On Wednesday 22 May 2002 6:27 pm, Alfred Perlstein wrote:
> * Dorr H. Clark <dclark@applmath.scu.edu> [020522 09:58] wrote:
> > I don't have access to a fancy Xeon, I just have
> > a PIII dual-banger, so I'm relying on the list traffic.
> > To summarize the past two months:
> >
> > On Thu, 14 Mar 2002, John Baldwin wrote:
> >
> > On Thu, 14 Mar 2002, Terry Lambert wrote:
> >
> > On Tue, 23 Apr 2002, FiberOps wrote:
> >
> > On Tue, 23 Apr 2002, John Baldwin wrote:
> >
> > On 23-Apr-2002 FiberOps wrote:
> >
> > This final message was not followed up except by me,
> > although someone else informed me that while the CPUs
> > launch, FreeBSD can't run processes on them.
> >
> > So I thought I'd try to stir up an answer to the original question:
> >
> > For the latest Xeon motherboards, does FreeBSD 4.x stable
> > support hyperthreading? If not, does the current TOT?
> > If not, why not? Is gcc an issue or not? If gcc is an issue,
> > would this be an obstacle for all gcc-based OSes,
> > not just FreeBSD, most prominently among these Linux?
> >
> > Clear answers gratefully appreciated,
>
> I'm glad you chose to take the word of a couple of people
> that have never used a hyperthreading board above what I've
> already told you.
>
> Here's what I know:
> The additional CPUs probe.
>
> A benchmarking utility reports equivelant performance to a 4 way
> machine.
One thing we don't do which we could use to squeeze extra performance is to
adjust the allocation of cpus to procs. When one hyperthread is idle on a cpu
while the other one is running, the running hyperthread is faster since it
can use more functional units. When we schedule a new thread, we should
prefer cpus which are totally idle (i.e. both hyperthreads are idle) and only
schedule two hyperthreads on a single cpu when there is no totally idle cpu
left.
--
Doug Rabson Mail: dfr@nlsystems.com
Phone: +44 20 8348 6160
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