Java 7 and -XX:TraceDeoptimization

Question

I'm trying to debug Java deoptimization, but I can't get -XX:+TraceDeoptimization 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 -XX:+unlockSomething 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 PrintCompilation 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.

Solution:

The default builds indeed do not include this functionality. You need a debug build. You can find some with Google on jdk7.java.net.

score 0 · Answer 1 · answered Jan 22 '13 at 16:17

0

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

answered Jan 22 '13 at 16:17

Peter Lawrey

525,659
79
751
1,130

That actually is what I tried. Sorry for the copy & paste above. It doesn't work here. – Has QUIT--Anony-Mousse Jan 22 '13 at 16:18
On a side note, `-XX:-TraceDeoptimization` causes the same error. – Has QUIT--Anony-Mousse Jan 22 '13 at 16:25
It might be disabled in that version. I would try the Oracle Hotspot Java 7. – Peter Lawrey Jan 22 '13 at 16:31
Oracle Java 7 says: `Unrecognized VM option 'TraceDeoptimization'`. Which at least is an error message, although it doesn't help me debugging this performance regression... any idea which version of Java actually supports this kind of debugging? – Has QUIT--Anony-Mousse Jan 22 '13 at 16:50
I know they do a "debug" release with mreo options, but you may have to build one yourself as they don't do it very often. – Peter Lawrey Jan 22 '13 at 17:16
1

With Google I found a JDK7 debug build on java.net, and this one indeed includes the option. Thank you. – Has QUIT--Anony-Mousse Jan 22 '13 at 17:41
You should be able to build this version yourself but I don't know how. – Peter Lawrey Jan 22 '13 at 18:11

score 0 · Accepted Answer · answered Jun 18 '16 at 13:31

0

The default builds indeed do not include this functionality.

You need a debug build. You can find some with Google on jdk7.java.net.

answered Jun 18 '16 at 13:31

Has QUIT--Anony-Mousse

76,138
12
138
194

user2179737 · Answer 3 · 2016-06-18T13:44:15.057

-1

This option is available only in the debug version of the VM. (at least that is what my idk 1.8u92 is telling me.

edited Jun 18 '16 at 13:44

answered Jun 18 '16 at 12:37

user2179737

493
3
6

Java 7 and -XX:TraceDeoptimization

Solution:

3 Answers3