CSR: Small: Memory System Optimizations to Enable Fast-Response Mobile Devices at Low Power

过去十年见证了计算平台的范式转变。智能手机和平板电脑等新兴手持设备已成为日常使用中最常见的计算设备之一。能耗是影响移动手持设备发展的主要考虑因素之一，因为它决定了设备在电池供电下保持可用的持续时间。智能手机等设备的使用模式与笔记本电脑和台式机等传统计算设备有很大不同，用户对这些手持移动设备的期望也不同。例如，移动设备预计将始终开机-至少一天，并启动和快速响应。另一方面，笔记本电脑/台式机设备预计在高使用量下表现良好，对快速启动和响应的期望并不那么严格。此外，在应用程序使用方面，移动系统往往具有低级别多任务的突发使用，而桌面使用涉及更连续的长时间运行的程序，具有高级别的多任务处理。该项目寻求通过利用这些使用差异来优化移动设备中的存储系统，以实现快速响应时间，同时保持低功耗。它包括三个方面的方法：首先，通过开发使用日志程序来分析移动用户的使用模式，从而减少活动内存占用。第二，开发智能纠错方案，其可以在不损害数据完整性的情况下减少存储系统消耗的刷新能量。第三，通过利用新兴的非易失性存储器(NVM)技术和开发可以将关键数据保留在NVM中的数据分区技术来降低存储器功耗。内存功耗仍然是移动平台电池寿命的主要限制因素之一。除了智能手机和平板电脑的一般用途外，高效的移动存储系统还应用于监控、汽车、环境、军事和生物医学等其他领域。我们提案中开发的技术也将对这些领域有用。关于使用记录和使用特征的基础设施将促进移动存储系统领域的其他研究。

The past decade has seen a paradigm shift in computing platforms. Emerging handheld devices such as Smartphones and Tablets have become one of the most common devices for computing in everyday use. Energy consumption is one of the prime considerations that influence the development of mobile hand-held devices, as it determines the duration for which the device remains usable on battery power. The usage patterns for devices such as smartphones are quite different from traditional computing devices such as laptops and desktops, and users have a different set of expectation from these handheld mobile devices. For example, mobile devices are expected to be always-on for at-least a day and to start-up and respond quickly. On the other hand, laptop/desktop devices are expected to perform well under heavy use, and the expectations of fast start-up and response are not as stringent. Furthermore, in terms of application usage, mobile systems tends to have burst usage with low-levels of multitasking, while desktop usage involves more continuous long-running programs with high-levels of multitasking. The project seeks to optimize the memory system in mobile devices to enable fast-response time while maintaining low power by levering these usage differences. It consists of a three-pronged approach: First, reducing active memory footprint size by analyzing the usage patterns of mobile users by developing a usage logging program. Second, developing intelligent error correction schemes that can reduce the refresh energy consumed by the memory system without compromising data integrity. Third, reducing the memory power by utilizing emerging Non Volatile Memory (NVM) technologies and developing data partitioning techniques that can keep critical data in NVM. Memory power consumption continues to be one of the main limiter of the battery life of mobile platforms. In additional to the general use as smartphone and tablets, efficient mobile memory system has use in several other application domains such as surveillance, automotive, environment, military, and biomedical. The techniques developed in our proposal will be useful for these domains as well. The infrastructure on usage logging and the usage characterization will foster other studies in the area of mobile memory systems.