System information

146 System Analysis and Tuning Guide
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Suggestion: Enable SATA ALPM link power management via:
echo min_power > /sys/class/scsi_host/host0/link_power_management_policy
or press the S key.
The column shows the C-states. When working, the CPU is in state 0, when
resting it is in some state greater than 0, depending on which C-states are avail-
able and how deep the CPU is sleeping.
The column shows average time in milliseconds spent in the particular C-state.
The column shows the percentages of time spent in various C-states. For con-
siderable power savings during idle, the CPU should be in deeper C-states most
of the time. In addition, the longer the average time spent in these C-states, the
more power is saved.
The column shows the frequencies the processor and kernel driver support on
your system.
The column shows the amount of time the CPU cores stayed in different fre-
quencies during the measuring period.
Shows how often the CPU is awoken per second (number of interrupts). The
lower the number the better. The interval value is the powerTOP refresh in-
terval which can be controlled with the -t option. The default time to gather da-
ta is 5 seconds.
When running powerTOP on a laptop, this line displays the ACPI information
on how much power is currently being used and the estimated time until dis-
charge of the battery. On servers, this information is not available.
Shows what is causing the system to be more active than needed. powerTOP dis-
plays the top items causing your CPU to awake during the sampling period.
Suggestions on how to improve power usage for this machine.
For more information, refer to the powerTOP project page at http://
www.lesswatts.org/projects/powertop/. It also provides tips and tricks
and an informative FAQ section.
11.4 Special Tuning Options
The following sections highlight some of the most relevant settings that you might
want to touch.