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7/27/2014 Operating Systems with Lab… 1/3

Lab 4 of 7: Main Memory Allocation – Part 1 of 2 (50 Points)

Click here to open the instructions to access the Linux environment.

Main Memory Allocation – Part 1 of 2

The objective of this week’s lab is to simulate and evaluate different memory allocation/deallocation techniques (first fit, next fit, best fit,

and worst fit)when a linked list is used to keep track of memory usage. You will implement a separate Memory component for TWO

of the four memory allocation/deallocation techniques. This lab is designed to be completed in two weeks. One

allocation/deallocation technique is due on Week 4, and the second technique is due on Week 5.


Submit your assignment to the Dropbox located on the silver tab at the top of this page.

(See the Syllabus section “Due Dates for Assignments & Exams” for due dates.)

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Accessing the Linux Environment

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Assume that the memory is 256 KB and is divided into units of 2 KB each. A process may request between 3 and 10 units of memory.

Your simulation consists of three components: a Memory component that implements a specific allocation/deallocation technique, a

request generation component that generates allocation/deallocation requests, and a statistics reporting component that prints out the

relevant statistics. The Memory component exports the following functions:

1. int allocate_mem(int process_id, int num_units): allocates num_units units of memory to a process whose id is

process_id. If successful, it returns the number of nodes traversed in the linked list. Otherwise, it returns -1.

2. int deallocate_mem(int process_id): deallocates the memory allocated to the process whose ID is process_id. It returns 1,

if successful, otherwise “1.

3. int fragment_count( ): returns the number of holes (fragments of sizes 1 or 2 units).

The request generation component generates allocation and deallocation requests. For allocation requests, the component specifies the

process ID of the process for which memory is requested as well as the number of memory units being requested. For this simulation,

assume that memory is requested for each process only once. For deallocation requests, the component specifies the process ID of the

process whose memory has to be deallocated. For this simulation, assume that the entire memory allocated to a process is deallocated on

a deallocation request. You may generate these requests based on some specific criteria, e.g., at random or from a memory

allocation/deallocation trace obtained from some source.

There are three performance parameters that your simulation should calculate for the chosen two techniques: average number of external

fragments, average allocation time in terms of the average number of nodes traversed in allocation, and the percentage of times an

allocation request is denied.

Generate 10,000 requests using the request generation component, and for each request, invoke the appropriate function of the Memory

component for each of the memory allocation/deallocation techniques. After every request, update the three performance parameters for

each of the techniques. The statistics reporting component prints the value of the three parameters for the two techniques at the end.

You will submit four separate files to the dropbox for Week 4:

1. C or C++ program (source code)

2. Executable file (object)


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3. Instructions to execute the program

4. Analysis of the results for the chosen allocation/deallocation technique

The program for the main memory allocation/deallocation for the first chosen technique is due this week. This program is to be written in

C or C++ programming language on a Linux environment. The second technique is due on Week 5.

IMPORTANT: Please make sure that any questions or clarification about these labs are addressed early.

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