MemoryAllocationSimulation

Demonstration of different memory allocation algorithms

Compiling

In the linux terminal, go to the directory of the program and run the command "gcc holes.c -o holes"

Running the program

Run the program using ./holes INPUTFILE

INPUTFILE must be a properly formated file, it is required to run the program.

Using the simulator

The simulator takes no user input during run time. The simulator uses the following algorithms in order to allocate memory: First Fit Best Fit Worst Fit Next Fit

The simulator prints when a process is added to the memory, as well as the number of holes, number of processes, memory usage and cumulative memory usage When the ready queue is empty, the simulator will print the final statistics

Design

The simulator uses a linked list to create a ready queue of processes The main memory is set at 128MB and it assumes all processes are an integer value The main memory is represented by a doubly linked list of processes. Empty memory is stored as emptry process structs When a process is removed from the memory to create space, holes before and after the process will be merged to create a single hole After one of the algorithms has run, all variables are reset for the next algorithm

First fit

• finds first hole of the appropriate size
• adds process to memeory, creates hole if there is remaining room
• if there isn't enough space, remove the oldest process

Best fit

• first hole of appropriate size is chosen as best fit
• if a more optimal hole is found, that becomes the best fit hole
• adds process to best fit hole
• if there isn't enough space, remove oldest process

Worst fit

• first hole of appropriate size is chosen as worst fit
• if a less optimal hole is found, that becomes the worst fit hole
• adds process to worst fit hole
• if there isn't enough space, remove oldest process

Next fit

• starts at last inserted process, searches for a hole that fits
• if no hole is found after that process, a search from the begining of the memeory will look for a hole until the entire memeory is searched
• if no hole is found, remove oldest process

Limitations

The '!' character cannot represent a process name, it is reserved to represent a hole.

References

1. C Program of priority queue using linked list Author: Animesh Shaw Publication date: September 22, 2012 URL: https://codeitaway.wordpress.com/2012/09/22/c-program-of-priority-queue-using-linked-list/ Code referenced for linked list implementation. Lines: 667-750
2. Program to copy one linked list into another using recursion Author: Jackson Bouchard URL: http://www.dailyfreecode.com/code/copy-linked-list-another-recursion-2824.aspx Code referenced and modified for copying linked list. Lines: 645-659