I have an urgent problem because my time is running out: I let my calculations process on a server with 8 cores therefore I'm using openMP in my c++ code and it works fine. Of course I'm not the only one who is using the server, so my capacity is not always 800%CPU. 
But it happened now several times that someone who started his python prog on the machine paralyzed mine and his prog completely: Although I was still using around 500%CPU the code was running approx. 100x slower - for me and the other guy. Do you have an idea what the reason could be, how to prevent it?
There can be a number of reasons for this, for example:

Increased failure rate in the branch prediction
Exhausted CPU cache
Filled up the memory bus
Too much context switching (this have an effect on many things, including all the previous points)
programs paralyzing each other on the server (c++ with openMP and python)