A Memory Copy Reduction Scheme for Networked Multimedia Service in Linux Kernel

Abstract

While Multimedia streams need an efficient support of kernel, the current buffer cache mechanism of Linux kernel originally based on the Unix operating system is designed apt for small files, which are aperiodically requested and time-uncritical. But, in case of continuous media, the overhead of CPU occurs for large copying memory from kernel address space to user address space. This overhead both degrades system throughputs and cannot guarantee QOS. In this paper, we’ve designed and implemented two memory copy reduction schemes in Linux kernel, direct I/O and one-copy. The direct I/O path skips the buffer cache layer of Linux kernel and directly copies the disk blocks to the user buffer. And, the one-copy provides fast disk-to-network data path without copying to user address space. These enhancements should increase the throughputs of VOD server. The experimental results demonstrate throughput improvements and show considerable reduction of CPU overhead.