jdk1.4+ jvm parameters

-verbose:gc -XX:+PrintGCTimeStamps -XX:+PrintGCDetails -XX:+PrintTenuringDistribution


-Xms2048M -Xmx2048M -XX:MaxPermSize=128M -XX:NewRatio=3 -Xmn400M -XX:SurvivorRatio=30 -Xloggc:/var/log/search/tomcat_gc.log

above params means

jvm mem=2048M
perm gen=128M
old gen:young gen=3:1, so old gen=1920*0.75=1440M 
young gen=480M


eden:survivor=30:1,so survivor1=survivor2=480/32=15M
                      eden=480-30=450M


PrintTenuringDistribution means from young gen to old gen.


http://blog.csdn.net/jimmy1980/article/details/4968308
http://blog.csdn.net/alivetime/article/details/6895537