/*
* Copyright 2009 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.dev.util;
import java.io.File;
import java.lang.management.ManagementFactory;
import java.lang.reflect.Method;
/**
* Utility methods for dealing with VM memory.
*/
public class Memory {
/**
* Number of times to call System.gc() before measuring the memory
* usage/dumping the heap. This value was arrived at through trial-and-error
* on the Sun JVM; memory usage seems to stabilize after 3 to 4 runs. We think
* the reason it requires multiple runs is due to the generational aspect of
* garbage collection.
*/
private static final int NUM_GC_COLLECTIONS = 4;
/**
* Set this system property to a filename suffix to dump heaps into.
*/
private static final String PROPERTY_DUMP_HEAP = "gwt.memory.dumpHeap";
/**
* Set this system property to dump memory usage at various points.
*/
private static final String PROPERTY_DUMP_MEMORY = "gwt.memory.usage";
/**
* Time to start measuring since the last memory measurement/dump, or
* application startup.
*/
private static long startTime;
public static void initialize() {
if (System.getProperty(PROPERTY_DUMP_MEMORY) != null) {
System.out.println("Will print mem usage");
}
if (System.getProperty(PROPERTY_DUMP_HEAP) != null) {
System.out.println("Will dump heap into: *-"
+ System.getProperty(PROPERTY_DUMP_HEAP));
}
startTime = System.currentTimeMillis();
}
public static void main(String[] args) {
initialize();
System.setProperty(PROPERTY_DUMP_MEMORY, "");
maybeDumpMemory("test");
}
public static void maybeDumpMemory(String info) {
long elapsed = System.currentTimeMillis() - startTime;
if (System.getProperty(PROPERTY_DUMP_MEMORY) != null) {
for (int i = 0; i < NUM_GC_COLLECTIONS; ++i) {
System.gc();
}
long heap = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getUsed();
long nonHeap = ManagementFactory.getMemoryMXBean().getNonHeapMemoryUsage().getUsed();
String infoString = String.format("[%.18s]", info);
System.out.println(String.format(
"%-20s %10d heap, %10d nonheap, %10d total, %10.2fs", infoString,
heap, nonHeap, heap + nonHeap, (double) elapsed / 1000));
}
String dumpFile = System.getProperty(PROPERTY_DUMP_HEAP);
if (dumpFile != null) {
String procName = ManagementFactory.getRuntimeMXBean().getName();
dumpFile = info + "-" + procName + dumpFile;
new File(dumpFile).delete();
try {
Class<?> beanClass = Class.forName("com.sun.management.HotSpotDiagnosticMXBean");
Object bean = ManagementFactory.newPlatformMXBeanProxy(
ManagementFactory.getPlatformMBeanServer(),
"com.sun.management:type=HotSpotDiagnostic", beanClass);
Method dumpHeapMethod = beanClass.getDeclaredMethod("dumpHeap",
String.class, Boolean.TYPE);
dumpHeapMethod.invoke(bean, dumpFile, true);
System.out.println("(" + info + ") dumped heap into: " + dumpFile);
} catch (Throwable e) {
System.err.println("Unable to dump heap");
e.printStackTrace();
}
}
// Reset for next call
startTime = System.currentTimeMillis();
}
}