Re: [rvm-core] The future of the thread model, interactions with class libraries

I agree that getting Harmony working with native threads is an
important goal, but I can not see how we can list it as a blocker.

The previous implementation of Harmony was not ready for production
use. From the tests we were running it never supported multiple
processors, and when running with a single processor had a significant
number of failures. Obviously moving to a system without green threads
makes running with a single processor no longer possible. This was a
well understood problem, and work on Harmony to fix this issue was
deliberately delayed until after native threads was implemented.

I think that the decision to make a release should be based on
stability and improvements in our supported configurations---those
that are running (and passing) sanity runs. Obviously when we have a
stable implementation using the Harmony libraries that is a
significant release milestone. When this happens, it may even be
sensible for Harmony to become the default class library
implementation. If we can have Harmony working for our next release
then all the better, but it does not make sense to significantly delay
releases solely for this.

This relates to a significant issue that I don't think was adequately
addressed at the time. The announcement of our initial
compatibility/support for the Harmony libraries was premature, and I
know made a lot of the core team uncomfortable. Such announcements
have the potential to significantly affect the credibility of Jikes
RVM, and should not be made without some consultation within the core
team. What we claim to support officially in releases of JikesRVM has
a direct impact on everyone working on the project.

I think it is clear that we all want to work toward compatibility with
Harmony (and possibly OpenJDK) but we need to do so carefully.

I have left aside my thoughts on the low level technical detail here;
it is important to take a step back from that and solve the strategic
issues first.

Cheers,
Daniel.

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