Java Garbage Collection Time?

Question

I have a very performance sensitive application in Java. (I know I should actually use C or something else. But it's Java now.) I'm trying to avoid creating and throwing away objects. Now I need to know how much garbage collecting is going on still.

How can I find out ?

If possible I would like to have a sort of number in milliseconds or nanoseconds something that doesn't require installation of more software.

Solution 1

Or you can let JVM print the GC activity.. These settings I have:

-verbose:gc -XX:+PrintGCTimeStamps -XX:+PrintGCDetails -XX:+PrintTenuringDistribution -Xloggc:logs/gc.log

GC activity is printed to a file logs/gc.log..

Solution 2

You can use tools like VisualVM to monitor application activity. Make sure you are using appropriate GC alogorithms.

Oracle JVM provides multiple types of Garbage Collectors:

• The throughput collector
• The concurrent low pause collector
• The incremental (sometimes called train) low pause collector:

Read more on these collectors here.

Solution 3

You can use VisualVm for this, it is exactly what you need.
As you can see below you have GC activity which is very useful:

Beside the GC Activity you have a lot of details there like : heap usage, cpu usage, object instances usage etc.

Solution 4

Jprofiler ,which Enables both memory profile to assess memory usage and dynamic allocation leaks and CPU profiling to assess thread conflicts.

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Comments

[Vishy]

+1 Note: for low GC programs, VisualVM will create more garbage than your application. For this I use YourKit, which is not free. I would start with VisualVM.

[Aaron]

There is also a plugin for VisualVM called VisualGC which shows what is happening for each heap space in real time. blogs.oracle.com/klc/entry/visualgc_plugin_for_visualvm