On 16 August 2011 11:39, mark florisson <markflorisso...@gmail.com> wrote: > On 15 August 2011 23:33, Dag Sverre Seljebotn > <d.s.seljeb...@astro.uio.no> wrote: >> Would it be horribly expensive to generate a better runtime error, or even >> initialize the gil on demand? If the gil is not initialized, get the thread >> ID of the thread calling the callback and check against the thread entering >> at module initialization time...I don't know whether pythread.h has a cheap >> way of achieving this. > > I'm not sure how expensive PyThread_get_thread_ident(), for pthreads > it calls pthread_self() is. So it's either such a call for every with > gil, or initializing the GIL... I'll try to do some tests later today > and report back. > >> -- >> Sent from my Android phone with K-9 Mail. Please excuse my brevity. >> >> Stefan Behnel <stefan...@behnel.de> wrote: >>> >>> Dag Sverre Seljebotn, 15.08.2011 11:54: > On 08/15/2011 11:42 AM, mark >>> florisson wrote: >> @Cython-dev: Do we merely want to update the docs, or do >>> we want to >> initialize the GIL for either case, or only for the with gil >>> >> functions? I'm not entirely sure what the overhead is for >> >>> single-threaded code, but I'd say we need to initialize it for both >> >>> cases. > > I'm not sure if I like magic related to having used "with gil" on >>> a > function signature -- it's a bit too magic and obscure. I don't really >>> like this either. The reason why the GIL is not being initialised by default >>> is that it has a runtime impact. Just because code is aware of threading >>> does not mean it is going to be used with threads. Especially library code >>> (which is a common place for using Cython) shouldn't impose such an impact >>> on the rest of the runtime. Stefan >>> ________________________________ >>> cython-devel mailing list cython-devel@python.org >>> http://mail.python.org/mailman/listinfo/cython-devel >> >> _______________________________________________ >> cython-devel mailing list >> cython-devel@python.org >> http://mail.python.org/mailman/listinfo/cython-devel >> >> >
Ok, I attached a little script that does some computation (naive_convolve from the docs). This is the result: ➤ python convolve.py 5.61997413635 ➤ python convolve.py --with-gil 5.96432781219 So that mean you get approximately a 6% slowdown with the GIL initialized. The alternative is that we do a check for every with gil in Cython code for the thread ident + PyEval_ThreadsInitialized() (haven't tested how much that will slow down with gil blocks, but I assume the difference would be nearly negligible). So I suppose that check + abort would be the way to go? _______________________________________________ cython-devel mailing list cython-devel@python.org http://mail.python.org/mailman/listinfo/cython-devel
