Integrated: 8329134: Reconsider TLAB zapping

[Aleksey Shipilev]

On Tue, 26 Mar 2024 21:08:16 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> We zap the entire TLAB on initial allocation (`MemAllocator::mem_allocate_inside_tlab_slow`), and then also rezap the object contents when object is allocated from the TLAB (`ThreadLocalAllocBuffer::allocate`). The second part seems excessive, given the TLAB is already fully zapped.
> 
> There is also no way to disable this zapping, like you would in other places with the relevant Zap* flags.
> 
> Fixing both these issues allows to improve fastdebug tests performance, e.g. in jcstress. 
> 
> It also allows to remove the related Zero kludge.
> 
> Additional testing:
>  - [x] Linux AArch64 server fastdebug, `all` tests 
>  - [x] MacOS AArch64 Zero fastdebug, `bootcycle-images` pass

This pull request has now been integrated.

Changeset: 5698f7ad
Author:    Aleksey Shipilev <shade at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/5698f7ad29c939b7e52882ace575dd7113bf41de
Stats:     30 lines in 5 files changed: 5 ins; 16 del; 9 mod

8329134: Reconsider TLAB zapping

Reviewed-by: stefank, rkennke

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PR: https://git.openjdk.org/jdk/pull/18500