Hi Arnar, You said, "There have been discussions here occasionally about something generic, like wrapping libevent or similar in an interface that "looks" synchronous but in the background does async I/O and uses channels to make it look synchronous." That is of course what this does. Points: - "There have been discussions" implies a blocking point ;-) This is a design that is complete. simple, and proven, and could be put in the virtual machine tomorrow. - The notion of "asynchronous IO" is vague and, in the typical manner, therefore threatens to complicate matters with a huge palette (your "myriad") of explicit tools that work at cross-purposes. By contrast, the first phase of this design (Channel Communication plus Hardware Select) would result in NO VISIBLE CHANGE, no libraries - just a clearing of the "blocking" logjam and freedom for other tasklets to run efficiently while the hardware wait is going on, just as David wanted. - There is also no visible change if you add the second phase, "Timer": the sleeping tasklet (or simultaneously sleeping tasklets) would take no blocking time on the round robin. (Your time.sleep code indicates this is not currently the case - am I right, or does Py_BEGIN_ALLOW_THREADS set up a separate queue?) - The complication added by these phases is in the virtual machine only: a couple of new queues (channel and timer) in addition to Stackless's round robin scheduler. The channel queues have maximum length 1. I am assuming that "tasklet" = "process" in the sense I defined in the note (which certainly appears to be the case, with the examples you gave). I am also assuming there is some memory dedicated to the tasklet for its whole life (but I can't imagine anything being "stackless" without that!). - The only thing that would create a new visible interpreted code option would be the last phase, the user-level ALT or select. And that could be done in any way that people like: for instance, as a standard Unix-like select call, or a transputer-like ALT branching on readiness of IO channels. In my experience, that is the central key to any serious parallel coding (changing disorder into order, as it were). - And all without a myriad: the only other such structure that I've ever found useful is a simple binary semaphore (which works just like the timer queue, and avoids the ALT/select overhead in a common case). That could be added later. - The only question is whether something about the object structure forbids input from several channels in one tasklet.
Larry On 10/9/08, Arnar Birgisson <[EMAIL PROTECTED]> wrote: > > Hi Larry, > > On Fri, Oct 10, 2008 at 00:54, Larry Dickson <[EMAIL PROTECTED]> > wrote: > > On Fri, Sep 26 17:09:54 CEST 2008, Arnar Birgisson <arnarbi at gmail.com > > > >> > Surely there is a way around this? Some kind of pooling select? If > >> > there is > >> > no work around then I cannot see too much practical use for my thread > >> > library > >> > [except having to avoid learning tasklets for someone who is familiar > >> > with > >> > threads]. As I understand it, due to the GIL the only real practical > >> > use for > >> > threads is if one has blocking function calls (IO-type, etc) > >> > >> The solution would be asynchronous I/O. There have been discussions > >> here occasionally about something generic, like wrapping libevent or > >> similar in an interface that "looks" synchronous but in the background > >> does async I/O and uses channels to make it look synchronous. I figure > >> such a thing would be an excellent component of your thread library. > >> > >> > [Has the GIL restriction been fixed in 3k? As far as I know Jython > does > >> > not > >> > have this limitation...] > >> > >> The GIL has not been removed in Py 3.0, nor will it be removed any > >> time soon. Jython does not have such a thing. > > > > This design solves all these problems, using only C/Unix select (which > you > > pointed out is already used to do time.sleep) in the virtual machine; and > > it runs in only one thread. There is no need to remove the GIL. > > What problems? If you read my message you can clearly see that I > pointed to a _solution_, namely asynchronous I/O. :) What I meant in > my last message is that I don't see how your suggestion improves on > the myriad of async solutions out there already (which are based on > select, poll, epoll, Windows ASIO, etc). > > cheers, > Arnar >
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