GraalVM 20.1

Oleg Šelajev
Published in
5 min readMay 19, 2020


We’re really happy to announce that the 20.1.0 release of GraalVM is available and ready to make your applications run faster.

GraalVM 20.1 is a feature release from the master branch and includes a number of improvements across all the components of the distribution. We’re grateful for all the support from various teams and individual contributors for helping make this release of GraalVM the best it can be. Thanks for raising issues if something doesn’t work the way you expect, suggesting useful features, spreading the word about GraalVM, and contributing to the project on GitHub.

For a detailed list of features in the release please check out the release notes and individual changelog files for the components on GitHub; here are now the highlights of the release.

Faster runtime

One new feature is improved Kotlin coroutine support in the GraalVM compiler. In the past the GraalVM compiler didn’t know how to process irreducible loops in Java bytecode. This is a particularly rare pattern in the bytecode where you can jump in the middle of the loop code without visiting the loop entrance. This pattern doesn’t occur when you compile Java or Scala, Groovy or Clojure (and I’m sure other languages), but it might happen if you run a bytecode obfuscator or use Kotlin coroutines inside loops.

Not being able to process code like that meant that the compiler has to bail on compiling the whole unit if it encountered this pattern, relying on the interpreter to run the code there. The GraalVM compiler in 20.1 can process code like that and it both speeds it up considerably compared to previous versions and enables processing code like that in the native images!

If we look at some of the benchmarks from the kotlinx.coroutines project we can see significant improvements. Clone the project, run it with gradle — no-daemon cleanJmhJar jmh -Pjmh="scrabble", and see for yourself (the numbers are time per operation, so lower is better):

# GraalVM Enterprise 20.0
Benchmark Mode Cnt Score Error Units avgt 7 256.648 ± 3.574 ms/op avgt 7 114.249 ± 1.465 ms/op avgt 7 121.020 ± 3.820 ms/op avgt 7 35.641 ± 6.984 ms/op avgt 7 75.944 ± 8.367 ms/op avgt 7 16.180 ± 4.012 ms/op

# GraalVM Enterprise 20.1
Benchmark Mode Cnt Score Error Units avgt 7 85.204 ± 14.663 ms/op avgt 7 21.275 ± 6.202 ms/op avgt 7 121.277 ± 24.748 ms/op avgt 7 37.277 ± 8.069 ms/op avgt 7 16.945 ± 3.285 ms/op avgt 7 15.811 ± 4.544 ms/op

The benchmarks that don’t use coroutines in loops didn’t change much, but on the ones which do (e.g.,SaneFlowPlaysScrabble, FlowPlaysScrabbleBase, FlowPlaysScrabbleOpt) GraalVM 20.1 is about 4 times faster!

There are more improvements to the GraalVM compiler. One notable example is a major improvement on JDK 11 based GraalVM when fast locking is in use. GraalVM 20.1 improves its score on many benchmarks, sometimes as dramatically as making it almost 40% faster than before. For example, on the log-regression benchmark from the Renaissance benchmark suite:

JDK 11 based builds of GraalVM saw great improvements on a number of workloads

Better user experience for native image

The GraalVM native image utility got a lot of attention in this release. One of the most notable pieces of feedback we get about GraalVM native image is that the compilation times aren’t great. Indeed, the native image utility needs to analyze all the classes in your application and figure out which ones need to be included in the executable, which takes quite a bit of time and memory.

To address this issue in 20.1 we added a new mechanism, called “saturated type flows”, to make the analysis faster. It is not enabled by default yet, so you need to turn it on manually with the -H:+RemoveSaturatedTypeFlows command line option.

The build process with it enabled can be significantly faster. For example, if we look at compiling the Spring Petclinic example to a native image using spring-graalvm-native, the build process is now approximately 25% faster and uses 25% less memory than before.

Speaking of Spring, the work on being able to run Spring applications as GraalVM native images progresses nicely and there are a number of issues related to it which got fixed in 20.1. You can find them on GitHub.

Another excellent quality of life improvement for native images that landed in 20.1 is the ability to include signal handlers in the executable. You can now specify the --install-exit-handlers option and the application will register a default SIGTERM handler. This helps the most when you’re running native images as entrypoints in Docker, where the native image now won’t prevent Docker container being stopped with Ctrl + C like before.

Improvements in languages and tools

GraalVM’s JavaScript has now ECMAScript 2020 mode features enabled by default. Another interesting change with our JavaScript implementation in GraalVM 20.1 is that TRegex, the regular expression engine built as a GraalVM language, supports now all necessary regex features necessary for JavaScript engines.

Python was updated to 3.8.2 and includes a lot of performance improvements for the Python primitives — Lists, Dicts, tuples. Also NumPy should now work on MacOS now using the same ginstall setup as on Linux.

TruffleRuby now has nightly builds, a much faster bundle install, and better compatibility with C extensions thanks to using the same C type as CRuby for VALUE.

Our R implementation now includes GCC runtime libraries on both Linux and MacOS. And it also removes GFortran as the requirement for running, which simplifies installation of CRAN packages a lot.

Tools in GraalVM saw a lot of improvements too. The stability of Language Server and the VSCode extensions for GraalVM has improved. In addition to JavaScript, Ruby and R now support Language Server Protocol too.

VisualVM now has the ability to show memory consumption by libgraal, which can help discover issues with misconfiguring it.

You can monitor memory used by `libgraal` in VisualVM.


GraalVM 20.1 is a major feature release with a number of improvements across all the components. It significantly improves the performance of numerous Java workloads, idiomatic Kotlin, and Python; simplifies the installation of R packages; and enables JavaScript 2020 features by default. There are many other other bugfixes, performance and stability improvements, and other features that are too numerous to mention here but are no less important!

Please read a more detailed outline of the new and noteworthy features in the release notes and consider looking at the changelog for the project components on GitHub!

Download GraalVM 20.1, use it for running your applications, and build new exciting projects. If you have any feedback please don’t hesitate to let us know on Twitter, Slack or GitHub!

— GraalVM team