only one logical CPU used in Xeon
olli at lurza.secnetix.de
Tue Mar 10 14:31:39 PDT 2009
Julian Elischer wrote:
> Robert Heron wrote:
> > Hyperthreading is enabled in BIOS, but the variable:
> > machdep.hyperthreading_allowed
> > is '0' by default in FreeBSD 6.2R :(((
> > I just changed it now to '1' and all cores in all CPUs started to work :)))
> > Very simple change and so much power more :)
> well certainly more power used..
> It would be a good idea to do benchmarks on your workload
> to check if it actually helps. This is is because
> Hyperthreading on some cpu models actually reduces throughput
> on some workloads because it thrashes the shared cache more.
No need for benchmarks here, because Robert's processors
don't do hyperthreading at all. FreeBSD 6.2 recognized
the *cores* as logical HT processors, so he needs to
set hyperthreading_allowed in order to enable the cores.
Of course, the better solution is to update to a more
recent release, such as 6.4 or even 7.1. His 6.2 is
more than 2 years old and contains lots of known bugs,
of which the wrong recognition of cores is a relatively
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