From: Ben Goertzel (ben@webmind.com)
Date: Tue Jul 17 2001 - 20:40:57 MDT
> > Not to get too far carried away with this thread, but there are a lot of
> > annoying subtleties here.
> >
> > For instance, a 64 bit JVM gives you more memory, but it also
> causes each
> > object to *consume* more memory, by using 64 bit ints, floats, etc.
>
> I don't see the big problem... the 64bit address space should allow for
> something like 2^32 times as much memory, not simply double the 2GB
> current limit. Who cares if your code takes up twice the mem when running
> if you can have access to so much more memory. Or am I missing something?
Yes, this is right, in the long run. In the short run, if you have a
machine with say 4GB of RAM, the advantage gained by a 64-bit JVM (an
increase from 400MB to 800GB of pragmatically usable memory) will be mostly
or entirely eaten up by the extra memory required to store 64 bit basic data
types, unless you use bit masking to get around the problem. But if you
have a machine with say 100 GB of RAM, then the exponential versus linear
comparison that you cite kicks in.
It happens that the most RAM you could get in a relatively inexpensive
computer (pentium-based, I mean) as of last year was 4GB of RAM, and so
that's what we had at Webmind Inc. If you can afford a Starfire or an IBM
mainframe, then there are no worries; and I imagine this is the primary
initial market for the 64 bit JVM.
- Ben
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