Interfacing Java to the virtual interface architecture

User-level network interfaces (UNIs) have reduced the overheads of communication by exposing the buffers used by the network interface DMA engine to the applications. This removes the kernel from the critical path of message transmission and reception, and reduces the number of data copies performed on that path. Unfortunately, the fact that UNIs require the application to manage buffers explicitly makes it difficult to provide direct access to a UNI from Java, as the language explicitly prevents programs from controlling the location or layout of objects. This paper describes Javia, a Java interface to the Virtual Interface Architecture (VIA), an emerging UNI standard in the industry. Javia explores two points in the design space. The first approach manages buffers in C code and requires data copies between the Java heap and native buffers. The second approach introduces a special Java-level buffer abstraction that allows programs to allocate regions of memory outside the Java heap and to use them directly and safely as Java arrays. These buffers eliminate the bottlenecks of the first approach but require modifications to the garbage collector. Simple experiments show that Java programs can achieve bandwidths of 80Mbytes/sec for 8Kbyte messages, which is within 1% of those achieved by C programs.