Re: Hyperthreading

From: Marc Dietrich (
Date: Thu Aug 22 2002 - 09:36:54 EST

Am Donnerstag, 22. August 2002 :06 schrieben Sie:
> 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)?

I don't think so. Original kernel gives me 2 penguins and cpuinfo shows 2
cpu's. Kernel is 2.4.19 with xfs patches and there is no "noht" option. I
attached a dmesg file of this one. Btw, setting the processor also sets some
other options (CMPXCHG, TCS, PGE, ...).

> 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".

Give it a try. A dual Xeon won't take to much time to compile a new kernel ;)



Marc Dietrich

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