OSL Open Source

Exploiting the cache barrier command for Flash storage, we overhaul the IO scheduler, the dispatch module, and the filesystem so that these layers are orchestrated to preserve the ordering condition imposed by the application with which the associated data blocks are made durable. We implement the barrier-enabled IO stack in server as well as in mobile platforms.

Github Link: https://github.com/ESOS-Lab/barrieriostack

• • [USENIX FAST] Youjip Won, Jaemin Jung, Gyeongyeol Choi, Joontaek Oh, Seongbae Son, Jooyoung Hwang, Sangyeun Cho “Barrier Enabled IO Stack for Flash Storage”, in Proc. of  USENIX FAST 2018, Oakland, CA, USA, Feb. 12-15, 2018, Slide link : slide (Awarded Best Paper)

Github Link: https://github.com/ESOS-Lab/SHADOW

• • [VLDB] Youjip Won, Sundoo Kim, Juseong Yun, Dam Quang Tuan, Jiwon Seo, “DASH: Database Shadowing for Mobile DBMS”, Accepted for publication, In proc. of VLDB 2019, Los Angeles, CA, USA, August 26-30, 2019

We developed a heap-based persistent object store, HEAPO, to manage persistent objects in byte-addressable NVRAM. HEAPO defines its own persistent heap layout, the persistent object format, name space organization, object sharing and protection mechanism, and undo-only log based crash recovery, all of which are effectively tailored for NVRAM.

Github Link: https://github.com/ESOS-Lab/HEAPO

• • Taeho Hwang, Jaemin Jung, and Youjip Won, “HEAPO: Heap-based Persistent Object Store”, ACM Transactions on Storage, Accepted for publication, May 2014

Github Link: https://github.com/ESOS-Lab/WALDIO

• • Wongun Lee, Keonwoo Lee, Hankeun Son, Wook-Hee Kim, Beomseok Nam, Youjip Won, “WALDIO: Eliminating the Filesystem Journaling in Resolving the Journaling of Journal Anomaly”, In Proceedings of USENIX ATC(Annual Technical Conference), Santa Clara, CA, July 8 – 10, 2015

Androtrace, which is specifically tailored for Android platform. Unlike earlier works that required prolonged post processing procedures, Androtrace not only traces with low overhead, but also provides efficient solution for storage with– in mobile devices. Captured IO trace is temporarily stored in main memory and storage device, and they are transferred to Androtrace server when the device is connected to WiFi. We use server and client model to support and analyze multiple Android users.

Github Link: https://github.com/ESOS-Lab/Androtrace

• • Eunryoung Lim, Seongjin Lee, Youjip Won, “Androtrace: Framework for Tracing and Analyzing IOs on Android”,  In Proceedings of 3rd workshop on Interactions of NVM/Flash with Operating-Systems and Workloads (INFLOW 2015), California, USA, Oct. 4-7, 2015

Suspend-aware Segment Cleaning is advanced segment cleaning policy of F2FS file system in Android device. Traditional segment cleaning routine would be stopped when the device is entered to the suspend mode. Under the situation that excessive data are wrote before suspend, there could be the lack of free segment because the segment cleaning thread is frozen when suspend. SASC awares the screen-off signal and then adjust segment cleaning period before entering suspend mode. SASC adjusts segment cleaning period from 300ms to 900ms by the storage utilization. SASC consolidates x6 more free segments than stock segment cleaning does.

Github Link: https://github.com/chunccc/SASC

• • Dongil Park, Seungyong Cheon and Youjip Won, “Suspend-aware Segment Cleaning in Log-structured File System”, In Proceedings of USENIX HotStorage’15, Santa Clara, USA, July. 6-7, 2015

Android imposes user-level filesystem (FUSE) over native filesystem partition to provide flexibility in managing the internal storage space and to maintain host compatibility. However, the overhead of user-level filesystem is prohibitively large and the native storage bandwidth is significantly under-utilized. In order to address this overhead of user-level filesystem, we propose Buffered FUSE (bFUSE). The key technical ingredients of Buffered FUSE are (i) extended FUSE IO size, (ii) internal user-level write buffer (FUSE buffer) and (iii) independent management thread which performs time driven FUSE buffer synchronization.

Github Link: https://github.com/ESOS-Lab/BufferedFUSE

• • Sooman Jeong, Youjip Won, “Buffered FUSE: optimising the Android IO stack for user-level filesystem” , International Journal of Embedded Systems (IJES), Special Issue for Embedded and Ubiquitous Computing,2014 Vol. 6, No.2/3, pp.95 – 107, doi:10.1504/IJES.2014.063806

Mobibench is a benchmark tool specifically designed for simulating the I/O characteristics of the Android applications. It is capable of measuring the performance of file I/Os and SQLite operations. This has four essential features as following. First, Mobibench has a function to generate write() followed by fsync(). Second, measuring the performance of SQLite is possible. Third, Mobibench is able to run as an Android app, as well as a shell command. Finally, this tool provides various options for file and database in measuring the performance of file I/O and DBMS. Mobibench tool is used in the research works listed below.Link: http://www.mobibench.co.kr/

• • “AndroStep: Android Storage Performance Analysis Tool”, Lecture Notes in Informatics, Vol. 215, Stefan Kowalewski and Bernhard pe(Hrsg.) (1st European Workshop on Mobile Engineering), Feb. 26-Mar 1, 2013, Aachen, Germany

• • Sooman Jeong, Kisung Lee, Jungwoo Hwang, Seongjin Lee, Youjip Won, “Framework for Analyzing Android I/O Stack Behavior: from Generating the Workload to Analyzing the Trace”, Future Internet 2013, 5(4), Special Issue for “Mobile Engineering², MDPI(ISSN 1999-5903), 591-610; doi:10.3390/fi5040591

• • Sooman Jeong, Kisung Lee, Seongjin Lee, Seoungbum Son, Youjip Won, “I/O Stack Optimization for Smartphones”, USENIX ATC(Annual Technical Conference) 2013, June 26-28, 2013, San Jose, CA, USA, (Best Paper Award)

We developed mobile storage analyzer, MOST (MObile STorage analyzer) to capture the IO traces and extract key file system characteristics such as file types, ratio between random/sequential access, ratio between buffered/synchronous IO, block type, file name using reverse mapping feature. This consists of modifed Linux kernel to caputre IO traces and modified debugfs utility to reverse-map the block in the EXT4 file system. MOST is used in the research works listed below.Github Link: https://github.com/ESOS-Lab/MOST

• • Sooman Jeong, Kisung Lee, Jungwoo Hwang, Seongjin Lee, Youjip Won, “AndroStep: Android Storage Performance Analysis Tool”, Lecture Notes in Informatics, Vol. 215, Stefan Kowalewski and Bernhard pe(Hrsg.) (1st European Workshop on Mobile Engineering), Feb. 26-Mar 1, 2013, Aachen, Germany

• • Sooman Jeong, Kisung Lee, Jungwoo Hwang, Seongjin Lee, Youjip Won, “Framework for Analyzing Android I/O Stack Behavior: from Generating the Workload to Analyzing the Trace”, Future Internet 2013, 5(4), Special Issue for “Mobile Engineering², MDPI(ISSN 1999-5903), 591-610; doi:10.3390/fi5040591

• • Sooman Jeong, Kisung Lee, Seongjin Lee, Seoungbum Son, Youjip Won, “I/O Stack Optimization for Smartphones”, USENIX ATC(Annual Technical Conference) 2013, June 26-28, 2013, San Jose, CA, USA, (Best Paper Award)

• • Kisung Lee, Youjip Won, “Smart layers and dumb result: Io characterization of an android-based smartphone”, In EMSOFT 2012, In Proceedings of International Conference on Embedded Software (Oct.7-12 2012). Tampere, Finland

This is an SSD Simulator performed with full virtualized system based on QEMU. VSSIM runs in real-time and allows the user to measure both the host performance and SSD behavior under various design choices. This Simulator is used in the research works listed below.Github Link: https://github.com/ESOS-Lab/VSSIM

• • Jinsoo Yoo, Youjip Won, Joongwoo Hwang, Sooyong Kang, Jongmoo Choi, Sungroh Yoon and Jaehyuk Cha, “VSSIM: Virtual Machine based SSD Simulator”, IEEE 29th Symposium on Mass Storage Systems and Technologies (MSST 2013), Long Beach, California, USA, May 6-10, 2013

• • Joohyun Kim, Haesung Kim, Seongjin Lee, Youjip Won, “VSSIM : Virtual SSD Simulator” , 9th USENIX Symposium on Operating System Design and Implementation (OSDI ’10), Vancouver, BC, Canada, Work-In-Progress, October 4-6, 2010)

We collect the IO traces from the following applications using blktrace: < Gmail, Google Drive, Chrome, Facebook, Twitter, etc >. These IO traces are used in the research works listed below.SSD Trace Data: https://oslab.kaist.ac.kr/sub/ssd_trace_data.zip

• • Seokhei Cho, Changhyun Park, Youjip Won, Sooyong Kang, Jaehyuk Cha, Sungroh Yoon, Jongmoo Choi, “Design Trade-Offs of SSDs: from Energy Consumption’s Perspective”, ACM Trans. On Storage, Accepted for publication, Mar 2014

• • Seokhei Cho, Youjip Won, Sooyong Kang, Jaehyuk Cha, Jongmoo Choi, Sungroh Yoon, “Influence of Number of Channels and FTL on SSD Power Consumption”, International Conference of Electrical, Computer, Electronics and Biomedical Engineering (ICECEBE’2012), Dec. 28-29, 2012, Bangkok, Thailan

These trace files are collected from a SAMBA Server, which is used by about twenty people at ESOS Lab, Hanyang University. It is collected by blktrace. File types in the storage deivce include music, video, document files and files from various applications. Users access files directly or download files to host computer. Users access files directly or download files to host computer. Upload and deletion of the files in the SAMBA Server is not too frequent. Related research works are listed below.SAMBA Trace Data: http://cfsr.hanyang.ac.kr/publications/main_sambatrace.htm

• • Seokhei Cho, Changhyun Park, Youjip Won, Sooyong Kang, Jaehyuk Cha, Sungroh Yoon, Jongmoo Choi, “Design Trade-Offs of SSDs: from Energy Consumption’s Perspective”, ACM Trans. On Storage, Accepted for publication, Mar 2014

• • Seokhei Cho, Youjip Won, Sooyong Kang, Jaehyuk Cha, Jongmoo Choi, Sungroh Yoon, “Influence of Number of Channels and FTL on SSD Power Consumption”, International Conference of Electrical, Computer, Electronics and Biomedical Engineering (ICECEBE’2012), Dec. 28-29, 2012, Bangkok, Thailand

The disk layout model provided by current Disksim package is simple cylindrical layout which few modern hard disk drives adopt, and surface serpentine which most widely used. We developed a hybrid serpentine layout model for Disksim, These Layout was developed with Samsung hard disk division in developing hard disk drive for HD quality video playback. Related research works listed below.Link: https://oslab.kaist.ac.kr/sub/main_disksim.htm

• • Jongmin Gim, Youjip Won, “Relieving the Burden of Track Switch in Modern Hard Disk Drives” , Multimedia Systems: Volume 17, Number 3 (June 2011), Pages 219-235, Springer

• • Jongmin Gim, Jaehyeok Chang, Hyungwon Jung, Youjip Won,Junseok Shim, Youngseon Park, “Hard Disk Drive for HD Quality Multimedia Home Appliance” , Computational Sciences and Its Applications, 2008. ICCSA’08. IEEE, Peruja, Italy, June 2008

We developed novel disk characterization suite, DIG(Disk Geometry Analyzer), to rapidly extract and characterize the key performance metrics of modern hard disk drive. DIG is used in research works listed below.

Link: https://oslab.kaist.ac.kr/sub/main_dig.htm

• • Jongmin Gim and Youjip Won “Extract and Infer Quickly: Obtaining Sector Geometry of Modern Hard Disk Drive” , ACM Transactions on Storage, Volume 6 (2), 1553-3077, July. 1. 2010

• • Jongmin Gim, Youjip Won, Jaehyeok Chang, Junseok Shim, Youngseon Park, “DIG: Rapid Characterization of Modern Hard Disk Drive and its performance implication” , The 5th IEEE International Workshop on Storage Network Architecture and Parallel I/Os, 2008. IEEE MSST/SNAPI’08. Baltimore, USA, September 20

We implemented Real-Time operating system for highly agile media, HAMOS adopts several basic characteristics such as real-time scheduler, inter-task synchronization, etc. Related research work listed below.

Link: http://hamos.hanyang.ac.kr/index.php

• • 정원민, 한석희, 신형종, 원유집, “고속 미디어 처리를 위한 실시간 운영체제의 설계 및 구현”, 정보과학회논문지: 시스템 및 이론, 2006년 12월

We analyzed mpeg traces which is publicly available library of frame size traces of long MPEG-4 and H.263 encoded videos. Related research work listed below

Link: http://broadpeak.kaist.ac.kr/wiki/dmcweb/mpeg2data/Video_traces.htm

• • 강성주, 원유집, 성병찬, “Non-stationary VBR 트래픽을 위한 동적 데이타 크기 예측 알고리즘”, 정보과학회 논문지: 정보통신 제 34 권 제 3 호, 2007년 6월

• • Sungjoo Kang, Seongjin Lee, Youjip Won, Byeongchan Seong, “On-Line Prediction of Nonstationary Variable-Bit-Rate Video Traffic”, IEEE Transactions on Signal Processing, Volume: 58, Issue: 3, Part: 1, Mar, 2010, Page(s): 1219 – 1237

We collected the packet traces from existing campus wireless LAN infra-structure. In analysis of collected tracffic data is presented in research work in the below

Traffic Data: https://oslab.kaist.ac.kr/wp-content/uploads/esos_files/personal/Dashdorj/traffic_data.zip

• • Dashdorj Yamkhin, Seongjin Lee and Youjip Won, “Modeling and Analysis of Wireless LAN traffic” , Journal of Information Science and Engineering, Vol.25, No. 6, pp. 1783-1801, Nov. 200