asmhatreandClaude Sonnet 5
2f88734f5d
MaxRAMPercentage vs a hardcoded -Xmx, -XX:-UseContainerSupport, the ActiveProcessorCount lie, and which diagnostic flags are worth leaving on in prod, verified in real Docker containers on JDK 25 and JDK 27. Co-Authored-By: Claude Sonnet 5 <[email protected]>
27 lines
1.1 KiB
Java
27 lines
1.1 KiB
Java
import java.util.ArrayList;
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import java.util.List;
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/**
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* Allocates a large number of a trivial fixed-shape object and a trivial
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* array, then sleeps so `jcmd <pid> GC.class_histogram` can be run against
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* it from outside the container. Used to measure the per-instance byte cost
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* that -XX:+/-UseCompactObjectHeaders actually makes, rather than quoting
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* the JEP's own number. See
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* https://ankurm.com/jvm-flags-for-spring-boot-in-containers-jdk-25-27/
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*/
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public class HeaderSizeDemo {
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static final class Pair { int a; int b; Pair(int a, int b) { this.a = a; this.b = b; } }
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public static void main(String[] args) throws Exception {
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int count = args.length > 0 ? Integer.parseInt(args[0]) : 2_000_000;
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List<Pair> pairs = new ArrayList<>(count);
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for (int i = 0; i < count; i++) {
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pairs.add(new Pair(i, i));
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}
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System.out.println("allocated " + pairs.size() + " Pair instances, pid=" + ProcessHandle.current().pid());
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System.gc();
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Thread.sleep(120_000);
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System.out.println(pairs.size());
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}
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}
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