[Python-ideas] Concurrent refcounting research
rhamph at gmail.com
Tue Oct 16 23:26:46 CEST 2007
On 10/16/07, Jason Orendorff <jason.orendorff at gmail.com> wrote:
> GIL-slayers take note. Here are two papers about concurrent reference counting:
> An On-The-Fly Reference Counting Garbage Collector for Java
> Levanoni and Petrank, 2001.
> Efficient On-the-Fly Cycle Collection
> Paz, Bacon, Kolodner, Petrank, and Rajan, 2005.
> "On-the-fly" means the algorithm is neither "fully concurrent" nor
> "stop the world". Rather, each thread pauses occasionally to do some
> work. Instead of a GIL, you have a lock that covers this periodic
> The details are awfully complex, but there may be insights worth
> gleaning regardless.
A key assumption of these papers (and presumably most such papers) is
that you have a true tracing GC to fall back on, not one bootstrapped
from reference counts like CPython has. This means that long-lived or
shared objects can disable reference counting entirely, and not face
the severe contention it would otherwise create.
Adam Olsen, aka Rhamphoryncus
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