Speaker : Pramod Nagaraja

This session explains how you can improve performance of I/O-intensive Java™ applications through a technique called zero copy. Zero copy lets you to avoid redundant data copies between intermediate buffers and reduces number of context switches between user and kernel space.

Background: Many applications [Web Servers, FTP-like services] serve a significant amount of static content, which amounts to reading data off of a disk and writing the exact data back to the response socket. Each time data traverses the user-kernel boundary; it must be copied, which consumes CPU cycles and memory bandwidth. Fortunately, we can eliminate these copies through a technique called — zero copy.

The Java class libraries support zero copy on Linux and UNIX systems through the transferTo() method in java.nio.channels.FileChannel.

Session Agenda: The session will initially focus on “Zero Copy” concept and its relevance in Data transfer applications. The traditional approach of transferring data b/w processes using File and Socket I/O will be explained in detail. It will demonstrate the overhead incurred when using traditional copy semantics, and will show how transferTo() achieves better performance. transferTo() API brings down the time 65% compared to traditional approach.

Summary
The Session demonstrates performance advantages of using transferTo() compared to the traditional approach. Intermediate buffer copies — even those hidden in the kernel — can have a measurable cost. In applications that do a great deal of copying of data between channels, zero-copy technique can offer a significant performance improvement.