Hi Kim,
Thanks for pushing this through! Looks good. Bengt On 2015-12-02 19:37, Kim Barrett wrote:
Please review this change to PhantomReference processing, changing the GC-based notification to automatically clear the referent. This change provides performance benefits by eliminating the work involved in keeping the otherwise inaccessible referent objects alive, as required by the existing specification. This not only immediately removes some work, but may enable further performance improvements. It also allows the referent objects to be immediately reclaimed in the GC cycle in which they were determined to be inaccessible, rather than lingering as a form of floating garbage until the application deals with the notified reference. This change results in a behavioral change to application code, as demonstrated by the associated test. Under the old specification, a reference R with referent X may be kept alive because it is referenced by an otherwise inaccessible referent Y of phantom reference P. This will result in X being treated as strongly referenced and prevent R from being notified, even if R is a phantom reference and X has become inaccessible to the application. With this change, Y is reclaimed when it becomes inaccessible and P is notified, and no longer prevents X from itself becoming a candidate for reclaimation once it is no longer accessible to the application. While this is a change in behavior, it seems unlikely to affect applications negatively. CR: https://bugs.openjdk.java.net/browse/JDK-8071507 Webrevs: http://cr.openjdk.java.net/~kbarrett/8071507/jdk.05/ http://cr.openjdk.java.net/~kbarrett/8071507/hotspot.05/ Testing: jprt, aurora ad hoc (defaults, GC/Runtime nightly, JCK)
