the memory usage of hotspot vm itself

[Jon Masamitsu]

For GC there are data structures that the VM maintains that are
proportional to the size of the heap.  For example to facilitate
young gen collections there is a card table which is used to
find references from the old generation to the young generation
and the size of the card table is proportional to the size of
the heap.  Depending on the collector in use, there are
bitmaps that are also proportional to the size of the heap.

Is that what you are asking?

On 3/1/2012 3:13 AM, Li Li wrote:
>      I have an application running in a machine with 6 GB memory. And the
> java program is allocated to use 4000M heap by -Xmx4000m and -Xms4000m. But
> we found it use swap memory and system get slower.
> When swapping, the total memory used by the java process is 4.6GB(use top
> res 4.6G and virt 5.1G)
>     I know Direct Buffer used by NIO, PermGen and stack is not limited by
> Xmx. we limit stack 256k and 400 threads in peak. so it will use 80MB
> memory and MaxPermSize is 256MB. MaxDirectMemorySize is default. I think is
> 64MB
> all sumed up is about 3400MB. so JVM itself will need more than 200MB.
>     any one tell me why JVM need more than 200MB memory?(I don't mean jvm
> should not use that much memory). how could I estimate the memory usage of
> JVM itself? thanks.
>
>
>
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