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Date: Thu, 4 Oct 2001 13:00:51 -0500
From: Alfred Perlstein <bright@mu.org>
To: Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>
Cc: smp@freebsd.org
Subject: Re: How to distinguish the SMP kernel and the UP kernel
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References: <200110030310.MAA13836@zodiac.mech.utsunomiya-u.ac.jp> <3BBB6757.9A668E99@mindspring.com> <200110041211.VAA24646@zodiac.mech.utsunomiya-u.ac.jp>
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* Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp> [011004 07:01] wrote:
> 
> # moved to smp ML, to which this thread should have been posted
> # in the first place :-)
> 
> >Kazutaka YOKOTA wrote:
> >> 
> >> Is there any way for the loadable module to detect if
> >> the kernel is configured for SMP or UP?
> >
> >There is a global variable, "ncpu".  Its name may have changed
> >recently, so you will want to look at the SYSCTL() stuff in
> >/sys/i386/i386 to be sure.
> >
> >-- Terry
> 
> The sysctl variable hw.ncpu returns 1 in the UP kernel,
> and returns the number of active CPUs in the SMP kernel.
> 
> When hw.ncpu == 1, it doesn't necessarily signifies the kernel
> is configured for UP. Because it is perfectly permissible
> to run the SMP kernel on the multi-CPU motherboard with only one
> CPU installed...
> 
> Am I wrong?

I'm quite sure you're right.  It would probably make sense
to have a sysctl that says weather or not MP is configured or
not.

-- 
-Alfred Perlstein [alfred@freebsd.org]
'Instead of asking why a piece of software is using "1970s technology,"
start asking why software is ignoring 30 years of accumulated wisdom.'

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