what's the point of rpython?

[Paul Rubin]

"Brendan Miller" <catphive at catphive.net> writes:
> > http://www.boost.org/doc/libs/1_37_0/libs/smart_ptr/shared_ptr.htm#ThreadSafety
> 
> I think you are misreading that. It says that multiple assignments to
> different copies of a share_ptr in different threads are fine.

I'll respond to this later.

> http://www.codemaestro.com/reviews/8
> http://siyobik.info/index.php?module=x86&id=159
> 
> Again, I'm not an assembly guru, but his sounds like exactly what
> you'd want. It gains exclusive access to system memory in a
> multi-processor environtment without leaving user space. Thus XADD is
> an atomic increment/decrement. It would be educational if someone more
> famliar with x86 than me could speak to the performance merits of this
> on modern multicore machines.

Those links describe using the LOCK prefix, which as the name implies,
asserts a lock, so it is no longer "lockless reference counting".  The
LOCK prefix adds about 100 cycles to the instruction.