why allocation of large amount of small objects so slow (x10) in D?

[nobody]

$ g++     alloc.cpp   -o alloc
$ time ./alloc
real    0m1.946s
user    0m1.688s
sys     0m0.256s

$ dmd -O -release allocd.d
$ time ./allocd
real    0m22.734s
user    0m22.353s
sys     0m0.360s

$ cat alloc.cpp
#include <vector>

typedef std::vector<int> intvec;
typedef intvec* intvecp;

int main() {
  int i, n = 20000000;
  intvecp* iva;
  iva = new intvecp[n];
  for (i = n; i-- > 0; ) {
    iva[i] = new intvec();
  }

  return 0;
}

$ cat allocd.d
int main() {
  int i, n = 20000000;
  Object[] oa;
  oa = new Object[n];
  for (i = n; i-- > 0; ) {
    oa[i] = new Object();
  }

  return 0;
}