--- /dev/null	Tue Feb  2 22:57:38 2016
+++ new/test/stress/gc/TestMultiThreadStressRSet.java	Tue Feb  2 22:58:58 2016
@@ -0,0 +1,307 @@
+/*
+ * Copyright (c) 2016, 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.
+ */
+
+
+import java.io.PrintStream;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Random;
+import sun.hotspot.WhiteBox;
+
+/*
+ * @test TestMultiThreadStressRSet.java
+ * @key stress
+ * @requires vm.gc=="G1" | vm.gc=="null"
+ * @requires os.maxMemory > 2G
+ *
+ * @summary Stress G1 Remembered Set by in multiple threads
+ * @modules java.base/sun.misc
+ * @library /testlibrary /test/lib
+ * @build sun.hotspot.WhiteBox
+ * @run main ClassFileInstaller sun.hotspot.WhiteBox
+ *                              sun.hotspot.WhiteBox$WhiteBoxPermission
+ * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
+ *   -XX:+UseG1GC -XX:G1SummarizeRSetStatsPeriod=1 -XX:+G1SummarizeRSetStats
+ *   -XX:+IgnoreUnrecognizedVMOptions -XX:+PrintGC -XX:+PrintGCTimeStamps -Xlog:gc 
+ *   -Xmx500m -XX:G1HeapRegionSize=1m -XX:MaxGCPauseMillis=1000 TestMultiThreadStressRSet 10 4
+ *
+ * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
+ *   -XX:+UseG1GC -XX:G1SummarizeRSetStatsPeriod=100 -XX:+G1SummarizeRSetStats
+ *   -XX:+IgnoreUnrecognizedVMOptions -XX:+PrintGC -XX:+PrintGCTimeStamps -Xlog:gc 
+ *   -Xmx1G -XX:G1HeapRegionSize=8m -XX:MaxGCPauseMillis=1000 TestMultiThreadStressRSet 60 16
+ *
+ * @run main/othervm/timeout=700 -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
+ *   -XX:+UseG1GC -XX:G1SummarizeRSetStatsPeriod=100 -XX:+G1SummarizeRSetStats
+ *   -XX:+IgnoreUnrecognizedVMOptions -XX:+PrintGC -XX:+PrintGCTimeStamps -Xlog:gc 
+ *   -Xmx500m -XX:G1HeapRegionSize=1m -XX:MaxGCPauseMillis=1000 TestMultiThreadStressRSet 600 32
+ */
+public class TestMultiThreadStressRSet {
+
+    private static final Random RND = new Random(2015 * 2016);
+    private static final WhiteBox WB = WhiteBox.getWhiteBox();
+    private static final int REF_SIZE = WB.getHeapOopSize();
+    private static final int REGION_SIZE = WB.g1RegionSize();
+    
+    // How many regions to use for the storage
+    private static final int STORAGE_REGS = 20;
+    
+    // Size a single obj in the storage
+    private static final int OBJ_SIZE = 1024;
+
+    // How many regions of young/old gen to use in the BUFFER
+    private static final int BUFFER_YOUNG_REGS = 60;
+    private static final int BUFFER_OLD_REGS = 40;
+    
+    // Total number of objects in the storage.
+    private final int N;
+
+    // The storage of byte[]
+    private final List<Object> STORAGE;
+
+    // Where references to the Storage will be stored
+    private final List<Object[]> BUFFER;
+
+    // The lenght of a buffer element.
+    // RSet deals with "cards" (areas of 512 bytes), not with single refs
+    // So, to affect the RSet the BUFFER refs should be allocated in different
+    // memory cards.
+    private final int BUF_ARR_LEN = 100 * (512 / REF_SIZE);
+
+    // Total number of objects in the young/old buffers
+    private final int YOUNG;
+    private final int OLD;
+
+    // Frame of STORAGE - a subset of STORAGE, objects which will be
+    // refered. First element has got the index: 'frameStart', the last
+    // one 'frameStart + frameSize - 1'
+    private int frameStart;
+    private final int frameSize;
+
+    // Counter of created worker threads
+    private int counter = 0;
+
+    private volatile String errorMessage = null;
+    private volatile boolean isEnough = false;
+
+    public static void main(String args[]) {
+        if (args.length != 2) {
+            throw new IllegalArgumentException("TEST BUG: wrong arg count " + args.length);
+        }
+        long time = Long.parseLong(args[0]);
+        int threads = Integer.parseInt(args[1]);
+        new TestMultiThreadStressRSet().test(time * 1000, threads);
+    }
+
+    /**
+     * Initiates test parameters, fills out the STORAGE and BUFFER.
+     */
+    public TestMultiThreadStressRSet() {
+        
+        N = (REGION_SIZE - 1) * STORAGE_REGS / OBJ_SIZE + 1;
+        STORAGE = new ArrayList<>(N);
+        int bytes = OBJ_SIZE - 20;
+        for (int i = 0; i < N - 1; i++) {
+            STORAGE.add(new byte[bytes]);
+        }
+        STORAGE.add(new byte[REGION_SIZE / 2 + 100]); // humongous
+        frameStart = 0;
+        frameSize = REGION_SIZE / OBJ_SIZE;
+
+        BUFFER = new ArrayList<>();
+        int sizeOfBufferObject = 20 + REF_SIZE * BUF_ARR_LEN;
+        OLD = REGION_SIZE * BUFFER_OLD_REGS / sizeOfBufferObject;
+        YOUNG = REGION_SIZE * BUFFER_YOUNG_REGS / sizeOfBufferObject;
+        for (int i = 0; i < OLD + YOUNG; i++) {
+            BUFFER.add(new Object[BUF_ARR_LEN]);
+        }
+    }
+
+    /**
+     * Does the testing. Steps:
+     * <ul>
+     * <li> starts the Shifter thread
+     * <li> during the given time starts new Worker threads, keeping the number
+     * of living thread under limit.
+     * <li> stops the Shifter thread
+     * </ul>
+     *
+     * @param timeInMillis how long to stress
+     * @param maxThreads the maximum number of Worker thread working together.
+     */
+    public void test(long timeInMillis, int maxThreads) {
+        if (timeInMillis <= 0 || maxThreads <= 0) {
+            throw new IllegalArgumentException("TEST BUG: be positive!");
+        }
+        System.out.println("%% Time to work: " + timeInMillis / 1000 + "s");
+        System.out.println("%% Number of threads: " + maxThreads);
+        long finish = System.currentTimeMillis() + timeInMillis;
+        Shifter shift = new Shifter(this, 1000, (int) (frameSize * 0.9));
+        shift.start();
+        for (int i = 0; i < maxThreads; i++) {
+            new Worker(this, 100).start();
+        }
+        try {
+            while (System.currentTimeMillis() < finish && errorMessage == null) {
+                Thread.sleep(100);
+            }
+        } catch (Throwable t) {
+            printAllStackTraces(System.err);
+            t.printStackTrace(System.err);
+            this.errorMessage = t.getMessage();
+        } finally {
+            isEnough = true;
+        }
+        System.out.println("%% Total work cycles: " + counter);
+        if (errorMessage != null) {
+            throw new RuntimeException(errorMessage);
+        }
+    }
+
+    /**
+     * Returns an element from from the BUFFER (an object array) to keep
+     * references to the storage.
+     *
+     * @return an Object[] from buffer.
+     */
+    private Object[] getFromBuffer() {
+        int index = counter % (OLD + YOUNG);
+        synchronized (BUFFER) {
+            if (index < OLD) {
+                if (counter % 100 == (counter / 100) % 100) {
+                    // need a trash in the OldGen to provoke Mixed GC
+                    return replaceInBuffer(index);
+                } else {
+                    return BUFFER.get(index);
+                }
+            } else {
+                return replaceInBuffer(index);
+            }
+        }
+    }
+
+    private Object[] replaceInBuffer(int index) {
+        Object[] objs = new Object[BUF_ARR_LEN];
+        BUFFER.set(index, objs);
+        return objs;
+    }
+
+    /**
+     * Returns a random object from the current frame of the storage. A storage
+     * element with index from frameStart to frameStart+frameSize.
+     *
+     * @return a random element from the current frame of the storage.
+     */
+    private Object getRandomObject() {
+        int index = (frameStart + RND.nextInt(frameSize)) % N;
+        return STORAGE.get(index);
+    }
+
+    private static void printAllStackTraces(PrintStream ps) {
+        Map<Thread, StackTraceElement[]> traces = Thread.getAllStackTraces();
+        for (Thread t : traces.keySet()) {
+            ps.println(t.toString() + " " + t.getState());
+            for (StackTraceElement traceElement : traces.get(t)) {
+                ps.println("\tat " + traceElement);
+            }
+        }
+    }
+
+    /**
+     * Thread to create a number of references from BUFFER to STORAGE.
+     */
+    private static class Worker extends Thread {
+
+        final TestMultiThreadStressRSet boss;
+        final int refs; // number of refs to OldGen
+
+        /**
+         * @param boss the tests
+         * @param refsToOldGen how many references to the OldGen to create
+         */
+        Worker(TestMultiThreadStressRSet boss, int refsToOldGen) {
+            this.boss = boss;
+            this.refs = refsToOldGen;
+        }
+
+        @Override
+        public void run() {
+            try {
+                while (!boss.isEnough) {
+                    Object[] objs = boss.getFromBuffer();
+                    int step = objs.length / refs;
+                    for (int i = 0; i < refs; i += step) {
+                        objs[i] = boss.getRandomObject();
+                    }
+                    boss.counter++;
+                }
+            } catch (Throwable t) {
+                t.printStackTrace(System.out);
+                boss.errorMessage = t.getMessage();
+            }
+        }
+    }
+
+    /**
+     * The thread for periodical shifting of the current STORAGE frame and
+     * cleaning BUFFER from references to the objects outside of the new current
+     * frame.
+     */
+    private static class Shifter extends Thread {
+
+        final TestMultiThreadStressRSet boss;
+        final int sleepTime;
+        final int shift;
+
+        Shifter(TestMultiThreadStressRSet boss, int sleepTime, int shift) {
+            this.boss = boss;
+            this.sleepTime = sleepTime;
+            this.shift = shift;
+        }
+
+        @Override
+        public void run() {
+            try {
+                while (!boss.isEnough) {
+                    Thread.sleep(sleepTime);
+                    boss.frameStart += shift;
+                    for (int i = 0; i < boss.OLD; i++) {
+                        Object[] objs = boss.BUFFER.get(i);
+                        for (int j = 0; j < objs.length; j++) {
+                            objs[j] = null;
+                        }
+                    }
+                    if (!WB.g1InConcurrentMark()) {
+                        System.out.println("%% start CMC");
+                        WB.g1StartConcMarkCycle();
+                    } else {
+                        System.out.println("%% CMC is already in progress");
+                    }
+                }
+            } catch (Throwable t) {
+                t.printStackTrace(System.out);
+                boss.errorMessage = t.getMessage();
+            }
+        }
+    }
+}