[erlang-questions] fprof unusable?

Scott Lystig Fritchie <>
Sat Aug 23 01:04:43 CEST 2008


Joel Reymont <> wrote:

jr> Any suggestions on how to proceed other than shortening the
jr> profiling session?

Joel, I haven't had much luck with using fprof for 100%-CPU-eating
workloads for more than 30-60 seconds.  In versions up through R11B-5,
occasionally I see fprof:analyse() crash after chugging through some
fraction of the trace file.  {shrug}  I haven't used R12B-* enough to
say anything useful.

Even R12B releases are going to create gigantic trace files like that if
you run for a couple of days, it's the nature of the fprof beast, as far
as I know.

I very frequently use eprof or even cprof first, to get an idea of where
to start looking, then try to devise a short (time-wise) and small (# of
Erlang processes-wise) that ought to do the same thing, then use fprof
on that.  The problem is that the "try to devise..." step isn't always
feasible, but that's a case-by-case thing.  {shrug}

-Scott



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