How can I produce high CPU load on a Linux server?

Question

I'm currently in the process of debugging a Cacti installation and want to create CPU load to debug my CPU utilization graphs.

I tried to simply run cat /dev/zero > /dev/null, which works great, but only utilizes 1 core:

Could someone suggest a better approach maybe?

Related: How can I produce high CPU load on Windows?

Answer 1

Try stress It's pretty much an equivalent of the Windows consume.exe:

oliver$ ./stress --cpu 3
stress: info: [18472] dispatching hogs: 3 cpu, 0 io, 0 vm, 0 hdd

Answer 2

I made a simple python script which does the same. You can control the number of cpu cores you want to load. The good thing about this is that it won't consume any other resource besides the cpu. (I think mark johnson's idea would consume a lot of I/O resources, which is undesired here.)

from multiprocessing import Pool

def f(x):
    # Put any cpu (only) consuming operation here. I have given 1 below -
    while True:
        x * x

# decide how many cpus you need to load with.
no_of_cpu_to_be_consumed = 3

p = Pool(processes=no_of_cpu_to_be_consumed)
p.map(f, range(no_of_cpu_to_be_consumed))

Just run this script from the terminal $ python temp1.py. You need to kill the script when you are done.

Here, is my cpu consumption output when I load 3 of my cpu cores.

Answer 3

Compile the Linux kernel or GCC from source with:

make -j N

Where N is the number or cores + 1. You can do it in a loop in a bash script (make clean; make -j N) if you want a continuous load.

Answer 4

This will load your four cores at 100%:

for i in 1 2 3 4; do while : ; do : ; done & ; done

Edit: How it works is quite simple, it starts four endless loops. Each of them is repeating the null instruction (:). Each loop is able to load a CPU core at 100%.

Answer 5

I usually take the cpuburn suite:

sudo apt-get install cpuburn
for i in {1..4}; do burnK7 & done

Replace 4 with the number of cores / HT-threads you have or want to stress.

Note: This stresses as much chip area as possible at the same time, it's programmed to generate maximum power dissipation. I had to write this post a second time, somehow my machine didn't like it :-(

You could also do cpuburn in sequences:

burnP6 & burnP6 & burnP6 & burnP6 & 
[1] 28520
[2] 28521
[3] 28522
[4] 28523

And when you want to stop them:

killall burnP6

You could also multiply burnP6 & to match the number of CPU cores on your system.

Answer 6

A simple command line does it too:

x="x" ; while : ; do x=$x$x ; echo -n "." ; done

Answer 7

You can run that command as many times as you want, and it will take up a different core each time:

$ CORES=1
$ for i in `seq 1 $CORES`; do cat /dev/zero > /dev/null &
> done
[1] 8388