基于模型的多媒体应用性能和功耗预测

PTAS004

Shi Steven, 资深固件工程师，英特尔 Cremer Illia , 系统建模工程师，英特尔

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议程

• 问题介绍和设计挑战

• 方案 – 系统级建模

• 负载建模与时钟分析

• 平台/体系结构建模与功耗预测

• 总结/问答

本课程演示文稿（PDF）发布在技术课程目录网站: intel.com/go/idfsessionsBJ 该网址同时打印于会议指南中专题讲座日程页的上方

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议程

• 问题介绍和设计挑战

• 方案 – 系统级建模

• 负载建模与时钟分析

• 平台/体系结构建模与功耗预测

• 总结/问答

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问题介绍和设计挑战

• 最大化利用多核能力 – 并行化与任务同步是关键

– 难以在实现阶段解决

• 片上系统（SoC）开发中集成众多IP核

– IP核有不同的格式和接口

• 预测系统性能

– 识别性能瓶颈并监测其产生原因

– 在确定体系结构设计前，尽量早地做系统级仿真

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设计挑战 - 约束

• 功耗限制 – 能耗始终是设计的关键要素

– 必须在早期设计就考虑如何优化

• 上市时间

– 越来越多的功能和服务集成在了一起

– 开发的周期必须可控

– 一个星期的推迟也会造成巨大的损失

• 成本

– 开发硬件原型非常昂贵

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方案需求

现有设计工具需要调整以应对系统设计挑战

快速仿真（仿真更多的应用场景&交互）

硬件与软件分离建模

与已有的代码和工具集成

激发创新（新功能&服务）

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议程

• 问题介绍和设计挑战

• 方案 – 系统级建模

• 负载建模与时钟分析

• 平台/体系结构建模与能耗预测

• 总结/问答

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方案 – 系统级建模

• 快速仿真（仿真更多的应用场景&交互） – 提高抽象层次，从周期准确级（Cycle-Accurate）上升到事务处理级（Transaction-Level Models）

• 硬件与软件分离建模

– 软硬件分离建模，并仿真出软件在具体平台上运行的情形

• 与已有的代码和工具集成

– 使用SystemC来轻松集成C/C++算法

• 激发创新（新功能&服务）

– 无需依赖预先定义的组件

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Intel® CoFluent™ Studio

• 建模与仿真框架

• 输入：

– 图：基于UML/SysML或Intel® CoFluent™标记图

– C/C++代码：算法和数据类型定义

– 时钟参数、注释

• 输出：

– 自动生成SystemC事务处理级代码并注入插桩

• 行为和性能的分析工具

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用途

• 早期设计中体系结构探索与性能分析

• 项目成员中共享可演示执行的规范

• 加快创建虚拟平台的设备模型

• 在验证环境中重用SystemC代码

通过支持早期设计中体系结构的探索， Intel® CoFluent™ Studio解决了设计中的主要挑战

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议程

• 问题介绍和设计挑战

• 方案 – 系统级建模

• 负载建模与时钟分析

• 平台/体系结构建模与能耗预测

• 总结/问答

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负载建模

• 依据以下方式来对负载和使用案例建模： – UML/SysML – Intel® CoFluent™图形记号

• 一体化视图：控制流和数据流

• 并行与层次结构描述

• 注意：负载建模是完全独立于运行平台的

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时钟与C/C++代码

• 加入各个功能的运行时间来分析系统性能

• 加入了C/C++结构来定义交互数据的类型

• 行为 VS. 功能

– 行为模型：没有C/C++/Matlab 代码的算法，只有以图示标号为基础的建模

– 功能模型：使用C/C++/Matlab 代码来刻画算法，并处理真实数据

• SystemC代码生成并支持在多个工具环境中编译使用

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多媒体应用实例

• 负载建模

– 音频/视频的解码和播放

Video Player

Sce

nari

o Con

trol

ler

Audio Player

Audio Source

MP3 Decoder

Video Source

Video Processing

Video Decoder

Video Display

Video Output

Audio Output

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多媒体播放器负载

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不同功能的函数有不同程度的并行定义

多媒体播放器负载

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不同的同步关系使用不同类型的同步定义

多媒体播放器负载

不同功能的函数有不同程度的并行定义

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在操作模块中定义C/C++算法

多媒体播放器负载

不同功能的函数有不同程度的并行定义

不同的同步关系使用不同类型的同步定义

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负载模型仿真

在没有具体平台约束的情况下使用负载模型来做功能上的验证仿真

在仿真中评测延时、死锁、缓冲和流水线设计

Timelines “y=f(t)” charts

“y=f(x)” charts Tables

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议程

• 问题介绍和设计挑战

• 方案 – 系统级建模

• 负载建模与时钟分析

• 平台/体系结构建模与能耗预测

• 总结/问答

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平台/体系结构建模与能耗预测

• 负载模型有不少优点，但它是基于“完美世界”的仿真…

– 没有调度的约束

– 没有并发的约束

– 没有资源共享的约束

• 平台与体系结构的模型是用来定义约束和可用资源的

• 平台的模型是独立于负载模型的，可被不同的负载复用

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平台模型的创建

• 和负载建模一样，使用类似于Eclipse*的图形开发环境来对平台模型的组件与互连建模

• 建模基于一般的处理器，总线，存储器和调度器

• 可对调度、性能、功耗的参数做定制

• 可选择调度和仲裁策略

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多媒体应用平台

处理器

互连

存储器

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体系结构模型的建立

• 体系结构建模

– 依据软硬件不同的划分策略将负载映射到平台

– 任务分配到不同的处理核

– 功能模块间通信的路由

– 任务优先级的定义

• 性能评测

– 延时

– 系统功耗

– 处理器利用率

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仿真结果 – 软/硬件划分

• 体系结构1：所有功能都映射到处理器去执行

• 体系结构2：视频的滤波函数映射到硬件加速器

• 时序和体系结构剖面的分析表结果：

– 得益于视频滤波计算的分担，体系结构2的显示延时有25%的下降

– 因为处理器和协处理器的频繁交互，总线利用率从2%提高到了20%

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仿真结果 – 功耗优化

• 功耗不优化 VS. 功耗优化

• 有了功耗优化，功耗的峰值变平滑了

功耗和性能的评估是设计体系结构的关键

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议程

• 问题介绍和设计挑战

• 方案 – 系统级建模

• 负载建模与时钟分析

• 平台/体系结构建模与能耗预测

• 总结/问答

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总结 • 现有设计工具需要调整以应对系统设计挑战

• 通过支持早期设计中体系结构的探索， Intel® CoFluent™ Studio解决了设计中的主要挑战

• 在没有具体平台约束的情况下使用负载模型来做功能上的验证仿真

• 功耗和性能的评估是设计体系结构的关键

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更多资讯…

• 通过以下链接了解更多关于Intel® CoFluent™ Studio的信息并免费下载 Intel CoFluent Reader:

– http://cofluent.intel.com/

• 通过以下链接了解更多关于Intel ® 软件开发工具的信息:

– http://software.intel.com/en-us/intel-sdp-home/

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Glossary

• UML: Unified Modeling Language (www.uml.org) • SysML: Systems Modeling Language

(www.sysml.org)

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