[gclist] Treadmill doubly-linked list costs

[Jerry Leichter]

A number of people have asked how my proposal to use a single pointer field with the treadmill algorithm could work.

It wouldn't; at least, I don't know of any method, now that the problem has 
been pointed out.  I missed the obvious.  Sorry 'bout that.

(It's actually kind of funny:  The *collector* part of the treadmill algorithm 
works just fine.  It's the *mutator* that has problems.  As someone said (Henry 
Baker?), both the collector and the mutator repeatedly walk all of accessible 
memory; the collector is just more organized about it.  It's exactly because of 
that that it can manage with XOR'ed pointers!  Only in the context of the GC 
list could one so concentrate on the collector as to forget the mutator - where 
the actual work of the program goes on!)
							-- Jerry