Language: Java
Synopsis:
This was quite a project. Now looking back over it after I have finished, I see some of the answers to the questions I had that I thought weren't ever answered. However my instructor just assigned the project and didn't know much about the specifics.
Here is the exact book instructions for the project:
Designing a Virtual Memory Manager
InputFile.txt
correct output for InputFile.txt
Generate a Backing Store file
Random Access File example
Note:
Our instructor told us that we did not have to do the modifications as stated at the end of the instructions. So this implementation only accounts for physical memory size and virtual memory size being the same. My grade was 93%. The reason is I compared my output to the correct output using the website http://text-compare.com/ and all of my values were correct yet some of my translated addresses were not correct. Not sure where I went wrong. Also my statistics were all correct as well. I spend about 30 hours on this project.
Purpose:
To build part of an operating system--specifically a Virtual Memory Manager.Synopsis:
This was quite a project. Now looking back over it after I have finished, I see some of the answers to the questions I had that I thought weren't ever answered. However my instructor just assigned the project and didn't know much about the specifics.
Here is the exact book instructions for the project:
Designing a Virtual Memory Manager
package virtualMMan;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.HashMap;
public class VmmDriver {
private final int TABLE_ENTRIES_OR_SIZE = 256;
private final int PHYSICAL_MEMORY_SCALAR = 1;
private int [] pageTable = new int [TABLE_ENTRIES_OR_SIZE];
private int [] frameTable = new int [TABLE_ENTRIES_OR_SIZE];
private HashMap victimFrameLocater = new HashMap<Integer,Integer>();
private ArrayList<Integer> framesFIFOQueue = new ArrayList<Integer>();
private HashMap TLB = new HashMap<Integer,Integer>(17, 1);
private ArrayList<Integer> TLB_FIFOQueue = new ArrayList<Integer>();
private byte [] physicalMemory = new byte [TABLE_ENTRIES_OR_SIZE*TABLE_ENTRIES_OR_SIZE];
private int physicalMemoryPointer = 0;
private int availableFrameCounter = 0;
private int bitMask = 0x00FF;
private double pageFaults, numOfAddresses, pageFaultRate, TLBHits = 0;
public static void main(String[] args) {
new VmmDriver().run();
}
public void run(){
//Input File with Virtual Addresses
String filename = ("U:\\Project3\\src\\resources\\InputFile.txt");
// the file representing the simulated disk
File backStorePath;
RandomAccessFile backingStore = null;
/*Create pageTable and
* initialize each index with -1.
* This indicates that the entry in
* the pageTable is invalid.*/
for(int i = 0; i <(TABLE_ENTRIES_OR_SIZE-1); i++){
pageTable[i] = -1; }
/*Create frameTable and
* initialize each index starting at 0
* and increasing by TABLE_ENTRIES_OR_SIZE
* at each iteration*/
int frameNum = 0;
for(int i = 0; i < (TABLE_ENTRIES_OR_SIZE)-1; i++){
frameNum = i*(TABLE_ENTRIES_OR_SIZE);
frameTable[i] = frameNum;}
BufferedReader br = null;
try
{
File file = new File(filename);
FileReader fr = new FileReader(file);
br = new BufferedReader(fr);
String data;
while((data = br.readLine()) != null)
{
/*Right-Shift virtual Address by 8 bits virtual
* address space256).
* Use bitMask to "mask" Least Significant 0xFF bits*/
int pageNumber = (Integer.parseInt(data) >> 8);
int offset = (Integer.parseInt(data) & bitMask);
int val = 0;
int frameNumber = 0;
//Page Fault handling
if((!(TLB.containsKey(pageNumber)) && pageTable[pageNumber] == -1)){
try {
backStorePath = new
File("U:\\Project3\\BACKING_STORE_A");
backingStore = new RandomAccessFile(backStorePath, "r");
// seek to byte position pageNumber * TABLE_ENTRIES_OR_SIZE
backingStore.seek((pageNumber)*(TABLE_ENTRIES_OR_SIZE));
backingStore.read(physicalMemory, physicalMemoryPointer, TABLE_ENTRIES_OR_SIZE);
val = physicalMemory[physicalMemoryPointer+offset];
physicalMemoryPointer +=TABLE_ENTRIES_OR_SIZE;
//Update PageTable
pageTable[pageNumber] = frameTable[availableFrameCounter];
frameNumber = pageTable[pageNumber];
availableFrameCounter++;
//Update TLB
if(TLB.size() <= 16){
addtoTLB(pageNumber,frameNumber);
}
else{
TLB.remove(TLB_FIFOQueue.get(0));
}
pageFaults++;
//Place value in physicalMemory
//physicalMemory[frameNumber] = val;
//Take Frame number "or" it with offset to get physical address
int physicalAddress = frameNumber | offset;
System.out.println("Virtual address: " + data +" Physical address: "
+ physicalAddress + " Value: " + val);
//System.out.println("PageNumber: " + pageNumber
//+ " FrameNumber: " + frameNumber + " Offset: " + offset);
numOfAddresses++;
}
catch (IOException e) {
System.err.println ("Unable to start the disk");
//System.exit(1);
}
finally {
backingStore.close();
}
}//if
else{
if(TLB.containsKey(pageNumber)){
frameNumber = checkTLB (pageNumber);
int physicalAddress = frameNumber | offset;
System.out.println("Virtual address: " + data +" Physical address: "
+ physicalAddress + " Value: " + physicalMemory[frameNumber+offset]);
TLBHits++;
numOfAddresses++;
}
else{ //Take pageNumber as index and get Frame number from Page table
frameNumber = pageTable[pageNumber];
//Take Frame number "or" it with offset to get physical address
int physicalAddress = frameNumber | offset;
System.out.println("Virtual address: " + data +" Physical address: "
+ physicalAddress + " Value: " + physicalMemory[frameNumber+offset]);
//System.out.println("PageNumber: " + pageNumber +
//" FrameNumber: " + frameNumber + " Offset: " + offset);
numOfAddresses++;
}
}//else
}//while
}//try
catch(ArrayIndexOutOfBoundsException e){
e.printStackTrace();
}
catch(IOException e){
System.out.println(e + "File: " + "\"" + filename + "\"" + " not Found.");
}
finally{
try{
if(br != null){
br.close();
}
}
catch(IOException e){
e.printStackTrace();
}
}
printStats();
}//run()
public void addtoTLB (int pageNumber, int frameNumber ){
// Put value into Hash Map
TLB.put(pageNumber, frameNumber);
TLB_FIFOQueue.add(pageNumber);
}//addtoTLB
public int checkTLB (int pageNumber){
return (int) TLB.get(pageNumber);
}//checkTLB
public void printStats(){
pageFaultRate = pageFaults/numOfAddresses;
System.out.println("Number of Translated Addresses = " + (int)numOfAddresses);
System.out.println("Page Faults = " + (int)pageFaults);
System.out.println("Page Fault Rate = " + pageFaultRate);
System.out.println("TLB Hits = " + (int)TLBHits);
System.out.println("TLB Hit Rate = " + (TLBHits/numOfAddresses));
}
}InputFile.txt
correct output for InputFile.txt
Generate a Backing Store file
Random Access File example
Note:
Our instructor told us that we did not have to do the modifications as stated at the end of the instructions. So this implementation only accounts for physical memory size and virtual memory size being the same. My grade was 93%. The reason is I compared my output to the correct output using the website http://text-compare.com/ and all of my values were correct yet some of my translated addresses were not correct. Not sure where I went wrong. Also my statistics were all correct as well. I spend about 30 hours on this project.
