On Thu, 17 Jul 2025 21:20:06 GMT, Phil Race <p...@openjdk.org> wrote:
>> I tried to compare how Cleaner and Disposer are used. I found that in most >> cases Cleaner uses `this` as the object to track. But Disposer often uses a >> separate object like disposerReferent or some kind of anchor. This patch is >> one example. In some places we even replaced this with a different object. >> You can see that in the following RFR: >> https://bugs.openjdk.org/browse/JDK-8030099 >> https://mail.openjdk.org/pipermail/swing-dev/2015-October/005053.html >> >> I think I found the reason: https://bugs.openjdk.org/browse/JDK-8071507 >> >> In older versions of the JDK the Disposer had to use phantom references. >> Phantom references allow native cleanup to happen after the object is 100% >> no longer reachable. But this had a problem, the object stayed in memory >> until the reference was added to the queue and the code called >> [clear](https://github.com/openjdk/jdk/blob/bc72f476d1281dae2adb2322004c9880c1a6b66c/src/java.desktop/share/classes/sun/java2d/Disposer.java#L134). >> >> To avoid keeping large AWT or Java2D objects in memory for too long the code >> used small helper objects as referents instead of using the real object. >> >> Now the problem described in JDK-8071507 is fixed. So maybe we no longer >> need to use small disposer referents. And you can check that by the test >> from the description of this PR. > > I know this is possible, but I'd prefer to keep this pattern. This way It is > crystal clear that nothing to do with reference queues etc are delaying the > GC from immediately reclaiming the memory. > Honestly, it probably matters not so much for JRSUIControls, and even less so > for CGraphicsEnvironment, but may matter for some other cases. > > A later follow-up fix could go change a whole bunch of these cases at once > and we'd then have a good reference (pun intended) as to whether any issues > showed up. sounds good ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/26331#discussion_r2214413658
