nepiskopos / linux-tlb-addressing

Translation of logical addresses to physical addresses, using translation lookaside buffer (TLB).

On-demand paging

On-demand paging using translation lookaside buffer.

Description

This repository contains a very simple simulation of an on-demand paging system, insipred by Virtual Memory management system for Linux.

This simulation aims at performing virtual to physical memory address translation, utilizing a translation lookaside buffer (TLB).

We create a virtual memory space of addresses, a TLB of 16 entries, and a single-layer page table (we assume that the page table is of unlimited space).

Then, we read a series of logical addresses from the addresses file in which all addresses are stored as unsigned integer numbers and we convert then into physical addresses.

Every logical address consists of:

• an 8-bit page number
• an 8-bit offset (within the page)

After an address is read from the file, we search for it in the TLB. We consider the 2 following cases:

• Page fault. In this case, if the address does not exist in the page table, we open the binary content file, we read the corresponding page, we store it both in the TLB and the page table and we extract the signed byte which is stored in this physical address.
• Page hit. In this case, we just extract the signed byte which is stored in the corresponding physical address.

The TLB is updated using the Least Recently Used (LRU) policy.

For every logical address we read from the file, we print:

• The logical address read
• The physical address to which the logical address is translated
• The signed byte which is stored in the corresponding physical address

In the end, we print the following statistics:

• The page fault ratio
• The TLB hit ratio

Execution

In order to execute the software, use a Terminal Emulator and navigate to the src directory.

Then, to compile and build the software type the following command:

make

After you have successfully built the software, execute it using the following command:

./vmm DIRECTORY PAGE_TABLE_SIZE

where:

• DIRECTORY is the path to the directory which contains both the address file and the page file
• PAGE_TABLE_SIZE is the size of the page table and must be a positive power of 2 and at least equal to 256

For example, to execute the software using a the relative path to the default files directory and a page table of 512 frames, use the following command:

./vmm ../files 512