/* translate virtual address to pysical address. handles tlbmiss, page faults,
loads page to physical memory in case of page fault */
int translate(VirtualAddress address, PhysicalAddress &physicalAddress)
{
int rval = status_success;
PageEntry pageEntry; /* the page entry from page table. We use this for lookup in page table, and get frame no from it */
Page page; /* in case we need to get page from backing store and add it to physical memory */
FrameNumber frameno; /* in case we need to add page to physical memory */
PageNumber pageno = -1; /* page number we will lookkup. get this from virtual address */
int offset = -1; /* offset we will lookkup. get this from virtual address */
bool pagehit = false; /* flags */
bool tlbhit = false;
/* break address to page no offset */
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- get page number and offset\n");
pageno = getPageNumberFromLogicalAddress(address);
offset = getOffsetFromLogicalAddress(address);
/* we are storing he required frame number in the frameno value, weather we get a hit
from tlb, page table or page fault */
/* check in tlb */
tlb.lookup(pageno, frameno, tlbhit);
if(true == tlbhit)
{
/* we are done here */
zlog(ZLOG_LOC, "VirtualMemoryManager::translate - tlbhit !!\n");
tlbhits++;
}
else
{
/* check in page table tlb miss */
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- get page entry for page no : %d\n", pageno);
if(status_success != pageTable.lookup(pageno, pageEntry))
{
rval = status_failure;
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- unable to get page table entry\n");
goto exit1;
}
/* check if this is a page fault */
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- check for page fault\n");
if(true == pageEntry.isValid)
{
/* we are done */
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- page hit! \n");
frameno = pageEntry.frameNumber;
pagehit = true;
/* update counter */
pagehits++;
}
/* page fault code */
if(false == pagehit)
{
/* update counter */
pagefaults++;
/* get page from backing store */
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- page fault on page : %d, reading block : %d from backing store\n",
pageno, pageno);
if(status_success != backingStore.getPage(page, pageno*PageSize, PageSize))
{
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- unable to get page form backing store\n");
rval = status_failure;
goto exit2;
}
/* add to physical memory */
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- putting the page in physical memory\n");
if(status_success != physicalMemory.addPage(page, frameno))
{
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- unable to add page to physical memory\n");
rval = status_failure;
goto exit2;
}
/* update page entry */
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- update page Entry \n");
pageEntry.frameNumber = frameno;
pageEntry.isModified = false;
pageEntry.isValid = true;
/* add page entry to page table */
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- update page table\n");
if(status_success != pageTable.updatePageEntry(pageEntry, pageno))
{
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- unable to add entry to page table\n");
rval = status_failure;
goto exit2;
}
zlog(ZLOG_LOC, "VirtualMemoryManager::translate- lookup page table again\n");
frameno = pageEntry.frameNumber;
pagehit = true;
}
/* by this time we have a valid page frame mapping
if there was a tlb miss, update tlb table */
if(false == tlbhit)
{
TlbEntry tlbEntry;
tlbEntry.pageNumber = pageno;
tlbEntry.frameNumber = frameno;
tlbEntry.valid = true;
tlb.addEntry(tlbEntry);
}
}
/* page entry contains the frame number required */
physicalAddress = (frameno << numBitsForFrameOffset) + offset;
exit2:
exit1:
return rval;
}
int main(int argc, char **argv)
{
//cout<<argc<<endl;
//srand((int)time(NULL));
/**
* Configuration
*/
for(int i = 1; i < argc; i++)
{
if(i == 1)
{
if(strcmp(argv[i], "1") == 0)
{
debugMode = true;
} else {
debugMode = false;
}
} else if(i == 2)
{
sscanf(argv[i],"%d",&numberOfTLBEntries);
numberOfTLBEntries = getNearestBiggerPowerOfTwo(numberOfTLBEntries);
} else if(i == 3)
{
sscanf(argv[i],"%d",&numberOfPageFrames);
numberOfPageFrames = getNearestBiggerPowerOfTwo(numberOfPageFrames);
} else if(i == 4)
{
sscanf(argv[i],"%d",&numberOfInstructions);
} else if(i == 5)
{
sscanf(argv[i],"%d",&pageChangeAfterInstructionCount);
}
}
/**
* Initial State
*/
cout<<"Debug Mode: "<<debugMode<<endl;
cout<<"Total number of TLB Entries: "<<numberOfTLBEntries<<endl;
cout<<"Total number of Page Frames: "<<numberOfPageFrames<<endl;
cout<<"Total number of Instructions: "<<numberOfInstructions<<endl;
cout<<"Total number of Virtual Pages: "<<numberOfVirtualPages<<endl;
cout<<"On Average Virtual Address Page Changes after: "<<pageChangeAfterInstructionCount<<endl;
/**
* Operation starts...
* Create a pageTable, a TLB
*/
PageTable pageTable;
TranslationLookaheadBuffer tlb(numberOfTLBEntries);
pageTable.setTranslationLookaheadBuffer(&tlb);
for(int i = 0; i < numberOfInstructions; i++)
{
Instruction nextInstruction = getNextInstruction();
if(debugMode)
{
nextInstruction.print();
}
LookupResult l = tlb.lookup(nextInstruction.msbAddress);
if(l.isFound == true)
{
//do nothing
} else
{
if(debugMode)
{
printf("Cache Miss for page %02x\n",nextInstruction.msbAddress);
}
totalNumberOfCacheMisses += 1;
l = pageTable.lookup(nextInstruction.msbAddress);
if(l.isFound == true)
{
//do nothing
} else
{
if(debugMode)
{
printf("Page fault on page %02x\n",nextInstruction.msbAddress);
}
totalNumberOfPageFaults += 1;
pageTable.insert(nextInstruction.msbAddress);
l = pageTable.lookup(nextInstruction.msbAddress);
}
tlb.insert(nextInstruction.msbAddress, l.frameIndex);
//pageTable.insert(nextInstruction.msbAddress);
//l = pageTable.lookup(nextInstruction.msbAddress);
}
//
if(debugMode)
{
printf("Virtual Address: %02x%02x, Physical Address: %02x%02x\n", nextInstruction.msbAddress, nextInstruction.lsbAddress, l.frameIndex, nextInstruction.lsbAddress);
}
}
cout<<"Total number of Cache Misses: "<<totalNumberOfCacheMisses<<endl;
cout<<"Total number of Page Faults: "<<totalNumberOfPageFaults<<endl;
cout<<"Total number of Page Used: "<<pageTable.getUsedPageCount()<<endl;
cout<<"Total number of Page Changed: "<<pageChangeCount<<endl;
/*TranslationLookaheadBuffer tlb;
unsigned char accessPattern[] = "ABACBDADEDAEBAC";
for(int i = 0; i < 15; i++)
{
cout<<i<<","<<accessPattern[i]<<endl;
LookupResult result = tlb.lookup(accessPattern[i]);
if(result.isFound)
{
tlb.print();
} else {
cout<<"Cache Miss"<<endl;
tlb.insert(accessPattern[i],accessPattern[i]);
tlb.print();
}
}*/
return 0;
}
