Find native memory leak in Java application using

Question

Currently I am trying to resolve a Java memory issue: My Java application keeps using more and more memory and eventually it gets killed by the Linux OOM killer.

There is probably a Native Memory leak, because after inspection of the JVM with VisualVM both metaspace and the heap look OK.

Using the top command I can see that the memory used by the JVM keeps on increasing.

The first graphic in this article:

Example #1

Is a perfect match of what I am seeing in my own application.

So I tried using JeMalloc to find the leak as described in various articles. Here I run into a problem: When using the jeprof command and later the top command in jeprof itself, it does show the functions that use the most memory, but these are in hexadecimal addresses, so I must be missing some symbols. But I do not know which packages I need for that, that is unknown to me.

I already found this link: Link #1

And installed this package: debuginfo-install java-1.8.0-openjdk

I tried to work through simple steps first:

Get JeMalloc to work with a simple application, such as w. Next get it to work with java -version. So far so good, I can also get PDF's from JeMalloc with a perfect overview.

Next get it to work with java -jar simpletest.jar << Here I am missing symbols For example, if I do not close a GZipInputStream here, that does not show up in the JeMalloc results.

Next get it to work with java -jar myapplication.jar << Here I am missing symbols as well.

So my question is basically: What packages do I need in order to get JeMalloc to display all symbol-names to debug applications such as:

public void test1() {
    InputStream fileInputStream = null;
    GZipInputStream gzipInputStream = null;

    try {
      fileInputStream = new FileInputStream("test.zip");
      gzipInputStream = new GZIPInputStream(fileInputStream);

      int data = gzipInputStream.read();
      while (data != -1) {
        // do something with data
        data = gzipInputStream.read();
      }

    } catch (Exception ex) {

    } finally {
      // Disabled to see whether JeMalloc can detect the leak
      /*try {
        if (gzipInputStream != null) {
          gzipInputStream.close();
        }
        if (fileInputStream != null) {
          fileInputStream.close();
        }

        gzipInputStream = null;
        fileInputStream = null;
      } catch (IOException e) {
      e.printStackTrace();
    }*/
  }
}

Using the following software:

• Linux CentOS 7
• JeMalloc
• OpenJDK

Articles found:

Article #1

Article #2

Article #3

Article #4

Answer 1

Replacing allocator (with jemalloc or tcmalloc for instances) to profile memory usage may provide hint about source of native memory leak but it is limited to native code symbols available in libraries loaded in JVM.

To have Java class/method in stack trace, it is required to generate a mapping file associating native code memory location with its origin. The only tool at time of writing is https://github.com/jvm-profiling-tools/perf-map-agent

To get more than only "interpreter" names in stack, the concerned code has to be JIT-compiled, so enforcing with -XX:CompileThreshold=1 on JVM command line options is interesting (except in production IMO).

When agent loaded in JVM, mapping file generated, and code JIT-compiled, perf can be used to report CPU profiling. Memory leak investigation requires more processing.

The best option is to get bcc and its memleak tool if your Linux kernel is 4.9 or upper: https://github.com/iovisor/bcc/blob/master/tools/memleak_example.txt

Many thanks to Brendan Gregg

Debian system gets ready after a simple apt install bcc, but RedHat system requires more work as documented for CentOS 7 at http://hydandata.org/installing-ebpf-tools-bcc-and-ply-on-centos-7 (it is even worse on CentOS 6)

As an alternative, perf only can also report leakage stack trace with specific probes. Scripts and example usage are available at https://github.com/dkogan/memory_leak_instrumentation but has to be adapted to Java context.