I found that but I'm looking at the /gumstix-buildroot/build_arm_nofpu/linux- 2.6.18gum/kernel/Kconfig.preempt
where it says:
choice
    prompt "Preemption Model"
    default PREEMPT_NONE

config PREEMPT_NONE
    bool "No Forced Preemption (Server)"
    help
      This is the traditional Linux preemption model, geared towards
      throughput. It will still provide good latencies most of the
      time, but there are no guarantees and occasional longer delays
      are possible.

      Select this option if you are building a kernel for a server or
      scientific/computation system, or if you want to maximize the
      raw processing power of the kernel, irrespective of scheduling
      latencies.

config PREEMPT_VOLUNTARY
    bool "Voluntary Kernel Preemption (Desktop)"
    help
      This option reduces the latency of the kernel by adding more
      "explicit preemption points" to the kernel code. These new
      preemption points have been selected to reduce the maximum
      latency of rescheduling, providing faster application reactions,
      at the cost of slighly lower throughput.

      This allows reaction to interactive events by allowing a
      low priority process to voluntarily preempt itself even if it
      is in kernel mode executing a system call. This allows
      applications to run more 'smoothly' even when the system is
      under load.

      Select this if you are building a kernel for a desktop system.

config PREEMPT
    bool "Preemptible Kernel (Low-Latency Desktop)"
    help
      This option reduces the latency of the kernel by making
      all kernel code (that is not executing in a critical section)
      preemptible.  This allows reaction to interactive events by
      permitting a low priority process to be preempted involuntarily
      even if it is in kernel mode executing a system call and would
      otherwise not be about to reach a natural preemption point.
      This allows applications to run more 'smoothly' even when the
      system is under load, at the cost of slighly lower throughput
      and a slight runtime overhead to kernel code.

      Select this if you are building a kernel for a desktop or
      embedded system with latency requirements in the milliseconds
      range.
 
I can't find where that choice lies. I've selected the Preemptible Kernel (EXPERIMENTAL) from the Kernel Features
but as you can see the default preemption model is PREEMPT_NONE. I have a PREEMPT kernel on the gumstix right now but how do I know which preemption model it's running under?
Thanks for the quick responses!

On 1/18/07, Craig Hughes <craig@gumstix.com> wrote:
Look in the kernel menuconfig under "Kernel Features".  Top item.

C

On Jan 18, 2007, at 4:05 PM, Jesse Welling wrote:

> Does any one know where I can find more documentation on using the
> Preemption option for the 2.6.18 kernel?
> I found the RT patch wiki but I just wanted to see what is
> available with out it. I realize that the RT patch is being merged
> with the main line kernel and I found the /gumstix-buildroot/
> build_arm_nofpu/linux- 2.6.18gum/kernel/Kconfig.preempt which seems
> to be related to enabling the Preeempt when you rebuild the Kernel
> but I don't see where you select these options.
> Can any one shed any light or am I barking up the wrong tree?
>
>
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