Investigate methodologies to limit process CPU usage on Linux

[giampaolo]

I bumped into this article:
http://blog.scoutapp.com/articles/2014/11/04/restricting-process-cpu-usage-using-nice-cpulimit-and-cgroups
...describing different methods on how to limit CPU usage of a certain process on Linux amongst which:

• niceness (supported already)
• cpulimit cmdline tool: AFAIU it's a tool which ciclically sends supension signal to the process in order to keep it "calm"
• process groups (not supported by psutil)

The third one looks the most promising and needs more investigation 'cause I don't know exactly how it works.

[giampaolo]

Closing as duplicate of #490.