系统这两天出现了长时间的full gc, 使用-XX:+UseConcMarkSweepGC后,系统正常
5.4 The Concurrent Low Pause Collector
The concurrent low pause collector is a generational collector similar to the serial collector. The tenured generation is collected concurrently with this collector.
This collector attempts to reduce the pause times needed to collect the tenured generation. It uses a separate garbage collector thread to do parts of the major collection concurrently with the applications threads. The concurrent collector is enabled with the command line option -XX:+UseConcMarkSweepGC. For each major collection the concurrent collector will pause all the application threads for a brief period at the beginning of the collection and toward the middle of the collection. The second pause tends to be the longer of the two pauses and multiple threads are used to do the collection work during that pause. The remainder of the collection is done with a garbage collector thread that runs concurrently with the application. The minor collections are done in a manner similar to the serial collector although multiple threads are used to do the collection. See "Parallel Minor Collection Options with the Concurrent Collector" below for information on using multiple threads with the concurrent low pause collector.
The techniques used in the concurrent collector (for the collection of the tenured generation) are described at:
http://research.sun.com/techrep/2000/abstract-88.html
http://java.sun.com/docs/hotspot/gc5.0/gc_tuning_5.html
print gc.log
-verbose:gc -Xloggc:gc.log -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution