java.lang.management.MemoryUsage Java Examples

public static Map<String, MemoryUsage> getMemoryPoolUsage() {
    Map<String, MemoryUsage> gcMemory = new HashMap<String, MemoryUsage>();
    for (MemoryPoolMXBean memoryPoolMXBean : memoryPoolMXBeans) {
        String name = memoryPoolMXBean.getName();
        if (edenSpace.contains(name)) {
            gcMemory.put("eden", memoryPoolMXBean.getUsage());
        } else if (survivorSpace.contains(name)) {
            gcMemory.put("survivor", memoryPoolMXBean.getUsage());
        } else if (oldSpace.contains(name)) {
            gcMemory.put("old", memoryPoolMXBean.getUsage());
        } else if (permSpace.contains(name)) {
            gcMemory.put("perm", memoryPoolMXBean.getUsage());
        } else if (codeCacheSpace.contains(name)) {
            gcMemory.put("codeCache", memoryPoolMXBean.getUsage());
        }

    }
    return gcMemory;
}
 

public static void printMemoryUsage() {
    long total = Runtime.getRuntime().totalMemory();
    long free = Runtime.getRuntime().freeMemory();
    long used = total - free;

    System.out.println("Heap size:");
    System.out.println("-------------------");
    System.out.println("TotalMemory: " + formatSize(total));
    System.out.println("UsedMemory:  " + formatSize(used));
    System.out.println("FreeMemory:  " + formatSize(free));

    MemoryUsage mu = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();
    MemoryUsage nmu = ManagementFactory.getMemoryMXBean().getNonHeapMemoryUsage();
    System.out.println("HeapMemoryUsage: " + mu);
    System.out.println("NonHeapMemoryUsage: " + nmu);
}
 

private final void test() {
    System.gc();
    MemoryUsagePrinter.printMemoryUsage("init");

    allocate();
    MemoryUsagePrinter.printMemoryUsage("allocated");
    MemoryUsage muFull = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();

    free();
    MemoryUsagePrinter.printMemoryUsage("free");
    MemoryUsage muFree = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();

    assertLessThan(muFree.getCommitted(), muFull.getCommitted(), String.format(
            "committed free heap size is not less than committed full heap size, heap hasn't been shrunk?%n"
            + "%s = %s%n%s = %s",
            MIN_FREE_RATIO_FLAG_NAME,
            ManagementFactoryHelper.getDiagnosticMXBean().getVMOption(MIN_FREE_RATIO_FLAG_NAME).getValue(),
            MAX_FREE_RATIO_FLAG_NAME,
            ManagementFactoryHelper.getDiagnosticMXBean().getVMOption(MAX_FREE_RATIO_FLAG_NAME).getValue()
    ));
}
 

@Override
public List<MemoryPool> getMemoryPoolMetricsList() {
    List<MemoryPool> poolList = new LinkedList<MemoryPool>();
    for (MemoryPoolMXBean bean : beans) {
        String name = bean.getName();
        PoolType type;
        if (contains(getCodeCacheNames(), name)) {
            type = PoolType.CODE_CACHE_USAGE;
        } else if (contains(getEdenNames(), name)) {
            type = PoolType.NEWGEN_USAGE;
        } else if (contains(getOldNames(), name)) {
            type = PoolType.OLDGEN_USAGE;
        } else if (contains(getSurvivorNames(), name)) {
            type = PoolType.SURVIVOR_USAGE;
        } else if (contains(getMetaspaceNames(), name)) {
            type = PoolType.METASPACE_USAGE;
        } else if (contains(getPermNames(), name)) {
            type = PoolType.PERMGEN_USAGE;
        } else {
            continue;
        }

        MemoryUsage usage = bean.getUsage();
        poolList.add(MemoryPool.newBuilder()
                               .setType(type)
                               .setInit(usage.getInit())
                               .setMax(usage.getMax())
                               .setCommitted(usage.getCommitted())
                               .setUsed(usage.getUsed())
                               .build());
    }
    return poolList;
}
 

MemoryUsage getPeakMemoryUsage() {
    try {
        final Map<Object, Object> m = JvmContextFactory.getUserData();

        if (m != null) {
            final MemoryUsage cached = (MemoryUsage)
                m.get(entryPeakMemoryTag);
            if (cached != null) {
                if (log.isDebugOn())
                    log.debug("getPeakMemoryUsage",
                          entryPeakMemoryTag + " found in cache.");
                return cached;
            }

            MemoryUsage u = pool.getPeakUsage();
            if (u == null) u = ZEROS;

            m.put(entryPeakMemoryTag,u);
            return u;
        }
        // Should never come here.
        // Log error!
        log.trace("getPeakMemoryUsage", "ERROR: should never come here!");
        return ZEROS;
    } catch (RuntimeException x) {
        log.trace("getPeakMemoryUsage",
              "Failed to get MemoryUsage: " + x);
        log.debug("getPeakMemoryUsage",x);
        throw x;
    }

}
 

private static TextComponent generateMemoryPoolDiagram(MemoryUsage usage, MemoryUsage collectionUsage, int length) {
    double used = usage.getUsed();
    double collectionUsed = used;
    if (collectionUsage != null) {
        collectionUsed = collectionUsage.getUsed();
    }
    double committed = usage.getCommitted();
    double max = usage.getMax();

    int usedChars = (int) ((used * length) / max);
    int collectionUsedChars = (int) ((collectionUsed * length) / max);
    int committedChars = (int) ((committed * length) / max);

    TextComponent.Builder line = TextComponent.builder(Strings.repeat("/", collectionUsedChars)).color(TextColor.GRAY);

    if (usedChars > collectionUsedChars) {
        line.append(TextComponent.of("|", TextColor.RED));
        line.append(TextComponent.of(Strings.repeat("/", (usedChars - collectionUsedChars) - 1), TextColor.GRAY));
    }
    if (committedChars > usedChars) {
        line.append(TextComponent.of(Strings.repeat(" ", (committedChars - usedChars) - 1)));
        line.append(TextComponent.of("|", TextColor.YELLOW));
    }
    if (length > committedChars) {
        line.append(TextComponent.of(Strings.repeat(" ", (length - committedChars))));
    }

    return TextComponent.builder("")
            .append(TextComponent.of("[", TextColor.DARK_GRAY))
            .append(line.build())
            .append(TextComponent.of("]", TextColor.DARK_GRAY))
            .build();
}
 

public static void badNameCompositeData() throws Exception {
    final int K = 1024;
    final Object[] values = {
        new Long(5 * K),
        new Long(1 * K),
        new Long(10 * K),
        new Long(2 * K),
        "Dummy",
        "Dummy",
    };

    CompositeType muct =
        new CompositeType("MyMemoryUsageCompositeType",
                          "CompositeType for MemoryUsage",
                           badMUItemNames,
                           badMUItemNames,
                           memoryUsageItemTypes);
    CompositeData cd =
        new CompositeDataSupport(muct,
                                 badMUItemNames,
                                 values);
    try {
        MemoryUsage u = MemoryUsage.from(cd);
    } catch (IllegalArgumentException e) {
        System.out.println("Expected exception: " +
            e.getMessage());
        return;
    }
    throw new RuntimeException(
        "IllegalArgumentException not thrown");
}
 

MemoryUsage getHeapMemoryUsage() {
    try {
        final Map<Object, Object> m = JvmContextFactory.getUserData();

        if (m != null) {
            final MemoryUsage cached = (MemoryUsage)m.get(heapMemoryTag);
            if (cached != null) {
                log.debug("getHeapMemoryUsage",
                      "jvmMemory.getHeapMemoryUsage found in cache.");
                return cached;
            }

            final MemoryUsage u = getMemoryUsage(MemoryType.HEAP);

            // getHeapMemoryUsage() never returns null.
            //
            // if (u == null) u=MemoryUsage.INVALID;

            m.put(heapMemoryTag,u);
            return u;
        }

        // Should never come here.
        // Log error!
        log.trace("getHeapMemoryUsage", "ERROR: should never come here!");
        return getMemoryUsage(MemoryType.HEAP);
    } catch (RuntimeException x) {
        log.trace("getHeapMemoryUsage",
              "Failed to get HeapMemoryUsage: " + x);
        log.debug("getHeapMemoryUsage",x);
        throw x;
    }
}
 

/**
 * Triggers this sensor piggybacking a memory usage object.
 * This method sets this sensor on
 * and increments the count with the input <tt>increment</tt>.
 */
public void trigger(int increment, MemoryUsage usage) {
    synchronized (lock) {
        on = true;
        count += increment;
        // Do something here...
    }
    triggerAction(usage);
}
 

private MemoryUsage getMemoryUsage(MemoryType type) {
    if (type == MemoryType.HEAP) {
        return ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();
    } else {
        return ManagementFactory.getMemoryMXBean().getNonHeapMemoryUsage();
    }
}
 

private static void checkGcInfo(String name, GcInfo info) throws Exception {
    System.out.println("GC statistic for : " + name);
    System.out.print("GC #" + info.getId());
    System.out.print(" start:" + info.getStartTime());
    System.out.print(" end:" + info.getEndTime());
    System.out.println(" (" + info.getDuration() + "ms)");
    Map usage = info.getMemoryUsageBeforeGc();

    List pnames = new ArrayList();
    for (Iterator iter = usage.entrySet().iterator(); iter.hasNext(); ) {
        Map.Entry entry = (Map.Entry) iter.next();
        String poolname = (String) entry.getKey();
        pnames.add(poolname);
        MemoryUsage busage = (MemoryUsage) entry.getValue();
        MemoryUsage ausage = (MemoryUsage) info.getMemoryUsageAfterGc().get(poolname);
        if (ausage == null) {
            throw new RuntimeException("After Gc Memory does not exist" +
                " for " + poolname);
        }
        System.out.println("Usage for pool " + poolname);
        System.out.println("   Before GC: " + busage);
        System.out.println("   After GC: " + ausage);
    }

    // check if memory usage for all memory pools are returned
    List pools = ManagementFactory.getMemoryPoolMXBeans();
    for (Iterator iter = pools.iterator(); iter.hasNext(); ) {
        MemoryPoolMXBean p = (MemoryPoolMXBean) iter.next();
        if (!pnames.contains(p.getName())) {
            throw new RuntimeException("GcInfo does not contain " +
                "memory usage for pool " + p.getName());
        }
    }
}
 

public void setCollectionUsageThreshold(long newThreshold) {
    if (!isCollectionUsageThresholdSupported()) {
        throw new UnsupportedOperationException(
            "CollectionUsage threshold is not supported");
    }

    Util.checkControlAccess();

    MemoryUsage usage = getUsage0();
    if (newThreshold < 0) {
        throw new IllegalArgumentException(
            "Invalid threshold: " + newThreshold);
    }

    if (usage.getMax() != -1 && newThreshold > usage.getMax()) {
        throw new IllegalArgumentException(
            "Invalid threshold: " + newThreshold +
                 " > max (" + usage.getMax() + ").");
    }

    synchronized (this) {
        if (!gcSensorRegistered) {
            // pass the sensor to VM to begin monitoring
            gcSensorRegistered = true;
            setPoolCollectionSensor(gcSensor);
        }
        setCollectionThreshold0(collectionThreshold, newThreshold);
        this.collectionThreshold = newThreshold;
    }
}
 

/**
 * Triggers this sensor piggybacking a memory usage object.
 * This method sets this sensor on
 * and increments the count with the input <tt>increment</tt>.
 */
public void trigger(int increment, MemoryUsage usage) {
    synchronized (lock) {
        on = true;
        count += increment;
        // Do something here...
    }
    triggerAction(usage);
}
 

public static Map<String, MemoryUsage>
        getMemoryUsageAfterGc(CompositeData cd) {
    try {
        TabularData td = (TabularData) cd.get(MEMORY_USAGE_AFTER_GC);
        //return (Map<String,MemoryUsage>)
        return cast(memoryUsageMapType.toJavaTypeData(td));
    } catch (InvalidObjectException | OpenDataException e) {
        // Should never reach here
        throw new AssertionError(e);
    }
}
 

/**
 * Returns memory usage for the current java process.
 */
public static List<String> memoryUsage() throws Exception {
    final MemoryUsage heapMemoryUsage = MXBeanHolder.memoryMxBean.getHeapMemoryUsage();
    final MemoryUsage nonHeapMemoryUsage = MXBeanHolder.memoryMxBean.getNonHeapMemoryUsage();

    final List<String> memoryUsageList = new LinkedList<>();
    memoryUsageList.add("********************************** Memory Usage **********************************"
                        + Constants.NEWLINE);
    memoryUsageList.add("Heap Memory Usage: " + heapMemoryUsage.toString() + Constants.NEWLINE);
    memoryUsageList.add("NonHeap Memory Usage: " + nonHeapMemoryUsage.toString() + Constants.NEWLINE);

    return memoryUsageList;
}
 

public static Map<String, MemoryUsage>
        getMemoryUsageAfterGc(CompositeData cd) {
    try {
        TabularData td = (TabularData) cd.get(MEMORY_USAGE_AFTER_GC);
        //return (Map<String,MemoryUsage>)
        return cast(memoryUsageMapType.toJavaTypeData(td));
    } catch (InvalidObjectException | OpenDataException e) {
        // Should never reach here
        throw new AssertionError(e);
    }
}
 

public static long getBytesUsed(final MemoryPoolMXBean memoryPool,
    boolean getCurrentUsage) {
  if (getCurrentUsage) {
    return memoryPool.getUsage().getUsed();
  }
  else {
    final MemoryUsage usage = memoryPool.getCollectionUsage();
    if (usage != null) {
      return usage.getUsed();
    }
    else {
      return memoryPool.getUsage().getUsed();
    }
  }
}
 

public void setUsageThreshold(long newThreshold) {
    if (!isUsageThresholdSupported()) {
        throw new UnsupportedOperationException(
            "Usage threshold is not supported");
    }

    Util.checkControlAccess();

    MemoryUsage usage = getUsage0();
    if (newThreshold < 0) {
        throw new IllegalArgumentException(
            "Invalid threshold: " + newThreshold);
    }

    if (usage.getMax() != -1 && newThreshold > usage.getMax()) {
        throw new IllegalArgumentException(
            "Invalid threshold: " + newThreshold +
            " must be <= maxSize." +
            " Committed = " + usage.getCommitted() +
            " Max = " + usage.getMax());
    }

    synchronized (this) {
        if (!usageSensorRegistered) {
            // pass the sensor to VM to begin monitoring
            usageSensorRegistered = true;
            setPoolUsageSensor(usageSensor);
        }
        setUsageThreshold0(usageThreshold, newThreshold);
        this.usageThreshold = newThreshold;
    }
}
 

public void setCollectionUsageThreshold(long newThreshold) {
    if (!isCollectionUsageThresholdSupported()) {
        throw new UnsupportedOperationException(
            "CollectionUsage threshold is not supported");
    }

    Util.checkControlAccess();

    MemoryUsage usage = getUsage0();
    if (newThreshold < 0) {
        throw new IllegalArgumentException(
            "Invalid threshold: " + newThreshold);
    }

    if (usage.getMax() != -1 && newThreshold > usage.getMax()) {
        throw new IllegalArgumentException(
            "Invalid threshold: " + newThreshold +
                 " > max (" + usage.getMax() + ").");
    }

    synchronized (this) {
        if (!gcSensorRegistered) {
            // pass the sensor to VM to begin monitoring
            gcSensorRegistered = true;
            setPoolCollectionSensor(gcSensor);
        }
        setCollectionThreshold0(collectionThreshold, newThreshold);
        this.collectionThreshold = newThreshold;
    }
}
 

MemoryUsage getCollectMemoryUsage() {
    try {
        final Map<Object, Object> m = JvmContextFactory.getUserData();

        if (m != null) {
            final MemoryUsage cached = (MemoryUsage)
                m.get(entryCollectMemoryTag);
            if (cached != null) {
                if (log.isDebugOn())
                    log.debug("getCollectMemoryUsage",
                              entryCollectMemoryTag + " found in cache.");
                return cached;
            }

            MemoryUsage u = pool.getCollectionUsage();
            if (u == null) u = ZEROS;

            m.put(entryCollectMemoryTag,u);
            return u;
        }
        // Should never come here.
        // Log error!
        log.trace("getCollectMemoryUsage",
                  "ERROR: should never come here!");
        return ZEROS;
    } catch (RuntimeException x) {
        log.trace("getPeakMemoryUsage",
              "Failed to get MemoryUsage: " + x);
        log.debug("getPeakMemoryUsage",x);
        throw x;
    }

}
 

public static Map<String, MemoryUsage>
        getMemoryUsageBeforeGc(CompositeData cd) {
    try {
        TabularData td = (TabularData) cd.get(MEMORY_USAGE_BEFORE_GC);
        return cast(memoryUsageMapType.toJavaTypeData(td));
    } catch (InvalidObjectException | OpenDataException e) {
        // Should never reach here
        throw new AssertionError(e);
    }
}
 

private MemoryUsage getMemoryUsage(MemoryType type) {
    if (type == MemoryType.HEAP) {
        return ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();
    } else {
        return ManagementFactory.getMemoryMXBean().getNonHeapMemoryUsage();
    }
}
 

public void setCollectionUsageThreshold(long newThreshold) {
    if (!isCollectionUsageThresholdSupported()) {
        throw new UnsupportedOperationException(
            "CollectionUsage threshold is not supported");
    }

    Util.checkControlAccess();

    MemoryUsage usage = getUsage0();
    if (newThreshold < 0) {
        throw new IllegalArgumentException(
            "Invalid threshold: " + newThreshold);
    }

    if (usage.getMax() != -1 && newThreshold > usage.getMax()) {
        throw new IllegalArgumentException(
            "Invalid threshold: " + newThreshold +
                 " > max (" + usage.getMax() + ").");
    }

    synchronized (this) {
        if (!gcSensorRegistered) {
            // pass the sensor to VM to begin monitoring
            gcSensorRegistered = true;
            setPoolCollectionSensor(gcSensor);
        }
        setCollectionThreshold0(collectionThreshold, newThreshold);
        this.collectionThreshold = newThreshold;
    }
}
 

public static void badTypeCompositeData() throws Exception {
    final int K = 1024;
    final Object[] values = {
        new Integer(5 * K),
        new Long(1 * K),
        new Long(10 * K),
        new Long(2 * K),
        "Dummy",
        "Dummy",
    };

    CompositeType muct =
        new CompositeType("MyMemoryUsageCompositeType",
                          "CompositeType for MemoryUsage",
                          memoryUsageItemNames,
                          memoryUsageItemNames,
                          badMUItemTypes);
    CompositeData cd =
       new CompositeDataSupport(muct,
                                memoryUsageItemNames,
                                values);
    try {
        MemoryUsage u = MemoryUsage.from(cd);
    } catch (IllegalArgumentException e) {
        System.out.println("Expected exception: " +
            e.getMessage());
        return;
    }
    throw new RuntimeException(
        "IllegalArgumentException not thrown");
}
 

private Map<String, Object> getMetricsByHost(String host) {
    Map<String, Object> metrics = InsertionOrderUtil.newMap();
    // JMX client operations for Cassandra.
    try (NodeProbe probe = this.newNodeProbe(host)) {
        MemoryUsage heapUsage = probe.getHeapMemoryUsage();
        metrics.put(MEM_USED, heapUsage.getUsed() / Bytes.MB);
        metrics.put(MEM_COMMITED, heapUsage.getCommitted() / Bytes.MB);
        metrics.put(MEM_MAX, heapUsage.getMax() / Bytes.MB);
        metrics.put(MEM_UNIT, "MB");
        metrics.put(DATA_SIZE, probe.getLoadString());
    } catch (Throwable e) {
        metrics.put(EXCEPTION, e.toString());
    }
    return metrics;
}
 

private static void checkGcInfo(String name, GcInfo info) throws Exception {
    System.out.println("GC statistic for : " + name);
    System.out.print("GC #" + info.getId());
    System.out.print(" start:" + info.getStartTime());
    System.out.print(" end:" + info.getEndTime());
    System.out.println(" (" + info.getDuration() + "ms)");
    Map usage = info.getMemoryUsageBeforeGc();

    List pnames = new ArrayList();
    for (Iterator iter = usage.entrySet().iterator(); iter.hasNext(); ) {
        Map.Entry entry = (Map.Entry) iter.next();
        String poolname = (String) entry.getKey();
        pnames.add(poolname);
        MemoryUsage busage = (MemoryUsage) entry.getValue();
        MemoryUsage ausage = (MemoryUsage) info.getMemoryUsageAfterGc().get(poolname);
        if (ausage == null) {
            throw new RuntimeException("After Gc Memory does not exist" +
                " for " + poolname);
        }
        System.out.println("Usage for pool " + poolname);
        System.out.println("   Before GC: " + busage);
        System.out.println("   After GC: " + ausage);
    }

    // check if memory usage for all memory pools are returned
    List pools = ManagementFactory.getMemoryPoolMXBeans();
    for (Iterator iter = pools.iterator(); iter.hasNext(); ) {
        MemoryPoolMXBean p = (MemoryPoolMXBean) iter.next();
        if (!pnames.contains(p.getName())) {
            throw new RuntimeException("GcInfo does not contain " +
                "memory usage for pool " + p.getName());
        }
    }
}
 

MemoryUsage getCollectMemoryUsage() {
    try {
        final Map<Object, Object> m = JvmContextFactory.getUserData();

        if (m != null) {
            final MemoryUsage cached = (MemoryUsage)
                m.get(entryCollectMemoryTag);
            if (cached != null) {
                if (log.isDebugOn())
                    log.debug("getCollectMemoryUsage",
                              entryCollectMemoryTag + " found in cache.");
                return cached;
            }

            MemoryUsage u = pool.getCollectionUsage();
            if (u == null) u = ZEROS;

            m.put(entryCollectMemoryTag,u);
            return u;
        }
        // Should never come here.
        // Log error!
        log.trace("getCollectMemoryUsage",
                  "ERROR: should never come here!");
        return ZEROS;
    } catch (RuntimeException x) {
        log.trace("getPeakMemoryUsage",
              "Failed to get MemoryUsage: " + x);
        log.debug("getPeakMemoryUsage",x);
        throw x;
    }

}
 

public long getEdenCommitted()
  throws JMException
{
  CompositeData data
    = (CompositeData) _mbeanServer.getAttribute(getEdenName(), "Usage");

  MemoryUsage usage = MemoryUsage.from(data);

  return usage.getCommitted();
}
 

MemoryUsage getPeakMemoryUsage() {
    try {
        final Map<Object, Object> m = JvmContextFactory.getUserData();

        if (m != null) {
            final MemoryUsage cached = (MemoryUsage)
                m.get(entryPeakMemoryTag);
            if (cached != null) {
                if (log.isDebugOn())
                    log.debug("getPeakMemoryUsage",
                          entryPeakMemoryTag + " found in cache.");
                return cached;
            }

            MemoryUsage u = pool.getPeakUsage();
            if (u == null) u = ZEROS;

            m.put(entryPeakMemoryTag,u);
            return u;
        }
        // Should never come here.
        // Log error!
        log.trace("getPeakMemoryUsage", "ERROR: should never come here!");
        return ZEROS;
    } catch (RuntimeException x) {
        log.trace("getPeakMemoryUsage",
              "Failed to get MemoryUsage: " + x);
        log.debug("getPeakMemoryUsage",x);
        throw x;
    }

}
 

/** monitor GC, and should the heap grow above 80% usage, clear some strong references */
 protected void installGCMonitoring() {
  System.out.println("ReferenceManager.installGCMonitoring");
  Set<String> ignoredMemoryAreas = new HashSet<>(Arrays.asList("Code Cache", "Compressed Class Space", "Metaspace"));

  List<GarbageCollectorMXBean> gcbeans = java.lang.management.ManagementFactory.getGarbageCollectorMXBeans();
  for (GarbageCollectorMXBean gcbean : gcbeans) {
    NotificationListener listener = (notification, handback) -> {
      if (notification.getType().equals(GarbageCollectionNotificationInfo.GARBAGE_COLLECTION_NOTIFICATION)) {
        GarbageCollectionNotificationInfo info = GarbageCollectionNotificationInfo.from((CompositeData) notification.getUserData());

        //sum up used and max memory across relevant memory areas
        long totalMemUsed = 0;
        long totalMemMax = 0;
        for (Map.Entry<String, MemoryUsage> entry : info.getGcInfo().getMemoryUsageAfterGc().entrySet()) {
          String name = entry.getKey();
          if (!ignoredMemoryAreas.contains(name)) {
            MemoryUsage detail = entry.getValue();
            totalMemUsed += detail.getUsed();
            totalMemMax += detail.getMax();
          }
        }
        float heapUsageBefore = (float) totalMemUsed / (float) totalMemMax;
        if (heapUsageBefore > 0.8) { //TODO make configurable
          System.out.println("heap usage (after GC) is " + heapUsageBefore + ", clearing some references");
          clearReferences();
        }
      }
    };
    NotificationEmitter emitter = (NotificationEmitter) gcbean;
    emitter.addNotificationListener(listener, null, null);
  }
}