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A couple garbage collector questions

Frank Mitchellfrankm at bayarea.net
Fri Apr 20 03:26:22 EDT 2001


Daniel Berlin wrote:>> On Fri, 20 Apr 2001kragen at pobox.com wrote:>> > Neil Schemenauer <nas at python.ca> writes:> > > Kragen Sitaker wrote:> > > > Reference-counting exacts very heavy performance costs, no> > > > matter what you back it up with.> > >> > > Can you back that statement up with any data?> >> > Not right now, sorry --- too busy.  But if you happen to find data on> > the other side, I'd be happy to hear about it.>> So, in other words, your answer is "no".While I don't have any references to empirical comparisons, the book_Garbage Collection: Algorithms for Automatic Dynamic MemoryManagerment_ by Jones and Lins compares refcounting and tracingalgorithms.The upshot from that book seems to be that comparisons are tricky atbest, but in general refcounting is more of a performance drag thantracing: the accumulated overhead for pointer writes tends to outweighthe pauses for collection.  (OTOH, hard real-time or distributed systemsmay be happier with sophisticated refcounting, and for slowly-changingdata structures refcounts are perfectly acceptable.  With the extensivecompiler support described by Ms.[?] Schroeter, refcounts would be atleast competitive ... but how many compilers actually use thattechnique?)-- Frank Mitchell (frankm at bayarea.net)Ridiculous Lucky Captain Rabbit King!  Lucky Captain Rabbit KingNuggets are only for the youth!-- Powerpuff Girls, "Jewel of the Aisle"


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