jdk-24/hotspot/test/gc/arguments/TestParallelGCThreads.java

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/*
 * @test TestParallelGCThreads
 * @key gc
 * @bug 8059527
 * @summary Tests argument processing for ParallelGCThreads
 * @library /testlibrary
 * @modules java.base/sun.misc
 *          java.management
 * @run driver TestParallelGCThreads
 */

import jdk.test.lib.*;

public class TestParallelGCThreads {

  public static void main(String args[]) throws Exception {

    // For each parallel collector (G1, Parallel, ParNew/CMS)
    for (String gc : new String[] {"G1", "Parallel", "ConcMarkSweep"}) {

      // Make sure the VM does not allow ParallelGCThreads set to 0
      String[] flags = new String[] {"-XX:+Use" + gc + "GC", "-XX:ParallelGCThreads=0", "-XX:+PrintFlagsFinal", "-version"};
      ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(flags);
      OutputAnalyzer output = new OutputAnalyzer(pb.start());
      output.shouldHaveExitValue(1);

      // Do some basic testing to ensure the flag updates the count
      for (long i = 1; i <= 3; i++) {
        flags = new String[] {"-XX:+Use" + gc + "GC", "-XX:ParallelGCThreads=" + i, "-XX:+PrintFlagsFinal", "-version"};
        long count = getParallelGCThreadCount(flags);
        Asserts.assertEQ(count, i, "Specifying ParallelGCThreads=" + i + " for " + gc + "GC does not set the thread count properly!");
      }
    }
  }

  public static long getParallelGCThreadCount(String flags[]) throws Exception {
    ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(flags);
    OutputAnalyzer output = new OutputAnalyzer(pb.start());
    output.shouldHaveExitValue(0);
    String stdout = output.getStdout();
    return FlagsValue.getFlagLongValue("ParallelGCThreads", stdout);
  }
}