Why does it take so long to complete MPI_Comm_spawn?

Hi all,

I've using MPI_Comm_spawn in my code to dynamic create only one process but it takes a long time to complete (about 15s on Intel Xeon E5620 2.40GHz). I'm doing anything else but to call MPI_Comm_spawn. My simple code is:

#include <mpi.h>
#include <stdio.h>

int main(int argc, char ** argv)
{
        int rank;
        MPI_Comm comm_parent, intercomm;
        int errcodes;
        double t0, t1;

        MPI_Init(&argc, &argv);
        MPI_Comm_get_parent(&comm_parent);

        if(comm_parent == MPI_COMM_NULL){
                // Parent process
                t0 = MPI_Wtime();
                MPI_Comm_spawn(argv[0], &argv[1], 1, MPI_INFO_NULL, 0, MPI_COMM_SELF, &intercomm, &errcodes);
                t1 = MPI_Wtime();
                printf("Spawn time: %f\n", t1-t0);
        }
        else{
                // Child process
                sleep(5);
                printf("child created\n");
        }
        MPI_Finalize();
        return(0);
}

Compiling: 

$ mpiicc teste_spawn2.c -o teste_spawn

Running: 

$ mpirun -n 1 -r ssh ./teste_spawn

Output:

Spawn time: 15.221280
child created

Does anyone know why?

Fernanda