Re: JVM Usenix paper got rejected

[Jeff Sturm <jeff dot sturm at appnet dot com>]

Nic Ferrier wrote:
> I think that GCJ is a really usefull weapon in the armoury. It may
> even become a standard way of improving Java performance but my own
> view is it's likely to remain just another option.

However gcj is unique in several ways.

> A *lot* of work is happening on this and there are some quite
> interesting developments. GCJ is one. The potential of HotSpot engines
> is another and approaches like Jazelle is yet another.

In my opinion the performance is a losing battle.  Java has become big
business.  The gcj team simply doesn't have money and resources as e.g.
the Hotspot engineers do.

I know of at least three ways gcj can stand out over the alternatives:

1) It's currently the only way to get reasonable performance across a
variety of machines.  
For the most common architectures good VMs are freely available (though
not open source), and there exist several highly portable bytecode
interpreters for the others.  But if you are running, say, Linux on ARM
there simply aren't many good options around.

2) There are some tasks for which JIT compilers are poorly suited.

Small memory environments may not have the capacity for dynamically
compiled object code, class files and a JIT engine.  Also, programs
which are not repetitive do not tend to benefit from a JIT.  As an
experiment I recompiled Sun's javac compiler with gcj and observed
better than a 400% speedup over a normal javac while building a tree of
approx. 250 Java sources.

3) The libgcj is open and available for experimenting and innovation.

A great example is today's thread on memory-mapped byte arrays.  Without
from the availability of free clean-room Java runtimes, you coudln't
attempt such innovation without a source license from Sun.  (And then it
would probably be difficult anyway.)

> Also, I don't think that the usenix people necessarily represent the
> "java community".

Probably not.  But I suspect gcj would not be popular with many Java
proponents.  You might say gcj emphasizes Java as a language over Java
as a platform.  Some would say that's the wrong direction for Java.  The
Usenix reviewer could have been similarly biased.

Myself, I tire quickly of language wars.  We use Java because it's
reasonably fast, safe, extensible and well-supported.  But the real
innovation seems to have drained out of Java nowadays, and I find myself
keeping one eye open for something better.

Jeff