After lurking on the Perl6-lists and finally catching up on this long
discussion about garbage collection, I'm coming out ;-).
The reason I'm coming out is that I realised that we should maybe have a
radically different view on garbage collection than we have now.
Think about it:
1: in an ideal world with unlimited resources, who would need garbage
collection anyway? Or: simple oneliners and small scripts don't need GC.
2: limited resources may appear still available when in fact, they are
not. E.g. a limit on the total number of simultaneous database connections
as seen from the database server, not the Perl process. The Perl process
still thinks it can open connections, when in fact the database server is
already saturated.
3: some resources may not be needed temporarily, but should become
available magically when needed. E.g. virtual memory, database connections
that re-connect automatically after a disconnect (for whatever reason).
4: As a Perl programmer, I don't care whether a file-handle has been closed
because of resource management, as long as it is available to me when I
need it. I don't care whether a connection to a database server has been
re-used by other database server users, as long as I have a connection
(transparently) when I need it.
5: As a server administrator, I would like to be able to limit the
available memory to a Perl program or maximum number of database
connections, so that it behaves nicely towards other users of that server.
I think this calls for a resource management system, rather than a garbage
collection system. A resource management system with an API with which
resources (their creation, cleanup and destruction routines) can be
registered. No garbage collection (which implies a not well thought out
"way of life" to me) but planned ahead resource management (know in advance
what you need when) for situations that need it. (I guess my Dutch
background is showing here, wanting to have everything neatly organised ;-).
This resource management system would ideally include a (pluggable) virtual
memory system for Perl itself (Perl may be able to know better what to
temporarily store on disk than any OS would).
It would include the file IO subsystem.
It would include the handling of any external connections (such as
connections to databases).
Or any other resource that is in limited availability.
And of course, such a resource management system should degrade to a
"everything is free" approach for simple one-liners and small scripts, like
the current situation.
Elizabeth Mattijsen
P.S. Dan: I hope you don't mind not waiting for your PDD, but this seemed
too important to me for the train of thought about garbage collection at
this point in time.
