Can a java application allocate more memory than specified by jvm startup parameters?
Question
Assuming a java application is not using any native libraries. Is there a way that it anyway can allocate more memory than specified by jvm startup parameters?
Asking the other way round: Can I rely that a java application will never allocate more memory than restricted by JVM startup parameters?
3 answers
solution1
2 2013-09-24 09:50:54
Yes, it can. It cannot allocate more memory on the JVM heap, but it can allocate native memory by using ByteBuffer.allocateDirect or by calling to custom native code.
solution2
2 2013-09-25 07:32:01
Indeed, you always need more memory than the -Xmx specified in your startup script. GC internals, JIT optimization tables, off heap allocations, permgen, thread stacks, etc are all taking their toll.
solution3
-1 2013-09-24 09:47:41
No, a Java application can not go beyond the size specified by -Xmx . It wouldn't make much sense if it could - why bother having -Xmx in the first place, then?
I found an interesting link on Dream.In.Code where a user has given an example of a program that manages to resize itself, but it works by spawning a new JVM process.
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