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Nachos Project Assignment 3 Memory Management

Nachos Project Assignment 3 Memory Management. TA: Chien -Wen, Huang. Advisor: Farn , Wang. 2015/12/16. Outline. Memory Management Report Grading Policy & Late Policy. Reference. Memory Management. About the virtual memory manager, swap, page fault handler…. The Goal of Project 3.

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Nachos Project Assignment 3 Memory Management

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  1. Nachos Project Assignment 3Memory Management TA: Chien-Wen, Huang. Advisor: Farn, Wang. 2015/12/16

  2. Outline • Memory Management • Report • Grading Policy& Late Policy. • Reference.

  3. Memory Management About the virtual memory manager, swap, page fault handler…

  4. The Goal of Project 3. • Have you run these test cases in the test folder? • /test/matmult.c • /test/sort.c • Both the test cases require lots of memory. • Larger than the physical memory! • Goal: Run this two programs concurrently, and get the correct result. • Remember to specify the scheduling algorithm you used in the report. • No way to pass this project by simply modify the memory size in “machine”.

  5. Some Hints. • File system – swap space. • Maintain three tables to record the information. • PageTable • FrameTable • SwapTable • Think how to “load” the page correctly. • Deal with the PageFaultException. • Design your own “Virtual Memory Manager".

  6. Swap Space - Create Disk. • swap = new SynchDisk in your kernel. • Use the disk as the swap space. • Access the virtual memory in the disk by… • kernel->swap->WriteSector • kernel->swap->ReadSector • See “synchdisk.cc” and other files in /filesys for details! • Read the header in those files first.

  7. Maintain Three Tables. • PageTable • One page table per process. • Decide your virtual page number. • FrameTable • Record every physical page’sinformation. • Each frame represent one physical page. • SwapTable • Record every sector’s information in swap. • The number of entries in SwapTable is the same as the swap sectors. • Each entry represent one frame in the disk.

  8. Maintain Three Tables. Physical memory FrameTable 1 2 3 4 PageTable 1 2 3 4 SwapTable 1 2 3 4

  9. Maintain Three Tables - PageTable • For each entry in PageTable • TranslationEntry { unsigned intvirtualPage; //virtual memory page unsigned intphysicalPage; //if in physical memory bool valid; //if in physical memory bool use; //been used(read or write) bool dirty; //been modified };

  10. Maintain Three Tables - FrameTable • For each entry in FrameTable • FrameInfoEntry { Bool valid; //if being used Bool lock; AddrSpace *addrSpace; //which process is using this page Unsigned intvpn; //which virtual page of the process is stored in this page };

  11. Maintain Three Tables - SwapTable • For each entry in SwapTable • FrameInfoEntry { Bool valid; //if being used Bool lock; AddrSpace *addrSpace; //which process is using this page Unsigned intvpn; //which virtual page of the process is stored in this page }; // same as the FrameTable

  12. Back to Nachos - Addrspace::Load • Note: Load 1 page a time. • First ask for 1 page, if the FrameTable is full, select 1 frame and put it into SwapTable. • Design your own page replacement method to get the frame. • Specify the method in your report. • Mapping virtual address to physical address. • Invoke “executable->ReadAt(&(kernel->machine->mainMemory[physical address]), sizeToLoadNow, inFileAddr)”

  13. Address Mapping • Map the Virtual Address to Physical Address. • Like the way you used in project 1. • Physical Address = pageTable[(virtual address / PageSize)].physicalPage * PageSize + (virtual address % PageSize)

  14. One Possible Way to Implement:Create a new class “Memory Manager” • Class MemoryManager { IntTransAddr(AddrSpace *space, intvirtAddr); //return phyAddr (translated from virtAddr) Bool AcquirePage(AddrSpace *space, intvpn); //ask a page (frame) for vpn Bool ReleasePage(AddrSpace *space, intvpn); //free a page Void PageFaultHandler(); //will be called when manager want to swap a page from SwapTable to FrameTable and the FrameTable is full. };

  15. Page-Fault Handler? • Put the pages in SwapTable into FrameTable. • When all physical memory frames are occupied, design a page replacement method to get a frame. • Remember to specify it in your report! • You can do this work in your own way.

  16. Some files that might be useful. • For the disk usage details, see: • /filesys/synchdisk.h • /filesys/synchdisk.cc • Other files in /filesys (Optional). • For the swap space initialization: • /userprog/userkernel.h • /userprog/userkernel.cc • For the table maintaining, see: • /machine/machine.h and /machine/machine.cc • /machine/translate.h and /machine/translate.cc

  17. Some files that might be useful. • For the table maintaining, see: • /machine/machine.h and /machine/machine.cc • /machine/translate.h and /machine/translate.cc • For the loading of pages. • userprog/addrspace.h • userprog/addrspace.cc • Always see the header and comments first. • Based on your implementation, there might be different files that your need to see and modify.

  18. Report & Policy Report contents, grading policy, late policy and the summary.

  19. Report • Report • Motivation and the problem analysis. • What’s your plan to deal with the problem(high-level). • How you really implement to solve the problem in Nachos. • You can including some (not all) important code segments and comments. • Experiment result and some discussion. • Extra effort or observation. • Please saved as [Student ID]_NachOS_report.pdf • E.g. r04942044_NachOS_report.pdf • NOT [r04942044]_NachOS_report.pdf

  20. Extra effort as Bonus • The replacement method you design. • Extra observation or modification on nachos. • Please write it down on your report if you did.

  21. Hand in source code & report • Source Code • tar zcvf [Student ID]_Nachos3.tar.gz ./nachos-4.0 • E.g. r04942044_Nachos3.tar.gz • NOT .gz or .rar. • Please include ALL the nachos code. • Mail your source code and report to r04942044@ntu.edu.tw • One pdf file as report and one tar.gz file as source code. • Deadline: Jan.20.2016, 23:59:59.

  22. Grading PolicyWith presentation • Nachos source code: (30%) • Report: (30%) • Correct format: (20%) • Presentation: (20%) • Bonus

  23. Grading PolicyWithout presentation • Nachos source code: (40%) • Report: (40%) • Correct format: (20%) • Bonus

  24. Late Policy • 10% penalty per day. • Late penalty only holds for a week • After 7 days, you will get 70% penalty, but no more penalty after that. • That is, after n(n>=7) days, you will still get 70% penalty. • Don’t give up! • No plagiarism.

  25. Summary • Implement the memory manager (mainly the virtual memory). • Write the report. • Send to TA in the correct format before the deadline. • Jan.20.2016, 23:59:59 • Prepare the presentation if you should.

  26. Reference • Nachos Beginner’s Guide: • https://www.ida.liu.se/~TDDI12/material/begguide/ • Nachos Virtual Memory Slides: • http://www.ittc.ku.edu/~dmitchell/EECS678/labs/old-labs/lab12/NachosVM.pdf • Search Engine as your friends. 

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