some interesting performance loss happened with my measurements.
I have a system with two sockets, each socket is a E5-2680 processor. Each processor has 8 cores and with hyper-threading. The hyper-threading was ignored.
On this system, I started a program 16 times at the same time and each time pinned the program to different cores. At first, i set all cores to 2.7GHz and saw :
Program 0 Runtime 7.7s
Program 8 Runtime 7.63s
And then, i set cores on the second socket to 1.2GHz and saw:
Program 0 Runtime 12.18s
Program 8 Runtime 15.73s
The program 8 ran slower. It is clear, because core 8 had lower frequency. But why was program 0 also slower? Its frequency wasn't touched.