about memory release

[codingmiao]

I have written the following demo, which increases memory usage continuously during runtime until it encounters a memory overflow. Could you please confirm if this demo has a memory leak issue and suggest how to fix it?

import org.codehaus.commons.compiler.CompilerFactoryFactory;
import org.codehaus.commons.compiler.IClassBodyEvaluator;

import java.io.StringReader;

public class T2 {
    @FunctionalInterface
    public interface F {
        long test();
    }
    public static class CustomClassLoader extends ClassLoader {
    }

    public static void main(String[] args) throws Exception {
        for (long l = 0; l < 100000000L; l++) {
            String code = "public long test(){return " + l + ";}";
            IClassBodyEvaluator cbe = CompilerFactoryFactory.getDefaultCompilerFactory(new CustomClassLoader()).newClassBodyEvaluator();
            cbe.setImplementedInterfaces(new Class[]{F.class});
            F f = (F) cbe.createInstance(new StringReader(code));
            System.out.println(f.test());
        }
    }

}

Among them, this section of code, String code = "public long test(){return " + l + ";}";, is just a demonstration. In reality, it is dynamically passed by the user in a web service. Therefore, caching is not very meaningful. Even if I implement caching, it seems that some classes and objects generated by ClassBodyEvaluator will not be garbage collected. Over time, this will eventually result in a memory overflow.

[aunkrig]

Hey there,

AFAIK Janino has no memory leaks that would cause an OutOfMemoryError, however, some JVMs are notoriously bad when it comes to garbage-collecting classes and class loaders, which probably is what you observe here.

I ran your code example with an adopt_openjdk-11.0.11-9-hotspot on Windows 10, 21H2, and the memory usage stabilizes at 750...800 MB with the JVM default settings, and Janino happily cooks ClassBodyEvaluators at approx. 5000/sec.

What OS and JVM are you using? Could you please try some combinations of OS and/or JVM?

CU Arno

[codingmiao]

I tried switching from JDK 17 to JDK 11 and adjusted the -XX:MaxMetaspaceSize parameter. It seems that the memory usage has improved. I will continue to observe for a while. Thank you.