Requred memory

Calculated as  dim * dim * dim * 3 * sizeof (int) , where dim - dimension of matrixes.

Allocated memory

Memory allocated by the operation system for arrays m1, m2, m3.

Reserved memory

Address space, rezerved by the operation system for arrays m1, m2, m3.
Not all reserved memory pages are physically allocated.

Normalized time

Contains time, recounted for one pass of the innermost cycle.
Calculated as  T / (dim * dim * dim) , where T - total time, dim - dimension of matrixes.
Normalized time may be considered as time for accumulation  sum += m1 [i] [k] * m2 [k] [j];