From: matz@... (Yukihiro Matsumoto)
Date: 2002-09-04T02:42:12+09:00
Subject: Re: Best GC for Ruby?

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.

							matz.