Re: [linuxdc-dev][PATCH] Preemptible Kernel for SH (and thus dreamcast)

[Jason K. <ja...@ke...>]

I have the pre-empt patch installe don my base machine here, and have never 
really noticed much of a difference in response time. Would this make more of 
an effect in the dreamcast for some reason?

On December 2, 2001 9:53 pm, Robert Love wrote:
> I also want to mention that we have a version of the preemptible kernel
> for the SH arch now, and it seems to run lovely on the Dreamcast.
>
> It is available at:
> 	http://www.kernel.org/pub/linux/kernel/people/rml/sh/preempt-kernel-sh-2.4
>.16-1.patch
>
> You will also need the base preempt-kernel patch at:
> 	http://www.kernel.org/pub/linux/kernel/people/rml/preempt-kernel/v2.4/pree
>mpt-kernel-rml-2.4.16-1.patch
>
> And a recent SH tree. The "linux" module in CVS at
> http://sf.net/projects/linuxsh was recently updated to 2.4.16.
> Alternatively, here is a patch to bring 2.4.16 in sync with the SH tree:
> 	http://www.kernel.org/pub/linux/kernel/people/rml/sh/sh-update-rml-2.4.16-
>1.patch
>
> There is a bit of information about the preemptible kernel at
> http://tech9.net/rml/linux as well as LWN, slashdot, etc.  Basically,
> the current linux kernel does not allow processes to be preempted when
> operating inside the kernel.  I.e., kernel calls run until completion --
> this implies that even if task A needs to run, if task B is running and
> in the kernel, task A won't be scheduled until task A is done.  The
> degradation this causes to latency and system response is clear.
> Further, however, since with the preempt-kernel patch I/O-bound tasks
> are scheduled as-soon-as I/O is available, throughput tends to increase,
> too.  We are aiming at inclusion in 2.5.
>
> Its pretty neat.  If nothing else, tell your friends you have a fully
> preemptible Dreamcast.  Or something.
>
> Comments and feedback is welcome,
>
> 	Robert Love
>
>
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