[Python-Dev] Removing the GIL (Me, not you!)

[Justin Tulloss]

On 9/13/07, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
>
> Jason Orendorff wrote:
> > The clever bit is that SpiderMonkey's per-object
> > locking does *not* require a context switch or even an atomic
> > instruction, in the usual case where an object is *not* shared among
> > threads.
>
> How does it tell whether an object is shared between
> threads? That sounds like the really clever bit to me.


If you look at the article, they have a code sample.

Basically a global is "owned" by the first thread that touches it. That
thread can do whatever it wants with that global. If another thread wants to
touch the global, it locks everything to do so.

This is a pretty good idea except that in Python there are so many globals
that all threads benefit from having access to. Luckily, except for their
reference counts, they're mostly read-only. Therefore, if we can work out
this reference count, we can probably use a similar concept.

Justin
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