corretto
8357959: (bf) ByteBuffer.allocateDirect initialization can result in large TTSP spikes
ByteBuffer.allocateDirect initialization can result in large TTSP spikes
This backport adapts the JDK 26 improvement for ByteBuffer.allocateDirect initialization to reduce TTSP spikes. Minor conflict in template resolved manually to preserve 2023 copyright.
Description
This is a backport of a change made in https://github.com/openjdk/jdk/pull/25487
This is a performance change that prevents large safe point pauses during ByteBuffer.allocateDirect.
Related issues
Backport of https://github.com/openjdk/jdk/pull/25487
Motivation and context
This change has been added to JDK26 for a few months, and back ported to JDK25. This is a large performance gain, which would be nice to have in the 21 jdk.
How has this been tested?
This has been tested via unit test, and a reproducer run shows the performance gains from ~1s to < 1ms
https://gist.github.com/rk-kmr/be4322b72a14ae04aeefc0260c01acf6
Platform information
None
Additional context
This seems to be missing the key change in src/java.base/share/classes/java/nio/Direct-X-Buffer.java.template to actually use the new code, so I think if you run the reproducer you will not see any improvement.
Be aware that Corretto commit metadata should follow the OpenJDK one. Current commit would get committed with Backport e5ce5c57c83972ff52758a804c942986cab74ca7 from JDK 26 as synopsis, carried from the commit messages in your branch. It should really be: 8357959: (bf) ByteBuffer.allocateDirect initialization can result in large TTSP spikes.
