On Aug 1, 2:28 pm, John Krukoff <[EMAIL PROTECTED]> wrote: > On Thu, 2008-07-31 at 18:27 -0700, Craig Allen wrote: > > I have followed the GIL debate in python for some time. I don't want > > to get into the regular debate about if it should be gotten rid of > > (though I am curious about the status of that for Python 3)... > > personally I think I can do multi-threaded programming well, but I > > also see the benefits of a multiprocess approach. I'm not so > > egotistical that I don't realize perhaps my mt programming has not > > been "right" (though it worked and was debuggable) or more likely that > > doing it right I have avoided even trying some things people want mt > > programming to do... i.e. to do mt programming right you start to use > > queues a lot, inter-thread asynchronous, non-blocking, communication, > > which is essentially the multi-process approach, using IPC (except > > that the threads can see the same memory when, in your special case, > > you know that's ok. Given something like a reader-writer lock, this > > can have benefits... but again, whatever. > > > My question is that given this problem, years ago before I started > > writing in python I wrote some short programs in python which could, > > in fact, busy both my CPUs. In retrospect I assume I did not have > > code in my run function that causes a GIL lock... so I have done this > > again. > > > I start two threads... I use gkrellm to watch my processors (dual > > processor machine). If I merely print a number... both CPUS are > > getting 90% simultaneous loads. If I increment a counter and print it > > too, the same, and if I create a small list and sort it, the same. I > > did not expect this... I expected to see one processor pegged at > > around 100%, which should sometimes switch to the other processor. > > Granted, the same program in C/C++ would peg both processors at > > 100%... but given that the overhead in the interpreter cannot explain > > the extra usage, I assume the code in my thread's run functions is > > actually executing non-serially. > > > I assume this is because what I am doing does not require the GIL to > > be locked for a significant part of the time my code is running... > > what code could I put in my run function to see the behavior I > > expected? What code could I put there to take advantage of the > > possibility that really the GIL is not locked enough to cause actual > > serialization of the threads... anyone care to explain? > > -- > >http://mail.python.org/mailman/listinfo/python-list > > It's worth mentioning that the most common place for the python > interpreter to release the GIL is during I/O, which printing a number to > the screen certainly counts as. You might try again with a set of loops > that only increment, and don't print, and you may more obviously see the > GIL in action. > -- > John Krukoff <[EMAIL PROTECTED]> > Land Title Guarantee Company
thanks, good idea, I think I'll try that. -- http://mail.python.org/mailman/listinfo/python-list
