/*******************************************************************************
* Looks up an address in the current page table. If the entry for the given
* page is not valid, increments count_pagefaults and traps to the OS.
*
* @param vpn The virtual page number to lookup.
* @param write If the access is a write, this is 1. Otherwise, it is 0.
* @return The physical frame number of the page we are accessing.
*/
pfn_t pagetable_lookup(vpn_t vpn, int write) {
pfn_t pfn = current_pagetable[vpn].pfn; /* CHANGE ME */
/* FIX ME - Part 2
* Determine the PFN corresponding to the passed in VPN.
* Perform the lookup using the current_pagetable.
*/
if ((current_pagetable[vpn]).valid) {
return pfn;
}
count_pagefaults++;
return pagefault_handler(vpn, write);
}
/*******************************************************************************
* Looks up an address in the current page table. If the entry for the given
* page is not valid, traps to the OS.
*
* @param vpn The virtual page number to lookup.
* @param write If the access is a write, this is 1. Otherwise, it is 0.
* @return The physical frame number of the page we are accessing.
*/
pfn_t pagetable_lookup(vpn_t vpn, int write) {
pfn_t pfn;
/* FIX ME - Part 2
* Determine the PFN corresponding to the passed in VPN.
* current_pagetable variable accesses the process page table.
* if the pagetable entry is not valid, increment count_pagefaults, call
* pagefault_handler (traps to OS, returns frame number), and change pagetable
* entry to now be valid
*/
if(!current_pagetable[vpn].valid){
count_pagefaults++;
pfn = pagefault_handler(vpn,write);
}else{
pfn = current_pagetable[vpn].pfn;
}
return pfn;
}
/*******************************************************************************
* Looks up an address in the current page table. If the entry for the given
* page is not valid, increments count_pagefaults and traps to the OS.
*
* @param vpn The virtual page number to lookup.
* @param write If the access is a write, this is 1. Otherwise, it is 0.
* @return The physical frame number of the page we are accessing.
*/
pfn_t pagetable_lookup(vpn_t vpn, int write) {
pfn_t pfn;
/* Determine the PFN corresponding to the passed in VPN.
* Perform the lookup using the current_pagetable.
*/
pte_t *pte = current_pagetable + vpn;
pte->used = 1; // mark virtual frame as used
if (pte->valid) {
pfn = pte->pfn; // get physical frame number
}
else { // page fault!
count_pagefaults++;
pfn = pagefault_handler(vpn, write); // trap into pagefault_handler
}
return pfn;
}
int MMU(int pid, int addr, char type)
{
int frameNo;
int pageNo = (addr >> 8);
int offset = addr - (pageNo << 8);
int physicalAddr;
bool tlb_hit = false;
bool page_hit = false;
int lru;
int tlbFrame = pageNo % (TLB_ENTRY/2);
if(pageNo > NUM_PAGE) {
printf("invalid page number (NUM_PAGE = 0x%x): pid %d, addr %x\n", NUM_PAGE, pid, addr);
return -1;
}
if(pid > NUM_PROC-1) {
printf("invalid pid (NUM_PROC = %d): pid %d, addr %x\n", NUM_PROC, pid, addr);
return -1;
}
for(int i = 0; i < 2; i++) {
int check = tlb[pid][tlbFrame].entry[i];
if (tlb[pid][tlbFrame].valid[i] && check == pageNo) {
tlb_hit = true;
tlb[pid][tlbFrame].lru = !tlb[pid][tlbFrame].lru;
pageTable.stats.tlbHitCount++;
frameNo = tlb[pid][tlbFrame].frameNo[i];
break;
}
}
if (pageTable.entry[pid][pageNo].valid) {
page_hit = true;
pageTable.stats.hitCount++;
if (!tlb_hit) {
if (replacementPolicy == LRU) {
lruHelper(pageTable.entry[pid][pageNo].frameNo);
}
if (replacementPolicy == CLOCK) {
clockHelper(pageTable.entry[pid][pageNo].frameNo);
}
}
} else {
frameNo = pagefault_handler(pid, pageNo, type);
disk_read(frameNo, pid, pageNo);
pageTable.stats.missCount++;
}
if (!tlb_hit) {
lru = tlb[pid][tlbFrame].lru;
tlb[pid][tlbFrame].entry[lru] = pageNo;
tlb[pid][tlbFrame].frameNo[lru] = frameNo;
tlb[pid][tlbFrame].lru = !lru;
tlb[pid][tlbFrame].valid[lru] = true;
pageTable.stats.tlbMissCount++;
pageTable.entry[pid][pageNo].dirty = true;
}
physicalAddr = (frameNo << 8) + offset;
print_result(pid, type, tlb_hit, page_hit, addr, physicalAddr);
return physicalAddr;
}
