CODEWITHSUNDEEP
javamemory-managementjvmjvm-arguments
yaccob
yaccob

Reputation: 1333

Can a java application allocate more memory than specified by jvm startup parameters?

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?

Upvotes: 2

Views: 2235

Answers (3)

Ivo
Ivo

Reputation: 444

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.

Upvotes: 2

Piotr Kołaczkowski
Piotr Kołaczkowski

Reputation: 2629

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.

Upvotes: 2

DeadlyFugu
DeadlyFugu

Reputation: 152

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.

Upvotes: -1

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