On Sep 20, 2005, at 5:43 PM, Guido van Rossum wrote: > On 9/20/05, John J Lee <[EMAIL PROTECTED]> wrote: > >> threading is not the only, nor the best, concurrency model. >> But maybe these chips designed with threading in mind blow that >> argument >> out of the water. I don't know enough to know whether that's true or >> not... >> > > I don't know that any chips are designed with threading in mind. Fast > threading benefits from fast context switches which benefits from > small register sets. I believe the trend is towards ever large > register sets. Also, multiple processors with shared memory don't > scall all that well; multiple processors with explicit IPC channels > scale much better. All arguments for multi-processing and against > multi-threading.
Well, in many operating systems, there isn't a whole lot of difference between threads and processes (both are kernel threads). When using threads, you can typically still use IPC, so you could scale similarly. I think the biggest argument for threading is simply that lots of existing C/C++ code wants to use threads. What we have now works OK, but you can't reliably use Python in a real-time thread (e.g. a CoreAudio callback) or (reliably) in a signal handler because it might block too long because of something else going on. Of course, a lot of other design decisions in Python would prevent you from using it in that context too, so GIL-free threading wouldn't be a panacea. Personally my biggest issue with the way the CPython VM works is that you can't reliably do multiple interpreters in a single process. If that worked well, you could start an independent interpreter per thread and with a per-interpreter GIL you'd have pretty much everything you needed... but this would horribly break the C API and may be a performance hit. My use case for this isn't so much about threads, but plug-ins. Writing multiple Python-based plug-ins for an application is always a mess, because they share too much (sys.modules, sys.path, etc.). PyObjC would benefit greatly from this feature, because you can write Python-based plug-ins for any Cocoa app that supports plug-ins, even if they're otherwise unaware of Python's existence. There are workarounds, of course, with import hooks and similar hacks. I think that mod_python would also benefit from this, and probably other such systems. -bob _______________________________________________ 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
