[Issue 4462] core.cpuid wrong on Intel machines w/ multiple physical CPUs

d-bugmail at puremagic.com d-bugmail at puremagic.com
Sun Feb 27 14:02:43 PST 2011


http://d.puremagic.com/issues/show_bug.cgi?id=4462



--- Comment #3 from Don <clugdbug at yahoo.com.au> 2011-02-27 13:59:51 PST ---
To clarify: core.cpuid does NOT provide the number of CPUs in the system.
Hence, it does not give the total number of available cores.

core.cpuid gives the number of cores in each CPU, and the number of
hyperthreads in each core. This means that it has sufficient information to do
cache blocking correctly.

The total number of physical CPUs is required only when distributing work
between cores (you never need to know it when scheduling within a core).
Determining this is OS-dependent, and is actually pretty useless unless you
also have some way of controlling the processor affinity, as well. Although
this is stuff we will definitely need, it's quite a different situation from
bugs in the existing code.

Are there any cases where the reported values are actually wrong? Or is this a
feature request for the number of physical CPUs?

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