Utilization of Graphic Processing Unit on Smartphones
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Utilization of Graphic Processing Unit on Smartphones Abstract While the convergence of mobile phone and computing technology has been building for years, we are now starting to experience exciting and disruptive new applications on mobile devices. Starting off by introducing desktop GPUs as a reference, we discuss how mobile GPUs are designed to deliver the performance required for current and future mobile use cases. A mobile device is powered with batteries and is also small to be portable. In this paper, we discuss the architecture of one such GPU Nvidia Tegra X1, explore the key factors of it and we have compared Tegra X1 with its competitor Qualcomm Snapdragon Adreno 530. We show the rising demand for GPUs for Smartphones and tablets; The main functionality of Graphic processing unit on the mobile devices is the Visual Computing, and we also discuss the other use cases, Including the way mobile’s GPU is exploited for parallel processing for malware detection. The limitations and constraints imposed by current GPU technology is addressed. Introduction and background Mobile devices are becoming our most valuable in the present day and more valuable that personal computers. The smartphones and other portable tablets can execute almost every possible task that a PC could do, rather everyone prefer to use a mobile device because of its portability. Since the usage of these devices have become vital and the growth has been exponential, the need for faster more powerful mobile devices are required. With GPU and CPU being the two most vital processing units of the device, we concentrate on the jobs performed by the GPU in this paper. With the emergence of extreme scale computing, modern graphics processing units (GPUs) have been widely used to build powerful supercomputers and data centers. With large number of processing cores and high-performance memory subsystem, modern GPU is a perfect candidate to facilitate high performance computing (HPC). As the leading manufacturers in the GPU industry [1], Nvidia and ATI have been consistently competing by introducing a new generation series of graphic cards for computers. In recent times, similar necessity has become essential for mobile and handheld devices. Not only will high performance GPU’s will suffice, but also various other factors including the power efficiency and size of the GPU is taken into consideration while developing powerful Graphic processing units for mobile devices. Later, in the paper, we discuss about the basic GPU architecture for a mobile device; and compare the importance of performance vs power utilization. 1 The new mobile devices are more interactive, just like the newly developed immersive applications. The users have high expectations from these new mobile devices, for a smooth and uncompromised performance of these applications. To cater the needs of the user on the mobile devices, the two main components, the CPU and GPU of the device comes into action. The whole performance of a mobile device depends mostly upon the memory, CPU and the GPU used. How does a GPU work? Unlike central processors, with a few cores running at high speed, GPUs have many processing cores running at low speeds. These cores are basically aimed at two different functions: the processing of vertices and pixels. Vertex processing essentially revolves around the idea of coordinate systems. The GPU handles geometric calculations to reproduce dimensional space on your screen. This results in things like depth and spatial data in games and the possibility of rotation in three-dimensional space. The pixel processing of GPUs, or to put it more simply, the graphics we see, is very complex and requires even more processing power than is required by vertices. Pixel processing renders the various layers and applies the effects needed to create complex textures to get the most realistic graphics possible. 2 Need for more powerful GPUs. The segment of mobile gaming has been one of the fastest growing section, with the visually rich graphic mobile games being almost compared to those of PC and console games. Simple 2D games are now being developed into affluent gameplay and rich graphic 3D games demanding the fastest GPU processing built into the mobile device. The need for powerful GPU processing is to facilitate various features of the device, like delivering quick webpage and application rendering, smooth user interface interactions, high resolution displays and indeed high performance gaming. In the heat of including such high- performance GPU, challenges of power consumption and size is also considered while designing a suitable mobile device. We will consider the leading GPU brands and analyze the performance of NVIDIA’s Tegra X1 with Qualcomm Adreno 530 GPU based on a few benchmarks later in the Analysis section of this paper. GPU VS CPU Graphics processing units (GPUs) are becoming increasingly important in today’s platforms as their increased generality allows for them to be used as powerful coprocessors. A powerful GPU contributes to a rich 2D and 3D user interface[5], faster rendering of web pages and display output, and in providing a more immersive 3D gaming. These powerful GPUs’ also are very necessary while providing a smooth and responsive interface while executing applications. When we first consider the CPU and GPU and their performance independently during the computations in a mobile device, the efficiency and performance of the device falls as compared to when the GPU and CPU is integrated a used in parallel processing. The CPU is suited for most of the logic operations and operating system’s scheduling code. Most of the website’s HTML and JavaScript is parsed better when handled by the CPU. It deals with data processing jobs like reading and processing database to present emails and text messages and parsing documents into PDFs. The GPU, on the other hand, is best for rendering purposes. Effects like the window transitioning, zooming and scrolling, and animations, are handled smoothly by the GPU. Similarly, running high end 3D games on mobile devices requires the rendering capabilities of the graphic processing unit. We have seen the performance and potential when we use CPU and GPU independently, but then came the integration and processing of most the instructions parallelly by using both CPU and GPU simultaneously. To compensate for the loses when execution of applications and rendering occurs on independent efforts of the CPU and GPU, there was a recent development of integrating the CPU and GPU. Introducing the Augmented reality(AR) technology, also presented parallel processing of the CPU and GPU. AR applications help users to understand their environment better by 3 enhancing the real world with the virtual information on their mobile devices [6]. AR applications must perform intensive image processing algorithms and modules of overlaying specific virtual objects on real-time capturing. To execute these high intensive applications, parallel processing of CPU and GPU was used, where this scheme assigned the feature extraction and the feature description to CPU and GPU respectively, and these processes are conducted in parallel. The integration of CPU and GPU, and parallel processing was introduced by Nvidia Tegra 2[7], which we later explain with the image below. Modern system-on-chips (SoC) integrate CPU and GPU for better rendering and 3D immersive gaming experience on mobile devices. Multiprocessor system-on-chips in high-performance mobile platforms have witnessed unparalleled advances over the past few years. The current mobile system-on-chips combine diverse processing elements such as CPU, GPU, DSP blocks on a single chip. Digital Signal Processor (DSP) are designed high speed execution of large numeric values representing the analog signals in real time. Below figure shows the block diagram of the recent SoC by NVDIA Tegra 2. Nvidia’s Tegra series processor introduced a whole new technology of integrating powerful 3D rendering graphic GPU with CPU cores on the same chip, providing a sophisticated real- time experience for the mobile users. [7] 4 Analysis Mobile GPU architecture In the early mobile GPU stages, the CPU was involved in setting required parameters on the GPU and these GPU’s were Immediate-Mode-Rendering (IMR) based. The restructuring of pixels to the display was done span-wise (top to bottom and left to right) and the CPU had to wait for each conversion to be completed by the GPU, before it could issue a new pixel set; This causing a heavy dependency and synchronization overhead on the both the components. In the modern phase of GPU, the conversion of pixels (rasterization) was executed using the tile base approach (rendering all triangulated pixels tile by tile into the framebuffer). The usage of framebuffer reduced the memory bandwidth consumption. Although still following the IMR approach, the modern GPU’s followed Tile based deferred Rendering leading to significant reduction of dependency of the GPU and CPU. And with drastic development of System on Chips, the powerful GPU and CPU are now integrated into a single SoC [8]. An application running on a mobile device (a Game for example) utilizes the GPU which renders the triangles waits for the GPU to state on how and where it should be rendered. Processing these vertices into a noted position is done in a unit called Vertex processing. The setup unit assembles the triangles and computes data that are constant over the triangle. Computing the color of the pixel found inside the triangle is performed in the Pixel processing unit. Below is a conceptual overview of the working of a Graphic processing unit[8]. The modern mobile GPU’s are introduced as a System on Chip (SoC) which integrates a graphic processing unit, CPU, and a memory controller. A good example of the such a SoC is the NVIDIA Tegra family of processors.