[gclist] Experience with conservative GC sought

Jim Blandy jimb@red-bean.com
Wed, 21 Jan 1998 14:48:42 -0500

>If I were the on the development team, it would not be difficult 
>to decide whether I want to spend more time now debugging a precise
>collector where I have control over all aspects of the problem or
>whether I want to spend much more time later trying to provide a way
>to tweak that 1 in 1,000 heap that I have no control over (times a
>million+ users) that leaks so bad you have to restart every hour... 

Oy.  I suspect you have not done significant work on Emacs.  Almost
every release of Emacs has had some bugs related to improper
maintenance of the stack root list.  Stallman admits he makes these
mistakes frequently himself, so I don't think it's an issue of
programmer competence.  (Come on, you know what I mean. :) )

Give my experience with Emacs, I am a solid fan of conservative
techniques.  I am more of a fan of languages that support precise GC,
but sometimes one hasn't a choice about such things.

I'm running SCWM, the Scheme-Configurable Window Manager for X
Windows, which is based on Guile.  That's a long-running application.
I haven't noticed any leakage bugs.  Aubrey Jaffer uses his Scheme
system, SCM, on which Guile is based, for long-running digital circuit
simulations, and reports that he has never encountered a storage leak
due to the conservative GC.  Note that Guile uses conservative marking
only to find pointers on the C stack, and in continuations; it uses
precise techniques for all other intra-heap pointers.

I suspect you are simply suffering from the usual Indiana University
Perfectionism Syndrome.  :)