Re: Linux 2.5 / 2.6 TODO (preliminary)

From: Mike Porter (mike@UDel.Edu)
Date: Fri Jun 02 2000 - 09:55:26 EST

On Fri, 2 Jun 2000, Markus Pfeiffer wrote:

> Sasi Peter wrote:
> >
> > On Thu, 1 Jun 2000, Gregory Maxwell wrote:
> >
> > > About the only think I can think of is turning off CPUs on a SMP
> > > laptop for powermanagement.. :P So unless someone from transmeta speaks
> > > up about a quad cpu laptop this just sounds like a feature looking for a
> > > need. (i.e. worthless cruft)
> >
> > No!
> >
> > Think of a fan failing on one of the CPUs, in the middle of a veri
> > important computing task. If you can umount that CPU, it will not burn and
> > crash from overheat, and your process can also finish off.
> >
> > Thinking of HA, when desinging the future of linux is a must...
> ehemmm,
> I think the CPU will burn even if it is umounted ... and a fan failing
> ...
> Good, if you take a very cheap one, but if one does high performance
> computing
> one doesn´t use crappy equipment, and even if a failure of expensive
> equipment
> is possible, I think the scheduler changes are too expensive ( of the
> speeds point of
> view ... ). People at Be seem to be playing people...

Mainframe OSes (IBM MVS, now OS/390) can 'vary' off CPUs. It's not
something I've done very often, but it can be handy. We had a CPU
fail one time. The address space (process) running on that
processor failed, but the operating system kept running, along with
the 500 other address spaces. Being able to configure CPUs on and
offline is something you want if you are running a high
availability system. Detecting failed CPUs and automatically
configuring them offline is also useful, but does a typical
consumer PC with Pentium IIIs have any way to communicate the
notion of a failed processor to the operating system? Probably
not. Is IBM releasing enough details about their hardware to be
able to implement failed CPU detection? I'll bet not...


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