questions

[Per Hedeland]

Vlad Dumitrescu wrote:
>how is the free source version of Erlang related to the professional 
>    version? Will it always be one step back? (since the pro version now 
>    is 4.8)

I hope you don't think we're just sitting on the "pro" version for a
release interval until we release it as free source...:-) The problem is
that it's currently a lot of work, much of it manual, to turn "pro" into
something that can decently be released in source form, due to "pro"
being interwowen with the local development environment (ClearCase etc),
being targeted for binary-only releases, having portability problems,
etc.

That work has *so far* only been done once, with 4.7.4 -> open-source
47.4.0 - and the goal is that it shouldn't have to be done again;
quoting Sebastian Strollo from a message here back in May:

                                     Right now we are working hard
  to make sure that in the future we will make the main release the same
  as the open source release. The aim right now is to make the next
  major product release (beginning of November) this new unified source
  release.

I.e. we could in theory tar up the current "pro" and put it on the web
site, but virtually no one would be able to build it, and I don't think
that would benefit either the Erlang user community or Erlang's
reputation.:-) 

>is  the VxWorks port just a regular port, or it does use the special 
>    facilities of the OS in order to be more efficient?

I believe it's pretty regular, special facilities being used mostly to
overcome the mismatch between what the OS provides and what the Erlang
runtime system expects.:-) (E.g. it really doesn't have an equivalent of
a Unix pipe, so someone wrote a ("real OS") driver that implemented it.)

Basically, what is a Unix process in Unix is a "task" in VxWorks, rather
than (e.g.) Erlang processes being mapped to VxWorks tasks. Context
switches between VxWorks tasks should be less expensive than between
Unix processes, meaning that using "port programs" should be "cheaper"
in VxWorks, but as far as I know no measurements of this have been done.

--Per Hedeland
per@REDACTED