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JRE 7 Update 7 Performance Problem

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sanjay_dasgupta
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Joined: 2003-11-26

I was testing VisualLangLab with the new JRE (7 Update 6), and found a significant performance degradation.

When used to parse all the source files of the JDK as described in A Java7 Grammar for VisualLangLab, the tool finishes parsing the 7000+ file in about 9 minutes with the old (7 Update 5) JRE using the hardware and environment described in the blog.

But with the latest JRE (7 Update 6), it barely finishes processing 1000 files in 10 minutes.

A quick check with jconsole (see figures below) showed no major differences, so will now have to dig in with a profiler.

I have not seen any relevant bug reports, any hints you can give me will be helpful.

Old (7u5) JRE

The screenshot below shows the JConsole view after completion of run with the old (7u5) JRE.
This is the expected behavior (processes 7000+ files in about 10 minutes).

7u5 jconsole view

Latest (7u6) JRE

The screenshot below shows the JConsole view when running under the latest (7u6) JRE.
Though the details in Jconsole are not much different (VisualLangLab manages to process just about 1000 files in 10 minutes).

7u6 jconsole view

Other Details

VisualLangLab is compiled and built under JDK 7u6 (the latest JDK), but for a target of "6".

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csitx
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Joined: 2012-09-13

this might be relevant

A comparison of the String.java code between 7u5 and 7u6 indicates the implementation is completely different. The contents are now copied on every substring operation!