Re: Hyperthreading

From: Hugh Dickins (
Date: Thu Aug 22 2002 - 09:06:11 EST

On Thu, 22 Aug 2002, Marc Dietrich wrote:
> On Wed, 21 Aug 2002, Hugh Dickins wrote:
> >
> > You do need CONFIG_SMP and a processor capable of HyperThreading,
> > i.e. Pentium 4 XEON; but CONFIG_MPENTIUM4 is not necessary for HT,
> > just appropriate to that processor in other ways.
> I used KNOPPIX on a 2 way Dell WS 530 (Xeon 2.0 GHz). This distribution has
> CONFIG_M386 set (as most others also?) and HT was not enabled. I compiled the
> kernel myself (same config as KNOPPIX but with CONFIG_MPENTIUM4) and HT gets
> enabled. So is _does_ matter for which processor the kernel is optimized.

I'm surprised - perhaps the Knoppix distribution did not have SMP enabled
itself, but installed a config with CONFIG_SMP? Or you built more recent
kernel sources (2.4.19 defaults to HT on) than the Knoppix distribution
(vanilla 2.4.18 defaults to HT off)?

It would be awkward for me to try CONFIG_M386 on our P4 Xeon, but I did
just try building a CONFIG_M586 CONFIG_SMP kernel for it, which behaved
as I expected: /proc/cpuinfo showed 4 cpus, but only 2 cpus when booted
with "noht".


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