Anony-Mousse Anony-Mousse - 1 year ago 158
Java Question

Java 7 and -XX:TraceDeoptimization

I'm trying to debug Java deoptimization, but I can't get

to work. Do you know if it was disabled in OpenJDK 7, or maybe is not enabled in my version (7u9-2.3.4-0ubuntu1.12.04.1), or if there is some magic
that I need to call?

No matter what I try, I always get the error message

Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

without any further details when I add this parameter. Even a plain
java -XX:+TraceDeoptimization
prints this message. It doesn't say it does not recognize the option, either. However, as
reveals, I'm seeing a "made not entrant" messages, which apparently indicate a deoptimization, and I'd like to debug why this is happening, as I'm seeing an odd performance drop with supposedly improved code.


The default builds indeed do not include this functionality. You need a debug build. You can find some with Google on

Answer Source

All flag options require a + or - to enable or disable them. In your case the option would be -XX:+TraceDeoptimization To turn it off (which is the default) you can write -XX:-TraceDeoptimization

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