what's the point of rpython?

Brendan Miller catphive at catphive.net
Tue Jan 20 05:00:15 CET 2009

Maybe I'm missing something here but a lock free algorithm for
reference counting seems pretty trivial. As long as you can atomically
increment and decrement an integer without locking you are pretty much

For a reference implementation of lock free reference counting on all
common platforms check out boosts implementation of shared_ptr (a
reference counting smart pointer designed around multithreaded use

>There are well known concurrent and parallel GC techniques that
Hmm... I didn't really mention poor parallelism as a problem of GC. As
I see it the two trade offs that have to be made for GC vs alternative
techniques. The "embarrassing pause" during compaction which makes it
impossible to use for applications like interactive video display that
can't halt to compact a several gigabyte heap without causing stutter,
and the loose memory profile.

Maybe the document you sent me addresses those, and I'd be interested
if it did. It's 150~ pages though so I haven't really had time to read
it yet.

As far as parallelism problems with GC go... the only ones I can
imagine is that if you had a lot of threads going generating lots of
garbage you would need to start to compact more frequently. Since
compaction halts all threads, this could potentially cause very
frequent compactions? Is that what you were getting at? I'd wondered
about that before, but didn't know for a fact whether it came up in
real world scenarios.

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