cachegrind

"It should, at this point, be noted again: cachegrind is a simulator which does not use
measurements from the processor ... Furthermore, the simulation does not take context switches
and system calls into account, both of which can destroy large parts of L2 and must flush L1i
and L1d. This causes the total number of cache misses to be lower than experienced in
reality."

As cachegrind has no idea of hardware prefetching then, OTOH, it may report the total number
of cache misses to be higher than in reality.