Java memory benchmark

Question

I'm currently developing own pet project in Java which consist of custom data structures. To measure performance I chose Google Caliper framework, but to measure memory usage of data structure I should each time measure it using VisuamVm (dump heap and wait for calculation of object retained size), to get valid results. I want to make some kind of "memory benchmark" tests.

So, the question is:

Is there any Java framework similar to Caliper or JunitBenchmarks that allows to make tests to measure memory consumption of my data structures?

score 2 · Accepted Answer · edited May 23 '17 at 12:31

This tool is appropriate for you. Open JDK - Java Object Layout

Sample examining HashMap

$ java -jar jol-cli/target/jol-internals.jar java.util.HashMap
  Running 64-bit HotSpot VM.
  Using compressed references with 3-bit shift.
  Objects are 8 bytes aligned.
  Field sizes by type: 4, 1, 1, 2, 2, 4, 4, 8, 8 [bytes]
  Array element sizes: 4, 1, 1, 2, 2, 4, 4, 8, 8 [bytes]

  java.util.HashMap object internals:
   OFFSET  SIZE       TYPE DESCRIPTION                    VALUE
    0     4            (object header)                01 00 00 00 (00000001 00000000    00000000 00000000)
    4     4            (object header)                00 00 00 00 (00000000 00000000 00000000 00000000)
    8     4            (object header)                0f 0f 3e e0 (00001111 00001111 00111110 11100000)
   12     4        Set AbstractMap.keySet             null
   16     4 Collection AbstractMap.values             null
   20     4        int HashMap.size                   0
   24     4        int HashMap.threshold              16
   28     4      float HashMap.loadFactor             0.75
   32     4        int HashMap.modCount               0
   36     4        int HashMap.hashSeed               0
   40     4    Entry[] HashMap.table                  []
   44     4        Set HashMap.entrySet               null
   Instance size: 48 bytes (estimated, add this JAR via -javaagent: to get accurate result)
   Space losses: 0 bytes internal + 0 bytes external = 0 bytes total

score 0 · Answer 2 · answered Mar 10 '14 at 14:35

0

While I don't know of a library for that, there are better approaches than taking a heap dump to mesaure memory use: You can ask the JVM to perform a garbace collection with System.gc(), and then query heap usage with Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory() .

answered Mar 10 '14 at 14:35

meriton

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Thanks, but as far as I known this isn't best way to measure object accurate size. – Ivan Kurchenko Mar 10 '14 at 14:53
Why not? And do you want to measure object size, or find the heap memory usage contribution of an entire object graph? That's not the same ... – meriton Mar 10 '14 at 14:57
I need retained size of my object. When I analyzed heap using VisuamVm i find a lot of objects, that was created not from my tests program (I run it from IntelliJ) and as I understood there is a possibility to get invalid results using Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory(). – Ivan Kurchenko Mar 10 '14 at 15:07

QJGui · Answer 3 · 2014-03-11T02:36:31.880

Memory benchmark contains two points: throughput and fragment. Here I think what you want to do is choose what's the better data structure for these environment. For this point, I think you also need these two points to measure.

Here you can use OQL(Object query language) to query this datastructure usage. You can use hprof and MAT to analysis your system's heap context.

To solve your the question that making tests to measure the memory consumption, I suggest these steps:

Create a productive environment
Run the program
In the important point, you can dump your heap Use JMX to make HPROF heap dumps right before and after a full GC
Use MAT, VisualVM to analysis the hprof

Thanks! Can you please recommend some articles about throughput and fragment in context of memory in Java ? I've never heard about this terms before. — Ivan Kurchenko, Mar 10 '14 at 14:58

Java memory benchmark

3 Answers3