On 10/10/05, Greg Ewing <[EMAIL PROTECTED]> wrote: > I'm wondering whether Python threads should be > non-preemptive by default. Preemptive threading is > massive overkill for many applications. You don't > need it, for example, if you just want to use threads > to structure your program, overlap processing with I/O, > etc.
I recall using a non-preemptive system in the past; in Amoeba, to be precise. Initially it worked great. But as we added more powerful APIs to the library, we started to run into bugs that were just as if you had preemptive scheduling: it wouldn't always be predictable whether a call into the library would need to do I/O or not (it might use some sort of cache) so it would sometimes allow other threads to run and sometimes not. Or a change to the library would change this behavior (making a call that didn't use to block into sometimes-blocking). Given the tendency of Python developers to build layers of abstractions I don't think it will help much. > Preemptive threading would still be there as an option > to turn on when you really need it. > > Or perhaps there could be a priority system, with a > thread only able to be preempted by a thread of higher > priority. If you ignore priorities, all your threads > default to the same priority, so there's no preemption. > If you want a thread that can preempt others, you give > it a higher priority. If you ask me, priorities are worse than the problem they are trying to solve. -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
