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AQuoSA
AQuoSA (Adaptive Quality of Service Architecture) is an open architecture for the provisioning of adaptive Quality of service, Quality of Service functionality into the Linux kernel. The project features a flexible, portable, lightweight and open architecture for supporting QoS related services on the top of a general-purpose operating system as Linux. The architecture is well founded on formal scheduling analysis and control theoretical results. A key feature of AQuoSA is the Resource Reservation layer that is capable of dynamically adapting the Central processing unit, CPU allocation for QoS aware applications based on their run time (program lifecycle phase), run-time requirements. In order to provide such functionality, AQuoSA embeds a kernel-level CPU Scheduling (computing), scheduler implementing a resource reservation mechanism for the CPU based on Earliest deadline first scheduling, Earliest Deadline First (EDF). This gives the ability to the Linux kernel to realize (partial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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] [Amazon] |
SCHED DEADLINE
SCHED_DEADLINE is a CPU scheduling (computing), scheduler available in the Linux kernel since version 3.14, Linux Weekly News, Deadline scheduling for Linux OSNews, Deadline Scheduling in the Linux Kernel based on the earliest deadline first (EDF) and constant bandwidth server (CBS) L. Abeni and G. Buttazzo, "Integrating multimedia applications in hard real-time systems," Proc. of the 19th IEEE Real-Time Systems Symposium, Madrid, 1998, pp.4-13 algorithms, supporting resource reservations: each task scheduled under such policy is associated with a ''budg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Open Architecture
Open architecture is a type of computer architecture or software architecture intended to make adding, upgrading, and swapping components with other computers easy. For example, the IBM PC, Amiga 2000 and Apple IIe have an open architecture supporting plug-in cards, whereas the Apple IIc computer has a closed architecture. Open architecture systems may use a standardized system bus such as S-100, PCI or ISA or they may incorporate a proprietary bus standard such as that used on the Apple II, with up to a dozen slots that allow multiple hardware manufacturers to produce add-ons, and for the user to freely install them. By contrast, closed architectures, if they are expandable at all, have one or two "expansion ports" using a proprietary connector design that may require a license fee from the manufacturer, or enhancements may only be installable by technicians with specialized tools or training. Computer platforms may include systems with both open and closed architectures. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Operating System
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for efficient use of the system and may also include accounting software for cost allocation of Scheduling (computing), processor time, mass storage, peripherals, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computerfrom cellular phones and video game consoles to web servers and supercomputers. , Android (operating system), Android is the most popular operating system with a 46% market share, followed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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] [Amazon] |
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] [Amazon] |
PREEMPT RT
PREEMPT_RT was a set of out-of-tree patches for the Linux kernel which implement both hard and soft real-time computing capabilities. On September 20, 2024, PREEMPT_RT was fully merged and enabled in mainline Linux on the supported architectures x86, x86_64, RISC-V and ARM64 AArch64, also known as ARM64, is a 64-bit version of the ARM architecture family, a widely used set of computer processor designs. It was introduced in 2011 with the ARMv8 architecture and later became part of the ARMv9 series. AArch64 allows .... This made kernel v6.12 the first release to include baked-in real-time capability. History The PREEMPT_RT patchset has been in development since 2005. In 2021, the preemption core locking code was merged. Since February 2023, Canonical has been releasing real-time versions of Ubuntu Pro, free for personal and small-scale commercial use in up to 5 machines. The real-time kernel can be added to various existing Ubuntu releases through an enablement process ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Video Player (software)
Media player software is a type of application software for playing multimedia computer files like audio and video files. Media players commonly display standard media control icons known from physical devices such as tape recorders and CD players, such as play ( ), pause ( ), fastforward (⏩️), rewind (⏪), and stop ( ) buttons. In addition, they generally have progress bars (or "playback bars"), which are sliders to locate the current position in the duration of the media file. Mainstream operating systems have at least one default media player. For example, Windows comes with Windows Media Player, Microsoft Movies & TV and Groove Music, while macOS comes with QuickTime Player and Music. Linux distributions come with different media players, such as SMPlayer, Amarok, Audacious, Banshee, MPlayer, mpv, Rhythmbox, Totem, VLC media player, and xine. Android comes with YouTube Music for audio and Google Photos for video, and s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Worst-case Execution Time
The worst-case execution time (WCET) of a computational task is the maximum length of time the task could take to execute on a specific hardware platform. What it is used for Worst case execution time is typically used in reliable real-time systems, where understanding the worst case timing behaviour of software is important for reliability or correct functional behaviour. As an example, a computer system that controls the behaviour of an engine in a vehicle might need to respond to inputs within a specific amount of time. One component that makes up the response time is the time spent executing the software – hence if the software worst case execution time can be determined, then the designer of the system can use this with other techniques such as schedulability analysis to ensure that the system responds fast enough. While WCET is potentially applicable to many real-time systems, in practice an assurance of WCET is mainly used by real-time systems that are related to h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Real-time Computing
Real-time computing (RTC) is the computer science term for Computer hardware, hardware and software systems subject to a "real-time constraint", for example from Event (synchronization primitive), event to Event (computing), system response. Real-time programs must guarantee response within specified time constraints, often referred to as "deadlines".Mordechai Ben-Ari, Ben-Ari, Mordechai; "Principles of Concurrent and Distributed Programming", ch. 16, Prentice Hall, 1990, , p. 164 The term "real-time" is also used in Computer simulation, 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 rela ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Admission Control
Admission control is a validation process in communication systems where a check is performed before a connection is established to see if current resources are sufficient for the proposed connection. Applications For some applications, dedicated resources (such as a wavelength across an optical network) may be needed in which case admission control has to verify availability of such resources before a request can be admitted. For more elastic applications, a total volume of resources may be needed prior to some deadline in order to satisfy a new request, in which case admission control needs to verify availability of resources at the time and perform scheduling to guarantee satisfaction of an admitted request. Admission control systems *Asynchronous Transfer Mode * Audio Video Bridging using Stream Reservation Protocol * Call admission control *IEEE 1394 * Integrated services on IP networks *Public switched telephone network The public switched telephone network (PSTN) is the a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
