At 2:42 AM +0900 9/4/02, Yukihiro Matsumoto wrote:
>Hi,
>
>In message "Re: Best GC for Ruby?"
>     on 02/08/30, "Justin Johnson" <justinj / mobiusent.com> writes:
>
>|Maintaining the remembered sets without a hardware write barrier is still
>|posing a problem.  I can't seem to find any good information on software
>|write barriers.  There didn't seem to be anything in the Jones and Lins
>|book.
>
>See "7.5 Inter-generational pointers".  In p.172, "Using bytes rather
>than bits speeds up the write-barrier, reducing it to just three SPARC
>instructions in addition to the actual store".  So it's not
>impossible, at least in theory.
>
>|Also, I'm not sure how software write barriers could be introduced without
>|making extension programming more error prone and difficult.
>
>It can be, if all attribute modifies are done by API.  Though we can't
>assume this if we are developing general purpose collector like
>Boehm's.

Out of curiosity, have you given this a shot to see how performance 
looks? I've been debating the merits of generational collection, but 
I've been worried about the performance impact (and the code hassle) 
of maintaining generation barriers.
-- 
                                         Dan

--------------------------------------"it's like this"-------------------
Dan Sugalski                          even samurai
dan / sidhe.org                         have teddy bears and even
                                       teddy bears get drunk