On Thu, Sep 12, 2013 at 9:27 PM, Richard Oudkerk <shibturn@gmail.com> wrote:
On 12/09/2013 7:59pm, Giampaolo Rodola' wrote:
Given that multiple processes cannot take any advantage of hyper
threading technology then maybe it makes sense for multiprocessing to
expose a physical_cpu_count() function in order to preemptively figure
out how many processes to spawn.

Do you have a reference?  Wikipedia may not be reliable, but it seems to think otherwise:

Hyper-threading works by duplicating certain sections of the processor—
those that store the architectural state— but not duplicating the main
execution resources. This allows a hyper-threading processor to appear
as the usual "physical" processor and an extra "logical" processor to
the host operating system (HTT-unaware operating systems see two
"physical" processors), allowing the operating system to schedule two
threads or processes simultaneously and appropriately.
           ^^^^^^^^^

No, I was wrong. 
Please ignore that statement.
I got confused by the name "hyper-threading" and erroneously thought it only affected threads. =)