Barney Cordoba barney_cordoba at yahoo.com
Thu May 7 09:26:51 UTC 2009

--- On Wed, 5/6/09, pluknet <pluknet at gmail.com> wrote:

> From: pluknet <pluknet at gmail.com>
> Subject: Re: Hypertherading
> To: "Barney Cordoba" <barney_cordoba at yahoo.com>
> Cc: "Current at freebsd.org" <Current at freebsd.org>
> Date: Wednesday, May 6, 2009, 10:55 PM
> 2009/5/7 Barney Cordoba <barney_cordoba at yahoo.com>:
> >
> > I just got a shiny new nehalem box and it comes up
> with 16 processors with dual quads installed. Is there any
> benefit or should hyperthreading be disabled?
> >
> Hi. There is a measurable win if hyperthreading is enabled
> [1].
> You can switch it off via machdep.hyperthreading_enabled
> loader tunable.
> [1]
> http://lists.freebsd.org/pipermail/freebsd-stable/2009-January/047460.html

I wouldn't call varying the number of jobs a very good test
of hyperthreading. I'd want to see the exact same test with
hyperthreading enabled and disabled. Its pretty naive
to assume that running 16 jobs causes them to all be run on 
a different cpu.



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