Memory mapping and time execution

Hi,

I am trying to map a file to memory. Everything work well except the time of execution of the memory mapping which increases after several times of execution.

In fact, I am mapping a 72MO file. The first times it took me 0,3s to do it. Few days after this took 3s and now it took me about 9s to map it. Is it normal?

Thank you for your response in advance.