Systems Research and Architecture System und Rechnerarchitektur SRA
a SRA Theses Enhancing Energy Efficiency with Advanced DRAM Management in Linux

Enhancing Energy Efficiency with Advanced DRAM Management in Linux

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Problem Description

Modern computer systems face a significant challenge in managing physical memory efficiently, especially in the context of energy consumption. Traditional methods of memory management are not optimized for today's heterogeneous, nonvolatile, and large memory architectures. Specifically, the DRAM (Dynamic Random-Access Memory) components in these systems consume a considerable amount of energy due to their constant refresh requirements. This inefficiency is more pronounced in multi-core systems and impacts both performance and energy consumption. The recent LLFree allocator, developed by us (Wrenger et.al) addresses issues related to memory fragmentation and allocation efficiency, providing a foundation for further exploration in memory management.

Approach

The thesis will explore the integration of fine-granular DRAM management with the LLFree allocator framework. The approach involves selectively disabling DRAM-row refresh operations for memory blocks that are currently not allocated and do not hold data. By integrating this idea with the LLFree allocator, which is known for its anti-fragmentation properties and efficient memory management, the thesis aims to create a system that can dynamically and efficiently allocate memory while minimizing energy consumption.

The research involves the interaction between OS and DRAM controller, the integrartion of LLFree with this new hardware feature, and potentially modified memory-allocation policies to enlarge empty areas of physical DRAM. You will have to conduct experiments under Linux using a RAM emulator to measure the impact on energy efficiency.

This thesis offers a unique opportunity to contribute to the evolving field of energy-efficient computing, with potential implications for both software and hardware optimization in modern computer systems.

Additional Context and Technical Background

LLFree offers a scalable, lock- and log-free approach to memory allocation, significantly outperforming the traditional Linux frame allocator in terms of allocation time and memory compaction. Its cache-friendly data structures and antifragmentation behavior make it an ideal candidate for integration with advanced DRAM management techniques. This thesis will build upon the LLFree's capabilities, exploring how its efficient memory allocation can synergize with energy-saving DRAM management strategies.

DRAM has the necessity to periodically refresh data. DRAM stores data in tiny capacitors, which are prone to leakage over time. To prevent data loss, these capacitors need to be periodically recharged, a process known as a DRAM refresh. Typically, this refresh happens every 64 milliseconds, where the memory controller reads data from each row of the DRAM and writes it back, effectively recharging the capacitors. This operation is crucial for maintaining data integrity but also contributes significantly to power consumption, especially in large memory systems.

Requirements

Topics: Linux, Physical Memory Management, C, Rust