Turn On Java epoll

 今天整理舊代碼的時候，發現Gemfire consultant  給JVM添加了一個參數。

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

沒有見過這個參數，因此google了一下：

使用這個參數 重點是： Linux 2.6 system and handles lots of simultaneous connections

下面是從from Oracle epoll blog 複製過來的

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.

網上資料顯示，JDK6後，epoll是默認打開的，可是目前尚未找到官方文檔

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