[manoelcampos]

Measures the memory used by each VM and Host, to compare CloudSim Plus 8.5.1 (before cloudsimplus/cloudsimplus#586, where listener lists start as the shared List.of()) with the current version. Related to Optimization 3.1 of cloudsimplus/cloudsimplus#523.

Changes

• ListenersMemoryBenchmark: a plain main (not JMH, since we need the memory kept in the heap, not time or allocation rate). It creates 100,000 VMs and then 100,000 Hosts, measures the used heap after a GC before and after creating them, and prints the bytes kept by each object (median of 5 rounds). It must run with -XX:+UseSerialGC, so System.gc() does a full collection.
• pom.xml:
  • The CloudSim Plus dependency uses the new cloudsimplus.version property (default: ${project.version}).
  • The new cloudsimplus-8 profile sets it to 8.5.1. It excludes ListenersNotificationBenchmark, which uses the Listeners class from CloudSim Plus 9 (to be fixed by ListenersNotificationBenchmark shouldn't depend on the Listeners class from CloudSim Plus 9 #8).
  • The pinned logback-classic 1.4.5 was removed. It was mixed with logback-core 1.5.34 from CloudSim Plus 9, failing when a VM was created. Each CloudSim Plus version brings its matching logback.
• CLAUDE.md: documents the new benchmark.

How to run

./mvnw clean package -Pcloudsimplus-8
java -XX:+UseSerialGC -cp target/cloudsimplus-benchmarks-*-uber.jar org.cloudsimplus.listeners.ListenersMemoryBenchmark 8.5.1

./mvnw clean package
java -XX:+UseSerialGC -cp target/cloudsimplus-benchmarks-*-uber.jar org.cloudsimplus.listeners.ListenersMemoryBenchmark current

Results

Class	8.5.1	Current (9.0.0-SNAPSHOT)	Difference
VmSimple	1144 B	880 B	−264 B
HostSimple	880 B	912 B	+32 B

These results include all changes since 8.5.1, not only #586.
Running the benchmark with CloudSim Plus built at the #586 commit and at its parent showed that #586 alone saves:

• VM: 144 B (6 empty ArrayLists × 24 B);
• Host: 112 B (1 empty HashSet with its HashMap, 64 B, + 2 empty ArrayLists, 48 B).

So other changes since 8.5.1 made Hosts about 144 B bigger.

Run with JDK 25.0.4 (Corretto), compressed oops.

🤖 Generated with Claude Code