Turn On Java epoll

 今天整理旧代码的时候，发现Gemfire consultant  给JVM添加了一个参数。

-Djava.nio.channels.spi.SelectorProvider=sun.nio.ch.EPollSelectorProvider

没有见过这个参数，所以google了一下：

使用这个参数 重点是： Linux 2.6 system and handles lots of simultaneous connections

下面是从from Oracle epoll blog 复制过来的

So if you are running on a Linux 2.6 system with an application that handles lots of simultaneous connections you might want to give it a test-run. 

Will you see a difference? It depends on the workload. If you've registered lots of SelectableChannels with a Selector and you notice a lot of time spent in the kernel due to poll then you should see a difference. If you are doing test runs and you want to do a direct comparison with poll then you can set the java.nio.channels.spi.SelectorProvider system property to sun.nio.ch.PollSelectorProvider. This will select the poll-based Selector that will continue to be the default on 2.4 kernels. There is an epoll patch for 2.4 kernels but at this time anyway, the NIO implementation doesn't attempt to detect this.

网上资料显示，JDK6后，epoll是默认打开的，但是目前还没有找到官方文档

by the way, command to show the Linux Kerl uname -r