[Python-ideas] multiprocessing and physical CPU cores count

[Giampaolo Rodola']

On Thu, Sep 12, 2013 at 9:32 PM, Antoine Pitrou <solipsis at pitrou.net> wrote:

> On Thu, 12 Sep 2013 21:26:07 +0200
> "Giampaolo Rodola'" <g.rodola at gmail.com>
> wrote:
> > On Thu, Sep 12, 2013 at 9:10 PM, Antoine Pitrou <solipsis at pitrou.net>
> wrote:
> >
> > > On Thu, 12 Sep 2013 20:59:46 +0200
> > > "Giampaolo Rodola'" <g.rodola at gmail.com>
> > > wrote:
> > > > This is a follow up of a feature request which recently appeared on
> > > psutil
> > > > bug tracker:
> > > > https://code.google.com/p/psutil/issues/detail?id=427
> > > >
> > > > I don't know whether the proposal makes sense for psutil per-se but
> it
> > > > certainly made me think about multiprocessing.cpu_count() and the
> fact
> > > that
> > > > it currently returns the number of virtual CPUs (physical + logical).
> > > >
> > > > Given that multiple processes cannot take any advantage of hyper
> > > threading
> > > > technology
> > >
> > > Of course they can.  The CPU doesn't distinguish between different
> > > kinds of "threads", they can either belong to the same process or to
> > > different ones.
> >
> >
> > Of course you're right, I'm sorry. I should have phrased my statement
> more
> > carefully before sending the email.
> > Then the question is whether having physical CPU cores count can be
> useful.
>
> I suppose it doesn't hurt :-) I don't think it belongs specifically in
> multiprocessing, though. Perhaps in the platform module?
>

I'd be +0.5 for multiprocessing because:

- cpu_count() is already there
- physical_cpu_count() will likely be used by multiprocessing users only

...but my main concern was first figuring out whether it might actually
make sense to distinguish between virtual and physical CPUs in a real world
app.


> (unless you want to contribute psutil to the stdlib?)


That's something I'd be happy to do if there's general approval but I guess
that's for another thread.

--- Giampaolo
https://code.google.com/p/pyftpdlib/
https://code.google.com/p/psutil/
https://code.google.com/p/pysendfile/
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