The fundamental role of Internet servers for the services is to send large-size multimedia files to clients efficiently. Unfortunately, general-purpose Operating System(OS) and hardware(HW) have not been optimized for the applications which transfer large-size multimedia files, resulting in poor server I/O performance as well as increasing HW cost of the server systems. One source of the problem is several redundant copies when transferring data from disks to network interface card(NIC).
To solve a redundant copy problem, we propose a Contents Delivery Accelerator(CDA) which accelerates large file transfer by eliminating the redundant copies from disks to NIC. To eliminate the redundant copies, CDA newly introduces a new function named logical direct-link. The logical direct-link provides shortest path from disks to NIC. Using this shortest path, redundant copies which are come from general-purpose OS and HW can be completely eliminated so that I/O performance of server will be improved. Furthermore, to achieve better I/O performance, we take into accounts of all fast I/O mechanisms of Linux like page-cache, read-ahead, DMA carefully.
The CDA architecture is HW/SW co-approach. Thus it comprises of CDA HW and a modified Linux kernel. Current version of CDA is implemented on a Linux 2.4.18 kernel and an IXP1200 evaluation board. In experiment, we compare the logical-direct path with a redundant path. When transferring data from disks to NIC, experimental result shows that the average transfer latency of direct path is reduced up to 30 percents as compared with that of a redundant path.
