Software simulation of Virtual Memory using Demand Paging Dharma Prakash Natarajan

1. Software simulation of Virtual Memory using Demand Paging Dharma Prakash Natarajan • Goals of the Project • Construct the Virtual Memory Elements: Memory, Disk, Page Table,TLB. • Generate the test program for matrix multiplication to create the address sequence. Row wise and column wise matrix multiplication reference strings are generated. • Find out the TLB miss ratio • Find out the Page fault ratio. • Vary the associativity, TLB and memory size and study the effects on TLB miss ratio and Page fault ratio • Study the effects of LRU, FIFO and Random replacement strategies on TLB miss ratio

2. High Level Picture

4. Program Basics • Disk is created as an array each holding a page • Memory is created as a vector of memory entries • Page table is created as a vector of page table entries. • Each page table entry contains valid bit, reference bit and dirty bit • TLB is created as vector of TLB sets • Each TLB contains a vector of TLB entries. • Each TLB entry contains valid, reference and dirty bits • Main simulates the process execution

5. Test Program Matrix multiplication Page 20 Page 21 Page 39 Page 40 Page 41 Page 59 Page 0 Page 1 Page 19 20 x 20 matrix 20 x 20 matrix 20 x 20 matrix Reference String for Row wise Matrix multiplication 0 20 0 21 0 22 0 23 0 24 0 25 0 26 0 27 0 28 0 29 Reference String for Column wise matrix multiplication 0 20 1 20 2 20 3 20 4 20 5 20 6 20 7 20 8 20 9 20

6. Results

11. Conclusion • Mostly expected results on associativity, replacement strategy • Test case not able to distinguish between FIFO and LRU • Simulates only once process. Could be extended for multiple processes. • Context switch. Page table for each process • Byte addressing could be used. • Can be used to simulate multiple levels of page tables.