dynamic library cost (was RE: libtool, java woes)

Tom Tromey tromey@redhat.com
Thu Apr 12 22:17:00 GMT 2001

>>>>> "Hans" == Boehm, Hans <hans_boehm@hp.com> writes:

Hans> (As far as I know, the only way to currently get a write barrier
Hans> is with virtual memory techniques.  That means generational or
Hans> incremental collection requires virtual memory, and you only get
Hans> update information at coarse granularity.  And you're presumably
Hans> limited to a conservative stack scan.)

That is definitely the current state of affairs.

Adding write barrier support doesn't appear to be hugely difficult.
Jon Olson implemented it (I haven't seen the code).  Is it worth doing
this with your collector?

Adding non-conservative stack scanning is much harder.  It has been
added to gcc before (in gcc 1.something -- ancient history).  It is
definitely possible, but it touches a lot of the compiler.  There's a
paper on this by Rick Hudson.  When I say "much harder", my guess (and
this is really a wild guess) is that it is on the order of a man year.


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