Re: CFD: XMLification of NOTES
From: Bruce Evans (bde_at_zeta.org.au)
Date: 04/01/04
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Date: Thu, 1 Apr 2004 15:11:38 +1000 (EST) To: John Baldwin <john@baldwin.cx>
On Wed, 31 Mar 2004, John Baldwin wrote:
> On Tuesday 30 March 2004 06:54 pm, Dag-Erling Smørgrav wrote:
> > CPU_I386 should not conflict with SMP, but a kernel build with both
> > will be very slow.
>
> No, it does conflict. There's no cmpxchg on i386 and no one has had the
> desire or time to emulate one for 386 machines. Doing so would be a waste in
> my opinion as well.
des only claimed that it "should not".
Emulating cmpxchg might make a kernel built with both slow, but the
current CPU_I386 only adds a tiny amount of slowness. It just doesn't
work on multi-CPU systems if multiple CPUs are actually used.
Does it actually conflict in practice (except for the forced #error)
if the hardware is UP? jhb's APIC changes made configuring with SMP
not require APIC, so SMP kernels work on UP systems. Configuring with
I386_CPU shouldn't affect this, but it does because of the forced #error
at compile time.
Bruce
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