Re: What is the difference between Memory Usage and Heap Usage in
my JVM Metrics ?
On 08-02-2010 20:15, Krist wrote:
On 9 Feb, 08:09, Arne Vajh?j<a...@vajhoej.dk> wrote:
On 08-02-2010 18:08, Krist wrote:
In my Apps Server console (OC4J) JVM Metrics, there are two columns
about memory :
Memory Usage (MB) -> Shows the amount of physical memory used by the
JVM.
Heap Usage (MB) -> Shows the amount of heap space used by the
JVM.
(heap usage seems to be up and down, but memory usage is never going
down, even when all user already loggout.)
What are the difference between the two ?
I will guess that:
memory usage = memory the JVM has allocated from the OS
heap usage = memory your app has allocated from the JVM
With two points:
1) the JVM need memory for internal stuff so memory usage
is greater than heap usage
2) even if your app releases memory then the JVM may not
release it to the OS but keep it around just in case
you will need it again
So, is it only the heap area that I can tune ? (GC& Memory leak)
How can I also tune the 'memory for internal stuff' usage ?
I don't think you have much control over what the JVM use for
itself and for byte code and JIT'ed code.
Arne
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