Nachos Project Assignment 3

Virtual MemoryTA:吳哲榮

Assignment

Test case /test/matmult.c /test/sort.c

Both test programs are greater than whole memory.

Goal – run this two programs concurrently, and get the correct result.

Under RR scheduling.

Hints

File system – swap space Add some table to help you record all

the information. PageTable FrameTable SwapTable

Catch PageFaultException Construct your Virtual Memory

Manager

Hints

swap = new SynchDisk All headers you need to see are in

/filesys/ Use this disk to be the swap space

Hints

PageTable one pagetable per process

FrameTable Record every physical page information

SwapTable Record every sector’s information in

swap.

Hints

PageTable decide your virtual page number

TranslationEntry{unsigned int virtualPage;unsigned int physicalPage; bool valid; //whether in physical memorybool readOnly; bool use; //whether been referenced

or modifiedbool dirty; //whether been modified}

Hints

FrameTable Each frame represent one physical page

FrameInfoEntry{

bool valid;bool lock;unsigned int vpn; //which virtual page is

in this frameAddrSpace *addrSpace; //which process is

using this frame};

Hints

SwapTable The number of entries in swapTable is the same as swap

sectors. Each entry represent one frame in the disk.

FrameInfoEntry{

bool valid; //whether entry been used

bool lock;unsigned int vpn; //which virtual page is in

this entryAddrSpace *addrSpace;//which process is using

this entry};

Access virtual memory in the disk by kernel->swap->WriteSector and kernel->swap->ReadSector.

Hints

Virtual Address Map to Physical Address

Physical Address = pageTable[(virtual address / PageSize)].physicalPage * PageSize + (virtual address % PageSize)

Hints

Modify Addrspace::Load(char *fileName) load one page once

1.acquire one page When all physical memory frames are occupied,

please design a page replacement method to get a frame.

2.Map virtual address to physical address Invoke ‘executable->ReadAt(&(kernel-

>machine->mainMemory[physical address]), sizeToLoadNow, inFileAddr)’

Virtual Memory Manager

Public: int TranslateAddr(AddrSpace *space, int

virtAddr);// translate virtual address to physical address

bool AcquirePage(AddrSpace *space, unsigned int vpn);// get a frame

void ReleasePage(AddrSpace *space, unsigned int vpn);// release a page

void PageFaultHandler(void);// manage page fault

PageFaultHandler

PageFaultHandler Put the pages in swaptable into

frametable. When all physical memory frames are

occupied, please design a page replacement method to get a frame.

Assignment Requirements

Assignment Report (1/20 on the class)

How you modified Nachos to make it support virtual memory – important code segments

Test cases and demonstration to show the correctness of your design

Everything you consider important

Hand in your reports.

Please compress following with zip. source code Final report power-point filetar zcvf b99901000.tar.gz

E-mail your code and presentation files(report) to TA (b93901098@ntu.edu.tw).

Deadline: 2011/1/20 23:59

Grading Policy

Correct Result 30% Report 70%