I used the following code to benchmark, in an attempt to reduce the comparison solely to the actual printf calls:

use warnings;
use Benchmark qw(cmpthese);
open OUTF, '>', '/dev/null' or die "/dev/null: $!\n";
cmpthese(0, {
  perlprint => q{
    for my $j (0 .. 255) {
      printf OUTF "host DAAA%02X { blah blah XX:XX:XX:%02X; }\n", $j, 
+$j;
    }   
  },
  Cprint => q{
    for my $j (0 .. 255) {
      C_print(*OUTF, $j);
    }
  },
});

use Inline 'C' => <<INLINE;
void C_print(FILE *fp, int j) {
  fprintf(fp, "host DAAA%02X { blah blah XX:XX:XX:%02X; }\n", j, j);
}
INLINE

[download]

This consistently reported the C code as being about twice as fast as the perl code (on my perl-5.8.5 installation), which seems about reasonable to me given all the extra layers of indirection the perl code has to wade through.

One of the differences between perl-5.6.x and perl-5.8.x is that the 'perlio' abstraction is now the default, and with perlio enabled we get to take advantage of some of the lower-level I/O mechanisms available to the C library fprintf. It is possible that switching to a perl built with 'perlio' will get you a factor closer to this - check for "perlio=define" in the perl -V output.

Hugo

In reply to Re: perl printf vs C fprintf performance by hv
in thread perl printf vs C fprintf performance by decnartne

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