Description
Task:
In assignment 1, we assumed that the system had an infinite amount of memory. In this assignment, the operating system has a limited amount of memory and this needs to be managed to meet process demands. You will write a program to simulate a system that uses paging with virtual memory. The characteristics of the system are described below:
• Memory: The system has F frames available in user memory space. During execution, the processor will determine if the page required for the currently running process is in main memory.
a. If the page is in main memory, the processor will access the instruction and continue.
b. If the page is not in main memory, the processor will issue a page fault and block the process until the page has been transferred to main memory.
c. Initially no page is in the memory. I.e. the simulation will be strictly demand paging, where pages are only brought into main memory when they are requested.
d. In fixed allocation scheme frames are equally divided among processes, additional frames remain unused. In variable allocation scheme all frames are available to the processes.
• Paging and virtual memory: The system uses paging (without segmentation).
a. Each process can have a maximum 50 pages where each page contains a single instruction.
b. For page replacement you will need to apply First In First Out (FIFO) policy.
c. You will need to implement two different schemes for resident set management
i. ‘Fixed Allocation with Local Replacement Scope’ – In this scheme, the frames allocated to a process do not change over the simulation period i.e. even after a process finishes, the allocated frames do not change. And the page replacements (if necessary) will occur within the frames allocated to a process using FIFO policy.
d. All pages are read-only, so no page needs to be written back to disk.
b. Swapping in a page takes 6 units of time (if a page required by a process is not in main memory, the process must be put into its blocked state until the required page is available).
• Scheduling: The system is to use a Round Robin short-term scheduling algorithm with time a quantum of Q.
a. Executing a single instruction (i.e. a page) takes 1 unit of time.
b. Switching the processes does not take any time.
c. All the processes start execution at time t=0. And they will be processed in the order the process names appear in the input.
e. If multiple process becomes ready at the same time then they will enter the ready queue in the order they became blocked.
f. If a process P1 is finishes its time quantum at t1 and another process P2 becomes unblocked at the same time t1, then the unblocked process P2 is added in the ready queue first and the timequantum expired process P1 is added after that.
You are to compare the performance of the FIFO with Fixed Allocation & Local Page Replacement and FIFO with Variable Allocation & Global Page Replacement algorithms.
Please use the basic versions of the policies introduced in the lectures.
Input and Output
Input to your program should be via command line arguments, where the arguments are system configurations and the names of files that specify the execution trace of different processes. All processes start execution at time 0, and are entered into the system in the order of the command line arguments (with the third argument being the earliest process). For example:
java A3 30 3 process1.txt process2.txt process3.txt
Since we assume that each page contains a single instruction, an execution trace is simply a page request sequence.
For example: (process1.txt)
begin 1
3
2
1
4 3 end
This specifies a process that first reads page 1, then page 3, and so on until the ‘end’ is reached.
For each replacement strategy, the simulation should produce a summary showing, for each process, the turnaround time, the total number of page faults and the time the page faults were generated.
Sample inputs/outputs are provided. Working of the first example is presented with details of different levels for visualisation. Your submission will be tested with the above data and will also be tested with other input files.
Your program should output to standard output (this means output to the Console). Output should be strictly in the shown output format (see the supplied output files).
If output is not generated in the required format then your program will be considered incorrect.
Programming Language:
User Interface:
The output should be printed to the console, and strictly following the output samples given in the assignment package as separate files. You will lose marks if your program does not conform with the input/output formats.
Mark Distribution:
A general mark distribution can be found in the assignment feedback document
(Assign3Feedback.pdf); Note that this is a draft distribution and subject to change.
Submission Information for COMP2240 and COMP6240:
Deliverable:
1. Your submission will contain your source files and a readme.txt (containing any special instructions – this does not mean you are permitted to violate the following naming and running conventions) as well as your completed coversheet (PDF) and report (PDF), in the root of the submission. Zip these files and folder up into an archive called c12345678.zip (where c12345678 is your student number)- do not submit a .rar or a .7z etc.
2. Your main class should be A3.java, your program will compile with the command line javac A3.java and your program will be executed by running java A3 30 3 data1.txt data2.txt data3.txt (where data?.txt can be any relative filename and can be any number of files; see Input and Output above for description – do not hard code anything!).
3. Brief 1 page (A4) report (worth 10%) of how you tested your program and a comparison of the page replacement methods based on the results from your program and any interesting observations. Specifically, your report should include discussion on edge cases you considered and behaviour of your algorithm on those cases, any specific trick/technique you applied and did you face any specific issue.
4. Completed Assignment Coversheet.
NOTES
2. If your assignment is not prepared and submitted following above instructions then you will lose most of your marks despite your algorithms being correct – the specifications are not-negotiable!
