How to create a CPU spike with a bash command

Question

I use stress for this kind of thing, you can tell it how many cores to max out.. it allows for stressing memory and disk as well.

Example to stress 2 cores for 60 seconds

stress --cpu 2 --timeout 60

You can also do

dd if=/dev/zero of=/dev/null

To run more of those to put load on more cores, try to fork it:

fulload() { dd if=/dev/zero of=/dev/null | dd if=/dev/zero of=/dev/null | dd if=/dev/zero of=/dev/null | dd if=/dev/zero of=/dev/null & }; fulload; read; killall dd

Repeat the command in the curly brackets as many times as the number of threads you want to produce (here 4 threads). Simple enter hit will stop it (just make sure no other dd is running on this user or you kill it too).

I think this one is simpler. Open Terminal and type the following and press Enter.

yes > /dev/null &

To fully utilize modern CPUs, one line is not enough, you may need to repeat the command to exhaust all the CPU power.

To end all of this, simply put

killall yes

The idea was originally found here, although it was intended for Mac users, but this should work for *nix as well.

Although I'm late to the party, this post is among the top results in the google search "generate load in linux".

The result marked as solution could be used to generate a system load, i'm preferring to use sha1sum /dev/zero to impose a load on a cpu-core.

The idea is to calculate a hash sum from an infinite datastream (eg. /dev/zero, /dev/urandom, ...) this process will try to max out a cpu-core until the process is aborted. To generate a load for more cores, multiple commands can be piped together.

eg. generate a 2 core load: sha1sum /dev/zero | sha1sum /dev/zero

To load 3 cores for 5 seconds:

seq 3 | xargs -P0 -n1 timeout 5 yes > /dev/null

This results in high kernel (sys) load from the many write() system calls.

If you prefer mostly userland cpu load:

seq 3 | xargs -P0 -n1 timeout 5 md5sum /dev/zero

If you just want the load to continue until you press Ctrl-C:

seq 3 | xargs -P0 -n1 md5sum /dev/zero

One core (doesn't invoke external process):

while true; do true; done

Two cores:

while true; do /bin/true; done

The latter only makes both of mine go to ~50% though...

This one will make both go to 100%:

while true; do echo; done