Patch for adding SO_REUSEPORT socket option

[Kharbas, Kishor]

Hello all,

I request the community to review a patch for adding SO_REUSEPORT support. There is already an existing JBS opened at https://bugs.openjdk.java.net/browse/JDK-6432031

Details :

SO_REUSEPORT removes 1:1 assignment between listen socket and IP:PORT pair and enable multiple sockets listening to the same address and port. This improves the scalability and parallelism of network traffic handling. It is enabled for both TCP and UDP sockets (at least for Linux). For more details, please refer to https://lwn.net/Articles/542629/. Many applications, especially Linux or BSD based webservers such as Apache httpd and Nginx are already supporting it now. Ruby and Python have it supported as well. Other Java applications such as Netty webserver have it supported via JNI function since JDK has not supported it yet.



By enabling the SO_REUSEPORT feature itself, up to 4X throughput and latency improvement have been observed from various applications. Specific to Java application with this patch, we modified Apache Hadoop Distributed File System (HDFS) source code to take advantage of this feature. We observed up to 1.93x performance improvements.

The feature is supported since Linux Kernel 3.9. It is also supported in BSDs, Solaris and Mac OS. Windows does not have it. In the current patch, we only enable the feature on Linux platform since we do not have BSD, Solaris and Mac OS for testing. Whether the feature is supported or not on the running kernel is determined at the run time.

P.S. Based on Alan Baleman's comment on JBS, we are in meanwhile working on adding this option to 'java.net.ExtendedSocketOption'.

Regards,
Kishor Kharbas