CS3413/Assignment7/code/main.c

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#define OFFSETBITS 12
#define PAGESIZE (1 << OFFSETBITS)
#define PAGETABLEBITS 10
#define ARCH 32
int framesSize;
unsigned int pageFault=0;
unsigned int pageHits = 0;
unsigned int pagesSwapped = 0;
int time = 0;



typedef struct frameEntry{
	unsigned int pageNumber;
	int lastUsed;
	bool dirty;
} frameEntry;

frameEntry* frames;

int getPageOffsetAddress(unsigned long logicalAddress){
	// Last 12 bits of logical address
	// Page size is 4096 bytes, and we bitwise AND with 4095 (111111111111) to get the last 12 bits
	return logicalAddress & (PAGESIZE-1);
}

int getPageNumber(unsigned long logicalAddress){
	// First 20 bits of logical address
	// Bitwise shift right 12 bits to get the first 20 bits, as the last 12 bits are discarded
	return logicalAddress >> OFFSETBITS;

}

void printPhysicalAddress(int frameID, unsigned long logicalAddress){
	printf("%lu -> %i\n",logicalAddress,frameID*PAGESIZE+getPageOffsetAddress(logicalAddress));
}

double computeFormula(){
	// probabilityOfNoPageFault ∗ 10 + probabilityOfMajorPageFaultWithOneCopy ∗ 1000 + probabilityOfMajorPageFaultWithTwoCopyOperations ∗ 3000
	double probabilityOfNoPageFault = 1 - (double)pageFault/(pageFault+pageHits);
	double probabilityOfMajorPageFaultWithOneCopy = (double)pageFault/(pageFault+pageHits)*(1-(double)pagesSwapped/pageFault);
	double probabilityOfMajorPageFaultWithTwoCopyOperations = (double)pageFault/(pageFault+pageHits)*(double)pagesSwapped/pageFault;
	return probabilityOfNoPageFault*10 + probabilityOfMajorPageFaultWithOneCopy*1000 + probabilityOfMajorPageFaultWithTwoCopyOperations*3000;
}

// Int so we can return the index of the frame if it is in the frames array
int isInFrames(int pageNumber){
	for (int i = 0; i < framesSize; i++){
		if (frames[i].pageNumber == pageNumber){
			return i;
		}
	}
	return -1;
}

int swapOut(){
	// Find the least recently used frame
	int leastRecentlyUsed = 0x7FFFFFFF;
	int leastRecentlyUsedIndex = -1;
	for (int i = 0; i < framesSize; i++){
		if (frames[i].lastUsed < leastRecentlyUsed){
			leastRecentlyUsed = frames[i].lastUsed;
			leastRecentlyUsedIndex = i;
		}
	}
	// Swap out is implied, so we increment pageSwapped
	if (frames[leastRecentlyUsedIndex].dirty) {
		pagesSwapped++;
	}

	return leastRecentlyUsedIndex;
}

int swapIn(int pageNumber){
	// Find the first empty frame
	for (int i = 0; i < framesSize; i++){
		if (frames[i].pageNumber == -1){
			pageFault++;
			frames[i].pageNumber = pageNumber;
			return i;
		}
	}
	// If no empty frames, swap out a frame
	int frameID = swapOut();
	frames[frameID].pageNumber = pageNumber;
	pageFault++;
	return frameID;
}



void readFromAddress(unsigned long logicalAddress){
	unsigned int pageNumber = getPageNumber(logicalAddress);
	int frameID = isInFrames(pageNumber);
	if (isInFrames(pageNumber) == -1){
		frameID = swapIn(pageNumber);
	}
	else{
		pageHits++;
	}
	frames[frameID].lastUsed = time;
	printPhysicalAddress(frameID,logicalAddress);
}

void writeToAddress(unsigned long logicalAddress){
	unsigned int pageNumber = getPageNumber(logicalAddress);
	int frameID = isInFrames(pageNumber);
	if (isInFrames(pageNumber) == -1){
		frameID = swapIn(pageNumber);
	}
	else{
		pageHits++;
	}
	frames[frameID].dirty = true;
	frames[frameID].lastUsed = time;
	printPhysicalAddress(frameID,logicalAddress);
}


int main(int argc, char** argv){
	//Disable printf buffering
	setbuf(stdout, NULL);

    framesSize = atoi(argv[1]);
	frames = calloc(framesSize,sizeof(frameEntry));
	// Initialize frames to -1, so we can check if a frame is empty
	for (int i = 0; i < framesSize; i++){
		frames[i].pageNumber = -1;
		frames[i].lastUsed = -1;
		frames[i].dirty = false;
	}
    unsigned long logicalAddress;
    char operation;
    printf("Logical addresses -> Physical addresses:\n");
    while(EOF != scanf("%c %lu\n",&operation,&logicalAddress) )
    {
        if (operation == 'r')
        {
            readFromAddress(logicalAddress);
        }
        else
        {
            writeToAddress(logicalAddress);
        }
		time++;
    }

    printf("\nStats:\nmajor page faults = %u\npage hits = %u\npages swapped out = %u\nEffective Access Time = %.3lf\n",pageFault,pageHits,pagesSwapped, computeFormula());
    return 0;
}