Can I generate an HPROF file at will?

Question

I have a java process which is acting dubiously. I'd like to see what's up using the various HPROF analysis tools.

How do I generate one on the fly?

Answer 1

You have to start the Java process with the correct arguments, which vary a little depending on the JVM version. Then, send a QUIT signal to the process to generate a new file.

The output is normally generated when the VM exits, although this can be disabled by setting the “dump on exit” option to “n” (doe=n). In addition, a profile is generated when Ctrl-\ or Ctrl-Break (depending on platform) is pressed. On Solaris OS and Linux a profile is also generated when a QUIT signal is received (kill -QUIT pid). If Ctrl-\ or Ctrl-Break is pressed multiple times, multiple profiles are generated to the one file.

Answer 2

VisualVM can help you dig into what your process is doing, including the ability to arbitrarily force a heap dump on a running process.

Answer 3

You can generate an hprof file on the fly using the jmap tool, which ships with Sun's Java VM:

jmap -dump:file=<file_name> <pid>