RFR: 8319955: Improve dependencies removal during class unloading

[David Holmes]

On Mon, 13 Nov 2023 18:52:47 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   please review this performance improvement to dependency removal during class unloading: instead of moving the dependencies item by item via a `cmpxchg`, batch this operation.
> 
> This makes that part of class unloading ~7x faster in my measurements (class unloading stress test, loading/unloading 6k classes).
> 
> Testing: tier1-7
> 
> Thanks,
>   Thomas

So this batches the operation by moving the batch to the purge list, but it doesn't actually release anything. Who/what will process the purge list and when? The implications of this change in terms of concurrent activities is far from clear.

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PR Comment: https://git.openjdk.org/jdk/pull/16639#issuecomment-1809705815