Application-Adaptive Performance Improvement in Mobile Systems by Using Persistent Memory

Bahn, Hyokyung The Institute of Internet 2019 Journal of Advanced Smart Convergence Vol.8 No.1

In this article, we present a performance enhancement scheme for mobile applications by adopting persistent memory. The proposed scheme supports the deadline guarantee of real-time applications like a video player, and also provides reasonable performances for non-real-time applications. To do so, we analyze the program execution path of mobile software platforms and find two sources of unpredictable time delays that make the deadline-guarantee of real-time applications difficult. The first is the irregular activation of garbage collection in flash storage and the second is the blocking and time-slice based scheduling used in mobile platforms. We resolve these two issues by adopting high performance persistent memory as the storage of real-time applications. By maintaining real-time applications and their data in persistent memory, I/O latency can become predictable because persistent memory does not need garbage collection. Also, we present a new scheduler that exclusively allocates a processor core to a real-time application. Although processor cycles can be wasted while a real-time application performs I/O, we depict that the processor utilization is not degraded significantly due to the acceleration of I/O by adopting persistent memory. Simulation experiments show that the proposed scheme improves the deadline misses of real-time applications by 90% in comparison with the legacy I/O scheme used in mobile systems.

Characterization Studies on Data Access Bias in Mobile Platforms

Bahn, Hyokyung The Institute of Internet 2021 International journal of advanced smart convergenc Vol.10 No.4

Data access bias can be observed in various types of computing systems. In this paper, we characterize the data access bias in modern mobile computing platforms. In particular, we focus on the access bias of data observed at three different subsystems based on our experiences. First, we show the access bias of file data in mobile platforms. Second, we show the access bias of memory data in mobile platforms. Third, we show the access bias of web data and web servers. We expect that the characterization study in this paper will be helpful in the efficient management of mobile computing systems.

CPC: A File I/O Cache Management Policy for Compute-Bound Workloads

Bahn, Hyokyung The Institute of Internet 2022 International journal of advanced smart convergenc Vol.11 No.2

With the emergence of the new era of the 4th industrial revolution, compute-bound workloads with large memory footprint like big data processing increase dramatically. Even in such compute-bound workloads, however, we observe bulky I/Os while loading big data from storage to memory. Although file I/O cache plays a role of accelerating the performance of storage I/O, we found out that the cache hit rate in such environments is not improved even though we increase the file I/O cache capacity because of some special I/O references generated by compute-bound workloads. To cope with this situation, we propose a new file I/O cache management policy that improves the cache hit rate for compute-bound workloads significantly. Trace-driven simulations by replaying file I/O reference logs of compute-bound workloads show that the proposed cache management policy improves the cache hit rate compared to the well-acknowledged CLOCK algorithm by a large margin.

Analyzing Input Patterns of Smartphone Applications in Touch Interfaces

Bahn, Hyokyung,Kim, Jisun The Institute of Internet 2021 International journal of advanced smart convergenc Vol.10 No.4

Touch sensor interface has become the most useful input device in a smartphone. Unlike keypad/keyboard interfaces used in electronic dictionaries and feature phones, smartphone's touch interfaces allow for the recognition of various gestures that represent distinct features of each application's input. In this paper, we analyze application-specific input patterns that appear in smartphone's touch interfaces. Specifically, we capture touch input patterns from various Android applications, and analyze them. Based on this analysis, we observe a certain unique characteristics of application's touch input patterns. This can be utilized in various useful areas like user authentications, prevention of executing application by illegal users, or digital forensic based on logged touch patterns.

Analyzing Input Patterns of Smartphone Applications in Touch Interfaces

Hyokyung Bahn,Jisun Kim 한국인터넷방송통신학회 2021 Journal of Advanced Smart Convergence Vol.10 No.4

Touch sensor interface has become the most useful input device in a smartphone. Unlike keypad/keyboard interfaces used in electronic dictionaries and feature phones, smartphone’s touch interfaces allow for the recognition of various gestures that represent distinct features of each application’s input. In this paper, we analyze application-specific input patterns that appear in smartphone’s touch interfaces. Specifically, we capture touch input patterns from various Android applications, and analyze them. Based on this analysis, we observe a certain unique characteristics of application’s touch input patterns. This can be utilized in various useful areas like user authentications, prevention of executing application by illegal users, or digital forensic based on logged touch patterns.

Characterization Studies on Data Access Bias in Mobile Platforms

Hyokyung Bahn 한국인터넷방송통신학회 2021 Journal of Advanced Smart Convergence Vol.10 No.4

Data access bias can be observed in various types of computing systems. In this paper, we characterize the data access bias in modern mobile computing platforms. In particular, we focus on the access bias of data observed at three different subsystems based on our experiences. First, we show the access bias of file data in mobile platforms. Second, we show the access bias of memory data in mobile platforms. Third, we show the access bias of web data and web servers. We expect that the characterization study in this paper will be helpful in the efficient management of mobile computing systems.

Application-Adaptive Performance Improvement in Mobile Systems by Using Persistent Memory

Hyokyung Bahn 한국인터넷방송통신학회 2019 Journal of Advanced Smart Convergence Vol.8 No.1

In this article, we present a performance enhancement scheme for mobile applications by adopting persistent memory. The proposed scheme supports the deadline guarantee of real-time applications like a video player, and also provides reasonable performances for non-real-time applications. To do so, we analyze the program execution path of mobile software platforms and find two sources of unpredictable time delays that make the deadline-guarantee of real-time applications difficult. The first is the irregular activation of garbage collection in flash storage and the second is the blocking and time-slice based scheduling used in mobile platforms. We resolve these two issues by adopting high performance persistent memory as the storage of real-time applications. By maintaining real-time applications and their data in persistent memory, I/O latency can become predictable because persistent memory does not need garbage collection. Also, we present a new scheduler that exclusively allocates a processor core to a real-time application. Although processor cycles can be wasted while a real-time application performs I/O, we depict that the processor utilization is not degraded significantly due to the acceleration of I/O by adopting persistent memory. Simulation experiments show that the proposed scheme improves the deadline misses of real-time applications by 90% in comparison with the legacy I/O scheme used in mobile systems.

Memory Allocation in Mobile Multitasking Environments with Real-time Constraints

Hyokyung Bahn 한국인터넷방송통신학회 2023 International Journal of Internet, Broadcasting an Vol.15 No.1

Due to the rapid performance improvement of smartphones, multitasking on mobile platforms has become an essential feature. Unlike traditional desktop or server environments, mobile applications are mostly interactive jobs where response time is important, and some applications are classified as real-time jobs with deadlines. When interactive and real-time jobs run concurrently, memory allocation between multitasking applications is a challenging issue as they have different time requirements. In this paper, we study how to allocate memory space when real-time and interactive jobs are simultaneously executed in a smartphone to meet the multitasking requirements between heterogeneous jobs. Specifically, we analyze the memory size required to satisfy the constraints of real-time jobs and present a new model for allocating memory space between heterogeneous multitasking jobs. Trace-driven simulations show that the proposed model provides reasonable performance for interactive jobs while guaranteeing the requirement of real-time jobs.

분산 이질형 객체 환경에서 캐슁 알고리즘의 설계 및 성능 분석

반효경(Hyokyung Bahn),노삼혁(Sam H. Noh),민상렬(Sang Lyul Min),고건(Kern Koh) 한국정보과학회 2000 정보과학회논문지 : 시스템 및 이론 Vol.27 No.6

캐슁 기법은 저장 장치 계층 간의 속도차를 완충시키기 위해 캐쉬 메모리, 페이징 기법, 버퍼링 기법 등으로 널리 연구되어 왔다. 하지만, 최근 웹을 비롯한 다양한 광역 분산 환경의 보편화에 따라 단일 시스템 내의 저장 장치 간에 이루어지는 캐슁 기법 뿐 아니라 타 노드의 객체를 캐슁하는 기법의 중요성이 커지고 있다. 광역 분산 환경에서의 캐슁 기법은 객체의 캐슁에 드는 비용과 캐슁으로 인한 이득이 객체의 근원지 노드의 위치에 따라 이질적이기 때문에 비용 차이를 고려한 캐쉬 교체 알고리즘이 필요하다. 한편, 캐쉬 교체 알고리즘은 온라인 알고리즘으로서 매 시점 교체 대상이 되는 객체를 즉시 선택해야 하기 때문에 알고리즘의 시간 복잡도가 지나치게 높지 않아야 한다. 그러나, 광역 분산 환경에서의 교체 알고리즘에 대한 지금까지의 연구는 객체들의 이질성을 고려하는 문제와 캐쉬 운영의 시간 복잡도 측면 모두에서 만족스러운 결과를 보이지는 못하고 있다. 본 논문은 이러한 점을 극복하여 우수한 성능을 나타내면서 효율적인 구현이 가능한 새로운 교체 알고리즘을 설계하고, 그 우수성을 트레이스 기반 모의 실험을 통해 보여 준다. Caching mechanisms have been studied extensively to buffer the speed gap of hierarchical storages in the context of cache memory, paging system, and buffer management system. As the wide-area distributed environments such as the WWW extend broadly, caching of remote objects becomes more and more important. In the wide-area distributed environments, the cost and the benefit of caching an object is not uniform due to the location of the object; which should be considered in the cache replacement algorithms. For online operation, the time complexity of the replacement algorithm should not be excessive. To date, most replacement algorithms for the wide-area distributed environments do not meet both the non-uniformity of objects and the time complexity constraint. This paper proposes a replacement algorithm which considers the non-uniformity of objects properly; it also allows for an efficient implementation. Trace-driven simulations show that proposed algorithm outperforms existing replacement algorithms.

유전 알고리즘을 이용한 웹 프락시 캐시의 교체 정책 설계

반효경(Hyokyung Bahn),조경운(Kyoungwoon Cho),고건(Kern Koh),문병로(Byungro Moon) 한국정보과학회 1999 정보과학회논문지 : 시스템 및 이론 Vol.26 No.6

WWW의 사용량이 대단히 빠르게 늘어남에 따라 웹 프락시 서버의 캐싱 기능은 그 중요성이 날로 증가하고 있다. 본 논문에서는 이러한 웹 프락시 캐시의 교체 정책을 웹 요구의 특성과 프락시 서버환경 자체를 고려하여 주어진 환경에 맞는 교체 정책이 되도록 유전 알고리즘을 사용하여 설계하는 방법을 제시하였다. 이 방법은 대부분의 기존 연구에서처럼 특정한 교체 정책 자체를 제시하는 것이 아니라, 주어진 프락시 환경에 적합한 교체 정책을 동적으로 설계할 수 있는 방법을 제시한다는 점에서 기존의 연구보다 일반성이 높다. As the demand for WWW increases rapidly, the importance of caching at proxy servers also increases day by day. In this paper, we design WWW proxy cache replacement policies which consider the characteristics of Web requests and the environment of proxy servers using genetic algorithms. Unlike most of previous works that show their fixed replacement policies, this approach provides a general framework for the design of appropriate replacement policies for dynamic proxy environments.