Mailinglist Archive: opensuse (2876 mails)

["Greg Freemyer" <greg.freemyer@xxxxxxxxx>]

On 5/23/07, Doug McGarrett <dmcgarrett@xxxxxxxxxxxxx> wrote:
> On Wednesday 23 May 2007 20:44, Mike McMullin wrote:
> > On Wed, 2007-05-23 at 12:42 -0400, George Stoianov wrote:
> > > I think you should be using the smp kernel. What kind of a machine do
> > > you have? Anything in the system logs?
> >
> >   IIRC for 10.2 the kernel default is the smp kernel.
>
>
> What happens if you use this kernel on a machine that has only
> one processor, or is the install smart enough to figure all this
> out?
>
> --doug

The kernel developers got real smart in the last year or so.

The main difference between UP and SMP is the locking mechanisms.  So
in a SMP it makes sense to have a spin-lock.  (spin-lock == an
infinite loop waiting for a variable to change).  In a UP a spin-lock
might cause a lockup (Definitely will if interrupts are disabled).

The kernel now has self-modifying code.  During boot up, the low level
locking routines start out in SMP configuration, but if a UP is found
the machine code in those routines is replaced with their UP
equivalents (often no-ops).

I assume they have only done this for the most common CPU types (ie.
instruction sets).

See http://lwn.net/Articles/164121/ for more details ;(and accuracy)..

Greg
--
Greg Freemyer
The Norcross Group
Forensics for the 21st Century
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