"Unable to open '... (autosplit into ...)'"¶

The profiled application executed code in a module that used AutoLoader to load the code from a separate .al file. NYTProf automatically recognises this situation and tries to determine the 'parent' module file so it can associate the profile data with it. In order to do that the parent module file must already be 'known' to NYTProf, typically by already having some code profiled.

You're only likely to see this warning if you're using the "start" option to start profiling after compile-time. The effect is that times spent in autoloaded subs won't be associated with the parent module file and you won't get annotated reports for them.

You can avoid this by using the default "start=begin" option, or by ensuring you execute some non-autoloaded code in the parent module, while the profiler is running, before an autoloaded sub is called.

Background¶

Subroutine-level profilers:

  Devel::DProf        | 1995-10-31 | ILYAZ
  Devel::AutoProfiler | 2002-04-07 | GSLONDON
  Devel::Profiler     | 2002-05-20 | SAMTREGAR
  Devel::Profile      | 2003-04-13 | JAW
  Devel::DProfLB      | 2006-05-11 | JAW
  Devel::WxProf       | 2008-04-14 | MKUTTER

Statement-level profilers:

  Devel::SmallProf    | 1997-07-30 | ASHTED
  Devel::FastProf     | 2005-09-20 | SALVA
  Devel::NYTProf      | 2008-03-04 | AKAPLAN
  Devel::Profit       | 2008-05-19 | LBROCARD

Devel::NYTProf is a (now distant) fork of Devel::FastProf, which was itself an evolution of Devel::SmallProf.

Adam Kaplan took Devel::FastProf and added html report generation (based on Devel::Cover) and a test suite - a tricky thing to do for a profiler. Meanwhile Tim Bunce had been extending Devel::FastProf to add novel per-sub and per-block timing, plus subroutine caller tracking.

When Devel::NYTProf was released Tim switched to working on Devel::NYTProf because the html report would be a good way to show the extra profile data, and the test suite made development much easier and safer.

Then he went a little crazy and added a slew of new features, in addition to per-sub and per-block timing and subroutine caller tracking. These included the 'opcode interception' method of profiling, ultra-fast and robust inclusive subroutine timing, doubling performance, plus major changes to html reporting to display all the extra profile call and timing data in richly annotated and cross-linked reports.

Steve Peters came on board along the way with patches for portability and to keep NYTProf working with the latest development Perl versions.

Adam's work is sponsored by The New York Times Co. <http://open.nytimes.com>. Tim's work was partly sponsored by Shopzilla. <http://www.shopzilla.com>.