用户:MofuMoca/异构系统架构

在非HSA系统中使用GPU执行分担运算的步骤

在HSA系统中使用GPU执行分担运算的步骤，使用HSA的功能

异构系统架构（Heterogeneous System Architecture，HSA） ，是一种中央处理器与图形处理器共享汇流排、记忆体及处理程序的电脑处理器架构 HSA由HSA基金会开发，其中包含AMD及ARM。HSA起始目标是为了减少CPU、GPU以及其他计算单元之间的沟通延迟，并且从程式设计师的角度来看， 能够让许多设备更相容，减少程式设计师去规划资料在装置间所互不相通之记忆体中移动的程序（必须透过OpenCL或CUDA）。 异构计算广泛地被使用在系统单晶片装置中，像是平板电脑、智慧型手机以及其他行动装置。 HSA允许程式使用图形处理器（GPU）去计算浮点数，而不须调度或独立的记忆体。

概览

HSA is a set of features defining a system architecture that intends to make heterogeneous computing more mainstream. Heterogeneous computing itself refers to systems that contain multiples processing units – central processing units (CPUs), graphics processing units (GPUs), digital signal processors (DSPs), or any type of application-specific integrated circuits (ASICs). The system architecture allows any accelerator, for instance a graphics processor, to operate at the same processing level as the system's CPU.

Among its main features, HSA defines a unified virtual address space space for compute devices: where GPUs traditionally have their own memory, separate from the main (CPU) memory, HSA requires these devices to share page tables so that devices can exchange data by sharing pointers. This is to be supported by custom memory management units. To render interoperability possible and also to ease various aspects of programming, HSA is intended to be ISA-agnostic for both CPUs and accelerators, and to support high-level programming languages.

So far, the HSA specifications cover:

• HSA Intermediate Layer (HSAIL), a virtual instruction set for parallel programs
  • similarTemplate:According to whom? to LLVM Intermediate Representation and SPIR (used by OpenCL and Vulkan
  • finalized to a specific instruction set by a JIT compiler
  • make late decisions on which core(s) should run a task
  • explicitly parallel
  • supports exceptions, virtual functions and other high-level features
  • syscall methods (I/O, printf, etc.)
  • debugging support
• HSA memory model
  • compatible with C++11, OpenCL, Java and .NET memory models
  • relaxed consistency
  • designed to support both managed languages (e.g. Java) and unmanaged languages (e.g. C)
  • will make it much easier to develop 3rd-party compilers for a wide range of heterogeneous products programmed in Fortran, C++, C++ AMP, Java, et al.
• HSA dispatcher and run-time
  • designed to enable heterogeneous task queueing: a work queue per core, distribution of work into queues, load balancing by work stealing
  • any core can schedule work for any other, including itself
  • significant reduction of overhead of scheduling work for a core

Mobile devices are one of the HSA's application areas, in which it yields improved power efficiency.

方块图

The block diagrams below provide high-level illustrations of how HSA operates and compares to traditional architectures.

• 
  Standard architecture with a discrete GPU attached to the PCI Express bus. Zero-copy between the GPU and CPU is not possible due to distinct physical memories.
• 
  HSA brings unified virtual memory, and facilitates passing pointers over PCI Express instead of copying the entire data.
• 
  In partitioned main memory, one part of the system memory is exclusively allocated to the GPU. As a result, zero-copy operation are not possible.
• 
  Unified main memory, made possible by a combination of HSA-enabled GPU and CPU. As a result, it is possible to perform zero-copy operations.
• 
  Both the CPU's MMU and the GPU's IOMMU have to comply with the HSA hardware specifications.

软体支援

AMD GPUs contain certain additional functional units intended to be used as part of HSA. In Linux, kernel driver amdkfd provides required support.

Some of the HSA-specific features implemented in the hardware need to be supported by the operating system kernel and specific device drivers. For example, support for AMD Radeon and AMD FirePro graphics cards, and APUs based on so-called Graphics Core Next (GCN), was merged into version 3.19 of the Linux kernel mainline, released on February 8, 2015. Programs do not interact directly with amdkfd, but queue their jobs utilizing the HSA runtime. This very first implementation, known as amdkfd, focuses on "Kaveri" or "Berlin" APUs and works alongside the existing Radeon kernel graphics driver.

Additionally, amdkfd supports so-called heterogeneous queuing (HQ), which aims to simplify the distribution of computational jobs among multiple CPUs and GPUs from the programmer's perspective. 截至2015年2月 (2015-02), support for heterogeneous memory management, suited only for graphics hardware featuring version 2 of the AMD's IOMMU, has not yet been accepted into the Linux kernel mainline.

Integrated support for HSA platforms has been announced for the "Sumatra" release of OpenJDK, due in 2015.

AMD APP SDK is AMD's proprietary software development kit targeting parallel computing, available for Microsoft Windows and Linux. Bolt is a C++ template library optimized for heterogeneous computing.

硬体支援

截至2015年2月 (2015-02), only AMD's "Kaveri" A-series APUs (cf. "Kaveri" desktop processors and "Kaveri" mobile processors) and Sony's PlayStation 4 contain version 2 of the AMD's IOMMU.

参见

• General-purpose computing on graphics processing units (GPGPU)
• OpenMP
• Zero-copy

外部链接

• YouTube上的HSA Heterogeneous System Architecture Overview by Vinod Tipparaju at SC13 in November 2013
• HSA and the software ecosystem
• 2012 – HSA by Michael Houston