| 1 |
-----BEGIN PGP SIGNED MESSAGE----- |
| 2 |
Hash: SHA1 |
| 3 |
|
| 4 |
Brian Harring wrote: |
| 5 |
> On Tue, Sep 20, 2005 at 06:55:44PM -0500, Paul Varner wrote: |
| 6 |
> |
| 7 |
>>On Tue, 2005-09-20 at 18:34 -0500, Brian Harring wrote: |
| 8 |
>> |
| 9 |
>>>>Updated patch to add a semaphore to control access to the global |
| 10 |
>>>>portage.config object. Unless anyone sees any other issues with this |
| 11 |
>>>>patch, I will be placing it into gentoolkit. |
| 12 |
>>> |
| 13 |
>>>Reason for a semaphore over threading.Lock ? |
| 14 |
>> |
| 15 |
>>No reason other than I'm used to thinking of them as semaphores instead |
| 16 |
>>of locks, so semaphore is what I searched for in the Python docs. |
| 17 |
> |
| 18 |
> Need to make some chunks of the rewrite thread safe, so I poked a bit; |
| 19 |
> python -m timeit -n 10000 -r 3 -s 'import threading;s=threading.Lock()' 's.acquire();s.release()' |
| 20 |
> around 1us |
| 21 |
> python -m timeit -n 10000 -r 3 -s 'import threading;s=threading.Semaphore()' 's.acquire();s.release()' |
| 22 |
> 20us |
| 23 |
> |
| 24 |
> Granted... It's being anal. Just surprised me, and figured I'd poke |
| 25 |
> to find out if you had a specific reason for using sem over the |
| 26 |
> simpler (pretty much straight cpython) Lock :) |
| 27 |
> ~harring |
| 28 |
|
| 29 |
I haven't looked at the code, but I would gather that threading.lock is |
| 30 |
what most would call a Mutex. Semaphore's generally allow N number of |
| 31 |
things to do a task ( say have 6 readers on an object, wait on semaphore |
| 32 |
until all readers release, then write ). Usually a performance if there |
| 33 |
are more reads vs writes on your objects. |
| 34 |
|
| 35 |
Thus the Lock is really a semaphore -> N = 1 which allows the kernel to |
| 36 |
do some fun optimizing on it's operations. |
| 37 |
|
| 38 |
Of course this is all conjecture since none of the __doc__ strings are |
| 39 |
helpful :P |
| 40 |
-----BEGIN PGP SIGNATURE----- |
| 41 |
Version: GnuPG v1.4.1 (GNU/Linux) |
| 42 |
Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org |
| 43 |
|
| 44 |
iQIVAwUBQzFwF2zglR5RwbyYAQKP5g/+Og6ptvOFp+p4dWXBkKrgPEf/HjDP9Mdb |
| 45 |
uinNZtytWu4myvDH+nNzz91gFrXQ9vyH6nSv62RZg20jOnAXGEkBZJAnhujteu5i |
| 46 |
p9/ljSUphVvUHvzgixjGsJtKrbDNh72gwakniO57ZrjolKBxV3EZL87aJmoTd3Ye |
| 47 |
j9h07mKzla8yOS8rswAS+uSnwWNEHoNbQtcVXnhFw0hhsyasi74Vwm2zoRZs6qgS |
| 48 |
EHozcNmP0djn5pJPt5LNXhAOrd9myR/pkHQGAUKzvcpgfaRAFgflTJmrPqRAi61F |
| 49 |
J90+0ZnxSBtplOTifkrOQxAtr///ZEHoe9Hfp5Dg/WInau6FODsEmjZ0j5g+F/6U |
| 50 |
1V+50s4EMt4qcoGLPsGPj6HEy+M0SLF/Aie1VZesx/IwWf4jyy2Z6iHknM6WDGbh |
| 51 |
1d5c73f9r/2DiV7GdkwpgoTxIAb4i/IcUQSqhB2O4vaJOvLubeJG4UTGPc/AxpEu |
| 52 |
Vx1Ruvok6xDMOO5W7umYBpcD93ZBBRvdZiRj2uZVIl+AOM9aCejc+sW3KT7J+YLS |
| 53 |
zlyIkfI29IJdt5QXYweMIX1QiLQSZZQTDKuDmeoqWVm7g48u5f/JLR9wBP+eJluw |
| 54 |
4T92h5781vExy7TngGD5qGFMHwP8MMMi4UPB4tp6fLTEqkJeasa79LZrRHTEtNqQ |
| 55 |
etlk6kngm50= |
| 56 |
=P0ck |
| 57 |
-----END PGP SIGNATURE----- |
| 58 |
-- |
| 59 |
gentoo-portage-dev@g.o mailing list |
Archives