Tribblix: manual page: powertop.8

POWERTOP(8) Maintenance Commands and Procedures POWERTOP(8)

NAME

powertop - report and analyze events that affect power management

SYNOPSIS

powertop [-c processor_id] [-d count] [-t interval] [-v] [-h]

DESCRIPTION

PowerTOP is an observability tool that shows how effectively the
system is taking advantage of the CPU's power management features. By
running the tool on an otherwise idle system, the user can see for
how long the CPU is running at different power states. Ideally, an
unutilized (idle) system spends 100% of its time running at the
lowest power state, but because of background user and kernel
activity (random software periodically waking to poll status), idle
systems can consume more power than they should.

The tool analyzes system activity periodically and displays a summary
of how long the processor is executing at each supported power state.
It also displays the top activities responsible for causing the CPU
to wake up and use more energy. This report allows the user to
identify and diagnose problematic areas of the system and optimize
its power efficiency.

PowerTOP averages the amount of activity that is preventing the CPU
from entering a lower power state and presents it on the "Wakeups-
from-idle per second" field. This value represents the total number
of wake-ups divided by the current interval. Notice that not all
events are displayed on the screen at all times.

During execution, a user can force a refresh of the analysis by
pressing the R key. The interval time is restored to the default or
to a specified value. To quit the application, the user must press
the Q key.

If you are running as root (superuser) or in the Primary
Administrator role, the tool makes suggestions as how the system can
be improved from a power management perspective.

PowerTOP allows you to freeze each of its three subwindows, enabling
you to better analyze each subwindow's contents. When you have three
different DTrace scripts running at the same time, freezing
subwindows lowers CPU consumption. This feature is activated by
pressing the i, f, or e key while the tool running. Pressing one of
these keys freezes the idle, frequency, or event report,
respectively. Pressing it once more, unfreezes it. This feature is
most useful when invoked while the application being analyzed is
running.

PowerTOP runs on xVM(7) domains. However, the report for idle state
transitions might or might not be accurate as the physical CPU can be
shared by different virtual CPUs. Both wakeup count and event report
displays information regarding the current virtualized environment.

OPTIONS

The following options are supported:

-c [processor_id]

Specifies which CPU the tool should observe.

-d [count]

Dumps the results of count analysis of system activity to the
screen.

-h

Displays the command's usage.

-t [interval]

Specifies the interval, in seconds, at which the tool analyzes
the system. The possible values are between 1 and 100; the
default is 5 seconds.

-v

Switches to verbose mode, including noting firings of the kernel
cyclic subsystem in the event report.

EXAMPLES

Example 1: Setting the Interval

The following command sets the interval to two seconds.

% powertop -t 2

Example 2: Analyzing and Dumping System Activity

The following command analyzes and dumps system activity to the
standard output four times.

% powertop -d 4

Example 3: Reporting Cyclic Subsystem Activity

The following command reports cyclic subsystem activity.

% powertop -v

Example 4: Analyzing Activity on a Specific Processor

The following command runs PowerTOP and only displays data for CPU 3:

% powertop -c 3

EXIT STATUS

0

Successful operation.

1

An error occurred.

2

Incorrect usage.

ATTRIBUTES

USAGE

You must have DTrace privileges to run PowerTOP and root (superuser)
privileges or assume the Primary Administrator role for the tool to
suggest improvements to the system.

May 13, 2017 POWERTOP(8)