[BTW, please follow standard Usenet convention and attribute the quotes; I've added them back in for you]
In article <[EMAIL PROTECTED]>, Carl J. Van Arsdall <[EMAIL PROTECTED]> wrote: >Aahz: >>Carl Van Arsdall: >>> >>> 1. Who schedules which threads run and when? Is this something left up >>> to the operating system or does python provide a mechanism for this? >> >> Strictly OS -- Python provides no control. > >I did some research yesterday, and I'd like some clarification. So the >OS handles which thread runs and when, however if one of the python >processes currently holds the global interpreter lock, when the OS >switches to a python thread that does not have this lock, this thread >will do nothing. Does this sound right? Ultimately python does >control what thread runs by controlling the global interpreter lock >although its the underlying OS that handles all the context switching >etc. No. Python simply uses a standard OS thread lock. When a Python thread gives up the GIL, the OS decides which thread acquires the lock -- it could even be the same thread that released the lock. >Because of this global interpreter lock does this mean its impossible to >get speed up with threading on multiple processor systems? I would >think so because only one python thread can execute at any one time. Is >there a way to get around this? This isn't something I need to do, I'm >just curious at this point. You either need to run multiple processes or run code that mostly calls into C libraries that release the GIL. For example, a threaded spider scales nicely on SMP. -- Aahz ([EMAIL PROTECTED]) <*> http://www.pythoncraft.com/ "Don't listen to schmucks on USENET when making legal decisions. Hire yourself a competent schmuck." --USENET schmuck (aka Robert Kern) -- http://mail.python.org/mailman/listinfo/python-list
