CPU Tool is a utility which can be used to control the CPU utilization of
almost any process. It can take control of processes which are already
running and can also start a process on startup. It can limit CPU usage 
depending on both current system load and CPU utilization.


Its extremely easy to use:

1. Limit rsync to only use 50% CPU
cputool -c 50 -- rsync -a /home/ /mnt/backup/home

2. Limit rsync to only use 50% CPU and only run when load is below 3.0
cputool -c 50 -l 3.0 -- rsync -a /home/ /mnt/backup/home

3. Rsync is already running with PID 4324 and we want to limit it to 50% CPU
cputool -p 4324 -c 50


Maybe your machine has multiple processors? easy, express the CPU utilization
in terms of % of all CPU's combined. So 100% utilization across 4 CPU's would
be 400. This is useful when you have a process which spawns children.