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Java memory allocation alignment

Tags:

java

memory-management

memory-alignment

I know this is a weird question to ask in Java, but is there a way to let Java dynamic memory allocation be aligned with some alignment constraints? For example, is it possible to dynamically allocate objects that are aligned with the page size?

The reason I want to do this is because I'm going to access the Java object from native code through JNI interface, and the native code library requires the object to be aligned.

Thanks.

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Neo Hpcer Avatar asked Mar 11 '11 01:03

Neo Hpcer

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1 Answers

No it is not possible. Keep in mind that objects on the heap in Java can move around during garbage collection. You have some options:

  1. Stop accessing Java objects directly from JNI. Copy what you care about into a JNI-provided buffer that the native code has already aligned.
  2. Use ByteBuffer.allocateDirect(). Then find a region of your buffer that is correctly aligned. One way to do that is to allocate the buffer at startup and repeatedly attempt the alignment sensitive operation at different offsets until it works. This is a hack!
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Spike Gronim Avatar answered Oct 03 '22 23:10

Spike Gronim
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