To answer the original poster’s question, “maybe.” Here’s a note I
posted to the Jackson JSON java lib mailing list about an odd jvm
crash/hang. The system hangs only under the Java6 64-bit vm. I tried
running the same tests under the Java5 64-bit vm and it behaved
normally. The 32-bit vm (for Java5 or Java6) always behaved correctly.
I don’t know if this is a jruby bug (doubtful) or a general JVM
problem. The “cure” was to increase the stack size with -Xss but that
can be very wasteful in a multi-threaded environment.
I’ll try to do a test against a 64-bit vm under linux to see if I get
the same hang. If I do, then there is something here that needs
investigation. If it runs okay, then the problem is likely attributed
to Apple’s VM.
------ pasted -----
Here’s a link  to the ruby benchmark program I wrote along with the
benchmark results pasted at the bottom. I put the Jackson JSON Java
lib up against the json-jruby library which is a ruby library with
some native Java for use under jruby. All benchmarks were performed on
a Mac Pro with 16GB RAM, dual quad-core 2.8 GHz, on Java6.
cremes$ java -version
java version “1.6.0_07”
Java™ SE Runtime Environment (build 1.6.0_07-b06-153)
Java HotSpot™ 64-Bit Server VM (build 1.6.0_07-b06-57, mixed mode)
Interestingly, I needed to boost the stack size (-Xss) to 4m for the
benchmark to complete otherwise the java process would randomly hang.
The hang behaves very similar to an old Sun bug  which is perhaps
still open on Apple’s JVM.
For those who don’t want to click on the pastie, Jackson was about 3
times faster at generating JSON strings and roughly twice as fast at
parsing JSON strings.
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