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

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/*
 * @test TestParallelGCThreads
 * @key gc
 * @bug 8059527 8081382
 * @summary Tests argument processing for ParallelGCThreads
 * @library /testlibrary
 * @modules java.base/jdk.internal.misc
 *          java.management
 * @run driver TestParallelGCThreads
 */

import jdk.test.lib.*;

public class TestParallelGCThreads {

  public static void main(String args[]) throws Exception {
    testFlags();
    testDefaultValue();
  }

  private static final String flagName = "ParallelGCThreads";

  // uint ParallelGCThreads = 23 {product}
  private static final String printFlagsFinalPattern = " *uint *" + flagName + " *:?= *(\\d+) *\\{product\\} *";

  public static void testDefaultValue()  throws Exception {
    ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(
      "-XX:+UnlockExperimentalVMOptions", "-XX:+PrintFlagsFinal", "-version");

    OutputAnalyzer output = new OutputAnalyzer(pb.start());
    String value = output.firstMatch(printFlagsFinalPattern, 1);

    try {
      Asserts.assertNotNull(value, "Couldn't find uint flag " + flagName);

      Long longValue = new Long(value);

      // Sanity check that we got a non-zero value.
      Asserts.assertNotEquals(longValue, "0");

      output.shouldHaveExitValue(0);
    } catch (Exception e) {
      System.err.println(output.getOutput());
      throw e;
    }
  }

  public static void testFlags() 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!");
      }
    }

    // 4294967295 == (unsigned int) -1
    // So setting ParallelGCThreads=4294967295 should give back 4294967295
    // and setting ParallelGCThreads=4294967296 should give back 0. (SerialGC is ok with ParallelGCThreads=0)
    for (long i = 4294967295L; i <= 4294967296L; i++) {
      String[] flags = new String[] {"-XX:+UseSerialGC", "-XX:ParallelGCThreads=" + i, "-XX:+PrintFlagsFinal", "-version"};
      long count = getParallelGCThreadCount(flags);
      Asserts.assertEQ(count, i % 4294967296L, "Specifying ParallelGCThreads=" + i + " 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);
  }
}