/*
* Copyright (c) 2017, Google 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 MyPackage;
import java.util.ArrayList;
import java.util.List;
/** API for handling the underlying heap sampling monitoring system. */
public class HeapMonitor {
static {
try {
System.loadLibrary("HeapMonitor");
} catch (UnsatisfiedLinkError ule) {
System.err.println("Could not load HeapMonitor library");
System.err.println("java.library.path: " + System.getProperty("java.library.path"));
throw ule;
}
}
private static volatile int arrays[][];
/** Enable heap monitoring sampling given a rate and maximum garbage to keep in memory. */
public native static void enableSampling(int rate, int maximumGarbage);
/** Enable heap monitoring sampling given a rate. */
public static void enableSampling(int rate) {
enableSampling(rate, 200);
}
/** Enable heap monitoring sampling with default values for rate and maximum garbage. */
public static void enableSampling() {
enableSampling(1 << 19);
}
public native static void disableSampling();
public native static boolean areSamplingStatisticsZero();
public native static boolean statsHaveExpectedNumberSamples(int expected, int percentError);
/** Do the frames provided exist in live, recent garbage, and frequent garbage. */
public native static boolean framesExistEverywhere(Frame[] frames);
/** Do the frames provided not exist in live, recent garbage, and frequent garbage. */
public native static boolean framesExistNowhere(Frame[] frames);
/**
* Allocate memory but first create a stack trace of a particular depth.
*
* @return list of frames for the allocation.
*/
public static List allocate(int depth) {
List frames = new ArrayList();
if (depth > 1) {
createStackDepth(depth - 1, frames);
frames.add(new Frame("allocate", "(I)Ljava/util/List;", "HeapMonitor.java", 73));
} else {
actuallyAllocate(frames);
frames.add(new Frame("actuallyAllocate", "(Ljava/util/List;)I", "HeapMonitor.java", 127));
frames.add(new Frame("allocate", "(I)Ljava/util/List;", "HeapMonitor.java", 76));
}
return frames;
}
/**
* Allocate memory but first create a stack trace.
*
* @return list of frames for the allocation.
*/
public static List allocate() {
int sum = 0;
List frames = new ArrayList();
allocate(frames);
frames.add(new Frame("allocate", "()Ljava/util/List;", "HeapMonitor.java", 91));
return frames;
}
private static void createStackDepth(int depth, List frames) {
if (depth > 1) {
createStackDepth(depth - 1, frames);
frames.add(new Frame("createStackDepth", "(ILjava/util/List;)V", "HeapMonitor.java", 98));
} else {
allocate(frames);
frames.add(new Frame("createStackDepth", "(ILjava/util/List;)V", "HeapMonitor.java", 101));
}
}
private static void allocate(List frames) {
int sum = 0;
for (int j = 0; j < 1000; j++) {
sum += actuallyAllocate(frames);
}
frames.add(new Frame("actuallyAllocate", "(Ljava/util/List;)I", "HeapMonitor.java", 127));
frames.add(new Frame("allocate", "(Ljava/util/List;)V", "HeapMonitor.java", 109));
}
private static int actuallyAllocate(List frames) {
int sum = 0;
// Let us assume that a 1-element array is 24 bytes of memory and we want
// 2MB allocated.
int iterations = (1 << 19) / 6;
if (arrays == null) {
arrays = new int[iterations][];
}
for (int i = 0; i < iterations; i++) {
int tmp[] = new int[1];
// Force it to be kept and, at the same time, wipe out any previous data.
arrays[i] = tmp;
sum += arrays[0][0];
}
return sum;
}
/** Remove the reference to the global array to free data at the next GC. */
public static void freeStorage() {
arrays = null;
}
}