Principles of Operating Systems

CMSC 421 - Fall 2019

Homework 3

50 points total

Due by 11:59PM EST on Tuesday, December 10, 2019

No late submissions will be accepted for this assignment!

Please provide written responses to the following questions. Each response should be about a paragraph or two in length — there is no need to write us a book for each, just be sure to answer the question thoroughly. Each question is worth 10 points.

1. Describe the following types of directory structures for a filesystem, including listing pros and cons of each type: Tree-Structured, Acyclic Graph-Based, and General Graph-Based.
2. Describe what an inode is on a UNIX filesystem. Give several examples of pieces of data that would be stored in an inode.
3. Describe the process for doing an I/O over DMA in a modern system. Be sure to include how interrupts are used in the process.
4. Consider the following snapshot of a system's resource allocations:

       Allocation      Max       Available
        A B C D      A B C D      A B C D
   P0   0 0 1 2      0 0 1 2      1 5 2 0
   P1   1 0 0 0      1 7 5 0
   P2   1 3 5 4      2 3 5 6
   P3   0 6 3 2      0 6 5 2
   P4   0 0 1 4      0 6 5 6

   • Is the system as described in a safe state? If so, give an order that the processes could complete successfully. If not, describe why the system is not in a safe state.
   • If a request from P1 for (0, 4, 2, 0) comes in, can it be granted immediately? Show why or why not.
   (Question adapted from OSC 9e.)
5. Describe how the LRU algorithm for virtual memory page replacement works. Describe at least one way that LRU can be approximated with simpler hardware than a full implementation would require.

You must submit a PDF file of the answers to these questions on the Homework 3 assignment on Blackboard. You may prepare your responses in any word processing application of your choosing, but you must submit a PDF file. Do not submit Microsoft Word/Apple Pages/LibreOffice documents with your responses. You must convert to a PDF file before submitting or you will lose points.

Last modified Tuesday, 01-Sep-2020 18:43:34 EDT