I just added ruby 1.9 (svn rev 20317) to a simple xml processing 
benchmark I've created.

So far I've only tested rexml on ruby 1.9 but was surprised to find 
it about 13% slower than ruby 1.8.6.

In the benchmark (described below) ruby 1.9 took 9.793s while ruby 
1.8.6 took only 8.606s.

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I've updated my simple ruby xml benchmark which measures the time to 
open a 98k XML document and count one type of leaf element (466 
entries) 100 times.

   https://svn.concord.org/svn/projects/trunk/common/ruby/xml_benchmarks/

The summary is that for this one test using libxml in MRI 1.8.6 and 
jdom_document_builder (a native Java library) in JRuby take just 
about the same time. This is similar to the last time I ran these 
benchmarks.

However testing in REXML, 8 months JRuby was 41% slower than MRI 
1.8.6 while now it's about 35% faster.

Tests run on a MacBook Pro, Mac OS X 10.5.5, 4GB memory, 2.5 GHz 
Intel Core 2 Duo.

   hpricot 0.6.164
   libxml: 0.9.2

All benchmarks were run twice in sequence and the measurements 
presented here are from the second run. Java automatically optimizes 
JRuby code which is run many times and the speedup from the first to 
the second test is from 40 to 75%. There is no essential difference 
in the speed of the C version of Ruby between the first test and the 
second.

100 times: Open 98k XML document and count one type of leaf element 
(466 entries)

  time (s)   Ruby VM, version, XML library
-----------------------------------------------------------------------------------------
   0.360    JRuby (Java 1.6.0_03-p3-Soylatte using server mode): 
jdom_document_builder
   0.383    MRI 1.8.6 p114: libxml v0.9.2
   0.401    JRuby (Java 1.6.0_07): jdom_document_builder
   0.428    JRuby (Java 1.5.0_16): jdom_document_builder
   1.977    JRuby (Java 1.6.0_03-p3-Soylatte using server mode): hpricot
   2.027    JRuby (Java 1.5.0_16): hpricot
   2.094    JRuby (Java 1.6.0_07): hpricot
   2.140    MRI 1.8.6 p114: hpricot
   5.488    JRuby (Java 1.6.0_03-p3-Soylatte using server mode): rexml
   5.569    JRuby (Java 1.5.0_16): rexml
   5.578    JRuby (Java 1.5.0_16): rexml
   8.606    MRI 1.8.6 p114: rexml
   9.793    MRI Ruby 1.9 (svn rev 20317): rexml