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/*
* Copyright (c) 2014, 2022, 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.
*/
package gc;
/**
* @test TestSmallHeap
* @bug 8067438 8152239
* @summary Verify that starting the VM with a small heap works
* @library /test/lib
* @modules java.base/jdk.internal.misc
* @build jdk.test.whitebox.WhiteBox
* @run driver jdk.test.lib.helpers.ClassFileInstaller jdk.test.whitebox.WhiteBox
* @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI gc.TestSmallHeap
*/
/* Note: It would be nice to verify the minimal supported heap size here,
* but we align the heap size based on the card table size. And the card table
* size is aligned based on the minimal pages size provided by the os. This
* means that on most platforms, where the minimal page size is 4k, we get a
* minimal heap size of 2m but on Solaris/Sparc we have a page size of 8k and
* get a minimal heap size of 4m. And on platforms where the page size is 64k
* we get a minimal heap size of 32m. We never use large pages for the card table.
*
* There is also no check in the VM for verifying that the maximum heap size
* is larger than the supported minimal heap size.
*
* To work around these behaviors this test uses -Xmx4m but then
* calculates what the expected heap size should be. The calculation is a
* simplified version of the code in the VM. We assume that the card table will
* use one page. Each byte in the card table corresponds to 512 bytes on the heap.
* So, the expected heap size is page_size * 512.
*
* There is no formal requirement for the minimal value of the maximum heap size
* the VM should support. In most cases the VM could start with -Xmx2m.
* But with 2m limit GC could be triggered before VM initialization completed.
* Therefore we start the VM with 4M heap.
*/
import jdk.test.lib.Asserts;
import jdk.test.lib.process.OutputAnalyzer;
import jdk.test.lib.process.ProcessTools;
import jtreg.SkippedException;
import jdk.test.whitebox.WhiteBox;
import jdk.test.whitebox.gc.GC;
public class TestSmallHeap {
public static void main(String[] args) throws Exception {
// Do all work in the VM driving the test, the VM
// with the small heap size should do as little as
// possible to avoid hitting an OOME.
WhiteBox wb = WhiteBox.getWhiteBox();
int pageSize = wb.getVMPageSize();
int heapBytesPerCard = 512;
long expectedMaxHeap = pageSize * heapBytesPerCard;
boolean noneGCSupported = true;
if (GC.Parallel.isSupported()) {
noneGCSupported = false;
verifySmallHeapSize("-XX:+UseParallelGC", expectedMaxHeap);
}
if (GC.Serial.isSupported()) {
noneGCSupported = false;
verifySmallHeapSize("-XX:+UseSerialGC", expectedMaxHeap);
}
if (GC.G1.isSupported()) {
noneGCSupported = false;
verifySmallHeapSize("-XX:+UseG1GC", expectedMaxHeap);
}
if (noneGCSupported) {
throw new SkippedException("Skipping test because none of Parallel/Serial/G1 is supported.");
}
}
private static void verifySmallHeapSize(String gc, long expectedMaxHeap) throws Exception {
long minMaxHeap = 4 * 1024 * 1024;
ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(
gc,
"-Xmx" + minMaxHeap,
"-XX:+PrintFlagsFinal",
VerifyHeapSize.class.getName());
OutputAnalyzer analyzer = new OutputAnalyzer(pb.start());
analyzer.shouldHaveExitValue(0);
expectedMaxHeap = Math.max(expectedMaxHeap, minMaxHeap);
long maxHeapSize = Long.parseLong(analyzer.firstMatch("MaxHeapSize.+=\\s+(\\d+)",1));
long actualHeapSize = Long.parseLong(analyzer.firstMatch(VerifyHeapSize.actualMsg + "(\\d+)",1));
Asserts.assertEQ(maxHeapSize, expectedMaxHeap);
Asserts.assertLessThanOrEqual(actualHeapSize, maxHeapSize);
}
}
class VerifyHeapSize {
public static final String actualMsg = "Actual heap size: ";
public static void main(String args[]) {
// Avoid string concatenation
System.out.print(actualMsg);
System.out.println(Runtime.getRuntime().maxMemory());
}
}
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