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As usual just before each Java release, I'm listing all the new performance features in the upcoming release of Java 17 (I have done this every 6 months prior to each new release, you can track back to the previous February and August newsletters if you want to see what's new performance-wise in any release). As usual I give the new features, the performance benefits from each feature, and how to use the feature.

Java 17 has a bunch of performance changes, but nothing really major. This is expected, because Java 17 is a Long Term Support (LTS) release, and no one wants to make a significant change in that release because if it's wrong, you have to support it for a long time. Instead all the significant changes are in the Java 12-16 releases, where they've had time to be well tested before Java 17.

Now on to the details of those Java 17 changes, including the options you have available to use them. And of course the tips from this month's articles, as ever are extracted into this month's tips page.

A note from this newsletter's sponsor

News

Java performance tuning related news - Java 17 generally useful performance features

• Unified Logging supports asynchronous log flushing with -Xlog:async, with a bounded buffer (-XX:AsyncLogBufferSize=BYTES) - messages are dropped if the buffer isn't flushed fast enough (ie IO rate compared to logging rate is too slow at any time)
• JEP411 Deprecate the Security Manager for Removal Not specifically performance related, but I know the performance community hae used the Security Manager to track some performance features, notably IO, so it's useful to know this is going
• JEP410 Removal of experimental features AOT jaotc and Graal JIT Removed because it's used very little but has support cost
• JEP415 Context-Specific Deserialization Filters Useful for defending against too large deserialized objects

Java performance tuning related news - Java 17 niche but useful performance features

• JEP412 Foreign Function & Memory API (Incubator) Still in incubation after many iterations. Useful for off heap management
• JEP414 Vector API (Incubator) Vector computations that reliably compile at runtime to optimal vector hardware instructions. If you use these types of operations - eg ML, image processing, scientific processing, massive financial calculations, etc - then you should check it out and feedback since this matters to you
• JEP382 Faster rendering on MacOS with -Dsun.java2d.metal=true
• FileSystemView.getSystemIcon() added to allow access to higher quality icons which should provide more optimal scaling
• Modernization of Ideal Graph Visualizer - a tool to explore visually and interactively the intermediate representation used in the HotSpot VM C2 just-in-time (JIT) compiler
• For those of you using JVMTI, some old heap analysis functions have been deprecated, you should move to the modern versions of these functions
• A new implementation of the Selector API on Windows - if you have issues it can be reverted for now with -Djava.nio.channels.spi.SelectorProvider=sun.nio.ch.WindowsSelectorProvider on the command line
• Stricter enforcement of an Agent's premain method to the java.lang.instrument specification
• Parallel GC now ergonomically determines the optimal number of threads to use for processing java.lang.ref.Reference instances during garbage collection The option -XX:ParallelRefProcEnabled is now true (enabled) by default. You can revert to the previous behavior by specifying -XX:-ParallelRefProcEnabled on the command line. The ergonomics of java.lang.ref.Reference processing can be tuned by using the experimental option -XX:ReferencesPerThread (default value: 1000)

Articles

• Filter Incoming Serialization Data (Roger Riggs/OpenJDK)
• Unified Logging Supports Asynchronous Log Flushing (David Holmes/OpenJDK)
• Context-Specific Deserialization Filters (Roger Riggs/OpenJDK)

Jack Shirazi

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