andrelucas/mkhot repository overview

⁠README for andrelucas/mkhot

This is a very simple CPU load generator, suitable for use when stress testing.

WARNING! This will, by design, cause very heavy CPU utilisation. That may cost you money, shorten the life of your hardware (or someone else's hardware), and otherwise affect running services.

⁠Running

$ docker run -t andrelucas/mkhot
Starting 4 load-generator thread(s), mode 'wait'

The -t option allows the program to be stopped with CTRL-C. Without it, you'll have to stop with docker stop.

With no options, mkhot will start one system thread per hardware thread (as reported via C++ std::thread::hardware_concurrency()) which will run a busy-wait loop. No special instructions, no contention, no system calls - just a spinning loop.

⁠Options

There are a few options:

$ docker run andrelucas/mkhot --help
Usage: mkhot [OPTIONS]
Where OPTIONS can be:
  --help                                Display this message
  -i [ --io-load ]                      Perform I/O in the load threads
  -n [ --no-fork ]                      Do not fork() on startup
  -h [ --override-hw-threads ] arg (=4) Override the number of hardware threads
  -t [ --threads-per-core ] arg (=1)    Threads per hardware core/thread

The -i option specifies an I/O operation should be run in the busy threads, again in a tight loop. This is simply a read of /dev/zero; we don't care about actual I/O, we just want to generate system calls.

The -h and -t options act as multipliers for the number of threads started. -h is defaulted to the number of hardware threads detected, and -t multiplies the number in -h in order to generate more load and contention. -t is especially useful for the I/O load option.

⁠nofork mode

When running under Docker we end up as PID 1 inside the container, and we don't get terminal signals. Normally, to avoid this, we'll fork() just before running the load threads in order to not be PID 1 any more, and so get CTRL-C etc. send to the process. This means mkhot can be stopped from the terminal instead of requiring action via e.g. docker stop.

This mode can be turned off with the -n option.