renice comes with linux-tools
To play with it, install mathomatic to create a very demanding task
sudo yum install mathomatic mathomatic-tools
Generate a demanding task (calculate prime numbers in background task - notice the & symbol at the end)
matho-primes 1 9999999999 > p1.txt &
=> process id 1
matho-primes 1 9999999999 > p2.txt &
=> process id 2
sudo renice 20 <process id 1>
Check with top command the cpu load for each process
Applied to Rails app deployment to reduce the assets compilation cpu demand
Wait for “node” process to start, get its pid and execute
renice 20 node-pid