Outstanding Paper Award: Schedulability Analysis of the Linux Push and Pull Scheduler with Arbitrary Processor Affinities

Gujarati, Arpan; Cerqueira, Felipe; Brandenburg, Björn B.

doi:10.1109/ecrts.2013.18

Cited by 13 publications

(13 citation statements)

References 25 publications

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“…Case in point: while Linux, QNX, and many other commercial real-time OSs offer flexible scheduling APIs that allow specifying arbitrary processor affinities [28], they default to global scheduling.…”

Section: A Motivation: the Case For Global Schedulingmentioning

confidence: 99%

Scaling global scheduling with message passing

Cerqueira

Vanga

Brandenburg

2014

2014 IEEE 19th Real-Time and Embedded Technology and Applications Symposium (RTAS)

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Abstract-Global real-time schedulers have earned the reputation of scaling poorly due to the high runtime overheads involved in global state management. In this paper, two mature implementations, one using fine-grained locking (SCHED DEADLINE) and one using coarse-grained locking (LITMUS RT 's G-EDF plugin), are evaluated and it is shown that, regardless of locking granularity, indeed neither scales well w.r.t. worst-case overheads due to excessive lock contention. To demonstrate that this is not an inherent limitation of global scheduling, the design of G-EDF-MP is presented, a global scheduler that uses message passing to avoid lock contention and cache-line sharing. It is shown to offer up to a 23-to 36-fold reduction in worst-case scheduling overhead on a 64-core platform, which translates into much improved schedulability (in some cases, more than 120 additional tasks can be supported).

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Section: A Motivation: the Case For Global Schedulingmentioning

confidence: 99%

Scaling global scheduling with message passing

Cerqueira

Vanga

Brandenburg

2014

2014 IEEE 19th Real-Time and Embedded Technology and Applications Symposium (RTAS)

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“…The other mean by which a task can be restricted to execute on a subset of CPUs is called task affinity . Although Gujarati et al already studied admission control for Arbitrary Processor Affinities , affinity setting is currently disabled for tasks handled by our scheduler because of the complexity of the admission control.…”

Section: Sched_deadlinementioning

confidence: 99%

Deadline scheduling in the Linux kernel

et al. 2015

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During the last decade, there has been a considerable interest in using Linux in real-time systems, especially for industrial control. The simple and elegant design of Linux guarantees reliability and very good performance, while its open-source license allows to modify and change the source code according to the user needs. However, Linux has been designed to be a general-purpose operating system. Therefore, it presents some issues like unpredictable latencies and limited support for real-time scheduling. In this paper, we present our experience in the design and implementation of the real-time scheduler that has been recently included in the Linux kernel. The scheduler is based on the Resource Reservation paradigm, which allows to enforce temporal isolation between the running tasks. We describe the genesis of the project, the challenges we have encountered, the implementation details and the API offered to the programmers. Then, we show the experimental results measured on a real hardware.has concerned the optimization of the average throughput (i.e. the amount of 'useful work' performed by the system in the unit of time) instead of meeting the timing constraints of each running application. As a result, the standard Linux kernel does not provide good real-time performance (i.e. low kernel latencies) or other features needed for supporting real-time applications (for example, advanced scheduling / resource management algorithms).In this paper, we describe a real-time scheduler for the CPU that we have recently included in Linux. The paper is organized as follows. In Section 2, we present the previous work about real-time on Linux. In Section 3, we describe the scheduling algorithm, the implementation details as well as the API offered to the programmer. Then, in Section 4, we provide some experimental results on a real hardware. Finally, in Section 5, we state our conclusions and we provide information about the future work. RELATED WORKIn the last decade, several (sometimes orthogonal) mechanisms have been proposed to add real-time capabilities to the Linux kernel. These mechanisms can be grouped in the following classes [1].Hardware Abstraction Layers (HALs). The first technique consists on reducing the kernel latency through a small abstraction layer (also called hypervisor), which virtualizes the hardware exposed to the Linux kernel [2]. This layer takes full control of the hardware resources (mainly, interrupts and system timers) and directly handles the real-time tasks at a higher priority than Linux. The Linux kernel is thus scheduled by the HAL as a low-priority task. The real-time applications cannot use functionalities provided by the Linux kernel, unless by temporarily loosing their real-time guarantees.This approach, originally introduced by Finite State Machine Labs with real-time Linux (RTLinux) [3], then acquired by Wind River [4], is now provided by two community-driven projects. The Real-Time Application Interface (RTAI) project [5], started in 1997, has developed the Adeos kernel [6] as a rep...

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“…In recent years, the researchers focused on another type of approaches, which we refer to as the arbitrary-partitioned approaches (e.g. LMM [23], APA [18]). In these approaches, each task has a set of cores where it is allowed to migrate to.…”

Section: Related Workmentioning

confidence: 99%

Hard Real-Time Multiprocessor Scheduling Resilient to Core Failures

Nikolic

Bletsas

Petters

2015

2015 IEEE 21st International Conference on Embedded and Real-Time Computing Systems and Applications

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Most multiprocessor scheduling theory overlooks the possibility of hardware failures that entirely nullify the computation carried out by a task instance, and potentially also make the respective processor henceforth unusable. Yet, such failures may occur, causing the system to fail. Motivated by this reality, we introduce a new concept of hard real-time schedulability guarantees for critical multiprocessor systems and analysis for their derivation. Namely, all deadlines must be met, even in the event of a core failure. A scheduling approach, based on global fixed priorities, and accompanying analysis, for achieving such guarantees are then formulated.

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Outstanding Paper Award: Schedulability Analysis of the Linux Push and Pull Scheduler with Arbitrary Processor Affinities

Cited by 13 publications

References 25 publications

Scaling global scheduling with message passing

Scaling global scheduling with message passing

Deadline scheduling in the Linux kernel

Hard Real-Time Multiprocessor Scheduling Resilient to Core Failures

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