alexandrejenny@kolor.com:

Sorry my fault. My answer was done too fast.
Here's the exact code that didn't scaled.
My include's order to be sure :
#include <math.h>
#include <algorithm>

Ok. So it's std::sort and std::vector. I can model the problem.
The problem is not std::sort. The problem is iterators of std::vector. Debug iterators have some mutexes for debug checks. Define:

#define _HAS_ITERATOR_DEBUGGING 0

And the problem will go away.

Btw, in release build iterator debugging is turned off by default, and scaling is linear.