RFR: 8281318: Improve jfr/event/allocation tests reliability

[Markus Grönlund]

On Mon, 7 Feb 2022 09:34:15 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This fixes the failure on x86_32 by resolving an object/TLAB "sizing" problem. On x86_32, the 100K object gets 200K TLAB, which allocates the next object exactly in the same TLAB. Bumping the object size to 128K resolves this.
> 
> Additionally, rewired the tests to match object sizes exactly. In modern JDK, the header size depends on `UseCompressedClassPointers`, not on `UseCompressedOops`. Using `Whitebox`, we can poll the VM configuration exactly.
> 
> Additional testing: 
>  - [x] Linux x86_32 fastdebug, `jfr/event/allocation/`
>  - [x] Linux x86_64 fastdebug, `jfr/event/allocation/`, out of the box
>  - [x] Linux x86_64 fastdebug, `jfr/event/allocation/`, with `-XX:-UseCompressedClassPointers`

Can you take a look at this, https://bugs.openjdk.java.net/browse/JDK-8281638?

-------------

PR: https://git.openjdk.java.net/jdk/pull/7365