jdk-24/test/hotspot/jtreg/gc/stress/TestReclaimStringsLeaksMemory.java

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 * version 2 for more details (a copy is included in the LICENSE file that
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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/*
 * @test TestReclaimStringsLeaksMemory
 * @bug 8180048
 * @summary Ensure that during a Full GC interned string memory is reclaimed completely.
 * @requires vm.gc=="null" & !vm.graal.enabled & !vm.debug
 * @key gc
 * @library /test/lib
 * @modules java.base/jdk.internal.misc
 * @run main/othervm TestReclaimStringsLeaksMemory
 * @run main/othervm TestReclaimStringsLeaksMemory -XX:+UseSerialGC
 * @run main/othervm TestReclaimStringsLeaksMemory -XX:+UseParallelGC
 * @run main/othervm TestReclaimStringsLeaksMemory -XX:+UseParallelGC -XX:-UseParallelOldGC
 * @run main/othervm TestReclaimStringsLeaksMemory -XX:+UseConcMarkSweepGC
 * @run main/othervm TestReclaimStringsLeaksMemory -XX:+UseG1GC
 */

import java.util.Arrays;
import java.util.ArrayList;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

import jdk.test.lib.Asserts;
import jdk.test.lib.process.OutputAnalyzer;
import jdk.test.lib.process.ProcessTools;

public class TestReclaimStringsLeaksMemory {

    // The amount of memory in kB reserved in the "Symbol" category that indicates a memory leak for
    // this test.
    public static final int ReservedThreshold = 70000;

    public static void main(String[] args) throws Exception {
        ArrayList<String> baseargs = new ArrayList(Arrays.asList( "-Xms256M",
                                                                  "-Xmx256M",
                                                                  "-Xlog:gc*",
                                                                  "-XX:NativeMemoryTracking=summary",
                                                                  "-XX:+UnlockDiagnosticVMOptions",
                                                                  "-XX:+PrintNMTStatistics" ));
        baseargs.addAll(Arrays.asList(args));
        baseargs.add(GCTest.class.getName());
        ProcessBuilder pb_default =
            ProcessTools.createJavaProcessBuilder(baseargs.toArray(new String[] {}));
        verifySymbolMemoryUsageNotTooHigh(new OutputAnalyzer(pb_default.start()));
    }

    private static void verifySymbolMemoryUsageNotTooHigh(OutputAnalyzer output) throws Exception {
        String stdout = output.getStdout();
        System.out.println(stdout);

        Pattern p = Pattern.compile("Symbol \\(reserved=(\\d*)");
        Matcher m = p.matcher(stdout);

        if (!m.find()) {
            throw new RuntimeException("Could not find Symbol memory usage in NMT output");
        }

        int reserved = Integer.parseInt(m.group(1));
        Asserts.assertLT(reserved, ReservedThreshold, "Reserved memory size is " + reserved + "KB which is greater than or equal to " + ReservedThreshold + "KB indicating a memory leak");

        output.shouldHaveExitValue(0);
    }

    static class GCTest {
        public static final String BaseName = "SomeRandomBaseString";
        public static volatile String lastString;

        public static void main(String [] args) {
            for (int iterations = 0; iterations < 20;) {
                for (int i = 0; i < 1000000; i++) {
                    lastString = (BaseName + i).intern();
                }
                if (++iterations % 5 == 0) {
                   System.gc();
                }
            }
        }
    }
}