Inverted Page Tables: Optimizing Virtual Memory Management

Explore inverted page tables, a memory management technique designed to improve efficiency compared to traditional page tables. This tutorial explains how inverted page tables work, their advantages in reducing memory usage, and the trade-offs involved, including increased search overhead for address translation.

Inverted Page Tables in Memory Management

Addressing Page Table Inefficiencies

Traditional paging systems use a separate page table for each process. For systems with many processes, this can consume significant memory. Furthermore, page tables themselves need to be accessed to translate virtual addresses (used by programs) into physical addresses (actual RAM locations), introducing overhead and slowing memory access. Inverted page tables are a technique designed to reduce this overhead and improve memory efficiency.

How Inverted Page Tables Work

An inverted page table has one entry for each frame (a block) in physical memory, rather than one for each page in each process. Each entry stores the process ID and the virtual page number associated with that frame. This eliminates the need for individual page tables for each process.

To translate a virtual address, the OS searches the inverted page table for the entry matching the process ID and page number. The corresponding frame number provides the physical address.

Diagram illustrating an inverted page table

Advantages of Inverted Page Tables

  • Reduced Memory Usage: The size of the page table is significantly reduced, as it does not require maintaining separate tables for each process.
  • Simplified Management: Managing and updating the table is less computationally intensive.

Disadvantages of Inverted Page Tables

Inverted page tables, while improving memory efficiency, introduce complexities to searching the page table. Finding the physical address for a virtual address now involves searching the entire inverted page table for the matching process ID and page number. This can add significant time overhead and makes it unsuitable for some operating systems.