[gclist] zillion objects

Ji-Yong D. Chung virtualcyber@erols.com
Thu, 23 Aug 2001 20:17:05 -0400


    This question is a general one. In brief:
if you have a large number of objects, a small
fraction of which die (very slowly), is there a
method of automatic memory management
(i.e., gc), which would not (1) try to copy most of
those objects or (2) trace most of those pointers?

    Objects here can be cyclic.


    Detailed description of the question.

    Say I have 100 M worth of objects resident
in memory. Most of them are not large, and their
pointers criss-cross everywhere.

    One characteristic of these objects is that a
fraction of them die, be it very slowly. If you GC'ed
these objects (via generational collector), when the
oldest generation has to be garbage collected, the
collector has to scan all the pointers that are boxed
in 100 M worth of objects. This can be CPU

    If you impose the condition that there are no
cycles, then solving the preceding problem is easy: just use
reference counting. Because reference counting
only touches objects that are affected when a reference
is decremented, the overall cost to the above system is low,
even though one may have 100 M of small, pointer-filled

    Of course, for the problem I am considering,
there is no guarantee that the chain of ponters
are acyclic.