/*
 * Copyright (c) 2019, 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
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 * questions.
 */

package gc.z;

/*
 * @test TestHighUsage
 * @requires vm.gc.Z & !vm.graal.enabled
 * @summary Test ZGC "High Usage" rule
 * @library /test/lib
 * @run main/othervm gc.z.TestHighUsage
 */

import java.util.LinkedList;
import jdk.test.lib.process.ProcessTools;

public class TestHighUsage {
    static class Test {
        private static final int K = 1024;
        private static final int M = K * K;
        private static final long startAt = 16 * M;
        private static final long spikeAt = 4 * M;
        private static volatile LinkedList<byte[]> keepAlive;
        private static volatile Object dummy;

        public static void main(String[] args) throws Exception {
            System.out.println("Allocating live-set");

            // Allocate live-set
            keepAlive = new LinkedList<>();
            while (Runtime.getRuntime().freeMemory() > startAt) {
                while (Runtime.getRuntime().freeMemory() > startAt) {
                    keepAlive.add(new byte[128 * K]);
                }

                // Compact live-set and let allocation rate settle down
                System.gc();
                Thread.sleep(2000);
            }

            System.out.println("Allocating garbage slowly");

            // Allocate garbage slowly, such that the sampled allocation rate on
            // average becomes zero MB/s for the last 1 second windows. If free
            // memory goes below the spike limit we induce an allocation spike.
            // The expected behavior is that the "High Usage" rule kicks in before
            // the spike happens, avoiding an "Allocation Stall".
            for (int i = 0; i < 300; i++) {
                final long free = Runtime.getRuntime().freeMemory();
                System.out.println("Free: " + (free / M) + "M");

                if (free > spikeAt) {
                    // Low allocation rate
                    dummy = new byte[128 * K];
                } else {
                    // High allocation rate

                    // Before inducing an allocation spike, give the GC time to
                    // complete a cycle. This is needed in case the test system
                    // is starved on CPU, in which case the GC might not otherwise
                    // be able to complete a cycle before the allocation spike
                    // happens, resulting in an allocation stall.
                    Thread.sleep(50000);

                    dummy = new byte[8 * M];
                }

                Thread.sleep(250);
            }

            System.out.println("Done");
        }
    }

    public static void main(String[] args) throws Exception {
        ProcessTools.executeTestJvm(new String[]{ "-XX:+UnlockExperimentalVMOptions",
                                                  "-XX:+UseZGC",
                                                  "-XX:+UnlockDiagnosticVMOptions",
                                                  "-XX:-ZProactive",
                                                  "-Xms128M",
                                                  "-Xmx128M",
                                                  "-XX:ParallelGCThreads=1",
                                                  "-XX:ConcGCThreads=1",
                                                  "-Xlog:gc,gc+start",
                                                  Test.class.getName() })
                    .shouldNotContain("Allocation Stall")
                    .shouldContain("High Usage")
                    .shouldHaveExitValue(0);
    }
}