/*

 * 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

 * @requires os.maxMemory > 2G

 * @requires vm.opt.MaxGCPauseMillis == "null"

 *

 * @summary Stress G1 Remembered Set using multiple threads

 * @modules java.base/jdk.internal.misc

 * @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 -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 -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 -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_REGIONS = 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_REGIONS = 60;

    private static final int BUFFER_OLD_REGIONS = 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 length 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;

    // To cause Remembered Sets change their coarse level the test uses a window

    // within STORAGE. All the BUFFER elements refer to only STORAGE objects

    // from the current window. The window is defined by a range.

    // The first element has got the index: 'windowStart',

    // the last one: 'windowStart + windowSize - 1'

    // The window is shifting periodically.

    private int windowStart;

    private final int windowSize;

    // 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_REGIONS / 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

        windowStart = 0;

        windowSize = REGION_SIZE / OBJ_SIZE;

        BUFFER = new ArrayList<>();

        int sizeOfBufferObject = 20 + REF_SIZE * BUF_ARR_LEN;

        OLD = REGION_SIZE * BUFFER_OLD_REGIONS / sizeOfBufferObject;

        YOUNG = REGION_SIZE * BUFFER_YOUNG_REGIONS / 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 live 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) (windowSize * 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 to generate garbage in the old gen 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 window within the storage.

     * A storage element with index from windowStart to windowStart+windowSize.

     *

     * @return a random element from the current window within the storage.

     */

    private Object getRandomObject() {

        int index = (windowStart + RND.nextInt(windowSize)) % 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();

            }

        }

    }

    /**

     * Periodically shifts the current STORAGE window, removing references

     * in BUFFER that refer to objects outside the window.

     */

    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.windowStart += 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();

            }

        }

    }

}