The following blog entry will describe UNSUPPORTED <\/span><\/strong>functionality. This means that relying on the described APIs or functionality may BREAK <\/strong><\/span>your code\/plugin with any given update of the JDK and\/or Mission Control. <\/span><\/span><\/p>\n<\/blockquote>\n If you ever used JRockit, you may fondly remember the old jrcmd<\/font> utility, which now exists in a HotSpot incarnation as jcmd<\/font>. Well, jrcmd had an option, \u2013l, which would list all the the performance counters in the target JVM. The following code will let you implement something similar to the jrcmd \u2013l command. Note that the PerformanceCounter API resides in a package most IDEs will restrict access to. You will need to change your project settings accordingly for the following to compile. <\/p>\n Anyways, here is a hack to list all the performance counters for a particular PID:<\/p>\n import java.io.IOException; import sun.management.counter.Counter; public class PerfCounterTest { <\/font> <\/p>\n public static void main(String[] args) throws IOException { } Note that you will need the \u201csun.misc.Perf.getPerf\u201d permission to be able to access the Perf instance when running with a security manager.<\/p>\n From here to a fully functional Dynamic MBean, the step is pretty short.<\/p>\n Here is an example of how code exposing the Performance Counters as a Dynamic MBean can look like:<\/p>\n import java.io.IOException; import javax.management.Attribute; import sun.misc.Perf; public class PerfCounters implements DynamicMBean { static { public PerfCounters() { @Override @Override @Override @Override @Override @Override private static ObjectName createObjectName(String name) { private Map<String, Counter> setUpCounters() { private MBeanInfo createMBeanInfo() { And here is a little test application that registers the MBean with the platform MBean server and then waits around, giving you an opportunity to hook up with Mission Control and try it out: <\/p>\n import java.io.IOException; import javax.management.InstanceAlreadyExistsException; public class PerfCounterMBeanRunner { <\/font> <\/p>\n public static void main(String[] args) throws InstanceAlreadyExistsException, MBeanRegistrationException, NotCompliantMBeanException, IOException { }<\/font> <\/p>\n If you use the JMX Console to connect to a JVM where the PerfCounters MBean is registered, you should be able to find the PerfCounters MBean using the MBean Browser. There should be quite a few performance counters available:<\/p>\nPerformance Counter Hello World<\/h2>\n
import java.nio.ByteBuffer; <\/font> <\/p>\n
import sun.management.counter.perf.PerfInstrumentation;
import sun.misc.Perf; <\/font> <\/p>\n
if (args.length != 1) {
System.out.println(“Usage: PerfCounterTest <PID>”);
System.exit(2);
}
Perf p = Perf.getPerf();
ByteBuffer buffer = p.attach(Integer.parseInt(args[0]), “r”);
PerfInstrumentation perfInstrumentation = new PerfInstrumentation(buffer);
for (Counter counter : perfInstrumentation.getAllCounters()) {
System.out.println(String.format(
“%s = %s [Variability: %s, Units: %s]”, counter.getName(),
String.valueOf(counter.getValue()),
counter.getVariability(), counter.getUnits()));
} <\/font> <\/p>\n
}<\/font> <\/p>\nPerformanceCounterMBean \u00e1 la JRockit for HotSpot<\/h2>\n
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map; <\/font> <\/p>\n
import javax.management.AttributeList;
import javax.management.AttributeNotFoundException;
import javax.management.DynamicMBean;
import javax.management.InvalidAttributeValueException;
import javax.management.MBeanAttributeInfo;
import javax.management.MBeanException;
import javax.management.MBeanInfo;
import javax.management.MalformedObjectNameException;
import javax.management.ObjectName;
import javax.management.ReflectionException;
import javax.management.RuntimeOperationsException; <\/font> <\/p>\n
import sun.management.counter.Counter;
import sun.management.counter.perf.PerfInstrumentation; <\/font> <\/p>\n
public final static ObjectName MBEAN_OBJECT_NAME;
public final Map<String, Counter> counterMap;
private final MBeanInfo info; <\/font> <\/p>\n
MBEAN_OBJECT_NAME = createObjectName(“se.hirt.management:type=PerfCounters”);
} <\/font> <\/p>\n
counterMap = setUpCounters();
info = createMBeanInfo();
} <\/font> <\/p>\n
public Object getAttribute(String attribute)
throws AttributeNotFoundException, MBeanException,
ReflectionException {
if (attribute == null) {
throw new RuntimeOperationsException(new IllegalArgumentException(
“The attribute name cannot be null.”),
“Cannot invoke getAttribute on ” + MBEAN_OBJECT_NAME
+ ” with null as attribute name.”);
}
Counter c = counterMap.get(attribute);
if (c == null) {
throw new AttributeNotFoundException(
“Could not find the attribute ” + attribute);
}
return c.getValue();
} <\/font> <\/p>\n
public void setAttribute(Attribute attribute)
throws AttributeNotFoundException, InvalidAttributeValueException,
MBeanException, ReflectionException {
if (attribute == null) {
throw new RuntimeOperationsException(new IllegalArgumentException(
“The attribute name cannot be null.”),
“Cannot invoke setAttribute on ” + MBEAN_OBJECT_NAME
+ ” with null as attribute name.”);
}
Counter c = counterMap.get(attribute);
if (c == null) {
throw new AttributeNotFoundException(
“Could not find the attribute ” + attribute + “.”);
}
throw new RuntimeOperationsException(
new UnsupportedOperationException(),
“All attributes on the PerfCounters MBean are read only.”);
} <\/font> <\/p>\n
public AttributeList getAttributes(String[] attributes) {
AttributeList attributeList = new AttributeList();
for (String attribute : attributes) {
try {
attributeList.add(new Attribute(attribute,
getAttribute(attribute)));
} catch (AttributeNotFoundException | MBeanException
| ReflectionException e) {
\/\/ Seems this one is not supposed to throw exceptions. Try to
\/\/ get as many as possible.
}
}
return attributeList;
} <\/font> <\/p>\n
public AttributeList setAttributes(AttributeList attributes) {
\/\/ Seems this one is not supposed to throw exceptions.
\/\/ Just ignore.
return null;
} <\/font> <\/p>\n
public Object invoke(String actionName, Object[] params, String[] signature)
throws MBeanException, ReflectionException {
throw new MBeanException(new UnsupportedOperationException(
MBEAN_OBJECT_NAME + ” does not have any operations.”));
} <\/font> <\/p>\n
public MBeanInfo getMBeanInfo() {
return info;
} <\/font> <\/p>\n
try {
return new ObjectName(name);
} catch (MalformedObjectNameException e) {
\/\/ This will not happen – known to be wellformed.
e.printStackTrace();
}
return null;
} <\/font> <\/p>\n
Map<String, Counter> counters = new HashMap<>();
Perf p = Perf.getPerf();
try {
ByteBuffer buffer = p.attach(0, “r”);
PerfInstrumentation perfInstrumentation = new PerfInstrumentation(
buffer);
for (Counter counter : perfInstrumentation.getAllCounters()) {
counters.put(counter.getName(), counter);
}
} catch (IllegalArgumentException | IOException e) {
System.err.println(“Failed to access performance counters. No counters will be available!”);
e.printStackTrace();
}
return counters;
} <\/font> <\/p>\n
Collection<Counter> counters = counterMap.values();
List<MBeanAttributeInfo> attributes = new ArrayList<>(counters.size());
for (Counter c : counters) {
if (!c.isVector()) {
String typeName = “java.lang.String”;
synchronized (c) {
Object value = c.getValue();
if (value != null) {
typeName = value.getClass().getName();
}
}
attributes.add(new MBeanAttributeInfo(c.getName(), typeName,
String.format(“%s [%s,%s]”, c.getName(), c.getUnits(),
c.getVariability()), true, false, false));
}
}
MBeanAttributeInfo[] attributesArray = attributes.toArray(new MBeanAttributeInfo[attributes.size()]);
return new MBeanInfo(
this.getClass().getName(),
“An MBean exposing the available JVM Performance Counters as attributes.”,
attributesArray, null, null, null);
}
}<\/font> <\/p>\n
import java.lang.management.ManagementFactory; <\/font> <\/p>\n
import javax.management.MBeanRegistrationException;
import javax.management.NotCompliantMBeanException; <\/font> <\/p>\n
ManagementFactory.getPlatformMBeanServer().registerMBean(new PerfCounters(), PerfCounters.MBEAN_OBJECT_NAME);
System.out.println(“Press enter to quit!”);
System.in.read();
} <\/font> <\/p>\n
![\"JMC_perf_counters\"](\"https:\/\/hirt.se\/blog\/wp-content\/uploads\/2014\/02\/JMC_perf_counters.png\" "\\"JMC_perf_counters\\"")
<\/a> <\/p>\n