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Operating System Articles
Page 133 of 171
Linear Scheduling Method in Operating System
Linear Scheduling Method (LSM) is a scheduling algorithm designed for real-time systems where tasks must be completed within specific time frames to ensure proper system operation. It assigns tasks based on their deadlines and provides them with fixed time slices to complete their execution. This straightforward algorithm arranges tasks in linear order and moves through the list sequentially. How Linear Scheduling Method Works Tasks in LSM are arranged in a linear queue, and the scheduler moves through the list, allocating fixed time slices to each task in turn. The length of each time slice is predetermined based on ...
Read MoreLinux System Call in Detail
A system call is a mechanism in Linux that allows user-space applications to interact with the kernel, which forms the core of the operating system. When a user-space application needs privileged operations performed—such as reading/writing files or creating new processes—it must request these services from the kernel through system calls. How Linux System Calls Work System calls are executed in kernel mode and accessed by user-space applications through standard C library functions like open(), read(), write(), close(), fork(), and exec(). System Call Execution Flow ...
Read MoreLock Variable Mechanism
A lock variable is a fundamental synchronization mechanism that controls access to shared resources in multi-threaded or multi-process environments. It acts as a simple data structure, typically implemented as a boolean or integer, that indicates whether a resource is currently in use or available for access. How Lock Variable Mechanism Works When a thread or process wants to access a shared resource, it first checks the lock variable's value. If the lock is free (unlocked), the thread can acquire it by setting the variable to busy (locked). This ensures mutual exclusion, allowing only one thread to access the ...
Read MoreLogical Clock in Distributed System
Logical clocks in distributed systems provide a way to order events across multiple machines that do not share synchronized physical clocks. Since each machine may have its own local clock running at different rates, logical clocks assign timestamps to events based on causality rather than actual time, creating a consistent virtual global timepiece across all machines in the system. The Need for Logical Clocks In distributed systems, establishing the order of events is crucial for maintaining consistency. Physical clocks on different machines may drift or run at different speeds, making it impossible to rely on wall-clock time for ...
Read MoreLRU Approximation (Second Chance Algorithm)
The LRU Approximation Algorithm, commonly known as the Second Chance Algorithm, is a page replacement algorithm used in operating systems for memory management. It provides an efficient approximation to the ideal Least Recently Used (LRU) algorithm while maintaining significantly lower overhead. This algorithm uses reference bits and a circular queue structure to make replacement decisions. How the Second Chance Algorithm Works The algorithm maintains pages in a circular queue and uses a single reference bit per page. When a page fault occurs, the algorithm searches for a victim page to replace using the following process: Start ...
Read MoreMaekawa\'s Algorithm for Mutual Exclusion in Distributed System
Multiple processes may require concurrent access to common resources in a distributed system. Concurrent access to a shared resource, however, may result in errors and inconsistencies. A distributed mutual exclusion algorithm must be employed to manage access to shared resources in order to guarantee mutual exclusion. Maekawa's Algorithm is a distributed mutual exclusion technique that ensures mutual exclusion between running processes in a distributed system. Only one process at a time can access a shared resource thanks to the algorithm, which is based on a voting system. How Maekawa's Algorithm Works The voting-based algorithm was proposed in ...
Read MoreMaster Boot Record
The Master Boot Record (MBR) is a critical 512-byte sector located at the very beginning of a storage device such as a hard disk drive or SSD. It contains essential information required to start the computer's boot process and load the operating system. The MBR consists of three main components: boot code, partition table, and disk signature. MBR Structure and Organization Master Boot Record (512 bytes) Boot Code (446 bytes) Partition Table (64 bytes) ...
Read MoreMeasure the time spent in context switch
Context switching is a fundamental mechanism in modern operating systems that enables multiple processes or threads to share CPU resources efficiently. When the OS switches from executing one process to another, it must save the current process state and load the state of the next process. This operation, called a context switch, takes time and affects overall system performance. Understanding the time spent in context switching is crucial for system optimization, performance tuning, and identifying bottlenecks in multitasking environments. Methods for Measuring Context Switch Time Several approaches can be used to measure the duration of context switches ...
Read MoreMemory Allocation Techniques | Mapping Virtual Addresses to Physical Addresses
Memory allocation techniques are fundamental mechanisms in operating systems that manage how programs access and use system memory. The mapping of virtual addresses to physical addresses is a crucial aspect that allows multiple processes to run simultaneously while maintaining memory protection and efficient resource utilization. Virtual addresses provide programs with an abstraction layer over physical memory locations. Programs use virtual addresses to access memory, while the operating system translates these to actual physical addresses in RAM where data is stored. Methods of Virtual to Physical Address Mapping There are several established methods for mapping virtual addresses to ...
Read MoreMemory ballooning in OS
Memory ballooning is a dynamic memory management technique used in virtualized environments to optimize memory allocation among virtual machines (VMs). It allows the hypervisor to reclaim unused memory from one VM and redistribute it to others that need more resources, preventing memory waste and improving overall system efficiency. How Memory Ballooning Works Memory ballooning operates through a special balloon driver installed in each guest VM that communicates with the hypervisor. The driver can artificially consume memory within the VM when the hypervisor needs to reclaim it, and release that memory back to the VM when resources become available ...
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