-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Brian Harring wrote: > On Tue, Sep 20, 2005 at 06:55:44PM -0500, Paul Varner wrote: > >>On Tue, 2005-09-20 at 18:34 -0500, Brian Harring wrote: >> >>>>Updated patch to add a semaphore to control access to the global >>>>portage.config object. Unless anyone sees any other issues with this >>>>patch, I will be placing it into gentoolkit. >>> >>>Reason for a semaphore over threading.Lock ? >> >>No reason other than I'm used to thinking of them as semaphores instead >>of locks, so semaphore is what I searched for in the Python docs. > > Need to make some chunks of the rewrite thread safe, so I poked a bit; > python -m timeit -n 10000 -r 3 -s 'import threading;s=threading.Lock()' > 's.acquire();s.release()' > around 1us > python -m timeit -n 10000 -r 3 -s 'import threading;s=threading.Semaphore()' > 's.acquire();s.release()' > 20us > > Granted... It's being anal. Just surprised me, and figured I'd poke > to find out if you had a specific reason for using sem over the > simpler (pretty much straight cpython) Lock :) > ~harring
I haven't looked at the code, but I would gather that threading.lock is what most would call a Mutex. Semaphore's generally allow N number of things to do a task ( say have 6 readers on an object, wait on semaphore until all readers release, then write ). Usually a performance if there are more reads vs writes on your objects. Thus the Lock is really a semaphore -> N = 1 which allows the kernel to do some fun optimizing on it's operations. Of course this is all conjecture since none of the __doc__ strings are helpful :P -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iQIVAwUBQzFwF2zglR5RwbyYAQKP5g/+Og6ptvOFp+p4dWXBkKrgPEf/HjDP9Mdb uinNZtytWu4myvDH+nNzz91gFrXQ9vyH6nSv62RZg20jOnAXGEkBZJAnhujteu5i p9/ljSUphVvUHvzgixjGsJtKrbDNh72gwakniO57ZrjolKBxV3EZL87aJmoTd3Ye j9h07mKzla8yOS8rswAS+uSnwWNEHoNbQtcVXnhFw0hhsyasi74Vwm2zoRZs6qgS EHozcNmP0djn5pJPt5LNXhAOrd9myR/pkHQGAUKzvcpgfaRAFgflTJmrPqRAi61F J90+0ZnxSBtplOTifkrOQxAtr///ZEHoe9Hfp5Dg/WInau6FODsEmjZ0j5g+F/6U 1V+50s4EMt4qcoGLPsGPj6HEy+M0SLF/Aie1VZesx/IwWf4jyy2Z6iHknM6WDGbh 1d5c73f9r/2DiV7GdkwpgoTxIAb4i/IcUQSqhB2O4vaJOvLubeJG4UTGPc/AxpEu Vx1Ruvok6xDMOO5W7umYBpcD93ZBBRvdZiRj2uZVIl+AOM9aCejc+sW3KT7J+YLS zlyIkfI29IJdt5QXYweMIX1QiLQSZZQTDKuDmeoqWVm7g48u5f/JLR9wBP+eJluw 4T92h5781vExy7TngGD5qGFMHwP8MMMi4UPB4tp6fLTEqkJeasa79LZrRHTEtNqQ etlk6kngm50= =P0ck -----END PGP SIGNATURE----- -- gentoo-portage-dev@gentoo.org mailing list
