A Software Framework for Embedded Multi-Core Systems.ppt

A Software Framework for Embedded Multi-Core Systems

Taehyo Song

Real-Time Operating Systems Laboratory,

Seoul National University, Korea

2008-09-29

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OutlineOutline

Introduction Problem Definition and Solution Overview Framework for Embedded Multi-Core Systems Experimental Evaluation (not yet done) Conclusion


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Motivation (1)Motivation (1)

Multi-core systems are spreading to embedded areaHard to achieve higher clock rate because of the heat and power consumption problems

Power is very important factor in embedded systems

Introduction

Multi-core performance and power scenario

Performance and power1. Standard single-core processor

over-clocked 20%

2. Standard single-core processor

3. Dual-core processor each core under-clocked 20%

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Motivation (2)Motivation (2)

Developer need to be preparedCan’t take advantages from previous method

Use multi-threading technology to take advantages• Steep learning curve to learn multi-threaded programming

• Leading to deadlock and complex debugging scenarios

• Lengthy development time

Introduction

Gap between two classes of software developers

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OutlineOutline

Introduction Problem Definition and Solution Overview

Problems

Problem Definitions

Solution Overview

Framework for Embedded Multi-Core Systems Experimental Evaluation Conclusion


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Problems (1)Problems (1)

Existing technologies such as OMP, MPI, TBB support to develop parallel software

Cannot apply to embedded system since it has resource restrictions

Limitations of the automatic parallelization [1]

Problem Definition and Solution Overview

[1] Zhao-Hui Du, Chu-Cheow Lim, Xiao-Feng Li et al., “A Cost-Driven Compilation Framework for Speculative Parallelization of Sequential Programs, PLDI, 2004

Basic compilation Current best compilation Enabling optimization

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Problems (2)Problems (2)

Parallel design patterns can help developersLearning design patterns and particularly applying them is not an easy task [2]

Conversion from patterns to codes for implementation is not that straight forward and without proper guidance and coaching this process could create problems [3]


[1] Masita Abdul Jalil, Shahrul Azman Mohd Noah, “The Difficulties of Using Design Patterns among Novices: An Exploratory Study”, 2007[2] Ó Cinnéide, M. & Tynan R., “A Problem-Based Approach to Teaching Design Patterns”, 2004.

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Problem DefinitionProblem Definition

How to develop embedded software that is running on multi-core system easily and effectively in terms of development time and performance respectively


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Solution OverviewSolution Overview

Efficient use of design patterns by using frameworkReconstruct existing parallel design patterns to suit for framework and add to the framework


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OutlineOutline

Introduction Problem Definition and Solution Overview Framework for Embedded Multi-Core Systems

Embedded System Framework

Overview of the Apparatus Framework

Analysis the Apparatus Framework

Proposed Framework

Experimental Evaluation Conclusion


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Proposal FrameworkProposal Framework

Framework for Embedded Multi-Core SystemsModify modules of Apparatus Framework to suit for multi-core System

Improve existing parallel design patterns and reconstruct it to suit for framework, add to Apparatus Framework

Framework for Embedded Multi-Core Systems

Hardware

BSP

eCos OSE RTOS Linux uC/OS

Kernel

Pattern

Multi-Core

Pattern

RT_STL

Application

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Analysis of Apparatus Framework (1)Analysis of Apparatus Framework (1)

Several features are applicable for multi-thread programming

Inter-task Communication• Communication between tasks is generally performed by

asynchronous communication

Messages • A task reads messages and reacts according to the type and

content of this message

Resource Protection • A set of mechanisms to serialize access to shared resources is

provided: semaphores, mutexes, monitors and guards


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Analysis of Apparatus Framework (2)Analysis of Apparatus Framework (2)

Apparatus Framework is not designed for multi-core systems

Modules are not thread safe• Queue, State Machine, Device Accessing, Communication etc.

Pattern service does not provide patterns that are used for multi-core systems

• Task parallelization patterns

• Data parallelization patterns


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Thread Safety ModulesThread Safety Modules

Com, Device, RT-STL and Pattern modules are unsafe under concurrent operations

Attempting concurrent modifications could corrupt them

Solutionwrap a lock around container accesses

It does not cause any overhead when single thread is used since lock can be removed at development time using configuration tool

Modules Modification of Apparatus Framework

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Types of ParallelizationTypes of Parallelization

Parallelization generally falls between two polesTask Parallelization

• Task parallelization refers to the alternative scenario where several nodes may execute different algorithms on the same data source, or alternatively on several data sources [4]

Data Parallelization• Data parallelization refers to a given data source being

processed using the same technique on each node in the parallel architecture [5]

Parallel Design Patterns to Framework

[4] Akram Hameed, “Parallelization of the AAE algorithm”, 2007[5] Wilkinson, B, Allen M , “Parallel programming: techniques and applications using networked workstations and parallel computers”, Prentice-Hall, 1998

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Task Parallelization PatternsTask Parallelization Patterns

Task Parallel ModelThe program is split into a number of tasks

Each task is assigned to a specific core

PatternsThread Pool

Fork/Join Pattern

Pipeline Pattern


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Thread Pool Pattern (1)Thread Pool Pattern (1)

Thread PoolAllocate number of threads to thread pool

• A number of N threads are created to perform a number of M tasks (N << M)

• A thread completes its task, it will request the next task from the queue until all tasks have been completed

• The thread can then terminate, or sleep until there are new tasks available


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Conceptual Diagram



Task 1

Task Task Task Task

Task K Task M

Task 5

Task Queue

Thread Pool

Completed Tasks

Task Task Task Task

Thread

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Hot SpotTasks that will be assigned to thread

Scheduling policy of threads

Class Diagram


…

ThreadPoolManager

+Initialize()+AssignThread()+RemoveThread()

Client

0..*1

Task

+runBody()+virtual run()

SchedulingPolicy

+Policy()

1

1

SP1 SP2 UDSP

0..*1

ConcreteTask

+run()

ApparatusTask

+virtual runBody()

Queue

0..*1

1

1

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Fork/Join Pattern (1)Fork/Join Pattern (1)

Fork/JoinA main task forks off some number of other tasks that then continue in parallel to accomplish some portion of the overall work

• The fork operation starts a new parallel fork/join subtask

• The join operation causes the current task not to proceed until the forked subtask has completed


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Conceptual Diagram


Task

Thread

TaskTask

Task 1 Task 2.1

Task 2.2

Task

Thread 1 Thread 2

Fork

Join

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Hot SpotTasks that will be processed concurrently

Class Diagram


Fork/ J oinManager

+addTask()+fork()+join()

ConcreteTask

+run()

ApparatusTask

+virtual runBody()

FJTask


ThreadPoolManager


*1

Client

1

1..*

0..*1 *1

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Pipeline Pattern (1)Pipeline Pattern (1)

PipelineExecute tasks or group of tasks in regular sequence when the execution order of tasks is regular, one-way and static

• Enables the decomposition of a repetitive sequential process into a succession of distinguishable sub-processes

• Each of processes can be efficiently executed on a distinct processing element or elements which operate concurrently


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Conceptual Diagram


Input DataInput Data ClientClient

Task

Data

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Hot SpotSet of tasks that will be processed serially or concurrently

Class Diagram


PipelineManager

+virtual runBody()+addTask()+removeTask()

Queue

1

1

FJTask


ApparatusTask

+virtual runBody()

ConcreteTask

+run()

*1

ThreadPoolManager


1

1..*

Client

0..*1

0..*1 0..* 1

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Data Parallelization PatternsData Parallelization Patterns

Data Parallel ModelData is distributed over the cores

Each core works on a different part of the same data structure

PatternsSPMD Pattern


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SPMD Pattern (1)SPMD Pattern (1)

Single Program, Multiple DataThe same program is executed on different cores, over distinct data sets

Each task is characterized by the data over which the common code is executed


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Conceptual Diagram


Input DataInput Data ClientClient

Thread 1 Thread 2 Thread 3 Thread 4

Data

Task

Thread

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Hot SpotTask to be executed in separate threads

Load balancing policy

Class Diagram


…

SPMDManager

+Initialize()+SetTask()+Execute()

LoadBalancer

+DistributionPolicy()

1

1

LBP1 LBP2 UDLBP

Client

*1Task


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ConcreteTask

+run()

ApparatusTask

+virtual runBody()

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OutlineOutline

Introduction Problem Definition and Solution Overview Framework for Embedded Multi-Core Systems Experimental Evaluation Conclusion


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Experimental EvaluationExperimental Evaluation

Remaining this part as a future work Comparison results will be given

Using framework and NOT using framework• Throughput time when developing application that has same

functionalities

• Comparing with LOC (Lines-Of-Code)

Case-study is needed for evaluation

Experimental Evaluation

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OutlineOutline

Introduction Problem Definition and Solution Overview Framework for Embedded Multi-Core Systems Experimental Evaluation Conclusion


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ConclusionConclusion

New software framework for embedded multi-core systems

Framework provides parallel features for multi-core systems

Experimental evaluation will be givenShow that using new software framework gives good results

Conclusion

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ReferencesReferences

Ralph E. Johnson, “Frameworks=(Components+Patterns)”, 1997

Bruce Powel Douglass, “Real-Time Design Patterns: Robust Scalable Architecture for Real-Time Systems”, 2002

Timothy G. Mattson, Beverly A. Sanders, Berna L. Massingill, “Patterns for Parallel Programming”, 2004

Max Domeika, “Software Development for Embedded Multi-Core Systems”, 2008

A.Pastino, C.C.Ribeiro, N.Rodriguez, “Developing SPMD Applications with Load Balancing”, 2003

Michael A. Bender, Jeremy T. Fineman, Seth Gilbert et al., “On-the-Fly Maintenance of Series-Parallel Relationships in Fork-Join Multithreaded Programs”, 2004


Thank You!!!Thank You!!!

A Software Framework for Embedded Multi-Core Systems.ppt

Documents

apparatus framework

proposal framework framework

software framework

multicore systems modules

framework problem definition

guards framework

modules of apparatus

apparatus framework