http://www.andowson.com/posts/list/4.page JForum - http://www.jforum.net java -XmxXXXXM -version指令來測試JVM最大的記憶體設定，經過我自己在CentOS 4.4 Linux上面測試後發現JDK 6.0可以支援到2690M

[andowson@www bin]$ java -Xmx2690M -version
java version "1.6.0"
Java(TM) SE Runtime Environment (build 1.6.0-b105)
Java HotSpot(TM) Client VM (build 1.6.0-b105, mixed mode)
[andowson@www bin]$ java -Xmx2691M -version
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.

但是如果再加上-server參數，則可以再往上擠出10M，達到2700M。
[andowson@www bin]$ java -server -Xmx2700M -version
java version "1.6.0"
Java(TM) SE Runtime Environment (build 1.6.0-b105)
Java HotSpot(TM) Server VM (build 1.6.0-b105, mixed mode)
[andowson@www bin]$ java -server -Xmx2701M -version
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.]]> http://www.andowson.com/posts/preList/30/34.page http://www.andowson.com/posts/preList/30/34.page GMT
並發用戶量比較大的應用應該通過集群的方式解決問題。]]> http://www.andowson.com/posts/preList/30/99.page http://www.andowson.com/posts/preList/30/99.page GMT http://www.andowson.com/posts/preList/30/101.page http://www.andowson.com/posts/preList/30/101.page GMT 如果JVM heap size設置過大在JVM heap回收内存的時候會導致整個系統停頓一段時間，所以JVM heap size大小的調整是以滿足應用需要為目的。除非你的JVM支持多綫程回收内存，並且設置JVM參數讓JVM在系統CPU空閒的時候部分回收JVM heap内存，否則過大的JVM heap size勢必影響系統性能。]]> http://www.andowson.com/posts/preList/30/102.page http://www.andowson.com/posts/preList/30/102.page GMT [url=http://www.caucho.com/resin-3.0/performance/jvm-tuning.xtp]JVM Tuning[/url]
:!:Xms建議等於Xmx
:!:Xmn要小於Xmx
:!:Heap size 不能決定JVM真正使用記憶體的大小，實際上會更大
Memory usage=Stack Size+Heap Size+Code Size
:!:調整Stack size的參數是Xss

[url=http://publib.boulder.ibm.com/infocenter/wxdinfo/v6r0/index.jsp?topic=/com.ibm.websphere.xd.doc/info/odoe_task/todhmmheap.html]Modifying the JVM heap size[/url]
IBM的這篇文章有一些實體記憶體大小對應Heap Size設定的參考數字，最大值大約是實體記憶體的一半左右。]]> http://www.andowson.com/posts/preList/30/104.page http://www.andowson.com/posts/preList/30/104.page GMT