Donghyouk Lim

EXPLOITING TEMPORAL LOCALITY FOR ENERGY EFFICIENT MEMORY MANAGEMENT

Memory is becoming one of the major power consumers in computing systems. Therefore, energy efficient memory management is essential. Modern memory systems employ sleep states for energy saving. To utilize this feature, existing research activities have concentrated on increasing spatial locality to deactivate as many blocks as possible. However, they did not count the unexpected activation of memory blocks due to cache eviction of deactivated tasks. In this paper, we suggest a software-based power state management scheme for memory, which exploits temporal locality to relieve the energy loss from the unexpected activation of memory blocks from cache eviction. The suggested scheme SW-NAP makes a memory block remain deactivated during a certain tick, which has no cache miss over the block. The evaluation shows that SW-NAP is 50% better than PAVM, which is an existing software scheme, and worse than PMU, which is another approach based on the specialized hardware by 20%. We also suggest task scheduling policies that increase the effectiveness of SW-NAP and they saved up to 7% additional energy.

A real-time responsiveness measurement method of linux-based mobile systems for P2P cloud systems

Linux-based mobile computing systems such as robots, electronic control devices, and smart-phone are the most important types of P2P cloud systems in recent days. To improve the overall performance of networked systems, each mobile computing system requires real-time characteristics. For this reason, mobile computing system developers want to know how well real-time responsiveness is supported; several real-time measurement tools have been proposed. However, those previous tools have their own measurement schemes and we think that the results from those models do not show how responsive those systems are. In this paper, we propose ELRM, a new real-time measurement method that has clear measurement interval definitions and an accurate measurement method for real-time responsiveness. We evaluate ELRM on various mobile computing systems and compare it with other existing models. As a result, our method can obtain more accurate and intuitive real-time responsiveness measurement results.

Cross-layer real-time support for JVM-based smartphone systems

The existence of the JVM layer hinders applications from notifying the operating system scheduler about their timeliness requirements and, therefore, the applications sometimes fail to respond on time. This research proposes a cross-layer real-time support by which applications notify operating systems about their timeliness requirements. Our prototype shows significant improvements in the response times and throughputs of prioritized applications.

Linux Based Real-Time Feature Supporting Method and Evaluation for Information Devices

Recently, demands of information devices are increasing as we can find so many information devices around us such as smartphone, mobile internet device (MID), tablet. These characteristics of information devices services should support soft real-time based time guaranteed multimedia services and control internet appliances. In this situation, soft real-time supported system should be developed to consider as a total aspect of hardware, kernel, middleware, application. But this paper will describe soft real-time supporting and evaluation methods for information device as an aspect of only kernel.