MP2 Multi-Programming

• Goal

1. Understand how memory management works in NachOS

1. Understand how to implement page table mechanism

• Assignment

• Trace code

• Starting from “threads/kernel.cc Kernel::ExecAll()”, “threads/thread.cc thread::Sleep()” until “machine/mipssim.cc Machine::Run()” is called for executing the first instruction from the user program.

• You need to explain at least the function mentioned below in the report.

1-1. threads/thread.cc

Thread::Sleep()

Thread::StackAllocate()

Thread::Finish()

Thread::Fork()

1-2. userprog/addrspace.cc

AddrSpace::AddrSpace()

AddrSpace::Execute()

AddrSpace::Load()

1-3. threads/kernel.cc

Kernel::Kernel()

Kernel::ExecAll()

Kernel::Exec()

Kernel::ForkExecute()

1-4. threads/scheduler.cc

Scheduler::ReadyToRun()

Scheduler::Run()

• Implement page table in NachOS

2-1. Working item: Modify its memory management code to make NachOS support multiprogramming.

2-2. Verification:

• Wrong results without multiprogramming

• Correct results with multiprogramming

• Correctly handle the exception about insufficient memory (Details in 2-3 requirement)

2-3. Requirement:

• Be careful that program size might exceeds a pagesize

• You must put the data structure recording used physical memory in kernel.h / kernel.cc

• You must set up “valid, readOnly, use, and dirty” field for your page table, which is defined under “TranslationEntry class” in translate.h

• You must call ExceptionHandler to handle the exception when there is insufficient memory for a thread. (i.e. MemoryLimitException).

Since there is no MemoryLimitException in ExceptionType class, you need to add it in machine.h and place it right before NumExceptionTypes. (0 points for using existing exception type or placing it in the wrong index.)

Also, you need to create the test cases to verify the correctness .TAs will use hidden test cases to test.

• When the thread is finished, make sure to release the address space and restore physical page status.

2-4. Hint: The following files “may” be modified…

• userprog/addrspace.*

• threads/kernel.*

• Report

• Cover page, including team members, Team member contribution.

• Explain your implementation.

• Explain how NachOS creates a thread (process), load it into memory and place it into the scheduling queue as requested in the Trace code part.

Your explanation on the functions along the code path should at least cover answer for the questions below:

• How does Nachos allocate the memory space for a new thread(process)?

• How does Nachos initialize the memory content of a thread(process), including loading the user binary code in the memory?

• How does Nachos create and manage the page table?

• How does Nachos translate addresses?

• How Nachos initializes the machine status (registers, etc) before running a thread(process)

• Which object in Nachos acts the role of process control block

• When and how does a thread get added into the ReadyToRun queue of Nachos CPU scheduler?
• Please look at the following code from urserprog/exception.cc and answer the question:

According to the code above, please explain under what circumstances an error will occur if the message size is larger than one page and why? (Hint: Consider the relationship between physical pages and virtual pages.)

• Instructions

1. Copy your code for MP1 to a new folder

$ cp -r NachOS-4.0_MP1 NachOS-4.0_MP2

1. Copy test file

$ cp /home/os2023/share/consoleIO_test* NachOS-4.0_MP2/code/test/

1. Compile / Rebuild NachOS

• cd NachOS-4.0_MP2/code/build.linux

• make clean

• make

1. Test your program

$ cd NachOS-4.0_MP2/code/test

• ../build.linux/nachos -e consoleIO_test1 -e consoleIO_test2

• Grading

1. Implementation correctness – 60%

1. Execute “../build.linux/nachos -e consoleIO_test1 -e consoleIO_test2” correctly

1. There will be hidden test cases to test the requirements. Make sure your code meets all the requirements.
2. Your working directory will be copied for validation after the deadline.

1. Report – 20%
   1. Upload to eeclass with the filename MP2_report_<Group Number>.pdf
2. Demo – 20%
   1. Demonstrate your implementation, and answer questions from TAs in 15 minutes.
   2. Some random test cases will be used for correctness verification.
   3. Demos will take place on our server, so you are responsible to make sure your code works on our server.
3. Refer to the syllabus for late submission penalty.
4. Plagiarism
   1. NEVER SHOW YOUR CODE to others.
   2. If the codes are similar to other people (including your upperclassman) and you can't answer questions properly during the demo, you will be identified as plagiarism.