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Resident memory of java application

868448Jun 13 2011 — edited Jun 14 2011
Hi,

When I start my application, I have set max heap size as 2 GB (-Xmx2048M). Since I set max heap size as 2 GB, the resident memory of the java application should be less than 2.5 GB ( Max Heap + Jars Memory + VM Memory ). But the resident memory of the java application is keep increasing (4+ GB) without throwing OutOfMemory error. When I see the java heap memory usage using JMX, it shows only 1.6 GB. The gc.txt log also shows only 1.6 GB.

I assume, there is no memory leak in my java code because of below reasons,

There is no OutOfMemroy error, even though java resident memory shows 4+ GB.
The JMX stats shows memory heap size as 1.6 GB.

I don't why the resident memory of the java application keep increasing without OutOfMemory. As per my knowledge, there are 2 cases this will happen,

If the java app triggers any process using Runtime.getRuntime() and the process has memory leak
If the java app triggers any native call (JNI) and the native implementation has memory leak

In my case, my java app neither use any Runtime.getRuntime() method call nor my own native implementation call. But the resident memory of my java app is keep increasing without OutOfMemory error.

My Setup Details :

JDK : java version "1.6.0_16" - Java(TM) SE Runtime Environment (build 1.6.0_16-b01)
OS : Linux x.x.x.x 2.6.18-194.11.4.el5 #1 SMP Tue Sep 21 05:04:09 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux
Java GC Options : -Xmx2048M -Xms2048M -XX:+UseConcMarkSweepGC -XX:+HeapDumpOnOutOfMemoryError -verbose:gc -Xloggc:../logs/gc.txt -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCApplicationConcurrentTime -XX:+PrintGCApplicationStoppedTime

Can you please help me to solve this issue ? Kindly let me know, if you require any other information.

Thanks,
Ramesh

Comments

EJP
Since I set max heap size as 2 GB, the resident memory of the java application should be less than 2.5 GB ( Max Heap + Jars Memory + VM Memory ).
Only if you assume the latter two items take up <= 0.5GB each. Do they?
868448
EJP wrote:
Since I set max heap size as 2 GB, the resident memory of the java application should be less than 2.5 GB ( Max Heap + Jars Memory + VM Memory ).
Only if you assume the latter two items take up <= 0.5GB each. Do they?
I am not 100% sure. Just gave worst case assumption. If my code base/jar is high, I should get java.lang.OutOfMemoryError: PermGen space. right ? Do you have any idea ?
802316
What is your maximum direct memory? By default its the same as the heap memory maximum. This can give you a maximum size of 2 GB (heap) + 2 GB (direct) + 0.5 - 1.0 GB for the rest.

BTW: I would try updating your JVM, it is 10 updates behind current.

If you do that, something which can reduce memory consumption without too much overhead is -XX:+UseCompressedOops and -XX:+UseCompressedStrings
1 person found this helpful
EJP
I am not 100% sure. Just gave worst case assumption.
No you didn't. It isn't a 'worst case assumption'. It's just a guess. The true figure might be higher. That's my point. In this case obviously something is a lot higher. The current case is worse than your 'worst case'.
If my code base/jar is high, I should get java.lang.OutOfMemoryError: PermGen space. right?
Among other possibilities. But there is also the question of how much memory the JVM itself needs.
JRK wrote:
....without throwing OutOfMemory error.
...
Can you please help me to solve this issue ? Kindly let me know, if you require any other information.
What is the "issue" exactly?

Since there is no OOM that certainly isn't the issue.
So explain in detail why you think what you are seeing is a problem - specifically what impact it is going to have.
868448
Thanks to all for your help.
No you didn't. It isn't a 'worst case assumption'. It's just a guess.
Yes. It is just a guess not worst case assumption.
jschell wrote:
JRK wrote:
....without throwing OutOfMemory error.
...
Can you please help me to solve this issue ? Kindly let me know, if you require any other information.
What is the "issue" exactly?

Since there is no OOM that certainly isn't the issue.
So explain in detail why you think what you are seeing is a problem - specifically what impact it is going to have.
My server m/c has 8 GB RAM and I am running 2 instance of my java application in that m/c. Since each instance of memory goes to 4 GB, the m/c is not reachable. Because no more memory is available for open ssh session.
What is your maximum direct memory? By default its the same as the heap memory maximum. This can give you a maximum size of 2 GB (heap) >+ 2 GB (direct) + 0.5 - 1.0 GB for the rest.
I didn't mention anything. So it should be default ( 2GB). Thanks Peter Lawrey. Now, I understand that, the memory wiIl go upto 5GB in my case.

Thanks,
Ramesh
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Locked on Jul 12 2011
Added on Jun 13 2011
#java-virtual-machine-jvm
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