How is HotSpot profiled and debugged?

[David Holmes]

On 23/06/2023 8:21 pm, Julian Waters wrote:
> Hi all,
> 
> Anyone who has seen JDK-8288293 
> (https://bugs.openjdk.org/browse/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!

I can't say I have any specific advice for this situation. You have 
basically used a "new" compiler to build a Windows JDK and it doesn't 
work. That is not a situation we normally need to debug.

About the only advice I could give would be to disable all optimisations 
in the compiler and see how that goes.

Sorry.

David


> best regards,
> Julian