Intro to operating system

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p4-start.cpp

p4-start.cpp

/**  @file   p4-start.c
 * 
 *  @author  Your Name
 *  @assg    Programming Assignment #4
 *  @date    March 8, 2019
 */
#include   < stdlib . h >
#include   < iostream >
#include   < fstream >
#include   < string >
using   namespace  std ;


// guarantee simulations have no more than this number of page references
// and we guarantee that you don't need to simulate a memory of more
// than this number of physical pages
const   int  MAX_PAGE_REFERENCES  =   50 ;
const   int  MAX_PHYSICAL_PAGES  =   10 ;

/** fifo page replacement simulation
 *  Perform first-in first-out (FIFO) page replacement simulation.
 *
 *  @arg  framesize The number of physical frames of memory to simulate.
 *  @arg  numref The number of page references in the simulated page address
 *       stream.  There should be pagestream[0] to pagestream[numref-1]
 *       pages in the pagestream.
 *  @arg  pagestream An array of integers.  The value indicates a references
 *       page, and the index is the time when the page was referenced.
 */
void  fifo ( int  framesize ,   int  numref ,   int *  pagestream )
{
   // implement fifo (first-in-first-out) page replacement here

   // an example of stepping through time and the pagestream to get
   // you going
   for   ( int  time = 0 ;  time  <  numref ;  time ++ )
   {
    cout  <<   "Time: "   <<  time  <<  endl ;
    cout  <<   "Page: "   <<  pagestream [ time ]   <<  endl ;
    cout  <<  endl ;
   }
}

/** lru page replacement simulation
 *  Perform least recently used (LRU) page replace simulation.
 *
 *  @arg  framesize The number of physical frames of memory to simulate.
 *  @arg  numref The number of page references in the simulated page address
 *       stream.  There should be pagestream[0] to pagestream[numref-1]
 *       pages in the pagestream.
 *  @arg  pagestream An array of integers.  The value indicates a references
 *       page, and the index is the time when the page was referenced.
 */
void  lru ( int  framesize ,   int  numref ,   int *  pagestream )
{
   // implement lru (least recently used) page replacement here

   // an example of stepping through time and the pagestream to get
   // you going
   for   ( int  time = 0 ;  time  <  numref ;  time ++ )
   {
    cout  <<   "Time: "   <<  time  <<  endl ;
    cout  <<   "Page: "   <<  pagestream [ time ]   <<  endl ;
    cout  <<  endl ;
   }
}

/** Load page references from file
 *  Load the stream of simulated page references from the indicate file.
 *  return the references in a simple array of integers.
 *
 *  @param  simfilename  The name of the file to open and read page references
 *           from.
 *  @param  pagestream Should be a pointer to an array of integers.  The array
 *           is filled with the page references on return.  The index of each
 *           reference indicates time when the page references occurs in
 *           simulation.
 *  @returns  int The number of page references in the page stream.
 */
int  loadPageStream ( char *  simfilename ,   int *  pagestream )
{
  ifstream pagestreamfile ( simfilename );
   int  pageref ;
   int  time ;

   // If we can't open file, abort and let the user know problem
   if   ( ! pagestreamfile . is_open ())
   {
    cout  <<   "Error: could not open page simulation file: "   <<  simfilename 
      <<  endl ;
    exit ( 1 );
   }

   // Load simulated page references into integer array
  time  =   0 ;
   while   ( ! pagestreamfile . eof ())
   {
    pagestreamfile  >>  pageref ;
    pagestream [ time ]   =  pageref ;
    time ++ ;
    pagestreamfile  >>  ws ;    // extract newlines from end of line
   }

   return  time ;
}

/** Main entry point of simulator
 *  The main entry point of the page replacement simulator.  Process 
 *  command line arguments and call appropriate simulation.  We expect
 *  three command line arguments: pageref.sim  [fifo|lru]  framesize
 *
 *  @param  argc The argument count
 *  @param  argv The command line argument values. We expect argv[1] to be the
 *              name of a file in the current directory holding page file
 *              references, argv[2] to indicate [fifo|lru] and argv[3] to be
 *              an integer indicating size of memory in frames.
 */
int  main ( int  argc ,   char **  argv )
{
   int  framesize  =   0 ;
   int  pagestream [ MAX_PAGE_REFERENCES ];
   int  numref ;
  string scheme ;

   // If not all parameters not provided, abort and let user know of problem
   if   ( argc  !=   4 )
   {
    cout  <<   "Usage: "   <<  argv [ 0 ]   <<   " pageref.sim [lru|fifo] framesize"   <<  endl ;
    exit ( 1 );
   }

   // load page stream and parse command line arguments
  numref  =  loadPageStream ( argv [ 1 ],  pagestream );
  scheme . assign ( argv [ 2 ]);  
  framesize  =  atoi ( argv [ 3 ]);

   // perform simulation of indicated replacement scheme
   if   ( scheme  ==   "lru" )
   {
    lru ( framesize ,  numref ,  pagestream );
   }
   else   if   ( scheme  ==   "fifo" )
   {
    fifo ( framesize ,  numref ,  pagestream );
   }
   else
   {
    cout  <<   "Error: unknown page replacement scheme: "   <<  scheme  <<  endl ;
    exit ( 1 );
   }
}

prog-04.pdf

Programming Assignment #4

CSci 430 Spring 2019

Dates:

Assigned: Monday March 5, 2019 Due: Wednesday April 10, 2019 (before Midnight)

Objectives:

� Better understand page replacement memory management properties through implementation of page replacement schemes.

� Implement basic page replacement schemes, such as least recently used and �rst-in-�rst-out (FIFO)

� Practice C/C++ usage and implementation of queues and stacks needed for memory management algorithms.

� Be able to compare, contrast and understand the relative performance of di�erent replacement schemes.

Description:

In programming assignment #4 you are to write a simulation of a page replacement memory management system. You will be implementing least recently used (LRU) and �rst-in-�rst-out (FIFO) page replacement schemes (Chapter 8, pg 369).

Your program should read from a �le to get information about the se- quence of page faults that occur. I will provide a simple example of such a text �le. It consists simply of one integer value per line, which represent a sequence of page faults that occur in the simulation. For example:

1

----------- Begin Input File pagestream.txt --------

2

3

2

1

5

2

4

5

3

2

5

2

------------ End Input File -------------------------

represents the sequence of page address faults/requests for the Figure 8.15 example from our text book.

Your program should read 3 pieces of information from the command line: simulation �le name, replacement scheme [lru or �fo], and the number of physical frames in memory. For example:

$ p3.exe pagestream.sim lru 3

To get you started, I have included a main() function and a main event loop in a �le called p3-start.cpp, that can open and read in the page stream �le into an array. Your main job is to implement the least recently used (LRU )and �rst-in-�rst-out FIFO page replacement algorithms. The FIFO page replacement should be the simplier of the two, so I would suggest you get that scheme working �rst. In FIFO, of course, when there is a page reference 'miss', you simply need to keep a pointer or index into your frames indicating the next physical frame number that should be replaced.

Your program should take the indicated stream of page addresses (a �le name) as the �rst parameters. The second parameter indicates the total number of frames that the system is simulating (in the above example this is 3, the same as the example shown in Figure 8.15). Your implementa- tion should be able to simulate systems with up to 10 physical frames at a maximum.

The output for your simulation should be formatted in exactly the fol- lowing format. To get exact output format and correct answers for the include pagestream.sim input �le, look at the results in the zip �le called pagestream-lru-3.out and pagestream-�fo-3.out.

2

Time: 0

Page: 2

Frame1: 2

Frame2: 0

Frame3: 0

Hit ratio: 0 / 12 (0)

Time: 1

Page: 3

Frame1: 2

Frame2: 3

Frame3: 0

Hit ratio: 0 / 12 (0)

Time: 2

Page: 2

Frame1: 2

Frame2: 3

Frame3: 0

Hit ratio: 1 / 12 (0.0833333)

etc.

To interpret, for each page reference in the pagestream, you will print out the time, the page that was referenced (time starts at 0), the Page reference that was made at that time, and the state of the system frames after that page is processed.

If you use the pagestream sequence from �gure 8.15 with a system frame size of 3 you should be able to reproduce the LRU and FIFO results shown. I have given you example correct outputs for both FIFO and LRU page replacement, for systems with both 3 and 4 physical frames of memory. Use these correct example outputs to test that your implementation is working correctly. I will test your program using di�erent pagestream sequences and di�erent system frame sizes, so make sure you thoroughly test your algorithm yourself before submitting.

3

pagestream.sim

2 3 2 1 5 2 4 5 3 2 5 2

pagestream-fifo-3.res

pagestream-fifo-4.res

pagestream-lru-3.res

pagestream-lru-4.res