Saturday, December 22, 2007

docbook-defguide - solving performance and timing issues with native code

Some days ago I wrote down my experiences with packaging docbook-defguide. The main (remaining) issues I mentioned were the resources and the time the package needs to build. Even on an AMD X2 4600+ with 6GB of RAM it needs 7-8 hours.

Today I met with Torsten Werner. He mentioned, that there are some move JVMs I could try. So I tested alternatives to GIJ this night. I found this short summary about free JVMs, which was some kind of interesting.

I began with cacao, which seemed to be fast, but it was killed very early in the build process with an java.lang.OutOfMemory error. Even playing around with the -Xms and -Xmx switches in buildtools/ did not help. So I dropped cacao from the list. Seems both cacao and kaffe create similar problems here and are not suitable for building the package.

Second alternative I tried was sablevm. It directly throw out some warnings or errors so I directly dropped it too.

Next JVM was jamvm. But it was as slow as GIJ. So I dropped it from the list of alternatives too.

Then I found an interesting statement in the article I linked somewhere above. The author said, that his perfomance test time with GCJ/GIJ reduced from 433 to 9 seconds, when he compiled his application into a native executable. So I took a fast look through the docbook-defguide build dependencies and found, that Debian already provides a natively compiled Xerces package libxerces2-java-gcj. But there were no packages for libsaxon-java, libxml-commons-resolver1.1-java and docbook-xsl-saxon. So short and dirty: I downloaded the source for these packages, added the necessary stuff to get natively compiled packages too, built and installed them. Fortunately packages with native code already exist for their dependencies JAXP 1.3 and Xerces.

And what should I say: Now building the TDG needs less then 512MB RAM and it builds in around an hour ... even on my system. I will ask the Debian Java maintainers to add -gcj packages for Saxon and XML-Commons and fix my own docbook-xsl-saxon package. This will hopefully help maintaining docbook-defguide.