Patch for adding SO_REUSEPORT socket option

Lu, Yingqi at
Thu Nov 19 20:37:00 UTC 2015

Hello All,

Currently, I think the only platform that does not have SO_REUSEPORT is Windows. API allows this possibility by throwing SocketException with message "Invalid option". Older kernel that does not support the feature throws SocketException with message "Protocol not available".

Here is the first version of the patch (we implement SO_REUSEPORT as a standard socket option):

Here is the second version of the patch (we implement SO_REUSEPORT as an extended socket option):

The performance improvement by enabling SO_REUSEPORT is significant (up to 1.93x on Hadoop Distributed File System (HDFS)). It would be great if OpenJDK can have it. Please take some time to review the patches and let us know your feedback and comments!


From: Kharbas, Kishor
Sent: Monday, November 16, 2015 10:47 AM
To: core-libs-dev at
Cc: Kharbas, Kishor; Lu, Yingqi; Kharbas, Kishor
Subject: Patch for adding SO_REUSEPORT socket option

Hello all,

I request the community to review a patch for adding SO_REUSEPORT support. There is already an existing JBS opened at

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 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 ''.

Kishor Kharbas

More information about the core-libs-dev mailing list