RFR: 8333047: Remove arena-size-workaround in jvmtiUtils.cpp

[Thomas Stuefe]

On Wed, 29 May 2024 07:42:01 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> In `JvmtiUtil::single_threaded_resource_area()`, we create a resource area that is supposed to work even if the current thread is not attached yet and there is no associated Thread or the Thread has no valid ResourceArea.
>> 
>> It contains a workaround:
>> 
>> 
>>     // lazily create the single threaded resource area
>>     // pick a size which is not a standard since the pools don't exist yet
>>     _single_threaded_resource_area = new (mtInternal) ResourceArea(Chunk::non_pool_size);
>> 
>> 
>> It specifies a non-standard chunk size to circumvent the chunk-pool-based allocation in the RA constructor, ensuring that only malloc is used. This is because in the old days the ChunkPools had been allocated from C-Heap and there was a time window when no chunk pools were live yet.
>> 
>> This is quirky and a bit ugly. It is also unnecessary since [JDK-8272112](https://bugs.openjdk.org/browse/JDK-8272112) (since JDK 18). We now create chunk pools as global objects, so they are live as soon as the libjvm C++ initialization ran. We can remove this workaround and the comment.
>> 
>> ---
>> 
>> Tests: GHAs.
>> I also manually called this function, and allocated from the resulting ResourceArea, at the very beginning of CreateJavaVM. I made sure that both allocations and follow-up-chunk-allocation worked even this early in VM life.
>
> Today, the ChunkPools are allocated before main through static initialization. That means that the ChunkPools exists when main starts executing, so this is safe.

Thanks @jdksjolen and @sspitsyn !

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PR Comment: https://git.openjdk.org/jdk/pull/19425#issuecomment-2141338912