Generate some CPU stress

If you need to generate 100% usage on all core:

openssl speed -multi $(grep -ci processor /proc/cpuinfo)

If you want to generate 100% usage on a single core:

yes > /dev/null &

The ampersand will create a background job for this command. If you have 8 core, this command will cause 12,5% overall usage. If you want to generate more usage, you can execute this command multiple times.