Next performance fix: Builder::XChar
Posted by Nick Sieger Thu, 17 Jan 2008 23:48:00 GMT
Next up in our performance series: Builder::XChar. (Another fine Sam Ruby production!) While this piece of code in the Builder library strikes me as perfectly fine, it also tends to slow down quite a bit with larger documents or chunks of text.
Our path to the bottleneck is as follows: ActiveRecord::Base#to_xml => Builder::XMLMarkup#text! => String#to_xs => Fixnum#xchr. Consider:
require 'rubygems'
gem 'activesupport'
require 'active_support'
require 'benchmark'
module Benchmark
class << self
def report(&block)
n = 10
times = (1..10).map do
bm = measure(&block)
puts bm
bm
end
sum = times.inject(0) {|s,t| s + t.real}
mean = sum / n
sumsq = times.inject(0) {|s,t| s + t.real * t.real}
sd = Math.sqrt((sumsq - (sum * sum / n)) / (n - 1))
puts("Mean: %0.6f SDev: %0.6f" % [mean, sd])
end
end
end
# http://blog.nicksieger.com/files/page.xml
page = File.open("page.xml") {|f| f.read }
Benchmark.report do
20.times { page.to_xs }
endOn Ruby and JRuby, this produces:
$ ruby to_xs.rb
21.430000 0.400000 21.830000 ( 22.022769)
21.530000 0.360000 21.890000 ( 22.005737)
21.540000 0.370000 21.910000 ( 22.065165)
21.530000 0.370000 21.900000 ( 22.028591)
21.500000 0.350000 21.850000 ( 21.990395)
21.550000 0.370000 21.920000 ( 22.033164)
21.520000 0.360000 21.880000 ( 21.984129)
21.550000 0.370000 21.920000 ( 22.116802)
21.550000 0.370000 21.920000 ( 22.051421)
21.520000 0.380000 21.900000 ( 22.084736)
Mean: 22.038291 SDev: 0.041985
$ jruby -J-server to_xs.rb
79.112000 0.000000 79.112000 ( 79.112000)
81.480000 0.000000 81.480000 ( 81.481000)
84.745000 0.000000 84.745000 ( 84.745000)
84.384000 0.000000 84.384000 ( 84.384000)
121.933000 0.000000 121.933000 (121.933000)
85.533000 0.000000 85.533000 ( 85.532000)
82.762000 0.000000 82.762000 ( 82.763000)
82.090000 0.000000 82.090000 ( 82.090000)
81.298000 0.000000 81.298000 ( 81.299000)
80.774000 0.000000 80.774000 ( 80.773000)
Mean: 86.411200 SDev: 12.635700
(Hmm, I must have accidentally swapped in some large program in the middle of that JRuby run. The perils of benchmarking on a desktop machine. I don’t claim that the numbers are scientific, just illustrative!)
Fortunately, the fix again is very simple, and has previously been acknowledged. The latest (unreleased?) Hpricot has a new native extension, fast_xs, which is an almost drop-in replacement for the pure-ruby String#to_xs. (Almost, because it creates the method String#fast_xs instead of String#to_xs. ActiveSupport 2.0.2 and later take care of aliasing it for you). Unbeknownst to me, I ported fast_xs recently as part of upgrading JRuby extensions that have Java code in them. And so it happens to come in handy at this time. The patch for that is here.
I have the latest Hpricot gems on my server, so you can install it yourself (for either Ruby or JRuby):
gem install hpricot --source http://caldersphere.net
or
jruby -S gem install hpricot --source http://caldersphere.net
With that installed, the script now produces these results:
$ ruby to_xs.rb
0.460000 0.080000 0.540000 ( 0.537793)
0.420000 0.070000 0.490000 ( 0.501965)
0.430000 0.070000 0.500000 ( 0.501359)
0.400000 0.070000 0.470000 ( 0.484495)
0.400000 0.070000 0.470000 ( 0.479995)
0.400000 0.070000 0.470000 ( 0.469118)
0.390000 0.070000 0.460000 ( 0.468864)
0.390000 0.070000 0.460000 ( 0.465009)
0.390000 0.060000 0.450000 ( 0.452902)
0.390000 0.070000 0.460000 ( 0.466881)
Mean: 0.482838 SDev: 0.024926
$ jruby -J-server to_xs.rb
0.882000 0.000000 0.882000 ( 0.883000)
0.832000 0.000000 0.832000 ( 0.832000)
0.851000 0.000000 0.851000 ( 0.850000)
0.837000 0.000000 0.837000 ( 0.837000)
0.846000 0.000000 0.846000 ( 0.846000)
0.843000 0.000000 0.843000 ( 0.843000)
0.835000 0.000000 0.835000 ( 0.835000)
0.825000 0.000000 0.825000 ( 0.826000)
0.830000 0.000000 0.830000 ( 0.830000)
0.834000 0.000000 0.834000 ( 0.833000)
Mean: 0.841500 SDev: 0.016379
