chris at kiffer.eunet.be
Mon Feb 19 14:00:42 PST 2001
On Wed, 14 Feb 2001, Javier Garcia wrote:
> Hi. I'm very interested in small JVM's for embedded
> systems. I have to say that after two weeks of
> Internet searching, the only JVM that is clear enough
> for me is Kaffe, but the problem is the size. I want
> to get a JVM of about 5M, but when I installed Kaffe I
> got about 50M.
We need to distinguish between several definitions of "size".
1. Size of the source files after decompression. Probably includes
a bunch of documentaion and some "useful resources" which you don't
need to put on the target machine if you don't want to.
2. Size of the binary executable file ("stripped", i.e. minus any extra
information added by the compiler to help with online debugging --
typically the stripped file is half the size of the unstripped file).
It should be possibly to build a JVM and essential native libraries in
less than 1 MB, so long as the platform you are working on doesn't
insist on linking in huge libraries. (Which should not be the case
on an embedded system).
3. Minimum amount of RAM that the system needs in order to boot up.
Depending on what flavour of Java your embedded system wants to
support, you have to get 100--200 classes loaded up just to do
business, and the class files involved contain several thousand
text strings, to mention just one aspect. So to get the JVM to
run in just 4 MB of workspace (1 + 4 = 5) is going to be a tight
> I have also downloaded the datasheet
> and I got astonished when I saw that the size of Kaffe
> is said to be less than 2M.
I guess that refers to item 1. in my list ...
> What I'm doing bad to get
> such a huge installation? What are the config options
> to get Kaffe running in 2M? And another one: if
> anybody knows about some other free-source JVM's with
> a little size (for Linux, of course)
Why the "of course"? At the memory levels you're talking about,
eCos would sound like a better bet.
Chris Gray chris at kiffer.eunet.be chris_gray at bcs.org.uk
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