Status of Python threading support (GIL removal)?

[Jesse Noller]

On Fri, Jun 19, 2009 at 6:10 PM, Jure Erznožnik<jure.erznoznik at gmail.com> wrote:
> On Jun 19, 11:59 pm, Jesse Noller <jnol... at gmail.com> wrote:
>> On Fri, Jun 19, 2009 at 12:50 PM, OdarR<Olivier.Da... at gmail.com> wrote:
>> > On 19 juin, 16:16, Martin von Loewis <martin.vonloe... at hpi.uni-:
>> >> If you know that your (C) code is thread safe on its own, you can
>> >> release the GIL around long-running algorithms, thus using as many
>> >> CPUs as you have available, in a single process.
>>
>> > what do you mean ?
>>
>> > Cpython can't benefit from multi-core without multiple processes.
>>
>> > Olivier
>>
>> Sorry, you're incorrect. I/O Bound threads do in fact, take advantage
>> of multiple cores.
>
> Incorrect. They take advantage of OS threading support where another
> thread can run while one is blocked for I/O.
> That is not equal to running on multiple cores (though it actually
> does do that, just that cores are all not well utilized - sum(x) <
> 100% of one core).
> You wil get better performance running on single core because of the
> way GIL is implemented in all cases.

No. That's simply incorrect. I (and others) have seen significant
increases in threaded, I/O bound code using multiple cores. It's not
perfect, but it is faster.