114,147 research outputs found
Specification and Analysis of Resource-Bound Real-Time Systems
We describe a layered approach to the specification and verification of real-time systems. Application processes are specified in the CSR application language, which includes high-level language constructs such as timeouts, deadlines, periodic processes, interrupts and exception-handling. Then, a configuration schema is used to map the processes to system resources, and to specify the physical communication links between them. To analyze and execute the entire system, we automatically translate the result of the mapping into the CCSR process algebra. CCSR characterizes CSR\u27s resource-based computation model by a priority-sensitive, operational semantics, which yields a set of equivalence-preserving proof rules. Using this proof system, we perform the algebradc verification of our original real-time system
VERSA: A Tool for the Specification and Analysis of Resource-Bound Real-Time Systems
VERSA is a tool that assists in the algebraic analysis of real-time systems. It is based on ACSR, a timed process algebra designed to express resource-bound real-time distributed systems. VERSA supports the analysis of real-time processes through algebraic rewriting, interactive execution, and equivalence testing. This paper begins by presenting a brief overview of the process algebra ACSR, its syntax, operational semantics, and equivalence relations. VERSA\u27S process and command syntax, its algebraic rewrite system, and its state-based analysis features are described fully. The presentation includes examples that illustrate the salient features of ACSR, and output from sample VERSA sessions that demonstrate the application of the tool to real-time systems analysis
Towards Energy Consumption Verification via Static Analysis
In this paper we leverage an existing general framework for resource usage
verification and specialize it for verifying energy consumption specifications
of embedded programs. Such specifications can include both lower and upper
bounds on energy usage, and they can express intervals within which energy
usage is to be certified to be within such bounds. The bounds of the intervals
can be given in general as functions on input data sizes. Our verification
system can prove whether such energy usage specifications are met or not. It
can also infer the particular conditions under which the specifications hold.
To this end, these conditions are also expressed as intervals of functions of
input data sizes, such that a given specification can be proved for some
intervals but disproved for others. The specifications themselves can also
include preconditions expressing intervals for input data sizes. We report on a
prototype implementation of our approach within the CiaoPP system for the XC
language and XS1-L architecture, and illustrate with an example how embedded
software developers can use this tool, and in particular for determining values
for program parameters that ensure meeting a given energy budget while
minimizing the loss in quality of service.Comment: Presented at HIP3ES, 2015 (arXiv: 1501.03064
MorphoSys: efficient colocation of QoS-constrained workloads in the cloud
In hosting environments such as IaaS clouds, desirable application performance is usually guaranteed through the use of Service Level Agreements (SLAs), which specify minimal fractions of resource capacities that must be allocated for unencumbered use for proper operation. Arbitrary colocation of applications with different SLAs on a single host may result in inefficient utilization of the host’s resources. In this paper, we propose that periodic resource allocation and consumption models -- often used to characterize real-time workloads -- be used for a more granular expression of SLAs. Our proposed SLA model has the salient feature that it exposes flexibilities that enable the infrastructure provider to safely transform SLAs from one form to another for the purpose of achieving more efficient colocation. Towards that goal, we present MORPHOSYS: a framework for a service that allows the manipulation of SLAs to enable efficient colocation of arbitrary workloads in a dynamic setting. We present results from extensive trace-driven simulations of colocated Video-on-Demand servers in a cloud setting. These results show that potentially-significant reduction in wasted resources (by as much as 60%) are possible using MORPHOSYS.National Science Foundation (0720604, 0735974, 0820138, 0952145, 1012798
An Algebra of Synchronous Scheduling Interfaces
In this paper we propose an algebra of synchronous scheduling interfaces
which combines the expressiveness of Boolean algebra for logical and functional
behaviour with the min-max-plus arithmetic for quantifying the non-functional
aspects of synchronous interfaces. The interface theory arises from a
realisability interpretation of intuitionistic modal logic (also known as
Curry-Howard-Isomorphism or propositions-as-types principle). The resulting
algebra of interface types aims to provide a general setting for specifying
type-directed and compositional analyses of worst-case scheduling bounds. It
covers synchronous control flow under concurrent, multi-processing or
multi-threading execution and permits precise statements about exactness and
coverage of the analyses supporting a variety of abstractions. The paper
illustrates the expressiveness of the algebra by way of some examples taken
from network flow problems, shortest-path, task scheduling and worst-case
reaction times in synchronous programming.Comment: In Proceedings FIT 2010, arXiv:1101.426
A C-DAG task model for scheduling complex real-time tasks on heterogeneous platforms: preemption matters
Recent commercial hardware platforms for embedded real-time systems feature
heterogeneous processing units and computing accelerators on the same
System-on-Chip. When designing complex real-time application for such
architectures, the designer needs to make a number of difficult choices: on
which processor should a certain task be implemented? Should a component be
implemented in parallel or sequentially? These choices may have a great impact
on feasibility, as the difference in the processor internal architectures
impact on the tasks' execution time and preemption cost. To help the designer
explore the wide space of design choices and tune the scheduling parameters, in
this paper we propose a novel real-time application model, called C-DAG,
specifically conceived for heterogeneous platforms. A C-DAG allows to specify
alternative implementations of the same component of an application for
different processing engines to be selected off-line, as well as conditional
branches to model if-then-else statements to be selected at run-time. We also
propose a schedulability analysis for the C-DAG model and a heuristic
allocation algorithm so that all deadlines are respected. Our analysis takes
into account the cost of preempting a task, which can be non-negligible on
certain processors. We demonstrate the effectiveness of our approach on a large
set of synthetic experiments by comparing with state of the art algorithms in
the literature
The Epistemology of scheduling problems
Scheduling is a knowledge-intensive task spanning over many activities in day-to-day life. It deals with the temporally-bound assignment of jobs to resources. Although scheduling has been extensively researched in the AI community for the past 30 years, efforts have primarily focused on specific applications, algorithms, or 'scheduling shells' and no comprehensive analysis exists on the nature of scheduling problems, which provides a formal account of what scheduling is, independently of the way scheduling problems can be approached. Research on KBS development by reuse makes use of ontologies, to provide knowledge-level specifications of reusable KBS components. In this paper we describe a task ontology, which formally characterises the nature of scheduling problems, independently of particular application domains and in-dependently of how the problems can be solved. Our results provide a comprehensive, domain-independent and formally specified refer-ence model for scheduling applications. This can be used as the ba-sis for further analyses of the class of scheduling problems and also as a concrete reusable resource to support knowledge acquisition and system development in scheduling applications
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