loadplay(1)

NAME
loadplay - CPU load player

SYNOPSIS
loadplay -h
loadplay [-i file] [-o file] command [...]

DESCRIPTION
The loadplay command replays a load recording created with loadrec(1). The command can either be powerd(8) or powerd++(8), compatibility with other tools has not been tested.

  OPTIONS
The following options are supported:

-h, --help
    Show usage and exit.

-i, --input file
    Read load recording from file instead of stdin.

-o, --output file
    Output statistics to file instead of stdout.

USAGE NOTES
The loadplay command injects libloadplay.so into command. This library simulates the load from the input and outputs load statistics.

  OUTPUT
The first line of output contains column headings, columns are separated by a single space.

The Following columns are present, columns containing %d occur for each core simulated:

time[s]
    The simulation progress in 0.001 second resolution.

cpu.%d.rec.freq[MHz]
    The recorded clock frequency, sampled at the end of the frame.

cpu.%d.rec.load[MHz]
    The recorded load in 0.1 MHz resolution.

cpu.%d.run.freq[MHz]
    The simulated clock frequency set by the host process, sampled at the end of the frame.

cpu.%d.run.load[MHz]
    The simulated load in 0.1 MHz resolution.

  SAMPLING
There is one sample for each recorded line. The duration of each frame depends on the recording, which defaults to 25 ms. At this sample rate loads are dominated by noise, so a gliding average should be applied to any load columns for further use, such as plotting.

IMPLEMENTATION NOTES
The injected libloadplay.so works by intercepting system function calls and substituting the host environment with the recording. To achieve this the following function calls are intercepted:

•   sysctl(3), sysctlnametomib(3), sysctlbyname(3)

•   daemon(3)

•   geteuid(2)

•   pidfile_open(3), pidfile_write(,) pidfile_close(3), pidfile_remove(3), pidfile_fileno(3)

  INITIALISATION
The sysctl family of functions is backed by a table that is initialised from the header of the load recording. If the heading is incomplete the setup routines print a message on stderr. All the following intercepted function calls will return failure, ensuring that the host process is unable to operate and terminates.

Like powerd++(8) and loadrec(1) loadplay is core agnostic. Meaning that any core may have a .freq and .freq_levels sysctl handle. Due to this flexibility load recordings may in part or wholly be fabricated to test artificial loads or systems and features that do not yet exist. E.g. it is possible to offer a .freq handle for each core or fabricate new .freq_levels.

  SIMULATION
If setup succeeds a simulation thread is started that reads the remaining input lines, simulates the load and updates the kern.cp_times entry in the thread safe sysctl table. For each frame a line of output with load statistics is produced.

Interaction with the host process happens solely through the sysctl table. The simulation reads the recorded loads and the current core frequencies to update kern.cp_times. The host process reads this data and adjusts the clock frequencies, which in turn affects the next frame.

  FINALISATION
After reading the last line of input the simulation thread sends a SIGINT to the process to cause it to terminate.

ENVIRONMENT

LOADPLAY_IN
    If set the file named is used for input instead of stdin. This only affects the input of loadplay, the host process is not affected.

LOADPLAY_OUT
    If set the file named is used for output instead of stdout. This only affects the output of loadplay, the host process is not affected.

LD_PRELOAD
    Used to inject libloadplay.so into the host process.

FILES

/usr/local/lib/libloadplay.so
    A library injected into command via the LD_PRELOAD environment variable.

EXAMPLES
Play a load recording with loadplay:

    > loadplay -i loads/freq_tracking.load powerd++
    time[s] cpu.0.rec.freq[MHz] cpu.0.rec.load[MHz] cpu.0.run.freq[MHz] cpu.0.run.load[MHz] cpu.1.rec.freq[MHz] cpu.1.rec.load[MHz] cpu.1.run.freq[MHz] cpu.1.run.load[MHz] cpu.2.rec.freq[MHz] cpu.2.rec.load[MHz] cpu.2.run.freq[MHz] cpu.2.run.load[MHz] cpu.3.rec.freq[MHz] cpu.3.rec.load[MHz] cpu.3.run.freq[MHz] cpu.3.run.load[MHz]
    0.025 1700 1700.0 1700 1700.0 1700 0.0 1700 0.0 1700 1700.0 1700 1700.0 1700 850.0 1700 850.0
    0.050 1700 1700.0 1700 1700.0 1700 1700.0 1700 1700.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0
    0.075 1700 566.7 1700 566.6 1700 1700.0 1700 1700.0 1700 0.0 1700 0.0 1700 566.7 1700 566.6
    0.100 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0
    0.125 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0
    0.150 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0
    0.175 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0
    0.200 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0
    0.225 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0
    0.250 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0
    0.275 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0 1700 0.0

Capture load and loadplay output simultaneously into two different files:

    > loadplay -i loads/freq_tracking.load -o load.csv powerd++ -f > load.out

Capture and display loadplay output:

    > loadplay -i loads/freq_tracking.load -o load.csv powerd++ -f | tee load.out
    power:  online, load:  527 MHz, cpu0.freq: 1700 MHz, wanted: 1405 MHz
    power:  online, load:  459 MHz, cpu0.freq: 1400 MHz, wanted: 1224 MHz
    power:  online, load:  502 MHz, cpu0.freq: 1200 MHz, wanted: 1338 MHz
    power:  online, load:  548 MHz, cpu0.freq: 1300 MHz, wanted: 1461 MHz
    power:  online, load:  704 MHz, cpu0.freq: 1500 MHz, wanted: 1877 MHz
    power:  online, load:  750 MHz, cpu0.freq: 1900 MHz, wanted: 2000 MHz
    power:  online, load:  805 MHz, cpu0.freq: 2000 MHz, wanted: 2146 MHz
    power:  online, load:  772 MHz, cpu0.freq: 2200 MHz, wanted: 2058 MHz
    power:  online, load:  574 MHz, cpu0.freq: 2000 MHz, wanted: 1530 MHz
    power:  online, load:  515 MHz, cpu0.freq: 1500 MHz, wanted: 1373 MHz

SEE ALSO
loadrec(1), powerd(8), powerd++(8), rtld(1), signal(3), tee(1)

AUTHORS
Implementation and manual by Dominic Fandrey <kami@freebsd.org>