Operating System Tutorial

Operating System Tutorial Types of Operating System Evolution of Operating System Functions of Operating System Operating System Properties Operating System Services Components of Operating System Needs of the Operating System

Operating Systems

Linux Operating System Unix Operating System Ubuntu Operating System Chrome Operating Systems Fedora Operating System MAC Operating System MS Windows Operating System Solaris Operating System Cooperative Operating System CorelDRAW Operating System CentOS FreeBSD Operating Systems Batch Operating System MS-DOS Operating System Commercial Mobile Operating Systems


Difference Between Multi-programming and Multitasking Difference between C-LOOK and C-SCAN Difference between Rotational Latency and Disk Assess Time Trap vs Interrupt Difference between C-SCAN and SSTF Difference between SCAN and FCFS Difference between Seek Time and Disk Access Time Difference between SSTF and LOOK Difference between Process and Program in the Operating System Difference between Protection and Security in Operating System

How To

How to implement Monitors using Semaphores How to Install a Different Operating System on a PC


What is Kernel and Types of Kernel What is DOS Operating System What is Thread and Types of Thread What is Process Scheduler and Process Queue What is Context Switching What is CPU Scheduling What is Producer-Consumer Problem What is Semaphore in Operating System Monitors in Operating System What is Deadlock What is Paging and Segmentation What is Demand Paging What is Virtual Memory What is a Long term Scheduler What is Page Replacement in Operating System What is BSR Mode What is Convoy Effect What is Job Sequencing in Operating System Why is it critical for the Scheduler to distinguish between I/O-bound and CPU-bound programs Why is there a Need for an Operating System


Process Management Process State Scheduling Algorithm FCFS (First-come-First-Serve) Scheduling SJF (Shortest Job First) Scheduling Round-Robin CPU Scheduling Priority Based Scheduling HRRN (Highest Response Ratio Next) Scheduling Process Synchronization Lock Variable Mechanism TSL Mechanism Turn Variable Mechanism Interested Variable Mechanism Deadlock Avoidance Strategies for Handling Deadlock Deadlock Prevention Deadlock Detection and Recovery Resource Allocation Graph Banker’s Algorithm in Operating System Fixed Partitioning and Dynamic Partitioning Partitioning Algorithms Disk Scheduling Algorithms FCFS and SSTF Disk Scheduling Algorithm SCAN and C-SCAN Disk Scheduling Algorithm Look and C-Look Disk Scheduling Algorithm File in Operating System File Access Methods in Operating System File Allocation Method Directory Structure in Operating System N-Step-SCAN Disk Scheduling Feedback Queue in Operating System Contiguous Memory Allocation in Operating System Real-time Operating System Starvation in Operating System Thrashing in Operating System 5 Goals of Operating System Advantages of Operating System Advantages of UNIX Operating System Bit Vector in Operating System Booting Process in Operating System Can a Computer Run Without the Operating System Dining Philosophers Problem in Operating System Free Space Management in Operating System Inter Process Communication in Operating System Swapping in Operating System Memory Management in Operating System Multiprogramming Operating System Multitasking Operating Systems Multi-user Operating Systems Non-Contiguous Memory Allocation in Operating System Page Table in Operating System Process Scheduling in Operating System Segmentation in Operating System Simple Structure in Operating System Single-User Operating System Two Phase Locking Protocol Advantages and Disadvantages of Operating System Arithmetic operations in binary number system Assemblers in the operating system Bakery Algorithm in Operating System Benefits of Ubuntu Operating System CPU Scheduling Criteria in Operating System Critical Section in Operating System Device Management in Operating System Linux Scheduler in Operating System Long Term Scheduler in Operating System Mutex in Operating System Operating System Failure Peterson's Solution in Operating System Privileged and Non-Privileged Instructions in Operating System Swapping in Operating System Types of Operating System Zombie and Orphan Process in Operating System 62-bit operating system Advantages and Disadvantages of Batch Operating System Boot Block and Bad Block in Operating System Contiguous and Non - Contiguous Memory Allocation in Operating System Control and Distribution Systems in Operations Management Control Program in Operating System Convergent Technologies in Operating System Convoy Effect in Operating System Copy Operating Systems to SSD Core Components of Operating System Core of UNIX Operating System Correct Value to return to the Operating System Corrupted Operating System Cos is Smart Card Operating System Cosmos Operating Systems Examples Generation of Operating System Hardware Solution in Operating System Process Control Block in Operating System Function of Kernel in Operating System Operating System Layers History of Debian Operating Systems Branches and Architecture of Debian Operating Systems Features and Packages of Debian Operating Systems Installation of Operating System on a New PC Organizational Structure and Development in Debian Operating Systems User Interface in Operating System Types Of Memory in OS Operating System in Nokia Multilevel Paging in OS Memory Mapping Techniques in OS Memory Layout of a Process in Operating System Hardware Protection in Operating System Functions of File Management in Operating System Core of Linux Operating System Cache Replacement Policy in Operating System Cache Line and Cache Size in Operating System What is Memory Mapping? Difference Between Network Operating System And Distributed Operating System What is the difference between a Hard link and a Soft Link? Principles of Preemptive Scheduling Process Scheduling Algorithms What is NOS? What is the Interrupt I/O Process? What is Time Sharing OS What is process termination? What is Time-Sharing Operating System What is Batch File File system manipulation What is Message-passing Technique in OS Logical Clock in Distributed System

Multilevel Paging in OS

Multilevel paging is a memory management method used in operating systems (OS) to manage memory more efficiently. The page table is partitioned into numerous levels with this approach, with each level having a subset of the page table entries.

The top-level data structure in multilevel paging is the page directory. It has a set number of entries, each pointing to a page table. Each page directory entry represents a page of virtual memory, which is usually 4 KB (Kilo Byte) in size. A control register in the CPU specifies the position of the page directory in physical memory.

Multilevel Paging in OS

The above diagram shows the multi-level page tables. The page table is the second-level data structure used in multilevel paging. It contains a fixed number of entries, each of which maps a virtual page to a physical page. Each entry in the page table represents a page of virtual memory, which is also typically 4 KB (Kilo Bytes) in size. The page table is in physical memory, and its location is specified by an entry in the page directory.

 When a process seeks access to a memory location, the central processing unit constructs a virtual address that includes a page number and an offset inside the page. The page number is used to index the page directory to find the entry matching the requested page. The page directory item gives the physical location of the page table for that page.

Once the page table is located, the CPU uses the offset within the virtual address to index into the page table to find the entry corresponding to the requested memory location. The page table entry contains the physical address of the memory location.

If the page table entry is invalid, the CPU generates a page fault, which is handled by the operating system. The operating system reads the data from the disk into a free page frame in physical memory, updates the page table entry, and restarts the instruction that caused the page fault.

Multilevel paging reduces the page table and the amount of memory needed to hold it. A 32-bit address space, for example, requires a page table with 2 power 20 (1048576) entries, which necessitates 4 MB of RAM. The page directory contains just 2 power 10 (1024) items with two-level paging, and each page table has 2 power 10 (1024) entries, using only 8 KB (Kilo Bytes) of memory.

Multilevel paging also allows for more efficient use of memory. Only the pages that are currently being used by a process need to be mapped to physical memory, while the rest of the pages can remain on the disk until they are needed. This allows more processes to run simultaneously without running out of physical memory.

However, multilevel paging also increases the overhead of memory access. The operating system needs to perform multiple memory lookups to translate a virtual address to a physical address, which can slow down the system. To minimize this overhead, modern CPUs use hardware-based translation look-aside buffers (TLBs) to cache recently used translations.

 Here's an example of multilevel paging in action in an operating system:

 Assume we have a process that requires 16 GB of memory. The operating system splits the virtual address space of the process into 4 KB (Kilo Bytes) pages. A piece page is broken further into smaller pages of 1 KB (Kilo Byte) apiece, resulting in a two-level paging system.

The page directory, which comprises a list of page tables, is the initial level of the paging structure. Each page directory entry corresponds to a page table, which holds the physical addresses of the page's smaller pages.

The page table, which holds a list of page entries, is the second level of the paging structure. Each page table item corresponds to a 1 KB (Kilo Byte) page and specifies the page's physical address.

When a process wants to access a memory address, the operating system finds the corresponding page directory entry and utilizes it to find the page table. The page table entry is then used to find the physical address of the required page.

Because it only needs to allocate memory for the pages that the process actually uses, multilevel paging allows the operating system to allocate and manage memory more efficiently. It also reduces the amount of memory needed to hold the page tables since the operating system may utilize smaller page tables for each page directory entry.


In conclusion, multilevel paging is a memory management method used by operating systems to handle huge amounts of memory. It involves partitioning a process's virtual address space into several pages, and each page is further divided into smaller pages, resulting in a hierarchical structure.

There are a few disadvantages to adopting tiered paging. The additional degree of indirection required to reach a memory address, for example, might result in greater overhead and longer access times. Overall, multilevel paging is a useful technique for managing large amounts of memory in operating systems, but it should be carefully considered in the context of the specific system requirements and trade-offs between performance, complexity, and memory usage.