[pypy-dev] Would the following shared memory model be possible?

[Maciej Fijalkowski]

On Thu, Jul 29, 2010 at 7:18 AM, William Leslie
<william.leslie.ttg at gmail.com> wrote:
> On 29 July 2010 11:33, Kevin Ar18 <kevinar18 at hotmail.com> wrote:
>> In detail, here's what I mean:
>> * unlike POSH, utilize OS threads and shared memory (not processes)
>> * Create a special shared memory location where you can place Python objects
>> * Each Python object you place into this location can only be accessed
>> (modified) by 1 thread.
>> * You must manually assign ownership of an object to a particular thread.
>> * The thread that "owns" the object is the only one that can modify it.
>> * You can transfer ownership to another thread (but, as always only the
>> owner can modify it).
>
> When an object is mutable, it must be visible to at most one thread.
> This means it can participate in return values, arguments and queues,
> but the sender cannot keep a reference to an object it sends, because
> if the receiver mutates the object, this will need to be reflected in
> the sender's thread to ensure internal consistency. Well, you could
> ignore internal consistency, require explicit locking, and have it
> segfault when the change to the length of your list has propogated but
> not the element you have added, but that wouldn't be much fun. The
> alternative, implicitly writing updates back to memory as soon as
> possible and reading them out of memory every time, can be hundreds or
> more times slower. So you really can't have two tasks sharing mutable
> objects, ever.
>
> --
> William Leslie

Hi.

Do you have any data points supporting your claim?

Cheers,
fijal