12 : Swapping

VPN = (VirtualAddress & VPN_MASK) >> SHIFT (Success, TlbEntry) = TLB_Lookup(VPN) if (Success == True) // TLB Hit if (CanAccess(TlbEntry.ProtectBits) == True) Offset = VirtualAddress & OFFSET_MASK PhysAddr = (TlbEntry.PFN << SHIFT) | Offset Register = AccessMemory(PhysAddr) else RaiseException(PROTECTION_FAULT) else // TLB Miss PTEAddr = PTBR + (VPN * sizeof(PTE)) PTE = AccessMemory(PTEAddr) if (PTE.Valid == False) RaiseException(SEGMENTATION_FAULT) else if (CanAccess(PTE.ProtectBits) == False) RaiseException(PROTECTION_FAULT) else if (PTE.Present == True) // assuming hardware-managed TLB TLB_Insert(VPN, PTE.PFN, PTE.ProtectBits) RetryInstruction() else if (PTE.Present == False) RaiseException(PAGE_FAULT)

PFN = FindFreePhysicalPage() if (PFN == -1) // no free page found PFN = EvictPage() // run replacement algorithm DiskRead(PTE.DiskAddr, PFN) // sleep (waiting for I/O) PTE.present = True // update page table with present PTE.PFN = PFN // bit and translation (PFN) RetryInstruction() // retry instruction