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From "Geir Magnusson Jr." <ge...@apache.org>
Subject Re: Work items
Date Fri, 27 May 2005 22:18:05 GMT
Thanks Steve!

Looking at these, they seem to be split between working at the  
respective projects, and working here.

For stuff elsewhere, how do we want to keep in touch?  Cross-posting  
might be too much, but maybe people that do go work on these ideas  
elsewhere can report back from time to time?

For the stuff that can work here, lets try to establish informal  
subject keys (ex [dynaload] ........ ) so we can separate what is  
what on the dev list.  Also, I'll setup SVN and start the committer  
policy discussion.  We're going to need to highly segment the code  
repository for reasons that will be made clear.


On May 27, 2005, at 5:30 PM, Steve Blackburn wrote:

> Hi all,
> I imagine I'm not alone in thinking that there are a great many
> concrete things people can be working on right away, even while
> discussion on key design issues continues.  It would be good to have a
> work list of concrete work items that eager folks can go to.  So I'll
> stick my neck out and throw out a list of a few tasks that can be
> worked on right away.  These include prototyping, research and
> improvements to existing infrastructure. I have not included broad
> design issues on there since design issues are not "projects", but the
> subject of large scale discusion.
> Among the items listed below, I have included items from MMTk and
> Jikes RVM and I'm hoping others will do the same and add items from
> other projects that work towards the goal of contributing to the
> Harmony project.  I hope everyone feels free to add to the list with
> any work items they can think of (and argue for the removal of items
> if they want).  This is just a start.  The list definitely needs
> improving and growing, but at least there is no reason for anyone to
> be sitting on their hands ;-)
> What do people think?
> --Steve
> . prototype backend generator [prototype]
>  Explore Ertl & Gregg's work to develop a "backend generator" which
>  leverages the portability of gcj to automatically generate backends
>  for a simple JIT.  The semantics of Java bytecodes are expressed
>  using Java code, and then gcj is used to generate code fragments
>  which are then captured for use by a simple JIT (Ertl & Gregg used C
>  and gcc, but with vmmagic support, Java and gcj would be nicer).
>  See also
> http://www.csc.uvic.ca/~csc586a/papers/ertlgregg04.pdf
>  http://mail-archives.apache.org/mod_mbox/incubator-harmony-dev/ 
> 200505.mbox/%3c20050523.084854.343163557.shudo@aist.go.jp%3e
> . vmmagic support for gcj [gcj]
>  Implement the vmmagic unboxed types in gcj, so they are compiled to
>  unboxed native operations (eg Address.loadInt() will perform an
>  integer load from an address value, and all instances of Address
>  will appear not as object instances but as 32/64 bit primitives).
>  http://jikesrvm.sourceforge.net/api/org/vmmagic/unboxed/package- 
> summary.html
>  This will allow gcj to be used to build Java code which uses the
>  vmmagic primitves.  Thus gcj could be used to build a virtual
>  machine image, an interpreter, or be used to automatically generate
>  a compiler back end.
> . bytecode optimization [reserach]
>  On architectures where there is no high performance JIT, the
>  performance of the interpreter or simple jit (see backend generator
>  project) will be the limiting factor.  (High performance JITs are
>  heavyweight and inevitably will only exist on the architectures were
>  there has been demonstrated demand for it). Since a simple
>  interpreter or simple JIT has very limited opportunity for
>  optimization, it may be very important to perform bytecode
>  optimization.  There are a number of toolkits including bloat and
>  soot.
>  http://www.sable.mcgill.ca/soot/
>  http://www.cs.purdue.edu/s3/projects/bloat/
>  http://portal.acm.org/citation.cfm?id=781995.782008
> . dynamic loading VM components and libraries [research]
>  Whether built in Java, C/C++ or a mix, harmony should probably have
>  strong support for dynamic loading and sharing of precompiled
>  "libraries" designed in from the begining.  This is a very
>  interesting problem space, possibly made more interesting by
>  JSR-121.  Jikes RVM, for example, mmaps a monolithic image
>  corresponding to a lot of precompiled and initialized classes.  ORP
>  dynamically loads components such as the JIT.  Generalizing these
>  ideas would be enormously helpful to harmony. Minimizing the
>  footprint of the VM, particularly in the context of multiple VMs is
>  interesting.  There are complex issues associated with class
>  initialization and related code optimization issues (a static final
>  field that is initiated in a context sensitive way can't be constant
>  folded by an optimizing compiler except in a context specific
>  way---in other words the optimization would have to be ignored or
>  else separate code would have to be generated for each instance).
>  This also stirs up questions of heap and memory layout, the location
>  of class fields versus code etc etc.  There is a lot here.  It is
>  very important and very interesting.  As far as jsr 121 goes, it is
>  important to note that Doug Lea is involved in both Harmony and the
>  JSR proposal.
>  http://jcp.org/aboutJava/communityprocess/pr/jsr121/index.html
> . benchmarks [dacapo]
>  Good benchmarks are essential.  A major effort has been underway in
>  the DaCapo group to put together a new benchmark suite.  Plans are
>  to relicense this under the Apache license.  The suite badly needs
>  new packaging and a new harness and is looking for someone to pick
>  up the ball and run with it.  Many of the constituent benchmarks are
>  drawn from the Jakarta project.
>  http://www-ali.cs.umass.edu/DaCapo/gcbm.html
> . Generalize object model abstraction [mmtk,ovm]
>  There are many different object models (ways of laying out an
>  object, its header and associated metadata).  A good GC toolkit
>  should be able to abstract over the various object models a host VM
>  may implement.  Providing a suitably high level abstraction without
>  performance penalty is an important item on the MMTk todo list.
>  This sort of generality is something the OVM project has focussed
>  on.
>  http://www.ovmj.org/
>  http://www.ovmj.org/ovmir.ps
> . MMTk as .so [mmtk]
>  Build MMTk as a .so, ideally adding new pragmas so that barriers and
>  allocation sequeneces are materialized as inlined C in mmtk.h.
>  Builds on prior work by Robin Garner and Andrew Gray.  Will allow
>  MMTk to be linked into C-based VM's.
>  http://cs.anu.edu.au/~Andrew.Gray/rmtk/
> . jikes rvm opt modularization [jikesrvm]
>  The Jikes RVM optimizing compiler is one of the valuable aspects of
>  Jikes RVM.  If it is to be reused by harmony it needs to be properly
>  modularized.  This project will involve "normalizing" the code
>  (getting rid of Jikes RVM-specific idioms and ideosynchrosies) and
>  clearly defining the module.  In addition to extracting one of the
>  most important
>  http://jikesrvm.sourceforge.net/userguide/HTML/optdetails.html
> . remove dependency on jburg in jikesrvm [jikesrvm]
>  iburg is a widely used bottom up re-write tool used to produce code
>  generators.  Jikes RVM added some extensions, known within jikes rvm
>  as jburg.  There also exists a tool called jburg which is a java
>  implementation of the original burs work (not directly derived from
>  iburg, but written from scratch on the basis of the orginal Fraser,
>  Hansen and Proebsting paper.
>  http://jburg.sourceforge.net/
>  http://cvs.sourceforge.net/viewcvs.py/jikesrvm/rvm/src/tools/jburg/
>  http://www.cs.princeton.edu/software/iburg/
>  http://portal.acm.org/citation.cfm?id=151640.151642
>  http://www.cs.manchester.ac.uk/mscprojects/projects.05/jam.html

Geir Magnusson Jr                                  +1-203-665-6437

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