Questions

[652053395]

Hello, I have run the project "mysafe" , and I have some questions, looking for your help.

Why when I run the method unsafe.allocatememory() , it would go to the method MysafeDelegator.allocateMemory()?

How the program detects the implementation of the method unsafe.allocatememory()?

And I used the method "ByteBuffer.allocateDirect()" to allocate direct memory, but it could not be detected.

Thanks for your help!!

[serkan-ozal]

Hi @652053395,

Answers are inline:

Why when I run the method unsafe.allocatememory() , it would go to the method MysafeDelegator.allocateMemory()?

Yes, unsafe.allocatememory() is redirected to MysafeDelegator.allocateMemory()

How the program detects the implementation of the method unsafe.allocatememory()?

Application classes are inspected and at bytecode level Unsafe calls are replaced by MysafeDelegator calls

And I used the method "ByteBuffer.allocateDirect()" to allocate direct memory, but it could not be detected.

Currently only application classes are taken care of. Classes, such as DirectByteBuffer, loaded by the bootstrap classloader are ignored.
https://github.com/serkan-ozal/mysafe/blob/master/src/main/java/tr/com/serkanozal/mysafe/impl/processor/MySafeProcessor.java#L19
(if the class is loaded by the bootstrap classloader, loader is null here)

[652053395]

Thanks for your answering , it helps me a lot !!

I still have some questions. So Instead of directly monitoring the Class "Unsafe" or the method Unsafe.allocateMemory(), it just monitors the classes (application classes) which call the method Unsafe.allocateMemory() ?

If the classes are loaded before the agent, they could not be monitored?

As I know, the Class Unsafe is also loaded before the agent, so I still wonder how the program knows the method Unsafe.allocatememory() is called?

And Is there any way we could directly get the total direct memory usage (or directly monitor the method Unsafe.allocateMemory() ) when it is called ? (Since there might be some other system Classes calling this method)