[Python-Dev] Stackless Design Q. (original) (raw)

Christian Tismer tismer@tismer.com
Wed, 20 Feb 2002 13:44:31 +0100

Greg Ewing wrote:

Now I am at the point where I'm worst suited for: Design an interface.

Please tell me what you think, and what you'd like to change. It's not clear exactly what you're after here. Are you trying to define the lowest-level interface upon which everything else will be built? If so, I think what you have presented is FAR too complex.

The old Stackless with its continuations was at lowest possible level, in a sense. What I now try to do is a compromise: I would like to build the simplest possible but powerful set of methods. At the same time, I'd like to keep track of tasklets, since they are now containing vitual information about stack state, and I cannot afford to loose one of them, or we'll crash. The little doubly-linked list maintenance is very cheap to do. So my basic idea was to provide what is needed to get uthreads at very high speed, without the ned to use Python for the basic machinery.

It seems to me you need only two things:

Yes, I need these two things, and some more.

All the other stuff you talk about -- passing values between tasklets, rings of runnable tasklets, scheduling policies, etc -- can all be implemented in Python on top of these primitives.

Sure it can, with one exception: My tasklets will also support threading, that is they will become auto-scheduled if the user switches this on. But auto-scheduled frames are a diffeent kind of thing than those which are in "waiting for data" state. I need to distinguish them or I will crash. That's the reason why I keep these linked lists. Switching to the wrong tasklet should be rock solid in the kernel, this is nothing that I want people to play with from Python.

Thanks a lot anyway, I'll try to make it even simpler.

ciao - chris

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