RFR (S): JEP-142: Reduce Cache Contention on Specified Fields

[Doug Lea]

(Warning: cross-posting, so replies may bounce to one or both lists.)

> However, this still has a drawback that the subclass annotation will
> only affect the fields in the subclass, and not in the superclasses
> (laying the superclass fields on the same offsets in the subclass is
> important to get cheap polymorphism).


Considering that the only usages with predictable effects will be
on leaf/final classes anyway, perhaps the @Contended annotation
should only have a defined effect on layout when applied to final
classes (plus statics). This also seems to be the only case when a
developer can have an empirical basic for using the annotation.
And if there someday turns out to be some reason to lift this
restriction, it would be possible to do so.

-Doug