Virtual Memory Manager

This is a simple virtual memory manager. It takes a sequence of page references as an input, as well as the number of available frames. It performs the placement of these pages to the available frames using the page replacement policy specified by the user.

The replacement policy used in this project are:

• FIFO (First-in-first-out)
• LFU (Least-frequently-used)
• LRU-STACK (Least-recently-used stack implementation)
• LRU-CLOCK ((Least-recently-used clock implementation – -second chance alg.).
• LRU-REF8 (Least-recently-used Reference-bit - Optimal Page Replacement Algorithm Implementation, using 8 reference bits)

The default will be FIFO.

OUTPUT

The final output should compare Optimal page replacement algorithm, and the performance of the replacement-policy chosen by the user in terms of number of page replacements for the given string.

$ virtualmem –f 10 –r LFU –i myinputfile
# of page replacements with LFU : 118
# of page replacements with Optimal : 85
% page replacement penalty using LFU : 38.8%
Total time to run LFU algorithm : 1214 msec
Total time to run Optimal algorithm : 1348 msec
LFU is 9.9% faster than Optimal algorithm.

Command Line Input

(Main file is : "virtualmem")

virtualmem [-h] [-f available-frames] [-r replacement-policy] [-i input_file]

• -h : Print a usage summary with all options and exit.
• -f available-frames : Set the number of available frames. By default it should be 5.
• -r replacement-policy : Set the page replacement policy. It can be either
  • FIFO (First-in-first-out)
  • LFU (Least-frequently-used)
  • LRU-STACK (Least-recently-used stack implementation)
  • LRU-CLOCK ((Least-recently-used clock implementation – second chance alg.).
  • LRU-REF8 (Least-recently-used Reference-bit Implementation, using 8 reference bits)
  • The default will be FIFO.
• -i input file : Read the page reference sequence from a specified file. If not given,the sequence should be read from STDIN (ended with ENTER).