8037924: CMM Testing: Check Min/MaxHeapFreeRatio flags allows to shrink the heap when using ParallelGC

New test implemented

Reviewed-by: ehelin, tschatzl

hotspot/test/TEST.groups

@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.
 # DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 #
 # This code is free software; you can redistribute it and/or modify it
@@ -131,6 +131,7 @@ needs_compact3 = \
   gc/metaspace/TestMetaspaceMemoryPool.java \
   gc/arguments/TestDynMinHeapFreeRatio.java \
   gc/arguments/TestDynMaxHeapFreeRatio.java \
+  gc/parallelScavenge/TestDynShrinkHeap.java \
   runtime/InternalApi/ThreadCpuTimesDeadlock.java \
   serviceability/threads/TestFalseDeadLock.java \
   compiler/tiered/NonTieredLevelsTest.java \

hotspot/test/gc/parallelScavenge/TestDynShrinkHeap.java

@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test TestDynShrinkHeap
+ * @bug 8016479
+ * @summary Verify that the heap shrinks after full GC according to the current values of the Min/MaxHeapFreeRatio flags
+ * @library /testlibrary
+ * @run main/othervm -XX:+UseAdaptiveSizePolicyWithSystemGC -XX:+UseParallelGC -XX:MinHeapFreeRatio=0 -XX:MaxHeapFreeRatio=100 -verbose:gc TestDynShrinkHeap
+ */
+
+import com.oracle.java.testlibrary.TestDynamicVMOption;
+import java.lang.management.ManagementFactory;
+import java.lang.management.MemoryUsage;
+import java.util.ArrayList;
+import sun.management.ManagementFactoryHelper;
+import static com.oracle.java.testlibrary.Asserts.*;
+
+public class TestDynShrinkHeap {
+
+    public static final String MIN_FREE_RATIO_FLAG_NAME = "MinHeapFreeRatio";
+    public static final String MAX_FREE_RATIO_FLAG_NAME = "MaxHeapFreeRatio";
+
+    private static ArrayList<byte[]> list = new ArrayList<>(0);
+    private static final int M = 1024 * 1024; // to make heap more manageable by test code
+
+    private final TestDynamicVMOption maxRatioOption;
+    private final TestDynamicVMOption minRatioOption;
+
+    public TestDynShrinkHeap() {
+        minRatioOption = new TestDynamicVMOption(MIN_FREE_RATIO_FLAG_NAME);
+        maxRatioOption = new TestDynamicVMOption(MAX_FREE_RATIO_FLAG_NAME);
+    }
+
+    private final void test() {
+        System.gc();
+        MemoryUsagePrinter.printMemoryUsage("init");
+
+        eat();
+        MemoryUsagePrinter.printMemoryUsage("eaten");
+        MemoryUsage muFull = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();
+
+        free();
+        MemoryUsagePrinter.printMemoryUsage("free");
+        MemoryUsage muFree = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();
+
+        assertLessThan(muFree.getCommitted(), muFull.getCommitted(), String.format(
+                "committed free heap size is not less than committed full heap size, heap hasn't been shrunk?%n"
+                + "%s = %s%n%s = %s",
+                MIN_FREE_RATIO_FLAG_NAME,
+                ManagementFactoryHelper.getDiagnosticMXBean().getVMOption(MIN_FREE_RATIO_FLAG_NAME).getValue(),
+                MAX_FREE_RATIO_FLAG_NAME,
+                ManagementFactoryHelper.getDiagnosticMXBean().getVMOption(MAX_FREE_RATIO_FLAG_NAME).getValue()
+        ));
+    }
+
+    private void eat() {
+        for (int i = 0; i < M; i++) {
+            list.add(new byte[1024]);
+        }
+        MemoryUsagePrinter.printMemoryUsage("allocated " + M + " arrays");
+
+        list.subList(0, M / 2).clear();
+        System.gc();
+        MemoryUsagePrinter.printMemoryUsage("array halved");
+    }
+
+    private void free() {
+        maxRatioOption.setIntValue(minRatioOption.getIntValue() + 1);
+        System.gc();
+        MemoryUsagePrinter.printMemoryUsage("under pressure");
+    }
+
+    public static void main(String[] args) {
+        new TestDynShrinkHeap().test();
+    }
+}
+
+/**
+ * Prints memory usage to standard output
+ */
+class MemoryUsagePrinter {
+
+    public static String humanReadableByteCount(long bytes, boolean si) {
+        int unit = si ? 1000 : 1024;
+        if (bytes < unit) {
+            return bytes + " B";
+        }
+        int exp = (int) (Math.log(bytes) / Math.log(unit));
+        String pre = (si ? "kMGTPE" : "KMGTPE").charAt(exp - 1) + (si ? "" : "i");
+        return String.format("%.1f %sB", bytes / Math.pow(unit, exp), pre);
+    }
+
+    public static void printMemoryUsage(String label) {
+        MemoryUsage memusage = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();
+        float freeratio = 1f - (float) memusage.getUsed() / memusage.getCommitted();
+        System.out.format("[%-24s] init: %-7s, used: %-7s, comm: %-7s, freeRatio ~= %.1f%%%n",
+                label,
+                humanReadableByteCount(memusage.getInit(), true),
+                humanReadableByteCount(memusage.getUsed(), true),
+                humanReadableByteCount(memusage.getCommitted(), true),
+                freeratio * 100
+        );
+    }
+}