Nachos Project Assignment 3

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Nachos Project Assignment 3

• Virtual Memory
• TA???

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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.

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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

4
Hints

• swap new SynchDisk
• All headers you need to see are in /filesys/
• Use this disk to be the swap space

5
Hints

• PageTable
• one pagetable per process
• FrameTable
• Record every physical page information
• SwapTable
• Record every sectors information in swap.

6
Hints

• PageTable
• decide your virtual page number
• TranslationEntry
• unsigned int virtualPage
• unsigned int physicalPage
• bool valid //whether in physical memory
• bool readOnly
• bool use //whether been referenced or
  modified
• bool dirty //whether been modified

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Hints

• FrameTable
• Each frame represent one physical page
• FrameInfoEntry
• bool valid
• bool lock
• unsigned int vpn //which virtual page is in
  this frame
• AddrSpace addrSpace //which process is
  using this frame

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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 entry
• AddrSpace addrSpace//which process is using
  this entry
• Access virtual memory in the disk by
  kernel-gtswap-gtWriteSector and kernel-gtswap-gtReadSe
  ctor.

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Hints

• Virtual Address Map to Physical Address
• Physical Address pageTable(virtual address /
  PageSize).physicalPage PageSize (virtual
  address PageSize)

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Hints

• Modify AddrspaceLoad(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-gtReadAt((kernel-gtmachine-gtmain
  Memoryphysical address),
  sizeToLoadNow,
  inFileAddr)

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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

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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.

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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

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Hand in your reports.

• Please compress following with zip.
• source code
• Final report
• power-point file
• tar zcvf b99901000.tar.gz
• E-mail your code and presentation files(report)
  to TA (b93901098_at_ntu.edu.tw).
• Deadline 2011/1/20 2359

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Grading Policy

• Correct Result 30
• Report 70