怎么提高二维数组的动态内存配置与回收的速度

如何提高二维数组的动态内存配置与回收的速度
我这样定义了一个二维指针数组
char   **A_segment   =new   char*[２００００００];
for(int   i=0;i <2000000;i++)
{
    A_segment[i]=new   char[15];
}

[解决办法]
const int SIZE = 2000000;
const int STEP = 15;
char* mem = new char[SIZE * sizeof(char*) + SIZE*STEP];
char** A_segment = reinterpret_cast <char**> (mem);
char* data = mem + SIZE * sizeof(char*);
for(int i=0;i <SIZE;i++)
{
A_segment[i] = data;
data += STEP;
}

//... do something
strcpy(A_segment[SIZE-1], "hello! ");
printf( "%s\n ", A_segment[SIZE-1]);

//release
delete mem;