FFI ruby object caching should be rewritten to not use id2ref

[flavorjones]

id2ref is slow and may be turned off by default in JRuby 1.4.

discussed with wmeissner, and the probable path is to build an API into FFI that is an hash table containing address => weakref(ruby_object).

[nicksieger]

FYI, id2ref (and objectspace) is turned off by default in JRuby. We made a conscious decision to do this because it's expensive and not feasible to manage all live objects with JRuby.

[nicksieger]

Also: tools to help implement the caching in Java/JRuby:

http://java.sun.com/javase/6/docs/api/java/lang/ref/WeakReference.html
http://java.sun.com/javase/6/docs/api/java/util/WeakHashMap.html

Note the last item may not be exactly what is needed, it's a map w/ weak keys, not a map that weakly references its values.

[flavorjones]

Nick, thanks for the pointers (no pun intended).

[flavorjones]

Charlie Nutter published weakling, a library for managing weakrefs efficiently on JRuby. Check out http://github.com/tenderlove/nokogiri/tree/weakling for the branch that uses it, and https://gist.github.com/8bec624e396812c4d00e for an explanation of why it isn't in master yet.

[tenderlove]

I think we can close this one now, can't we?

[flavorjones]

yes. weakling branch was merged into master.