How to create a CPU spike with a bash command

Question

I want to create a near 100% load on a Linux machine. It\'s quad core system and I want all cores going full speed. Ideally, the CPU load would last a designated amount of

Answer 1

To enhance dimba's answer and provide something more pluggable (because i needed something similar). I have written the following using the dd load-up concept :D

It will check current cores, and create that many dd threads. Start and End core load with Enter

#!/bin/bash

load_dd() {
    dd if=/dev/zero of=/dev/null
}

fulload() {
    unset LOAD_ME_UP_SCOTTY
    export cores="$(grep proc /proc/cpuinfo -c)"
    for i in $( seq 1 $( expr $cores - 1 ) )
      do
    export LOAD_ME_UP_SCOTTY="${LOAD_ME_UP_SCOTTY}$(echo 'load_dd | ')"
  done
        export LOAD_ME_UP_SCOTTY="${LOAD_ME_UP_SCOTTY}$(echo 'load_dd &')"
    eval ${LOAD_ME_UP_SCOTTY}
}

echo press return to begin and stop fullload of cores
  read
  fulload
  read
  killall -9 dd

Answer 2

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).

Answer 3

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

Answer 4

I would split the thing in 2 scripts :

infinite_loop.bash :

#!/bin/bash
while [ 1 ] ; do
    # Force some computation even if it is useless to actually work the CPU
    echo $((13**99)) 1>/dev/null 2>&1
done

cpu_spike.bash :

#!/bin/bash
# Either use environment variables for NUM_CPU and DURATION, or define them here
for i in `seq ${NUM_CPU}` : do
    # Put an infinite loop on each CPU
    infinite_loop.bash &
done

# Wait DURATION seconds then stop the loops and quit
sleep ${DURATION}
killall infinite_loop.bash

Answer 5

to increase load or consume CPU 100%

sha1sum /dev/zero &

then you can see CPU uses by typing command

top

to release the load

killall sha1sum

Answer 6

Just paste this bad boy into the SSH or console of any server running linux. You can kill the processes manually, but I just shutdown the server when I'm done, quicker.

Edit: I have updated this script to now have a timer feature so that there is no need to kill the processes.

read -p "Please enter the number of minutes for test >" MINTEST && [[ $MINTEST == ?(-)+([0-9]) ]]; NCPU="$(grep -c ^processor /proc/cpuinfo)";  ((endtime=$(date +%s) + ($MINTEST*60))); NCPU=$((NCPU-1)); for ((i=1; i<=$NCPU; i++)); do while (($(date +%s) < $endtime)); do : ; done & done