How is HotSpot profiled and debugged?

[Julian Waters]

Hi all,

Anyone who has seen JDK-8288293 (https://bugs.openjdk.org/browse/JDK-8288293)
might probably be intrigued to learn that gcc has been able to compile a
complete, somewhat functioning Windows JDK for somewhat over a month by
this point. There is an unfortunate catch: The experimental HotSpot
produced by gcc in this manner is extremely volatile and unstable, often
suddenly spiking CPU usage to 100% and devouring system resources at
completely random moments, causing the entire system (not just the Java
process itself, per se) to freeze as a result of the immense strain
suddenly placed on it

The question I have is: How do HotSpot developers debug and profile HotSpot
in cases where bugs or performance hits like this occur? I don't have much
experience working with HotSpot as of yet, so I don't quite know where to
start in tackling this issue. Any tips on what to do in dealing with this
performance issue would be greatly appreciated!

best regards,
Julian
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