Add heap usage and measure gc activity

[kwsta]

I think it would beneficial to also understand the memory usage profile of each of the libraries.

I see you mention that isn't included in the README.md. Is it planned for the future?

[fabienrenaud]

It would definitely be beneficial but it's a complex thing to measure in Java since there are:

• many garbage collectors
• many JVMs (dalvik, JIT, HotSpot, versions)
• many different ways of tuning just a simple hotspot VM; and without tuning you'd need to wait for hours/days of intense activity before seeing the memory structure and usage stabilizing.

There is also no clear methodology on how one should do a memory benchmark in Java:
http://stackoverflow.com/questions/27831778/how-to-really-benchmark-the-memory-usage-of-a-java-application
Sure there is something in JMH but it seems hard to use/read/process: http://java-performance.info/introduction-jmh-profilers/

I'll try to think of something but these are the reasons why I haven't done it...
Any help is welcome. :)

[JanecekPetr]

Sure there is something in JMH but it seems hard to use/read/process: http://java-performance.info/introduction-jmh-profilers

The link is dead now, so I cannot see what it was saying. It should be fairly straightforward to see how much garbage got generated, this is mostly independent from JVM and/or Java version, and completely independent from the chosen GC.

Run with -prof gc and parse out the gc.alloc.rate.norm value: https://hg.openjdk.java.net/code-tools/jmh/file/523c524305e2/jmh-samples/src/main/java/org/openjdk/jmh/samples/JMHSample_35_Profilers.java#l170

[fabienrenaud]

If anyone wants to tackle this, the project is opened to contributions.