idlestat(1)

A CPU power-state analysis tool.

Section 1 idlestat bookworm source

Description

idlestat

NAME

idlestat - A CPU power-state analysis tool.

SYNOPSIS

Trace mode:

idlestat --trace -f|--trace-file filename -t|--duration seconds [OPTION] [command]

Reporting mode:

idlestat --import -f|--trace-file filename [OPTION]

DESCRIPTION

Idlestat comes with two modes: in trace mode, it measures how long the CPUs have been in the different idle and operating states, analyzes captured events, logs them, and generates a report; in reporting mode, it reads the trace file, analyzes logged events in the trace file, and generates a report. A report by idlestat shows statistics of power related states. Currently, it handles P-states, C-states, and IRQ states.

For trace mode, idlestat relies on the kernel’s FTRACE function to monitor and capture C-state and P-state transitions of CPUs over a time interval. That is, for trace mode, idlestat needs a kernel with FTRACE related configurations enabled. And since it uses FTRACE, root privilege is needed when running in trace mode. Idlestat extracts the following information from trace file:

	Times when CPUs entered and exited a certain C-state
	Times when CPUs entered and exited a certain P-state
	Raised IRQs

Following a successful run, idlestat calculates and reports the following information:

	-		Total, average, minimum, and maximum time spent in each C-state, per-CPU.
	-		Total, average, minimum, and maximum time spent in each P-state, per-CPU.
	-		Total, average, minimum, and maximum time during which all CPUs in a cluster were in a "shallowest" (closest to running) state of all the constituent CPUs.
	-		Number of times a certain IRQ caused a CPU to exit idle state, per-CPU and per-IRQ

OPTIONS

--trace

Run idlestat in trace mode, as noted above, root privilege is needed. Used with -t and -f to specify running duration and trace output filename, respectively.

--import

Run idlestat in reporting mode. Used with -f to specify the trace file to import.

-f, --trace-file filename

Specify the trace filename to generate (for --trace) or read (for --import).

-t, --duration seconds

Time to capture in seconds

[command]

If the command argument is given, idlestat will fork a child to run the command so that you can capture related states when the command is running. Note that if the running command does not terminate before the time specified by -t, idlestat will send a SIGTERM to the child process to ask it to terminate. If the command to run lasts less than the time specified by -t, idlestat will terminate after the command finished.

When there is no command, idlestat does trace capture and other works dutifully.

-b, --baseline_trace baseline_filename

Specify baseline filename for trace comparison. See COMPARISON and EXAMPLES for more information.

-c, --idle

Show idle, C-state in ACPI term, statistics. This is the default mode if neither -w nor -p is set. Note that -w, -c, and -p are not exclusive, that is, you can choose any combination of the three.

-e, --energy-model-file energy_model

Specify energy model file. See ENERGY MODEL for the description of the energy file format.

-h, --help, -?

Print simple help messages.

-o, --output-file filename

Specify the file name to output statistics. If not specified, statistics are printed to stdout.

-p, --frequency

Show cpufreq (or say P-state) statistics.

-r, --report-format

Specify the report format. Valid types are: default, boxless, csv, and comparison.

-v, --verbose

Specify the verbosity level. This option could be specified multiple times. Each copy of the option increases verbosity level by one, currently the highest verbosity level used for any message is 2.

-w, --wakeup

Show wakeup statistics.

-B, --boxless

Set the report format to boxless

-C, --csv

Set the report format to comma separated values (CSV)

-I, --poll-interval

Set kernel polling interval, which is used to determine if itâs time move data from kernel FTRACE buffer to other places.

-S, --buffer-size

Set the kernel FTRACE buffer size to use.

-V, --version

Show idlestat version information and exit.

COMPARISON

The comparison report is used to compare changes between the active trace (specified by -f,--trace-file) and the baseline trace. It becomes active by providing a baseline trace (-b,--baseline_trace) and specifying the comparison report style with "-r comparison".

ENERGY MODEL

The following describes the format of idlestat energy model files (using the included energy_model file as an example):

Lines starting with # or which are blank are ignored.

First, specify how many clusters there are.

clusters 1

For each cluster (named clusterA, clusterB, etc.) specify how many cap states and C states there are. Idlestat will check that the correct number of clusters are provided.

#
clusterA: 16 cap states 5 C states

Then specify the name, cluster power and core power for each P-state (idlestat will check if there are the correct number of P-states provided) in the cluster.

P-states:
# speed, cluster power, core power

2901	6200	3200
2900	6190	3190
2800	6180	3180
2700	6170	3170
2500	6160	3160
2400	6150	3150
2300	6140	3140
2200	6130	3130
2000	6120	3120
1900	6110	3110
1800	6100	3100
1700	6090	3090
1600	6080	3080
1400	6070	3070
1300	6060	3060
1200	6050	3050

Then specify the name, cluster power and core power for each C-state (idlestat will check if there are the correct number of C-states provided) in the cluster.

C-states:

C1-IVB

C1E-IVB

C3-IVB

C6-IVB

C7-IVB

			25	0
			30	0
			35	0
			40	0
			35	0

Finally, specify the wakeup power.

wakeup

210

Repeat for each cluster.

TRACE FILE FORMAT

Idlestat has its own trace file format, which is based on ftrace’s format (see Documentation/trace/ftrace.txt in kernel source). Besides standard FTRACE entries, idlestat adds CPU topology, C-state information, and some artificial P-State entries. Idlestat can also import standard FTRACE format and "trace-cmd report" format. Note that since there is no CPU topology and C-state information in FTRACE or trace-cmd trace files, they should be used on the machines those traces are captured.

REPORT FORMATS

Currently, idlestat supports four report formats: default, boxless, csv, and comparison.

	1.		default: show C-state, P-State, and IRQ state statistics tables if corresponding -c, -p, and -w command line options are set. Tables come with - and \| as boundaries.
	2.		boxless: it’s the default without - and \| as table boundaries. This is more Braille terminal friendly than the default one
	3.		csv: comma separated values. This is easier to process with scripting languages, such as awk and perl. Also it’s easier to be processed with spreadsheet software.
	4.		comparison: This is similar to default report style, except that it displays changes in active trace compared to the baseline trace. It becomes active by providing a baseline trace (--baseline) and specifying the comparison report style with "-r comparison".

EXAMPLES

Assuming the idlestat binary is in your PATH.

Run a trace, post-process the results (default is to show only C-state statistics):

sudo idlestat --trace -f /tmp/mytrace -t 10

Run a trace, post-process the results and print all statistics:

sudo idlestat --trace -f /tmp/mytrace -t 10 -p -c -w

Run a trace with an external workload, post-process the results:

sudo idlestat --trace -f /tmp/mytrace -t 10 -p -c -w -- rt-app /tmp/mp3.json

Post-process a trace captured earlier:

idlestat --import -f /tmp/mytrace

Run a trace, post-process the results and print all statistics into a file:

sudo idlestat --trace -f /tmp/mytrace -t 10 -p -c -w -o /tmp/myreport

Run a comparison trace, say, before and after making changes to system behavior

sudo idlestat --trace -f /tmp/baseline -t 10
sudo idlestat --trace -f /tmp/changedstate -t 10
idlestat --import -f /tmp/changedstate -b /tmp/baseline -r comparison

LIMITATIONS

During the acquisition, idlestat tries to stay quiescent to prevent disturbing the traces. For this reason the traces are buffered in a fixed buffer size. If the duration of the acquisition produces more traces than what the buffer is capable to store, that will result in a truncated result.

AUTHOR

Started by Daniel Lezcano with contributions from others. See the git log of the source code (https://git.linaro.org/power/idlestat.git) for all the contributors.

REPORTING BUGS

Send mail to sched-tools@linaro.org. Or, submit bugs at https://bugs.linaro.org/enter_bug.cgi under Product "power management", Component "idlestat".

COPYRIGHT

This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Or, say, there is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.