jdk

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/*
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 * Copyright (c) 2014, 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;
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/**
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 * @test TestSmallHeap
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 * @bug 8067438 8152239
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 * @summary Verify that starting the VM with a small heap works
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 * @library /test/lib
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 * @modules java.base/jdk.internal.misc
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 * @build jdk.test.whitebox.WhiteBox
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 * @run driver jdk.test.lib.helpers.ClassFileInstaller jdk.test.whitebox.WhiteBox
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 * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI gc.TestSmallHeap
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 */
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/* Note: It would be nice to verify the minimal supported heap size here,
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 * but we align the heap size based on the card table size. And the card table
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 * size is aligned based on the minimal pages size provided by the os. This
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 * means that on most platforms, where the minimal page size is 4k, we get a
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 * minimal heap size of 2m but on Solaris/Sparc we have a page size of 8k and
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 * get a minimal heap size of 4m. And on platforms where the page size is 64k
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 * we get a minimal heap size of 32m. We never use large pages for the card table.
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 *
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 * There is also no check in the VM for verifying that the maximum heap size
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 * is larger than the supported minimal heap size.
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 *
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 * To work around these behaviors this test uses -Xmx4m but then
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 * calculates what the expected heap size should be. The calculation is a
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 * simplified version of the code in the VM. We assume that the card table will
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 * use one page. Each byte in the card table corresponds to 512 bytes on the heap.
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 * So, the expected heap size is page_size * 512.
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 *
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 * There is no formal requirement for the minimal value of the maximum heap size
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 * the VM should support. In most cases the VM could start with -Xmx2m.
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 * But with 2m limit GC could be triggered before VM initialization completed.
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 * Therefore we start the VM with 4M heap.
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 */
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import jdk.test.lib.Asserts;
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import jdk.test.lib.process.OutputAnalyzer;
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import jdk.test.lib.process.ProcessTools;
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import jtreg.SkippedException;
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import jdk.test.whitebox.WhiteBox;
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import jdk.test.whitebox.gc.GC;
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public class TestSmallHeap {
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    public static void main(String[] args) throws Exception {
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        // Do all work in the VM driving the test, the VM
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        // with the small heap size should do as little as
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        // possible to avoid hitting an OOME.
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        WhiteBox wb = WhiteBox.getWhiteBox();
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        int pageSize = wb.getVMPageSize();
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        int heapBytesPerCard = 512;
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        long expectedMaxHeap = pageSize * heapBytesPerCard;
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        boolean noneGCSupported = true;
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        if (GC.Parallel.isSupported()) {
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            noneGCSupported = false;
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            verifySmallHeapSize("-XX:+UseParallelGC", expectedMaxHeap);
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        }
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        if (GC.Serial.isSupported()) {
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            noneGCSupported = false;
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            verifySmallHeapSize("-XX:+UseSerialGC", expectedMaxHeap);
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        }
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        if (GC.G1.isSupported()) {
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            noneGCSupported = false;
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            verifySmallHeapSize("-XX:+UseG1GC", expectedMaxHeap);
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        }
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        if (noneGCSupported) {
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            throw new SkippedException("Skipping test because none of Parallel/Serial/G1 is supported.");
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        }
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    }
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    private static void verifySmallHeapSize(String gc, long expectedMaxHeap) throws Exception {
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        long minMaxHeap = 4 * 1024 * 1024;
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        OutputAnalyzer analyzer = ProcessTools.executeLimitedTestJava(
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            gc,
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            "-Xmx" + minMaxHeap,
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            "-XX:+PrintFlagsFinal",
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            VerifyHeapSize.class.getName());
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        analyzer.shouldHaveExitValue(0);
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        expectedMaxHeap = Math.max(expectedMaxHeap, minMaxHeap);
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        long maxHeapSize = Long.parseLong(analyzer.firstMatch("MaxHeapSize.+=\\s+(\\d+)",1));
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        long actualHeapSize = Long.parseLong(analyzer.firstMatch(VerifyHeapSize.actualMsg + "(\\d+)",1));
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        Asserts.assertEQ(maxHeapSize, expectedMaxHeap);
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        Asserts.assertLessThanOrEqual(actualHeapSize, maxHeapSize);
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    }
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}
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class VerifyHeapSize {
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    public static final String actualMsg = "Actual heap size: ";
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    public static void main(String args[]) {
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        // Avoid string concatenation
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        System.out.print(actualMsg);
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        System.out.println(Runtime.getRuntime().maxMemory());
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    }
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}
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