Measuring Java execution time, memory usage and cpu load for a code segment

Question

For a particular segment of Java code, I'd like to measure:

• execution time (most likely thread execution time)
• memory usage
• CPU load (specifically attributable to the code segment)

I'm a relative Java novice and am not familiar with how this might be achieved. I've been referred to JMX, however I'm not sure how that might be used, and JMX looks a bit 'heavy' for what I'm looking to do.

Ideally I'd like some measurement class that can be told what I would like to measure, with the option of calling a start() method prior to a code segment and a stop() method after. Relevant metrics would be logged to a file I specify.

For example:

import com.example.metricLogger;

metricLogger logger = new metricLogger();

logger.setLogPath(pathToLogFile);
logger.monitor(executionTime);
logger.monitor(memoryUsage);
logger.monitor(cpuLoad);

logger.start();

/* Code to be measured */

logger.stop();

Is there any standard/common/conventional way of achieving this in Java?

Such measurements are for one-off performance comparisons and so I'm not looking for any in-production long-term monitoring processes.

I'm more than happy to be referred to tutorials or external examples and don't expect a full answer here. That said, if anything as simple as the above can be achieved a realistic example would go down really well.

Answer 1

Profiling may be an easier option since you don't require in-production stats. Profiling also doesn't require code modification. VisualVM (which ships w/ the JDK 1.6.06+) is a simple tool. If you want something more in-depth I'd go w/ Eclipse TPTP, Netbeans profiler, or JProfiler(pay).

If you want to write you own, consider the following:

Simple measurments like execution time can be done by "clocking" the section you're interested in:

long start = System.nanoTime(); // requires java 1.5
// Segment to monitor
double elapsedTimeInSec = (System.nanoTime() - start) * 1.0e-9;

You can use a similar technique to monitor memory via Runtime.getRuntime().*memory() methods. Keep in mind that tracking memory usage in a garbage collected environment is trickier simple subtraction.

CPU load is hard to measure in Java, I typically stick w/ execution time and optimize the longer / repetitive sections

Answer 2

Using a Java Profiler is the best option and it will give you all the insight that you need into the code. viz Response Times, Thread CallTraces, Memory Utilisations, etc

I will suggest you JENSOR, an open source Java Profiler, for its ease-of-use and no overheads on CPU. You can download it, instrument the code and will get all the info you need about your code.

You can download it from: http://jensor.sourceforge.net/

Answer 3

With the ThreadMXBean you can get CPU usage of individual threads and cpu time consumed rather than elapse time which may be useful.

However, its often simpler to use a profiler as this process often generates a lot of data and you need a good visualisation tool to see what is going on.

I use Yourkit as I find it easier to solve problems that other profilers I have used. I also use the builtin hprof as this can give you a different view on the profile of your application (but not as useful)