R&D: Building Stream-based Page Cache to Accelerate File Scanning on Fast Storage Devices

ACM Transactions on Storage has published an article written by Zhiyue li, Tsinghua University, Beijing, China, and Guangyan Zhang, Dept. Computer science and technology, Tsinghua University, Beijing, China.

Abstract: “Buffered I/O via page cache is used for file scanning in many cases as page cache can provide buffering, data aggregation, I/O alignment, and prefetching transparently. However, our study indicates that employing page cache for file scanning on fast storage devices presents two performance issues: it offers limited I/O bandwidth that does not align with the performance of fast storage devices, and the intensive background writeback onto fast storage devices can significantly interfere with foreground I/O requests.“

“In this paper, we propose StreamCache, a new page cache management system for file scanning on fast storage devices. StreamCache exploits three techniques to achieve high I/O performance. First, it uses a two-layer memory management method to accelerate page allocation by leveraging CPU cache locality. Second, it uses a stream-based page reclaiming method to lower the interference to foreground I/O requests. Third, it uses a lightweight stream tracking method to record the states of cached pages at the granularity of sequential streams to support stream-based page reclaiming.“

“We implement StreamCache in XFS. Experimental results show that compared with existing methods, StreamCache can increase the I/O bandwidth of scientific applications by 44%, and reduce the checkpoint/restart time of large language models by 15.7% on average.“