RFR: 8290344: Start/stop displaysync affects performance in metal rendering pipeline [v2]

[Jayathirth D V]

On Wed, 24 Aug 2022 13:37:16 GMT, Alexey Ushakov <avu at openjdk.org> wrote:

>> Reuse displaysync thread for subsequent updates
>
> Alexey Ushakov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains one additional commit since the last revision:
> 
>   8290344: Start/stop displaysync affects performance in metal rendering pipeline
>   
>   Reuse displaysync thread for subsequent updates

Stopping DisplayLink once we are done with blitting was used to fix https://bugs.openjdk.org/browse/JDK-8259038 . I think with displayLink active count as 4 we might see unnecessary(~4) displayLink callbacks when we just draw text and leave it as noticed in the bug.  But i think this tradeoff is fine as we are trying to achieve balance between power and performance.

Also this change should not cause state management issues as we are just maintaining displayLink for longer time. @avu Could you please verify that we are not seeing issues like https://bugs.openjdk.org/browse/JDK-8247332 ?

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PR: https://git.openjdk.org/jdk/pull/9512