The paper 'create() Scalability of F2FS Through Per-Core NAT in Manycore Environments', written by graduate student Hwang Soon of the Department of Computer Science & Engineering (master's, 4th semester) under the supervision of Professor Kim Young-jae, received the Excellent Paper Award in the computer systems field at the Korean Institute of Information Scientists and Engineers conference (KSC 2021) held on 20 December 2021.

▲ From left: Hwang Soon (master's, 4th semester; supervisor: Professor Kim Young-jae), Lee Chang-gyu (combined master's–doctoral, 9th semester; supervisor: Professor Kim Young-jae), Han Jung-wook (master's, 2nd semester; supervisor: Professor Kim Young-jae), Professor Kim Young-jae (supervisor)

▲ Excellent Paper Award at the 2021 Korean Institute of Information Scientists and Engineers conference

Figure 1. The file create flow of existing F2FS

Figure 2. The create flow of F2FS with per-core NAT applied

As the number of cores provided by a single CPU has grown recently, manycore servers with hundreds of cores are being used in data processing systems. Manycore servers, drawing on high-performance storage such as NVMe SSDs, have also made highly parallel I/O processing to local file systems possible. When many cores perform I/O simultaneously on a local file system in a manycore environment, performance scalability drops sharply. Performance scalability — throughput increasing in proportion to the number of cores performing I/O — can be divided broadly into data I/O scalability and metadata I/O scalability. The low scalability of metadata I/O is due to the use of file system-wide locks on the data structures that metadata I/O operations share.

To improve the performance scalability of create(), a representative metadata I/O operation, this paper analyses the create() scalability of the Linux file system F2FS using FxMark. The analysis confirmed that the create() scalability bottleneck stems from blocking caused by locks applied to the Free NID Cache and NAT Cache, which cache the on-disk NAT (Node Address Table) data structure. To resolve this, the paper proposes per-core NAT, which allows each core independent access to the NAT cache, and demonstrates scalability in a workload where each core performs create() in its own separate directory.

The Korean Institute of Information Scientists and Engineers conference (KSC 2021) is an information science and technology conference at which the latest research results across every area of information technology — artificial intelligence, computer systems, information security and high-assurance computing and more — are presented.

Paper link: https://discos.sogang.ac.kr/file/2021/dome_paper/KSC_2021_S_Hwang.pdf