Mike Gran <spk121@yahoo.com> writes:

> I can't imagine any possible way that this patch could make
> performance worse, but, it is in the very core of the ports.
>  
> I don't think you can get away without at least a bit of
> profiling.

Fair enough.  First of all, this patch reduces the size of the built
libguile.so by about 42 kilobytes, and libguile.a by about 96 kilobytes.

As for performance: the updated patches (attached below) slows things
down by about one quarter of one percent on my machine.  The specific
benchmark I did was to call 'read-string' on an 11 megabyte ASCII text
file, with the port-encoding set to UTF-8.  In this case, all the reads
are done using 'scm_get_byte_or_eof' (called from 'get_utf8_codepoint').

So I think this is an acceptable cost for such a great reduction in code
size.  What do you think?

Thanks for nudging me to do the measurement.  To be honest, the original
patch I posted slowed things down by 4.5%, which I found extremely
surprising.  I fixed it by adding an internal 'static' version of
'scm_fill_input'.  So for those who doubt the cost of function calls
though the shared library PLT (which, within a shared library, is
*every* function call to a non-static function), let this be a lesson.
That's the only thing that changed here, and it made more than a 4%
difference, even though the procedure call in question was done only
once per 4 kilobyte buffer!

Here's the raw data:

before:
   12767060  libguile-2.0.a
    6999271  libguile-2.0.so.22.6.0

after:
   12671162  libguile-2.0.a          (96 kbytes smaller)
    6956989  libguile-2.0.so.22.6.0  (42 kbytes smaller)

test file (the contents of 'psyntax.scm' repeated many times):
-rw-r--r-- 1 mhw mhw 11503780 Apr  2 12:46 /home/mhw/BIG-FILE

before:
scheme@(guile-user)> ,time (define s (call-with-input-file "/home/mhw/BIG-FILE" read-string))
;; 2.953214s real time, 2.951423s run time.  0.027767s spent in GC.
scheme@(guile-user)> ,time (define s (call-with-input-file "/home/mhw/BIG-FILE" read-string))
;; 2.942170s real time, 2.940581s run time.  0.011873s spent in GC.
scheme@(guile-user)> ,time (define s (call-with-input-file "/home/mhw/BIG-FILE" read-string))
;; 2.954309s real time, 2.950164s run time.  0.011952s spent in GC.
avg: 2.9473893333333336

after:
scheme@(guile-user)> ,time (define s (call-with-input-file "/home/mhw/BIG-FILE" read-string))
;; 2.964777s real time, 2.957597s run time.  0.012116s spent in GC.
scheme@(guile-user)> ,time (define s (call-with-input-file "/home/mhw/BIG-FILE" read-string))
;; 2.971099s real time, 2.968656s run time.  0.012020s spent in GC.
scheme@(guile-user)> ,time (define s (call-with-input-file "/home/mhw/BIG-FILE" read-string))
;; 2.942377s real time, 2.940015s run time.  0.012085s spent in GC.
avg: 2.9554226666666663

0.27% slower

I've attached the new patches.  Okay to push now?

   Thanks,
     Mark