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STEP: A Concomitant Protocol for Real Time Applications

WIRELESS PERSONAL COMMUNICATIONS 2022年第4期122卷 3795-3832页

作者： Pandey, Sarvesh Shanker, Udai MMM Univ Technol Dept Comp Sci & Engn Gorakhpur 273010 Uttar Pradesh India Banaras Hindu Univ Varanasi Uttar Pradesh India

In distributed real-time database system, utilizing a priority inheritance mechanism may help in reducing the priority inversion duration of a conflicting (and waiting) high priority transaction. However, mere integration of the priority inheritance scheme with classic 2PC is not enough and may lead to performance degradation. The two main problems that arise because of such integration are considerably longer 'priority-Inherit' message dissemination time and extra message overhead. In addition, the explosion of priority inheritance events in the system might lead to the increased miss percentage for high-priority transactions. To address the above-mentioned problems, a Sophisticated Time and message utilization centered priority inheritance (STEP) concomitant protocol is designed which brings down the overhead (time & message) by simply requiring of single round intelligent message transfer and eliminates priority de-boosting part of the general priority inheritance mechanism. Moreover, it also keeps a check on the no. of priority inheritance events occurrences with the help of real-time monitoring of priority inversions' percentage in the system and thereby makes sure that high priority transaction miss percentage does not increase in an uncontrolled manner. The extensive performance study suggests that STEP protocol performs considerably well compared to the existing state-of-the-art protocols.

关键词： Concurrency control Commit priority inversion Executing-committing conflict priority inheritance DRTDBS

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Task synchronization in reservation-based real-time systems

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IEEE TRANSACTIONS ON COMPUTERS 2004年第12期53卷 1591-1601页

作者： Lipari, G Lamastra, G Abeni, L Scuola Super SantAnna Retis Lab I-56100 Pisa Italy Telecom Italia Lab I-10148 Turin Italy Broadsat SRL I-51017 Pescia PT Italy

In this paper, we present the BandWidth inheritance (BWI) protocol, a new strategy for scheduling real-time tasks in dynamic systems, which extends the resource reservation framework to systems where tasks can interact through shared resources. The proposed protocol provides temporal isolation between independent groups of tasks and enables a schedulability analysis for guaranteeing the performance of hard real-time tasks. We show that BWI is the natural extension of the well-known priority inheritance Protocol to dynamic reservation systems. A formal analysis of the protocol is presented and a guarantee test for hard real-time tasks is proposed that takes into account the case in which hard real-time tasks interact with soft real-time tasks.

关键词： real-time scheduling dynamic system resource reservation priority inheritance constant bandwidth server

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Analysis and implementation of the multiprocessor bandwidth inheritance protocol

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REAL-TIME SYSTEMS 2012年第6期48卷 789-825页

作者： Faggioli, Dario Lipari, Giuseppe Cucinotta, Tommaso Ecole Normale Super Lab Specificat & Verificat F-94235 Cachan France PRES Universud Paris F-94235 Cachan France Scuola Super Sant Anna Real Time Syst Lab I-56124 Pisa Italy Alcatel Lucent Bell Labs Dublin Ireland

The Multiprocessor Bandwidth inheritance (M-BWI) protocol is an extension of the Bandwidth inheritance (BWI) protocol for symmetric multiprocessor systems. Similar to priority inheritance, M-BWI lets a task that has locked a resource execute in the resource reservations of the blocked tasks, thus reducing their blocking time. The protocol is particularly suitable for open systems where different kinds of tasks dynamically arrive and leave, because it guarantees temporal isolation among independent subsets of tasks without requiring any information on their temporal parameters. Additionally, if the temporal parameters of the interacting tasks are known, it is possible to compute an upper bound to the interference suffered by a task due to other interacting tasks. Thus, it is possible to provide timing guarantees for a subset of interacting hard real-time tasks. Finally, the M-BWI protocol is neutral to the underlying scheduling policy: it can be implemented in global, clustered and semi-partitioned scheduling. After introducing the M-BWI protocol, in this paper we formally prove its isolation properties, and propose an algorithm to compute an upper bound to the interference suffered by a task. Then, we describe our implementation of the protocol for the LITMUS (RT) real-time testbed, and measure its overhead. Finally, we compare M-BWI against FMLP and OMLP, two other protocols for resource sharing in multiprocessor systems.

关键词： Resource sharing Real-time Multiprocessors Resource reservation priority inheritance

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Preemptive transaction scheduling in hard real-time database systems

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JOURNAL OF SYSTEMS ARCHITECTURE 1997年第9期43卷 625-637页

作者： Lam, KW Hung, SL Department of Computer Science City University of Hong Kong 83 Tat Chee Avenue Kowloon Hong Kong

Hard real-time database systems (RTDBS) must provide a guarantee of meeting deadlines of transactions. Concurrent transaction accesses to shared data need to be synchronized in a serializable manner to ensure database consistency. Transaction blocking is needed to resolve data conflicts among transactions. This transaction blocking can be unbounded. Thus, transaction scheduling protocols for hard RTDBS must control a tight bound on the duration of a transaction blocking. In this paper, we present a new scheduling protocol that utilizes the operation semantics of transactions under the update-in-workspace model to enhance transaction preemptability, This protocol can alleviate the unnecessary transaction blocking problem associated with some other protocols. We show that this protocol has two important properties: single-blocking and deadlock-free. We devise a schedulability analysis which provides a better schedulability condition for systems using this protocol.

关键词： database systems real-time systems priority inheritance concurrency controls transaction scheduling

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Improving responsiveness of time-sensitive applications by exploiting dynamic task dependencies

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SOFTWARE-PRACTICE & EXPERIENCE 2018年第4期48卷 820-841页

作者： Cucinotta, Tommaso Abeni, Luca Lelli, Juri Lipari, Giuseppe Scuola Super Sant Anna ReTiS Lab Via G Moruzzi 1 I-56124 Pisa Italy ARM Ltd Cambridge CB1 9NJ England Univ Lille CNRS UMR 9189 CRIStAL F-59800 Lille France

In this paper, a mechanism is presented for reducing priority inversion in multiprogrammed computing systems. Contrary to well-known approaches from the literature, this paper tackles cases where the dependency relationships among tasks cannot be known in advance to the operating system. The presented mechanism allows tasks to explicitly declare aforementioned relationships, enabling the operating system scheduler to take advantage of such information and trigger priority inheritance, resulting in reduced priority inversion. We present the prototype implementation of the concept within the Linux kernel in the form of modifications to the standard Portable Operating System Interface (POSIX) condition variable code, along with an extensive evaluation, including a quantitative assessment of the benefits for applications making use of the technique and comprehensive overhead measurements. In addition, we present an associated technique for the theoretical schedulability analysis of a system using the new mechanism, which is useful to determine whether all tasks can meet their deadlines or not, in the specific scenario of tasks interacting only through remote procedure calls and under partitioned scheduling.

关键词： concurrent programming priority inheritance priority inversion real-time analysis real-time scheduling on Linux

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RACE: A Concurrency Control Protocol for Time-Constrained Transactions

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ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2020年第12期45卷 10131-10146页

作者： Pandey, Sarvesh Shanker, Udai MMM Univ Technol CSE Dept Gorakhpur Uttar Pradesh India

The two-phase locking with high priority (2PL-HP) protocol is a broadly used concurrency control protocol as it better handles the priority inversion problem. However, its performance might get degraded due to the inclusion of cyclic restart, deadlock, unnecessary abort, pseudo-priority inversion, and starvation. To overcome the above problems, this paper proposes a Reduction of long transactions starvation effect, Avoidance of deadlock and pseudo-priority inversion, and Conditional-restart for an Efficient resource utilization (RACE) concurrency control protocol. The RACE specifically aims at reducing the transaction miss percent by eliminating the following problems-deadlock through dividing the execution stage in the locking phase and processing phase, the cyclic restart through prejudging its occurrence, and the pseudo-priority inversion that may occur with an intermediate lock holder low priority cohort. Moreover, it reduces unnecessary transaction aborts through the utilization of the priority inheritance method and saves long transactions from being starved to some extent by ensuring fair chances of their completion. Simulation results confirm up to 11% improvement in transactions miss percent and up to 38% reduction in transactions' rollbacks in RACE protocol over 2PL-HP and extended 2PL-HP.

关键词： Distributed real-time transaction Pessimistic concurrency control protocol 2PL-HP priority inheritance

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RAPID: A real time commit protocol

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JOURNAL OF KING SAUD UNIVERSITY-COMPUTER AND INFORMATION SCIENCES 2022年第6期34卷 2916-2925页

作者： Pandey, Sarvesh Shanker, Udai MMM Univ Technol Comp Sci & Engn Dept Gorakhpur 273010 Uttar Pradesh India

A write transaction intending to access data already accessed by the group of transactions in read mode may starve. The situation may even become worse with the simultaneous occurrence of the priority inversion if the priority level of the requesting write transaction is higher than that of the highest priority lock holding read transaction from the group of transactions currently holding the conflicting data in read mode. A Reads-write Avoid starvation and priority Inversion period Declined (RAPID) commit protocol has been proposed that efficiently resolves the above problem by declining the priority inversion duration optimistically through lessening the number of reader transactions either requested or currently holding the conflicting data item in read mode by aborting some of them (if possible). The simulation results show that the RAPID outperforms 2PC and PIC protocol. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of King Saud University.

关键词： Concurrency control Commit processing priority inversion Executing-committing conflict priority inheritance Read-read access

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Global Real-Time Semaphore Protocols: A Survey, Unified Analysis, and Comparison 36

Global Real-Time Semaphore Protocols: A Survey, Unified Anal...

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IEEE 36th Real-Time Systems Symposium (RTSS)

作者： Yang, Maolin Wieder, Alexander Brandenburg, Bjoern B. Max Planck Inst Software Syst MPI SWS Kaiserslautern Germany Univ Elect Sci & Technol China Chengdu Peoples R China

ISBN: (纸本)9781467395076

All major real-time suspension-based locking protocols (or semaphore protocols) for global fixed-priority scheduling are reviewed and a new, unified response-time analysis framework applicable to all protocols is proposed. The newly proposed analysis, based on linear programming, is shown to be clearly preferable compared to all prior conventional approaches. Based on the new analysis, all protocols are directly compared with each other in a large-scale schedulability study. Interestingly, the priority inheritance Protocol (PIP) and the Flexible Multiprocessor Locking Protocol (FMLP), which are the two oldest and simplest of the considered protocols, are found to perform best.

关键词： global scheduling priority inheritance priority inversion real-time locking response-time analysis semaphores

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Several methods of design and implementation to solve priority inversion problem in μC/OS-II

Several methods of design and implementation to solve priori...

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6th International Conference on Intelligent Networks and Intelligent Systems (ICINIS)

作者： Wang Xibo Jin Shan Yang Zhongling Shenyang Univ Technol Sch Informat Sci & Engn Shenyang 110178 Peoples R China Shenyang Metro Co Ltd Mech & Elect Equipment Ctr Dept Commun & Signal Shenyang 110178 Peoples R China

ISBN: (纸本)9781479928088

Multi-task concurrent execution and resource sharing based on preemptive scheduling strategy may cause priority inversion phenomenon in real-time systems. priority inversion phenomenon is the significant reason of unpredictable errors in real-time system;serious continuous priority inversion phenomenon will lead to real-time system collapse. The paper analyzes the phenomenon and the cause of the phenomenon, puts forward several design and implementation methods to solve priority inversion problem suitable for various application scenarios in mu C/OS-II. A priority exchange method is proposed to improve priority inheritance protocol. The proposed method limit priority inversion phenomenon to one level. Theoretical analyses and experimental results indicate that the methods to solve the priority inversion problem in mu C/OS-II are concise and effective, provides reasonable technical means for the safe running of complex real-time applications in mu C/OS-II.

关键词： real-time system priority inversion priority inheritance priority ceiling priority exchange

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Resource Sharing in GPU-accelerated Windowing Systems

Resource Sharing in GPU-accelerated Windowing Systems

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17th IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS)

作者： Kato, Shinpei Lakshmanan, Karthik Ishikawa, Yutaka Rajkumar, Ragunathan (Raj) Carnegie Mellon Univ Dept Elect & Comp Engn Pittsburgh PA 15213 USA Univ Tokyo Dept Comp Sci Tokyo Japan

ISBN: (纸本)9780769543444

Recent windowing systems allow graphics applications to directly access the graphics processing unit (GPU) for fast rendering. However, application tasks that render frames on the GPU contend heavily with the windowing server that also accesses the GPU to blit the rendered frames to the screen. This resource-sharing nature of direct rendering introduces core challenges of priority inversion and temporal isolation in multi-tasking environments. In this paper, we identify and address resource-sharing problems raised in GPU-accelerated windowing systems. Specifically, we propose two protocols that enable application tasks to efficiently share the GPU resource in the X Window System. The priority inheritance with X server (PIX) protocol eliminates priority inversion caused in accessing the GPU, and the Reserve inheritance with X server (RIX) protocol addresses the same problem for resource-reservation systems. Our design and implementation of these protocols highlight the fact that neither the X server nor user applications need modifications to use our solutions. Our evaluation demonstrates that multiple GPU-accelerated graphics applications running concurrently in the X Window System can be correctly prioritized and isolated by the PIX and the RIX protocols.

关键词： Driver circuits Engines GPU GPU-accelerated windowing systems Graphics processing unit Protocols Real time systems Real-Time Scheduling Rendering (computer graphics) Resource Sharing Servers Windowing Systems X Window System X server protocol computer graphic equipment coprocessors graphics processing unit priority inheritance priority inversion rendering rendering (computer graphics) reserve inheritance resource sharing problem resource-reservation systems temporal isolation

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