On Fri, 10 May 2024 10:06:55 GMT, Alan Bateman <al...@openjdk.org> wrote:
> This is the implementation changes for JEP 471. > > The methods in sun.misc.Unsafe for on-heap and off-heap access are deprecated > for removal. This means a removal warning at compile time. No methods have > been removed. A deprecated message is added to each of the methods but > unlikely to be seen as the JDK does not generate or publish the API docs for > this class. > > A new command line option --sun-misc-unsafe-memory-access=$value is > introduced to allow or deny access to these methods. The default proposed for > JDK 23 is "allow" so no change in behavior compared to JDK 22 or previous > releases. > > A new test is added to test the command line option settings. The existing > micros for FFM that use Unsafe are updated to suppress the removal warning at > compile time. A new micro is introduced with a small sample of methods to > ensure the changes doesn't cause any perf regressions. > > For now, the changes include the update to the man page for the "java" > command. It might be that this has to be separated out so that it goes with > other updates in the release. Some of the deprecated methods are very likely to be run in hot loops (e.g. read/store operations). Unless we set `--sun-misc-unsafe-memory-access=allow`, what would be the performance impact on various platforms for these operations? ------------- PR Comment: https://git.openjdk.org/jdk/pull/19174#issuecomment-2107216975
