Thanks for Wolf-Dieter and Peter's answer, I am reading Peter's white papers now.
And i have done another test, this time i set 10 threads in Jmeter, and the throughput first time above to 42 and one night later fall to stay at 37.4.
Follow charp is the "Full GC"map record from jconsole. I can't understand why in the first time, full gc came so often, but when the 'Troughput' become stay at 37.4, the full gc become happen allmost once every hour?
http://community.jboss.org/servlet/JiveServlet/downloadImage/2-590582-11831/450-356/gccharp.bmp
