From: Bil Kleb <W.L.Kleb@...>
Date: 2001-08-18T12:58:31+09:00
Subject: [ruby-talk:19964] Slow file I/O? (newbie)

So we were trying to test the speed of mirrored versus non-mirrored
disks and decided to use Ruby to do the testing.  We wrote a couple
one-liners to write and read a Gigabyte-sized file of all 1's, viz,

 File.open("testFile","w") { |f| (2**30).times{f.putc "1"} }

and

 File.open("testFile") { |f| (2**30).times{f.getc} }

but we found the writing was so slow that we abandoned all hope
before we even got around to the reading part...

We tried setting a variable instead of using "1", but it didn't
noticeably alter the speed.

What are we doing wrong?

(We're running Ruby 1.6.4 on Pentium II's and III's via GNU/Linux.)

For a MB file, i.e., 2**20, ruby -r profile testw.rb gives:

  %   cumulative   self              self     total
 time   seconds   seconds    calls  ms/call  ms/call  name
 77.74   189.94    189.94        1 189940.00 244320.00  Fixnum#times
 22.26   244.32     54.38  1048576     0.05     0.05  IO#putc
  0.00   244.32      0.00        1     0.00 244320.00  File#open
  0.00   244.32      0.00        1     0.00     0.00  Fixnum#<
  0.00   244.32      0.00        1     0.00     0.00  Fixnum#**
  0.00   244.32      0.00        1     0.00 244320.00  #toplevel

(BTW: it only takes 3 seconds without the profiling.)

The comparable c routine runs several orders of magnitude faster:

#include <stdio.h>
#include <math.h>
int main(){
  FILE *outfile= fopen("ctestFile","w");
  unsigned int i;
  for (i=0; i<pow(2,30); ++i) fputc('1',outfile);
  return 0;
}

Thanks in advance,
--
bil <http://abweb.larc.nasa.gov/~kleb/>