[gclist] A problem with the Baker treadmill.

[Charles Fiterman]

I was updating our Treadmill collector to work in a
multi threaded environment when the problem with
this kind of write barrier struck me hard.

The write barrier moves stuff from the white queue
to the grey queue. This means locking those queues
or locking the whole collector or something like that.
While moving things from one queue to another is
acceptable overhead that lock is way over the top.

Years ago I worked with a machine from Perkin Elmer
which had an instruction that moved things from one
double linked list to another as a single atomic
operation. I miss this feature about three times
a year and miss it badly.


			-  
Charles Fiterman		Geodesic Systems
414 North Orleans Suite 410	Phone 312 832 1221 x223
Chicago IL 60610-4418		FAX   312 832 1230
				http://www.geodesic.com

A computer language without garbage collection
  is like a city without garbage collection.