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Predictable Interrupt Management and Scheduling in the Composite Component-based System
, 2008
"... This paper presents the design of user-level scheduling hierarchies in the Composite component-based system. The motivation for this is centered around the design of a system that is both dependable and predictable, and which is configurable to the needs of specific applications. Untrusted applicati ..."
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Cited by 12 (4 self)
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This paper presents the design of user-level scheduling hierarchies in the Composite component-based system. The motivation for this is centered around the design of a system that is both dependable and predictable, and which is configurable to the needs of specific applications. Untrusted application developers can safely develop services and policies, that are isolated in protection domains outside the kernel. To ensure predictability, Composite needs to enforce timing control over user-space services. Moreover, it must provide a means by which asynchronous events, such as interrupts, are handled in a timely manner without jeopardizing the system. Towards this end, we describe the features of Composite that allow user-defined scheduling policies to be composed for the purposes of combined interrupt and task management. A significant challenge arises from the need to synchronize access to shared data structures (e.g., scheduling queues), without allowing untrusted code to disable interrupts or use atomic instructions that lock the memory bus. Additionally, efficient upcall mechanisms are needed to deliver asynchronous event notifications in accordance with policy-specific priorities, without undue recourse to schedulers. We show how these issues are addressed in Composite, by comparing several hierarchies of scheduling polices, to manage both tasks and the interrupts on which they depend. Studies show how it is possible to implement guaranteed differentiated services as part of the handling of I/O requests from a network device while avoiding livelock. Microbenchmarks indicate that the costs of implementing and invoking user-level schedulers in Composite are on par with, or less than, those in other systems, with thread switches more than twice as fast as in Linux.
HIRES: a System for Predictable Hierarchical Resource Management
"... Abstract—This paper presents HIRES, a system structured around predictable, hierarchical resource management (HRM). Applications and different subsystems use customized resource managers that control the allocation and usage of memory, CPU, and I/O. This increased resource management flexibility ena ..."
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Cited by 10 (0 self)
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Abstract—This paper presents HIRES, a system structured around predictable, hierarchical resource management (HRM). Applications and different subsystems use customized resource managers that control the allocation and usage of memory, CPU, and I/O. This increased resource management flexibility enables subsystems with different timing constraints to specialize resource management around meeting these requirements. In HIRES, subsystems delegate the management of resources to other subsystems, thus creating the resource management hierarchy. In delegating the control of resources, the subsystem focuses on providing isolation between competing subsystems. To make HRM both predictable and efficient, HIRES ensures that regardless of a subsystem’s depth in the hierarchy, the overheads of resource usage and control remain constant. In doing so, HIRES encourages HRM as a fundamental system design technique. Results show that HIRES has competitive performance with existing systems, and that HRM naturally provides both strong isolation guarantees, and flexible and efficient subsystem control over resources. I.
Fitting linux device drivers into an analyzable scheduling framework
- In Proceedings of the 3rd Workshop on Operating Systems Platforms for Embedded Real-Time Applications
, 2007
"... API extensions and performance improvements to the Linux operating system now enable it to serve as a platform for a range of embedded real-time applications, using fixed-priority preemptive scheduling. Powerful techniques exist for analytical verification of application timing constraints under thi ..."
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Cited by 8 (1 self)
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API extensions and performance improvements to the Linux operating system now enable it to serve as a platform for a range of embedded real-time applications, using fixed-priority preemptive scheduling. Powerful techniques exist for analytical verification of application timing constraints under this scheduling model. However, when the application is layered over an operating system the operating system must be included in the analysis. In particular, the computational workloads due to device drivers and other internal components of the operating system, and the ways they are scheduled, need to match abstract workload models and scheduling polices that are amenable to analysis. This paper assesses the degree to which the effects of device drivers in Linux can now be modeled adequately to admit fixed-priority preemptive schedulability analysis, and what remains to be done to reach that goal.
Mutable Protection Domains: Towards a Component-based System for Dependable and Predictable Computing ∗
"... The increasing complexity of software poses significant challenges for real-time and embedded systems beyond those based purely on timeliness. With embedded systems and applications running on everything from mobile phones, PDAs, to automobiles, aircraft and beyond, an emerging challenge is to ensur ..."
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Cited by 6 (3 self)
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The increasing complexity of software poses significant challenges for real-time and embedded systems beyond those based purely on timeliness. With embedded systems and applications running on everything from mobile phones, PDAs, to automobiles, aircraft and beyond, an emerging challenge is to ensure both the functional and timing correctness of complex software. We argue that static analysis of software is insufficient to verify the safety of all possible control flow interactions. Likewise, a static system structure upon which software can be isolated in separate protection domains, thereby defining immutable boundaries between system and application-level code, is too inflexible to the challenges faced by real-time applications with explicit timing requirements. This paper, therefore, investigates a concept called ”mutable protection domains” that supports the notion of hardware-adaptable isolation boundaries between software components. In this way, a system can be dynamically reconfigured to maximize software fault isolation, increasing dependability, while guaranteeing various tasks are executed according to specific time constraints. Using a series of simulations on multidimensional, multiple-choice knapsack problems, we show how various heuristics compare in their ability to rapidly reorganize the fault isolation boundaries of a componentbased system, to ensure resource constraints while simultaneously maximizing isolation benefit. Our ssh oneshot algorithm offers a promising approach to address system dynamics, including changing component invocation patterns, changing execution times, and mispredictions in isolation costs due to factors such as caching. ∗ This material is based upon work supported by the National Science Foundation under Grant Numbers 0615153 and 0720464. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. 1
Software Architecture Challenges and Requirements for Transportation Cyber-Physical Systems
"... A new field of cyber-physical computing is now emerging, involving communication and processing of data exchanged between physical devices and systems. In the transportation cyber-physical system (CPS) domain, there are numerous challenges posed by avionics, automotive and rail applications. For exa ..."
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A new field of cyber-physical computing is now emerging, involving communication and processing of data exchanged between physical devices and systems. In the transportation cyber-physical system (CPS) domain, there are numerous challenges posed by avionics, automotive and rail applications. For example, in the rail industry, monitoring and communication services are becoming increasingly im-
Increasing Memory Utilization with Transient Memory Scheduling∗
"... Abstract—In addition to predictability, both reliability and security are increasingly important for embedded systems. To limit the scope of errant behavior in open and mixed criticality systems, a common approach is to raise isolation barriers between software components. However, this decentralize ..."
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Abstract—In addition to predictability, both reliability and security are increasingly important for embedded systems. To limit the scope of errant behavior in open and mixed criticality systems, a common approach is to raise isolation barriers between software components. However, this decentralizes memory man-agement across all system components. Memory is often cached and quickly accessible in each application. This paper introduces the TMEM system for increasing memory utilization while optimizing for application end-to-end constraints such as meeting deadlines. In addition to the traditional spatial multiplexing of memory, TMEM introduces the predictable temporal multiplexing of memory within caches in a system component, and memory scheduling to continually reallocate memory between components to best benefit the system. We find that TMEM is able to maintain the efficiency of caches, while also lowering both task tardiness and system memory requirements. I.
