RFR: 6203: Add ZGC allocation stall rule

[Marcus Hirt]

On Wed, 9 Jul 2025 14:17:10 GMT, Suchita Chaturvedi <schaturvedi at openjdk.org> wrote:

> This enhancement is to add new rule for ZGC Allocation Stall events.
> 
> The default configuration:
>  
> <img width="946" alt="image" src="https://github.com/user-attachments/assets/0d39ae26-fdc4-49e3-a0ed-fb7f7da8f709" />
> 
> Here are few screenshots for reference:
> 
> <img width="344" alt="image" src="https://github.com/user-attachments/assets/e7efe1e2-d6b3-4a05-8ea6-1bf2e8b8c15f" />
> 
> <img width="353" alt="image" src="https://github.com/user-attachments/assets/a3d3862f-96d2-4292-947f-4562c7f9f3d3" />
> 
> <img width="344" alt="image" src="https://github.com/user-attachments/assets/9616eea6-bce8-4395-a846-db343fe349f2" />
> 
> <img width="341" alt="image" src="https://github.com/user-attachments/assets/376a100e-ac05-48fe-a9c3-754923c3d79e" />
> 
> <img width="353" alt="image" src="https://github.com/user-attachments/assets/cfa7c5f1-08f0-44b4-a49d-28504439a631" />
> 
> Ignored
> 
> <img width="352" alt="image" src="https://github.com/user-attachments/assets/3c00c22e-e64d-46b0-8b64-ed653ed1fc4b" />
> 
> If we change default configuration as below:
> 
> <img width="367" alt="image" src="https://github.com/user-attachments/assets/8da64985-8446-44b8-bfb4-696a726b5255" />
> 
> <img width="350" alt="image" src="https://github.com/user-attachments/assets/ad89f02e-39b4-4df4-aae7-43cec9cc9a91" />
> 
> <img width="347" alt="image" src="https://github.com/user-attachments/assets/b3ec1081-26dd-4391-9e0f-0b4c64a7e3c1" />
> 
> <img width="344" alt="image" src="https://github.com/user-attachments/assets/106a7c3e-aaaf-495a-8c6f-281c96371e6e" />

I would be wary about making the heuristic dependent on the number of stall events per recording. Perhaps we can find a better thing to look at, that is unrelated to the length of the recording? For example, how long a particular thread has been stalled per minute, or the longest time a thread was stalled (or both)?

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PR Comment: https://git.openjdk.org/jmc/pull/664#issuecomment-3069639323