[master] RFR: Implement non-racy fast-locking [v3]

[Roman Kennke]

On Wed, 27 Jul 2022 21:16:06 GMT, David Holmes <dholmes at openjdk.org> wrote:

> > I also intend to upstream this change (minus the Lilliput-specific parts) soon, that will help Lilliput upstreaming and later on the JOM project.
> 
> I would need a lot of convincing that we should be doing anything upstream in this area "soon" given the current status of the two projects, but look forward to seeing such a proposal and its performance etc.

I don't know about JOM's status, because unfortunately the project is not public (otherwise I wouldn't have had to re-do it). Lilliput is at a point where I'm planning to start upstreaming it so that 64bit headers can make it into JDK21. And the new locking scheme would be one of the first prerequisite steps towards that goal. Performance in Lilliput: see above. I'd expect it to be neutral outside of Lilliput because there the benefit of faster load-Klass does not exist, and the benefit of faster i-hash is probably not significant.

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PR: https://git.openjdk.org/lilliput/pull/51