hotspot/test/gc/arguments/TestSelectDefaultGC.java

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/*
 * @test TestSelectDefaultGC
 * @summary Test selection of GC when no GC option is specified
 * @bug 8068582
 * @key gc
 * @library /testlibrary
 * @modules java.base/jdk.internal.misc
 *          java.management
 * @ignore 8148239
 * @run driver TestSelectDefaultGC
 */

import jdk.test.lib.*;
import java.util.regex.*;

public class TestSelectDefaultGC {
    public static void assertVMOption(OutputAnalyzer output, String option, boolean value) {
        output.shouldMatch(" " + option + " .*=.* " + value + " ");
    }

    public static void main(String[] args) throws Exception {
        // Start VM without specifying GC
        ProcessBuilder pb = ProcessTools.createJavaProcessBuilder("-XX:+PrintFlagsFinal", "-version");
        OutputAnalyzer output = new OutputAnalyzer(pb.start());
        output.shouldHaveExitValue(0);

        boolean isServerVM = Platform.isServer();
        boolean isEmbeddedVM = Platform.isEmbedded();

        // Verify GC selection
        // G1 is default for non-embedded server VMs
        assertVMOption(output, "UseG1GC",            isServerVM && !isEmbeddedVM);
        // Parallel is default for embedded server VMs
        assertVMOption(output, "UseParallelGC",      isServerVM && isEmbeddedVM);
        assertVMOption(output, "UseParallelOldGC",   isServerVM && isEmbeddedVM);
        // Serial is default for non-server VMs
        assertVMOption(output, "UseSerialGC",        !isServerVM);
        assertVMOption(output, "UseConcMarkSweepGC", false);
        assertVMOption(output, "UseParNewGC",        false);
    }
}