[kaffe] need your help in optimising Kaffe
robilad at kaffe.org
Thu Sep 2 14:17:27 PDT 2004
Kirankumar T wrote:
> we are doing some research application as part of it we are
> trying to
> optimise the kaffe JVM .So we removed almost all the lib,doc...
> now it came to 1.5Mb
> to further optimise it i am thinking of removing un used user
> define class loaders
> is it possible to remove userdefine class loaders?
I'm not sure I understand. What is a user defined class loader?
> can i have kaffe jvm of size less than 1Mb?
In theory, I'd say yes. I've tried to cut the i386 VM down to just the
things necessary for running HelloWorld. My installed size, after
purging all the things that are not necessary is
topic at jbox:/tmp/classes$ /tmp/topic/current/bin/kaffe HelloWorldApp
topic at jbox:/tmp/classes$ du -ks /tmp/topic/current
Using latest CVS, debian sarge, gcc 3.3.4.
A few things: this is not statically liked, so by using static linking
for the VM, it should be possible to bring the size further down. It's
currently not possible to disable the building of the native libraries I
explicitely removed by hand. I could provide a set of configure options
to do that, though. --without-native-zip, without-verfier, etc.
The native libraries needed for hello world, and their sizes:
topic at jbox:/tmp/classes$ ls -sS1 /tmp/topic/current/jre/lib/i386/
All the libraries have been compiled with gcc's -Os option to opmitize
for size. They have been stripped, too.
The largest chunk is the 380k of libkaffevm, of which the largest
portion is in the translate function of jit3. You could further reduce
the size of the library by chosing to use the smaller jit engine instead
of jit3, or the even smaller interpreter engine.
By compiling the code statically, you should be able to reduce the size
further, and get rid of most of the 0k and 4k files.
The other large chunk was the class library. I used a very simple scheme
to create a transitive closure of java.lang.Object and the few other
classes needed by kaffe. I went to the source directory
libraries/javalib and then called
jikes -d /tmp/classes/ -g:none java/lang/Object.java
which compiled just the smallest set of classes needed, and wrote them
into /tmp/classes. Jarring the classes there resulted in a 560k rt.jar
file. It's available at http://www.kaffe.org/~robilad/mini.jar
So, all the things taken together, I'm quite confident that you can make
a version of kaffe that fits in under 1M and can run programs that don't
use most parts of the class library.
As you're doing research, you may be interested in implementing a free
software PACK200 (de)compression implementation. That would
significantly reduce the size of jar files. Other than that, a cheap
(but probably very slow) way to reduce the size of rt.jar would be to
use something like tar.bz2 instead of zip. mini.jar is about half the
size as a tar.bz2 file, but you'd need to write a separate class loader
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