idlestat - A CPU power-state analysis tool.
- idlestat --trace -f|--trace-file filename -t|--duration seconds [OPTION] [command]
- idlestat --import -f|--trace-file filename [OPTION]
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
- 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.
- 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
- 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
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 it’s 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.
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".
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.
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 3050Then 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 25 0 C1E-IVB 30 0 C3-IVB 35 0 C6-IVB 40 0 C7-IVB 35 0
Finally, specify the wakeup power.
wakeup 210 6
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.
Currently, idlestat supports four report formats: default, boxless, csv, and comparison.
- 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.
- boxless: it's the default without - and | as table boundaries. This is more Braille terminal friendly than the default one
- 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.
- 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".
Assuming the idlestat binary is in your PATH.
- Run a trace, post-process the results (default is to show only C-state statistics):
- Run a trace, post-process the results and print all statistics:
- Run a trace with an external workload, post-process the results:
- Post-process a trace captured earlier:
- Run a trace, post-process the results and print all statistics into a file:
- Run a comparison trace, say, before and after making changes to system behavior
sudo idlestat --trace -f /tmp/changedstate -t 10
idlestat --import -f /tmp/changedstate -b /tmp/baseline -r comparison
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.
Copyright © 2015, Linaro Limited. License GPLv2: GNU GPL version 2 http://gnu.org/licenses/gpl.html.
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.
trace-cmd(1), trace-cmd-format(1), trace-cmd.dat(5)