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eclipse-jdt / eclipse.jdt.core

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Inefficient memory org.eclipse.jdt.internal.compiler.ClassFile #2950

Closed jukzi closed 1 day ago

jukzi commented 5 days ago

During an OOME building a large project i find ~1GB is allocated for org.eclipse.jdt.internal.compiler.ClassFile. That seems unnecessary for several reasons:

First observation was that different Classfile instances had the exact same amount of retained memory: image

Also JFR reports 2 ~ GB overhead due to duplicate Arrays used in ClassFile and its members: image

Focusing on CharArrayCache one sees the duplicate arrays are mostly filled with 0 bytes and have the initial size of the ContantPools (defined in ConstantPool.UTF8_INITIAL_SIZE / STRING_INITIAL_SIZE ...): image

Focusing on ClassFile.header or ClassFile.bytes it is visible that most of those arrays are duplicates - i did not find an explanation for that yet. image image

jukzi commented 5 days ago

Please note that the underlying Problem for OOME seems to be a leak in the current hibernate annotation processor and this ticket is only observation where memory could be reduced in JDT.