[erlang-questions] fprof doubts

Raimo Niskanen <>
Wed Sep 3 11:32:23 CEST 2008

On Wed, Sep 03, 2008 at 01:55:31PM +0530, Geevarghese Philip wrote:
> Hi,
> I used fprof to profile my code. I got an analysis report, but I am confused
> about a couple of things in the report:
>    a) There is not much information about /my/ functions in the report : it
> is mostly about the underlying Erlang library functions. While I expect that
> most of the work is done by the libraries, my own functions are the gateways
> (so to speak) to these library functions, so they should appear in the
> profile with large ACC numbers against them, but this doesn't happen.
> Wherever my functions appear, they have very small numbers against them, and
> only in /two/ places do they occur with a % against them -- which indicates
> that the information is about calls to these functions.
> b) I checked every instance in the report where the module name is "graphs"
> (my module). Everywhere the function reported is a fun. Why isn't the parent
> function reported at all?
> c) In nearly every block of information, there is an entry named "undefined"
> with large numbers against it. What does this mean?

Can you give an example?
'undefined' is an unknown or undefined function.
E.g when you spawn a new process the caller of the
first function is 'undefined'.

> Could these be because I have not invoked/named my functions in some
> specified manner?

Yes, probably. How _did_ you trace?

	fprof:apply(graph, func, [arg])
	%wait a while
on a running system hoping to catch something interesting,


> Thanks,
> Philip

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/ Raimo Niskanen, Erlang/OTP, Ericsson AB

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