55 research outputs found
A PTAS for assigning sporadic tasks on two-type heterogeneous multiprocessors
Consider the problem of determining a task-toprocessor assignment for a given collection of implicit-deadline sporadic tasks upon a multiprocessor platform in which there are two distinct kinds of processors. We propose a polynomialtime approximation scheme (PTAS) for this problem. It offers the following guarantee: for a given task set and a given platform, if there exists a feasible task-to-processor assignment, then given an input parameter, ϵ, our PTAS succeeds, in polynomial time, in finding such a feasible task-to-processor assignment on a platform in which each processor is 1+3ϵ times faster. In the simulations, our PTAS outperforms the state-of-the-art PTAS [1] and also for the vast majority of task sets, it requires significantly smaller processor speedup than (its upper bound of) 1+3ϵ for successfully determining a feasible task-to-processor assignment
Two protocols without periodicity for the global and preemptive scheduling problem of multi-mode real-time systems upon multiprocessor Platforms
We consider the problem of scheduling a multi-mode
real-time system upon identical multiprocessor platforms.
Since it is a multi-mode system, the system can change from
one mode to another such that the current task set is replaced
with a new task set. Ensuring that deadlines are met
requires not only that a schedulability test is performed on
tasks in each mode but also that (i) a protocol for transitioning
from one mode to another is specified and (ii) a schedulability
test for each transition is performed. We propose
two protocols which ensure that all the expected requirements
are met during every transition between every pair of
operating modes of the system. Moreover, we prove the correctness
of our proposed algorithms by extending the theory
about the makespan determination problem
Timing Analysis of Fixed Priority SelfSuspending Sporadic Tasks
27th Euromicro Conference on Real-Time Systems (ECRTS 2015), Lund, Sweden.Many real-time systems include tasks that need to suspend their execution in order to externalize some of their operations or to wait for data, events or shared resources. Although commonly encountered in real-world systems, study of their timing analysis is still limited due to the problem complexity. In this paper, we invalidate a claim made in one of the earlier works [1], that led to the common belief that the timing analysis of one self-suspending task interacting with non-self-suspending sporadic tasks is much easier than in the periodic case. This work highlights the complexity of the problem and presents a method to compute the exact worst-case response time (WCRT) of a self-suspending task with one suspension region. However, as the complexity of the analysis might rapidly grow with the number of tasks, we also define an optimization formulation to compute an upper-bound on the WCRT for tasks with multiple suspendion regions. In the experiments, our optimization framework outperforms all previous analysis techniques and often finds the exact WCRT
Analysis of self-interference within DAG tasks
6th Real-Time Scheduling Open Problems Seminar (RTSOPS 2015), Lund, Sweden.No abstract (2-pages paper) Few years ago, the frontier separating the real-time embedded domain from the high-performance computing domain was neat
and clearly defined. Nowadays, many contemporary applications no longer find their place in either category as they manifest
both strict timing constraints and work-intensive computational demands. The only way forward to cope with such orthogonal
requirements is to embrace the parallel execution programming paradigm on the emergent scalable and energy-efficient multicore/many-core
architecture
Methodologies for the WCET Analysis of Parallel Applications on Many-core Architectures
Euromicro Conference on Digital System Design (DSD 2015), Funchal, Portugal.There is an increasing eagerness to deploy and execute parallel applications on many-core infrastructures, pre- serving the time-predictability of the execution as required by real-time practices to upper-bound the response time of the embedded application. In this context, the paper discusses the application of the currently-available WCET analysis techniques and tools on such platforms and with highly parallel activities. After discussing the pros and cons of all different methodologies for WCET analysis, we introduce a new approach that is developed within the P-SOCRATES project
Real-time Parallel Applications on Many-core Architectures
Presented at INForum - Simpósio de Informática (INFORUM 2015). 7 to 8, Sep, 2015. Portugal.There is an increasing eagerness to deploy and execute parallel applications on manycore infrastructures,
preserving the time-predictability of the execution as required by real-timepractices to upper-bound the response time of the embedded application. In this context, thiscommunication describes the application of the currentlyavailable real-time analysis techniquesand tools on such platforms and with highly parallel activities, and presents the approach whichis being developed within the P-SOCRATES project
A Multi-DAG Model for Real-Time Parallel Applications with Conditional Execution
The 30th ACM/SIGAPP Symposium On Applied Computing (SAC 2015). 13 to 17, Apr, 2015, Embedded Systems. Salamanca, Spain.Owing to the current trends for higher performance and the
ever growing availability of multiprocessors in the embedded
computing (EC) domain, there is nowadays a strong push towards
the parallelization of modern embedded applications.
Several real-time task models have recently been proposed
to capture different forms of parallelism. However, they do
not deal explicitly with control flow information as they assume
that all the threads of a parallel task must execute
every time the task is activated. In contrast, in this paper,
we present a multi-DAG model where each task is characterized
by a set of execution flows, each of which represents
a different execution path throughout the task code and is
modeled as a DAG of sub-tasks. We propose a two-step solution
that computes a single synchronous DAG of servers
for a task modeled by a multi-DAG and show that these
servers are able to supply every execution flow of that task
with the required cpu-budget so that the task can execute
entirely, irrespective of the execution flow taken at run-time,
while satisfying its precedence constraints. As a result, each
task can be modeled by its single DAG of servers, which
facilitates in leveraging the existing single-DAG schedulability
analyses techniques for analyzing the schedulability of
parallel tasks with multiple execution flows
Timing Analysis Methodology
This chapter focuses on the analysis of the timing behavior of software applications that expose real-time (RT) requirements. The state-of-the-art methodologies to timing analysis of software programs are generally split into four categories, referred to as static, measurement-based, hybrid, and probabilistic analysis techniques. First, we present an overview of each of these methodologies and discuss their advantages and disadvantages. Next, we explain the choices made by our proposed methodology in Section 5.2 and present the details of the solution in Section 5.3. Finally, we conclude the chapter in Section 5.4 with a summary.info:eu-repo/semantics/publishedVersio
A tighter analysis of the worst-case endto- end communication delay in massive multicores
"Many-core” systems based on the Network-on-
Chip (NoC) architecture have brought into the fore-front various
opportunities and challenges for the deployment of real-time
systems. Such real-time systems need timing guarantees to be
fulfilled. Therefore, calculating upper-bounds on the end-to-end
communication delay between system components is of primary
interest. In this work, we identify the limitations of an existing
approach proposed by [1] and propose different techniques to
overcome these limitations
Partitioned scheduling of multimode systems on multiprocessor platforms: when to do the mode transition?
Systems composed of distinct operational modes are a common necessity for embedded applications with strict timing
requirements. With the emergence of multi-core platforms protocols to handle these systems are required in order to
provide this basic functionality.In this work a description on the problems of creating an effective mode-transition
protocol are presented and it is proven that in some cases previous single-core protocols can not be extended to handle
the mode-transition in multi-core
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