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Mailing List Archive: Gentoo: PPC-User

Kernel Preemption

 

 

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michael_six at users

Aug 3, 2005, 5:15 AM

Post #1 of 3 (665 views)
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Kernel Preemption

<snipped from another thread>

On Mon August 1 2005 07:26 am, Mike S wrote:

>
>
> >
> > No, just broken.


> Unless you enable SMP in conjunction with it (yes, even if you _only have one
> CPU_!).


I opted to use an upstream kernel. Is this also broken here, or just in
the gentoo kernel? And I do have SMP enabled. Basically whatever
speed-ups I can get I am trying to use.

--Mike S
--
gentoo-ppc-user [at] gentoo mailing list


zeekec at mad

Aug 4, 2005, 6:56 AM

Post #2 of 3 (622 views)
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Re: Kernel Preemption [In reply to]

On Wed August 3 2005 08:15 am, Mike S wrote:
> <snipped from another thread>
>
> On Mon August 1 2005 07:26 am, Mike S wrote:
> >> > Is kernel preemption a bad thing?
> >> >
> >> > --Mike S
> > >
> > > No, just broken.
> >
> > Unless you enable SMP in conjunction with it (yes, even if you _only have
> > one CPU_!).
>
> I opted to use an upstream kernel. Is this also broken here, or just in
> the gentoo kernel? And I do have SMP enabled. Basically whatever
> speed-ups I can get I am trying to use.
>
> --Mike S

As I understand, it preemption is not exactly a speedup. It is supposed to
improve the responsiveness of the kernel to user input. The kernel can
switch contexts in more places inside the kernel in response to other inputs.
This is great for desktops, but probably not for servers/number crunchers.

I have no idea if it's fixed or not. Try disabling SMP and enabling
preemption followed by an emerge of something large (openoffice, kde, you
pick). If it succeeds, maybe it's fixed. If not, then it's still broken.

Erik

P.S. I'm no expert on the kernel (I'm a laser physicist.), so you might be
better off Googling for an answer.
--
*******************************************
Dr. Erik Zeek
Postdoctoral Research Associate
Department of Physics and Astronomy
The University of Georgia
Athens, GA 30602-2451

Tel: 706-542-7293
Email: mailto:zeekec [at] mad
Html: http://www.physast.uga.edu/~zeekec
*******************************************
Against stupidity the very gods
Themselves contend in vain.
- Johann Christoph Friedrich von Schiller (1801)
*******************************************


dholm at gentoo

Aug 4, 2005, 7:04 AM

Post #3 of 3 (624 views)
Permalink
Re: Kernel Preemption [In reply to]

On Thursday 04 August 2005 15:56, Erik Zeek wrote:

[snip]

> As I understand, it preemption is not exactly a speedup. It is supposed to
> improve the responsiveness of the kernel to user input. The kernel can
> switch contexts in more places inside the kernel in response to other
> inputs. This is great for desktops, but probably not for servers/number
> crunchers.

That pretty much sums it up.

> I have no idea if it's fixed or not. Try disabling SMP and enabling
> preemption followed by an emerge of something large (openoffice, kde, you
> pick). If it succeeds, maybe it's fixed. If not, then it's still broken.

No, it hasn't been fixedyet. :(
Please don't attempt to disable SMP with preemption still enabled.

//David

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