Lab 6: C++ Fixed-size Memory Manager

1. Overload new and delete operators in C++.
2. Download memmgr-0.0.1.tar.gz.
3. Ungzip and untar memmgr-0.0.1.tar.gz and compile the code.

     $ gzip -cd memmgr-0.0.1.tar.gz | tar xvf -
     $ cd memmgr-0.0.1
     $ configure
     $ make
     

4. Edit mem_mgr.h and fill in the code at places marked as XXX.

   #ifndef MEM_MGR_H
   #define MEM_MGR_H
   
   #include <stdio.h>
   #include <assert.h>
   
   class MemMgr {
   public:
       int iSize;
       int iCount;
       void *pvList;
       void *pvFree;
   
   public:
       MemMgr(int iSize, int iCount) :
           iSize(iSize),
           iCount(iCount),
           pvList(NULL),
           pvFree(NULL) {
           assert(iSize >= sizeof(void *));
       }
       ~MemMgr(void) {
           while (pvList) {
               char *p = (char *)pvList;
               pvList = *(void **)pvList;
               delete []p;
           }
       }
       void *malloc(void) {
           // XXX: write your code here
           return (NULL);
       }
       void free(void *p) {
           // XXX: write your code here
       }
   };
   
   #endif // MEM_MGR_H
     

5. Test your code by running main and main_mm with count # 1000, 10000, 100000, 1000000, 2000000, 3000000, 4000000, 5000000, 6000000, 7000000, 8000000, 9000000, 10000000. Keep track the user time returned by the command time.

     $ time main 1000000
     1.040u 0.012s 0:01.04 100.9%    0+0k 0+0io 0pf+0w
     $  time main_mm 1000000
     0.980u 0.004s 0:01.00 98.0%     0+0k 0+0io 0pf+0w
     

6. Keep the user time in a text file, say, time.txt. For example:

     1000     ...    ...
     ...
     1000000  1.040  0.980
     ...
     

7. Plot the data using gnuplot.

     $ gnuplot
     gnuplot> plot 'time.txt' using 1:2 with lines title "Without MM",\
                   'time.txt' using 1:3 with lines title "With MM"
     

8. Explain the graph.