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 * 2 along with this work; if not, write to the Free Software Foundation,

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/*

 * @test TestGreyReclaimedHumongousObjects.java

 * @bug 8069367

 * @requires vm.gc == "G1" | vm.gc == "null"

 * @summary Test handling of marked but unscanned reclaimed humongous objects.

 * @key gc

 * @run main/othervm -XX:+UseG1GC -Xss32m -Xmx128m -XX:G1HeapRegionSize=1m

 *      -XX:+UnlockExperimentalVMOptions

 *          -XX:+G1EagerReclaimHumongousObjects

 *          -XX:+G1EagerReclaimHumongousObjectsWithStaleRefs

 *      TestGreyReclaimedHumongousObjects 1048576 90

 */

// This test spawns a bunch of threads, each of them rapidly

// allocating large objects and storing them into a circular buffer

// associated with the thread.  The circular buffer results in these

// objects becoming dead in fairly short order.

//

// The situation we're trying to provoke is

//

// (1) A humongous object H is marked and added to the mark stack.

//

// (2) An evacuation pause determines H is no longer live, and

// reclaims it.  This occurs before concurrent marking has gotten

// around to processing the mark stack entry for H.

//

// (3) Concurrent marking processes the mark stack entry for H.  The

// bug is that it would attempt to scan the now dead object.

//

// Unfortunately, this test is *very* sensitive to configuration.

// Among the parameters that affect whether / how often we'll get into

// the desired situation within a reasonable amount of time are:

//

// - THREAD_COUNT: The number of allocating threads.

//

// - OLD_COUNT: The number of objects each thread keeps.

//

// - MAX_MEMORY: The maximum heap size.

//

// - G1HeapRegionSize

//

// - The size of the objects being allocated.

//

// The parameter values specified here:

//

// - THREAD_COUNT = 12

// - OLD_COUNT == 4

// - MAX_MEMORY == 128m

// - G1HeapRegionSize = 1m

// - Object size = 1048576 (2 regions after header overhead and roundup)

//

// seems to work well at provoking the desired state fairly quickly.

// Even relatively small perturbations may change that.  The key

// factors seem to be keeping the heap mostly full of live objects but

// having them become dead fairly quickly.

import java.util.Date;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.ThreadFactory;

import java.util.concurrent.TimeUnit;

import com.sun.management.HotSpotDiagnosticMXBean;

import java.lang.management.ManagementFactory;

public class TestGreyReclaimedHumongousObjects {

    static class NamedThreadFactory implements ThreadFactory {

       private int threadNum = 0;

       @Override

       public Thread newThread(Runnable r) {

         return new Thread(r, THREAD_NAME + (threadNum++));

       }

    }

    static class Runner extends Thread {

        private final Date startDate = new Date();

        private final int obj_size;

        private final Object[] old_garbage;

        private int old_index = 0;

        public Runner(int obj_size) {

            this.obj_size = obj_size;

            old_garbage = new Object[OLD_COUNT];

        }

        private void allocate_garbage() {

            byte[] garbage = new byte[obj_size];

            old_garbage[Math.abs(++old_index % OLD_COUNT)] = garbage;

        }

        @Override

        public void run() {

            try {

                while (!isInterrupted()) {

                    allocate_garbage();

                    Thread.sleep(0); // Yield, to ensure interruptable.

                }

            } catch (InterruptedException e) {

                System.out.println("Aborted after "

                                   + (new Date().getTime() - startDate.getTime())

                                   + " ms");

                interrupt();

            }

        }

    }

    public static void main(String[] args) throws Exception {

        HotSpotDiagnosticMXBean diagnostic =

                ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class);

        System.out.println("Max memory= " + MAX_MEMORY + " bytes");

        int obj_size = 0;

        long seconds_to_run = 0;

        if (args.length != 2) {

            throw new RuntimeException("Object size argument must be supplied");

        } else {

            obj_size = Integer.parseInt(args[0]);

            seconds_to_run = Integer.parseInt(args[1]);

        }

        System.out.println("Objects size= " + obj_size + " bytes");

        System.out.println("Seconds to run=" + seconds_to_run);

        int region_size =

            Integer.parseInt(diagnostic.getVMOption("G1HeapRegionSize").getValue());

        if (obj_size < (region_size / 2)) {

            throw new RuntimeException("Object size " + obj_size +

                                       " is not humongous with region size " + region_size);

        }

        ExecutorService executor =

            Executors.newFixedThreadPool(THREAD_COUNT, new NamedThreadFactory());

        System.out.println("Starting " + THREAD_COUNT + " threads");

        for (int i = 0; i < THREAD_COUNT; i++) {

            executor.execute(new Runner(obj_size));

        }

        Thread.sleep(seconds_to_run * 1000);

        executor.shutdownNow();

        if (!executor.awaitTermination(10, TimeUnit.SECONDS)) {

            System.err.println("Thread pool did not terminate after 10 seconds after shutdown");

        }

    }

    private static final long MAX_MEMORY = Runtime.getRuntime().maxMemory();

    private static final int OLD_COUNT = 4;

    private static final int THREAD_COUNT = 12;

    private static final String THREAD_NAME = "TestGreyRH-";

}