From: Alex Fenton <alex@...>
Date: 2009-03-27T23:16:38+09:00
Subject: Re: Bug: Ruby 1.9.1 File io on Windows is slooooow

Damjan Rems wrote:
> This simple code shows everything:
> 
> time = [Time.new]
> c = ''
> 'aaaa'.upto('zzzz') {|e| c << e}
> 3.times { c << c }
> time << Time.new
> File.open('out.file','w') { |f| f.write(c) }
> time << Time.new
> c = File.open('out.file','r') { |f| f.read }
> time << Time.new
> 0.upto(time.size - 2) {|i| p "#{i} #{time[i+1]-time[i]}" }
> 
> ruby 1.9.1p0 (2009-01-30 revision 21907) [i386-mswin32]
> "0 0.537075"
> "1 0.696244"
> "2 40.188834"
> 
> ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32]
> "0 0.551"
> "1 0.133"
> "2 0.087"

I'm pretty sure from your other message that it's using Ruby 1.9 with 
UTF-8 encoded strings that kills performance. I get equivalent results 
on OS X comparing 1.8.6 to 1.9.1 on common string operations like 
String#[](a_fixnum).

It's understandable that correct character-wise operations are much 
harder for Ruby to implement efficiently on variable-byte-length 
encodings like UTF-8. Unfortunately, though I was delighted to get 
proper encoding support in 1.9, the performance hit on strings was a 
killer on my string-intensive GUI app.

There are sometimes ways round this (eg I rewrote diff/lcs to use string 
character enumerators rather than repeated expensive calls to String#[]).

I expect the Ruby team are already aware of the problem, and I hope this 
is a top priority for 1.9.2.

btw, you can report bugs at:
http://redmine.ruby-lang.org/

alex