RFR: 8268349: Provide more detail in JEP 411 warning messages

[Weijun Wang]

On Tue, 8 Jun 2021 17:15:29 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> I thought about that but not sure of performance impact. Is the worst problem that more than one warnings will be printed for a single caller? It's not really harmless.
>> 
>> As for the frame, if the warning message only contain the caller class name and its code source, why is it worth using a key of multiple frames? The message will look the same.
>
>> I thought about that but not sure of performance impact. Is the worst problem that more than one warnings will be printed for a single caller? It's not really harmless.
>> 
>> As for the frame, if the warning message only contain the caller class name and its code source, why is it worth using a key of multiple frames? The message will look the same.
> 
> WeakHashMap access needs synchronization. Whether we need to cache to avoid excessive warnings isn't clear. If the SM is enabled once and never disabled/re-enabled then caching isn't interesting.  On the other hand if there are programs that are enabling/disabling to execute subsets of code then maybe it is. Maybe we should just drop this and see if there is any feedback on the repeated warning?

Not sure what you meant by "WeakHashMap access synchronization", it's just a noun without any other parts. Do you think synchronization is necessary?

For the cache, I'm OK to drop it at the moment.

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PR: https://git.openjdk.java.net/jdk/pull/4400