jdk

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/*
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 * Copyright (c) 2020, 2023, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 */
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package gc.stress;
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/*
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 * @test TestStressUncommit
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 * @key stress
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 * @summary Stress uncommitting by allocating and releasing memory
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 * @requires vm.gc.G1
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 * @library /test/lib
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 * @modules java.base/jdk.internal.misc
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 * @run driver/timeout=1300 gc.stress.TestStressG1Uncommit
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 */
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import java.lang.management.ManagementFactory;
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import java.lang.management.MemoryMXBean;
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import java.time.Duration;
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import java.time.Instant;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.LinkedList;
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import java.util.concurrent.ConcurrentLinkedQueue;
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import java.util.concurrent.CountDownLatch;
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import java.util.concurrent.ExecutorService;
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import java.util.concurrent.Executors;
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import java.util.concurrent.TimeUnit;
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import com.sun.management.ThreadMXBean;
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import jdk.test.lib.Asserts;
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import jdk.test.lib.process.ProcessTools;
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import jdk.test.lib.process.OutputAnalyzer;
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public class TestStressG1Uncommit {
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    public static void main(String[] args) throws Exception {
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        ArrayList<String> options = new ArrayList<>();
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        Collections.addAll(options,
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            "-Xlog:gc,gc+heap+region=debug",
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            "-XX:+UseG1GC",
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            StressUncommit.class.getName()
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        );
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        OutputAnalyzer output = ProcessTools.executeLimitedTestJava(options);
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        output.shouldHaveExitValue(0);
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        output.shouldMatch("Uncommit regions");
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        output.outputTo(System.out);
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    }
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}
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class StressUncommit {
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    private static final long M = 1024 * 1024;
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    private static final long G = 1024 * M;
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    private static final Instant StartTime = Instant.now();
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    private static final ThreadMXBean threadBean = (ThreadMXBean) ManagementFactory.getThreadMXBean();
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    private static final MemoryMXBean memoryBean = ManagementFactory.getMemoryMXBean();
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    private static ConcurrentLinkedQueue<Object> globalKeepAlive;
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    public static void main(String args[]) throws InterruptedException {
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        // Leave 20% head room to try to avoid Full GCs.
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        long allocationSize = (long) (Runtime.getRuntime().maxMemory() * 0.8);
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        // Figure out suitable number of workers (~1 per gig).
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        int gigsOfAllocation = (int) Math.ceil((double) allocationSize / G);
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        int numWorkers = Math.min(gigsOfAllocation, Runtime.getRuntime().availableProcessors());
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        long workerAllocation = allocationSize / numWorkers;
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        log("Using " + numWorkers + " workers, each allocating: ~" + (workerAllocation / M) + "M");
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        ExecutorService workers = Executors.newFixedThreadPool(numWorkers);
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        try {
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            int iteration = 1;
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            // Run for 60 seconds.
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            while (uptime() < 60) {
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                log("Interation: " + iteration++);
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                globalKeepAlive = new ConcurrentLinkedQueue<>();
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                // Submit work to executor.
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                CountDownLatch workersRunning = new CountDownLatch(numWorkers);
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                for (int j = 0; j < numWorkers; j++) {
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                    // Submit worker task.
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                    workers.submit(() -> {
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                    allocateToLimit(workerAllocation);
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                    workersRunning.countDown();
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                    });
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                }
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                // Wait for tasks to complete.
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                workersRunning.await();
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                // Clear the reference holding all task allocations alive.
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                globalKeepAlive = null;
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                // Do a GC that should shrink the heap.
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                long committedBefore = memoryBean.getHeapMemoryUsage().getCommitted();
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                System.gc();
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                long committedAfter = memoryBean.getHeapMemoryUsage().getCommitted();
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                Asserts.assertLessThan(committedAfter, committedBefore);
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            }
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        } finally {
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            workers.shutdown();
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            workers.awaitTermination(5, TimeUnit.SECONDS);
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        }
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    }
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    private static void allocateToLimit(long limit) {
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        var localKeepAlive = new LinkedList<byte[]>();
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        long currentAllocation = threadBean.getCurrentThreadAllocatedBytes();
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        long allocationLimit = currentAllocation + limit;
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        while (currentAllocation < allocationLimit) {
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            // Check roughly every megabyte.
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            for (long j = 0 ; j < 1000; j++) {
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            localKeepAlive.add(new byte[1024]);
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            }
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            currentAllocation = threadBean.getCurrentThreadAllocatedBytes();
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        }
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        // Add to globalKeepAlive for realease by main thread.
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        globalKeepAlive.add(localKeepAlive);
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    }
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    private static long uptime() {
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        return Duration.between(StartTime, Instant.now()).getSeconds();
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    }
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    private static void log(String text) {
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        System.out.println(uptime() + "s: " + text);
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    }
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}
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