Why GIL? (was Re: what's the point of rpython?)

Steve Holden steve at holdenweb.com
Tue Jan 27 19:10:09 CET 2009

Bryan Olson wrote:
> Paul Rubin wrote:
>> Bryan Olson <fakeaddress at nowhere.org> writes:
>>> An object's __dict__ slot is *not* mutable; thus we could gain some
>>> efficiency by protecting the object and its dict with the same lock. I
>>> do not see a major win in Mr. Banks' point that we do not need to lock
>>> the object, just its dict.
>> If the dict contents don't change often, maybe we could use an
>> STM-like approach to eliminate locks when reading.  That would of
>> course require rework to just about every C function that accesses
>> Python objects.
> I'm a fan of lock-free data structure and software transactional memory,
> but I'm also a realist. Heck, I'm one of this group's outspoken
> advocates of threaded architectures. Theoretical breakthroughs will
> happen, but in real world of today, threads are great but GIL-less
> Python is a loser.
> Wherever Python is going, let's recognize that a scripting language that
> rocks is better than any other kind of language that sucks.
Guido, IIRC, has said that he's against any GIL-removal policy that
lowers performance on single-processor systems. Personally I'd be happy
if there were an *alternative* multi-processor implementation that was
slower for single-processor architectures and faster for
multi-processor, but I'm not about to start developing it.

Steve Holden        +1 571 484 6266   +1 800 494 3119
Holden Web LLC              http://www.holdenweb.com/

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