C6, where C6 is the deepest state),
allowing RHEL 6.x to take advantage of these states. The deeper the C-state, the more power consumption the
processor can save. Although C-states can significantly reduce power consumption, the drawback of going to a deeper
C-state is the latency associated with the time it takes for the processor to wake up from its idle state and resume
executing instructions. Information about the C-states for system processors is available in
/sys/devices/system/cpu/cpu*/cpuidle/state*.
Note
You can configure the server to not utilize the idle C-states by choosing the No
C-states setting in RBSU.
Additional RHEL 6.x power management features
RHEL 6.x provides a comprehensive set of features for managing the power usage of ProLiant servers.
The “Green IT” features introduced in RHEL 6.0
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and later offer the user a range of kernel and user-space features to
manage server power consumption. With the “tickless when idle” kernel feature, it is possible to reduce the number of
wakeups per seconds from 1024 to typically less than 30. For instance, in Figure 7, notice that the “Wakeups-from-idle
per second” is below 23. Additional tools are available to monitor the system power consumption. For example, using
the PowerTOP
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tool (powertop-1.11-4.el6.i686.rpm), you can identify processes that are most responsible for
waking a processor up from its idle state and thereby driving up power consumption. Reference the PowerTOP
documentation for further reading on what the output of PowerTOP represents, and for tips and tricks on how to best
tune the server for maximum power savings.
Figure 7 displays the PowerTOP V1.1 screen output on an idle 1P ProLiant DL360e Gen8 platform with Intel(R) Xeon(R)
CPU E5-2420 processor and 2 GB system memory running under RHEL 6.1. The average residency in the deepest
supported C-state
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is about 49ms. This value is due to the processor being awakened about only 23 per second times
from its idle state. The output listing is for a case where the IPMI service has been stopped on the server
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.
The latest PowerTOP v2.0
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— released in May, 2012 — provides many new features. For example, enhanced diagnostic
capabilities are available by using the perf subsystem of the Linux kernel. The user can monitor any of five different
views by selecting one of the tabs at the top of the screen: Overview, Idle stats, Frequency stats, Device stats, or
Tunables. Figure 8 displays the PowerTOP v2.0 screen output for the same system hardware used in the example of
Figure 7 running under RHEL 6.3.
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Red Hat Enterprise Linux 6: Green Computing Features
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An introduction to powerTOP: https://lesswatts.org/projects/powertop/
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ACPI C3 actually corresponds to hardware C6 state which is the deepest C-state supported by the processors on that platform
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Halting the IPMI driver results in a user losing the ability to remotely monitor the server. If the IPMI service is stopped to save power, it is possible to
resume the IPMI service with the service ipmi restart command.
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PowerTOP V2.0: https://01.org/powertop/blogs/ceferron/2012/powertop-v2.0-release