jdk1.6内存布局 [英] jdk1.6 memory layout

问题描述

我正在使用jdk1.6。我配置
Xmx = 2G，Xms = 2G，NewSize = MaxNewSize = 660m

我启用详细的gc。我看到这我不undertsnaidng：

  PSYoungGen总计608256K，使用32440K 
 eden空间540672K，使用6％ 
来自空间67584K，0％使用
到67584K空间，0％使用
  

根据我的配置，YoungGen的大小是675840MB。
因为younGen =伊甸园+两个幸存者空间，所以

GC日志说我的YoungGen大小= 608256K这不是我配置的。
另外，如果我添加Eden空间和两个生存空间，我得到
540672K + 67584K + 67584K = 675840K

这也是错误的。 p>

但是Eden + 1幸存者空间= 540672K + 67584K = 675840K，我已经配置了。
那么这是否意味着YoungGen = Eden + 1幸存者空间？我认为有
两个幸存者空间，对吗？

请解释我。

感谢您

解决方案

有两个幸存者空间，但在任何给定时间只有一个空间;每当有年轻一代的垃圾收集时，物体就会从一个幸存者空间来回移动到另一个。因此，您配置的年轻一代空间等于伊甸园空间加上一个的幸存空间;另一个基本上只是开销。

i am using jdk1.6. I configureg Xmx = 2G, Xms= 2G, NewSize = MaxNewSize = 660m

I enable verbose gc. I see this which I am not undertsnaidng:

PSYoungGen      total 608256K, used 32440K 
 eden space 540672K, 6% used 
 from space 67584K, 0% used 
 to   space 67584K, 0% used 

According to my configuration YoungGen size is 675840MB. Because younGen = Eden + two survivor spaces,

GC log saying that my YoungGen size = 608256K which is not what i've configured. Also if I add Eden space and two survivor spaces I am getting 540672K + 67584K + 67584K = 675840K

which is also wrong.

But Eden + 1 Survivor space = 540672K + 67584K = 675840K, what i have configured. So does this mean that YoungGen = Eden + 1 Survivor space? I think there are two survivor space, correct?

Please explain me.

thanking you

解决方案

There are two survivor spaces, but only one is used at any given time; objects get moved back and forth from one survivor space to the other every time there's a young-generation garbage-collection. So your configured young-generation space is equal to the eden space plus one of the survivor-spaces; the other is basically just overhead.

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