GraalVM logs to the console

[kaikreuzer]

With openHAB 5.0.0.M4, I see the following being logged to the console where I'm starting openHAB:

[To redirect Truffle log output to a file use one of the following options:
* '--log.file=<path>' if the option is passed using a guest language launcher.
* '-Dpolyglot.log.file=<path>' if the option is passed using the host Java launcher.
* Configure logging using the polyglot embedding API.]
[engine] WARNING: The polyglot engine uses a fallback runtime that does not support runtime compilation to native code.
Execution without runtime compilation will negatively impact the guest application performance.
The following cause was found: JVMCI is required to enable optimizations. Pass -XX:+EnableJVMCI as a virtual machine argument to the java executable to resolve this.
For more information see: https://www.graalvm.org/latest/reference-manual/embed-languages/#runtime-optimization-support.
To disable this warning use the '--engine.WarnInterpreterOnly=false' option or the '-Dpolyglot.engine.WarnInterpreterOnly=false' system property.

Looks to me as if this is coming from GraalVM - is there anyway to suppress this? //cc @digitaldan

[digitaldan]

@florian-h05 anything you think we can do here? I guess the simple solution would be to add -Dpolyglot.engine.WarnInterpreterOnly=false to the start up script?

[holgerfriedrich]

We seem to have two issues here; one warning regarding log and one regarding JIT performance.

Did we miss something here? Do we need to add -XX:+EnableJVMCI to our start scripts for better performance, or is this something we will evaluate and maybe roll out later?

@ccutrer @florian-h05 @HolgerHees

[ccutrer]

In an ideal world, yes I think we should EnableJVMCI by default. But I'm hesitant to do so since I know all the extra options Graal depends on/recommends are relatively new, and not necessarily supported by all JVMs. I've been using EnableJVMCI for a few months in my production instance with no issues, running openjdk 21.0.7:

openjdk 21.0.7 2025-04-15
OpenJDK Runtime Environment (build 21.0.7+6-Ubuntu-0ubuntu124.04)
OpenJDK 64-Bit Server VM (build 21.0.7+6-Ubuntu-0ubuntu124.04, mixed mode, sharing)

I we can get confirmation that it works with Temurin and Azul Zulu as well, then I say we enable it.

As for the warning about redirecting Truffle log output, I'll look into it today.

[florian-h05]

Seems that this is caused by MQTT HA, with JS Scripting and Python Scripting installed only I don't get this warning.
But good that this has been brought up - checking https://www.graalvm.org/latest/reference-manual/embed-languages/#runtime-optimization-support.

I hence agree with @ccutrer to enable JVMCI, but only after 5.0 to take no risk. But I think we then also need the compiler.jar in place.

[holgerfriedrich]

Thanks for the quick feedback, @ccutrer and @florian-h05.
Then I would prefer to keeping the part of the warning referring to -XX:+EnableJVMCI in the log.

[HolgerHees]

I disable this warning by setting the mentioned property in my binding.

Before I tried to enable it without any success. I got the message that no truffle runtime is available. I'm using the jdk provided by openhab docker container.

[florian-h05]

@ccutrer Were you able to get it working properly? When enabling JVMCI for me, I get:

[engine] WARNING: The polyglot engine uses a fallback runtime that does not support runtime compilation to native code.
Execution without runtime compilation will negatively impact the guest application performance.
The following cause was found: No optimizing Truffle runtime found on the module or class-path.
For more information see: https://www.graalvm.org/latest/reference-manual/embed-languages/#runtime-optimization-support.
To disable this warning use the '--engine.WarnInterpreterOnly=false' option or the '-Dpolyglot.engine.WarnInterpreterOnly=false' system property.

[ccutrer]

I thought it was working, cause warnings went away. I have -XX:+UnlockExperimentalVMOptions -XX:+EnableJVMCI in my /etc/default/openhab EXTRA_JAVA_OPTS. But maybe it's not, and the log message is just going somewhere I'm not seeing it?

Okay, I see now that I'm getting

The polyglot engine uses a fallback runtime that does not support runtime compilation to native code.
Execution without runtime compilation will negatively impact the guest application performance.
The following cause was found: Libgraal compilation is not available on this JVM. Alternatively, the org.graalvm.compiler:compiler module can be put on the --upgrade-module-path.
For more information see: https://www.graalvm.org/latest/reference-manual/embed-languages/#runtime-optimization-support.
To disable this warning use the '--engine.WarnInterpreterOnly=false' option or the '-Dpolyglot.engine.WarnInterpreterOnly=false' system property.

Slightly different warning. But the gist is basically "please use the GraalVM JVM".

[HolgerHees]

@holgerfriedrich if you want to keep the warning, I can remove my property setting.

[holgerfriedrich]

This is not a strong opinion. You are the experts for graalvm, I leave it up to you.
We may need some more optimizations in 5.1.

[ccutrer]

Given we don't yet want to enable JVMCI by default, I think we should silence the warnings. I'll do that for the Home Assistant addon.

[florian-h05]

Slightly different warning. But the gist is basically "please use the GraalVM JVM".

Or bring in the Graal compiler … which would require us to ship at least the compiler JAR.

[ccutrer]

Or bring in the Graal compiler … which would require us to ship at least the compiler JAR.

I have a feeling that that would cause another fun trip of incompatibilities between OSGi and Java Modules. I'm tapped out of that nightmare for a few months ;).