From: Yusuke Endoh <redmine@...>
Date: 2010-04-09T22:19:38+09:00
Subject: [ruby-core:29382] [Bug #1544](Feedback) rb_io_write bug?

Issue #1544 has been updated by Yusuke Endoh.

Status changed from Open to Feedback

Hi,

2009/5/31 Brian Lopez <redmine@ruby-lang.org>:
> I'm using rb_io_write to write (in C) to a StringIO instance (which was defined in Ruby, and passed to my C code) and noticed some strange behavior.
> I'm writing to the IO at the beginning of a recursively called method and under 1.9.1 it's *really* slow unless I buffer up the contents then only write to the IO once using rb_io_write. For what I'm doing it's the difference between completing in 3.3 seconds, vs 0.13 seconds.
> Under 1.8.6 I can write to the IO using rb_io_write in the smaller chunks (on ever recursive call) and it performs similar to the buffered write in 1.9.1.

I failed to reproduce with RubyInline, 1.8.8dev and trunk.


  require "rubygems"
  require "inline"
  require "stringio"
  require "benchmark"

  class Test
    inline do |builder|
     builder.c <<-EOF
        VALUE test(VALUE io, VALUE str, VALUE num) {
          int i = NUM2INT(num);;
          while (i--) {
            rb_io_write(io, str);
          }
          return Qnil;
        }
      EOF
    end
  end

  str = "foobar"
  N = 100_000
  Benchmark.bm do |bm|
    test = Test.new
    io = StringIO.new("")
    bm.report("1") { test.test(io, str, N) }
    io = StringIO.new("")
    bm.report("2") { test.test(io, str * N, 1) }
  end



  $ ../ruby-trunk-local/bin/ruby -v test.rb
  ruby 1.9.2dev (2010-04-09 trunk 27269) [i686-linux]
        user     system      total        real
  1  0.020000   0.000000   0.020000 (  0.019992)
  2  0.010000   0.000000   0.010000 (  0.001042)

  $ ruby18 -v test.rb
  ruby 1.8.8dev (2010-04-08) [i686-linux]
        user     system      total        real
  1  0.020000   0.000000   0.020000 (  0.020884)
  2  0.000000   0.000000   0.000000 (  0.001030)


I tried various parameters of string length and loop count,
but I cannot reproduce the phenomenon you said.
I admit the condition will be very different from yours,
though.


2009/6/30 Brian Lopez <redmine@ruby-lang.org>:
> Anyway, the code is in my yajl-ruby project. Specifically, if you look here: http://github.com/brianmario/yajl-ruby/blob/866e58ed553083e079ed5797eb5a6256dd6ce2d3/ext/yajl_ext.c#L74
> That line is the call to rb_io_write that I was talking about. You'll notice I have it only call rb_io_write if the write buffer size is equal or surpassed the WRITE_BUFSIZE constants value (defaults to 8kb).
>
> Previously, I wasn't doing that buffer size check and just calling rb_io_write on every call of the yajl_encode_part function (which is called recursively. That's how I surfaced the issue.

We are not familiar with yajl at all.  Please show us the
smaller code to reproduce, or at least, tell us the process
to reproduce with yajl...

I can't help but close this ticket unless you answer.

-- 
Yusuke ENDOH <mame@tsg.ne.jp>
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