xmlrpc idea for getting around the GIL

[Patrick Stinson]

On Wed, Dec 2, 2009 at 7:42 AM, sturlamolden <sturlamolden at yahoo.no> wrote:
> On 2 Des, 02:47, Patrick Stinson <patrickstinson.li... at gmail.com>
> wrote:
>
>> We don't need extension modules, and all we need to do is run some
>> fairly basic scripts that make callbacks and use some sip-wrapped
>> types.
>
> Sure, you use SIP but not extension modules...
>
>
>> - Python is not suitable for real-time work.
>>
>> Not true. We have been running python callback code using
>> PyObject_CallObject from within our audio thread for some time without
>> a problem, and it's *extremely* fast.
>
> It seems you are confusing "real-time" with "real-fast". The fact that
> something runs fast does not make it "real-time".
>
> Python is not suitable for real-time applications, nor are the OSes
> commonly used to run Python.
>

Semantics aside, my point is that it runs well enough in our
environment. If the audio is smooth, it is considered "working".

>
>
>> We
>> need just a liiiitle push to get our code to work at low latencies,
>> and the only thing that is standing in our way is that all threads
>> 9usually around 20 have to block on the Gil, and this causes small
>> gaps in the sound at low latencies (around 5ms, or 64 sample period).
>>
>> ...almost perfect.
>
> Python is not programmed with real-time applications in mind: You have
> no guarrantees on maximum time-lag when a thread is blocked on the
> GIL.

We don't need theoretical guarantees, because we've tried it and it
works. That's the bottom line

>
> "Priority requests" (i.e. pre-emptive multitasking) was removed from
> Antoine's "newgil" branch, but that is the kind of mechanism you would
> need. Even with priority requests, Python would not be suitable for
> real-time apps, as extension modules (e.g. C++ wrapped with SIP) can
> hold the GIL forever.

see above.

>
> You will also need an OS with a real-time scheduler and a real-time C
> library, such as QNX or VxWorks.
>
> I find thea idea of a true real-time Python very interesting, but it
> would take a completely reworked interpreter.
>
>
>
>
>
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>