[cffi-devel] Re: Strange Performance Issue

[Luis Oliveira]

"Luís Oliveira" <luismbo at gmail.com> writes:
> I didn't do any profiling but I guess that extra overhead I described
> explains the time difference. I'm not sure what's consing 700M though.

A quick profiling session reveals CHECK-FOR-TYPEDEF-CYCLES is the
culprit, because it conses a fresh hashtable each time. This is called
by PARSE-TYPE, which in turn is called by MEM-[A]REF in that inner loop
in TEST-2.  That's 786432 new hashtables.

TEST-2 with PARSE-TYPE modified not to call CHECK-FOR-TYPEDEF-CYCLES:

CFFI> (time (test-2))
Evaluation took:
  11.782 seconds of real time
  5.285146 seconds of user run time
  0.307772 seconds of system run time
  [Run times include 0.145 seconds GC run time.]
  0 calls to %EVAL
  0 page faults and
  22,016,008 bytes consed.

I suppose it might be worthwhile to look into some way of optimizing
C-F-T-C.  This check can probably be done when the type is defined, at
least in some cases.

-- 
Luís Oliveira
http://student.dei.uc.pt/~lmoliv/