[jdom-interest] JDOM2 and Performance.

Rolf jdom at tuis.net
Sat Oct 15 15:17:33 PDT 2011

Hi all.

I've come close to restoring the JDOM 1.1.2 levels of performance.

When 'fixing' code in JDOM2 I cam accross a numbr of different places 
where namespace processing is performed (calculating the 'in scope' and 
the 'added' namespaces for an Element). This code was scattered in 
various places, inconsistent, and some places were buggy. I ended up 
stripping all of these places and replacing them all with the 
Content.getNamespacesInScope() concepts.

While convenient, the Content.getNamespacesInScope() methods were (much 
too) slow because they dynamically calculate the Namespaces each time 
they are called (which is fine for unstructured requirements where the 
document structure could change from one moment to the next).

I have thus re-implemented a new 'Namespace Stack' which is much faster 
than a completely dynamic calculation, and it is able to replace the 
various other 'stacks' that were removed before.

This has (mostly) 'restored' the performance of JDOM2's 'guts', I seem 
to be about 1-2% slower at the moment than JDOM 1.1.2

If you look at the numbers you will see that the 'Dump' code is still 
slow though. The Dump code dumps the document in the three main formats: 
Pretty, Raw, and Compact. This is running slow, and is probably related 
to the changes made for Issue #31.

I'm going to fix up that performance in XMLOutputter, and hopefully that 
will pull back the performance numbers on the other areas (the 1% - 2%) 
because each of those processes use the XMLOutputter in some way.
The Dump is particularly slow because it uses the more complicated 
Pretty and Compact mechanisms....).

The 'performance' page below has been updated...


On 13/10/2011 8:27 PM, Rolf wrote:
> Hi all.
> I have put together a 'simple' system for measuring the relative
> performance of JDOM2. The idea is that I need to know whether I am
> improving or breaking JDOM performance as the code evolves.
> Currently the metric code is only useful of you compare apples to
> apples, and, in this case, it means processing a single (medium size)
> XML document on my laptop, yada-yada-yada. But, it should be useful as a
> tool to get a feel for what a code-change does.
> Already I can see that I probably have an issue in the SAXHandler
> (possibly an issue in JDOM-1.1.2 actually) because 1.1.2 is 5-times
> faster in that area than JDOM2.
> I have put together a results page here:
> http://hunterhacker.github.com/jdom/jdom2/performance.html
> It also describes what each test does. If you are interested in seeing
> the code and what it does have a look here (it is not well documented
> and it is still perhaps evolving):
> https://github.com/hunterhacker/jdom/commit/8b719c86913398ace8e197b6de145b33d9d300bb
> Rolf

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