[kramdown-users] Performance optimizations

[Thomas Leitner]

Hi everybody,

there was a major performance drop in the 0.11.0 version of kramdown
due to the preservation of the ordering of the element attributes.

I did some investigations and found that turning off the garbage
collector makes kramdown run much faster. So it seems that kramdown
creates too much objects and the garbage collector has to do too much.
After some tweaking the performance of the next release should be much
better again. Also, 15% less objects are created in comparison with the
0.11.0 release.

Here are some performance numbers for various kramdown versions on
different ruby versions. All benchmarks are run on an Intel Core i5
M520 with 4GB memory on Ubuntu 10.10 with 64bit. The data is generated
with the new `benchmark/benchmark.sh` script. You can reproduce the
data by cloning the git repository and running

    bash benchmark/benchmark.sh -k "REL_0_1_0 REL_0_6_0 REL_0_9_0 REL_0_10_0 REL_0_11_0 master"

The generated data can be found in /tmp/kramdown-benchmark. By default
all tags and the master version are used for the kramdown versions if
not overridden with the `-k` option. The script uses rvm to switch
between ruby versions, so you need that too! You will also need gnuplot
so that the images can be generated.

jruby-1.5.0RC1
#       REL_0_1_0 ||  REL_0_6_0 ||  REL_0_9_0 || REL_0_10_0 || REL_0_11_0 ||     master
  1       0.23100       0.21300       0.24600       0.17700       0.18600       0.25500
  2       0.15100       0.23300       0.21500       0.21300       0.24600       0.21600
  4       0.17200       0.17400       0.19600       0.18700       0.33900       0.23600
  8       0.29300       0.28600       0.31200       0.29600       0.37600       0.31800
 16       0.37400       0.35600       0.52100       0.50500       0.42200       0.45600
 32       0.59000       0.55700       0.59900       0.59900       0.70300       0.64900

ruby 1.8.5-p231
#       REL_0_6_0 ||  REL_0_9_0 || REL_0_10_0 || REL_0_11_0 ||     master
  1       0.01000       0.01051       0.01136       0.01195       0.01175
  2       0.02109       0.02174       0.02119       0.02277       0.02039
  4       0.03730       0.04732       0.04732       0.04573       0.04850
  8       0.09734       0.08701       0.08335       0.11130       0.08702
 16       0.18256       0.20505       0.19535       0.23545       0.20143
 32       0.41248       0.44407       0.46074       0.49541       0.46472

ruby 1.8.6-p399
#       REL_0_1_0 ||  REL_0_6_0 ||  REL_0_9_0 || REL_0_10_0 || REL_0_11_0 ||     master
  1       0.01241       0.01014       0.01191       0.01134       0.01222       0.01117
  2       0.01608       0.02513       0.02176       0.02733       0.02321       0.02155
  4       0.03024       0.03929       0.04743       0.04753       0.04654       0.04751
  8       0.06593       0.07937       0.08792       0.08623       0.09291       0.08353
 16       0.13082       0.17244       0.19194       0.18539       0.22715       0.18366
 32       0.27855       0.38740       0.42560       0.42649       0.47899       0.49377

ruby 1.8.7-p249
#       REL_0_1_0 ||  REL_0_6_0 ||  REL_0_9_0 || REL_0_10_0 || REL_0_11_0 ||     master
  1       0.00895       0.01051       0.01264       0.01274       0.01242       0.01141
  2       0.01722       0.02107       0.02299       0.02229       0.02382       0.02318
  4       0.03070       0.04586       0.04909       0.04872       0.04764       0.04919
  8       0.06811       0.08272       0.09249       0.09098       0.11013       0.08745
 16       0.16567       0.17962       0.19554       0.18920       0.22599       0.18849
 32       0.28729       0.39177       0.53765       0.44901       0.49453       0.39598

ruby 1.8.7-p302
#       REL_0_1_0 ||  REL_0_6_0 ||  REL_0_9_0 || REL_0_10_0 || REL_0_11_0 ||     master
  1       0.00966       0.01171       0.01291       0.01286       0.01387       0.01261
  2       0.01778       0.02483       0.02535       0.02476       0.03128       0.02728
  4       0.03422       0.05098       0.05400       0.05377       0.05474       0.05435
  8       0.07529       0.09204       0.09825       0.09899       0.12087       0.09575
 16       0.18189       0.19847       0.21057       0.25462       0.24744       0.20743
 32       0.31704       0.43067       0.51242       0.51385       0.53427       0.44922

ruby 1.9.2-p0
#       REL_0_1_0 ||  REL_0_6_0 ||  REL_0_9_0 || REL_0_10_0 || REL_0_11_0 ||     master
  1       0.01357       0.00870       0.00934       0.00935       0.01056       0.00968
  2       0.02199       0.01758       0.01957       0.01947       0.02030       0.01938
  4       0.04581       0.03701       0.04082       0.04215       0.04545       0.04122
  8       0.09261       0.07473       0.08601       0.08608       0.08778       0.08847
 16       0.18589       0.14448       0.15985       0.16125       0.18634       0.15448
 32       0.38448       0.31029       0.35264       0.35203       0.37317       0.34102

-- Thomas