JDK6 YoungGen Layout

[Srinivas Ramakrishna]

On Wed, Mar 28, 2012 at 12:33 PM, Kobe Bryant <kbbryant61 at gmail.com> wrote:

>
>
>   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 understanding:
>
>
> 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,
> which matches my understanding what the YoungGen size should be.
>
> 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
>
> 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?
>

You are right. For historical reasons, the JVM produces under "total" for
young gen, only that space
that can have objects. Since only one of the survivor spaces (and Eden) can
hold java objects at any
one time, the message states that that's the "size" of the young gen.

Hope that helps clear the confusion. (Ask again if i did not understand yr
question.)
-- ramki


> Please explain me.
>
> thanking you
>
>
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