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Earliest Eligible Virtual Deadline First Scheduling
Earliest eligible virtual deadline first (EEVDF) is a dynamic priority proportional share scheduling algorithm for soft real-time systems. Algorithm EEVDF was first described in the 1995 paper "Earliest Eligible Virtual Deadline First : A Flexible and Accurate Mechanism for Proportional Share Resource Allocation" by Ion Stoica and Hussein Abdel-Wahab. It uses notions of virtual time, eligible time, virtual requests and virtual deadlines for determining scheduling priority. It has the property that when a job keeps requesting service, the amount of service obtained is always within the maximum quantum size of what it is entitled. Linux kernel scheduler In 2023, Peter Zijlstra proposed replacing the Completely Fair Scheduler (CFS) in the Linux kernel with an EEVDF process scheduler. The aim was to remove the need for CFS "latency nice" patches. The EEVDF scheduler replaced CFS in version 6.6 of the Linux kernel. See also * Brain Fuck Scheduler * Earliest deadline first schedu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Priority Scheduling
Dynamic priority scheduling is a type of scheduling algorithm in which the priorities are calculated during the execution of the system. The goal of dynamic priority scheduling is to adapt to dynamically changing progress and to form an optimal configuration in a self-sustained manner. It can be very hard to produce well-defined policies to achieve the goal depending on the difficulty of a given problem. Earliest deadline first scheduling and Least slack time scheduling are examples of Dynamic priority scheduling algorithms. Optimal schedulable utilization The idea of real-time scheduling is to confine processor utilization under schedulable utilization of a certain scheduling algorithm, which is scaled from 0 to 1. Higher schedulable utilization means higher utilization of resource and the better the algorithm. In preemptible scheduling, dynamic priority scheduling such as earliest deadline first (EDF) provides the optimal schedulable utilization of 1 in contrast to less than 0 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scheduling Algorithm
In computing, scheduling is the action of assigning resources to perform tasks. The resources may be processors, network links or expansion cards. The tasks may be threads, processes or data flows. The scheduling activity is carried out by a mechanism called a scheduler. Schedulers are often designed so as to keep all computer resources busy (as in load balancing), allow multiple users to share system resources effectively, or to achieve a target quality-of-service. Scheduling is fundamental to computation itself, and an intrinsic part of the execution model of a computer system; the concept of scheduling makes it possible to have computer multitasking with a single central processing unit (CPU). Goals A scheduler may aim at one or more goals, for example: * maximizing ''throughput'' (the total amount of work completed per time unit); * minimizing '' wait time'' (time from work becoming ready until the first point it begins execution); * minimizing '' latency'' or '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soft Real-time
Real-time computing (RTC) is the computer science term for hardware and software systems subject to a "real-time constraint", for example from event to system response. Real-time programs must guarantee response within specified time constraints, often referred to as "deadlines". Ben-Ari, Mordechai; "Principles of Concurrent and Distributed Programming", ch. 16, Prentice Hall, 1990, , p. 164 The term "real-time" is also used in simulation to mean that the simulation's clock runs at the same speed as a real clock. Real-time responses are often understood to be in the order of milliseconds, and sometimes microseconds. A system not specified as operating in real time cannot usually ''guarantee'' a response within any timeframe, although ''typical'' or ''expected'' response times may be given. Real-time processing ''fails'' if not completed within a specified deadline relative to an event; deadlines must always be met, regardless of system load. A real-time system has been desc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ion Stoica
Ion Stoica (born ) is a Romanian–American computer scientist specializing in distributed systems, cloud computing and computer networking. He is a professor of computer science at the University of California, Berkeley and co-director of AMPLab. He co-founded Conviva and Databricks with other original developers of Apache Spark and Anyscale with other original developers of Ray. As of April 2025, Forbes ranked him and Matei Zaharia as the 3rd- richest people in Romania with a net worth of $2.7 billion. Education Stoica was born in Romania, where he grew up and attended Polytechnic University of Bucharest, receiving a MS in Electrical Engineering and Computer Science in 1989. He moved to the U.S. in 1994 to start a PhD at Old Dominion University with computer-science professor Hussein Abdel-Wahab. Together with Wahab, in 1995 he published the algorithm for earliest eligible virtual deadline first scheduling, which is the current process scheduler in the Linux kernel. In 1996 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Old Dominion Univ
Old or OLD may refer to: Places *Old, Baranya, Hungary *Old, Northamptonshire, England *Old Street station, a railway and tube station in London (station code OLD) *OLD, IATA code for Old Town Municipal Airport and Seaplane Base, Old Town, Maine, United States People *Old (surname) Music *OLD (band), a grindcore/industrial metal group * ''Old'' (Danny Brown album), a 2013 album by Danny Brown * ''Old'' (Starflyer 59 album), a 2003 album by Starflyer 59 * "Old" (song), a 1995 song by Machine Head *"Old", a 1982 song by Dexys Midnight Runners from ''Too-Rye-Ay'' Other uses * ''Old'' (film), a 2021 American thriller film *''Oxford Latin Dictionary'' *Online dating *Over-Locknut Distance (or Dimension), a measurement of a bicycle wheel and frame See also *Old age *List of people known as the Old *''Old LP'', a 2019 album by That Dog * * *Olde, a list of people with the surname *Olds (other) Olds may refer to: People * The olds, a jocular and irreverent online nick ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Completely Fair Scheduler
The Completely Fair Scheduler (CFS) was a process scheduler that was merged into the 2.6.23 (October 2007) release of the Linux Linux kernel, kernel. It was the default scheduler of the tasks of the SCHED_NORMAL class (i.e., tasks that have no real-time execution constraints) and handled central processing unit, CPU resource allocation for executing process (computing), processes, aiming to maximize overall CPU utilization while also maximizing interactive performance. In contrast to the previous O(1) scheduler used in older Linux 2.6 kernels, which maintained and switched Run queue, run queues of active and expired tasks, the CFS scheduler implementation is based on per-CPU run queues, whose nodes are time-ordered schedulable entities that are kept sorted by red–black trees. The CFS does away with the old notion of per-priorities fixed time-slices and instead it aims at giving a fair share of CPU time to tasks (or, better, schedulable entities). Starting from version 6.6 of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux Kernel
The Linux kernel is a Free and open-source software, free and open source Unix-like kernel (operating system), kernel that is used in many computer systems worldwide. The kernel was created by Linus Torvalds in 1991 and was soon adopted as the kernel for the GNU operating system (OS) which was created to be a free software, free replacement for Unix. Since the late 1990s, it has been included in many Linux distributions, operating system distributions, many of which are called Linux. One such Linux kernel operating system is Android (operating system), Android which is used in many mobile and embedded devices. Most of the kernel code is written in C (programming language), C as supported by the GNU compiler collection (GCC) which has extensions beyond standard C. The code also contains assembly language, assembly code for architecture-specific logic such as optimizing memory use and task execution. The kernel has a Modular programming, modular design such that modules can be inte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Process Scheduler
In computing, scheduling is the action of assigning resources to perform tasks. The resources may be processors, network links or expansion cards. The tasks may be threads, processes or data flows. The scheduling activity is carried out by a mechanism called a scheduler. Schedulers are often designed so as to keep all computer resources busy (as in load balancing), allow multiple users to share system resources effectively, or to achieve a target quality-of-service. Scheduling is fundamental to computation itself, and an intrinsic part of the execution model of a computer system; the concept of scheduling makes it possible to have computer multitasking with a single central processing unit (CPU). Goals A scheduler may aim at one or more goals, for example: * maximizing ''throughput'' (the total amount of work completed per time unit); * minimizing '' wait time'' (time from work becoming ready until the first point it begins execution); * minimizing '' latency'' or '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phoronix
Phoronix Test Suite (PTS) is a free and open-source benchmark software for Linux and other operating systems. The Phoronix Test Suite, developed by Michael Larabel and Matthew Tippett, has been endorsed by sites such as Linux.com, LinuxPlanet, and Softpedia. Features Phoronix Test Suite supports over 220 test profiles and over 60 test suites. It uses an XML-based testing architecture. Tests available to use include MEncoder, FFmpeg and lm sensors, along with OpenGL games such as '' Doom 3'', '' Nexuiz'', and '' Enemy Territory: Quake Wars'', and many more. The suite also contains a feature called PTS Global where users may upload their test results and system information for sharing. By executing a single command, other users can compare their test results to a selected system in an easy-comparison mode. Before 2014, these benchmark results could be uploaded to the Phoronix Global online database, but since 2013, these benchmark results can be uploaded topenbenchmarking. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brain Fuck Scheduler
The Brain Fuck Scheduler (BFS) is a process scheduler designed for the Linux kernel in August 2009 based on earliest eligible virtual deadline first scheduling (EEVDF), as an alternative to the Completely Fair Scheduler (CFS) and the O(1) scheduler. BFS was created by Con Kolivas. The objective of BFS, compared to other schedulers, is to provide a scheduler with a simpler algorithm, that does not require adjustment of heuristics or tuning parameters to tailor performance to a specific type of computational workload. Kolivas asserted that these tunable parameters were difficult for the average user to understand, especially in terms of interactions of multiple parameters with each other, and claimed that the use of such tuning parameters could often result in improved performance in a specific targeted type of computation, at the cost of worse performance in the general case. BFS has been reported to improve responsiveness on Linux desktop computers with fewer than 16 cores ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earliest Deadline First Scheduling
Earliest deadline first (EDF) or least time to go is a dynamic priority scheduling algorithm used in real-time operating systems to place processes in a priority queue. Whenever a scheduling event occurs (task finishes, new task released, etc.) the queue will be searched for the process closest to its deadline. This process is the next to be scheduled for execution. EDF is an ''optimal'' scheduling algorithm on preemptive uniprocessors, in the following sense: if a collection of independent ''jobs,'' each characterized by an arrival time, an execution requirement and a deadline, can be scheduled (by any algorithm) in a way that ensures all the jobs complete by their deadline, the EDF will schedule this collection of jobs so they all complete by their deadline. With scheduling periodic processes that have deadlines equal to their periods, EDF has a utilization bound of 100%. Thus, the schedulability test for EDF is: :U = \sum_^ \frac \leq 1, where the \left\ are the worst-case com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nice (Unix)
nice is a program found on Unix and Unix-like operating systems such as Linux. It directly maps to a kernel call of the same name. nice is used to invoke a utility or shell script with a particular CPU priority, thus giving the process more or less CPU time than other processes. A niceness of -20 is the lowest niceness, or highest priority. The default niceness for processes is inherited from its parent process and is usually 0. Systems have diverged on what priority is the lowest. Linux systems document a niceness of 19 as the lowest priority, BSD systems document 20 as the lowest priority. In both cases, the "lowest" priority is documented as running only when nothing else wants to. Etymology ''Niceness value'' is a number attached to processes in *nix systems, that is used along with other data (such as the amount of I/O done by each process) by the kernel process scheduler to calculate a process' 'true priority'which is used to decide how much CPU time is allocated t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
