Как сэкономить память?

#define PORTS 260
#define MAX_NUMBER_OF_ENTRIES 255

STRUCT_T (*location)[MAX_NUMBER_OF_ENTRIES];

location = (STRUCT_T (*)[MAX_NUMBER_OF_ENTRIES]) malloc( sizeof(STRUCT_T) * PORTS * MAX_NUMBER_OF_ENTRIES );
 
location[PORT][ENTRY].a = 4;
location[PORT][ENTRY].b = 5;
...

STRUCT_S_T *location;
 
typedef STRUCT_T *STRUCT_S_T[MAX_NUMBER_OF_ENTRIES];

location[123][ENTRY].a = 4;
location[56][ENTRY].a = 5;
location[32][ENTRY].a = 5;

STRUCT_S_T * list = (STRUCT_S_T *)malloc(sizeof(STRUCT_S_T));

list = (STRUCT_S_T *)realloc((void *)list, n*sizeof(STRUCT_S_T));

#include <stdlib.h>
#include <mem.h>
#define PORTS 3
#define N 10
 
typedef struct STRUCT_T
{
 int port;
} STRUCT_T, *PSTRUCT_T;
 
int main()
{
 int i;
 STRUCT_T **location=(PSTRUCT_T*)malloc(PORTS*sizeof(PSTRUCT_T));
 setmem(location,PORTS*sizeof(PSTRUCT_T),0);
 for (i=0;i<PORTS;i++)
 {
  location[i]=(STRUCT_T*)malloc(N*sizeof(STRUCT_T));
  setmem(location[i],N*sizeof(STRUCT_T),0);
 }
 location[0][0].port=1;
 location[1][1].port=2;
 location[2][2].port=3;
 for (i=0;i<PORTS;i++)
  free(location[i]);
 free(location);
 return 0;
}