Java heap profiling between two events

Question

I want to gather the heap usage of a program. In particular from a specific start event up to an end event, and with a set interval for example every 10ms. I tried to implement something like this myself, which is the following code. It works for slow intervals, like 1second, but for lower intervals, like 100ms, it becomes buggy. Does the System.gc() method block all threads until it finishes? I'm currently assuming so.

public void startAsync()
{
    running = true;
    Thread thread = new Thread(new Runnable()
    {
        @Override
        public void run()
        {
            while (running)
            {
                measure();
                try
                {
                    Thread.sleep(wait);
                } catch (InterruptedException e)
                {
                    throw new RuntimeException();
                }
            }
        }
    });
    thread.start();
}

public void measure()
{
    MemoryMXBean memoryBean = ManagementFactory.getMemoryMXBean();
    memoryBean.gc();
    long currentTime = System.currentTimeMillis();
    MemoryUsage memoryUsage = memoryBean.getHeapMemoryUsage();
    writer.exec(currentTime - startTime, memoryUsage.getUsed());
}

Your measurement measures itself as well :) – khachik Dec 06 '10 at 15:26 — khachik, Dec 06 '10 at 15:26

skaffman · Answer 1 · 2010-12-06T15:34:56.940

2

The numbers returned by java.lang.Runtime are not worth much - ignore them.

You'll get better results from the Management API, e.g.

MemoryUsage memoryUsage = ManagementFactory.getMemoryMXBean().getMemoryUsage();

... and related methods, which will likely give you far more information than you ever wanted to know.

edited Dec 06 '10 at 15:34

answered Dec 06 '10 at 15:29

skaffman

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NPE · Answer 2 · 2010-12-06T16:14:32.437

2

YourKit is superb (no connection other than as a satisfied customer.)

edited Dec 06 '10 at 16:14

answered Dec 06 '10 at 15:34

NPE

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The evaluation license might be all you need to diagnose the problem. ;) – Peter Lawrey Dec 06 '10 at 16:13

score 1 · Answer 3 · edited Apr 01 '13 at 15:58

1

Instead of wasting the time in the command prompt, I suggest that you follow the accurate measurements provided by the NetBeans IDE.

edited Apr 01 '13 at 15:58

wchargin

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answered Jan 17 '13 at 06:33

SHRIKANT KALE

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score 0 · Answer 4 · answered Jan 17 '13 at 06:37

0

JProfiler is the best one for monitoring such issues.

answered Jan 17 '13 at 06:37

Ahmet Karakaya

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score 0 · Answer 5 · answered Dec 06 '10 at 19:18

0

You can do it from the command line with jmap -heap

http://download.oracle.com/javase/1.5.0/docs/tooldocs/share/jmap.html

1 line script to loop this every x seconds.

answered Dec 06 '10 at 19:18

bwawok

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Java heap profiling between two events

5 Answers5