From: lance@unix386.Convergent.COM (Lance Norskog)
Subject: Re: TECH: My standard is better than your standard.
Date: 8 Jul 92 23:28:04 GMT
Organization: Unisys/Convergent, San Jose, CA



Distributed garbage collection of objects has not been addressed.

The book "Ecology of Computation", edited by Bernardo Huberman, $97,
(ouch!) has an article on "Agoric Open Computing".  This paper
describes a distributed computation environment where all objects
have bank accounts attached, and participate in an economy.
The entire concept is very 80's/Libertarian/Rand-ish, but
one particular idea has relevance: bankruptcy-based GC.

Each object has a home base, and sends representatives out to
other decks.  Out in the boonies, they rely on "money from home".
That is, they have a "money" account on the local deck.  
Periodically, the home base sends CompuBucks out to its satellite 
objects.  When they run out of the old $CB, they go bankrupt
and are dissected for their resources (disk/RAM space/CPU time).

More concretely, the home base sends out a keep-alive to each
satellite every X seconds.  After X*M seconds with no keep-alive,
the satellite object disappears.  This is a very useful distributed
GC algorithm because the required network traffic is predictable.
If the keep-alives are concentrated in backbones and fanned out
(after all, they are not urgent messages in terms of end-to-end
delay), the traffic load grows more slowly than any other
scheme I've examined (not that many, to be sure).  
Assuming that interconnect cable & switchers will be installed
as an interconnect mesh, network traffic for this algorithm
could grow more slowly than the total capacity of the growing network.

Lance Norskog
(Thanks to an engineer at Autodesk who turned me on to this.
I, shamefully, have forgotten his name.)