Strange behaviour in DeferredCompletionFailureHandler (original) (raw)

Jan Lahoda jan.lahoda at oracle.com
Mon Nov 12 15:57:22 UTC 2018

Hi Dmitry,

The overall goal is to avoid CompletionFailures to be thrown to the user code. This requires to "spit" a Symbol into user code version and an javac internal version and to use the user-code version while in user code, and javac internal version while in javac. (Because javac needs the CompletionFailures for correctness.)

There was an issue that even "hypothetical" Symbol were kept in the maps, which should be fixed now. Please see: https://bugs.openjdk.java.net/browse/JDK-8209055

Please let me know how it works in your usecase.

Thanks, Jan

On 12.11.2018 16:10, Dmitry Batkovich wrote:

Hi all,

I've faced with javac 11 performance problem in DeferredCompletionFailureHandler. I have a project with google dagger dependency injection and with some javac task listener (You may see https://youtrack.jetbrains.com/issue/IDEA-201978). In this case I see lots FlipSymbolDescription#flip() traces in compiler profile snapshot. I've tried to investigate the problem by myself and found next things: 1) Map com.sun.tools.javac.code.DeferredCompletionFailureHandler.Handler#class2Flip produces memory leaks because keys of the map are present as a part of value object. So, keys are always strongly referenced. And usage of WeakHashMap is useless here. 2) com.sun.tools.javac.code.DeferredCompletionFailureHandler.Handler#class2Flip does nothing. Any information inside FlipSymbolDescription is never used (DefferedCompleter is never used). 3) Handler.install/uninstall method usages (see setHandler() usages in MultiTaskListener) produces lots of odd cycles where we have only field reassignment. Sure we need at least one TaskListener here. So, I've found that fix for https://bugs.openjdk.java.net/browse/JDK-8187950 is very dirty in point view of compiler performance. And I don't understand what's the purpose of class2Flip map introduction. Could you clarify, help me, please? Cheers, Dmitrii Batkovich

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